An isotopic and modelling study of flow paths and storage in Quaternary calcarenite, SW Australia: implications for speleothem paleoclimate records

NASA Astrophysics Data System (ADS)

Treble, Pauline C.; Bradley, Chris; Wood, Anne; Baker, Andy; Jex, Catherine N.; Fairchild, Ian J.; Gagan, Michael K.; Cowley, Joan; Azcurra, Cecilia

2013-03-01

We investigated the distinctive shallow sub-surface hydrology of the southwest Western Australia (SWWA) dune calcarenite using observed rainfall and rainfall δ18O; soil moisture, cave drip rate and dripwater δ18O over a six-year period: August 2005-March 2012. A lumped parameter hydrological model is developed to describe water fluxes and drip δ18O. Comparison of observed data and model output allow us to assess the critical non-climatic karst hydrological processes that modify the precipitation δ18O signal and discuss the implications for speleothem paleoclimate records from this cave and those with a similar karst setting. Our findings include evidence of multiple reservoirs, characterised by distinct δ18O values and recharge responses ('low' and 'high' flow sites). Dripwaters exhibit δ18O variations in wet versus dry years at low-flow sites receiving diffuse seepage from the epikarst with an attenuated isotopic composition that approximates mean rainfall. Recharge from high-magnitude rain events is stored in a secondary reservoir which is associated with high-flow dripwater that is 1‰ lower than our monitored low-flow sites (δ18O). One drip site is characterised by mixed-flow behaviour and exhibits a non-linear threshold response after the cessation of drainage from a secondary reservoir following a record dry year (2006). Additionally, our results yield a better understanding of the vadose zone hydrology and dripwater characteristics in Quaternary age dune limestones. We show that flow to our monitored sites is dominated by diffuse flow with inferred transit times of less than one year. Diffuse flow appears to follow vertical preferential paths through the limestone reflecting differences in permeability and deep recharge into the host rock.

Mathematical model of sediment and solute transport along slope land in different rainfall pattern conditions

PubMed Central

Tao, Wanghai; Wu, Junhu; Wang, Quanjiu

2017-01-01

Rainfall erosion is a major cause of inducing soil degradation, and rainfall patterns have a significant influence on the process of sediment yield and nutrient loss. The mathematical models developed in this study were used to simulate the sediment and nutrient loss in surface runoff. Four rainfall patterns, each with a different rainfall intensity variation, were applied during the simulated rainfall experiments. These patterns were designated as: uniform-type, increasing-type, increasing- decreasing -type and decreasing-type. The results revealed that changes in the rainfall intensity can have an appreciable impact on the process of runoff generation, but only a slight effect on the total amount of runoff generated. Variations in the rainfall intensity in a rainfall event not only had a significant effect on the process of sediment yield and nutrient loss, but also the total amount of sediment and nutrient produced, and early high rainfall intensity may lead to the most severe erosion and nutrient loss. In this study, the calculated data concur with the measured values. The model can be used to predict the process of surface runoff, sediment transport and nutrient loss associated with different rainfall patterns. PMID:28272431

Assessing modern climatic controls on southern Sierra Nevada precipitation and speleothem δ18O

NASA Astrophysics Data System (ADS)

McCabe-Glynn, S. E.; Johnson, K. R.; Berkelhammer, M. B.

2012-12-01

Precipitation in the southwestern United States (SW US) is highly seasonal and exhibits inter-annual to inter-decadal variability. A 1154-year δ18O time series obtained from a southwestern Sierra Nevada Mountain stalagmite from Crystal Cave, CRC-3, (36.58°N; 118.56°W; 1540 m) reveals substantial decadal to multi-decadal variability closely linked to the Pacific Decadal Oscillation (PDO), and more specifically, to sea surface temperatures (SSTs) in the Kuroshio Extension region, which impact the atmospheric trajectory and isotopic composition of moisture reaching the study site. The instrumental portion of the CRC-3 δ18O time series suggests that more negative precipitation δ18O values are delivered from higher latitudes during positive phases of the PDO and/or when SSTs in the Kuroshio Extension region are anomalously cool, such as during La Niña events. In order to improve our understanding of the controls on speleothem δ18O in this region, we have conducted a detailed modern study of the climate, hydrology, and stable isotopic composition of meteoric waters (precipitation and drip water) at the cave. Here we present Crystal Cave drip logger results from 2010 to 2012, the isotopic composition of North American Deposition Program precipitation samples collected from 2001 to 2012 from several locations near our site including Ash Mountain (ASM), Sequoia National Park-Giant Forest (Ca75), and Yosemite National Park (Ca99), and isotopic composition of cave drip water and glass plate calcite. We also compare the δ18O values in the precipitation to satellite imagery, NCAR/NCEP data, and NOAA Hysplit Model backward trajectories between the sites. Results indicate that this site is particularly sensitive to "Pineapple Express" type storms, a persistent flow of atmospheric moisture and heavy rainfall extending from near the Hawaiian Islands to the coast of North America, which average about twice as much precipitation as other storms in the Sierra Nevada during winter. Crystal Cave drip logger results indicate a low drip rate variability in the cave between July 2010 and July 2011, averaging between ~25 drips/hour but we observe a significant increase during three "Pineapple Express" type storms (PE) during the 2010-2011 winter. Analysis of the δ18O of precipitation samples collected during these storms events exhibit significantly more negative values which could complicate the interpretation of speleothem δ18O if the relative contribution of PE moisture varies on interannual to multi-decadal timescales.

The Effects of Ashe Juniper on Groundwater Recharge in the Edwards Aquifer

NASA Astrophysics Data System (ADS)

Bazan, R. A.; Wilcox, B. P.; Munster, C. L.; Gregory, L. F.

2008-12-01

Understanding groundwater recharge rates has direct relevance for management of the Edwards Aquifer, which serves as the main source of fresh water for the city of San Antonio and surrounding communities. As population around San Antonio continues to grow, so does the demand for water and the stress placed on the aquifer. A method that is commonly believed to augment water yields is brush management. Recently on the Edwards Plateau decreasing streamflow has coincided with increasing juniper density. This has led many to believe that removing juniper would increase available water. Due to its karstic nature, the recharge zone of the Edwards Aquifer is assumed to be a prime location for augmenting water yields through vegetation manipulation. This study assesses the dynamics of recharge and the effects of manipulating surface vegetation. To accomplish this, a shallow cave located in the Edwards Aquifer recharge zone in San Antonio, Texas was instrumented to monitor drip recharge in response to simulated rainfall events. In 2004, simulations were conducted over the cave to measure recharge rates with a dense Ashe juniper canopy. The data and observations from the initial simulations were used to establish a baseline with the juniper in place. In March 2008 the juniper stand was cleared and the rainfall simulations were reproduced in June and July 2008. Results initially indicated that removing the juniper decreases recharge, however, surface runoff was significantly increased. From the results we can conclude that the dynamics of recharge are affected initially following removal of juniper.

Simulation of different types of ENSO impacts on South Asian Monsoon in CCSM4

NASA Astrophysics Data System (ADS)

Islam, Siraj ul; Tang, Youmin

2017-02-01

It has been found in observation that there are different types of influences of El Nino Southern Oscillation (ENSO) on the South Asian Monsoon (SAM). A correct description and representation of these teleconnections is critical for climate models to simulate and predict SAM. In this study, we examine these teleconnections in NCAR CAM4 and CCSM4 models, including the strength and weakness of these models in preserving different types of ENSO-SAM relationships. By using observational and simulation dataset, the composite analysis, based on specific selection criteria, is performed for both SAM rainfall and the eastern equatorial Pacific sea surface temperature (SST) anomalies. Anomalous SAM rainfall is characterized in three different types i.e. the indirect influence of the SST anomalies of preceding winter (DJF-only), direct influence of the SST anomalies of concurrent summer (JJAS-only) and the combined influence of both preceding winter and concurrent summer (DJF&JJAS). The analysis reveals that CAM4 uncoupled simulation can reasonably well reproduce the anomalous SAM rainfall in DJF-only and DJF&JJAS types whereas the model fails to simulate the anomalous rainfall in the JJAS-only type. The better performance of CAM4, particularly in DJF&JJAS type, comes from its realistic simulation of moisture content and thermal contrast. Its failure to preserve the ENSO-SAM relationship of JJAS-only type is due to the absence of ENSO induced warming in Northern Indian Ocean via atmospheric circulation which is indirectly linked to the lack of air-sea coupling. The role of Indian Ocean in controlling the ENSO-SAM teleconnections of the DJF&JJAS type is further investigated using CAM4 sensitivity experiments. It is found that in absence of Indian Ocean SST, the anomalous SAM summer rainfall suppresses in the DJF&JJAS type, suggesting the important modulation by Indian Ocean SST probably through the preceding winter equatorial Pacific SST forcing and the atmospheric circulations. On the other hand, CCSM4 shows large systematical errors in DJF-only and DJF&JJAS types and reproduce weak anomalous SAM rainfall. The failure of CCSM4 in simulating DJF-only and DJF&JJAS types is found mainly due to the errors in its SST simulation. The JJAS-only type is better reproduced in the CCSM4 simulation as compared to CAM4 and observation composites. Strong convergence over the SAM region which intensifies the anomalous SAM is seen to be responsible for its better simulation in this type. It is found that the atmospheric circulations in CCSM4 contribute more than the thermal contrast in modulating the intensity of anomalous rainfall in JJAS-only type. This study suggests that, although air-sea coupling is important for better SAM simulation and its relationship with ENSO, the SST bias in coupled model can significantly degrade ENSO-SAM relationship.

Hydrological characterization of cave drip waters in a porous limestone: Golgotha Cave, Western Australia

NASA Astrophysics Data System (ADS)

Mahmud, Kashif; Mariethoz, Gregoire; Baker, Andy; Treble, Pauline C.

2018-02-01

Cave drip water response to surface meteorological conditions is complex due to the heterogeneity of water movement in the karst unsaturated zone. Previous studies have focused on the monitoring of fractured rock limestones that have little or no primary porosity. In this study, we aim to further understand infiltration water hydrology in the Tamala Limestone of SW Australia, which is Quaternary aeolianite with primary porosity. We build on our previous studies of the Golgotha Cave system and utilize the existing spatial survey of 29 automated cave drip loggers and a lidar-based flow classification scheme, conducted in the two main chambers of this cave. We find that a daily sampling frequency at our cave site optimizes the capture of drip variability with the least possible sampling artifacts. With the optimum sampling frequency, most of the drip sites show persistent autocorrelation for at least a month, typically much longer, indicating ample storage of water feeding all stalactites investigated. Drip discharge histograms are highly variable, showing sometimes multimodal distributions. Histogram skewness is shown to relate to the wetter-than-average 2013 hydrological year and modality is affected by seasonality. The hydrological classification scheme with respect to mean discharge and the flow variation can distinguish between groundwater flow types in limestones with primary porosity, and the technique could be used to characterize different karst flow paths when high-frequency automated drip logger data are available. We observe little difference in the coefficient of variation (COV) between flow classification types, probably reflecting the ample storage due to the dominance of primary porosity at this cave site. Moreover, we do not find any relationship between drip variability and discharge within similar flow type. Finally, a combination of multidimensional scaling (MDS) and clustering by k means is used to classify similar drip types based on time series analysis. This clustering reveals four unique drip regimes which agree with previous flow type classification for this site. It highlights a spatial homogeneity in drip types in one cave chamber, and spatial heterogeneity in the other, which is in agreement with our understanding of cave chamber morphology and lithology.

Trade-offs between light interception and leaf water shedding: a comparison of shade- and sun-adapted species in a subtropical rainforest.

PubMed

Meng, Fengqun; Cao, Rui; Yang, Dongmei; Niklas, Karl J; Sun, Shucun

2014-01-01

Species in high-rainfall regions have two major alternative approaches to quickly drain off water, i.e., increasing leaf inclination angles relative to the horizontal plane, or developing long leaf drip tips. We hypothesized that shade-adapted species will have more pronounced leaf drip tips but not greater inclination angles (which can reduce the ability to intercept light) compared to sun-adapted species and that length of leaf drip tips will be negatively correlated with photosynthetic capacity [characterized by light-saturated net photosynthetic rates (Amax), associated light compensation points (LCP), and light saturation points (LSP)]. We tested this hypothesis by measuring morphological and physiological traits that are associated with light-interception and water shedding for seven shade-adapted shrub species, ten sun-adapted understory shrub species, and 15 sun-adapted tree species in a subtropical Chinese rainforest, where mean annual precipitation is around 1,600 mm. Shade-adapted understory species had lower LMA, Amax, LSP, and LCP compared to understory or canopy sun-adapted species; their leaf and twig inclination angles were significantly smaller and leaf drip tips were significantly longer than those in sun-adapted species. This suggests that shade-adapted understory species tend to develop pronounced leaf drip tips but not large leaf inclination angles to shed water. The length of leaf drip tips was negatively correlated with leaf inclination angles and photosynthetic capacity. These relationships were consistent between ordinary regression and phylogenetic generalized least squares analyses. Our study illustrates the trade-offs between light interception and leaf water shedding and indicates that length of leaf drip tips can be used as an indicator of adaptation to shady conditions and overall photosynthetic performance of shrub species in subtropical rainforests.

The significance of chemical, isotopic, and detrital components in three coeval stalagmites from the superhumid southernmost Andes (53°S) as high-resolution palaeo-climate proxies

NASA Astrophysics Data System (ADS)

Schimpf, Daniel; Kilian, Rolf; Kronz, Andreas; Simon, Klaus; Spötl, Christoph; Wörner, Gerhard; Deininger, Michael; Mangini, Augusto

2011-02-01

Stalagmites are important palaeo-climatic archives since their chemical and isotopic signatures have the potential to record high-resolution changes in temperature and precipitation over thousands of years. We present three U/Th-dated records of stalagmites (MA1-MA3) in the superhumid southern Andes, Chile (53°S). They grew simultaneously during the last five thousand years (ka BP) in a cave that developed in schist and granodiorite. Major and trace elements as well as the C and O isotope compositions of the stalagmites were analysed at high spatial and temporal resolution as proxies for palaeo-temperature and palaeo-precipitation. Calibrations are based on data from five years of monitoring the climate and hydrology inside and outside the cave and on data from 100 years of regional weather station records. Water-insoluble elements such as Y and HREE in the stalagmites indicate the amount of incorporated siliciclastic detritus. Monitoring shows that the quantity of detritus is controlled by the drip water rate once a threshold level has been exceeded. In general, drip rate variations of the stalagmites depend on the amount of rainfall. However, different drip-water pathways above each drip location gave rise to individual drip rate levels. Only one of the three stalagmites (MA1) had sufficiently high drip rates to record detrital proxies over its complete length. Carbonate-compatible element contents (e.g. U, Sr, Mg), which were measured up to sub-annual resolution, document changes in meteoric precipitation and related drip-water dilution. In addition, these soluble elements are controlled by leaching during weathering of the host rock and soils depending on the pH of acidic pore waters in the peaty soils of the cave's catchment area. In general, higher rainfall resulted in a lower concentration of these elements and vice versa. The Mg/Ca record of stalagmite MA1 was calibrated against meteoric precipitation records for the last 100 years from two regional weather stations. Carbonate-compatible soluble elements show similar patterns in the three stalagmites with generally high values when drip rates and detrital tracers were low and vice versa. δ 13C and δ 18O values are highly correlated in each stalagmite suggesting a predominantly drip rate dependent kinetic control by evaporation and/or outgassing. Only C and O isotopes from stalagmite MA1 that received the highest drip rates show a good correlation between detrital proxy elements and carbonate-compatible elements. A temperature-related change in rainwater isotope values modified the MA1 record during the Little Ice Age (˜0.7-0.1 ka BP) that was ˜1.5 °C colder than today. The isotopic composition of the stalagmites MA2 and MA3 that formed at lower drip rates shows a poor correlation with stalagmite MA1 and all other chemical proxies of MA1. 'Hendy tests' indicate that the degassing-controlled isotope fractionation of MA2 and MA3 had already started at the cave roof, especially when drip rates were low. Changing pathways and residence times of the seepage water caused a non-climatically controlled isotope fractionation, which may be generally important in ventilated caves during phases of low drip rates. Our proxies indicate that the Neoglacial cold phases from ˜3.5 to 2.5 and from ˜0.7 to 0.1 ka BP were characterised by 30% lower precipitation compared with the Medieval Warm Period from 1.2 to 0.8 ka BP, which was extremely humid in this region.

Validation and application of a two-dimensional model to simulate soil salt transport under mulched drip irrigation

NASA Astrophysics Data System (ADS)

Jiao, Huiqing; Zhao, Chengyi; Sheng, Yu; Chen, Yan; Shi, Jianchu; Li, Baoguo

2017-04-01

Water shortage and soil salinization increasingly become the main constraints for sustainable development of agriculture in Southern Xinjiang, China. Mulched drip irrigation, as a high-efficient water-saving irrigation method, has been widely applied in Southern Xinjiang for cotton production. In order to analyze the reasonability of describing the three-dimensional soil water and salt transport processes under mulched drip irrigation with a relatively simple two-dimensional model, a field experiment was conducted from 2007 to 2015 at Aksu of Southern Xinjiang, and soil water and salt transport processes were simulated through the three-dimensional and two-dimensional models based on COMSOL. Obvious differences were found between three-dimensional and two-dimensional simulations for soil water flow within the early 12 h of irrigation event and for soil salt transport in the area within 15 cm away from drip tubes during the whole irrigation event. The soil water and salt contents simulated by the two-dimensional model, however, agreed well with the mean values between two adjacent emitters simulated by the three-dimensional model, and also coincided with the measurements as corresponding RMSE less than 0.037 cm3 cm-3 and 1.80 g kg-1, indicating that the two-dimensional model was reliable for field irrigation management. Subsequently, the two-dimensional model was applied to simulate the dynamics of soil salinity for five numerical situations and for a widely adopted irrigation pattern in Southern Xinjiang (about 350 mm through mulched drip irrigation during growing season of cotton and total 400 mm through flooding irrigations before sowing and after harvesting). The simulation results indicated that the contribution of transpiration to salt accumulation in root layer was about 75% under mulched drip irrigation. Moreover, flooding irrigations before sowing and after harvesting were of great importance for salt leaching of arable layer, especially in bare strip where drip irrigation water hardly reached, and thus providing suitable root zone environment for cotton. Nevertheless, flooding irrigation should be further optimized to enhance water use efficiency.

Subsurface drip irrigation for native wildflower seed production

Treesearch

Clint C. Shock; Erik Feibert; Lamont Saunders; Nancy Shaw

2008-01-01

Native forb seed is needed to restore rangelands of the Intermountain West. Commercial seed production is necessary to provide the quantity of seed needed for restoration efforts. A major limitation to economically viable commercial production of native forb seed is stable and consistent seed productivity over years. Variations in spring rainfall and soil moisture...

Native wildflower seed production with limited subsurface drip irrigation

Treesearch

Clinton C. Shock; Erik B. G. Feibert; Lamont D. Saunders; Nancy Shaw

2010-01-01

Native wildflower seed is needed to restore rangelands of the Intermountain West. Commercial seed production is necessary to provide the quantity of seed needed for restoration efforts. A major limitation to economically viable commercial production of native wildflower (forb) seed is stable and consistent seed productivity over years. Variations in spring rainfall and...

Native wildflower seed production with limited subsurface drip irrigation

Treesearch

Clint C. Shock; Erik Feibert; Lamont Saunders; Nancy Shaw

2009-01-01

Native wildflower seed is needed to restore rangelands of the Intermountain West. Commercial seed production is necessary to provide the quantity of seed needed for restoration efforts. A major limitation to economically viable commercial production of native wildflower (forb) seed is stable and consistent seed productivity over years. Variations in spring rainfall and...

Stochastic modeling of hourly rainfall times series in Campania (Italy)

NASA Astrophysics Data System (ADS)

Giorgio, M.; Greco, R.

2009-04-01

Occurrence of flowslides and floods in small catchments is uneasy to predict, since it is affected by a number of variables, such as mechanical and hydraulic soil properties, slope morphology, vegetation coverage, rainfall spatial and temporal variability. Consequently, landslide risk assessment procedures and early warning systems still rely on simple empirical models based on correlation between recorded rainfall data and observed landslides and/or river discharges. Effectiveness of such systems could be improved by reliable quantitative rainfall prediction, which can allow gaining larger lead-times. Analysis of on-site recorded rainfall height time series represents the most effective approach for a reliable prediction of local temporal evolution of rainfall. Hydrological time series analysis is a widely studied field in hydrology, often carried out by means of autoregressive models, such as AR, ARMA, ARX, ARMAX (e.g. Salas [1992]). Such models gave the best results when applied to the analysis of autocorrelated hydrological time series, like river flow or level time series. Conversely, they are not able to model the behaviour of intermittent time series, like point rainfall height series usually are, especially when recorded with short sampling time intervals. More useful for this issue are the so-called DRIP (Disaggregated Rectangular Intensity Pulse) and NSRP (Neymann-Scott Rectangular Pulse) model [Heneker et al., 2001; Cowpertwait et al., 2002], usually adopted to generate synthetic point rainfall series. In this paper, the DRIP model approach is adopted, in which the sequence of rain storms and dry intervals constituting the structure of rainfall time series is modeled as an alternating renewal process. Final aim of the study is to provide a useful tool to implement an early warning system for hydrogeological risk management. Model calibration has been carried out with hourly rainfall hieght data provided by the rain gauges of Campania Region civil protection agency meteorological warning network. ACKNOWLEDGEMENTS The research was co-financed by the Italian Ministry of University, by means of the PRIN 2006 PRIN program, within the research project entitled ‘Definition of critical rainfall thresholds for destructive landslides for civil protection purposes'. REFERENCES Cowpertwait, P.S.P., Kilsby, C.G. and O'Connell, P.E., 2002. A space-time Neyman-Scott model of rainfall: Empirical analysis of extremes, Water Resources Research, 38(8):1-14. Salas, J.D., 1992. Analysis and modeling of hydrological time series, in D.R. Maidment, ed., Handbook of Hydrology, McGraw-Hill, New York. Heneker, T.M., Lambert, M.F. and Kuczera G., 2001. A point rainfall model for risk-based design, Journal of Hydrology, 247(1-2):54-71.

Simulation of precipitation by weather pattern and frontal analysis

NASA Astrophysics Data System (ADS)

Wilby, Robert

1995-12-01

Daily rainfall from two sites in central and southern England was stratified according to the presence or absence of weather fronts and then cross-tabulated with the prevailing Lamb Weather Type (LWT). A semi-Markov chain model was developed for simulating daily sequences of LWTs from matrices of transition probabilities between weather types for the British Isles 1970-1990. Daily and annual rainfall distributions were then simulated from the prevailing LWTs using historic conditional probabilities for precipitation occurrence and frontal frequencies. When compared with a conventional rainfall generator the frontal model produced improved estimates of the overall size distribution of daily rainfall amounts and in particular the incidence of low-frequency high-magnitude totals. Further research is required to establish the contribution of individual frontal sub-classes to daily rainfall totals and of long-term fluctuations in frontal frequencies to conditional probabilities.

Seasonal dripwater Mg/Ca and Sr/Ca variations driven by cave ventilation: Implications for and modeling of speleothem paleoclimate records

USGS Publications Warehouse

Wong, C.I.; Banner, J.L.; Musgrove, M.

2011-01-01

A 4-year study in a central Texas cave quantifies multiple mechanisms that control dripwater composition and how these mechanisms vary at different drip sites. We monitored cave-air compositions, in situ calcite growth, dripwater composition and drip rate every 4-6weeks. Three groups of drip sites are delineated (Groups 1-3) based on geochemical variations in dripwater composition. Quantitative modeling of mineral-solution reactions within the host carbonate rock and cave environments is used to identify mechanisms that can account for variations in dripwater compositions. The covariation of Mg/Ca (and Sr/Ca) and Sr isotopes is key in delineating whether Mg/Ca and Sr/Ca variations are dictated by water-rock interaction (i.e., calcite or dolomite recrystallization) or prior calcite precipitation (PCP). Group 1 dripwater compositions reflects a narrow range of the extent of water-rock interaction followed by varying amounts of prior calcite precipitation (PCP). Group 2 dripwater compositions are controlled by varying amounts of water-rock interaction with little to no PCP influence. Group 3 dripwater compositions are dictated by variable extents of both water-rock interaction and PCP. Group 1 drip sites show seasonal variations in dripwater Mg/Ca and Sr/Ca, whereas the other drip sites do not. In contrast to the findings of most previous dripwater Mg/Ca-Sr/Ca studies, these seasonal variations (at Group 1 drip sites) are independent of changes in water flux (i.e., rainfall and/or drip rate), and instead significantly correlate with changes in cave-air CO2 concentrations. These results are consistent with lower cave-air CO2, related to cool season ventilation of the cave atmosphere, enhancing calcite precipitation and leading to dripwater geochemical evolution via PCP. Group 1 dripwater Mg/Ca and Sr/Ca seasonality and evidence for PCP as a mechanism that can account for that seasonality, have two implications for many other regions where seasonal ventilation of caves is likely: (1) speleothem trace-element records may provide seasonal signals, and (2) such records may be biased toward recording climate conditions during the season when calcite is depositing. Additionally, we use our results to construct a forward model that illustrates the types of speleothem Mg/Ca and Sr/Ca variations that would result from varying controls on dripwater compositions. The model provides a basis for interpreting paleo-dripwater controls from high frequency Mg/Ca and Sr/Ca variations for speleothems from caves at which long term monitoring studies are not feasible. ?? 2011 Elsevier Ltd.

Determining erosion relevant soil characteristics with a small-scale rainfall simulator

NASA Astrophysics Data System (ADS)

Schindewolf, M.; Schmidt, J.

2009-04-01

The use of soil erosion models is of great importance in soil and water conservation. Routine application of these models on the regional scale is not at least limited by the high parameter demands. Although the EROSION 3D simulation model is operating with a comparable low number of parameters, some of the model input variables could only be determined by rainfall simulation experiments. The existing data base of EROSION 3D was created in the mid 90s based on large-scale rainfall simulation experiments on 22x2m sized experimental plots. Up to now this data base does not cover all soil and field conditions adequately. Therefore a new campaign of experiments would be essential to produce additional information especially with respect to the effects of new soil management practices (e.g. long time conservation tillage, non tillage). The rainfall simulator used in the actual campaign consists of 30 identic modules, which are equipped with oscillating rainfall nozzles. Veejet 80/100 (Spraying Systems Co., Wheaton, IL) are used in order to ensure best possible comparability to natural rainfalls with respect to raindrop size distribution and momentum transfer. Central objectives of the small-scale rainfall simulator are - effectively application - provision of comparable results to large-scale rainfall simulation experiments. A crucial problem in using the small scale simulator is the restriction on rather small volume rates of surface runoff. Under this conditions soil detachment is governed by raindrop impact. Thus impact of surface runoff on particle detachment cannot be reproduced adequately by a small-scale rainfall simulator With this problem in mind this paper presents an enhanced small-scale simulator which allows a virtual multiplication of the plot length by feeding additional sediment loaded water to the plot from upstream. Thus is possible to overcome the plot length limited to 3m while reproducing nearly similar flow conditions as in rainfall experiments on standard plots. The simulator is extensively applied to plots of different soil types, crop types and management systems. The comparison with existing data sets obtained by large-scale rainfall simulations show that results can adequately be reproduced by the applied combination of small-scale rainfall simulator and sediment loaded water influx.

Rainfall Control of Karst Solution and the Inter/Intra Annual Hydrogeochemical Evolution of Cave Dripwater: A Long-term, Site-specific Study, Soreq Cave, Israel

NASA Astrophysics Data System (ADS)

Burstyn, Yuval; Bar-Matthews, Miryam; Ayalon, Avner; Matthews, Alan

2016-04-01

Speleothem laminae preserve climate information transferred to the cave via dripwater. High spatial resolution methods allow in situ measurement of geochemical and isotopic proxies at seasonal resolution. Existing hydrogeochemical calibration models suggest that high rainfall inhibits karst water chemical evolution, resulting in low δ 18O values, and low Mg/Ca and Sr/Ca ratios that are not necessarily correlated. Drought periods display opposite chemical behaviour owing to lower infiltration rates and increased Prior Calcite Precipitation (PCP). This study aims to provide a site-specific, high-resolution hydrogeochemical calibration for the Soreq Cave. We examine four sites that were continuously sampled since 1990. Four main rainfall conditions are characterized: very wet years, average, drought and very dry years. Two sites are fed by 'fast drips', which only become active after ˜ 250mm rainfall has accumulated since the beginning of the winter season. Two sites, located deeper in the cave, are fed by 'slow drips' that are active all year round. Drip rate measurements identify two main reservoirs - fissure and matrix - that mainly differ in residence time. The δ 18O of fissure water is closer to that of mean annual rainfall (˜ -6 ‰VSMOW), while matrix values are higher (˜ -3.5 ‰VSMOW). Two main Sr and Mg sources are identified - dolomitic bedrock (Mg/Ca ˜ 700 mM/M, Sr/Ca ˜ 0.4 mM/M) and soil leachate (Mg/Ca ˜ 300 mM/M, Sr/Ca ˜ 1.1 mM/M). Most cave dripwater evolves from ˜ 1:1 soil-bedrock solution. PCP effect on dripwater solution at each site is estimated by comparing the ln(Mg/Ca) vs ln(Sr/Ca) linear slope to the PCP slope calculated using cave specific D(Mg) and D(Sr). Soreq Cave PCP slope is similar to the global slope of 0.88± 0.13. The composition and chemical evolution of each reservoir and its contribution to water influx at each site is primarily governed by annual effective infiltration. Higher seasonal amplitude in δ 18O, Mg/Ca and Sr/Ca in all sites is positively correlated to increase in rainfall. For the deeper site, with rock cover of >40 m, the `classic' wet-dry model can be applied - more soil input and less PCP in the wetter years and vice-versa. Conversely, in the shallower sites, high PCP is observed in wetter years. Results from this study are compared with high-resolution δ 18O and trace element records of modern speleothems (age ˜ 20y). The speleothem from the deeper site shows a good match with the hydrogeochemical data, thus supporting the applicability of the model to palaeoclimate studies. However, the speleothem from the shallow site shows a strong winter bias, which may be due to complete secession of summer drip during dry years (micro-hiatuses), or during wetter years, considerable winter calcite precipitation resulting in minimal summer imprint on each seasonal lamina. We plan to analyse a fast growing modern sample from the shallow site to resolve this seasonal bias. Therefore, contemporaneous speleothem records from different sites can be utilized to estimate past changes in annual and decadal effective infiltration, allowing evaluation of water availability in the region during periods of rapid climate change. [1] Orland, I.J. et al. 2014. Chemical Geology, v. 363, p. 322-333.

Rainfall-induced release of microbes from manure: model development, parameter estimation, and uncertainty evaluation on small plots

USDA-ARS?s Scientific Manuscript database

A series of simulated rainfall-runoff experiments with applications of different manure types (cattle solid pats, poultry dry litter, swine slurry) were conducted across four seasons on a field containing 36 plots (0.75 × 2 m each), resulting in 144 rainfall-runoff events. Simulating time-varying re...

Mini rainfall simulation for assessing soil erodibility

NASA Astrophysics Data System (ADS)

Peters, Piet; Palese, Dina; Baartman, Jantiene

2016-04-01

The mini rainfall simulator is a small portable rainfall simulator to determine erosion and water infiltration characteristics of soils. The advantages of the mini rainfall simulator are that it is suitable for soil conservation surveys and light and easy to handle in the field. Practical experience over the last decade has shown that the used 'standard' shower is a reliable method to assess differences in erodibility due to soil type and/or land use. The mini rainfall simulator was used recently in a study on soil erosion in olive groves (Ferrandina-Italy). The propensity to erosion of a steep rain-fed olive grove (mean slope ~10%) with a sandy loam soil was evaluated by measuring runoff and sediment load under extreme rain events. Two types of soil management were compared: spontaneous grass as a ground cover (GC) and tillage (1 day (T1) and 10 days after tillage (T2)). Results indicate that groundcover reduced surface runoff to approximately one-third and soil-losses to zero compared with T1. The runoff between the two tilled plots was similar, although runoff on T1 plots increased steadily over time whereas runoff on T2 plots remained stable.

Small scale rainfall simulators: Challenges for a future use in soil erosion research

NASA Astrophysics Data System (ADS)

Ries, Johannes B.; Iserloh, Thomas; Seeger, Manuel

2013-04-01

Rainfall simulation on micro-plot scale is a method used worldwide to assess the generation of overland flow, soil erosion, infiltration and interrelated processes such as soil sealing, crusting, splash and redistribution of solids and solutes. The produced data are of great significance not only for the analysis of the simulated processes, but also as a source of input-data for soil erosion modelling. The reliability of the data is therefore of paramount importance, and quality management of rainfall simulation procedure a general responsibility of the rainfall simulation community. This was an accepted outcome at the "International Rainfall Simulator Workshop 2011" at Trier University. The challenges of the present and near future use of small scale rainfall simulations concern the comparability of results and scales, the quality of the data for soil erosion modelling, and further technical developments to overcome physical limitations and constraints. Regarding the high number of research questions, different fields of application, and due to the great technical creativity of researchers, a large number of different types of rainfall simulators is available. But each of the devices produces a different rainfall, leading to different kinetic energy values influencing soil surface and erosion processes. Plot sizes are also variable, as well as the experimental simulation procedures. As a consequence, differing runoff and erosion results are produced. The presentation summarises the three important aspects of rainfall simulations, following a processual order: 1. Input-factor "rain" and its calibration 2. Surface-factor "plot" and its documentation 3. Output-factors "runoff" and "sediment concentration" Finally, general considerations about the limitations and challenges for further developments and applications of rainfall simulation data are presented.

Rainfall simulation experiments in the southwestern USA using the Walnut Gulch Rainfall Simulator

NASA Astrophysics Data System (ADS)

Polyakov, Viktor; Stone, Jeffry; Holifield Collins, Chandra; Nearing, Mark A.; Paige, Ginger; Buono, Jared; Gomez-Pond, Rae-Landa

2018-01-01

This dataset contains hydrological, erosion, vegetation, ground cover, and other supplementary information from 272 rainfall simulation experiments conducted on 23 semiarid rangeland locations in Arizona and Nevada between 2002 and 2013. On 30 % of the plots, simulations were conducted up to five times during the decade of study. The rainfall was generated using the Walnut Gulch Rainfall Simulator on 2 m by 6 m plots. Simulation sites included brush and grassland areas with various degrees of disturbance by grazing, wildfire, or brush removal. This dataset advances our understanding of basic hydrological and biological processes that drive soil erosion on arid rangelands. It can be used to estimate runoff, infiltration, and erosion rates at a variety of ecological sites in the Southwestern USA. The inclusion of wildfire and brush treatment locations combined with long-term observations makes it important for studying vegetation recovery, ecological transitions, and the effect of management. It is also a valuable resource for erosion model parameterization and validation. The dataset is available from the National Agricultural Library at https://data.nal.usda.gov/search/type/dataset (DOI: https://doi.org/10.15482/USDA.ADC/1358583).

Mass Balance of Water and Nitrogen in the Mounded Drainfield of a Drip-Dispersal Septic System.

PubMed

De, Mriganka; Toor, Gurpal S

2016-07-01

Quantitative assessment of nitrogen (N) loading from septic systems is needed to protect groundwater contamination. We determined the mass balance of water and N in the mounded drainfield of a drip-dispersal septic system. Three lysimeters (152.4 cm long, 91.4 cm wide, 91.4 cm high, with 1:1 side slope) were constructed using pressure-treated wood to mimic mounded drainfields. Of total water inputs, septic tank effluent (STE) added 57% water and natural rainfall added 43% water from January 2013 to January 2014. Outputs included leached water (46%) from the lysimeters over 67 sampling events ( = 15 daily and = 52 weekly flow-weighted), potential evapotranspiration (28%), and water stored in the drainfields (26%). Over 13 mo, each drainfield received 227 g of total N (STE, 99%; rainfall, 1%), of which 33% leached, 23% accumulated in the drainfield, and 6% was taken up by grass, with the remainder (38%) estimated to be gaseous N loss. Using these data, the leaching of water from 2.5 million drip-dispersal drainfields in the state of Florida was estimated to be 2.29 × 10 L yr, which would transport 2.4 × 10 kg of total N yr from the drainfields to shallow groundwater. Further reduction of N below drainfields in the soil profile could be expected before STE reaches groundwater. Our results provide quantitative information on the water and N loading and can be used to optimize drainfield conditions to attenuate N and protect groundwater quality. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

[Three-dimension temporal and spatial dynamics of soil water for the artificial vegetation in the center of Taklimakan desert under saline water drip-irrigation].

PubMed

Ding, Xin-yuan; Zhou, Zhi-bin; Xu, Xin-wen; Lei, Jia-qiang; Lu, Jing-jing; Ma, Xue-xi; Feng, Xiao

2015-09-01

Three-dimension temporal and spatial dynamics of the soil water characteristics during four irrigating cycles of months from April to July for the artificial vegetation in the center of Taklimakan Desert under saline water drip-irrigation had been analyzed by timely measuring the soil water content in horizontal and vertical distances 60 cm and 120 cm away from the irrigating drips, respectively. Periodic spatial and temporal variations of soil water content were observed. When the precipitation effect was not considered, there were no significant differences in the characteristics of soil water among the irrigation intervals in different months, while discrepancies were obvious in the temporal and spatial changes of soil moisture content under the conditions of rainfall and non-rainfall. When it referred to the temporal changes of soil water, it was a little higher in April but a bit lower in July, and the soil water content in June was the highest among four months because some remarkable events of precipitation happened in this month. However, as a whole, the content of soil moisture was reduced as months (from April to July) went on and it took a decreasing tendency along with days (1-15 d) following a power function. Meanwhile, the characteristics of soil water content displayed three changeable stages in an irrigation interval. When it referred to the spatial distributions of soil water, the average content of soil moisture was reduced along with the horizontal distance following a linear regression function, and varied with double peaks along with the vertical distance. In addition, the spatial distribution characteristics of the soil water were not influenced by the factors of precipitation and irrigating time but the physical properties of soil.

An assessment of the ability of Bartlett-Lewis type of rainfall models to reproduce drought statistics

NASA Astrophysics Data System (ADS)

Pham, M. T.; Vanhaute, W. J.; Vandenberghe, S.; De Baets, B.; Verhoest, N. E. C.

2013-12-01

Of all natural disasters, the economic and environmental consequences of droughts are among the highest because of their longevity and widespread spatial extent. Because of their extreme behaviour, studying droughts generally requires long time series of historical climate data. Rainfall is a very important variable for calculating drought statistics, for quantifying historical droughts or for assessing the impact on other hydrological (e.g. water stage in rivers) or agricultural (e.g. irrigation requirements) variables. Unfortunately, time series of historical observations are often too short for such assessments. To circumvent this, one may rely on the synthetic rainfall time series from stochastic point process rainfall models, such as Bartlett-Lewis models. The present study investigates whether drought statistics are preserved when simulating rainfall with Bartlett-Lewis models. Therefore, a 105 yr 10 min rainfall time series obtained at Uccle, Belgium is used as a test case. First, drought events were identified on the basis of the Effective Drought Index (EDI), and each event was characterized by two variables, i.e. drought duration (D) and drought severity (S). As both parameters are interdependent, a multivariate distribution function, which makes use of a copula, was fitted. Based on the copula, four types of drought return periods are calculated for observed as well as simulated droughts and are used to evaluate the ability of the rainfall models to simulate drought events with the appropriate characteristics. Overall, all Bartlett-Lewis model types studied fail to preserve extreme drought statistics, which is attributed to the model structure and to the model stationarity caused by maintaining the same parameter set during the whole simulation period.

A copula-based assessment of Bartlett-Lewis type of rainfall models for preserving drought statistics

NASA Astrophysics Data System (ADS)

Pham, M. T.; Vanhaute, W. J.; Vandenberghe, S.; De Baets, B.; Verhoest, N. E. C.

2013-06-01

Of all natural disasters, the economic and environmental consequences of droughts are among the highest because of their longevity and widespread spatial extent. Because of their extreme behaviour, studying droughts generally requires long time series of historical climate data. Rainfall is a very important variable for calculating drought statistics, for quantifying historical droughts or for assessing the impact on other hydrological (e.g. water stage in rivers) or agricultural (e.g. irrigation requirements) variables. Unfortunately, time series of historical observations are often too short for such assessments. To circumvent this, one may rely on the synthetic rainfall time series from stochastic point process rainfall models, such as Bartlett-Lewis models. The present study investigates whether drought statistics are preserved when simulating rainfall with Bartlett-Lewis models. Therefore, a 105 yr 10 min rainfall time series obtained at Uccle, Belgium is used as test case. First, drought events were identified on the basis of the Effective Drought Index (EDI), and each event was characterized by two variables, i.e. drought duration (D) and drought severity (S). As both parameters are interdependent, a multivariate distribution function, which makes use of a copula, was fitted. Based on the copula, four types of drought return periods are calculated for observed as well as simulated droughts and are used to evaluate the ability of the rainfall models to simulate drought events with the appropriate characteristics. Overall, all Bartlett-Lewis type of models studied fail in preserving extreme drought statistics, which is attributed to the model structure and to the model stationarity caused by maintaining the same parameter set during the whole simulation period.

Stormwater harvesting for irrigation purposes: an investigation of chemical quality of water recycled in pervious pavement system.

PubMed

Nnadi, Ernest O; Newman, Alan P; Coupe, Stephen J; Mbanaso, Fredrick U

2015-01-01

Most available water resources in the world are used for agricultural irrigation. Whilst this level of water use is expected to increase due to rising world population and land use, available water resources are expected to become limited due to climate change and uneven rainfall distribution. Recycled stormwater has the potential to be used as an alternative source of irrigation water and part of sustainable water management strategy. This paper reports on a study to investigate whether a sustainable urban drainage system (SUDS) technique, known as the pervious pavements system (PPS) has the capability to recycle water that meets irrigation water quality standard. Furthermore, the experiment provided information on the impact of hydrocarbon (which was applied to simulate oil dripping from parked vehicles onto PPS), leaching of nutrients from different layers of the PPS and effects of nutrients (applied to enhance bioremediation) on the stormwater recycling efficiency of the PPS. A weekly dose of 6.23 × 10(-3) L of lubricating oil and single dose of 17.06 g of polymer coated controlled-release fertilizer granules were applied to the series of 710 mm × 360 mm model pervious pavement structure except the controls. Rainfall intensity of 7.4 mm/h was applied to the test models at the rate of 3 events per week. Analysis of the recycled water showed that PPS has the capability to recycle stormwater to a quality that meets the chemical standards for use in agricultural irrigation irrespective of the type of sub-base used. There is a potential benefit of nutrient availability in recycled water for plants, but care should be taken not to dispose of this water in natural water courses as it might result in eutrophication problems. Copyright © 2014 Elsevier Ltd. All rights reserved.

Combining spray nozzle simulators with meshes: characterization of rainfall intensity and drop properties

NASA Astrophysics Data System (ADS)

Carvalho, Sílvia C. P.; de Lima, João L. M. P.; de Lima, M. Isabel P.

2013-04-01

Rainfall simulators can be a powerful tool to increase our understanding of hydrological and geomorphological processes. Nevertheless, rainfall simulators' design and operation might be rather demanding, for achieving specific rainfall intensity distributions and drop characteristics. The pressurized simulators have some advantages over the non-pressurized simulators: drops do not rely on gravity to reach terminal velocity, but are sprayed out under pressure; pressurized simulators also yield a broad range of drop sizes in comparison with drop-formers simulators. The main purpose of this study was to explore in the laboratory the potential of combining spray nozzle simulators with meshes in order to change rainfall characteristics (rainfall intensity and diameters and fall speed of drops). Different types of spray nozzles were tested, such as single full-cone and multiple full-cone nozzles. The impact of the meshes on the simulated rain was studied by testing different materials (i.e. plastic and steel meshes), square apertures and wire thicknesses, and different vertical distances between the nozzle and the meshes underneath. The diameter and fall speed of the rain drops were measured using a Laser Precipitation Monitor (Thies Clima). The rainfall intensity range and coefficients of uniformity of the sprays and the drop size distribution, fall speed and kinetic energy were analysed. Results show that when meshes intercept drop trajectories the spatial distribution of rainfall intensity and the drop size distribution are affected. As the spray nozzles generate typically small drop sizes and narrow drop size distributions, meshes can be used to promote the formation of bigger drops and random their landing positions.

Dissolution of three insensitive munitions formulations.

PubMed

Taylor, Susan; Park, Eileen; Bullion, Katherine; Dontsova, Katerina

2015-01-01

The US military fires live munitions during training. To save soldiers lives both during training and war, the military is developing insensitive munitions (IM) that minimize unintentional detonations. Some of the compounds in the IM formulation are, however, very soluble in water, raising environmental concerns about their fate and transport. We measured the dissolution of three of these IM formulations, IMX101, IMX104 and PAX21 using laboratory drip tests and studied the accompanying changes in particle structure using micro computed tomography. Our laboratory drip tests mimic conditions on training ranges, where spatially isolated particles of explosives scattered by partial detonations are dissolved by rainfall. We found that the constituents of these IM formulations dissolve sequentially and in the order predicted by their aqueous solubility. The order of magnitude differences in solubility among their constituents produce water solutions whose compositions and concentrations vary with time. For IMX101 and IMX104, that contain 3-nitro-1,2,4-triazol-5-one (NTO), the solutions also vary in pH. The good mass balances measured for the drip tests indicate that the formulations are not being photo-or bio-transformed under laboratory conditions. Published by Elsevier Ltd.

Deep subsurface drip irrigation using coal-bed sodic water: part II. geochemistry

USGS Publications Warehouse

Bern, Carleton R.; Breit, George N.; Healy, Richard W.; Zupancic, John W.

2013-01-01

Waters with low salinity and high sodium adsorption ratios (SARs) present a challenge to irrigation because they degrade soil structure and infiltration capacity. In the Powder River Basin of Wyoming, such low salinity (electrical conductivity, EC 2.1 mS cm-1) and high-SAR (54) waters are co-produced with coal-bed methane and some are used for subsurface drip irrigation(SDI). The SDI system studied mixes sulfuric acid with irrigation water and applies water year-round via drip tubing buried 92 cm deep. After six years of irrigation, SAR values between 0 and 30 cm depth (0.5-1.2) are only slightly increased over non-irrigated soils (0.1-0.5). Only 8-15% of added Na has accumulated above the drip tubing. Sodicity has increased in soil surrounding the drip tubing, and geochemical simulations show that two pathways can generate sodic conditions. In soil between 45-cm depth and the drip tubing, Na from the irrigation water accumulates as evapotranspiration concentrates solutes. SAR values >12, measured by 1:1 water-soil extracts, are caused by concentration of solutes by factors up to 13. Low-EC (-1) is caused by rain and snowmelt flushing the soil and displacing ions in soil solution. Soil below the drip tubing experiences lower solute concentration factors (1-1.65) due to excess irrigation water and also contains relatively abundant native gypsum (2.4 ± 1.7 wt.%). Geochemical simulations show gypsum dissolution decreases soil-water SAR to 14 and decreasing EC in soil water to 3.2 mS cm-1. Increased sodicity in the subsurface, rather than the surface, indicates that deep SDI can be a viable means of irrigating with sodic waters.

Evaluation of rainfall structure on hydrograph simulation: Comparison of radar and interpolated methods, a study case in a tropical catchment

NASA Astrophysics Data System (ADS)

Velasquez, N.; Ochoa, A.; Castillo, S.; Hoyos Ortiz, C. D.

2017-12-01

The skill of river discharge simulation using hydrological models strongly depends on the quality and spatio-temporal representativeness of precipitation during storm events. All precipitation measurement strategies have their own strengths and weaknesses that translate into discharge simulation uncertainties. Distributed hydrological models are based on evolving rainfall fields in the same time scale as the hydrological simulation. In general, rainfall measurements from a dense and well maintained rain gauge network provide a very good estimation of the total volume for each rainfall event, however, the spatial structure relies on interpolation strategies introducing considerable uncertainty in the simulation process. On the other hand, rainfall retrievals from radar reflectivity achieve a better spatial structure representation but with higher uncertainty in the surface precipitation intensity and volume depending on the vertical rainfall characteristics and radar scan strategy. To assess the impact of both rainfall measurement methodologies on hydrological simulations, and in particular the effects of the rainfall spatio-temporal variability, a numerical modeling experiment is proposed including the use of a novel QPE (Quantitative Precipitation Estimation) method based on disdrometer data in order to estimate surface rainfall from radar reflectivity. The experiment is based on the simulation of 84 storms, the hydrological simulations are carried out using radar QPE and two different interpolation methods (IDW and TIN), and the assessment of simulated peak flow. Results show significant rainfall differences between radar QPE and the interpolated fields, evidencing a poor representation of storms in the interpolated fields, which tend to miss the precise location of the intense precipitation cores, and to artificially generate rainfall in some areas of the catchment. Regarding streamflow modelling, the potential improvement achieved by using radar QPE depends on the density of the rain gauge network and its distribution relative to the precipitation events. The results for the 84 storms show a better model skill using radar QPE than the interpolated fields. Results using interpolated fields are highly affected by the dominant rainfall type and the basin scale.

Rainfall-induced release of microbes from manure: model development, parameter estimation, and uncertainty evaluation on small plots

EPA Science Inventory

A series of simulated rainfall run-off experiments with applications of different manure types (cattle solid pats, poultry dry litter, swine slurry) was conducted across four seasons on a field containing 36 plots (0.75 × 2 m each), resulting in 144 rainfall run-off events....

Comparison of Spring and Cave Drip Water in Westcave Preserve, Central Texas May Reveal Epikarst CO2 Degassing

NASA Astrophysics Data System (ADS)

Carlson, P.; Banner, J. L.; Casteel, R. C.; Breecker, D.

2013-12-01

The cave at Westcave Preserve, in central Texas, is a unique location to study karst processes due to its low, nearly atmospheric cave-air CO2 levels and seasonally variable temperature. The source of water that drips into the cave, however, has not been constrained, limiting interpretation of climate proxies in the cave. It is possible that a nearby spring and the cave drip-waters share a common source. Alternatively, the drip-waters could represent precipitation that has infiltrated the host rock. These hypotheses should be tested using Sr isotope ratios and/or other tracers. If they do share a common source, analysis of dissolved inorganic carbon (DIC) concentration , δ13CDIC, and cation concentrations of the two waters could provide insight into epikarst processes such as CO2 degassing and prior calcite precipitation (PCP) that are otherwise difficult to constrain. Westcave Preserve includes outcrops of the Hensell Sand, the Cow Creek Limestone, and the Hammett Shale, with a small cave at the contact between the Cow Creek and Hammett formations. The overlying Hensell Sand contains water that emerges at the surface as a spring near the cave. Water also drips directly into the cave, forming speleothems. Previous research has established that although δ18O values of rainfall in the area vary seasonally, between -10.5 and 1.1‰ with a weighted mean of -6.5‰ (VSMOW), the drip-water varies only between -4.7 and -4.3‰ with a weighted mean of -4.5‰ (Feng et al., in review). This suggests a large well-mixed reservoir above the cave. The soils above the cave have high CO2 of up to 17,500 ppmv, but because the cave is shallow with multiple large openings, cave CO2 levels are near-atmospheric (Casteel and Banner, in review). This creates a steep CO2 gradient between the soil and the cave air. The spring water DIC is nearly in carbon-isotope equilibrium with the soil CO2, suggesting that soil respiration, here controlled by C3 plants, is the primary source of CO2 for this reservoir. The drip water δ13CDIC is higher than the spring water (-10.3‰ versus -13.0‰). Although the spring water has higher DIC concentration than the drip water, with mean values of 128 mg/L C versus 113 mg/L C, respectively, preliminary data suggest that for some drips, the drip water DIC concentrations and δ13CDIC may vary with spring DIC values. We propose that if the spring and the drip water prove to be derived from the same source, the differences in DIC and δ13CDIC between spring and drip water are due to epikarst CO2 degassing as the water percolates down the CO2 gradient toward the cave ceiling. If the spring represents the source of the drip water, the calculated δ13 value of degassed CO2 is -33.3‰, assuming no PCP. PCP may occur, leading to a δ13C of degassed CO2 lower than calculated, but would result in a decrease or no change in δ13CDIC and therefore does not explain the observed difference between spring water and drip water.

Qualitative comparison of soil erosion, runoff and infiltration coefficients using small portable rainfall simulators in Germany, Spain and France

NASA Astrophysics Data System (ADS)

Rodrigo Comino, Jesús; Iserloh, Thomas; Morvan, Xavier; Malam Issa, Oumarou; Naisse, Christophe; Keesstra, Saskia; Cerdà, Artemi; Prosdocimi, Massimo; Arnáez, José; Lasanta, Teodoro; Concepción Ramos, María; José Marqués, María; Ruiz Colmenero, Marta; Bienes, Ramón; Damián Ruiz Sinoga, José; Seeger, Manuel; Ries, Johannes B.

2016-04-01

Small portable rainfall simulators are considered as a useful tool to analyze soil erosion processes in cultivated lands. European research groups of Spain (Valencia, Málaga, Lleida, Madrid and La Rioja), France (Reims) or Germany (Trier) have used different rainfall simulators (varying in drop size distribution and fall velocities, kinetic energy, plot forms and sizes, and field of application)to study soil loss, surface flow, runoff and infiltration coefficients in different experimental plots (Valencia, Montes de Málaga, Penedès, Campo Real and La Rioja in Spain, Champagne in France and Mosel-Ruwer valley in Germany). The measurements and experiments developed by these research teams give an overview of the variety in the methodologies with rainfall simulations in studying the problem of soil erosion and describing the erosion features in different climatic environments, management practices and soil types. The aim of this study is: i) to investigate where, how and why researchers from different wine-growing regions applied rainfall simulations with successful results as a tool to measure soil erosion processes; ii) to make a qualitative comparison about the general soil erosion processes in European terroirs; iii) to demonstrate the importance of the development a standard method for soil erosion processes in vineyards, using rainfall simulators; iv) and to analyze the key factors that should be taken into account to carry out rainfall simulations. The rainfall simulations in all cases allowed knowing the infiltration capacity and the susceptibility of the soil to be detached and to generate sediment loads to runoff. Despite using small plots, the experiments were useful to analyze the influence of soil cover to reduce soil erosion and to make comparison between different locations or the influence of different soil characteristics.

Addressing the mischaracterization of extreme rainfall in regional climate model simulations - A synoptic pattern based bias correction approach

NASA Astrophysics Data System (ADS)

Li, Jingwan; Sharma, Ashish; Evans, Jason; Johnson, Fiona

2018-01-01

Addressing systematic biases in regional climate model simulations of extreme rainfall is a necessary first step before assessing changes in future rainfall extremes. Commonly used bias correction methods are designed to match statistics of the overall simulated rainfall with observations. This assumes that change in the mix of different types of extreme rainfall events (i.e. convective and non-convective) in a warmer climate is of little relevance in the estimation of overall change, an assumption that is not supported by empirical or physical evidence. This study proposes an alternative approach to account for the potential change of alternate rainfall types, characterized here by synoptic weather patterns (SPs) using self-organizing maps classification. The objective of this study is to evaluate the added influence of SPs on the bias correction, which is achieved by comparing the corrected distribution of future extreme rainfall with that using conventional quantile mapping. A comprehensive synthetic experiment is first defined to investigate the conditions under which the additional information of SPs makes a significant difference to the bias correction. Using over 600,000 synthetic cases, statistically significant differences are found to be present in 46% cases. This is followed by a case study over the Sydney region using a high-resolution run of the Weather Research and Forecasting (WRF) regional climate model, which indicates a small change in the proportions of the SPs and a statistically significant change in the extreme rainfall over the region, although the differences between the changes obtained from the two bias correction methods are not statistically significant.

Soil erodibility variability in laboratory and field rainfall simulations

NASA Astrophysics Data System (ADS)

Szabó, Boglárka; Szabó, Judit; Jakab, Gergely; Centeri, Csaba; Szalai, Zoltán

2017-04-01

Rainfall simulation experiments are the most common way to observe and to model the soil erosion processes in in situ and ex situ circumstances. During modelling soil erosion, one of the most important factors are the annual soil loss and the soil erodibility which represent the effect of soil properties on soil loss and the soil resistance against water erosion. The amount of runoff and soil loss can differ in case of the same soil type, while it's characteristics determine the soil erodibility factor. This leads to uncertainties regarding soil erodibility. Soil loss and soil erodibility were examined with the investigation of the same soil under laboratory and field conditions with rainfall simulators. The comparative measurement was carried out in a laboratory on 0,5 m2, and in the field (Shower Power-02) on 6 m2 plot size where the applied slope angles were 5% and 12% with 30 and 90 mm/h rainfall intensity. The main idea was to examine and compare the soil erodibility and its variability coming from the same soil, but different rainfall simulator type. The applied model was the USLE, nomograph and other equations which concern single rainfall events. The given results show differences between the field and laboratory experiments and between the different calculations. Concerning for the whole rainfall events runoff and soil loss, were significantly higher at the laboratory experiments, which affected the soil erodibility values too. The given differences can originate from the plot size. The main research questions are that: How should we handle the soil erodibility factors and its significant variability? What is the best solution for soil erodibility determination?

The Role of Fog in Ecosystem Hydrology: Initial Results from Investigations Using Stable Isotopes of Water in Hawaiian Cloud Forests

NASA Astrophysics Data System (ADS)

Scholl, M. A.; Gingerich, S. B.; Giambelluca, T. W.; Nullet, M. A.; Loope, L. L.

2002-05-01

The role of fog drip in cloud forest ecosystems is being investigated at two sites, one each on the windward and leeward sides of East Maui, Hawaii. The study involves using the different isotopic signatures of fog (cloud water) and rain to trace fog through the forest water cycle, as well as comparing relative amounts of fog, rain, and throughfall. At each site, volume of rain, fog plus rain, and throughfall is recorded hourly. Stable isotope samples of rain, fog, soil water, stream water, and tree sap are collected monthly, and each site has a visibility sensor and weather station. The windward site, at 1950 m altitude, is enveloped by orographic clouds under trade wind conditions almost every day. This site is near the upper boundary of extensive forested mountain slopes that are a major watershed for the island. Volume data suggest that fog drip (compared to rain as measured by a standard gage) contributes substantially to the forest water budget on the windward side. Tree sap deuterium composition was consistently similar to fog composition for samples analyzed thus far, while soil water was isotopically lighter, possibly reflecting a mixture of fog with rain or shallow groundwater. The leeward site, at 1220 m, is often in a cloud bank under trade wind conditions. During the summer the major source of precipitation is cloud water; rainfall generally occurs during winter storms. Scattered cloud forest remnants persist at this site despite degradation of extensive native forest by ungulate browsing, plant invasion, and fire. Here, fog drip was a smaller proportion of the total precipitation than at the windward site, but exceeded rainfall for some precipitation events. Unlike the windward site, tree sap and soil water had similar isotopic composition. The information gained from this study underscores the importance of trees and shrubs in extracting cloud water that contributes to soil moisture, groundwater recharge, and stream flow in watersheds.

1,3-dichloropropene and chloropicrin emissions following simulated drip irrigation to raised beds under plastic films

USDA-ARS?s Scientific Manuscript database

Using laboratory soil chambers a non-scaled representation of an agricultural raised bed was constructed. For a sandy loam soil, a drip application of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) under both high density polyethylene (HDPE) and virtually impermeable film (VIF) was performed at 5...

Trace Phosphorus Variation in Cave Drip Water and Its Paleo-environmental Implication: A Case Study in HeShang Cave, qingjiang river, Hubei province, China

NASA Astrophysics Data System (ADS)

Yang, L. A., Jr.

2016-12-01

Trace elements demonstrate apparent seasonal variation in the lamina of speleothems in recent years, providing the possibility of studying the changing seasonality of the earth's climate in the past and attracting much extensive attention. As one of the most significant biological elements, the utilization of biology for phosphorus has a direct impact on the growth of animals and plants on the earth surface. The research revolves around standard recovery test of P drip water samples at HS4 drop site in different periods (four periods in total), and the quantitative analysis of phosphates in drip water samples of HS4 drop site within HeShang Cave, qingjiang river, Hubei province was made, recognizing the orthophosphate seasonal changes in karst system and its response to the environment of the earth's surface. The results manifest that the maximum concentration value of phosphorus in drip water samples from 2005 to 2012 is 12.1μg/L(2007-8-14), and the minimum concentration value is 0.1μg/L(2009-3-16), with the average value of 4.55μg/L. The P concentration in HeShang Cave is in accordance with the exclusively reported P data in Ernesto cave in Italy at present. The phosphorus concentration fluctuates seasonally by and large: high in summer and autumn while low in winter and spring, which has common in similar seasonal cycles with synchronous temperatures and drip water rates, also conforming to local temperature and precipitation changes. Plant productivity (determines the organic quality supplied to soil), microbiological effects (relate to temperature and humidity) and underground water permeability (relate to the precipitation and surrounding rock structure) can have an impact on the concentration of phosphorus in drip water. In winter and spring, organic phosphorus decomposition is slow and the phosphorus entering into the karst water is less as low temperature and less rainfall and weak biological process influence, resulting in the phosphorus concentration in drip water is low. With summer's approaching, temperatures rise and precipitations increase, and biological effects enhance, which cause a distinct elevation of the concentration of phosphorus. The value of phosphorus concentration reaches the peak since the turn of the summer - autumn.

Effect of age and rainfall pH on contaminant yields from metal roofs.

PubMed

Wicke, Daniel; Cochrane, Thomas A; O'Sullivan, Aisling D; Cave, Simon; Derksen, Mark

2014-01-01

Metal roofs are recognized for conveying significant metal loads to urban streams through stormwater runoff. Metal concentrations in urban runoff depend on roof types and prevailing weather conditions but the combined effects of roof age and rainfall pH on metal mobilization are not well understood. To investigate these effects on roof runoff, water quality was analysed from galvanized iron and copper roofs following rainfall events and also from simulating runoff using a rainfall simulator on specially constructed roof modules. Zinc and copper yields under different pH regimes were investigated for two roof materials and two different ages. Metal mobilization from older roofs was greater than new roofs with 55-year-old galvanized roof surfaces yielding more Zn, on average increasing by 45% and 30% under a rainfall pH of 4 and 8, respectively. Predominantly dissolved (85-95%) Zn and Cu concentrations in runoff exponentially increased as the rainfall pH decreased. Results also confirmed that copper guttering and downpipes associated with galvanized steel roof systems can substantially increase copper levels in roof runoff. Understanding the dynamics of roof surfaces as a function of weathering and rainfall pH regimes can help developers with making better choices about roof types and materials for stormwater improvement.

Impact and sustainability of low-head drip irrigation kits, in the semi-arid Gwanda and Beitbridge Districts, Mzingwane Catchment, Limpopo Basin, Zimbabwe

NASA Astrophysics Data System (ADS)

Moyo, Richard; Love, David; Mul, Marloes; Mupangwa, Walter; Twomlow, Steve

Resource-poor smallholder farmers in the semi-arid Gwanda and Beitbridge districts face food insecurity on an annual basis due to a combination of poor and erratic rainfall (average 500 mm/a and 345 mm/a, respectively, for the period 1970-2003) and technologies inappropriate to their resource status. This impacts on both household livelihoods and food security. In an attempt to improve food security in the catchment a number of drip kit distribution programmes have been initiated since 2003 as part of an on-going global initiative aimed at 2 million poor households per year. A number of recent studies have assessed the technical performance of the drip kits in-lab and in-field. In early 2005 a study was undertaken to assess the impacts and sustainability of the drip kit programme. Representatives of the NGOs, local government, traditional leadership and agricultural extension officers were interviewed. Focus group discussions with beneficiaries and other villagers were held at village level. A survey of 114 households was then conducted in two districts, using a questionnaire developed from the output of the interviews and focus group discussions. The results from the study showed that the NGOs did not specifically target the distribution of the drip kits to poor members of the community (defined for the purpose of the study as those not owning cattle). Poor households made up 54% of the beneficiaries. This poor targeting of vulnerable households could have been a result of conditions set by some implementing NGOs that beneficiaries must have an assured water source. On the other hand, only 2% of the beneficiaries had used the kit to produce the expected 5 harvests over the 2 years, owing to problems related to water shortage, access to water and also pests and diseases. About 51% of the respondents had produced at least 3 harvests and 86% produced at least 2 harvests. Due to water shortages during the dry season 61% of production with the drip kit occurred during the wet season. This suggests that most households use the drip kits as supplementary irrigation. Conflicts between beneficiaries and water point committees or other water users developed in some areas especially during the dry season. The main finding from this study was that low cost drip kit programs can only be a sustainable intervention if implemented as an integral part of a long-term development program, not short-term relief programs and the programme should involve a broad range of stakeholders. A first step in any such program, especially in water scarce areas such as Gwanda and Beitbridge, is a detailed analysis of the existing water resources to assess availability and potential conflicts, prior to distribution of drip kits.

Automated Irrigation System for Greenhouse Monitoring

NASA Astrophysics Data System (ADS)

Sivagami, A.; Hareeshvare, U.; Maheshwar, S.; Venkatachalapathy, V. S. K.

2018-06-01

The continuous requirement for the food needs the rapid improvement in food production technology. The economy of food production is mainly dependent on agriculture and the weather conditions, which are isotropic and thus we are not able to utilize the whole agricultural resources. The main reason is the deficiency of rainfall and paucity in land reservoir water. The continuous withdrawal water from the ground reduces the water level resulting in most of the land to come under the arid. In the field of cultivation, use of appropriate method of irrigation plays a vital role. Drip irrigation is a renowned methodology which is very economical and proficient. When the conventional drip irrigation system is followed, the farmer has to tag along the irrigation timetable, which is different for diverse crops. The current work makes the drip irrigation system an automated one, thereby the farmer doesn't want to follow any timetable since the sensor senses the soil moisture content and based on it supplies the water. Moreover the practice of economical sensors and the simple circuitry makes this project as an inexpensive product, which can be bought even by an underprivileged farmer. The current project is best suited for places where water is limited and has to be used in limited quantity.

Automated Irrigation System for Greenhouse Monitoring

NASA Astrophysics Data System (ADS)

Sivagami, A.; Hareeshvare, U.; Maheshwar, S.; Venkatachalapathy, V. S. K.

2018-03-01

The continuous requirement for the food needs the rapid improvement in food production technology. The economy of food production is mainly dependent on agriculture and the weather conditions, which are isotropic and thus we are not able to utilize the whole agricultural resources. The main reason is the deficiency of rainfall and paucity in land reservoir water. The continuous withdrawal water from the ground reduces the water level resulting in most of the land to come under the arid. In the field of cultivation, use of appropriate method of irrigation plays a vital role. Drip irrigation is a renowned methodology which is very economical and proficient. When the conventional drip irrigation system is followed, the farmer has to tag along the irrigation timetable, which is different for diverse crops. The current work makes the drip irrigation system an automated one, thereby the farmer doesn't want to follow any timetable since the sensor senses the soil moisture content and based on it supplies the water. Moreover the practice of economical sensors and the simple circuitry makes this project as an inexpensive product, which can be bought even by an underprivileged farmer. The current project is best suited for places where water is limited and has to be used in limited quantity.

Using Conditional Analysis to Investigate Spatial and Temporal patterns in Upland Rainfall

NASA Astrophysics Data System (ADS)

Sakamoto Ferranti, Emma Jayne; Whyatt, James Duncan; Timmis, Roger James

2010-05-01

The seasonality and characteristics of rainfall in the UK are altering under a changing climate. Summer rainfall is generally decreasing whereas winter rainfall is increasing, particularly in northern and western areas (Maraun et al., 2008) and recent research suggests these rainfall increases are amplified in upland areas (Burt and Ferranti, 2010). Conditional analysis has been used to investigate these rainfall patterns in Cumbria, an upland area in northwest England. Cumbria was selected as an example of a topographically diverse mid-latitude region that has a predominately maritime and westerly-defined climate. Moreover it has a dense network of more than 400 rain gauges that have operated for periods between 1900 and present day. Cumbria has experienced unprecedented flooding in the past decade and understanding the spatial and temporal changes in this and other upland regions is important for water resource and ecosystem management. The conditional analysis method examines the spatial and temporal variations in rainfall under different synoptic conditions and in different geographic sub-regions (Ferranti et al., 2009). A daily synoptic typing scheme, the Lamb Weather Catalogue, was applied to classify rainfall into different weather types, for example: south-westerly, westerly, easterly or cyclonic. Topographic descriptors developed using GIS were used to classify rain gauges into 6 directionally-dependant geographic sub-regions: coastal, windward-lowland, windward-upland, leeward-upland, leeward-lowland, secondary upland. Combining these classification methods enabled seasonal rainfall climatologies to be produced for specific weather types and sub-regions. Winter rainfall climatologies were constructed for all 6 sub-regions for 3 weather types - south-westerly (SW), westerly (W), and cyclonic (C); these weather types contribute more than 50% of total winter rainfall. The frequency of wet-days (>0.3mm), the total winter rainfall and the average wet day rainfall amount were analysed for each rainfall sub-region and weather type from 1961-2007 (Ferranti et al., 2010). The conditional analysis showed total rainfall under SW and W weather types to be increasing, with the greatest increases observed in the upland sub-regions. The increase in total SW rainfall is driven by a greater occurrence of SW rain days, and there has been little change to the average wet-day rainfall amount. The increase in total W rainfall is driven in part by an increase in the frequency of wet-days, but more significantly by an increase in the average wet-day rainfall amount. In contrast, total rainfall under C weather types has decreased. Further analysis will investigate how spring, summer and autumn rainfall climatologies have changed for the different weather types and sub-regions. Conditional analysis that combines GIS and synoptic climatology provides greater insights into the processes underlying readily available meteorological data. Dissecting Cumbrian rainfall data under different synoptic and geographic conditions showed the observed changes in winter rainfall are not uniform for the different weather types, nor for the different geographic sub-regions. These intricate details are often lost during coarser resolution analysis, and conditional analysis will provide a detailed synopsis of Cumbrian rainfall processes against which Regional Climate Model (RCM) performance can be tested. Conventionally RCMs try to simulate composite rainfall over many different weather types and sub-regions and by undertaking conditional validation the model performance for individual processes can be tested. This will help to target improvements in model performance, and ultimately lead to better simulation of rainfall in areas of complex topography. BURT, T. P. & FERRANTI, E. J. S. (2010) Changing patterns of heavy rainfall in upland areas: a case study from northern England. Atmospheric Environment, [in review]. FERRANTI, E. J. S., WHYATT, J. D. & TIMMIS, R. J. (2009) Development and application of topographic descriptors for conditional analysis of rainfall. Atmospheric Science Letters, 10, 177-184. FERRANTI, E. J. S., WHYATT, J. D., TIMMIS, R. J. & DAVIES, G. (2010) Using GIS to investigate spatial and temporal variations in upland rainfall. Transactions in GIS, [in press]. MARAUN, D., OSBORN, T. J. & GILLETT, N. P. (2008) United Kingdom daily precipitation intensity: improved early data, error estimates and an update from 2000 to 2006. International Journal of Climatology, 28, 833-842.

Testing the Validity of Local Flux Laws in an Experimental Eroding Landscape

NASA Astrophysics Data System (ADS)

Sweeney, K. E.; Roering, J. J.; Ellis, C.

2015-12-01

Linking sediment transport to landscape evolution is fundamental to interpreting climate and tectonic signals from topography and sedimentary deposits. Most geomorphic process laws consist of simple continuum relationships between sediment flux and local topography. However, recent work has shown that nonlocal formulations, whereby sediment flux depends on upslope conditions, are more accurate descriptions of sediment motion, particularly in steep topography. Discriminating between local and nonlocal processes in natural landscapes is complicated by the scarcity of high-resolution topographic data and by the difficulty of measuring sediment flux. To test the validity of local formulations of sediment transport, we use an experimental erosive landscape that combines disturbance-driven, diffusive sediment transport and surface runoff. We conducted our experiments in the eXperimental Landscape Model at St. Anthony Falls Laboratory a 0.5 x 0.5 m test flume filled with crystalline silica (D50 = 30μ) mixed with water to increase cohesion and preclude surface infiltration. Topography is measured with a sheet laser scanner; total sediment flux is tracked with a series of load cells. We simulate uplift (relative baselevel fall) by dropping two parallel weirs at the edges of the experiment. Diffusive sediment transport in our experiments is driven by rainsplash from a constant head drip tank fitted with 625 blunt needles of fixed diameter; sediment is mobilized both through drop impact and the subsequent runoff of the drops. To drive advective transport, we produce surface runoff via a ring of misters that produce droplets that are too small to disturb the sediment surface on impact. Using the results from five experiments that systematically vary the time of drip box rainfall relative to misting rainfall, we calculate local erosion in our experiments by differencing successive time-slices of topography and test whether these patterns are related to local topographic metrics. By examining these patterns over different timescales, we are able to assess whether there is a signature of nonlocal transport in long-term topographic evolution or if, instead, local formulations are appropriate over timescales much greater than individual transport events.

Mechanical Stimulation by Postnasal Drip Evokes Cough

PubMed Central

Iwata, Toshiyuki; Ito, Isao; Niimi, Akio; Ikegami, Koji; Marumo, Satoshi; Tanabe, Naoya; Nakaji, Hitoshi; Kanemitsu, Yoshihiro; Matsumoto, Hisako; Kamei, Junzo; Setou, Mitsutoshi; Mishima, Michiaki

2015-01-01

Cough affects all individuals at different times, and its economic burden is substantial. Despite these widespread adverse effects, cough research relies on animal models, which hampers our understanding of the fundamental cause of cough. Postnasal drip is speculated to be one of the most frequent causes of chronic cough; however, this is a matter of debate. Here we show that mechanical stimuli by postnasal drip cause chronic cough. We distinguished human cough from sneezes and expiration reflexes by airflow patterns. Cough and sneeze exhibited one-peak and two-peak patterns, respectively, in expiratory airflow, which were also confirmed by animal models of cough and sneeze. Transgenic mice with ciliary dyskinesia coughed substantially and showed postnasal drip in the pharynx; furthermore, their cough was completely inhibited by nasal airway blockade of postnasal drip. We successfully reproduced cough observed in these mice by injecting artificial postnasal drip in wild-type mice. These results demonstrated that mechanical stimulation by postnasal drip evoked cough. The findings of our study can therefore be used to develop new antitussive drugs that prevent the root cause of cough. PMID:26581078

An Evaluation of WRF Microphysics Schemes for Simulating the Warm-Type Heavy Rain over the Korean Peninsula

NASA Astrophysics Data System (ADS)

Song, Hwan-Jin; Sohn, Byung-Ju

2018-05-01

The Korean peninsula is the region of distinctly showing the heavy rain associated with relatively low storm height and small ice water content in the upper part of cloud system (i.e., so-called warm-type heavy rainfall). The satellite observations for the warm-type rain over Korea led to a conjecture that the cloud microphysics parameterization suitable for the continental deep convection may not work well for the warm-type heavy rainfall over the Korean peninsula. Therefore, there is a growing need to examine the performance of cloud microphysics schemes for simulating the warm-type heavy rain structures over the Korean peninsula. This study aims to evaluate the capabilities of eight microphysics schemes in the Weather Research and Forecasting (WRF) model how warm-type heavy rain structures can be simulated, in reference to the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) reflectivity measurements. The results indicate that the WRF Double Moment 6-class (WDM6) scheme simulated best the vertical structure of warm-type heavy rain by virtue of a reasonable collision-coalescence process between liquid droplets and the smallest amount of snow. Nonetheless the WDM6 scheme appears to have limitations that need to be improved upon for a realistic reflectivity structure, in terms of the reflectivity slope below the melting layer, discontinuity in reflectivity profiles around the melting layer, and overestimation of upper-level reflectivity due to high graupel content.

How is rainfall interception in urban area affected by meteorological parameters?

NASA Astrophysics Data System (ADS)

Zabret, Katarina; Rakovec, Jože; Mikoš, Matjaž; Šraj, Mojca

2017-04-01

Rainfall interception is part of the hydrological cycle. Precipitation, which hits vegetation, is retained on the leaves and branches, from which it eventually evaporates into the atmosphere (interception) or reaches the ground by dripping from the canopy, falling through the gaps (throughfall) and running down the stems (stemflow). The amount of rainfall reaching the ground depends on various meteorological and vegetation parameters. Rainfall, throughfall and stemflow have been measured in the city of Ljubljana, Slovenia since the beginning of 2014. Manual and automatic measurements are performed regularly under Betula pendula and Pinus nigra trees in urban area. In 2014, there were detected 178 rainfall events with total amount of 1672.1 mm. In average B. pendula intercepted 44% of rainfall and P. nigra intercepted 72% of rainfall. In 2015 we have detected 117 events with 1047.4 mm of rainfall, of which 37% was intercepted by B. pendula and 60% by P. nigra. The effect of various meteorological parameters on the rainfall interception was analysed in the study. The parameters included in the analysis were rainfall rate, rainfall duration, drop size distribution (average drop velocity and diameter), average wind speed, and average temperature. The results demonstrate decreasing rainfall interception with longer rainfall duration and higher rainfall intensity although the impact of the latter one is not statistically significant. In the case of very fast or very slow rainfall drops, the interception is higher than for the mean rain drop velocity values. In the case of P. nigra the impact of the rain drop diameter on interception is similar to the one of rain drop velocity while for B. pendula increasing of drop diameter also increases the interception. As expected, interception is higher for warmer events. This trend is more evident for P. nigra than for B. pendula. Furthermore, the amount of intercepted rainfall also increases with wind although it could be relatively high in case of very low wind speeds.

Effects of soil type on leaching and runoff transport of rare earth elements and phosphorous in laboratory experiments.

PubMed

Wang, Lingqing; Liang, Tao; Chong, Zhongyi; Zhang, Chaosheng

2011-01-01

Through leaching experiments and simulated rainfall experiments, characteristics of vertical leaching of exogenous rare earth elements (REEs) and phosphorus (P) and their losses with surface runoff during simulated rainfall in different types of soils (terra nera soil, cinnamon soil, red soil, loess soil, and purple soil) were investigated. Results of the leaching experiments showed that vertical transports of REEs and P were relatively low, with transport depths less than 6 cm. The vertical leaching rates of REEs and P in the different soils followed the order of purple soil > terra nera soil > red soil > cinnamon soil > loess soil. Results of the simulated rainfall experiments (83 mm h⁻¹) revealed that more than 92% of REEs and P transported with soil particles in runoff. The loss rates of REEs and P in surface runoff in the different soil types were in the order of loess soil > terra nera soil > cinnamon soil > red soil > purple soil. The total amounts of losses of REEs and P in runoff were significantly correlated.

[Estimation of urban non-point source pollution loading and its factor analysis in the Pearl River Delta].

PubMed

Liao, Yi-Shan; Zhuo, Mu-Ning; Li, Ding-Qiang; Guo, Tai-Long

2013-08-01

In the Pearl Delta region, urban rivers have been seriously polluted, and the input of non-point source pollution materials, such as chemical oxygen demand (COD), into rivers cannot be neglected. During 2009-2010, the water qualities at eight different catchments in the Fenjiang River of Foshan city were monitored, and the COD loads for eight rivulet sewages were calculated in respect of different rainfall conditions. Interesting results were concluded in our paper. The rainfall and landuse type played important roles in the COD loading, with greater influence of rainfall than landuse type. Consequently, a COD loading formula was constructed that was defined as a function of runoff and landuse type that were derived SCS model and land use map. Loading of COD could be evaluated and predicted with the constructed formula. The mean simulation accuracy for single rainfall event was 75.51%. Long-term simulation accuracy was better than that of single rainfall. In 2009, the estimated COD loading and its loading intensity were 8 053 t and 339 kg x (hm2 x a)(-1), and the industrial land was regarded as the main source of COD pollution area. The severe non-point source pollution such as COD in Fenjiang River must be paid more attention in the future.

Monitoring of cave air temperature and humidity in the Niedźwiedzia Cave system (Sudetes, Poland) - a key to understanding tourists activity impact to cave environment

NASA Astrophysics Data System (ADS)

Gasiorowski, M.; Hercman, H.

2012-04-01

The Niedźwiedzia Cave is located in Śnieżnik Massif (the Easter Sudetes, SW Poland) at 800 m a.s.l. The length of known passages is ~3000 m and denivelation is 69 m. The system is composed of 3 levels of passages and chambers. It is a show cave with ~80,000 visitors every year. In 2010 we started monitoring program of cave air temperature and humidity, drip rate, stable isotopes and Uranium and Polonium content in water in selected sites inside the cave and in its vicinity. Changes in dropping rate in upper level are well correlated with precipitation. However, a response of dripping to rainfall depends on former precipitation frequency and intensity - during the humid period the dripping reacts immediately and after long dry period dripping responses with two-weeks delay. There is not so direct correlation between precipitation and dripping in lower level of the system. Air temperature inside the cave is almost stable in lower level (mean annual ~5.3 °C, and annual variation up to 0.7 °C) and more dynamic in the middle level (mean annual ~6.4 °C, and mean annual amplitude up to 4 °C). Daily and weekly measured changes of cave air temperature demonstrate extremely well correlation with number of visitors. In show cave passages (the middle level of the system) temperature increase 0.1-0.2 °C during every day when the cave is open for tourists and such changes is not observed during days without visitors and in lower level of the system closed for tourists. But even short visits of 3-4 cavers are recorded by temperature sensors exposed in the lower level (~0.02 °C increase). It proves very high sensitivity of cave environment to human activity. This study is funded by the National Science Centre and Higher Education grant no. N N306 131038.

Study on Hydrological Functions of Litter Layers in North China

PubMed Central

Li, Xiang; Niu, Jianzhi; Xie, Baoyuan

2013-01-01

Canopy interception, throughfall, stemflow, and runoff have received considerable attention during the study of water balance and hydrological processes in forested ecosystems. Past research has either neglected or underestimated the role of hydrological functions of litter layers, although some studies have considered the impact of various characteristics of rainfall and litter on litter interception. Based on both simulated rainfall and litter conditions in North China, the effect of litter mass, rainfall intensity and litter type on the maximum water storage capacity of litter (S) and litter interception storage capacity (C) were investigated under five simulated rainfall intensities and four litter masses for two litter types. The results indicated: 1) the S values increased linearly with litter mass, and the S values of broadleaf litter were on average 2.65 times larger than the S values of needle leaf litter; 2) rainfall intensity rather than litter mass determined the maximum interception storage capacity (Cmax); Cmax increased linearly with increasing rainfall intensity; by contrast, the minimum interception storage capacity (Cmin) showed a linear relationship with litter mass, but a poor correlation with rainfall intensity; 3) litter type impacted Cmax and Cmin; the values of Cmax and Cmin for broadleaf litter were larger than those of needle leaf litter, which indicated that broadleaf litter could intercepte and store more water than needle leaf litter; 4) a gap existed between Cmax and Cmin, indicating that litter played a significant role by allowing rainwater to infiltrate or to produce runoff rather than intercepting it and allowing it to evaporate after the rainfall event; 5) Cmin was always less than S at the same litter mass, which should be considered in future interception predictions. Vegetation and precipitation characteristics played important roles in hydrological characteristics. PMID:23936188

Assessing the impact of climate change on flood types in the Austrian and French Alps using the stochastic weather generator TripleM and rainfall-runoff modeling

NASA Astrophysics Data System (ADS)

Breinl, Korbinian; Turkington, Thea

2017-04-01

We developed a new methodology for classifying flood types, which appears to be particularly suitable for climate change impact studies. Climate change is not only expected to change the magnitude and frequency of Alpine floods but also the types of floods. The distribution of existing flood types may change and new flood types may develop. A shift away from solely focusing on the magnitude and frequency of floods in flood hazard assessment and disaster risk management towards the causal types of floods is required as the types and therefore also timing and characteristics of floods will have implications on both the local social and ecological systems. The flood types are classified using k-means clustering of temperature and precipitation indicators, capturing differences in rainfall amounts, antecedent rainfall, snow-cover, and the day of the year. In a first step, we used the open-source multi-site weather generator TripleM coupled with the fast conceptual rainfall-runoff model HBV to extrapolate the observed discharge time series and generate a large inventory of different types of observed flood events and flood types. The weather generator was then parameterized based on projections of rainfall and temperature to simulate future flood types and events. We selected four climate projections (mild dry, mild wet, warm dry and warm wet conditions) from a set of 15, which originated from the EURO-CORDEX dataset. We worked in two catchments in the Austrian and French Alps that have been affected by floods in the past: the medium-sized Salzach catchment in Austria, which is dominated by rainfall driven flooding during the summer and autumn period, and the small Ubaye catchment in the Southern French Alps, which is dominated by rain-on-snow floods in the spring period. The analysis of the simulated future flood types shows clear changes in the distribution and characteristics of flood types in both study areas under the different climate projections examined.

The significance of spatial variability of rainfall on streamflow: A synthetic analysis at the Upper Lee catchment, UK

NASA Astrophysics Data System (ADS)

Pechlivanidis, Ilias; McIntyre, Neil; Wheater, Howard

2017-04-01

Rainfall, one of the main inputs in hydrological modeling, is a highly heterogeneous process over a wide range of scales in space, and hence the ignorance of the spatial rainfall information could affect the simulated streamflow. Calibration of hydrological model parameters is rarely a straightforward task due to parameter equifinality and parameters' 'nature' to compensate for other uncertainties, i.e. structural and forcing input. In here, we analyse the significance of spatial variability of rainfall on streamflow as a function of catchment scale and type, and antecedent conditions using the continuous time, semi-distributed PDM hydrological model at the Upper Lee catchment, UK. The impact of catchment scale and type is assessed using 11 nested catchments ranging in scale from 25 to 1040 km2, and further assessed by artificially changing the catchment characteristics and translating these to model parameters with uncertainty using model regionalisation. Synthetic rainfall events are introduced to directly relate the change in simulated streamflow to the spatial variability of rainfall. Overall, we conclude that the antecedent catchment wetness and catchment type play an important role in controlling the significance of the spatial distribution of rainfall on streamflow. Results show a relationship between hydrograph characteristics (streamflow peak and volume) and the degree of spatial variability of rainfall for the impermeable catchments under dry antecedent conditions, although this decreases at larger scales; however this sensitivity is significantly undermined under wet antecedent conditions. Although there is indication that the impact of spatial rainfall on streamflow varies as a function of catchment scale, the variability of antecedent conditions between the synthetic catchments seems to mask this significance. Finally, hydrograph responses to different spatial patterns in rainfall depend on assumptions used for model parameter estimation and also the spatial variation in parameters indicating the need of an uncertainty framework in such investigation.

Medication and volume delivery by gravity-driven micro-drip intravenous infusion: potential variations during "wide-open" flow.

PubMed

Pierce, Eric T; Kumar, Vikram; Zheng, Hui; Peterfreund, Robert A

2013-03-01

Gravity-driven micro-drip infusion sets allow control of medication dose delivery by adjusting drops per minute. When the roller clamp is fully open, flow in the drip chamber can be a continuous fluid column rather than discrete, countable, drops. We hypothesized that during this "wide-open" state, drug delivery becomes dependent on factors extrinsic to the micro-drip set and is therefore difficult to predict. We conducted laboratory experiments to characterize volume delivery under various clinically relevant conditions of wide-open flow in an in vitro laboratory model. A micro-drip infusion set, plugged into a bag of normal saline, was connected to a high-flow stopcock at the distal end. Vertically oriented IV catheters (gauges 14-22) were connected to the stopcock. The fluid meniscus height in the bag was fixed (60-120 cm) above the outflow point. The roller clamp on the infusion set was in fully open position for all experiments resulting in a continuous column of fluid in the drip chamber. Fluid volume delivered in 1 minute was measured 4 times with each condition. To model resistive effects of carrier flow, volumetric infusion pumps were used to deliver various flow rates of normal saline through a carrier IV set into which a micro-drip infusion was "piggybacked." We also compared delivery by micro-drip infusion sets from 3 manufacturers. The volume of fluid delivered by gravity-driven infusion under wide-open conditions (continuous fluid column in drip chamber) varied 2.9-fold (95% confidence interval, 2.84-2.96) depending on catheter size and fluid column height. Total model resistance of the micro-drip with stopcock and catheter varied with flow rate. Volume delivered by the piggybacked micro-drip decreased up to 29.7% ± 0.8% (mean ± SE) as the carrier flow increased from 0 to 1998 mL/min. Delivery characteristics of the micro-drip infusion sets from 3 different manufacturers were similar. Laboratory simulation of clinical situations with gravity-driven micro-drip infusion sets under wide-open flow conditions revealed that infusion rate (drug and/or volume delivery) can vary widely depending on extrinsic factors including catheter size, fluid column height, and carrier flow. The variable resistance implies nonlaminar flow in the micro-drip model that cannot be easily predicted mathematically. These findings support the use of mechanical pumps instead of gravity-driven micro-drips to enhance the precision and safety of IV infusions, especially for vasoactive drugs.

Gauging Through the Crowd: A Crowd-Sourcing Approach to Urban Rainfall Measurement and Storm Water Modeling Implications

NASA Astrophysics Data System (ADS)

Yang, Pan; Ng, Tze Ling

2017-11-01

Accurate rainfall measurement at high spatial and temporal resolutions is critical for the modeling and management of urban storm water. In this study, we conduct computer simulation experiments to test the potential of a crowd-sourcing approach, where smartphones, surveillance cameras, and other devices act as precipitation sensors, as an alternative to the traditional approach of using rain gauges to monitor urban rainfall. The crowd-sourcing approach is promising as it has the potential to provide high-density measurements, albeit with relatively large individual errors. We explore the potential of this approach for urban rainfall monitoring and the subsequent implications for storm water modeling through a series of simulation experiments involving synthetically generated crowd-sourced rainfall data and a storm water model. The results show that even under conservative assumptions, crowd-sourced rainfall data lead to more accurate modeling of storm water flows as compared to rain gauge data. We observe the relative superiority of the crowd-sourcing approach to vary depending on crowd participation rate, measurement accuracy, drainage area, choice of performance statistic, and crowd-sourced observation type. A possible reason for our findings is the differences between the error structures of crowd-sourced and rain gauge rainfall fields resulting from the differences between the errors and densities of the raw measurement data underlying the two field types.

Synthetic generation of spatially high resolution extreme rainfall in Japan using Monte Carlo simulation with AMeDAS analyzed rainfall data sets

NASA Astrophysics Data System (ADS)

Haruki, W.; Iseri, Y.; Takegawa, S.; Sasaki, O.; Yoshikawa, S.; Kanae, S.

2016-12-01

Natural disasters caused by heavy rainfall occur every year in Japan. Effective countermeasures against such events are important. In 2015, a catastrophic flood occurred in Kinu river basin, which locates in the northern part of Kanto region. The remarkable feature of this flood event was not only in the intensity of rainfall but also in the spatial characteristics of heavy rainfall area. The flood was caused by continuous overlapping of heavy rainfall area over the Kinu river basin, suggesting consideration of spatial extent is quite important to assess impacts of heavy rainfall events. However, the spatial extent of heavy rainfall events cannot be properly measured through rainfall measurement by rain gauges at observation points. On the other hand, rainfall measurements by radar observations provide spatially and temporarily high resolution rainfall data which would be useful to catch the characteristics of heavy rainfall events. For long term effective countermeasure, extreme heavy rainfall scenario considering rainfall area and distribution is required. In this study, a new method for generating extreme heavy rainfall events using Monte Carlo Simulation has been developed in order to produce extreme heavy rainfall scenario. This study used AMeDAS analyzed precipitation data which is high resolution grid precipitation data made by Japan Meteorological Agency. Depth area duration (DAD) analysis has been conducted to extract extreme rainfall events in the past, considering time and spatial scale. In the Monte Carlo Simulation, extreme rainfall event is generated based on events extracted by DAD analysis. Extreme heavy rainfall events are generated in specific region in Japan and the types of generated extreme heavy rainfall events can be changed by varying the parameter. For application of this method, we focused on Kanto region in Japan. As a result, 3000 years rainfall data are generated. 100 -year probable rainfall and return period of flood in Kinu River Basin (2015) are obtained using generated data. We compared 100-year probable rainfall calculated by this method with other traditional method. New developed method enables us to generate extreme rainfall events considering time and spatial scale and produce extreme rainfall scenario.

Cloud shading and fog drip influence the metabolism of a coastal pine ecosystem.

PubMed

Carbone, Mariah S; Park Williams, A; Ambrose, Anthony R; Boot, Claudia M; Bradley, Eliza S; Dawson, Todd E; Schaeffer, Sean M; Schimel, Joshua P; Still, Christopher J

2013-02-01

Assessing the ecological importance of clouds has substantial implications for our basic understanding of ecosystems and for predicting how they will respond to a changing climate. This study was conducted in a coastal Bishop pine forest ecosystem that experiences regular cycles of stratus cloud cover and inundation in summer. Our objective was to understand how these clouds impact ecosystem metabolism by contrasting two sites along a gradient of summer stratus cover. The site that was under cloud cover ~15% more of the summer daytime hours had lower air temperatures and evaporation rates, higher soil moisture content, and received more frequent fog drip inputs than the site with less cloud cover. These cloud-driven differences in environmental conditions translated into large differences in plant and microbial activity. Pine trees at the site with greater cloud cover exhibited less water stress in summer, larger basal area growth, and greater rates of sap velocity. The difference in basal area growth between the two sites was largely due to summer growth. Microbial metabolism was highly responsive to fog drip, illustrated by an observed ~3-fold increase in microbial biomass C with increasing summer fog drip. In addition, the site with more cloud cover had greater total soil respiration and a larger fractional contribution from heterotrophic sources. We conclude that clouds are important to the ecological functioning of these coastal forests, providing summer shading and cooling that relieve pine and microbial drought stress as well as regular moisture inputs that elevate plant and microbial metabolism. These findings are important for understanding how these and other seasonally dry coastal ecosystems will respond to predicted changes in stratus cover, rainfall, and temperature. © 2012 Blackwell Publishing Ltd.

An evaluation of WRF microphysics schemes for simulating the warm-type heavy rain over the Korean peninsula

NASA Astrophysics Data System (ADS)

Song, Hwan-Jin; Sohn, Byung-Ju

2018-01-01

The Korean peninsula is the region of distinctly showing the heavy rain associated with relatively low storm height and small ice water content in the upper part of cloud system (i.e., so-called warm-type heavy rainfall). The satellite observations for the warmtype rain over Korea led to a conjecture that the cloud microphysics parameterization suitable for the continental deep convection may not work well for the warm-type heavy rainfall over the Korean peninsula. Therefore, there is a growing need to examine the performance of cloud microphysics schemes for simulating the warm-type heavy rain structures over the Korean peninsula. This study aims to evaluate the capabilities of eight microphysics schemes in the Weather Research and Forecasting (WRF) model how warmtype heavy rain structures can be simulated, in reference to the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) reflectivity measurements. The results indicate that the WRF Double Moment 6-class (WDM6) scheme simulated best the vertical structure of warm-type heavy rain by virtue of a reasonable collisioncoalescence process between liquid droplets and the smallest amount of snow. Nonetheless the WDM6 scheme appears to have limitations that need to be improved upon for a realistic reflectivity structure, in terms of the reflectivity slope below the melting layer, discontinuity in reflectivity profiles around the melting layer, and overestimation of upper-level reflectivity due to high graupel content.

Effect of Temperature, Precursor Type and Dripping Time on the Crystallite Size of Nano ZnO Obtained by One-Pot Synthesis: 2 k Full Factorial Design Analysis.

PubMed

Machado, Morgana de Medeiros; Savi, Bruna Martinello; Perucchi, Mariana Borges; Benedetti, Alessandro; Oliveira, Luis Felipe Silva; Bernardin, Adriano Michael

2018-06-01

The aim of this work was to determine the effect of temperature, precursor and dripping time on the crystallite size of ZnO nanoparticles synthesized by controlled precipitation according a 2k full factorial design. ZnCl2, Zn(NO3)2 and NaOH were used as precursors. After synthesis, the nano crystalline powder was characterized by XRD (Cu Kα), UV-Vis, and HR-TEM. The nano ZnO particles presented a crystallite size between 210 and 260 Å (HR-TEM and XRD). The results show that the crystallite size depends on the type of precursor and temperature of synthesis, but not on the dripping time.

Impact of using scatter-mimicking beams instead of standard beams to measure penetration when assessing the protective value of radiation-protective garments.

PubMed

Jones, A Kyle; Pasciak, Alexander S; Wagner, Louis K

2018-03-01

Use standardized methods to determine how assessment of protective value of radiation-protective garments changes under conditions employing standard beam qualities, scatter-mimicking primary beams, and a modified H p (10) measurement. The shielding properties of radiation-protective garments depend on the spectrum of beam energies striking the garment and the attenuation properties of materials used to construct the garment, including x-ray fluorescence produced by these materials. In this study the primary beam spectra employed during clinical interventional radiology and cardiology procedures (clinical primary beams, CPB) were identified using radiation dose structured reports (RDSR) and fluoroscope log data. Monte Carlo simulation was used to determine the scattered radiation spectra produced by these CPB during typical clinical application. For these scattered spectra, scatter-mimicking primary beams (SMPB) were determined using numerical optimization-based spectral reconstruction that adjusted kV and filtration to produce the SMPB that optimally matched the scattered spectrum for each CPB. The penetration of a subset of SMPB through four radiation-protective garments of varying compositions and nominal thicknesses was measured using a geometry specified by the International Electrotechnical Commission (IEC). The diagnostic radiological index of protection (DRIP), which increases with increasing penetration through a garment, was calculated using these measurements. Penetration through the same garments was measured for standard beams specified by the American Society of Testing and Materials (ASTM). Finally, 10 mm of PMMA was affixed to the inside of each garment and the DRIP remeasured in this configuration to simulate H p (10). The SMPB based on actual CPB were in general characterized by lower kV (range 60-76) and higher half-value layer (HVL, range 3.44-4.89 mm Al) than standard beam qualities specified by ASTM (kV range 70-85; HVL range 3.4-4.0 mm Al). A lead garment of nominal thickness 0.5 mm (D) had a DRIP of 0.8%, two lead-free garments of 0.5 mm nominal thickness had DRIPs of 1.2% (A) and 2.2% (B), and a lead-free bilayer (C) had a DRIP of 1.4%. When standard beam qualities specified by the ASTM were used, the DRIP for D was 2.2%, 175% higher than the DRIP measured using SMPB, and for A, B, and C was 2.8%, 3.2%, and 2.9%, respectively. This was 133%, 45%, and 107% higher than the DRIP measured using SMPB. Differences between the DRIP of lead-alternative garments and the lead garment were reduced when measured with 10 mm of PMMA. Using this method, the measured DRIPs were 2.2% (A), 3.1% (B), 2.5% (C), and 2.3% (D). Penetration of radiation through radiation-protective garments depended strongly on the methods and X-ray spectra used for evaluation. The DRIP was higher (i.e., protective value was lower) for lead-alternative garments than for lead garments in this evaluation. The DRIP was lower for all garments when SMPB based on actual clinical beam quality data were used to measure penetration compared to ASTM standard beams. Differences in penetration between lead-alternative and lead garments were less when the DRIP was measured with 10 mm of PMMA between the garment and the chamber. © 2018 American Association of Physicists in Medicine.

High Resolution Time Series Cave Ventilation Processes and the Effects on Cave Air Chemistry and Drip Waters: Speleoclimatology and Proxy Calibration

NASA Astrophysics Data System (ADS)

Kowalczk, A. J.; Froelich, P. N.; Gaffka, C.; Tremaine, D.

2008-12-01

Continuous high resolution (sub-hourly), long-term (Nov 2007-present) monitoring of cave air chemistry (Temperature, Relative Humidity, Barometric Pressure, Radon-222, CO2, Air flow, Wind speed and direction) in a shallow subtropical cave (Hollow Ridge) in N Florida reveals two major ventilation mechanisms: 1) ventilation driven by winds across the cave entrances, and 2) ventilation driven by density differences between atmospheric and cave air. The degree and type of ventilation strongly influence the 222Rn and CO2 of cave air, which in turn affects the timing and extent of calcite deposition in speleothems. The degree of ventilation is estimated using a cave air CO2-δ13CO2 Keeling Plot, or a simple radon deficiency model. Results show cave air has an atmospheric component ranging from 10-90%. During fall and winter, average CO2 (700 ppmv) and 222Rn (50-100 dpm/L) are lower than in spring and summer (CO2 = 1200 ppmv; 222Rn = 1000 dpm/L) due to increased winter ventilation. Decreased ventilation during the summer allows CO2 and 222Rn levels to rise. Winter daily ventilation is primarily a function of density gradients between cave air and atmospheric air, while summer daily ventilation is primarily a function of late morning NW-NE winds above the cave. Stable isotope analyses of drip water (fracture drip and pore flow drip) and aquifer water from Hollow Ridge agree with previous isotope studies of drip water at Florida Caverns State Park, 2 km to the NE. During summer, isotopic composition of pore flow drip water (δ18O -3.8 to -4.0 per mil; δD -17.3 to -20.2 per mil VSMOW) and aquifer water (δ18O -4.0 per mil; δD -18.0 to -21.1 per mil) are similar to average annual weighted isotopic composition of precipitation (δ18O -3.6 per mil) while fracture drip waters (δ18O -3 to -3.4 per mil; δD -11.9 to -14.3 per mil) likely reflect the isotopic composition of individual precipitation events. Pore flow drip waters δ18O are weakly correlated with drip rates (enriched δ18O during periods of higher drip rates) but show no correlation to precipitation amount. Knowledge of the type of drip flow is important when considering stalagmites for paleoclimate studies. A significant decrease in drip rate was observed from June (1034 drips/hour) through August 2008 (34 drips/hour). Higher water demands during summer months with increased evapotranspiration may be responsible for this decrease. A semi-diurnal drip rate cycle, negatively correlated with barometric pressure, is also observed throughout the period. This strong negative correlation is hypothesized to be controlled by atmospheric tidal oscillations. Observations into the fall and winter seasons should reveal seasonality, if any, and if there is an evapotranspiration effect present in the water cycle. High resolution studies of cave air chemistry and ventilation processes will enhance knowledge of the timing, extent, and isotopic and chemical composition of calcite deposition. When combined with drip water and precipitation isotope analyses, these studies will improve the understanding and interpretation of high- resolution (sub-annual) speleothem paleoclimate records.

Effect of water irrigation volume on Capsicum frutescens growth and plankton abundance in aquaponics system

NASA Astrophysics Data System (ADS)

Andriani, Y.; Dhahiyat, Y.; Zahidah; Subhan, U.; Iskandar; Zidni, I.; Mawardiani, T.

2018-03-01

This study aimed to understand Capsicum frutescens growth and plankton abundance in aquaponics culture. A Completely Randomized Design (CRD) with six treatments in triplicates comprising of treatment A (positive control using organic liquid fertilizer), B (negative control without fertilizer), C (drip irrigation aquaponics with a water debit of 100 ml/day/plant), D (drip irrigation aquaponics with a water debit of 150 ml/day/plant), E (drip irrigation with a water debit of 200 ml/day/plant), and F (drip irrigation aquaponics with a water debit of 250 ml/day/plant) was applied. The water used in treatments C, D, E, and F contained comet fish feces as fertilizer. C. frutescens growth and plankton abundance were observed. Analysis was conducted using analysis of variance for plant productivity and descriptive analysis for plankton abundance and water quality. The results of this study showed that the highest plant growth was seen in plants receiving F treatment with 50 ml/day drip irrigation. However, no significant difference was found when compared to the positive control with organic artificial fertilizer. Eleven types of phytoplankton and six types of zooplankton were found, with Stanieria sp. as the most abundant phytoplankton and Brachionus sp. and Epistylis sp. as the most abundant zooplanktons.

Simulation of Soil Wetting Patterns in Drip and Subsurface Irrigation. Effects in Design and Irrigation Management Variables.

NASA Astrophysics Data System (ADS)

Rodríguez-Sinobas, L.; Gil-Rodríguez, M.; Sánchez, R.; Losada, A.; Castañón, G.; Juana, L.; Laguna, F. V.; Benítez, J.

2010-05-01

Conventional drip irrigation is considered one of the most efficient irrigation systems. Alternatively to traditional surface drip irrigation systems (DI), laterals are deployed underneath the soil surface, as in subsurface drip irrigation (SDI), leading to a higher potential efficiency, which is of especial interest in places where water is a limited source. The design and management of DI and SDI systems involve selection of an appropriate combination of emitter discharge rate and spacing between emitters and the inlet pressure and irrigation time for any given set of soil, crop, and climatic conditions, as well as understanding the wetted zone pattern around the emitter. Likewise, water distribution is affected by soil hydraulic properties, initial water content, emitter discharge, irrigation frequency, evapotranspiration and root characteristics. However, complexity arousing of soil water properties and soil profile characteristics means that these are often not properly considered in the design and management of those systems. A better understanding of the infiltration process around the discharge point source should contribute to increase water use efficiency and thus to reduce the risk of environmental impact of irrigation. In this regard, numerical models have been proved to be a powerful tool to analyze the evolution of the wetting pattern during the distribution and redistribution processes, in order to explore irrigation management strategies, to set up the duration of irrigation, and finally to optimize water use efficiency. Also, irrigation design variables such as emitter spacing and discharge could also be assessed. In this study the suitability of the HYDRUS-2D to simulate infiltration process around an emitter during irrigation of a loamy soil with drip and SDI laterals has been addressed. The model was then applied in order to evaluate the main dimensions of the wetted soil volume surrounding the emitter during irrigation. Irrigation uniformity with DI and SDI laterals were determined by field evaluations at different inlet head pressures. Results were related with estimations made on water distribution within the soil that were simulated taking into account the emitter discharge at different lateral locations, initial soil water content, soil hydraulic properties and time of irrigation. Conclusions highlight the effect of emitter discharge, emitter spacing, and irrigation time on wetting patterns, and thus solute transport, in both drip and subsurface drip irrigation. The effect of emitter depth was also considered in SDI. Some recommendations for the design and management of these irrigation systems are also provided.

Future irrigation expansion outweigh groundwater recharge gains from climate change in semi-arid India.

PubMed

Sishodia, Rajendra P; Shukla, Sanjay; Wani, Suhas P; Graham, Wendy D; Jones, James W

2018-09-01

Simultaneous effects of future climate and irrigation intensification on surface and groundwater systems are not well understood. Efforts are needed to understand the future groundwater availability and associated surface flows under business-as-usual management to formulate policy changes to improve water sustainability. We combine measurements with integrated modeling (MIKE SHE/MIKE11) to evaluate the effects of future climate (2040-2069), with and without irrigation expansion, on water levels and flows in an agricultural watershed in low-storage crystalline aquifer region of south India. Demand and supply management changes, including improved efficiency of irrigation water as well as energy uses, were evaluated. Increased future rainfall (7-43%, from 5 Global Climate Models) with no further expansion of irrigation wells increased the groundwater recharge (10-55%); however, most of the recharge moved out of watershed as increased baseflow (17-154%) with a small increase in net recharge (+0.2mm/year). When increased rainfall was considered with projected increase in irrigation withdrawals, both hydrologic extremes of well drying and flooding were predicted. A 100-year flow event was predicted to be a 5-year event in the future. If irrigation expansion follows the historical trends, earlier and more frequent well drying, a source of farmers' distress in India, was predicted to worsen in the future despite the recharge gains from increased rainfall. Storage and use of excess flows, improved irrigation efficiency with flood to drip conversion in 25% of irrigated area, and reduced energy subsidy (free electricity for 3.5h compared to 7h/day; $1 billion savings) provided sufficient water savings to support future expansion in irrigated areas while mitigating well drying as well as flooding. Reductions in energy subsidy to fund the implementation of economically desirable (high benefit-cost ratio) demand (drip irrigation) and supply (water capture and storage) management was recommended to achieve a sustainable food-water-energy nexus in semi-arid regions. Copyright © 2018 Elsevier B.V. All rights reserved.

Rainfall height stochastic modelling as a support tool for landslides early warning

NASA Astrophysics Data System (ADS)

Capparelli, G.; Giorgio, M.; Greco, R.; Versace, P.

2009-04-01

Occurrence of landslides is uneasy to predict, since it is affected by a number of variables, such as mechanical and hydraulic soil properties, slope morphology, vegetation coverage, rainfall spatial and temporal variability. Although heavy landslides frequently occurred in Campania, southern Italy, during the last decade, no complete data sets are available for natural slopes where landslides occurred. As a consequence, landslide risk assessment procedures and early warning systems in Campania still rely on simple empirical models based on correlation between daily rainfall records and observed landslides, like FLAIR model [Versace et al., 2003]. Effectiveness of such systems could be improved by reliable quantitative rainfall prediction. In mountainous areas, rainfall spatial and temporal variability are very pronounced due to orographic effects, making predictions even more complicated. Existing rain gauge networks are not dense enough to resolve the small scale spatial variability, and the same limitation of spatial resolution affects rainfall height maps provided by radar sensors as well as by meteorological physically based models. Therefore, analysis of on-site recorded rainfall height time series still represents the most effective approach for a reliable prediction of local temporal evolution of rainfall. Hydrological time series analysis is a widely studied field in hydrology, often carried out by means of autoregressive models, such as AR and ARMA [Box and Jenkins, 1976]. Sometimes exogenous information coming from additional series of observations is also taken into account, and the models are called ARX and ARMAX (e.g. Salas [1992]). Such models gave the best results when applied to the analysis of autocorrelated hydrological time series, like river flow or level time series. Conversely, they are not able to model the behaviour of intermittent time series, like point rainfall height series usually are, especially when recorded with short sampling time intervals. More useful for this issue are the so-called DRIP (Disaggregated Rectangular Intensity Pulse) and NSRP (Neymann-Scott Rectangular Pulse) model [Heneker et al., 2001; Cowpertwait et al., 2002], usually adopted to generate synthetic point rainfall series. In this paper, the DRIP model approach is adopted in conjunction with FLAIR model to calculate the probability of flowslides occurrence. The final aim of the study is in fact to provide a useful tool to implement an early warning system for hydrogeological risk management. Model calibration has been carried out with hourly rainfall hieght data provided by the rain gauges of Campania Region civil protection agency meteorological warning network. So far, the model has been applied only to data series recorded at a single rain gauge. Future extension will deal with spatial correlation between time series recorded at different gauges. ACKNOWLEDGEMENTS The research was co-financed by the Italian Ministry of University, by means of the PRIN 2006 PRIN program, within the research project entitled ‘Definition of critical rainfall thresholds for destructive landslides for civil protection purposes'. REFERENCES Box, G.E.P. and Jenkins, G.M., 1976. Time Series Analysis Forecasting and Control, Holden-Day, San Francisco. Cowpertwait, P.S.P., Kilsby, C.G. and O'Connell, P.E., 2002. A space-time Neyman-Scott model of rainfall: Empirical analysis of extremes, Water Resources Research, 38(8):1-14. Salas, J.D., 1992. Analysis and modeling of hydrological time series, in D.R. Maidment, ed., Handbook of Hydrology, McGraw-Hill, New York. Heneker, T.M., Lambert, M.F. and Kuczera G., 2001. A point rainfall model for risk-based design, Journal of Hydrology, 247(1-2):54-71. Versace, P., Sirangelo. B. and Capparelli, G., 2003. Forewarning model of landslides triggered by rainfall. Proc. 3rd International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction and Assessment, Davos.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, A; Pasciak, A; Wagner, L

Purpose: To evaluate the sensitivity of the Diagnostic Radiological Index of Protection (DRIP) to procedural factors in fluoroscopy in an effort to determine an appropriate set of scatter-mimicking primary beams (SMPB) to be used in measuring the DRIP. Methods: A series of clinical and factorial Monte Carlo simulations were conducted to determine the shape of the scattered X-ray spectra incident on the operator in different clinical fluoroscopy scenarios. Two clinical evaluations studied the sensitivity of the scattered spectrum to gantry angle and patient size while technical factors were varied according to measured automatic dose rate control (ADRC) data. Factorial evaluationsmore » studied the sensitivity of the scattered spectrum to gantry angle, field of view, patient size and beam quality for constant technical factors. Average energy was the figure of merit used to condense fluence in each energy bin to a single numerical index. Results: Beam quality had the strongest influence on the scattered spectrum in fluoroscopy. Many procedural factors affected the scattered spectrum indirectly through their effects on primary beam quality through ADRC, e.g., gantry angle and patient size. Lateral C-arm rotation, common in interventional cardiology, increased the energy of the scattered spectrum, regardless of the direction of rotation. The effect of patient size on scattered radiation depended on ADRC characteristics, patient size, and procedure type. Conclusion: The scattered spectrum striking the operator in fluoroscopy, and therefore the DRIP, is most strongly influenced by primary beam quality, particularly kV. Use cases for protective garments should be classified by typical procedural primary beam qualities, which are governed by the ADRC according to the impacts of patient size, anatomical location, and gantry angle. These results will help determine an appropriate set of SMPB to be used for measuring the DRIP.« less

Comparison of TOPMODEL streamflow simulations using NEXRAD-based and measured rainfall data, McTier Creek watershed, South Carolina

USGS Publications Warehouse

Feaster, Toby D.; Westcott, Nancy E.; Hudson, Robert J.M.; Conrads, Paul; Bradley, Paul M.

2012-01-01

Rainfall is an important forcing function in most watershed models. As part of a previous investigation to assess interactions among hydrologic, geochemical, and ecological processes that affect fish-tissue mercury concentrations in the Edisto River Basin, the topography-based hydrological model (TOPMODEL) was applied in the McTier Creek watershed in Aiken County, South Carolina. Measured rainfall data from six National Weather Service (NWS) Cooperative (COOP) stations surrounding the McTier Creek watershed were used to calibrate the McTier Creek TOPMODEL. Since the 1990s, the next generation weather radar (NEXRAD) has provided rainfall estimates at a finer spatial and temporal resolution than the NWS COOP network. For this investigation, NEXRAD-based rainfall data were generated at the NWS COOP stations and compared with measured rainfall data for the period June 13, 2007, to September 30, 2009. Likewise, these NEXRAD-based rainfall data were used with TOPMODEL to simulate streamflow in the McTier Creek watershed and then compared with the simulations made using measured rainfall data. NEXRAD-based rainfall data for non-zero rainfall days were lower than measured rainfall data at all six NWS COOP locations. The total number of concurrent days for which both measured and NEXRAD-based data were available at the COOP stations ranged from 501 to 833, the number of non-zero days ranged from 139 to 209, and the total difference in rainfall ranged from -1.3 to -21.6 inches. With the calibrated TOPMODEL, simulations using NEXRAD-based rainfall data and those using measured rainfall data produce similar results with respect to matching the timing and shape of the hydrographs. Comparison of the bias, which is the mean of the residuals between observed and simulated streamflow, however, reveals that simulations using NEXRAD-based rainfall tended to underpredict streamflow overall. Given that the total NEXRAD-based rainfall data for the simulation period is lower than the total measured rainfall at the NWS COOP locations, this bias would be expected. Therefore, to better assess the use of NEXRAD-based rainfall estimates as compared to NWS COOP rainfall data on the hydrologic simulations, TOPMODEL was recalibrated and updated simulations were made using the NEXRAD-based rainfall data. Comparisons of observed and simulated streamflow show that the TOPMODEL results using measured rainfall data and NEXRAD-based rainfall are comparable. Nonetheless, TOPMODEL simulations using NEXRAD-based rainfall still tended to underpredict total streamflow volume, although the magnitude of differences were similar to the simulations using measured rainfall. The McTier Creek watershed was subdivided into 12 subwatersheds and NEXRAD-based rainfall data were generated for each subwatershed. Simulations of streamflow were generated for each subwatershed using NEXRAD-based rainfall and compared with subwatershed simulations using measured rainfall data, which unlike the NEXRAD-based rainfall were the same data for all subwatersheds (derived from a weighted average of the six NWS COOP stations surrounding the basin). For the two simulations, subwatershed streamflow were summed and compared to streamflow simulations at two U.S. Geological Survey streamgages. The percentage differences at the gage near Monetta, South Carolina, were the same for simulations using measured rainfall data and NEXRAD-based rainfall. At the gage near New Holland, South Carolina, the percentage differences using the NEXRAD-based rainfall were twice as much as those using the measured rainfall. Single-mass curve comparisons showed an increase in the total volume of rainfall from north to south. Similar comparisons of the measured rainfall at the NWS COOP stations showed similar percentage differences, but the NEXRAD-based rainfall variations occurred over a much smaller distance than the measured rainfall. Nonetheless, it was concluded that in some cases, using NEXRAD-based rainfall data in TOPMODEL streamflow simulations may provide an effective alternative to using measured rainfall data. For this investigation, however, TOPMODEL streamflow simulations using NEXRAD-based rainfall data for both calibration and simulations did not show significant improvements with respect to matching observed streamflow over simulations generated using measured rainfall data.

Evaluating rainfall errors in global climate models through cloud regimes

NASA Astrophysics Data System (ADS)

Tan, Jackson; Oreopoulos, Lazaros; Jakob, Christian; Jin, Daeho

2017-07-01

Global climate models suffer from a persistent shortcoming in their simulation of rainfall by producing too much drizzle and too little intense rain. This erroneous distribution of rainfall is a result of deficiencies in the representation of underlying processes of rainfall formation. In the real world, clouds are precursors to rainfall and the distribution of clouds is intimately linked to the rainfall over the area. This study examines the model representation of tropical rainfall using the cloud regime concept. In observations, these cloud regimes are derived from cluster analysis of joint-histograms of cloud properties retrieved from passive satellite measurements. With the implementation of satellite simulators, comparable cloud regimes can be defined in models. This enables us to contrast the rainfall distributions of cloud regimes in 11 CMIP5 models to observations and decompose the rainfall errors by cloud regimes. Many models underestimate the rainfall from the organized convective cloud regime, which in observation provides half of the total rain in the tropics. Furthermore, these rainfall errors are relatively independent of the model's accuracy in representing this cloud regime. Error decomposition reveals that the biases are compensated in some models by a more frequent occurrence of the cloud regime and most models exhibit substantial cancellation of rainfall errors from different regimes and regions. Therefore, underlying relatively accurate total rainfall in models are significant cancellation of rainfall errors from different cloud types and regions. The fact that a good representation of clouds does not lead to appreciable improvement in rainfall suggests a certain disconnect in the cloud-precipitation processes of global climate models.

Molten thermoplastic dripping behavior induced by flame spread over wire insulation under overload currents.

PubMed

He, Hao; Zhang, Qixing; Tu, Ran; Zhao, Luyao; Liu, Jia; Zhang, Yongming

2016-12-15

The dripping behavior of the molten thermoplastic insulation of copper wire, induced by flame spread under overload currents, was investigated for a better understanding of energized electrical wire fires. Three types of sample wire, with the same polyethylene insulation thickness and different core diameters, were used in this study. First, overload current effects on the transient one-dimensional wire temperature profile were predicted using simplified theoretical analysis; the heating process and equilibrium temperature were obtained. Second, experiments on the melting characteristics were conducted in a laboratory environment, including drop formation and frequency, falling speed, and combustion on the steel base. Third, a relationship between molten mass loss and volume variation was proposed to evaluate the dripping time and frequency. A strong current was a prerequisite for the wire dripping behavior and the averaged dripping frequency was found to be proportional to the square of the current based on the theoretical and experimental results. Finally, the influence of dripping behavior on the flame propagation along the energized electrical wire was discussed. The flame width, bright flame height and flame spreading velocity presented different behaviors. Copyright © 2016 Elsevier B.V. All rights reserved.

Rainfall simulators in hydrological and geomorphological sciences: benefits, applications and future research directions

NASA Astrophysics Data System (ADS)

Iserloh, Thomas; Cerdà, Artemi; Fister, Wolfgang; Seitz, Steffen; Keesstra, Saskia; Green, Daniel; Gabriels, Donald

2017-04-01

Rainfall simulators are used extensively within the hydrological and geomorphological sciences and provide a useful investigative tool to understand many processes, such as: (i) plot-scale runoff, infiltration and erosion; (ii) irrigation and crop management, and; (iii) investigations into flooding within a laboratory setting. Although natural rainfall is desirable as it represents actual conditions in a given geographic location, data acquisition relying on natural rainfall is often hindered by its unpredictable nature. Furthermore, rainfall characteristics such as the intensity, duration, drop size distribution and kinetic energy cannot be spatially or temporally regulated or repeated between experimentation. Rainfall simulators provide a suitable method to overcome the issues associated with depending on potentially erratic and unpredictable natural rainfall as they allow: (i) multiple measurements to be taken quickly without waiting for suitable natural rainfall conditions; (ii) the simulation of spatially and/or temporally controlled rainfall patterns over a given plot area, and; (iii) the creation of a closed environment, allowing simplified measurement of input and output conditions. There is no standardisation of rainfall simulation and as such, rainfall simulators differ in their design, rainfall characteristics and research application. Although this impedes drawing meaningful comparisons between studies, this allows researchers to create a bespoke and tailored rainfall simulator for the specific research application. This paper summarises the rainfall simulators used in European research institutions (Universities of Trier, Valencia, Basel, Tuebingen, Wageningen, Loughborough and Ghent) to investigate a number of hydrological and geomorphological issues and includes details on the design specifications (such as the extent and characteristics of simulated rainfall), as well as a discussion of the purpose and application of the rainfall simulator.

A theoretically consistent stochastic cascade for temporal disaggregation of intermittent rainfall

NASA Astrophysics Data System (ADS)

Lombardo, F.; Volpi, E.; Koutsoyiannis, D.; Serinaldi, F.

2017-06-01

Generating fine-scale time series of intermittent rainfall that are fully consistent with any given coarse-scale totals is a key and open issue in many hydrological problems. We propose a stationary disaggregation method that simulates rainfall time series with given dependence structure, wet/dry probability, and marginal distribution at a target finer (lower-level) time scale, preserving full consistency with variables at a parent coarser (higher-level) time scale. We account for the intermittent character of rainfall at fine time scales by merging a discrete stochastic representation of intermittency and a continuous one of rainfall depths. This approach yields a unique and parsimonious mathematical framework providing general analytical formulations of mean, variance, and autocorrelation function (ACF) for a mixed-type stochastic process in terms of mean, variance, and ACFs of both continuous and discrete components, respectively. To achieve the full consistency between variables at finer and coarser time scales in terms of marginal distribution and coarse-scale totals, the generated lower-level series are adjusted according to a procedure that does not affect the stochastic structure implied by the original model. To assess model performance, we study rainfall process as intermittent with both independent and dependent occurrences, where dependence is quantified by the probability that two consecutive time intervals are dry. In either case, we provide analytical formulations of main statistics of our mixed-type disaggregation model and show their clear accordance with Monte Carlo simulations. An application to rainfall time series from real world is shown as a proof of concept.

Calibration of three rainfall simulators with automatic measurement methods

NASA Astrophysics Data System (ADS)

Roldan, Margarita

2010-05-01

CALIBRATION OF THREE RAINFALL SIMULATORS WITH AUTOMATIC MEASUREMENT METHODS M. Roldán (1), I. Martín (2), F. Martín (2), S. de Alba(3), M. Alcázar(3), F.I. Cermeño(3) 1 Grupo de Investigación Ecología y Gestión Forestal Sostenible. ECOGESFOR-Universidad Politécnica de Madrid. E.U.I.T. Forestal. Avda. Ramiro de Maeztu s/n. Ciudad Universitaria. 28040 Madrid. margarita.roldan@upm.es 2 E.U.I.T. Forestal. Avda. Ramiro de Maeztu s/n. Ciudad Universitaria. 28040 Madrid. 3 Facultad de Ciencias Geológicas. Universidad Complutense de Madrid. Ciudad Universitaria s/n. 28040 Madrid The rainfall erosivity is the potential ability of rain to cause erosion. It is function of the physical characteristics of rainfall (Hudson, 1971). Most expressions describing erosivity are related to kinetic energy or momentum and so with drop mass or size and fall velocity. Therefore, research on factors determining erosivity leds to the necessity to study the relation between fall height and fall velocity for different drop sizes, generated in a rainfall simulator (Epema G.F.and Riezebos H.Th, 1983) Rainfall simulators are one of the most used tools for erosion studies and are used to determine fall velocity and drop size. Rainfall simulators allow repeated and multiple measurements The main reason for use of rainfall simulation as a research tool is to reproduce in a controlled way the behaviour expected in the natural environment. But in many occasions when simulated rain is used in order to compare it with natural rain, there is a lack of correspondence between natural and simulated rain and this can introduce some doubt about validity of data because the characteristics of natural rain are not adequately represented in rainfall simulation research (Dunkerley D., 2008). Many times the rainfall simulations have high rain rates and they do not resemble natural rain events and these measures are not comparables. And besides the intensity is related to the kinetic energy which determines the rainfall erosivity (Dunkerley D., 2008). A special attention must be paid to the experimental design and the understanding of the measurements obtained. The objective of this study is the calibration of simulated rain. In order to achieve this objective a rainfall simulator and disdrometer have been used. The first one is a nozzle type and its sprinkler system was located at different heights, three different spray nozzles supplied the water with known pressure. The simulated rainfall presented different intensities, drop diameters distribution and so different kinetic energy. The instrument of measurement for registering data is the disdrometer (Joss and Waldvogel, 1967) which provides the total number of impacts of raindrops, minute after minute, grouped in 20 classes according to their size which allows the real time measurements of the drop diameter distributions, kinetic energy per minute and intensity per minute. Disdrometer registers data in supposing drops fall down with terminal velocity but this velocity can reach up to 7-9 m of height in natural raindrop, depending on drop diameters. If the height of simulator is high enough the drops could recuperate their terminal velocities and their kinetic energies could be true. The nozzles were located to different heights in order to achieve these terminal velocities. These heights vary depending on the nozzles used, when the drops supplied by the nozzle are smaller the terminal velocity is reached sooner than when the drops are bigger. The physical characteristics of simulated rainfall in the three nozzles, intensity, drop diameter distributions and kinetic energy, are known and steady when the drops supplied by the nozzles reach terminal velocities.

Effect of monthly areal rainfall uncertainty on streamflow simulation

NASA Astrophysics Data System (ADS)

Ndiritu, J. G.; Mkhize, N.

2017-08-01

Areal rainfall is mostly obtained from point rainfall measurements that are sparsely located and several studies have shown that this results in large areal rainfall uncertainties at the daily time step. However, water resources assessment is often carried out a monthly time step and streamflow simulation is usually an essential component of this assessment. This study set out to quantify monthly areal rainfall uncertainties and assess their effect on streamflow simulation. This was achieved by; i) quantifying areal rainfall uncertainties and using these to generate stochastic monthly areal rainfalls, and ii) finding out how the quality of monthly streamflow simulation and streamflow variability change if stochastic areal rainfalls are used instead of historic areal rainfalls. Tests on monthly rainfall uncertainty were carried out using data from two South African catchments while streamflow simulation was confined to one of them. A non-parametric model that had been applied at a daily time step was used for stochastic areal rainfall generation and the Pitman catchment model calibrated using the SCE-UA optimizer was used for streamflow simulation. 100 randomly-initialised calibration-validation runs using 100 stochastic areal rainfalls were compared with 100 runs obtained using the single historic areal rainfall series. By using 4 rain gauges alternately to obtain areal rainfall, the resulting differences in areal rainfall averaged to 20% of the mean monthly areal rainfall and rainfall uncertainty was therefore highly significant. Pitman model simulations obtained coefficient of efficiencies averaging 0.66 and 0.64 in calibration and validation using historic rainfalls while the respective values using stochastic areal rainfalls were 0.59 and 0.57. Average bias was less than 5% in all cases. The streamflow ranges using historic rainfalls averaged to 29% of the mean naturalised flow in calibration and validation and the respective average ranges using stochastic monthly rainfalls were 86 and 90% of the mean naturalised streamflow. In calibration, 33% of the naturalised flow located within the streamflow ranges with historic rainfall simulations and using stochastic rainfalls increased this to 66%. In validation the respective percentages of naturalised flows located within the simulated streamflow ranges were 32 and 72% respectively. The analysis reveals that monthly areal rainfall uncertainty is significant and incorporating it into streamflow simulation would add validity to the results.

Set-up and calibration of an indoor nozzle-type rainfall simulator for soil erosion studies

NASA Astrophysics Data System (ADS)

Lassu, T.; Seeger, M.

2012-04-01

Rainfall simulation is one of the most prevalent methods used in soil erosion studies on agricultural land. In-situ simulators have been used to relate soil surface characteristics and management to runoff generation, infiltration and erosion, eg. the influence of different cultivation systems, and to parameterise erosion models. Laboratory rainfall simulators have been used to determine the impact of the soil surface characteristics such as micro-topography, surface roughness, and soil chemistry on infiltration and erosion rates, and to elucidate the processes involved. The purpose of the following study is to demonstrate the set-up and the calibration of a large indoor, nozzle-type rainfall simulator (RS) for soil erosion, surface runoff and rill development studies. This RS is part of the Kraijenhoff van de Leur Laboratory for Water and Sediment Dynamics in Wageningen University. The rainfall simulator consists from a 6 m long and 2,5 m wide plot, with metal lateral frame and one open side. Infiltration can be collected in different segments. The plot can be inclined up to 15.5° slope. From 3,85 m height above the plot 2 Lechler nozzles 460.788 are sprinkling the water onto the surface with constant intensity. A Zehnder HMP 450 pump provides the constant water supply. An automatic pressure switch on the pump keeps the pressure constant during the experiments. The flow rate is controlled for each nozzle by independent valves. Additionally, solenoid valves are mounted at each nozzle to interrupt water flow. The flow is monitored for each nozzle with flow meters and can be recorded within the computer network. For calibration of the RS we measured the rainfall distribution with 60 gauges equally distributed over the plot during 15 minutes for each nozzle independently and for a combination of 2 identical nozzles. The rainfall energy was recorded on the same grid by measuring drop size distribution and fall velocity with a laser disdrometer. We applied 2 different flow rates (4,5 l/min and 5,5 l/min), resulting in different rainfall intensities and made 2 repetitions each. The average rainfall intensity was 36,8 mm/h at the first and 37,6 mm/h at the second repetition with the lower flow rate (4,5 l/min). With the higher flow rate (5,5 l/min) at the first repetition it was 44,4 mm/h and 46 mm/h at the second one. The maximum and minimum values were 22 mm and 2 mm at the lower (4,5 l/min) flow rate, respectively 26 mm and 4 mm at the higher one (5,5 l/min). In this latter case, the resulting average kinetic energy reached 7 J m-2 mm-1, with a maximum 31,3 J m-2 mm-1 of and a minimum of 2,9 J m-2 mm-1. The Christiansen Uniformity coefficient (CU) for the lower intensities was 66% and 69%, respectively, with the higher intensities slightly better (70% and 72%). The data of the rainfall simulator in Wageningen make it a promising tool for research in soil erosion processes.

The wildgeographer avatar shows how to measure soil erosion rates by means of a rainfall simulator

NASA Astrophysics Data System (ADS)

Cerdà, Artemi; González Pelayo, Óscar; Pereira, Paulo; Novara, Agata; Iserloh, Thomas; Prosdocimi, Massimo

2015-04-01

This contribution to the immersed worlds wish to develop the avatar that will teach the students and other scientists how to develop measurements of soil erosion, surface runoff and wetting fronts by means of simulated rainfall experiments. Rainfall simulation is a well established and knows methodology to measure the soil erosion rates and soil hydrology under controlled conditions (Cerdà 1998a; Cerdà, 1998b; Cerdà and Jurgensen, 2011; Dunkerley, 2012; Iserloh et al., 2012; Iserloh et al., 2013; Ziadat and Taimeh, 2013; Butzen et al., 2014). However, is a method that requires a long training and expertise to avoid mismanagement and mistaken. To use and avatar can help in the teaching of the technique and the dissemination of the findings. This contribution will show to other avatars how to develop an experiment with simulated rainfall and will help to take the right decision in the design of the experiments. Following the main parts of the experiments and measurements the Wildgeographer avatar must develop: 1. Determine the objectives and decide which rainfall intensity and distribution, and which plot size to be used. Choose between a laboratory or a field rainfall simulation. 2. Design of the rainfall simulator to achieve the objectives: type of rainfall simulator (sprayer or drop former) and calibrate. 3. The experiments are carried out. 4. The results are show. Acknowledgements To the "Ministerio de Economía and Competitividad" of Spanish Government for finance the POSTFIRE project (CGL2013- 47862-C2-1-R). The research projects GL2008-02879/BTE, LEDDRA 243857 and PREVENTING AND REMEDIATING DEGRADATION OF SOILS IN EUROPE THROUGH LAND CARE (RECARE)FP7-ENV-2013- supported this research. References Butzen, V., Seeger, M., Wirtz, S., Huemann, M., Mueller, C., Casper, M., Ries, J. B. 2014. Quantification of Hortonian overland flow generation and soil erosion in a Central European low mountain range using rainfall experiments. Catena, 113, 202-212. Cerdà, A. 1998a. Effect of climate on surface flow along a climatological gradient in Israel. A field rainfall simulation approach. Journal of Arid Environments, 38, 145-159. Cerdà, A. 1998b. The influence of aspect and vegetation on seasonal changes in erosion under rainfall simulation on a clay soil in Spain. Canadian Journal of Soil Science, 78, 321-330. Cerdà, A., Jurgensen, M. F. 2011. Ant mounds as a source of sediment on citrus orchard plantations in eastern Spain. A three-scale rainfall simulation approach. Catena, 85(3), 231-236. Dunkerley, D. 2012. Effects of rainfall intensity fluctuations on infiltration and runoff: rainfall simulation on dryland soils, Fowlers Gap, Australia. Hydrological Processes, 26(15), 2211-2224. Iserloh, T., Ries, J.B., Arnaez, J., Boix Fayos, C., Butzen, V., Cerdà, A., Echeverría, M.T., Fernández-Gálvez, J., Fister, W., Geißler, C., Gómez, J.A., Gómez-Macpherson, H., Kuhn, N.J., Lázaro, R., León, F.J., Martínez-Mena, M., Martínez-Murillo, J.F., Marzen, M., Mingorance, M.D., Ortigosa, L., Peters, P., Regüés, D., Ruiz-Sinoga, J.D., Scholten, T., Seeger, M., Solé-Benet, A., Wengel, R., Wirtz, S. 2013. European small portable rainfall simulators: a comparison of rainfall characteristics. Catena, 110, 100-112. Doi: 10.1016/j.catena.2013.05.013 Iserloh, T., Ries, J.B., Cerdà, A., Echeverría, M.T., Fister, W., Geißler, C., Kuhn, N.J., León, F.J., Peters, P., Schindewolf, M., Schmidt, J., Scholten, T., Seeger, M. (2012): Comparative measurements with seven rainfall simulators on uniform bare fallow land. Zeitschrift für Geomorphologie, 57, 193-201. DOI: 10.1127/0372- 8854/2012/S-00118. Ziadat, F. M., Taimeh, A. Y. 2013. Effect of rainfall intensity, slope and land use and antecedent soil moisture on soil erosion in an arid environment. Land Degradation & Development, 24: 582- 590. DOI 10.1002/ldr.2239

Can we improve streamflow simulation by using higher resolution rainfall information?

NASA Astrophysics Data System (ADS)

Lobligeois, Florent; Andréassian, Vazken; Perrin, Charles

2013-04-01

The catchment response to rainfall is the interplay between space-time variability of precipitation, catchment characteristics and antecedent hydrological conditions. Precipitation dominates the high frequency hydrological response, and its simulation is thus dependent on the way rainfall is represented. One of the characteristics which distinguishes distributed from lumped models is their ability to represent explicitly the spatial variability of precipitation and catchment characteristics. The sensitivity of runoff hydrographs to the spatial variability of forcing data has been a major concern of researchers over the last three decades. However, although the literature on the relationship between spatial rainfall and runoff response is abundant, results are contrasted and sometimes contradictory. Several studies concluded that including information on rainfall spatial distribution improves discharge simulation (e.g. Ajami et al., 2004, among others) whereas other studies showed the lack of significant improvement in simulations with better information on rainfall spatial pattern (e.g. Andréassian et al., 2004, among others). The difficulties to reach a clear consensus is mainly due to the fact that each modeling study is implemented only on a few catchments whereas the impact of the spatial distribution of rainfall on runoff is known to be catchment and event characteristics-dependent. Many studies are virtual experiments and only compare flow simulations, which makes it difficult to reach conclusions transposable to real-life case studies. Moreover, the hydrological rainfall-runoff models differ between the studies and the parameterization strategies sometimes tend to advantage the distributed approach (or the lumped one). Recently, Météo-France developed a rainfall reanalysis over the whole French territory at the 1-kilometer resolution and the hourly time step over a 10-year period combining radar data and raingauge measurements: weather radar data were corrected and adjusted with both hourly and daily raingauge data. Based on this new high resolution product, we propose a framework to evaluate the improvements in streamflow simulation by using higher resolution rainfall information. Semi-distributed modelling is performed for different spatial resolution of precipitation forcing: from lumped to semi-distributed simulations. Here we do not work on synthetic (simulated) streamflow, but with actual measurements, on a large set of 181 French catchments representing a variety of size and climate. The rainfall-runoff model is re-calibrated for each resolution of rainfall spatial distribution over a 5-year sub-period and evaluated on the complementary sub-period in validation mode. The results are analysed by catchment classes based on catchment area and for various types of rainfall events based on the spatial variability of precipitation. References Ajami, N. K., Gupta, H. V, Wagener, T. & Sorooshian, S. (2004) Calibration of a semi-distributed hydrologic model for streamflow estimation along a river system. Journal of Hydrology 298(1-4), 112-135. Andréassian, V., Oddos, A., Michel, C., Anctil, F., Perrin, C. & Loumagne, C. (2004) Impact of spatial aggregation of inputs and parameters on the efficiency of rainfall-runoff models: A theoretical study using chimera watersheds. Water Resources Research 40(5), 1-9.

Ensemble flood simulation for a small dam catchment in Japan using 10 and 2 km resolution nonhydrostatic model rainfalls

NASA Astrophysics Data System (ADS)

Kobayashi, Kenichiro; Otsuka, Shigenori; Apip; Saito, Kazuo

2016-08-01

This paper presents a study on short-term ensemble flood forecasting specifically for small dam catchments in Japan. Numerical ensemble simulations of rainfall from the Japan Meteorological Agency nonhydrostatic model (JMA-NHM) are used as the input data to a rainfall-runoff model for predicting river discharge into a dam. The ensemble weather simulations use a conventional 10 km and a high-resolution 2 km spatial resolutions. A distributed rainfall-runoff model is constructed for the Kasahori dam catchment (approx. 70 km2) and applied with the ensemble rainfalls. The results show that the hourly maximum and cumulative catchment-average rainfalls of the 2 km resolution JMA-NHM ensemble simulation are more appropriate than the 10 km resolution rainfalls. All the simulated inflows based on the 2 and 10 km rainfalls become larger than the flood discharge of 140 m3 s-1, a threshold value for flood control. The inflows with the 10 km resolution ensemble rainfall are all considerably smaller than the observations, while at least one simulated discharge out of 11 ensemble members with the 2 km resolution rainfalls reproduces the first peak of the inflow at the Kasahori dam with similar amplitude to observations, although there are spatiotemporal lags between simulation and observation. To take positional lags into account of the ensemble discharge simulation, the rainfall distribution in each ensemble member is shifted so that the catchment-averaged cumulative rainfall of the Kasahori dam maximizes. The runoff simulation with the position-shifted rainfalls shows much better results than the original ensemble discharge simulations.

Analysis of Rainfall Infiltration Law in Unsaturated Soil Slope

PubMed Central

Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

2014-01-01

In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (θ s - θ r), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process. PMID:24672332

Analysis of rainfall infiltration law in unsaturated soil slope.

PubMed

Zhang, Gui-rong; Qian, Ya-jun; Wang, Zhang-chun; Zhao, Bo

2014-01-01

In the study of unsaturated soil slope stability under rainfall infiltration, it is worth continuing to explore how much rainfall infiltrates into the slope in a rain process, and the amount of rainfall infiltrating into slope is the important factor influencing the stability. Therefore, rainfall infiltration capacity is an important issue of unsaturated seepage analysis for slope. On the basis of previous studies, rainfall infiltration law of unsaturated soil slope is analyzed. Considering the characteristics of slope and rainfall, the key factors affecting rainfall infiltration of slope, including hydraulic properties, water storage capacity (θs - θr), soil types, rainfall intensities, and antecedent and subsequent infiltration rates on unsaturated soil slope, are discussed by using theory analysis and numerical simulation technology. Based on critical factors changing, this paper presents three calculation models of rainfall infiltrability for unsaturated slope, including (1) infiltration model considering rainfall intensity; (2) effective rainfall model considering antecedent rainfall; (3) infiltration model considering comprehensive factors. Based on the technology of system response, the relationship of rainfall and infiltration is described, and the prototype of regression model of rainfall infiltration is given, in order to determine the amount of rain penetration during a rain process.

Mesoscale Assimilation of TMI Rainfall Data with 4DVAR: Sensitivity Studies

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Pu, Zhaoxia

2003-01-01

Sensitivity studies are performed on the assimilation of TRMM (Tropical Rainfall Measurement Mission) Microwave Imager (TMI) derived rainfall data into a mesoscale model using a four-dimensional variational data assimilation (4DVAR) technique. A series of numerical experiments is conducted to evaluate the impact of TMI rainfall data on the numerical simulation of Hurricane Bonnie (1998). The results indicate that rainfall data assimilation is sensitive to the error characteristics of the data and the inclusion of physics in the adjoint and forward models. In addition, assimilating the rainfall data alone is helpful for producing a more realistic eye and rain bands in the hurricane but does not ensure improvements in hurricane intensity forecasts. Further study indicated that it is necessary to incorporate TMI rainfall data together with other types of data such as wind data into the model, in which case the inclusion of the rainfall data further improves the intensity forecast of the hurricane. This implies that proper constraints may be needed for rainfall assimilation.

A novel approach to model dynamic flow interactions between storm sewer system and overland surface for different land covers in urban areas

NASA Astrophysics Data System (ADS)

Chang, Tsang-Jung; Wang, Chia-Ho; Chen, Albert S.

2015-05-01

In this study, we developed a novel approach to simulate dynamic flow interactions between storm sewers and overland surface for different land covers in urban areas. The proposed approach couples the one-dimensional (1D) sewer flow model (SFM) and the two-dimensional (2D) overland flow model (OFM) with different techniques depending on the land cover type of the study areas. For roads, pavements, plazas, and so forth where rainfall becomes surface runoff before entering the sewer system, the rainfall-runoff process is simulated directly in the 2D OFM, and the runoff is drained to the sewer network via inlets, which is regarded as the input to 1D SFM. For green areas on which rainfall falls into the permeable ground surface and the generated direct runoff traverses terrain, the deduction rate is applied to the rainfall for reflecting the soil infiltration in the 2D OFM. For flat building roofs with drainage facilities allowing rainfall to drain directly from the roof to sewer networks, the rainfall-runoff process is simulated using the hydrological module in the 1D SFM where no rainfall is applied to these areas in the 2D OFM. The 1D SFM is used for hydraulic simulations in the sewer network. Where the flow in the drainage network exceeds its capacity, a surcharge occurs and water may spill onto the ground surface if the pressure head in a manhole exceeds the ground elevation. The overflow discharge from the sewer system is calculated by the 1D SFM and considered a point source in the 2D OFM. The overland flow will return into the sewer network when it reaches an inlet that connects to an un-surcharged manhole. In this case, the inlet is considered as a point sink in the 2D OFM and an inflow to a manhole in the 1D SFM. The proposed approach was compared to other five urban flood modelling techniques with four rainfall events that had previously recorded inundation areas. The merits and drawbacks of each modelling technique were compared and discussed. Based on the simulated results, the proposed approach was found to simulate floodings closer to the survey records than other approaches because the physical rainfall-runoff phenomena in urban environment were better reflected.

A model for estimating time-variant rainfall infiltration as a function of antecedent surface moisture and hydrologic soil type

NASA Technical Reports Server (NTRS)

Wilkening, H. A.; Ragan, R. M.

1982-01-01

Recent research indicates that the use of remote sensing techniques for the measurement of near surface soil moisture could be practical in the not too distant future. Other research shows that infiltration rates, especially for average or frequent rainfall events, are extremely sensitive to the proper definition and consideration of the role of the soil moisture at the beginning of the rainfall. Thus, it is important that an easy to use, but theoretically sound, rainfall infiltration model be available if the anticipated remotely sensed soil moisture data is to be optimally utilized for hydrologic simulation. A series of numerical experiments with the Richards' equation for an array of conditions anticipated in watershed hydrology were used to develop functional relationships that describe temporal infiltration rates as a function of soil type and initial moisture conditions.

Seasonal variations of cave conditions and drip water stable isotopes from a monitoring study of Raccoon Mountain Caverns, Tennessee, and its implications in interpreting speleothem record

NASA Astrophysics Data System (ADS)

Holtzclaw, C. L.; Gordon, R. D.; Feng, W.; Allard, J.

2015-12-01

A two-year monitoring study at Raccoon Mountain Caverns near Chattanooga, Tennessee was carried out in an attempt to establish quantitative relationships between climate signals and drip water stable isotopes for interpreting speleothem paleoclimate records from the cave. Eight field trips were made from Jan. 2014 to Jun. 2015, during which cave meteorological conditions (RH, temperature and cave air CO2 concentration) and drip rate were measured for 5 sites inside the cave. 63 cave drip and pool water samples were collected and analyzed for oxygen and hydrogen isotope compositions (δ18O and δD values). Cave air temperature varied throughout the study period, the temporal variations ranged at different sites from 2 to 8.4 °C (the greatest variation was observed at sites that are closer to the entrance or surface). These are significantly less than outside temperatures range of 24 °C, but more than observed in other monitored caves. Elevated cave-air CO2 concentration (3200 ppm) and slow drip rate during the summer indicated slowed or stalled growth of calcite. The overall range of δ18O values were -7.1‰ to -4.5‰. A δD vs δ18O diagram yields a slope of 6.1, which falls within the normal range of 6-8 for local Meteoric Water Line. The value is slightly above Global Meteoric Water Line, indicating lack of evaporative effect. Throughout the study period, the δ18O values varied from 0.6 ‰ at some sites to 1.9‰ at others. The largest changes were likely due to the close proximity of collection sites to the surface precipitation. Spatially, for samples collected at each cave trip, different sites displayed variations of δ18O values from 0‰ to 1.7‰. The difference could be attributed to different type of drip sites with varying types of flow paths rainwater takes to the drip sites. The significant seasonal shift of drip water δ18O values and growth conditions indicate importance of consideration of seasonality in interpreting speleothem δ18O record from this cave.

Comparison of different types of medium scale field rainfall simulators

NASA Astrophysics Data System (ADS)

Dostál, Tomáš; Strauss, Peter; Schindewolf, Marcus; Kavka, Petr; Schmidt, Jürgen; Bauer, Miroslav; Neumann, Martin; Kaiser, Andreas; Iserloh, Thomas

2015-04-01

Rainfall simulators are used in numerous experiments to study runoff and soil erosion characteristics. However, they usually differ in their construction details, rainfall generation, plot size and other technical parameters. As field experiments using medium to large scale rainfall simulators (plot length 3 - 8 m) are very much time and labor consuming, close cooperation of individual teams and comparability of results is highly desirable to enlarge the database of results. Two experimental campaigns were organized to compare three field rainfall simulators of similar scale (plot size), but with different technical parameters. The results were then compared, to identify parameters that are crucial for soil loss and surface runoff formation and test if results from individual devices can be reliably compared. The rainfall simulators compared were: field rainfall simulator of CTU Prague (the Czech Republic) (Kavka et al., 2012; EGU2015-11025), field simulator of BAW (Austria) (Strauss et al., 2002) and field simulator of TU Bergakademie Freiberg (Germany) (Schindewolf & Schmidt 2012). The device of CTU Prague is usually applied to a plot size of 9,5 x 2 m employing 4 nozzles SS Full Jet 40WSQ mounted on folding arm, working pressure is 0.8 bar, height of nozzles is 2.65 m. The intensity of rainfall is regulated electronically, which leaves the nozzle opened only for certain time. The rainfall simulator of BAW is constructed as a modular system, which is usually applied for a length of 5 m (area 2 x 5 m), using 6 nozzles SS Full Jet 40WSQ. Usual working pressure is 0.25 bar. Elevation of nozzles is 2.6 m. The intensity of rainfall is regulated electronically, which leaves the nozzle opened only for certain time. The device of TU Bergakademie Freiberg is also standard modular system, working usually with a plot size of 3 x 1 m, using 3 oscillating VeeJet 80/100 nozzles with an usual operating pressure of 0.5 bar. Intensity is regulated by the frequency of sweeps above the experimental plot. Comparison was done during two independent campaigns, where always two devices were present. Rainfall intensity for the experiments varied between 40 to 60 mm/h. Mutual comparison was carried out between the CTU Prague and TU Freiberg RSs at plot size of 3 x 1 m and Between CTU Prague and BAW RSs at plot size of 5 x 2 m. In general, the experiments revealed a significant effect of potential heterogeneities at the experimental plots and an effect of raindrop energy on both surface runoff formation and mainly soil loss. Therefore, coordination of methodology of the experiments and careful control of initial conditions seem to be a crucial point for comparability of results from individual devices. Detailed results will be presented on the poster. The research has been supported by the research grants SGS14/180/OHK1/3T/11, QJ1230056 and 7AMB14AT020. References Kavka, P., Davidová, T., Janotová, B., Bauer, M. a Dostál, T. 2012. Mobilní dešťový simulátor.(in Czech), Stavební obzor. 8, 2012. Schindewolf, M. & J. Schmidt (2012): Parameterization of the EROSION 2D/3D soil erosion model using a small-scale rainfall simulator and upstream runoff simulation, Catena 91, pp. 47-55, DOI: 10.1016/j.catena.2011.01.007 Strauss P., J.Pitty, M.Pfeffer, A. Mentler (2000): Rainfall Simulation for Outdoor Experiments. In: P. Jamet, J. Cornejo(eds.): Current research methods to assess the environmental fate of pesticides. pp. 329-333, INRA Editions.

Simulation and prediction the impact of climate change into water resources in Bengawan Solo watershed based on CCAM (Conformal Cubic Atmospheric Model) data

NASA Astrophysics Data System (ADS)

Sipayung, Sinta B.; Nurlatifah, Amalia; Siswanto, Bambang

2018-05-01

Bengawan Solo Watershed is one of the largest watersheds in Indonesia. This watershed flows in many areas both in Central Java and East Java. Therefore, the water resources condition greatly affects many people. This research will be conducted on prediction of climate change effect on water resources condition in terms of rainfall conditions in Bengawan Solo River Basin. The goal of this research is to know and predict the climate change impact on water resources based on CCAM (Conformal Cubic Atmosphere Model) with downscaling baseline (historical) model data from 1949 to 2005 and RCP 4.5 from 2006 to 2069. The modeling data was validated with in-situ data (measurement data). To analyse the water availability condition in Bengawan Solo Watershed, the simulation of river flow and water balance condition were done in Bengawan Solo River. Simulation of river flow and water balance conditions were done with ArcSWAT model using climate data from CCAM, DEM SRTM 90 meter, soil type, and land use data. The results of this simulation indicate there is (i) The CCAM data itself after validation has a pretty good result when compared to the insitu data. Based on CCAM simulation results, it is predicted that in 2040-2069 rainfall in Bengawan Solo River Basin will decrease, to a maximum of only about 1 mm when compared to 1971-2000. (ii) The CCAM rainfall prediction itself shows that rainfall in Bengawan Solo River basin will decline until 2069 although the decline itself is not significant and tends to be negligible (rainfall is considered unchanged) (iii) Both in the DJF and JJA seasons, precipitation is predicted to decline as well despite the significant decline. (iv) The river flow simulation show that the water resources in Bengawan Solo River did not change significantly. This event occurred because the rainfall also did not change greatly and close to 0 mm/month.

Requirements for future development of small scale rainfall simulators

NASA Astrophysics Data System (ADS)

Iserloh, Thomas; Ries, Johannes B.; Seeger, Manuel

2013-04-01

Rainfall simulation with small scale simulators is a method used worldwide to assess the generation of overland flow, soil erosion, infiltration and interrelated processes such as soil sealing, crusting, splash and redistribution of solids and solutes. Following the outcomes of the project "Comparability of simulation results of different rainfall simulators as input data for soil erosion modelling (Deutsche Forschungsgemeinschaft - DFG, Project No. Ri 835/6-1)" and the "International Rainfall Simulator Workshop 2011" in Trier, the necessity for further technical improvements of simulators and strategies towards an adaption of designs and methods becomes obvious. Uniform measurements of artificially generated rainfall and comparative measurements on a prepared bare fallow with rainfall simulators used by European research groups showed limitations of the comparability of the results. The following requirements, essential for small portable rainfall simulators, were identified: (I) Low and efficient water consumption for use in areas with water shortage, (II) easy handling and control of test conditions, (III) homogeneous spatial rainfall distribution, (IV) best possible drop spectrum (physically), (V) reproducibility and knowledge of spatial distribution and drop spectrum, (VI) easy and fast training of operators to obtain reproducible experiments and (VII) good mobility and easy installation for use in remote areas and in regions where highly erosive rainfall events are rare or irregular. The presentation discusses possibilities for a common use of identical plot designs, rainfall intensities and nozzles.

Climate downscaling over South America for 1971-2000: application in SMAP rainfall-runoff model for Grande River Basin

NASA Astrophysics Data System (ADS)

da Silva, Felipe das Neves Roque; Alves, José Luis Drummond; Cataldi, Marcio

2018-03-01

This paper aims to validate inflow simulations concerning the present-day climate at Água Vermelha Hydroelectric Plant (AVHP—located on the Grande River Basin) based on the Soil Moisture Accounting Procedure (SMAP) hydrological model. In order to provide rainfall data to the SMAP model, the RegCM regional climate model was also used working with boundary conditions from the MIROC model. Initially, present-day climate simulation performed by RegCM model was analyzed. It was found that, in terms of rainfall, the model was able to simulate the main patterns observed over South America. A bias correction technique was also used and it was essential to reduce mistakes related to rainfall simulation. Comparison between rainfall simulations from RegCM and MIROC showed improvements when the dynamical downscaling was performed. Then, SMAP, a rainfall-runoff hydrological model, was used to simulate inflows at Água Vermelha Hydroelectric Plant. After calibration with observed rainfall, SMAP simulations were evaluated in two different periods from the one used in calibration. During calibration, SMAP captures the inflow variability observed at AVHP. During validation periods, the hydrological model obtained better results and statistics with observed rainfall. However, in spite of some discrepancies, the use of simulated rainfall without bias correction captured the interannual flow variability. However, the use of bias removal in the simulated rainfall performed by RegCM brought significant improvements to the simulation of natural inflows performed by SMAP. Not only the curve of simulated inflow became more similar to the observed inflow, but also the statistics improved their values. Improvements were also noticed in the inflow simulation when the rainfall was provided by the regional climate model compared to the global model. In general, results obtained so far prove that there was an added value in rainfall when regional climate model was compared to global climate model and that data from regional models must be bias-corrected so as to improve their results.

Description of a novel telemedicine-enabled comprehensive system of care: drip and ship plus drip and keep within a system of stroke care delivery.

PubMed

Commiskey, Patricia; Afshinnik, Arash; Cothren, Elizabeth; Gropen, Toby; Iwuchukwu, Ifeanyi; Jennings, Bethany; McGrade, Harold C; Mora-Guillot, Julia; Sabharwal, Vivek; Vidal, Gabriel A; Zweifler, Richard M; Gaines, Kenneth

2017-04-01

United States (US) and worldwide telestroke programs frequently focus only on emergency room hyper-acute stroke management. This article describes a comprehensive, telemedicine-enabled, stroke care delivery system that combines "drip and ship" and "drip and keep" models with a comprehensive stroke center primary hub at Ochsner Medical Center in New Orleans, advanced stroke-capable regional hubs, and geographically-aligned, "stroke-ready" spokes. The primary hub provides vascular neurology expertise via telemedicine and monitors care for patients remaining at regional hubs and spokes using a multidisciplinary team approach. By 2014, primary hub telestroke consults grew to ≈1000/year with 16 min average door to consult initiation and 20 min to completion, and 29% of ischemic stroke patients received recombinant tissue-type plasminogen activator (rtPA), increasing 275%. Most patients remained in hospitals close to home, but neurointensive care and interventional procedures were common reasons for primary hub transfer. Given the time sensitivity and expert consultation needed for complex acute stroke care delivery paradigms, telestroke programs are effective for fulfilling unmet care needs. Combining drip and ship and drip and keep management allows more patients to stay "local," limiting primary hub transfer unless more advanced services are required. Post admission telestroke management at spokes increases personnel efficiency and can positively impact stroke outcomes.

Effects of soil type and rainfall intensity on sheet erosion processes and sediment characteristics along the climatic gradient in central-south China.

PubMed

Wu, Xinliang; Wei, Yujie; Wang, Junguang; Xia, Jinwen; Cai, Chongfa; Wei, Zhiyuan

2018-04-15

Soil erosion poses a major threat to the sustainability of natural ecosystems. The main objective of this study was to investigate the effects of soil type and rainfall intensity on sheet erosion processes (hydrological, erosional processes and sediment characteristics) from temperate to tropical climate. Field plot experiments were conducted under pre-wetted bare fallow condition for five soil types (two Luvisols, an Alisol, an Acrisol and a Ferralsol) with heavy textures (silty clay loam, silty clay and clay) derived separately from loess deposits, quaternary red clays and basalt in central-south China. Rainfall simulations were performed at two rainfall intensities (45 and 90mmh -1 ) and lasted one hour after runoff generation. Runoff coefficient, sediment concentration, sediment yield rate and sediment effective size distribution were determined at 3-min intervals. Runoff temporal variations were similar at the high rainfall intensity, but exhibited a remarkable difference at the low rainfall intensity among soil types except for tropical Ferralsol. Illite was positively correlated with runoff coefficient (p<0.05). Rainfall intensity significantly contributed to the erosional process (p<0.001). Sediment concentration and yield rate were the smallest for the tropical Ferralsol and sediment concentration was the largest for the temperate Luvisol. The regimes (transport and detachment) limiting erosion varied under the interaction of rainfall characteristics (intensity and duration) and soil types, with amorphous iron oxides and bulk density jointly enhancing soil resistance to erosive forces (Adj-R 2 >88%, p<0.001). Sediment size was dominated by <0.1mm size fraction for the Luvisols and bimodally distributed with the peaks at <0.1mm and 1-0.5mm size for the other soil types. Exchangeable sodium decreased sediment size while rainfall intensity and clay content increased it (Adj-R 2 =96%, p<0.01). These results allow to better understand the climate effect on erosion processes at the spatial-temporal scale from the perspective of soil properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Deep subsurface drip irrigation using coal-bed sodic water: part I. water and solute movement

USGS Publications Warehouse

Bern, Carleton R.; Breit, George N.; Healy, Richard W.; Zupancic, John W.; Hammack, Richard

2013-01-01

Water co-produced with coal-bed methane (CBM) in the semi-arid Powder River Basin of Wyoming and Montana commonly has relatively low salinity and high sodium adsorption ratios that can degrade soil permeability where used for irrigation. Nevertheless, a desire to derive beneficial use from the water and a need to dispose of large volumes of it have motivated the design of a deep subsurface drip irrigation (SDI) system capable of utilizing that water. Drip tubing is buried 92 cm deep and irrigates at a relatively constant rate year-round, while evapotranspiration by the alfalfa and grass crops grown is seasonal. We use field data from two sites and computer simulations of unsaturated flow to understand water and solute movements in the SDI fields. Combined irrigation and precipitation exceed potential evapotranspiration by 300-480 mm annually. Initially, excess water contributes to increased storage in the unsaturated zone, and then drainage causes cyclical rises in the water table beneath the fields. Native chloride and nitrate below 200 cm depth are leached by the drainage. Some CBM water moves upward from the drip tubing, drawn by drier conditions above. Chloride from CBM water accumulates there as root uptake removes the water. Year over year accumulations indicated by computer simulations illustrate that infiltration of precipitation water from the surface only partially leaches such accumulations away. Field data show that 7% and 27% of added chloride has accumulated above the drip tubing in an alfalfa and grass field, respectively, following 6 years of irrigation. Maximum chloride concentrations in the alfalfa field are around 45 cm depth but reach the surface in parts of the grass field, illustrating differences driven by crop physiology. Deep SDI offers a means of utilizing marginal quality irrigation waters and managing the accumulation of their associated solutes in the crop rooting zone.

A Rain Taxonomy for Degraded Visual Environment Mitigation

NASA Technical Reports Server (NTRS)

Gatlin, P. N.; Petersen, W. A.

2018-01-01

This Technical Memorandum (TM) provides a description of a rainfall taxonomy that defines the detailed characteristics of naturally occurring rainfall. The taxonomy is based on raindrop size measurements collected around the globe and encompasses several different climate types. Included in this TM is a description of these rainfall observations, an explanation of methods used to process those data, and resultant metrics comprising the rain taxonomy database. Each of the categories in the rain taxonomy are characterized by a unique set of raindrop sizes that can be used in simulations of electromagnetic wave propagation through a rain medium.

Evaluating the impacts of cumulus, land surface and ocean surface schemes on summertime rainfall simulations over East-to-southeast Asia and the western north Pacific by RegCM4

NASA Astrophysics Data System (ADS)

Li, Yu-Bin; Tam, Chi-Yung; Huang, Wan-Ru; Cheung, Kevin K. W.; Gao, Zhiqiu

2016-04-01

This study evaluates the sensitivity of summertime rainfall simulations over East-to-southeast Asia and the western north Pacific in the regional climate model version 4 (RegCM4) to cumulus (including Grell with Arakawa-Schubert type closure, Grell with Fritsch-Chappell type closure, and Emanuel), land surface (Biosphere-atmosphere transfer scheme or BATS, and the community land model or CLM) and ocean surface (referred to as Zeng1, Zeng2 and BATS1e in the model) schemes by running the model with different combinations of these parameterization packages. For each of these experiments, ensemble integration of the model was carried out in the extended boreal summer of May-October from 1998 to 2007. The simulated spatial distribution, intensity and inter-annual variation of the precipitation, latent heat flux, position of the subtropical high and tropical cyclone genesis patterns from these numerical experiments were analyzed. Examinations show that the combination of Emanuel, CLM and Zeng2 (E-C-Z2) yields the best overall results, consistent with the fact that physical mechanisms considered in E-C-Z2 tend to be more comprehensive in comparison with the others. Additionally, the rainfall quantity is found very sensitive to sea surface roughness length, and the reduction of the roughness length constant (from 2 × 10-4 to 5 × 10-5 m) in our modified BATS1e mitigates the drastic overestimation of latent heat flux and rainfall, and is therefore preferable to the default value for simulations in the western north Pacific region in RegCM4.

Identification of key climatic factors regulating the transport of pesticides in leaching and to tile drains.

PubMed

Nolan, Bernard T; Dubus, Igor G; Surdyk, Nicolas; Fowler, Hayley J; Burton, Aidan; Hollis, John M; Reichenberger, Stefan; Jarvis, Nicholas J

2008-09-01

Key climatic factors influencing the transport of pesticides to drains and to depth were identified. Climatic characteristics such as the timing of rainfall in relation to pesticide application may be more critical than average annual temperature and rainfall. The fate of three pesticides was simulated in nine contrasting soil types for two seasons, five application dates and six synthetic weather data series using the MACRO model, and predicted cumulative pesticide loads were analysed using statistical methods. Classification trees and Pearson correlations indicated that simulated losses in excess of 75th percentile values (0.046 mg m(-2) for leaching, 0.042 mg m(-2) for drainage) generally occurred with large rainfall events following autumn application on clay soils, for both leaching and drainage scenarios. The amount and timing of winter rainfall were important factors, whatever the application period, and these interacted strongly with soil texture and pesticide mobility and persistence. Winter rainfall primarily influenced losses of less mobile and more persistent compounds, while short-term rainfall and temperature controlled leaching of the more mobile pesticides. Numerous climatic characteristics influenced pesticide loss, including the amount of precipitation as well as the timing of rainfall and extreme events in relation to application date. Information regarding the relative influence of the climatic characteristics evaluated here can support the development of a climatic zonation for European-scale risk assessment for pesticide fate.

Estimation of Throughfall and Stemflow Bacterial Flux in a Subtropical Oak-Cedar Forest

NASA Astrophysics Data System (ADS)

Bittar, Thais B.; Pound, Preston; Whitetree, Ansley; Moore, L. Dean; Van Stan, John T.

2018-02-01

Transport pathways of microbes between ecosystem spheres (atmosphere, phyllosphere, and pedosphere) represent major fluxes in nutrient cycles and have the potential to affect microbially mediated biogeochemical processes. Novel data on bacterial fluxes from the phyllosphere to the pedosphere during rainfall via throughfall (rain dripping from/through the canopy) and stemflow (rain funneled down tree stems) are reported. Bacterial concentrations were quantified using flow cytometry and validated with quantitative polymerase chain reaction assays in rainfall samples from an oak-cedar forest in coastal Georgia (southeastern U.S.). Bacteria concentrations (cells mL-1) and storm-normalized fluxes (cells m-2 h-1, cells m-2 mm-1) were greater for cedar versus oak. Total bacterial flux was 1.5 × 1016 cells ha-1 yr-1. These previously unexamined bacterial fluxes are interpreted in the context of major elemental pools and fluxes in forests and could represent inoculum-level sources of bacteria (if alive), and organic matter and inorganic solute inputs (if lysed) to soils.

Convective Systems over the South China Sea: Cloud-Resolving Model Simulations.

NASA Astrophysics Data System (ADS)

Tao, W.-K.; Shie, C.-L.; Simpson, J.; Braun, S.; Johnson, R. H.; Ciesielski, P. E.

2003-12-01

The two-dimensional version of the Goddard Cumulus Ensemble (GCE) model is used to simulate two South China Sea Monsoon Experiment (SCSMEX) convective periods [18 26 May (prior to and during the monsoon onset) and 2 11 June (after the onset of the monsoon) 1998]. Observed large-scale advective tendencies for potential temperature, water vapor mixing ratio, and horizontal momentum are used as the main forcing in governing the GCE model in a semiprognostic manner. The June SCSMEX case has stronger forcing in both temperature and water vapor, stronger low-level vertical shear of the horizontal wind, and larger convective available potential energy (CAPE).The temporal variation of the model-simulated rainfall, time- and domain-averaged heating, and moisture budgets compares well to those diagnostically determined from soundings. However, the model results have a higher temporal variability. The model underestimates the rainfall by 17% to 20% compared to that based on soundings. The GCE model-simulated rainfall for June is in very good agreement with the Tropical Rainfall Measuring Mission (TRMM), precipitation radar (PR), and the Global Precipitation Climatology Project (GPCP). Overall, the model agrees better with observations for the June case rather than the May case.The model-simulated energy budgets indicate that the two largest terms for both cases are net condensation (heating/drying) and imposed large-scale forcing (cooling/moistening). These two terms are opposite in sign, however. The model results also show that there are more latent heat fluxes for the May case. However, more rainfall is simulated for the June case. Net radiation (solar heating and longwave cooling) are about 34% and 25%, respectively, of the net condensation (condensation minus evaporation) for the May and June cases. Sensible heat fluxes do not contribute to rainfall in either of the SCSMEX cases. Two types of organized convective systems, unicell (May case) and multicell (June case), are simulated by the model. They are determined by the observed mean U wind shear (unidirectional versus reverse shear profiles above midlevels).Several sensitivity tests are performed to examine the impact of the radiation, microphysics, and large-scale mean horizontal wind on the organization and intensity of the SCSMEX convective systems.

Development of in vitro models to demonstrate the ability of PecSys®, an in situ nasal gelling technology, to reduce nasal run-off and drip

PubMed Central

2013-01-01

Many of the increasing number of intranasal products available for either local or systemic action can be considered sub-optimal, most notably where nasal drip or run-off give rise to discomfort/tolerability issues or reduced/variable efficacy. PecSys, an in situ gelling technology, contains low methoxy (LM) pectin which gels due to interaction with calcium ions present in nasal fluid. PecSys is designed to spray readily, only forming a gel on contact with the mucosal surface. The present study employed two in vitro models to confirm that gelling translates into a reduced potential for drip/run-off: (i) Using an inclined TLC plate treated with a simulated nasal electrolyte solution (SNES), mean drip length [±SD, n = 10] was consistently much shorter for PecSys (1.5 ± 0.4 cm) than non-gelling control (5.8 ± 1.6 cm); (ii) When PecSys was sprayed into a human nasal cavity cast model coated with a substrate containing a physiologically relevant concentration of calcium, PecSys solution was retained at the site of initial deposition with minimal redistribution, and no evidence of run-off/drip anteriorly or down the throat. In contrast, non-gelling control was significantly more mobile and consistently redistributed with run-off towards the throat. Conclusion In both models PecSys significantly reduced the potential for run-off/drip ensuring that more solution remained at the deposition site. In vivo, this enhancement of retention will provide optimum patient acceptability, modulate drug absorption and maximize the ability of drugs to be absorbed across the nasal mucosa and thus reduce variability in drug delivery. PMID:22803832

Uncertainty based modeling of rainfall-runoff: Combined differential evolution adaptive Metropolis (DREAM) and K-means clustering

NASA Astrophysics Data System (ADS)

Zahmatkesh, Zahra; Karamouz, Mohammad; Nazif, Sara

2015-09-01

Simulation of rainfall-runoff process in urban areas is of great importance considering the consequences and damages of extreme runoff events and floods. The first issue in flood hazard analysis is rainfall simulation. Large scale climate signals have been proved to be effective in rainfall simulation and prediction. In this study, an integrated scheme is developed for rainfall-runoff modeling considering different sources of uncertainty. This scheme includes three main steps of rainfall forecasting, rainfall-runoff simulation and future runoff prediction. In the first step, data driven models are developed and used to forecast rainfall using large scale climate signals as rainfall predictors. Due to high effect of different sources of uncertainty on the output of hydrologic models, in the second step uncertainty associated with input data, model parameters and model structure is incorporated in rainfall-runoff modeling and simulation. Three rainfall-runoff simulation models are developed for consideration of model conceptual (structural) uncertainty in real time runoff forecasting. To analyze the uncertainty of the model structure, streamflows generated by alternative rainfall-runoff models are combined, through developing a weighting method based on K-means clustering. Model parameters and input uncertainty are investigated using an adaptive Markov Chain Monte Carlo method. Finally, calibrated rainfall-runoff models are driven using the forecasted rainfall to predict future runoff for the watershed. The proposed scheme is employed in the case study of the Bronx River watershed, New York City. Results of uncertainty analysis of rainfall-runoff modeling reveal that simultaneous estimation of model parameters and input uncertainty significantly changes the probability distribution of the model parameters. It is also observed that by combining the outputs of the hydrological models using the proposed clustering scheme, the accuracy of runoff simulation in the watershed is remarkably improved up to 50% in comparison to the simulations by the individual models. Results indicate that the developed methodology not only provides reliable tools for rainfall and runoff modeling, but also adequate time for incorporating required mitigation measures in dealing with potentially extreme runoff events and flood hazard. Results of this study can be used in identification of the main factors affecting flood hazard analysis.

Effect of rainfall simulator and plot scale on overland flow and phosphorus transport.

PubMed

Sharpley, Andrew; Kleinman, Peter

2003-01-01

Rainfall simulation experiments are widely used to study erosion and contaminant transport in overland flow. We investigated the use of two rainfall simulators designed to rain on 2-m-long (2-m2) and 10.7-m-long (32.6-m2) plots to estimate overland flow and phosphorus (P) transport in comparison with watershed-scale data. Simulated rainfall (75 mm h(-1)) generated more overland flow from 2-m-long (20 L m2) than from 10.7-m-long (10 L m2) plots established in grass, no-till corn (Zea mays L.), and recently tilled fields, because a relatively greater area of the smaller plots became saturated (>75% of area) during rainfall compared with large plots (<75% area). Although average concentrations of dissolved reactive phosphorus (DRP) in overland flow were greater from 2-m-long (0.50 mg L(-1)) than 10.7-m-long (0.35 mg L(-1)) plots, the relationship between DRP and Mehlich-3 soil P (as defined by regression slope) was similar for both plots and for published watershed data (0.0022 for grassed, 0.0036 for no-till, and 0.0112 for tilled sites). Conversely, sediment, particulate phosphorus (PP), and total phosphorus (TP) concentrations and selective transport of soil fines (<2 microm) were significantly lower from 2- than 10.7-m-long plots. However, slopes of the logarithmic regression between P enrichment ratio and sediment discharge were similar (0.281-0.301) for 2- and 10.7-m-long plots, and published watershed data. While concentrations and loads of P change with plot scales, processes governing DRP and PP transport in overland flow are consistent, supporting the limited use of small plots and rainfall simulators to assess the relationship between soil P and overland flow P as a function of soil type and management.

Influence of land use on rainfall simulation results in the Souss basin, Morocco

NASA Astrophysics Data System (ADS)

Peter, Klaus Daniel; Ries, Johannes B.; Hssaine, Ali Ait

2013-04-01

Situated between the High and Anti-Atlas, the Souss basin is characterized by a dynamic land use change. It is one of the fastest growing agricultural regions of Morocco. Traditional mixed agriculture is replaced by extensive plantations of citrus fruits, bananas and vegetables in monocropping, mainly for the European market. For the implementation of the land use change and further expansion of the plantations into marginal land which was former unsuitable for agriculture, land levelling by heavy machinery is used to plane the fields and close the widespread gullies. These gully systems are cutting deep between the plantations and other arable land. Their development started already over 400 years ago with the introduction of sugar production. Heavy rainfall events lead to further strong soil and gully erosion in this with 200 mm mean annual precipitation normally arid region. Gullies are cutting into the arable land or are re-excavating their old stream courses. On the test sites around the city of Taroudant, a total of 122 rainfall simulations were conducted to analyze the susceptibility of soils to surface runoff and soil erosion under different land use. A small portable nozzle rainfall simulator is used for the rainfall simulation experiments, quantifying runoff and erosion rates on micro-plots with a size of 0.28 m2. A motor pump boosts the water regulated by a flow metre into the commercial full cone nozzle at a height of 2 m. The rainfall intensity is maintained at about 40 mm h-1 for each of the 30 min lasting experiments. Ten categories of land use are classified for different stages of levelling, fallow land, cultivation and rangeland. Results show that mean runoff coefficients and mean sediment loads are significantly higher (1.4 and 3.5 times respectively) on levelled study sites compared to undisturbed sites. However, the runoff coefficients of all land use types are relatively equal and reach high median coefficients from 39 to 56 %. Only the rainfall simulations underneath mandarin trees in a plantation show with 10 % low coefficients. The results are stronger differentiated for the sediment loads. On levelled areas, the simulations reach median sediment loads of 41 and 61 g m-2 respectively. In spite of high runoff coefficients, the lowest sediment loads of around 4.5 g m-2 are measured on old fallow land (>5 y.) and rangeland which are both protected by biological crusts. The same low result is found on the mandarin plantation. On other younger fallow land (1-2, 2-5 y.) as well as on stone covered badlands and sundry anthropogenic influenced soils medium soil losses between 18 and 25 g m-2 are reached. On sparsely vegetated grain fields, soil erosion is because of initiated crusting despite lower runoff coefficients with 30 g m-2 still high. Land-levelling measures have the greatest influence on rainfall simulation results. Although runoff coefficients on almost all land use types are similar, clear differences of soil erosion due to different land use can be identified.

Simulating transport of nitrogen and phosphorus in a Cambisol after natural and simulated intense rainfall.

PubMed

Kaufmann, Vander; Pinheiro, Adilson; Castro, Nilza Maria dos Reis

2014-05-01

Intense rainfall adversely affects agricultural areas, causing transport of pollutants. Physically-based hydrological models to simulate flows of water and chemical substances can be used to help decision-makers adopt measures which reduce such problems. The purpose of this paper is to evaluate the performance of SWAP and ANIMO models for simulating transport of water, nitrate and phosphorus nutrients, during intense rainfall events generated by a simulator, and during natural rainfall, on a volumetric drainage lysimeter. The models were calibrated and verified using daily time series and simulated rainfall measured at 10-minute intervals. For daily time-intervals, the Nash-Sutcliffe coefficient was 0.865 for the calibration period and 0.805 for verification. Under simulated rainfall, these coefficients were greater than 0.56. The pattern of both nitrate and phosphate concentrations in daily drainage flow under simulated rainfall was acceptably reproduced by the ANIMO model. In the simulated rainfall, loads of nitrate transported in surface runoff varied between 0.08 and 8.46 kg ha(-1), and in drainage form the lysimeter, between 2.44 and 112.57 kg ha(-1). In the case of phosphate, the loads transported in surface runoff varied between 0.002 and 0.504 kg ha(-1), and in drainage, between 0.005 and 1.107 kg ha(-1). The use of the two models SWAP and ANIMO shows the magnitudes of nitrogen and phosphorus fluxes transported by natural and simulated intense rainfall in an agricultural area with different soil management procedures, as required by decision makers. Copyright © 2014 Elsevier B.V. All rights reserved.

Evaluation of Surface Runoff Generation Processes Using a Rainfall Simulator: A Small Scale Laboratory Experiment

NASA Astrophysics Data System (ADS)

Danáčová, Michaela; Valent, Peter; Výleta, Roman

2017-12-01

Nowadays, rainfall simulators are being used by many researchers in field or laboratory experiments. The main objective of most of these experiments is to better understand the underlying runoff generation processes, and to use the results in the process of calibration and validation of hydrological models. Many research groups have assembled their own rainfall simulators, which comply with their understanding of rainfall processes, and the requirements of their experiments. Most often, the existing rainfall simulators differ mainly in the size of the irrigated area, and the way they generate rain drops. They can be characterized by the accuracy, with which they produce a rainfall of a given intensity, the size of the irrigated area, and the rain drop generating mechanism. Rainfall simulation experiments can provide valuable information about the genesis of surface runoff, infiltration of water into soil and rainfall erodibility. Apart from the impact of physical properties of soil, its moisture and compaction on the generation of surface runoff and the amount of eroded particles, some studies also investigate the impact of vegetation cover of the whole area of interest. In this study, the rainfall simulator was used to simulate the impact of the slope gradient of the irrigated area on the amount of generated runoff and sediment yield. In order to eliminate the impact of external factors and to improve the reproducibility of the initial conditions, the experiments were conducted in laboratory conditions. The laboratory experiments were carried out using a commercial rainfall simulator, which was connected to an external peristaltic pump. The pump maintained a constant and adjustable inflow of water, which enabled to overcome the maximum volume of simulated precipitation of 2.3 l, given by the construction of the rainfall simulator, while maintaining constant characteristics of the simulated precipitation. In this study a 12-minute rainfall with a constant intensity of 5 mm/min was used to irrigate a corrupted soil sample. The experiment was undertaken for several different slopes, under the condition of no vegetation cover. The results of the rainfall simulation experiment complied with the expectations of a strong relationship between the slope gradient, and the amount of surface runoff generated. The experiments with higher slope gradients were characterised by larger volumes of surface runoff generated, and by shorter times after which it occurred. The experiments with rainfall simulators in both laboratory and field conditions play an important role in better understanding of runoff generation processes. The results of such small scale experiments could be used to estimate some of the parameters of complex hydrological models, which are used to model rainfall-runoff and erosion processes at catchment scale.

How is overland flow produced under intermittent rain? An analysis using plot-scale rainfall simulation on dryland soils

NASA Astrophysics Data System (ADS)

Dunkerley, David

2018-01-01

The characteristic intermittency of rainfall includes temporary cessations (hiatuses), as well as periods of very low intensity within more intense events. To understand how these characteristics of rainfall affect overland flow production, rainfall simulations involving repeated cycles of on-off intermittency were carried out on dryland soils in arid western New South Wales, Australia. Periods of rain (10 mm/h) and no-rain were applied in alternation with cycle times from 3 min to 25 min, in experiments lasting 1-1.5 h. Results showed that intermittency could delay the onset of runoff by more than 30 min, reduce the runoff ratio, reduce the peak runoff rate, and reduce the apparent event infiltration rate by 30-45%. When hiatuses in rainfall were longer than 15-20 min, runoff that had resulted from prior rain ceased completely before the recommencement of rain. Results demonstrate that if rainfall intermittency is not accounted for, estimates of infiltrability based on runoff plot data can be systematically in error. Despite the use of intermittent rain, the episodic occurrence of runoff could be predicted successfully by fitting multiple affine Horton infiltration equations, whose changing f0 and Kf coefficients, but uniform values of fc, reflected the redistribution of soil moisture and the change in the infiltrability f during hiatuses in rainfall. The value of fc varied little among the fitted equations, so constituting an affine set of relationships. This new approach provides an alternative to the use of steady-state methods that are common in rainfall simulation experiments and which typically yield only an estimate of fc. The new field results confirm that intermittency affects infiltration and runoff depths and timing at plot scale and on intra-event timescales. Additional work on other soil types, and at other spatial and temporal scales, is needed to test the generality of these findings.

Rainfall simulation experiments in the Southwestern USA using the Walnut Gulch rainfall simulator

USDA-ARS?s Scientific Manuscript database

The dataset contains hydrological, erosion, vegetation, ground cover, and other supplementary information from 272 rainfall simulation experiments conducted on 23 semi-arid rangeland locations in Arizona and Nevada between 2002 and 2013. On 30% of the plots simulations were conducted up to five time...

Simulated sensitivity of African terrestrial ecosystem photosynthesis to rainfall frequency, intensity, and rainy season length

NASA Astrophysics Data System (ADS)

Guan, Kaiyu; Good, Stephen P.; Caylor, Kelly K.; Medvigy, David; Pan, Ming; Wood, Eric F.; Sato, Hisashi; Biasutti, Michela; Chen, Min; Ahlström, Anders; Xu, Xiangtao

2018-02-01

There is growing evidence of ongoing changes in the statistics of intra-seasonal rainfall variability over large parts of the world. Changes in annual total rainfall may arise from shifts, either singly or in a combination, of distinctive intra-seasonal characteristics -i.e. rainfall frequency, rainfall intensity, and rainfall seasonality. Understanding how various ecosystems respond to the changes in intra-seasonal rainfall characteristics is critical for predictions of future biome shifts and ecosystem services under climate change, especially for arid and semi-arid ecosystems. Here, we use an advanced dynamic vegetation model (SEIB-DGVM) coupled with a stochastic rainfall/weather simulator to answer the following question: how does the productivity of ecosystems respond to a given percentage change in the total seasonal rainfall that is realized by varying only one of the three rainfall characteristics (rainfall frequency, intensity, and rainy season length)? We conducted ensemble simulations for continental Africa for a realistic range of changes (-20% ~ +20%) in total rainfall amount. We find that the simulated ecosystem productivity (measured by gross primary production, GPP) shows distinctive responses to the intra-seasonal rainfall characteristics. Specifically, increase in rainfall frequency can lead to 28% more GPP increase than the same percentage increase in rainfall intensity; in tropical woodlands, GPP sensitivity to changes in rainy season length is ~4 times larger than to the same percentage changes in rainfall frequency or intensity. In contrast, shifts in the simulated biome distribution are much less sensitive to intra-seasonal rainfall characteristics than they are to total rainfall amount. Our results reveal three major distinctive productivity responses to seasonal rainfall variability—‘chronic water stress’, ‘acute water stress’ and ‘minimum water stress’ - which are respectively associated with three broad spatial patterns of African ecosystem physiognomy, i.e. savannas, woodlands, and tropical forests.

Analysis of water-level fluctuations of the US Highway 90 retention pond, Madison, Florida

USGS Publications Warehouse

Bridges, W.C.

1985-01-01

A closed basin stormwater retention pond, located 1 mile west of Madison, Florida, has a maximum storage capacity of 134.1 acre-feet at the overtopping altitude of 100.2 feet. The maximum observed altitude (July 1982 to March 1984) was 99.52 feet (126.7 acre-feet) on March 28, 1984. This report provides a technique for simulating net monthly change-in-altitude in response to rainfall and evaporation. A regression equation was developed which relates net monthly change in altitude (dependent variable) to rainfall and evaporation (independent variables). Rainfall frequency curves were developed using a log-Pearson Type III distribution of the annual, January through April, June through August, and July monthly rainfall totals for the years 1908-72, 1974, 1976-82. The altitude of the retention pond increased almost 7 feet during the 4-month period January through April 1983. The rainfall total was 35.1 inches, and the recurrence interval exceeded the 100-year January-April rainfall. (USGS)

Using a Gaussian Process Emulator for Data-driven Surrogate Modelling of a Complex Urban Drainage Simulator

NASA Astrophysics Data System (ADS)

Bellos, V.; Mahmoodian, M.; Leopold, U.; Torres-Matallana, J. A.; Schutz, G.; Clemens, F.

2017-12-01

Surrogate models help to decrease the run-time of computationally expensive, detailed models. Recent studies show that Gaussian Process Emulators (GPE) are promising techniques in the field of urban drainage modelling. However, this study focusses on developing a GPE-based surrogate model for later application in Real Time Control (RTC) using input and output time series of a complex simulator. The case study is an urban drainage catchment in Luxembourg. A detailed simulator, implemented in InfoWorks ICM, is used to generate 120 input-output ensembles, from which, 100 are used for training the emulator and 20 for validation of the results. An ensemble of historical rainfall events with 2 hours duration and 10 minutes time steps are considered as the input data. Two example outputs, are selected as wastewater volume and total COD concentration in a storage tank in the network. The results of the emulator are tested with unseen random rainfall events from the ensemble dataset. The emulator is approximately 1000 times faster than the original simulator for this small case study. Whereas the overall patterns of the simulator are matched by the emulator, in some cases the emulator deviates from the simulator. To quantify the accuracy of the emulator in comparison with the original simulator, Nash-Sutcliffe efficiency (NSE) between the emulator and simulator is calculated for unseen rainfall scenarios. The range of NSE for the case of tank volume is from 0.88 to 0.99 with a mean value of 0.95, whereas for COD is from 0.71 to 0.99 with a mean value of 0.92. The emulator is able to predict the tank volume with higher accuracy as the relationship between rainfall intensity and tank volume is linear. For COD, which has a non-linear behaviour, the predictions are less accurate and more uncertain, in particular when rainfall intensity increases. This predictions were improved by including a larger amount of training data for the higher rainfall intensities. It was observed that, the accuracy of the emulator predictions depends on the ensemble training dataset design and the amount of data fed. Finally, more investigation is required to test the possibility of applying this type of fast emulators for model-based RTC applications in which limited number of inputs and outputs are considered in a short prediction horizon.

Uncertainties of flood frequency estimation approaches based on continuous simulation using data resampling

NASA Astrophysics Data System (ADS)

Arnaud, Patrick; Cantet, Philippe; Odry, Jean

2017-11-01

Flood frequency analyses (FFAs) are needed for flood risk management. Many methods exist ranging from classical purely statistical approaches to more complex approaches based on process simulation. The results of these methods are associated with uncertainties that are sometimes difficult to estimate due to the complexity of the approaches or the number of parameters, especially for process simulation. This is the case of the simulation-based FFA approach called SHYREG presented in this paper, in which a rainfall generator is coupled with a simple rainfall-runoff model in an attempt to estimate the uncertainties due to the estimation of the seven parameters needed to estimate flood frequencies. The six parameters of the rainfall generator are mean values, so their theoretical distribution is known and can be used to estimate the generator uncertainties. In contrast, the theoretical distribution of the single hydrological model parameter is unknown; consequently, a bootstrap method is applied to estimate the calibration uncertainties. The propagation of uncertainty from the rainfall generator to the hydrological model is also taken into account. This method is applied to 1112 basins throughout France. Uncertainties coming from the SHYREG method and from purely statistical approaches are compared, and the results are discussed according to the length of the recorded observations, basin size and basin location. Uncertainties of the SHYREG method decrease as the basin size increases or as the length of the recorded flow increases. Moreover, the results show that the confidence intervals of the SHYREG method are relatively small despite the complexity of the method and the number of parameters (seven). This is due to the stability of the parameters and takes into account the dependence of uncertainties due to the rainfall model and the hydrological calibration. Indeed, the uncertainties on the flow quantiles are on the same order of magnitude as those associated with the use of a statistical law with two parameters (here generalised extreme value Type I distribution) and clearly lower than those associated with the use of a three-parameter law (here generalised extreme value Type II distribution). For extreme flood quantiles, the uncertainties are mostly due to the rainfall generator because of the progressive saturation of the hydrological model.

Influence of rainfall microstructure on rainfall interception

NASA Astrophysics Data System (ADS)

Zabret, Katarina; Rakovec, Jože; Mikoš, Matjaž; Šraj, Mojca

2016-04-01

Rainfall interception is part of the hydrological cycle. Precipitation, which hits vegetation, is retained on the leaves and branches, from which it eventually evaporates into the atmosphere (interception) or reaches the ground by dripping from the canopy, falling through the gaps (throughfall) and running down the stems (stemflow). The process is influenced by various meteorological and vegetation parameters. Often neglected meteorological parameter influencing rainfall interception is also rainfall microstructure. Rain is a discrete process consisting of various numbers of individual raindrops with different sizes and velocities. This properties describe rainfall microstructure which is often neglected in hydrological analysis and replaced with rainfall intensity. Throughfall, stemflow and rainfall microstructure have been measured since the beginning of the year 2014 under two tree species (Betula pendula and Pinus nigra) on a study plot in Ljubljana, Slovenia. The preliminary analysis of the influence of rainfall microstructure on rainfall interception has been conducted using three events with different characteristics measured in May 2014. Event A is quite short with low rainfall amount and moderate rainfall intensity, whereas events B and C have similar length but low and high intensities, respectively. Event A was observed on the 1st of May 2014. It was 22 minutes long and delivered 1.2 mm of rainfall. The average rainfall intensity was equal to 3.27 mm/h. The event consisted of 1,350 rain drops with average diameter of 1.517 mm and average velocity of 5.110 m/s. Both Betula pendula and Pinus nigra intercepted similar amount of rainfall, 68 % and 69 %, respectively. Event B was observed in the night from the 7th to 8th of May 2014, it was 16 hours and 18 minutes long, and delivered 4.2 mm of rainfall with average intensity of 0.97 mm/h. There were 39,108 raindrops detected with average diameter of 0.858 mm and average velocity of 3.855 m/s. Betula pendula (23 %) has intercepted significantly less rainfall than Pinus nigra (85%). Event C was also observed in the night time between 11th and 12th of May 2014, it lasted 4 hours and 12 minutes and delivered 34.6 mm of rainfall with an average intensity equal to 8.24 mm/h. During the event 147,236 raindrops with average diameter of 1.020 mm and average velocity of 4.078 m/s were detected. Betula pendula has intercepted only 6 % of rainfall whereas Pinus nigra intercepted majority of rainfall, namely 85 %. In case of B. pendula rainfall interception is increasing with higher velocity whereas it is lower for medium diameters than for smaller or larger diameters. Rainfall interception under P. nigra is decreasing with higher velocities and behaving similar as under B. pendula for different diameters but with less obvious difference between diameter classes. We will continue with the measurements and further analysis of several rainfall events will be prepared.

A "simulation chain" to define a Multidisciplinary Decision Support System for landslide risk management in pyroclastic soils

NASA Astrophysics Data System (ADS)

Damiano, E.; Mercogliano, P.; Netti, N.; Olivares, L.

2012-04-01

This paper proposes a Multidisciplinary Decision Support System (MDSS) as an approach to manage rainfall-induced shallow landslides of the flow type (flowslides) in pyroclastic deposits. We stress the need to combine information from the fields of meteorology, geology, hydrology, geotechnics and economics to support the agencies engaged in land monitoring and management. The MDSS consists of a "simulation chain" to link rainfall to effects in terms of infiltration, slope stability and vulnerability. This "simulation chain" was developed at the Euro-Mediterranean Centre for Climate Change (CMCC) (meteorological aspects), at the Geotechnical Laboratory of the Second University of Naples (hydrological and geotechnical aspects) and at the Department of Economics of the University of Naples "Federico II" (economic aspects). The results obtained from the application of this simulation chain in the Cervinara area during eleven years of research allowed in-depth analysis of the mechanisms underlying a flowslide in pyroclastic soil.

Subsurface drip application of alternative fumigants to methyl bromide for controlling nematodes in replanted grapevines.

PubMed

Cabrera, J Alfonso; Wang, Dong; Schneider, Sally M; Hanson, Bradley D

2012-05-01

Many California grape growers use preplant fumigation to ensure uniform and healthy grapevine establishment in replant situations. A field study was conducted to evaluate the performance of subsurface drip-applied chemical alternatives to methyl bromide on plant-parasitic nematodes, plant vigor and fruit yield during the 6 year period following replanting. Subsurface drip fumigation with 1,3-dichloropropene plus chloropicrin and with iodomethane plus chloropicrin had generally similar nematicide activity as methyl bromide in three grape types, while sodium azide was less effective. The combination of 1,3-dichloropropene plus chloropicrin enhanced vine vigor similarly to methyl bromide. However, all plots treated with alternative fumigants produced less fruit yield than methyl bromide over the 4 years of evaluation. Subsurface drip fumigation with alternative chemicals to methyl bromide generally provided adequate management of plant-parasitic nematodes during the vine establishment period. However, further research is required to increase the performance of alternative chemicals against other components of the replant problem, as grape yield in vines grown in the alternative treatments was lower than in methyl bromide. Copyright © 2011 Society of Chemical Industry.

Oil encapsulation in core-shell alginate capsules by inverse gelation II: comparison between dripping techniques using W/O or O/W emulsions.

PubMed

Martins, Evandro; Poncelet, Denis; Rodrigues, Ramila Cristiane; Renard, Denis

2017-09-01

In the first part of this article, it was described an innovative method of oil encapsulation from dripping-inverse gelation using water-in-oil (W/O) emulsions. It was noticed that the method of oil encapsulation was quite different depending on the emulsion type (W/O or oil-in-water (O/W)) used and that the emulsion structure (W/O or O/W) had a high impact on the dripping technique and the capsules characteristics. The objective of this article was to elucidate the differences between the dripping techniques using both emulsions and compare the capsule properties (mechanical resistance and release of actives). The oil encapsulation using O/W emulsions was easier to perform and did not require the use of emulsion destabilisers. However, capsules produced from W/O emulsions were more resistant to compression and showed the slower release of actives over time. The findings detailed here widened the knowledge of the inverse gelation and gave opportunities to develop new techniques of oil encapsulation.

Characterization of rainfall-runoff response and estimation of the effect of wetland restoration on runoff, Heron Lake Basin, southwestern Minnesota, 1991-97

USGS Publications Warehouse

Jones, Perry M.; Winterstein, Thomas A.

2000-01-01

The U.S. Geological Survey (USGS), in cooperation with the Minnesota Department of Natural Resources and the Heron Lake Watershed District, conducted a study to characterize the rainfall-runoff response and to examine the effects of wetland restoration on the rainfall-runoff response within the Heron Lake Basin in southwestern Minnesota. About 93 percent of the land cover in the Heron Lake Basin consists of agricultural lands, consisting almost entirely of row crops, with less than one percent consisting of wetlands. The Hydrological Simulation Program – Fortran (HSPF), Version 10, was calibrated to continuous discharge data and used to characterize rainfall-runoff responses in the Heron Lake Basin between May 1991 and August 1997. Simulation of the Heron Lake Basin was done as a two-step process: (1) simulations of five small subbasins using data from August 1995 through August 1997, and (2) simulations of the two large basins, Jack and Okabena Creek Basins, using data from May 1991 through September 1996. Simulations of the five small subbasins was done to determine basin parameters for the land segments and assess rainfall-runoff response variability in the basin. Simulations of the two larger basins were done to verify the basin parameters and assess rainfall-runoff responses over a larger area and for a longer time period. Best-fit calibrations of the five subbasin simulations indicate that the rainfall-runoff response is uniform throughout the Heron Lake Basin, and 48 percent of the total rainfall for storms becomes direct (surface and interflow) runoff. Rainfall-runoff response variations result from variations in the distribution, intensity, timing, and duration of rainfall; soil moisture; evapotranspiration rates; and the presence of lakes in the basin. In the spring, the amount and distribution of rainfall tends to govern the runoff response. High evapotranspiration rates in the summer result in a depletion of moisture from the soils, substantially affecting the rainfall-runoff relation. Five wetland restoration simulations were run for each of five subbasins using data from August 1995 through August 1997, and for the two larger basins, Jack and Okabena Creek Basins, using data from May 1991 through September 1996. Results from linear regression analysis of total simulated direct runoff and total rainfall data for simulated storms in the wetland-restoration simulations indicate that the portion of total rainfall that becomes runoff will be reduced by 46 percent if 45 percent of current cropland is converted to wetland. The addition of wetlands reduced peak runoff in most of the simulations, but the reduction varied with antecedent soil moisture, the magnitude of the peak flow, and the presence of current wetlands and lakes. Reductions in the simulated total and peak runoff from the Jack Creek Basin for most of the simulated storms were greatest when additional wetlands were simulated in the North Branch Jack Creek or the Upper Jack Creek Subbasins. In the Okabena Creek Basin, reductions in simulated peak runoff for most of the storms were greatest when additional wetlands were simulated in the Lower Okabena Creek Subbasin.

Performance of ICTP's RegCM4 in Simulating the Rainfall Characteristics over the CORDEX-SEA Domain

NASA Astrophysics Data System (ADS)

Neng Liew, Ju; Tangang, Fredolin; Tieh Ngai, Sheau; Chung, Jing Xiang; Narisma, Gemma; Cruz, Faye Abigail; Phan Tan, Van; Thanh, Ngo-Duc; Santisirisomboon, Jerasron; Milindalekha, Jaruthat; Singhruck, Patama; Gunawan, Dodo; Satyaningsih, Ratna; Aldrian, Edvin

2015-04-01

The performance of the RegCM4 in simulating rainfall variations over the Southeast Asia regions was examined. Different combinations of six deep convective parameterization schemes, namely i) Grell scheme with Arakawa-Schubert closure assumption, ii) Grell scheme with Fritch-Chappel closure assumption, iii) Emanuel MIT scheme, iv) mixed scheme with Emanuel MIT scheme over the Ocean and the Grell scheme over the land, v) mixed scheme with Grell scheme over the land and Emanuel MIT scheme over the ocean and (vi) Kuo scheme, and three ocean flux treatments were tested. In order to account for uncertainties among the observation products, four different gridded rainfall products were used for comparison. The simulated climate is generally drier over the equatorial regions and slightly wetter over the mainland Indo-China compare to the observation. However, simulation with MIT cumulus scheme used over the land area consistently produces large amplitude of positive rainfall biases, although it simulates more realistic annual rainfall variations. The simulations are found less sensitive to treatment of ocean fluxes. Although the simulations produced the rainfall climatology well, all of them simulated much stronger interannual variability compare to that of the observed. Nevertheless, the time evolution of the inter-annual variations was well reproduced particularly over the eastern part of maritime continent. Over the mainland Southeast Asia (SEA), unrealistic rainfall anomalies processes were simulated. The lacking of summer season air-sea interaction results in strong oceanic forcings over the regions, leading to positive rainfall anomalies during years with warm ocean temperature anomalies. This incurs much stronger atmospheric forcings on the land surface processes compare to that of the observed. A score ranking system was designed to rank the simulations according to their performance in reproducing different aspects of rainfall characteristics. The result suggests that the simulation with Emanuel MIT convective scheme and BATs land surface scheme produces better collective performance compare to the rest of the simulations.

A Bivariate Mixed Distribution with a Heavy-tailed Component and its Application to Single-site Daily Rainfall Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chao ..; Singh, Vijay P.; Mishra, Ashok K.

2013-02-06

This paper presents an improved brivariate mixed distribution, which is capable of modeling the dependence of daily rainfall from two distinct sources (e.g., rainfall from two stations, two consecutive days, or two instruments such as satellite and rain gauge). The distribution couples an existing framework for building a bivariate mixed distribution, the theory of copulae and a hybrid marginal distribution. Contributions of the improved distribution are twofold. One is the appropriate selection of the bivariate dependence structure from a wider admissible choice (10 candidate copula families). The other is the introduction of a marginal distribution capable of better representing lowmore » to moderate values as well as extremes of daily rainfall. Among several applications of the improved distribution, particularly presented here is its utility for single-site daily rainfall simulation. Rather than simulating rainfall occurrences and amounts separately, the developed generator unifies the two processes by generalizing daily rainfall as a Markov process with autocorrelation described by the improved bivariate mixed distribution. The generator is first tested on a sample station in Texas. Results reveal that the simulated and observed sequences are in good agreement with respect to essential characteristics. Then, extensive simulation experiments are carried out to compare the developed generator with three other alternative models: the conventional two-state Markov chain generator, the transition probability matrix model and the semi-parametric Markov chain model with kernel density estimation for rainfall amounts. Analyses establish that overall the developed generator is capable of reproducing characteristics of historical extreme rainfall events and is apt at extrapolating rare values beyond the upper range of available observed data. Moreover, it automatically captures the persistence of rainfall amounts on consecutive wet days in a relatively natural and easy way. Another interesting observation is that the recognized ‘overdispersion’ problem in daily rainfall simulation ascribes more to the loss of rainfall extremes than the under-representation of first-order persistence. The developed generator appears to be a sound option for daily rainfall simulation, especially in particular hydrologic planning situations when rare rainfall events are of great importance.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, A. Kyle, E-mail: kyle.jones@mdanderson.org

Purpose: To evaluate the sensitivity of the diagnostic radiological index of protection (DRIP), used to quantify the protective value of radioprotective garments, to procedural factors in fluoroscopy in an effort to determine an appropriate set of scatter-mimicking primary beams to be used in measuring the DRIP. Methods: Monte Carlo simulations were performed to determine the shape of the scattered x-ray spectra incident on the operator in different clinical fluoroscopy scenarios, including interventional radiology and interventional cardiology (IC). Two clinical simulations studied the sensitivity of the scattered spectrum to gantry angle and patient size, while technical factors were varied according tomore » measured automatic dose rate control (ADRC) data. Factorial simulations studied the sensitivity of the scattered spectrum to gantry angle, field of view, patient size, and beam quality for constant technical factors. Average energy (E{sub avg}) was the figure of merit used to condense fluence in each energy bin to a single numerical index. Results: Beam quality had the strongest influence on the scattered spectrum in fluoroscopy. Many procedural factors affect the scattered spectrum indirectly through their effect on primary beam quality through ADRC, e.g., gantry angle and patient size. Lateral C-arm rotation, common in IC, increased the energy of the scattered spectrum, regardless of the direction of rotation. The effect of patient size on scattered radiation depended on ADRC characteristics, patient size, and procedure type. Conclusions: The scattered spectrum striking the operator in fluoroscopy is most strongly influenced by primary beam quality, particularly kV. Use cases for protective garments should be classified by typical procedural primary beam qualities, which are governed by the ADRC according to the impacts of patient size, anatomical location, and gantry angle.« less

Sensitivity of the diagnostic radiological index of protection to procedural factors in fluoroscopy.

PubMed

Jones, A Kyle; Pasciak, Alexander S; Wagner, Louis K

2016-07-01

To evaluate the sensitivity of the diagnostic radiological index of protection (DRIP), used to quantify the protective value of radioprotective garments, to procedural factors in fluoroscopy in an effort to determine an appropriate set of scatter-mimicking primary beams to be used in measuring the DRIP. Monte Carlo simulations were performed to determine the shape of the scattered x-ray spectra incident on the operator in different clinical fluoroscopy scenarios, including interventional radiology and interventional cardiology (IC). Two clinical simulations studied the sensitivity of the scattered spectrum to gantry angle and patient size, while technical factors were varied according to measured automatic dose rate control (ADRC) data. Factorial simulations studied the sensitivity of the scattered spectrum to gantry angle, field of view, patient size, and beam quality for constant technical factors. Average energy (Eavg) was the figure of merit used to condense fluence in each energy bin to a single numerical index. Beam quality had the strongest influence on the scattered spectrum in fluoroscopy. Many procedural factors affect the scattered spectrum indirectly through their effect on primary beam quality through ADRC, e.g., gantry angle and patient size. Lateral C-arm rotation, common in IC, increased the energy of the scattered spectrum, regardless of the direction of rotation. The effect of patient size on scattered radiation depended on ADRC characteristics, patient size, and procedure type. The scattered spectrum striking the operator in fluoroscopy is most strongly influenced by primary beam quality, particularly kV. Use cases for protective garments should be classified by typical procedural primary beam qualities, which are governed by the ADRC according to the impacts of patient size, anatomical location, and gantry angle.

On the wind-induced undercatch in rainfall measurement using CFD-based simulations

NASA Astrophysics Data System (ADS)

Colli, Matteo; Lanza, Luca

2016-04-01

The reliability of liquid atmospheric precipitation measurements is a basic requirement since rainfall data represent the fundamental input variables of many scientific applications (hydrologic models, weather forecasting data assimilation, climate change studies, calibration of weather radar, etc.). The scientific community and the National Meteorological Services worldwide are facing the issue of improving the accuracy of precipitation measurements, with an increased focus on retrieving the information at a high temporal resolution. The rainfall intensity is indeed fundamental information for the precise quantification of the markedly time-varying behavior of precipitation events. Environmental conditions have a relevant impact on the rain collection/sensing efficiency. Among other effects, wind is recognized as a major source of underestimation since it reduces the collection efficiency of the catching-type gauges (Nespor and Sevruk, 1999), the most common type of instruments used worldwide in the national observation networks. The collection efficiency is usually obtained by comparing the rainfall amounts measured by the gauge with the reference, which was defined by EN-13798 standard (CEN, 2002) as a gauge placed below the ground level inside a pit. A lot of scatter can be observed for a given wind speed, which is mainly caused by comparability issues among the tested gauges. An additional source of uncertainty is the drops size distribution (DSD) of the rain, which varies on an event-by-event basis. The goal of this study is to understand the role of the physical characteristics of precipitation particles on the wind-induced rainfall underestimation observed for catching-type gauges. To address this issue, a detailed analysis of the flow field in the vicinity of the gauge is conducted using time-averaged computational fluid dynamics (CFD) simulations (Colli et al., 2015). Using a Lagrangian model, which accounts for the hydrodynamic behavior of liquid particles in the atmosphere, droplets trajectories are calculated to obtain the collection efficiency associated with different drop size distribution and varying the wind speed. The main benefit of investigating this error by means of CFD simulations is the possibility to single out the prevailing environmental factors from the instrumental performance of the gauges under analysis. The preliminary analysis shows the variations in the catch efficiency due to the horizontal wind speeds and the DSD. Overall, this study contributes to a better understanding of the environmental sources of uncertainty in rainfall measurements. References: Colli, M., R. Rasmussen, J. M. Theriault, L. G. Lanza, C. B. Baker & J. Kochendorfer (2015) An Improved Trajectory Model to Evaluate the Collection Performance of Snow Gauges. Journal of Applied Meteorology and Climatology, 54, 1826-1836 Nespor, V. and Sevruk, B. (1999). Estimation of wind-induced error of rainfall gauge measurements using a numerical simulation. J. Atmos. Ocean. Tech, 16(4), 450-464. CEN (2002). EN 13798:2002 Hydrometry - Specification for a reference raingauge pit. European Committee for Standardization.

On the use of satellite-based estimates of rainfall temporal distribution to simulate the potential for malaria transmission in rural Africa

NASA Astrophysics Data System (ADS)

Yamana, Teresa K.; Eltahir, Elfatih A. B.

2011-02-01

This paper describes the use of satellite-based estimates of rainfall to force the Hydrology, Entomology and Malaria Transmission Simulator (HYDREMATS), a hydrology-based mechanistic model of malaria transmission. We first examined the temporal resolution of rainfall input required by HYDREMATS. Simulations conducted over Banizoumbou village in Niger showed that for reasonably accurate simulation of mosquito populations, the model requires rainfall data with at least 1 h resolution. We then investigated whether HYDREMATS could be effectively forced by satellite-based estimates of rainfall instead of ground-based observations. The Climate Prediction Center morphing technique (CMORPH) precipitation estimates distributed by the National Oceanic and Atmospheric Administration are available at a 30 min temporal resolution and 8 km spatial resolution. We compared mosquito populations simulated by HYDREMATS when the model is forced by adjusted CMORPH estimates and by ground observations. The results demonstrate that adjusted rainfall estimates from satellites can be used with a mechanistic model to accurately simulate the dynamics of mosquito populations.

The Impact of Solar Arrays on Arid Soil Hydrology: Some Numerical Simulations

NASA Astrophysics Data System (ADS)

Luo, Y.; Berli, M.; Koonce, J.; Shillito, R.; Dijkema, J.; Ghezzehei, T. A.; Yu, Z.

2016-12-01

Hot deserts are prime locations for solar energy generation but also recognized as particularly fragile environments. Minimizing the impact of facility-scale solar installations on desert environments is therefore of increasing concern. This study focuses on the impact of photovoltaic solar arrays on the water balance of arid soil underneath the array. The goal was to explore whether concentrated rainwater infiltration along the solar panel drip lines would lead to deeper infiltration and an increase in soil water storage in the long term. A two-dimensional HYDRUS model was developed to simulate rainwater infiltration into the soil within a photovoltaic solar array. Results indicate that rainwater infiltrates deeper below the drip lines compared to the areas between solar panels but only for coarse textured soil. Finer-textured soils redistribute soil moisture horizontally and the concentrating effect of solar panels on rainwater infiltration appears to be small.

Cellular model for induction of drip loss in meat.

PubMed

Lambert, I H; Nielsen, J H; Andersen, H J; Ørtenblad, N

2001-10-01

Drip loss from porcine muscle (M. longissimus dorsi) contained high concentrations of K(+) ( approximately 135 mM) and organic osmolytes, for example, taurine ( approximately 15 mM), as well as significant amounts of protein ( approximately 125 mg.mL(-1)). Thus, the drip reflects release of intramuscular components. To simulate events taking place at the time of slaughter and leading to release of osmolytes and subsequent formation of drip loss, C2C12 myotubes were exposed to anoxia and reduction in pH (from 7.4 to 6.0). Anoxia and acidification increased the cellular Ca(2+) concentration ([Ca(2+)](i)) at a rate of 22-32 nM.min(-)(1). The anoxia-induced increase in [Ca(2+)](i) was mainly due to influx via sarcolemmal Na(+) channels. As mammalian cells swell and release lysophospholipids during anoxia, C2C12 cells and primary porcine muscle cells were exposed to either hypotonic shock or lysophosphatidylcholine (LPC) and the release of taurine was followed. The swelling-induced taurine efflux was blocked in the presence of the anion channel blocker (DIDS), the 5-lipooxygenase inhibitors (ETH 615-139 and NDGA) but unaffected by the presence of vitamin E. In contrast, the LPC-induced taurine release was unaffected by DIDS but abolished by antioxidants (butylated hydroxytoluene and vitamin E). Thus, stress-induced taurine release from muscles may precede by two different mechanisms, one being 5-lipooxygenase dependent and the other involving generation of reactive oxygen species. A model for the cellular events, preceding formation of drip in meat, is presented.

Using rainfall simulations to understand the relationship between precipitation, soil crust and infiltration in four agricultural soils

NASA Astrophysics Data System (ADS)

Angulo-Martinez, Marta; Alastrué, Juan; Moret-Fernández, David; Beguería, Santiago; López, Mariví; Navas, Ana

2017-04-01

Rainfall simulation experiments were carried out in order to study soil crust formation and its relation with soil infiltration parameters—sorptivity (S) and hydraulic conductivity (K)—on four common agricultural soils with contrasted properties; namely, Cambisol, Gypsisol, Solonchak, and Solonetz. Three different rainfall simulations, replicated three times each of them, were performed over the soils. Prior to rainfall simulations all soils were mechanically tilled with a rototiller to create similar soil surface conditions and homogeneous soils. Rainfall simulation parameters were monitored in real time by a Thies Laser Precipitation Monitor, allowing a complete characterization of simulated rainfall microphysics (drop size and velocity distributions) and integrated variables (accumulated rainfall, intensity and kinetic energy). Once soils dried after the simulations, soil penetration resistance was measured and soil hydraulic parameters, S and K, were estimated using the disc infiltrometry technique. There was little variation in rainfall parameters among simulations. Mean intensity and mean median diameter (D50) varied in simulations 1 ( 0.5 bar), 2 ( 0.8 bar) and 3 ( 1.2 bar) from 26.5 mm h-1 and 0.43 mm (s1) to 40.5 mm h-1 and 0.54 mm (s2) and 41.1 mm h-1 and 0.56 mm for (s3), respectively. Crust formation by soil was explained by D50 and subsequently by the total precipitation amount and the percentage of silt and clay in soil, being Cambisol and Gypsisol the soils that showed more increase in penetration resistance by simulation. All soils showed similar S values by simulations which were explained by rainfall intensity. Different patterns of K were shown by the four soils, which were explained by the combined effect of D50 and intensity, together with soil physico-chemical properties. This study highlights the importance of monitoring all precipitation parameters to determine their effect on different soil processes.

Evaluating the Effect of Rainfall Infiltration on the Slope Stability of T16 tower of Taipei Mao-kong Gondola by Numerical Methods

NASA Astrophysics Data System (ADS)

RUNG, J.

2013-12-01

In this study, a series of rainfall-stability analyses were performed to simulate the failure mechanism and the function of remediation works of the down slope of T-16 tower pier, Mao-Kong gondola (or T-16 Slope) at the hillside of Taipei City using two-dimensional finite element method. The failure mechanism of T-16 Slope was simulated using the rainfall hyetograph of Jang-Mi typhoon in 2008 based on the field investigation data, monitoring data, soil/rock mechanical testing data and detail design plots of remediation works. Eventually, the numerical procedures and various input parameters in the analysis were verified by comparing the numerical results with the field observations. In addition, 48 hrs design rainfalls corresponding to 5, 10, 25 and 50 years return periods were prepared using the 20 years rainfall data of Mu-Zha rainfall observation station, Central Weather Bureau for the rainfall-stability analyses of T-16 Slope to inspect the effect of the compound stabilization works on the overall stability of the slope. At T-16 Slope, without considering the longitudinal and transverse drainages on the ground surface, there totally 4 types of stabilization works were installed to stabilize the slope. From the slope top to the slope toe, the stabilization works of T-16 Slope consists of RC-retaining wall with micro-pile foundation at the up-segment, earth anchor at the up-middle-segment, soil nailing at the middle-segment and retaining pile at the down-segment of the slope. The effect of each individual stabilization work on the slope stability under rainfall condition was examined and evaluated by raising field groundwater level.

Markov modulated Poisson process models incorporating covariates for rainfall intensity.

PubMed

Thayakaran, R; Ramesh, N I

2013-01-01

Time series of rainfall bucket tip times at the Beaufort Park station, Bracknell, in the UK are modelled by a class of Markov modulated Poisson processes (MMPP) which may be thought of as a generalization of the Poisson process. Our main focus in this paper is to investigate the effects of including covariate information into the MMPP model framework on statistical properties. In particular, we look at three types of time-varying covariates namely temperature, sea level pressure, and relative humidity that are thought to be affecting the rainfall arrival process. Maximum likelihood estimation is used to obtain the parameter estimates, and likelihood ratio tests are employed in model comparison. Simulated data from the fitted model are used to make statistical inferences about the accumulated rainfall in the discrete time interval. Variability of the daily Poisson arrival rates is studied.

Infiltration and Runoff Measurements on Steep Burned Hillslopes Using a Rainfall Simulator with Variable Rain Intensities

USGS Publications Warehouse

Kinner, David A.; Moody, John A.

2008-01-01

Multiple rainfall intensities were used in rainfall-simulation experiments designed to investigate the infiltration and runoff from 1-square-meter plots on burned hillslopes covered by an ash layer of varying thickness. The 1-square-meter plots were on north- and south-facing hillslopes in an area burned by the Overland fire northwest of Boulder near Jamestown on the Front Range of Colorado. A single-nozzle, wide-angle, multi-intensity rain simulator was developed to investigate the infiltration and runoff on steep (30- to 40-percent gradient) burned hillslopes covered with ash. The simulated rainfall was evaluated for spatial variability, drop size, and kinetic energy. Fourteen rainfall simulations, at three intensities (about 20 millimeters per hour [mm/h], 35 mm/h, and 50 mm/h), were conducted on four plots. Measurements during and after the simulations included runoff, rainfall, suspended-sediment concentrations, surface ash layer thickness, soil moisture, soil grain size, soil lost on ignition, and plot topography. Runoff discharge reached a steady state within 7 to 26 minutes. Steady infiltration rates with the 50-mm/h application rainfall intensity approached 20?35 mm/h. If these rates are projected to rainfall application intensities used in many studies of burned area runoff production (about 80 mm/h), the steady discharge rates are on the lower end of measurements from other studies. Experiments using multiple rainfall intensities (three) suggest that runoff begins at rainfall intensities around 20 mm/h at the 1-square-meter scale, an observation consistent with a 10-mm/h rainfall intensity threshold needed for runoff initiation that has been reported in the literature.

Application of the diagnostic radiological index of protection to protective garments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pasciak, Alexander S.; Jones, A. Kyle, E-mail: kyle.jones@mdanderson.org; Wagner, Louis K.

2015-02-15

Purpose: Previously, the diagnostic radiological index of protection (DRIP) was proposed as a metric for quantifying the protective value of radioprotective garments. The DRIP is a weighted sum of the percent transmissions of different radiation beams through a garment. Ideally, the beams would represent the anticipated stray radiation encountered during clinical use. However, it is impractical to expect a medical physicist to possess the equipment necessary to accurately measure transmission of scattered radiation. Therefore, as a proof of concept, the authors tested a method that applied the DRIP to clinical practice. Methods: Primary beam qualities used in interventional cardiology andmore » radiology were observed and catalogued. Based on the observed range of beam qualities, five representative clinical primary beam qualities, specified by kV and added filtration, were selected for this evaluation. Monte Carlo simulations were performed using these primary beams as source definitions to generate scattered spectra from the clinical primary beams. Using numerical optimization, ideal scatter mimicking primary beams, specified by kV and added aluminum filtration, were matched to the scattered spectra according to half- and quarter-value layers and spectral shape. To within reasonable approximation, these theoretical scatter-mimicking primary beams were reproduced experimentally in laboratory x ray beams and used to measure transmission through pure lead and protective garments. For this proof of concept, the DRIP for pure lead and the garments was calculated by assigning equal weighting to percent transmission measurements for each of the five beams. Finally, the areal density of lead and garments was measured for consideration alongside the DRIP to assess the protective value of each material for a given weight. Results: The authors identified ideal scatter mimicking primary beams that matched scattered spectra to within 0.01 mm for half- and quarter-value layers in copper and within 5% for the shape function. The corresponding experimental scatter-mimicking primary beams matched the Monte Carlo generated scattered spectra with maximum deviations of 6.8% and 6.6% for half- and quarter-value layers. The measured DRIP for 0.50 mm lead sheet was 2.0, indicating that it transmitted, on average, 2% of incident radiation. The measured DRIP for a lead garment and one lead-alternative garment closely matched that for pure lead of 0.50 mm thickness. The DRIP for other garments was substantially higher than 0.50 mm lead (3.9–5.4), indicating they transmitted about twice as much radiation. When the DRIP was plotted versus areal density, it was clear that, of the garments tested, none were better than lead on a weight-by-weight basis. Conclusions: A method for measuring the DRIP for protective garments using scatter-mimicking primary beams was developed. There was little discernable advantage in protective value per unit weight for lead-alternative versus lead-only garments. Careful consideration must be given to the balance of protection and weight when choosing a lead-alternative protective garment with a lower specified “lead equivalence,” e.g., 0.35 mm. The DRIP has the potential to resolve this dilemma. Reporting the DRIP relative to areal density is an ideal metric for objective comparisons of protective garment performance, considering both protective value in terms of transmission of radiation and garment weight.« less

Development of microwave rainfall retrieval algorithm for climate applications

NASA Astrophysics Data System (ADS)

KIM, J. H.; Shin, D. B.

2014-12-01

With the accumulated satellite datasets for decades, it is possible that satellite-based data could contribute to sustained climate applications. Level-3 products from microwave sensors for climate applications can be obtained from several algorithms. For examples, the Microwave Emission brightness Temperature Histogram (METH) algorithm produces level-3 rainfalls directly, whereas the Goddard profiling (GPROF) algorithm first generates instantaneous rainfalls and then temporal and spatial averaging process leads to level-3 products. The rainfall algorithm developed in this study follows a similar approach to averaging instantaneous rainfalls. However, the algorithm is designed to produce instantaneous rainfalls at an optimal resolution showing reduced non-linearity in brightness temperature (TB)-rain rate(R) relations. It is found that the resolution tends to effectively utilize emission channels whose footprints are relatively larger than those of scattering channels. This algorithm is mainly composed of a-priori databases (DBs) and a Bayesian inversion module. The DB contains massive pairs of simulated microwave TBs and rain rates, obtained by WRF (version 3.4) and RTTOV (version 11.1) simulations. To improve the accuracy and efficiency of retrieval process, data mining technique is additionally considered. The entire DB is classified into eight types based on Köppen climate classification criteria using reanalysis data. Among these sub-DBs, only one sub-DB which presents the most similar physical characteristics is selected by considering the thermodynamics of input data. When the Bayesian inversion is applied to the selected DB, instantaneous rain rate with 6 hours interval is retrieved. The retrieved monthly mean rainfalls are statistically compared with CMAP and GPCP, respectively.

Set-up and calibration of an outdoor nozzle-type rainfall simulator for soil erosion studies at the Masse experimental station (central Italy)

NASA Astrophysics Data System (ADS)

Vergni, Lorenzo; Todisco, Francesca

2016-04-01

This contribution describes the technical characteristics and the preliminary calibration of a rainfall simulator recently installed by the Department of Agricultural, Food and Environmental Sciences (Perugia University) at the Masse experimental station located 20 km south of Perugia, in the region of Umbria (central Italy). The site includes some USLE plots of different length λ = 11 and 22 m and width w = 2, 4 and 8 m, oriented parallel to a 16 % slope and kept free of vegetation by frequent ploughing. Since 2008, the station enabled to collect data from more than 80 erosive events, that were mainly used to investigate the relationship between rainfall characteristics and soil loss. The relevant soil loss variability that characterizes erosive storm events with similar overall characteristics (duration and/or depth) can be explained by the different rainfall profile of erosive storms and by the different antecedent soil aggregate stability. To analyse in more detail these aspects, recently, the Masse experimental station has been equipped with a semi-portable rainfall simulator placed over two micro-plots of 1x1 m each, having the same topographic and pedologic conditions of the adjacent USLE plots. The rainfall simulator consists of four full-cone spray nozzles for each micro-plot, placed at the angles of a 0.18-m square, centred over the plot at a height of 2.7 m above the ground. The operating pressure is regulated by pressure regulating valves and checked by pressure gauges mounted in correspondence of each nozzle. An electronic control unit regulates the start and stop of the inlet solenoid valves. A range of rainfall intensities can be achieved, by activating different combinations of nozzles (15 different intensities) also during the same simulation trial. The particular design of the plots allows to collect separately the runoff volume deriving from the plots and the water volume fallen outside of the plot. In this way it is possible to derive, by difference, the actual infiltration volume. The experiments are carried out simultaneously on the two adjacent micro-plots. In particular, this contribution reports the results of the first experimental trials aimed to assess the uniformity attainable by single nozzles and its reproducibility (between plots and in time). The interferences between adjacent nozzles (when they work simultaneously) were also evaluated.

Influence of Madden-Julian Oscillation (MJO) on Rainfall Variability over West Africa at Intraseasonal Timescale

NASA Astrophysics Data System (ADS)

Niang, C.

2015-12-01

Intraseasonal variability of rainfall over West Africa plays a significant role in the economy of the region and is highly linked to agriculture and water resources. This research study aims to investigate the relationship between Madden Julian Oscillation (MJO) and rainfall over West Africa during the boreal summer in the the state-of-the-art Atmospheric Model Intercomparison Project (AMIP) type simulations performed by Atmosphere General Circulation Models (GCMs) forced with prescribed Sea Surface Temperature (SST). It aims to determine the impact of MJO on rainfall and convection over West Africa and identify the dynamical processes which are involved in the state-of-the-art climate simulations. The simulations show in general good skills in capturing its main characteristics as well as its influence on rainfall over West Africa. On the global scale, most models simulated an eastward spatio-temporal propagation of enhanced and suppressed convection similar to the observed. However, over West Africa the MJO signal is weak in few of the models although there is a good coherence in the eastward propagation. The influence on rainfall is well captured in both Sahel and Guinea regions thereby adequately producing the transition between positive and negative rainfall anomalies through the different phases as seen in the observation. Furthermore, the results show that strong active convective phase is clearly associated with the African Easterly Jet (AEJ) but the weak convective phase is associated with a much weaker AEJ particularly over coastal Ghana. In assessing the mechanisms which are involved in the above impacts the convectively equatorial coupled waves (CCEW) are analysed separately. The analysis of the longitudinal propagation of zonal wind at 850hPa and outgoing longwave radiation (OLR) shows that the CCEW are very weak and their extention are very limited beyong West African region. It was found that the westward coupled equatorial Rossby waves are needed to bring out the MJO-convection link over the region and this relationship is well reproduced by all the models. Results also confirmed that it may be possible to predict the anomalous convection over West Africa with a time lead of 15-20 day with regard to Indian Ocean and AMIP simulations performed well in this regard.

Simulation of heavy precipitation episode over eastern Peninsular Malaysia using MM5: sensitivity to cumulus parameterization schemes

NASA Astrophysics Data System (ADS)

Salimun, Ester; Tangang, Fredolin; Juneng, Liew

2010-06-01

A comparative study has been conducted to investigate the skill of four convection parameterization schemes, namely the Anthes-Kuo (AK), the Betts-Miller (BM), the Kain-Fritsch (KF), and the Grell (GR) schemes in the numerical simulation of an extreme precipitation episode over eastern Peninsular Malaysia using the Pennsylvania State University—National Center for Atmospheric Research Center (PSU-NCAR) Fifth Generation Mesoscale Model (MM5). The event is a commonly occurring westward propagating tropical depression weather system during a boreal winter resulting from an interaction between a cold surge and the quasi-stationary Borneo vortex. The model setup and other physical parameterizations are identical in all experiments and hence any difference in the simulation performance could be associated with the cumulus parameterization scheme used. From the predicted rainfall and structure of the storm, it is clear that the BM scheme has an edge over the other schemes. The rainfall intensity and spatial distribution were reasonably well simulated compared to observations. The BM scheme was also better in resolving the horizontal and vertical structures of the storm. Most of the rainfall simulated by the BM simulation was of the convective type. The failure of other schemes (AK, GR and KF) in simulating the event may be attributed to the trigger function, closure assumption, and precipitation scheme. On the other hand, the appropriateness of the BM scheme for this episode may not be generalized for other episodes or convective environments.

Rainfall Data Simulation

Treesearch

T.L. Rogerson

1980-01-01

A simple simulation model to predict rainfall for individual storms in central Arkansas is described. Output includes frequency distribution tables for days between storms and for storm size classes; a storm summary by day number (January 1 = 1 and December 31 = 365) and rainfall amount; and an annual storm summary that includes monthly values for rainfall and number...

Management of irrigation frequency and nitrogen fertilization to mitigate GHG and NO emissions from drip-fertigated crops.

PubMed

Abalos, Diego; Sanchez-Martin, Laura; Garcia-Torres, Lourdes; van Groenigen, Jan Willem; Vallejo, Antonio

2014-08-15

Drip irrigation combined with split application of fertilizer nitrogen (N) dissolved in the irrigation water (i.e. drip fertigation) is commonly considered best management practice for water and nutrient efficiency. As a consequence, its use is becoming widespread. Some of the main factors (water-filled pore space, NH4(+) and NO3(-)) regulating the emissions of greenhouse gases (i.e. N2O, CO2 and CH4) and NO from agroecosystems can easily be manipulated by drip fertigation without yield penalties. In this study, we tested management options to reduce these emissions in a field experiment with a melon (Cucumis melo L.) crop. Treatments included drip irrigation frequency (weekly/daily) and type of N fertilizer (urea/calcium nitrate) applied by fertigation. Crop yield, environmental parameters, soil mineral N concentrations and fluxes of N2O, NO, CH4 and CO2 were measured during 85 days. Fertigation with urea instead of calcium nitrate increased N2O and NO emissions by a factor of 2.4 and 2.9, respectively (P<0.005). Daily irrigation reduced NO emissions by 42% (P<0.005) but increased CO2 emissions by 21% (P<0.05) compared with weekly irrigation. We found no relation between irrigation frequency and N2O emissions. Based on yield-scaled Global Warming Potential as well as NO cumulative emissions, we conclude that weekly fertigation with a NO3(-)-based fertilizer is the best option to combine agronomic productivity with environmental sustainability. Our study shows that adequate management of drip fertigation, while contributing to the attainment of water and food security, may provide an opportunity for climate change mitigation. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of Two Stochastic Daily Rainfall Models and their Ability to Preserve Multi-year Rainfall Variability

NASA Astrophysics Data System (ADS)

Kamal Chowdhury, AFM; Lockart, Natalie; Willgoose, Garry; Kuczera, George; Kiem, Anthony; Parana Manage, Nadeeka

2016-04-01

Stochastic simulation of rainfall is often required in the simulation of streamflow and reservoir levels for water security assessment. As reservoir water levels generally vary on monthly to multi-year timescales, it is important that these rainfall series accurately simulate the multi-year variability. However, the underestimation of multi-year variability is a well-known issue in daily rainfall simulation. Focusing on this issue, we developed a hierarchical Markov Chain (MC) model in a traditional two-part MC-Gamma Distribution modelling structure, but with a new parameterization technique. We used two parameters of first-order MC process (transition probabilities of wet-to-wet and dry-to-dry days) to simulate the wet and dry days, and two parameters of Gamma distribution (mean and standard deviation of wet day rainfall) to simulate wet day rainfall depths. We found that use of deterministic Gamma parameter values results in underestimation of multi-year variability of rainfall depths. Therefore, we calculated the Gamma parameters for each month of each year from the observed data. Then, for each month, we fitted a multi-variate normal distribution to the calculated Gamma parameter values. In the model, we stochastically sampled these two Gamma parameters from the multi-variate normal distribution for each month of each year and used them to generate rainfall depth in wet days using the Gamma distribution. In another study, Mehrotra and Sharma (2007) proposed a semi-parametric Markov model. They also used a first-order MC process for rainfall occurrence simulation. But, the MC parameters were modified by using an additional factor to incorporate the multi-year variability. Generally, the additional factor is analytically derived from the rainfall over a pre-specified past periods (e.g. last 30, 180, or 360 days). They used a non-parametric kernel density process to simulate the wet day rainfall depths. In this study, we have compared the performance of our hierarchical MC model with the semi-parametric model in preserving rainfall variability in daily, monthly, and multi-year scales. To calibrate the parameters of both models and assess their ability to preserve observed statistics, we have used ground based data from 15 raingauge stations around Australia, which consist a wide range of climate zones including coastal, monsoonal, and arid climate characteristics. In preliminary results, both models show comparative performances in preserving the multi-year variability of rainfall depth and occurrence. However, the semi-parametric model shows a tendency of overestimating the mean rainfall depth, while our model shows a tendency of overestimating the number of wet days. We will discuss further the relative merits of the both models for hydrology simulation in the presentation.

A point-infiltration model for estimating runoff from rainfall on small basins in semiarid areas of Wyoming

USGS Publications Warehouse

Rankl, James G.

1990-01-01

A physically based point-infiltration model was developed for computing infiltration of rainfall into soils and the resulting runoff from small basins in Wyoming. The user describes a 'design storm' in terms of average rainfall intensity and storm duration. Information required to compute runoff for the design storm by using the model include (1) soil type and description, and (2) two infiltration parameters and a surface-retention storage parameter. Parameter values are tabulated in the report. Rainfall and runoff data for three ephemeral-stream basins that contain only one type of soil were used to develop the model. Two assumptions were necessary: antecedent soil moisture is some long-term average, and storm rainfall is uniform in both time and space. The infiltration and surface-retention storage parameters were determined for the soil of each basin. Observed rainstorm and runoff data were used to develop a separation curve, or incipient-runoff curve, which distinguishes between runoff and nonrunoff rainfall data. The position of this curve defines the infiltration and surface-retention storage parameters. A procedure for applying the model to basins that contain more than one type of soil was developed using data from 7 of the 10 study basins. For these multiple-soil basins, the incipient-runoff curve defines the infiltration and retention-storage parameters for the soil having the highest runoff potential. Parameters were defined by ranking the soils according to their relative permeabilities and optimizing the position of the incipient-runoff curve by using measured runoff as a control for the fit. Analyses of runoff from multiple-soil basins indicate that the effective contributing area of runoff is less than the drainage area of the basin. In this study, the effective drainage area ranged from 41.6 to 71.1 percent of the total drainage area. Information on effective drainage area is useful in evaluating drainage area as an independent variable in statistical analyses of hydrologic data, such as annual peak frequency distributions and sediment yield.A comparison was made of the sum of the simulated runoff and the sum of the measured runoff for all available records of runoff-producing storms in the 10 study basins. The sums of the simulated runoff ranged from 12.0 percent less than to 23.4 percent more than the sums of the measured runoff. A measure of the standard error of estimate was computed for each data set. These values ranged from 20 to 70 percent of the mean value of the measured runoff. Rainfall-simulator infiltrometer tests were made in two small basins. The amount of water uptake measured by the test in Dugout Creek tributary basin averaged about three times greater than the amount of water uptake computed from rainfall and runoff data. Therefore, infiltrometer data were not used to determine infiltration rates for this study.

RCRA, superfund and EPCRA hotline training module. Introduction to: Drip pads (40 cfr parts 264/265, subpart w) updated July 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-07-01

In 1990, EPA promulgated listings for wastes from wood preserving processes. Many of these wastes are generated by allowing preservative to drip from wood onto concrete pads, called drip pads. To facilitate proper handling of these wastes, EPA developed design and operating standards for drip pads used to manage hazardous wastes. This module explains these standards. It defines a drip pad and summarizes the design and operating standards for drip pads. It describes the relationship between generator accumulation provisions and drip pads.

Modeling water flow and nitrate dynamics in a plastic mulch vegetable cultivation system using HYDRUS-2D

NASA Astrophysics Data System (ADS)

Filipović, Vilim; Romić, Davor; Romić, Marija; Matijević, Lana; Mallmann, Fábio J. K.; Robinson, David A.

2016-04-01

Growing vegetables commercially requires intensive management and involves high irrigation demands and input of agrochemicals. Plastic mulch application in combination with drip irrigation is a common agricultural management technique practiced due to variety of benefits to the crop, mostly vegetable biomass production. However, the use of these techniques can result in various impacts on water and nutrient distribution in underlying soil and consequently affect nutrient leaching towards groundwater resources. The aim of this work is to estimate the effect of plastic mulch cover in combination with drip irrigation on water and nitrate dynamics in soil using HYDRUS-2D model. The field site was located in Croatian costal karst area on a Gleysol (WRB). The experiment was designed according to the split-plot design in three repetitions and was divided into plots with plastic mulch cover (MULCH) and control plots with bare soil (CONT). Each of these plots received applications of three levels of nitrogen fertilizer: 70, 140, and 210 kg per ha. All plots were equipped with drip irrigation and cropped with bell pepper (Capsicum annuum L. cv. Bianca F1). Lysimeters were installed at 90 cm depth in all plots and were used for monitoring the water and nitrate outflow. HYDRUS-2D was used for modeling the water and nitrogen outflow in the MULCH and CONT plots, implementing the proper boundary conditions. HYDRUS-2D simulated results showed good fitting to the field site observed data in both cumulative water and nitrate outflow, with high level of agreement. Water flow simulations produced model efficiency of 0.84 for CONT and 0.56 for MULCH plots, while nitrate simulations showed model efficiency ranging from 0.67 to 0.83 and from 0.70 to 0.93, respectively. Additional simulations were performed with the absence of the lysimeter, revealing faster transport of nitrates below drip line in the CONT plots, mostly because of the increased surface area subjected to precipitation/irrigation due the absence of soil cover. Contrary, in the MULCH plots most of the nitrate applied was still left in the upper soil layer at the end of simulations. Numerical modeling revealed a large influence of plastic mulch cover on water and nutrient outflow and distribution in soil. Results suggest that under this management practice the nitrogen amounts applied via fertigation can be lowered and optimized (higher application frequencies) to reduce possible negative influence of the nitrogen based fertilizer such as leaching of nitrates to groundwater. Keywords: Plastic mulch cover; Vegetable cultivation; Water flow; Nitrate dynamics; HYDRUS-2D

Rainfall Induced Landslides in Puerto Rico (Invited)

NASA Astrophysics Data System (ADS)

Lepore, C.; Kamal, S.; Arnone, E.; Noto, V.; Shanahan, P.; Bras, R. L.

2009-12-01

Landslides are a major geologic hazard in the United States, typically triggered by rainfall, earthquakes, volcanoes and human activity. Rainfall-induced landslides are the most common type in the island of Puerto Rico, with one or two large events per year. We performed an island-wide determination of static landslide susceptibility and hazard assessment as well as dynamic modeling of rainfall-induced shallow landslides in a particular hydrologic basin. Based on statistical analysis of past landslides, we determined that reliable prediction of the susceptibility to landslides is strongly dependent on the resolution of the digital elevation model (DEM) employed and the reliability of the rainfall data. A distributed hydrology model capable of simulating landslides, tRIBS-VEGGIE, has been implemented for the first time in a humid tropical environment like Puerto Rico. The Mameyes basin, located in the Luquillo Experimental Forest in Puerto Rico, was selected for modeling based on the availability of soil, vegetation, topographical, meteorological and historic landslide data. .Application of the model yields a temporal and spatial distribution of predicted rainfall-induced landslides, which is used to predict the dynamic susceptibility of the basin to landslides.

Modelling hydrology of a single bioretention system with HYDRUS-1D.

PubMed

Meng, Yingying; Wang, Huixiao; Chen, Jiangang; Zhang, Shuhan

2014-01-01

A study was carried out on the effectiveness of bioretention systems to abate stormwater using computer simulation. The hydrologic performance was simulated for two bioretention cells using HYDRUS-1D, and the simulation results were verified by field data of nearly four years. Using the validated model, the optimization of design parameters of rainfall return period, filter media depth and type, and surface area was discussed. And the annual hydrologic performance of bioretention systems was further analyzed under the optimized parameters. The study reveals that bioretention systems with underdrains and impervious boundaries do have some detention capability, while their total water retention capability is extremely limited. Better detention capability is noted for smaller rainfall events, deeper filter media, and design storms with a return period smaller than 2 years, and a cost-effective filter media depth is recommended in bioretention design. Better hydrologic effectiveness is achieved with a higher hydraulic conductivity and ratio of the bioretention surface area to the catchment area, and filter media whose conductivity is between the conductivity of loamy sand and sandy loam, and a surface area of 10% of the catchment area is recommended. In the long-term simulation, both infiltration volume and evapotranspiration are critical for the total rainfall treatment in bioretention systems.

Assessing the performance of eight real-time updating models and procedures for the Brosna River

NASA Astrophysics Data System (ADS)

Goswami, M.; O'Connor, K. M.; Bhattarai, K. P.; Shamseldin, A. Y.

2005-10-01

The flow forecasting performance of eight updating models, incorporated in the Galway River Flow Modelling and Forecasting System (GFMFS), was assessed using daily data (rainfall, evaporation and discharge) of the Irish Brosna catchment (1207 km2), considering their one to six days lead-time discharge forecasts. The Perfect Forecast of Input over the Forecast Lead-time scenario was adopted, where required, in place of actual rainfall forecasts. The eight updating models were: (i) the standard linear Auto-Regressive (AR) model, applied to the forecast errors (residuals) of a simulation (non-updating) rainfall-runoff model; (ii) the Neural Network Updating (NNU) model, also using such residuals as input; (iii) the Linear Transfer Function (LTF) model, applied to the simulated and the recently observed discharges; (iv) the Non-linear Auto-Regressive eXogenous-Input Model (NARXM), also a neural network-type structure, but having wide options of using recently observed values of one or more of the three data series, together with non-updated simulated outflows, as inputs; (v) the Parametric Simple Linear Model (PSLM), of LTF-type, using recent rainfall and observed discharge data; (vi) the Parametric Linear perturbation Model (PLPM), also of LTF-type, using recent rainfall and observed discharge data, (vii) n-AR, an AR model applied to the observed discharge series only, as a naïve updating model; and (viii) n-NARXM, a naive form of the NARXM, using only the observed discharge data, excluding exogenous inputs. The five GFMFS simulation (non-updating) models used were the non-parametric and parametric forms of the Simple Linear Model and of the Linear Perturbation Model, the Linearly-Varying Gain Factor Model, the Artificial Neural Network Model, and the conceptual Soil Moisture Accounting and Routing (SMAR) model. As the SMAR model performance was found to be the best among these models, in terms of the Nash-Sutcliffe R2 value, both in calibration and in verification, the simulated outflows of this model only were selected for the subsequent exercise of producing updated discharge forecasts. All the eight forms of updating models for producing lead-time discharge forecasts were found to be capable of producing relatively good lead-1 (1-day ahead) forecasts, with R2 values almost 90% or above. However, for higher lead time forecasts, only three updating models, viz., NARXM, LTF, and NNU, were found to be suitable, with lead-6 values of R2 about 90% or higher. Graphical comparisons were made of the lead-time forecasts for the two largest floods, one in the calibration period and the other in the verification period.

Identification and Functional Analysis of the First Aquaporin from Striped Stem Borer, Chilo suppressalis

PubMed Central

Lu, Ming-Xing; Pan, Dan-Dan; Xu, Jing; Liu, Yang; Wang, Gui-Rong; Du, Yu-Zhou

2018-01-01

Aquaporins are integral membrane proteins some of which form high capacity water-selective channels, promoting water permeation across cell membranes. In this study, we isolated the aquaporin transcript (CsDrip1) of Chilo suppressalis, one of the important rice pests. CsDrip1 included two variants, CsDrip1_v1 and CsDrip1_v2. Although CsDrip1_v2 sequence (>409 bp) was longer than CsDrip1_v1, they possessed the same open reading frame (ORF). Protein structure and topology of CsDrip1 was analyzed using a predicted model, and the results demonstrated the conserved properties of insect water-specific aquaporins, including 6 transmembrane domains, 2 NPA motifs, ar/R constriction region (Phe69, His194, Ser203, and Arg209) and the C-terminal peptide sequence ending in “SYDF.” Our data revealed that the Xenopus oocytes expressing CsDrip1 indicated CsDrip1 could transport water instead of glycerol, trehalose and urea. Further, the transcript of CsDrip1 expressed ubiquitously but differentially in different tissues or organs and developmental stages of C. suppressalis. CsDrip1 mRNA exhibited the highest level of expression within hindgut and the third instar larvae. Regardless of pupae and adults, there were significantly different expression levels of CsDrip1 gene between male and female. Different from at low temperature, the transcript of CsDrip1 in larvae exposed to high temperature was increased significantly. Moreover, the mRNA levels of CsDrip1 in the third instar larvae, the fifth instar larvae, pupae (male and female), and adults (male and female) under different humidities were investigated. However, the mRNA levels of CsDrip1 of only female and male adults were changed remarkably. In conclusions, CsDrip1 plays important roles in maintaining water homeostasis in this important rice pest. PMID:29467668

Temporal rainfall estimation using input data reduction and model inversion

NASA Astrophysics Data System (ADS)

Wright, A. J.; Vrugt, J. A.; Walker, J. P.; Pauwels, V. R. N.

2016-12-01

Floods are devastating natural hazards. To provide accurate, precise and timely flood forecasts there is a need to understand the uncertainties associated with temporal rainfall and model parameters. The estimation of temporal rainfall and model parameter distributions from streamflow observations in complex dynamic catchments adds skill to current areal rainfall estimation methods, allows for the uncertainty of rainfall input to be considered when estimating model parameters and provides the ability to estimate rainfall from poorly gauged catchments. Current methods to estimate temporal rainfall distributions from streamflow are unable to adequately explain and invert complex non-linear hydrologic systems. This study uses the Discrete Wavelet Transform (DWT) to reduce rainfall dimensionality for the catchment of Warwick, Queensland, Australia. The reduction of rainfall to DWT coefficients allows the input rainfall time series to be simultaneously estimated along with model parameters. The estimation process is conducted using multi-chain Markov chain Monte Carlo simulation with the DREAMZS algorithm. The use of a likelihood function that considers both rainfall and streamflow error allows for model parameter and temporal rainfall distributions to be estimated. Estimation of the wavelet approximation coefficients of lower order decomposition structures was able to estimate the most realistic temporal rainfall distributions. These rainfall estimates were all able to simulate streamflow that was superior to the results of a traditional calibration approach. It is shown that the choice of wavelet has a considerable impact on the robustness of the inversion. The results demonstrate that streamflow data contains sufficient information to estimate temporal rainfall and model parameter distributions. The extent and variance of rainfall time series that are able to simulate streamflow that is superior to that simulated by a traditional calibration approach is a demonstration of equifinality. The use of a likelihood function that considers both rainfall and streamflow error combined with the use of the DWT as a model data reduction technique allows the joint inference of hydrologic model parameters along with rainfall.

Drip irrigation research update at NPRL

USDA-ARS?s Scientific Manuscript database

Drip irrigation research has been conducted since 1998 at NPRL. Systems include deep subsurface drip irrigation (SSDI), surface drip irrigation (SDI), and shallow subsurface drip irrigation (S3DI). Results have shown that SDI and S3DI are more economical to install than SSDI. SDI systems have more r...

Capabilities of stochastic rainfall models as data providers for urban hydrology

NASA Astrophysics Data System (ADS)

Haberlandt, Uwe

2017-04-01

For planning of urban drainage systems using hydrological models, long, continuous precipitation series with high temporal resolution are needed. Since observed time series are often too short or not available everywhere, the use of synthetic precipitation is a common alternative. This contribution compares three precipitation models regarding their suitability to provide 5 minute continuous rainfall time series for a) sizing of drainage networks for urban flood protection and b) dimensioning of combined sewage systems for pollution reduction. The rainfall models are a parametric stochastic model (Haberlandt et al., 2008), a non-parametric probabilistic approach (Bárdossy, 1998) and a stochastic downscaling of dynamically simulated rainfall (Berg et al., 2013); all models are operated both as single site and multi-site generators. The models are applied with regionalised parameters assuming that there is no station at the target location. Rainfall and discharge characteristics are utilised for evaluation of the model performance. The simulation results are compared against results obtained from reference rainfall stations not used for parameter estimation. The rainfall simulations are carried out for the federal states of Baden-Württemberg and Lower Saxony in Germany and the discharge simulations for the drainage networks of the cities of Hamburg, Brunswick and Freiburg. Altogether, the results show comparable simulation performance for the three models, good capabilities for single site simulations but low skills for multi-site simulations. Remarkably, there is no significant difference in simulation performance comparing the tasks flood protection with pollution reduction, so the models are finally able to simulate both the extremes and the long term characteristics of rainfall equally well. Bárdossy, A., 1998. Generating precipitation time series using simulated annealing. Wat. Resour. Res., 34(7): 1737-1744. Berg, P., Wagner, S., Kunstmann, H., Schädler, G., 2013. High resolution regional climate model simulations for Germany: part I — validation. Climate Dynamics, 40(1): 401-414. Haberlandt, U., Ebner von Eschenbach, A.-D., Buchwald, I., 2008. A space-time hybrid hourly rainfall model for derived flood frequency analysis. Hydrol. Earth Syst. Sci., 12: 1353-1367.

Assessment of the Weather Research and Forecasting (WRF) model for simulation of extreme rainfall events in the upper Ganga Basin

NASA Astrophysics Data System (ADS)

Chawla, Ila; Osuri, Krishna K.; Mujumdar, Pradeep P.; Niyogi, Dev

2018-02-01

Reliable estimates of extreme rainfall events are necessary for an accurate prediction of floods. Most of the global rainfall products are available at a coarse resolution, rendering them less desirable for extreme rainfall analysis. Therefore, regional mesoscale models such as the advanced research version of the Weather Research and Forecasting (WRF) model are often used to provide rainfall estimates at fine grid spacing. Modelling heavy rainfall events is an enduring challenge, as such events depend on multi-scale interactions, and the model configurations such as grid spacing, physical parameterization and initialization. With this background, the WRF model is implemented in this study to investigate the impact of different processes on extreme rainfall simulation, by considering a representative event that occurred during 15-18 June 2013 over the Ganga Basin in India, which is located at the foothills of the Himalayas. This event is simulated with ensembles involving four different microphysics (MP), two cumulus (CU) parameterizations, two planetary boundary layers (PBLs) and two land surface physics options, as well as different resolutions (grid spacing) within the WRF model. The simulated rainfall is evaluated against the observations from 18 rain gauges and the Tropical Rainfall Measuring Mission Multi-Satellite Precipitation Analysis (TMPA) 3B42RT version 7 data. From the analysis, it should be noted that the choice of MP scheme influences the spatial pattern of rainfall, while the choice of PBL and CU parameterizations influences the magnitude of rainfall in the model simulations. Further, the WRF run with Goddard MP, Mellor-Yamada-Janjic PBL and Betts-Miller-Janjic CU scheme is found to perform best in simulating this heavy rain event. The selected configuration is evaluated for several heavy to extremely heavy rainfall events that occurred across different months of the monsoon season in the region. The model performance improved through incorporation of detailed land surface processes involving prognostic soil moisture evolution in Noah scheme compared to the simple Slab model. To analyse the effect of model grid spacing, two sets of downscaling ratios - (i) 1 : 3, global to regional (G2R) scale and (ii) 1 : 9, global to convection-permitting scale (G2C) - are employed. Results indicate that a higher downscaling ratio (G2C) causes higher variability and consequently large errors in the simulations. Therefore, G2R is adopted as a suitable choice for simulating heavy rainfall event in the present case study. Further, the WRF-simulated rainfall is found to exhibit less bias when compared with the NCEP FiNaL (FNL) reanalysis data.

The Sensitivity of West African Squall Line Water Budgets to Land Cover

NASA Technical Reports Server (NTRS)

Mohr, Karen I.; Baker, R. David; Tao, Wei-Kuo; Famiglietti, James S.; Starr, David OC. (Technical Monitor)

2001-01-01

This study used a two-dimensional coupled land/atmosphere (cloud-resolving) model to investigate the influence of land cover on the water budgets of squall lines in the Sahel. Study simulations used the same initial sounding and one of three different land covers, a sparsely vegetated semi-desert, a grassy savanna, and a dense evergreen broadleaf forest. All simulations began at midnight and ran for 24 hours to capture a full diurnal cycle. In the morning, the latent heat flux, boundary layer mixing ratio, and moist static energy in the boundary layer exhibited notable variations among the three land covers. The broadleaf forest had the highest latent heat flux, the shallowest, moistest, slowest growing boundary layer, and significantly more moist static energy per unit area than the savanna and semi-desert. Although all simulations produced squall lines by early afternoon, the broadleaf forest had the most intense, longest-lived squall lines with 29% more rainfall than the savanna and 37% more than the semi-desert. The sensitivity of the results to vegetation density, initial sounding humidity, and grid resolution was also assessed. There were greater differences in rainfall among land cover types than among simulations of the same land cover with varying amounts of vegetation. Small changes in humidity were equivalent in effect to large changes in land cover, producing large changes in the condensate and rainfall. Decreasing the humidity had a greater effect on rainfall volume than increasing the humidity. Reducing the grid resolution from 1.5 km to 0.5 km decreased the temperature and humidity of the cold pools and increased the rain volume.

Performance of bias corrected MPEG rainfall estimate for rainfall-runoff simulation in the upper Blue Nile Basin, Ethiopia

NASA Astrophysics Data System (ADS)

Worqlul, Abeyou W.; Ayana, Essayas K.; Maathuis, Ben H. P.; MacAlister, Charlotte; Philpot, William D.; Osorio Leyton, Javier M.; Steenhuis, Tammo S.

2018-01-01

In many developing countries and remote areas of important ecosystems, good quality precipitation data are neither available nor readily accessible. Satellite observations and processing algorithms are being extensively used to produce satellite rainfall products (SREs). Nevertheless, these products are prone to systematic errors and need extensive validation before to be usable for streamflow simulations. In this study, we investigated and corrected the bias of Multi-Sensor Precipitation Estimate-Geostationary (MPEG) data. The corrected MPEG dataset was used as input to a semi-distributed hydrological model Hydrologiska Byråns Vattenbalansavdelning (HBV) for simulation of discharge of the Gilgel Abay and Gumara watersheds in the Upper Blue Nile basin, Ethiopia. The result indicated that the MPEG satellite rainfall captured 81% and 78% of the gauged rainfall variability with a consistent bias of underestimating the gauged rainfall by 60%. A linear bias correction applied significantly reduced the bias while maintaining the coefficient of correlation. The simulated flow using bias corrected MPEG SRE resulted in a simulated flow comparable to the gauge rainfall for both watersheds. The study indicated the potential of MPEG SRE in water budget studies after applying a linear bias correction.

Type-segregated aerosol effects on regional monsoon activity: A study using ground-based experiments and model simulations

NASA Astrophysics Data System (ADS)

Vijayakumar, K.; Devara, P. C. S.; Sonbawne, S. M.

2014-12-01

Classification of observed aerosols into key types [e.g., clean-maritime (CM), desert-dust (DD), urban-industrial/biomass-burning (UI/BB), black carbon (BC), organic carbon (OC) and mixed-type aerosols (MA)] would facilitate to infer aerosol sources, effects, and feedback mechanisms, not only to improve the accuracy of satellite retrievals but also to quantify the assessment of aerosol radiative impacts on climate. In this paper, we report the results of a study conducted in this direction, employing a Cimel Sun-sky radiometer at the Indian Institute of Tropical Meteorology (IITM), Pune, India during 2008 and 2009, which represent two successive contrasting monsoon years. The study provided an observational evidence to show that the local sources are subject to heavy loading of absorbing aerosols (dust and black carbon), with strong seasonality closely linked to the monsoon annual rainfall cycle over Pune, a tropical urban station in India. The results revealed the absence of CM aerosols in the pre-monsoon as well as in the monsoon seasons of 2009 as opposed to 2008. Higher loading of dust aerosols is observed in the pre-monsoon and monsoon seasons of 2009; majority may be coated with fine BC aerosols from local emissions, leading to reduction in regional rainfall. Further, significant decrease in coarse-mode AOD and presence of carbonaceous aerosols, affecting the aerosol-cloud interaction and monsoon-rain processes via microphysics and dynamics, is considered responsible for the reduction in rainfall during 2009. Additionally, we discuss how optical depth, contributed by different types of aerosols, influences the distribution of monsoon rainfall over an urban region using the Monitoring Atmospheric Composition and Climate (MACC) aerosol reanalysis. Furthermore, predictions of the Dust REgional Atmospheric Model (DREAM) simulations combined with HYSPLIT (HYbrid Single Particle Lagrangian Integrated Trajectory) cluster model are also discussed in support of the observed features.

Use NU-WRF and GCE Model to Simulate the Precipitation Processes During MC3E Campaign

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Wu, Di; Matsui, Toshi; Li, Xiaowen; Zeng, Xiping; Peter-Lidard, Christa; Hou, Arthur

2012-01-01

One of major CRM approaches to studying precipitation processes is sometimes referred to as "cloud ensemble modeling". This approach allows many clouds of various sizes and stages of their lifecycles to be present at any given simulation time. Large-scale effects derived from observations are imposed into CRMs as forcing, and cyclic lateral boundaries are used. The advantage of this approach is that model results in terms of rainfall and QI and Q2 usually are in good agreement with observations. In addition, the model results provide cloud statistics that represent different types of clouds/cloud systems during their lifetime (life cycle). The large-scale forcing derived from MC3EI will be used to drive GCE model simulations. The model-simulated results will be compared with observations from MC3E. These GCE model-simulated datasets are especially valuable for LH algorithm developers. In addition, the regional scale model with very high-resolution, NASA Unified WRF is also used to real time forecast during the MC3E campaign to ensure that the precipitation and other meteorological forecasts are available to the flight planning team and to interpret the forecast results in terms of proposed flight scenarios. Post Mission simulations are conducted to examine the sensitivity of initial and lateral boundary conditions to cloud and precipitation processes and rainfall. We will compare model results in terms of precipitation and surface rainfall using GCE model and NU-WRF

Methodology for application of field rainfall simulator to revise c-factor database for conditions of the Czech Republic

NASA Astrophysics Data System (ADS)

Neumann, Martin; Dostál, Tomáš; Krása, Josef; Kavka, Petr; Davidová, Tereza; Brant, Václav; Kroulík, Milan; Mistr, Martin; Novotný, Ivan

2016-04-01

The presentation will introduce a methodology of determination of crop and cover management factor (C-faktor) for the universal soil loss equation (USLE) using field rainfall simulator. The aim of the project is to determine the C-factor value for the different phenophases of the main crops of the central-european region, while also taking into account the different agrotechnical methods. By using the field rainfall simulator, it is possible to perform the measurements in specific phenophases, which is otherwise difficult to execute due to the variability and fortuity of the natural rainfall. Due to the number of measurements needed, two identical simulators will be used, operated by two independent teams, with coordinated methodology. The methodology will mainly specify the length of simulation, the rainfall intensity, and the sampling technique. The presentation includes a more detailed account of the methods selected. Due to the wide range of variable crops and soils, it is not possible to execute the measurements for all possible combinations. We therefore decided to perform the measurements for previously selected combinations of soils,crops and agrotechnologies that are the most common in the Czech Republic. During the experiments, the volume of the surface runoff and amount of sediment will be measured in their temporal distribution, as well as several other important parameters. The key values of the 3D matrix of the combinations of the crop, agrotechnique and soil will be determined experimentally. The remaining values will be determined by interpolation or by a model analogy. There are several methods used for C-factor calculation from measured experimental data. Some of these are not suitable to be used considering the type of data gathered. The presentation will discuss the benefits and drawbacks of these methods, as well as the final design of the method used. The problems concerning the selection of a relevant measurement method as well as the final method of simulation and C-factor determination for the gathered data will be discussed in more detail. The presentation was supported by research projects QJ1530181 and SGS14/180/OHK1/3T/11.

Daily Rainfall Simulation Using Climate Variables and Nonhomogeneous Hidden Markov Model

NASA Astrophysics Data System (ADS)

Jung, J.; Kim, H. S.; Joo, H. J.; Han, D.

2017-12-01

Markov chain is an easy method to handle when we compare it with other ones for the rainfall simulation. However, it also has limitations in reflecting seasonal variability of rainfall or change on rainfall patterns caused by climate change. This study applied a Nonhomogeneous Hidden Markov Model(NHMM) to consider these problems. The NHMM compared with a Hidden Markov Model(HMM) for the evaluation of a goodness of the model. First, we chose Gum river basin in Korea to apply the models and collected daily rainfall data from the stations. Also, the climate variables of geopotential height, temperature, zonal wind, and meridional wind date were collected from NCEP/NCAR reanalysis data to consider external factors affecting the rainfall event. We conducted a correlation analysis between rainfall and climate variables then developed a linear regression equation using the climate variables which have high correlation with rainfall. The monthly rainfall was obtained by the regression equation and it became input data of NHMM. Finally, the daily rainfall by NHMM was simulated and we evaluated the goodness of fit and prediction capability of NHMM by comparing with those of HMM. As a result of simulation by HMM, the correlation coefficient and root mean square error of daily/monthly rainfall were 0.2076 and 10.8243/131.1304mm each. In case of NHMM, the correlation coefficient and root mean square error of daily/monthly rainfall were 0.6652 and 10.5112/100.9865mm each. We could verify that the error of daily and monthly rainfall simulated by NHMM was improved by 2.89% and 22.99% compared with HMM. Therefore, it is expected that the results of the study could provide more accurate data for hydrologic analysis. Acknowledgements This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT & Future Planning(2017R1A2B3005695)

Why continuous simulation? The role of antecedent moisture in design flood estimation

NASA Astrophysics Data System (ADS)

Pathiraja, S.; Westra, S.; Sharma, A.

2012-06-01

Continuous simulation for design flood estimation is increasingly becoming a viable alternative to traditional event-based methods. The advantage of continuous simulation approaches is that the catchment moisture state prior to the flood-producing rainfall event is implicitly incorporated within the modeling framework, provided the model has been calibrated and validated to produce reasonable simulations. This contrasts with event-based models in which both information about the expected sequence of rainfall and evaporation preceding the flood-producing rainfall event, as well as catchment storage and infiltration properties, are commonly pooled together into a single set of "loss" parameters which require adjustment through the process of calibration. To identify the importance of accounting for antecedent moisture in flood modeling, this paper uses a continuous rainfall-runoff model calibrated to 45 catchments in the Murray-Darling Basin in Australia. Flood peaks derived using the historical daily rainfall record are compared with those derived using resampled daily rainfall, for which the sequencing of wet and dry days preceding the heavy rainfall event is removed. The analysis shows that there is a consistent underestimation of the design flood events when antecedent moisture is not properly simulated, which can be as much as 30% when only 1 or 2 days of antecedent rainfall are considered, compared to 5% when this is extended to 60 days of prior rainfall. These results show that, in general, it is necessary to consider both short-term memory in rainfall associated with synoptic scale dependence, as well as longer-term memory at seasonal or longer time scale variability in order to obtain accurate design flood estimates.

Simulation of extreme rainfall and projection of future changes using the GLIMCLIM model

NASA Astrophysics Data System (ADS)

Rashid, Md. Mamunur; Beecham, Simon; Chowdhury, Rezaul Kabir

2017-10-01

In this study, the performance of the Generalized LInear Modelling of daily CLImate sequence (GLIMCLIM) statistical downscaling model was assessed to simulate extreme rainfall indices and annual maximum daily rainfall (AMDR) when downscaled daily rainfall from National Centers for Environmental Prediction (NCEP) reanalysis and Coupled Model Intercomparison Project Phase 5 (CMIP5) general circulation models (GCM) (four GCMs and two scenarios) output datasets and then their changes were estimated for the future period 2041-2060. The model was able to reproduce the monthly variations in the extreme rainfall indices reasonably well when forced by the NCEP reanalysis datasets. Frequency Adapted Quantile Mapping (FAQM) was used to remove bias in the simulated daily rainfall when forced by CMIP5 GCMs, which reduced the discrepancy between observed and simulated extreme rainfall indices. Although the observed AMDR were within the 2.5th and 97.5th percentiles of the simulated AMDR, the model consistently under-predicted the inter-annual variability of AMDR. A non-stationary model was developed using the generalized linear model for local, shape and scale to estimate the AMDR with an annual exceedance probability of 0.01. The study shows that in general, AMDR is likely to decrease in the future. The Onkaparinga catchment will also experience drier conditions due to an increase in consecutive dry days coinciding with decreases in heavy (>long term 90th percentile) rainfall days, empirical 90th quantile of rainfall and maximum 5-day consecutive total rainfall for the future period (2041-2060) compared to the base period (1961-2000).

Measurement accuracy of weighing and tipping-bucket rainfall intensity gauges under dynamic laboratory testing

NASA Astrophysics Data System (ADS)

Colli, M.; Lanza, L. G.; La Barbera, P.; Chan, P. W.

2014-07-01

The contribution of any single uncertainty factor in the resulting performance of infield rain gauge measurements still has to be comprehensively assessed due to the high number of real world error sources involved, such as the intrinsic variability of rainfall intensity (RI), wind effects, wetting losses, the ambient temperature, etc. In recent years the World Meteorological Organization (WMO) addressed these issues by fostering dedicated investigations, which revealed further difficulties in assessing the actual reference rainfall intensity in the field. This work reports on an extensive assessment of the OTT Pluvio2 weighing gauge accuracy when measuring rainfall intensity under laboratory dynamic conditions (time varying reference flow rates). The results obtained from the weighing rain gauge (WG) were also compared with a MTX tipping-bucket rain gauge (TBR) under the same test conditions. Tests were carried out by simulating various artificial precipitation events, with unsteady rainfall intensity, using a suitable dynamic rainfall generator. Real world rainfall data measured by an Ogawa catching-type drop counter at a field test site located within the Hong Kong International Airport (HKIA) were used as a reference for the artificial rain generation system. Results demonstrate that the differences observed between the laboratory and field performance of catching-type gauges are only partially attributable to the weather and operational conditions in the field. The dynamics of real world precipitation events is responsible for a large part of the measurement errors, which can be accurately assessed in the laboratory under controlled environmental conditions. This allows for new testing methodologies and the development of instruments with enhanced performance in the field.

Imaging groundwater infiltration dynamics in the karst vadose zone with long-term ERT monitoring

NASA Astrophysics Data System (ADS)

Watlet, Arnaud; Kaufmann, Olivier; Triantafyllou, Antoine; Poulain, Amaël; Chambers, Jonathan E.; Meldrum, Philip I.; Wilkinson, Paul B.; Hallet, Vincent; Quinif, Yves; Van Ruymbeke, Michel; Van Camp, Michel

2018-03-01

Water infiltration and recharge processes in karst systems are complex and difficult to measure with conventional hydrological methods. In particular, temporarily saturated groundwater reservoirs hosted in the vadose zone can play a buffering role in water infiltration. This results from the pronounced porosity and permeability contrasts created by local karstification processes of carbonate rocks. Analyses of time-lapse 2-D geoelectrical imaging over a period of 3 years at the Rochefort Cave Laboratory (RCL) site in south Belgium highlight variable hydrodynamics in a karst vadose zone. This represents the first long-term and permanently installed electrical resistivity tomography (ERT) monitoring in a karst landscape. The collected data were compared to conventional hydrological measurements (drip discharge monitoring, soil moisture and water conductivity data sets) and a detailed structural analysis of the local geological structures providing a thorough understanding of the groundwater infiltration. Seasonal changes affect all the imaged areas leading to increases in resistivity in spring and summer attributed to enhanced evapotranspiration, whereas winter is characterised by a general decrease in resistivity associated with a groundwater recharge of the vadose zone. Three types of hydrological dynamics, corresponding to areas with distinct lithological and structural features, could be identified via changes in resistivity: (D1) upper conductive layers, associated with clay-rich soil and epikarst, showing the highest variability related to weather conditions; (D2) deeper and more resistive limestone areas, characterised by variable degrees of porosity and clay contents, hence showing more diffuse seasonal variations; and (D3) a conductive fractured zone associated with damped seasonal dynamics, while showing a great variability similar to that of the upper layers in response to rainfall events. This study provides detailed images of the sources of drip discharge spots traditionally monitored in caves and aims to support modelling approaches of karst hydrological processes.

Dripping from Rough Multi-Segmented Fracture Sets into Unsaturated Rock Underground Excavations

NASA Astrophysics Data System (ADS)

Cesano, D.; Bagtzoglou, A. C.

2001-05-01

The aim of this paper is to present a probabilistic analytical formulation of unsaturated flow through a single rough multi-segmented fracture, with the ultimate goal to provide a numerical platform with which to perform calculations on the dripping initiation time and to explain the fast flow-paths detected and reported by Fabryka-Martin et al. (1996). To accomplish this, an enhanced version of the Wang and Narasimhan model (Wang and Narasimhan, 1985; 1993), the Enhanced Wang and Narasimhan Model (EWNM), has been used. In the EWNM, a fracture is formed by a finite number of connected fracture segments of given strike and dip. These parameters are sampled from hypothetical probability density functions. Unsaturated water flow occurs in these fracture segments, and in order for dripping to occur it is assumed that local saturation conditions exist at the surface and the tunnel level, where dripping occurs. The current version of the EWNM ignores transient flow processes, and thus it assumes the flow system being at equilibrium. The fracture segments are considered as rough fractures, with their roughness characterized by an aperture distribution function that can be derived from real field data. The roughness along each fracture segment is considered to be constant, leading to a constant effective aperture, and it is randomly assigned. An effective flow area is also included in the model, which accounts for three-dimensional variations of the fracture area that can be possibly occupied by water. The model takes into account the possibility that the fracture crosses multiple layers, each of which can have a different configuration in the values of the input parameters. Monte Carlo simulations calculate average times for water to flow from the top to the bottom of the fracture for a specified number of random realizations. The random component of the realizations comprises the different geometric configurations of the fracture flow path, while the value of all the input parameters and the statistical distribution they honor are kept constant from realization to realization. This travel time, called the dripping initiation time, is the cumulative sum of the time it takes for the water to drip through all fracture segments and eventually reach the tunnel. Based on the results of a sensitivity analysis, three different scenarios of input parameters were used to test the validity of the model with the fast flow-paths detected and reported in the Fabryka-Martin et al. (1996) study. The three scenarios differed from each other for the response of the dripping initiation times. These three different parameter configurations were then tested at three different depths. Each depth represented a different location where fast-flow has been detected at Yucca Mountain and reported by Fabryka-Martin et al. (1996). The first depth is considered representative of a location in correspondence to the Bow Ridge Fault. The second location represents a network of steep fractures and cooling joints with large variability in dip reaching the ESF at a depth of 180 meters. The third location, which is probably connected to the Diabolous Ridge Fault, is 290 meters deep and the flow path is low-dipping. Monte Carlo simulations were run for each configuration at each depth to calculate average dripping initiation times, so that results from 9 scenarios were produced. The final conclusion is that the model is able to produce results quite consistent with the Fabryka-Martin et al. (1996) study.

Quasi-continuous stochastic simulation framework for flood modelling

NASA Astrophysics Data System (ADS)

Moustakis, Yiannis; Kossieris, Panagiotis; Tsoukalas, Ioannis; Efstratiadis, Andreas

2017-04-01

Typically, flood modelling in the context of everyday engineering practices is addressed through event-based deterministic tools, e.g., the well-known SCS-CN method. A major shortcoming of such approaches is the ignorance of uncertainty, which is associated with the variability of soil moisture conditions and the variability of rainfall during the storm event.In event-based modeling, the sole expression of uncertainty is the return period of the design storm, which is assumed to represent the acceptable risk of all output quantities (flood volume, peak discharge, etc.). On the other hand, the varying antecedent soil moisture conditions across the basin are represented by means of scenarios (e.g., the three AMC types by SCS),while the temporal distribution of rainfall is represented through standard deterministic patterns (e.g., the alternative blocks method). In order to address these major inconsistencies,simultaneously preserving the simplicity and parsimony of the SCS-CN method, we have developed a quasi-continuous stochastic simulation approach, comprising the following steps: (1) generation of synthetic daily rainfall time series; (2) update of potential maximum soil moisture retention, on the basis of accumulated five-day rainfall; (3) estimation of daily runoff through the SCS-CN formula, using as inputs the daily rainfall and the updated value of soil moisture retention;(4) selection of extreme events and application of the standard SCS-CN procedure for each specific event, on the basis of synthetic rainfall.This scheme requires the use of two stochastic modelling components, namely the CastaliaR model, for the generation of synthetic daily data, and the HyetosMinute model, for the disaggregation of daily rainfall to finer temporal scales. Outcomes of this approach are a large number of synthetic flood events, allowing for expressing the design variables in statistical terms and thus properly evaluating the flood risk.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, R.A.; Cron, J.

This design analysis has shown that, on a conceptual level, the emplacement of drip shields is feasible with current technology and equipment. A plan for drip shield emplacement was presented using a Drip Shield Transporter, a Drip Shield Emplacement Gantry, a locomotive, and a Drip Shield Gantry Carrier. The use of a Drip Shield Emplacement Gantry as an emplacement concept results in a system that is simple, reliable, and interfaces with the numerous other exising repository systems. Using the Waste Emplacement/Retrieval System design as a basis for the drip shield emplacement concept proved to simplify the system by using existingmore » equipment, such as the gantry carrier, locomotive, Electrical and Control systems, and many other systems, structures, and components. Restricted working envelopes for the Drip Shield Emplacement System require further consideration and must be addressed to show that the emplacement operations can be performed as the repository design evolves. Section 6.1 describes how the Drip Shield Emplacement System may use existing equipment. Depending on the length of time between the conclusion of waste emplacement and the commencement of drip shield emplacement, this equipment could include the locomotives, the gantry carrier, and the electrical, control, and rail systems. If the exisiting equipment is selected for use in the Drip Shield Emplacement System, then the length of time after the final stages of waste emplacement and start of drip shield emplacement may pose a concern for the life cycle of the system (e.g., reliability, maintainability, availability, etc.). Further investigation should be performed to consider the use of existing equipment for drip shield emplacement operations. Further investigation will also be needed regarding the interfaces and heat transfer and thermal effects aspects. The conceptual design also requires further design development. Although the findings of this analysis are accurate for the assumptions made, further refinements of this analysis are needed as the project parameters change. The designs of the drip shield, the Emplacement Drift, and the other drip shield emplacement equipment all have a direct effect on the overall design feasibility.« less

Extreme rainfall-induced landslide changes based on landslide susceptibility in China, 1998-2015

NASA Astrophysics Data System (ADS)

Li, Weiyue; Liu, Chun; Hong, Yang

2017-04-01

Nowadays, landslide has been one of the most frequent and seriously widespread natural hazards all over the world. Rainfall, especially heavy rainfall is a trigger to cause the landslide occurrence, by increasing soil pore water pressures. In China, rainfall-induced landslides have risen up over to 90% of the total number. Rainfall events sometimes generate a trend of extremelization named rainfall extremes that induce the slope failure suddenly and severely. This study shows a method to simulate the rainfall-induced landslide spatio-temporal distribution on the basis of the landslide susceptibility index. First, the study on landslide susceptibility in China is introduced. We set the values of the index to the range between 0 and 1. Second, we collected TRMM 3B42 precipitation products spanning the years 1998-2015 and extracted the daily rainfall events greater than 50mm/day as extreme rainfall. Most of the rainfall duration time that may trigger a landslide has resulted between 3 hours and 45 hours. The combination of these two aspects can be exploited to simulate extreme rainfall-induced landslide distribution and illustrate the changes in 17 years. This study shows a useful tool to be part of rainfall-induced landslide simulation methodology for landslide early warning.

Hydrological modelling in sandstone rocks watershed

NASA Astrophysics Data System (ADS)

Ponížilová, Iva; Unucka, Jan

2015-04-01

The contribution is focused on the modelling of surface and subsurface runoff in the Ploučnice basin. The used rainfall-runoff model is HEC-HMS comprising of the method of SCS CN curves and a recession method. The geological subsurface consisting of sandstone is characterised by reduced surface runoff and, on the contrary, it contributes to subsurface runoff. The aim of this paper is comparison of the rate of influence of sandstone on reducing surface runoff. The recession method for subsurface runoff was used to determine the subsurface runoff. The HEC-HMS model allows semi- and fully distributed approaches to schematisation of the watershed and rainfall situations. To determine the volume of runoff the method of SCS CN curves is used, which results depend on hydrological conditions of the soils. The rainfall-runoff model assuming selection of so-called methods of event of the SCS-CN type is used to determine the hydrograph and peak flow rate based on simulation of surface runoff in precipitation exceeding the infiltration capacity of the soil. The recession method is used to solve the baseflow (subsurface) runoff. The method is based on the separation of hydrograph to direct runoff and subsurface or baseflow runoff. The study area for the simulation of runoff using the method of SCS CN curves to determine the hydrological transformation is the Ploučnice basin. The Ploučnice is a hydrologically significant river in the northern part of the Czech Republic, it is a right tributary of the Elbe river with a total basin area of 1.194 km2. The average value of CN curves for the Ploučnice basin is 72. The geological structure of the Ploučnice basin is predominantly formed by Mesozoic sandstone. Despite significant initial loss of rainfall the basin response to the causal rainfall was demonstrated by a rapid rise of the surface runoff from the watershed and reached culmination flow. Basically, only surface runoff occures in the catchment during the initial phase of this extreme event. The increase of the baseflow runoff is slower and remains constant after reaching a certain level. The rise of the baseflow runoff is showed in a descending part of the hydrograph. The recession method in this case shows almost 20 hours delay. Results from the HEC-HMS prove availability of both methods for the runoff modeling in this type of catchment. When simulating extreme short-term rainfall-runoff episodes, the influence of geological subsurface is not significant, but it is manifested. Using more relevant rainfall events would bring more satisfactory results.

The Spatial Scaling of Global Rainfall Extremes

NASA Astrophysics Data System (ADS)

Devineni, N.; Xi, C.; Lall, U.; Rahill-Marier, B.

2013-12-01

Floods associated with severe storms are a significant source of risk for property, life and supply chains. These property losses tend to be determined as much by the duration of flooding as by the depth and velocity of inundation. High duration floods are typically induced by persistent rainfall (upto 30 day duration) as seen recently in Thailand, Pakistan, the Ohio and the Mississippi Rivers, France, and Germany. Events related to persistent and recurrent rainfall appear to correspond to the persistence of specific global climate patterns that may be identifiable from global, historical data fields, and also from climate models that project future conditions. A clear understanding of the space-time rainfall patterns for events or for a season will enable in assessing the spatial distribution of areas likely to have a high/low inundation potential for each type of rainfall forcing. In this paper, we investigate the statistical properties of the spatial manifestation of the rainfall exceedances. We also investigate the connection of persistent rainfall events at different latitudinal bands to large-scale climate phenomena such as ENSO. Finally, we present the scaling phenomena of contiguous flooded areas as a result of large scale organization of long duration rainfall events. This can be used for spatially distributed flood risk assessment conditional on a particular rainfall scenario. Statistical models for spatio-temporal loss simulation including model uncertainty to support regional and portfolio analysis can be developed.

Longevity of shallow subsurface drip irrigation tubing under three tillage practices

USDA-ARS?s Scientific Manuscript database

Shallow Sub-Surface drip irrigation (S3DI) has drip tubing buried about 2-in below the soil surface. It is unknown how long drip tubing would be viable at this shallow soil depth using strip- or no-tillage systems. The objectives were to determine drip tube longevity, resultant crop yield, and parti...

Use of dynamical downscaling to improve the simulation of Central U.S. warm season precipitation in CMIP5 models

NASA Astrophysics Data System (ADS)

Harding, Keith J.; Snyder, Peter K.; Liess, Stefan

2013-11-01

supporting exceptionally productive agricultural lands, the Central U.S. is susceptible to severe droughts and floods. Such precipitation extremes are expected to worsen with climate change. However, future projections are highly uncertain as global climate models (GCMs) generally fail to resolve precipitation extremes. In this study, we assess how well models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) simulate summer means, variability, extremes, and the diurnal cycle of Central U.S. summer rainfall. Output from a subset of historical CMIP5 simulations are used to drive the Weather Research and Forecasting model to determine whether dynamical downscaling improves the representation of Central U.S. rainfall. We investigate which boundary conditions influence dynamically downscaled precipitation estimates and identify GCMs that can reasonably simulate precipitation when downscaled. The CMIP5 models simulate the seasonal mean and variability of summer rainfall reasonably well but fail to resolve extremes, the diurnal cycle, and the dynamic forcing of precipitation. Downscaling to 30 km improves these characteristics of precipitation, with the greatest improvement in the representation of extremes. Additionally, sizeable diurnal cycle improvements occur with higher (10 km) resolution and convective parameterization disabled, as the daily rainfall peak shifts 4 h closer to observations than 30 km resolution simulations. This lends greater confidence that the mechanisms responsible for producing rainfall are better simulated. Because dynamical downscaling can more accurately simulate these aspects of Central U.S. summer rainfall, policymakers can have added confidence in dynamically downscaled rainfall projections, allowing for more targeted adaptation and mitigation.

Sub-annual paleoenvironmental information evaluated from intensity variations of fluorescent annual layers in a stalagmite from Ryuo-do Cave, Nagasaki Prefecture, western Japan

NASA Astrophysics Data System (ADS)

Sasaki, Hana; Onishi, Yuri; Ishihara, Yoshiro; Yoshimura, Kazuhisa

2017-04-01

Stalagmites can provide various types of paleoenvironmental information such as information on vegetation and climate changes. Fluorescent annual layers formed by humic substances (mainly fulvic acids: FA) in these stalagmites can also provide a time proxy, and a time series on precipitation. Fluorescence intensity patterns in these annual layers can be classified into symmetric, gradually increasing and gradually decreasing types. Onishi et al. (EGU2016) demonstrated the existence of these fluorescence intensity patterns in the annual layers, and their stratigraphic changes, by numerical simulations, and suggested that the patterns could provide paleoenvironmental information at a sub-annual resolution. In this study, we carried out an analysis of fluorescence intensity patterns in the annual layers of a stalagmite from Ryuo-do Cave, Nagasaki Prefecture, western Japan, and also simulated the patterns in the stalagmite, to obtain paleoenvironmental information. Fluorescence intensity patterns in the annual layers are strongly affected by annual variations in FA concentration and precipitation rates of calcite. As the result of simulations of fluorescence intensity patterns, cumulative variations and various types of pattern are reproduced. These differences are depending on time lags between the variation of the FA concentration in the drip waters, and that of the growth rate of the stalagmite. Co-precipitation models of FA are divided into the "Hiatus model" in which FA are preferentially preserved in the stalagmite when its growth rate is relatively low, and the "Partition coefficient (PC) model" in which FA concentrations in the stalagmite increase when the calcite precipitation rate is relatively high. However, various fluorescence intensity patterns in the annual layers could be formed under a combination or either of both of the models. Fluorescence intensity patterns in an annual layer in the stalagmite from Ryuo-do Cave, Nagasaki Prefecture, western Japan vary stratigraphically, and multiple types of fluorescence intensity pattern are observed in the stalagmite. When the co-precipitation of FA is governed by the hiatus model, it is suggested that a gradual increase in the annual layers will result from a large accumulation of calcite after the annual peak in the FA concentration, whereas there will be a gradual decrease if the main growth occurs before the annual peak in FA concentration. However, in the case of the PC model, a gradually increasing type of pattern is formed if the main growth occurs before the annual peak in FA concentration, and a gradually decreasing type is formed if the main growth occurs afterwards. If the annual peak of FA concentration occurs several months after high summer, it is suggested that intervals showing a gradually increasing type were formed in winter, and intervals showing a gradually decreasing type were formed in the early summer, in the case of the hiatus model. In the case of PC model, the seasons are reversed. In the climatic environment around the Ryuo-do Cave, the growth rates of stalagmites are affected by cave air circulation in winter and by rainfall (rainy season) in early summer.

A laboratory rainfall simulator to study the soil erosion and runoff water

NASA Astrophysics Data System (ADS)

Cancelo González, Javier; Rial, M. E.; Díaz-Fierros, Francisco

2010-05-01

The soil erosion and the runoff water composition in some areas affected by forest fires or submitted to intensive agriculture are an important factor to keep an account, particularly in sensitive areas like estuary and rias that have a high importance in the socioeconomic development of some regions. An understanding of runoff production indicates the processes by which pollutants reach streams and also indicates the management techniques that might be uses to minimize the discharge of these materials into surface waters. One of the most methodology implemented in the soil erosion studies is a rainfall simulation. This method can reproduce the natural soil degradation processes in field or laboratory experiences. With the aim of improve the rainfall-runoff generation, a laboratory rainfall simulator which incorporates a fan-like intermittent water jet system for rainfall generation were modified. The major change made to the rainfall simulator consist in a system to coupling stainless steel boxes, whose dimensions are 12 x 20 x 45 centimeters, and it allows to place soil samples under the rainfall simulator. Previously these boxes were used to take soil samples in field with more of 20 centimeters of depth, causing the minimum disturbance in their properties and structure. These new implementations in the rainfall simulator also allow collect water samples of runoff in two ways: firstly, the rain water that constituted the overland flow or direct runoff and besides the rain water seeps into the soil by the process of infiltration and contributed to the subsurface runoff. Among main the variables controlled in the rainfall simulations were the soil slope and the intensity and duration of rainfall. With the aim of test the prototype, six soil samples were collected in the same sampling point and subjected to rainfall simulations in laboratory with the same intensity and duration. Two samples will constitute the control test, and they were fully undisturbed, and four samples were subjected to controlled burnings with different fire severity: two samples burnt to 250°C and the other two samples burnt to 450°C. Preliminary laboratory data of soil erosion and surface and subsurface runoff were obtained. The water parameters analysed were: pH, electrical conductivity, temperature (in the moment of sampling) and suspended sediments, ammonium, nitrates, total nitrogen (Kjeldahl method), within 24 hours after sampling.

A software-based sensor for combined sewer overflows.

PubMed

Leonhardt, G; Fach, S; Engelhard, C; Kinzel, H; Rauch, W

2012-01-01

A new methodology for online estimation of excess flow from combined sewer overflow (CSO) structures based on simulation models is presented. If sufficient flow and water level data from the sewer system is available, no rainfall data are needed to run the model. An inverse rainfall-runoff model was developed to simulate net rainfall based on flow and water level data. Excess flow at all CSO structures in a catchment can then be simulated with a rainfall-runoff model. The method is applied to a case study and results show that the inverse rainfall-runoff model can be used instead of missing rain gauges. Online operation is ensured by software providing an interface to the SCADA-system of the operator and controlling the model. A water quality model could be included to simulate also pollutant concentrations in the excess flow.

Continuous Sub-daily Rainfall Simulation for Regional Flood Risk Assessment - Modelling of Spatio-temporal Correlation Structure of Extreme Precipitation in the Austrian Alps

NASA Astrophysics Data System (ADS)

Salinas, J. L.; Nester, T.; Komma, J.; Bloeschl, G.

2017-12-01

Generation of realistic synthetic spatial rainfall is of pivotal importance for assessing regional hydroclimatic hazard as the input for long term rainfall-runoff simulations. The correct reproduction of observed rainfall characteristics, such as regional intensity-duration-frequency curves, and spatial and temporal correlations is necessary to adequately model the magnitude and frequency of the flood peaks, by reproducing antecedent soil moisture conditions before extreme rainfall events, and joint probability of flood waves at confluences. In this work, a modification of the model presented by Bardossy and Platte (1992), where precipitation is first modeled on a station basis as a multivariate autoregressive model (mAr) in a Normal space. The spatial and temporal correlation structures are imposed in the Normal space, allowing for a different temporal autocorrelation parameter for each station, and simultaneously ensuring the positive-definiteness of the correlation matrix of the mAr errors. The Normal rainfall is then transformed to a Gamma-distributed space, with parameters varying monthly according to a sinusoidal function, in order to adapt to the observed rainfall seasonality. One of the main differences with the original model is the simulation time-step, reduced from 24h to 6h. Due to a larger availability of daily rainfall data, as opposite to sub-daily (e.g. hourly), the parameters of the Gamma distributions are calibrated to reproduce simultaneously a series of daily rainfall characteristics (mean daily rainfall, standard deviations of daily rainfall, and 24h intensity-duration-frequency [IDF] curves), as well as other aggregated rainfall measures (mean annual rainfall, and monthly rainfall). The calibration of the spatial and temporal correlation parameters is performed in a way that the catchment-averaged IDF curves aggregated at different temporal scales fit the measured ones. The rainfall model is used to generate 10.000 years of synthetic precipitation, fed into a rainfall-runoff model to derive the flood frequency in the Tirolean Alps in Austria. Given the number of generated events, the simulation framework is able to generate a large variety of rainfall patterns, as well as reproduce the variograms of relevant extreme rainfall events in the region of interest.

Influences of Appalachian orography on heavy rainfall and rainfall variability associated with the passage of hurricane Isabel by ensemble simulations

NASA Astrophysics Data System (ADS)

Oldaker, Guy; Liu, Liping; Lin, Yuh-Lang

2017-12-01

This study focuses on the heavy rainfall event associated with hurricane Isabel's (2003) passage over the Appalachian mountains of the eastern United States. Specifically, an ensemble consisting of two groups of simulations using the Weather Research and Forecasting model (WRF), with and without topography, is performed to investigate the orographic influences on heavy rainfall and rainfall variability. In general, the simulated ensemble mean with full terrain is able to reproduce the key observed 24-h rainfall amount and distribution, while the flat-terrain mean lacks in this respect. In fact, 30-h rainfall amounts are reduced by 75% with the removal of topography. Rainfall variability is also significantly increased with the presence of orography. Further analysis shows that the complex interaction between the hurricane and terrain along with contributions from varied microphysics, cumulus parametrization, and planetary boundary layer schemes have a pronounced effect on rainfall and rainfall variability. This study follows closely with a previous study, but for a different TC case of Isabel (2003). It is an important sensitivity test for a different TC in a very different environment. This study reveals that the rainfall variability behaves similarly, even with different settings of the environment.

Constraining continuous rainfall simulations for derived design flood estimation

NASA Astrophysics Data System (ADS)

Woldemeskel, F. M.; Sharma, A.; Mehrotra, R.; Westra, S.

2016-11-01

Stochastic rainfall generation is important for a range of hydrologic and water resources applications. Stochastic rainfall can be generated using a number of models; however, preserving relevant attributes of the observed rainfall-including rainfall occurrence, variability and the magnitude of extremes-continues to be difficult. This paper develops an approach to constrain stochastically generated rainfall with an aim of preserving the intensity-durationfrequency (IFD) relationships of the observed data. Two main steps are involved. First, the generated annual maximum rainfall is corrected recursively by matching the generated intensity-frequency relationships to the target (observed) relationships. Second, the remaining (non-annual maximum) rainfall is rescaled such that the mass balance of the generated rain before and after scaling is maintained. The recursive correction is performed at selected storm durations to minimise the dependence between annual maximum values of higher and lower durations for the same year. This ensures that the resulting sequences remain true to the observed rainfall as well as represent the design extremes that may have been developed separately and are needed for compliance reasons. The method is tested on simulated 6 min rainfall series across five Australian stations with different climatic characteristics. The results suggest that the annual maximum and the IFD relationships are well reproduced after constraining the simulated rainfall. While our presentation focusses on the representation of design rainfall attributes (IFDs), the proposed approach can also be easily extended to constrain other attributes of the generated rainfall, providing an effective platform for post-processing of stochastic rainfall generators.

Wind erodibility response of physical and biological crusts to rain and flooding

NASA Astrophysics Data System (ADS)

Aubault, H.; Bullard, J. E.; Strong, C. L.; Ghadiri, H.; McTainsh, G. H.

2015-12-01

Soil surface crusts are important controllers of the small-scale wind entrainment processes that occur across all dust source regions globally. The crust type influences water and wind erosion by impacting infiltration, runoff, threshold wind velocity and surface storage capacity of both water and loose erodible material. The spatial and temporal patterning of both physical and biological crusts is known to change with rainfall and flooding. However, little is known about the impact of differing water quantity (from light rainfall through to flooding) on soil crusting characteristics (strength, roughness, sediment loss). This study compares the response of two soil types (loamy sand - LS, sandy loam - SL) with and without BSCs to three different rainfall events (2mm, 8mm, 15mm). Two BSC treatments were used one that simulated a young cyanobacteria dominated crust and an older flood induced multi species biological crust. For both soil types, soil surface strength increased with increasing rainfall amount with LS having consistently higher resistance to rupture than SL. Regardless of texture, soils with BSCs were more resistant and strength did not change in response to rainfall impact. Soil loss due to wind erosion was substantially higher on bare LS (4 times higher) and SL (3 times higher) soils compared with those with BSCs. Our results also show that young biological crust (formed by the rainfall event) have reduced soil erodibility with notably greater strength, roughness and reduced sediment losses when compared to soils with physical crust. Interestingly though, the erodibility of the old BSC did not differ greatly from that of the young BSC with respect to strength, roughness and sediment loss. This raises questions regarding the rapid soil surface protection offered by young colonising cyanobacteria crusts. Further analyses exploring the role of biological soil crusts on surface response to rainfall and wind saltation impact are ongoing.

Extreme Rainfall from Hurricane Harvey (2017): Intercomparisons of WRF Simulations and Polarimetric Radar Fields

NASA Astrophysics Data System (ADS)

Yang, L.; Smith, J. A.; Liu, M.; Baeck, M. L.; Chaney, M. M.; Su, Y.

2017-12-01

Hurricane Harvey made landfall on 25 August 2017 and produced more than a meter of rain during a four-day period over eastern Texas, making it the wettest tropical cyclone on record in the United States. Extreme rainfall from Harvey was predominantly related to the dynamics and structure of outer rain bands. In this study, we provide details of the extreme rainfall produced by Hurricane Harvey. The principal research questions that motivate this study are: (1) what are the key microphysical properties of extreme rainfall from landfalling tropical cyclones and (2) what are the capabilities and deficiencies of existing bulk microphysics parameterizations from the physical models in capturing them. Our analyses are centered on intercomparisons of high-resolution simulations using the Weather Research and Forecasting (WRF) model and polarimetric radar fields from KHGX (Houston, Texas) WSR-88D. The WRF simulations accurately capture the track and intensity of Hurricane Harvey. Multi-rainband structure and its key evolution features are also well represented in the simulations. Two microphysics parameterizations (WSM6 and WDM6) are tested in this study. Radar reflectivity and differential reflectivity fields simulated by the WRF model are compared with polarimetric radar observations. An important feature for the extreme rainfall from Hurricane Harvey is the sharp boundary of spatial rainfall accumulation along the coast (with torrential rainfall distributed over Houston and its surrounding inland areas). We will examine the role of land-sea contrasts in dictating storm structure and evolution from both WRF simulations and polarimetric radar fields. Implications for improving hurricane rainfall forecasts and estimates will be provided.

Evaporative cooling of speleothem drip water

PubMed Central

Cuthbert, M. O.; Rau, G. C.; Andersen, M. S.; Roshan, H.; Rutlidge, H.; Marjo, C. E.; Markowska, M.; Jex, C. N.; Graham, P. W.; Mariethoz, G.; Acworth, R. I.; Baker, A.

2014-01-01

This study describes the first use of concurrent high-precision temperature and drip rate monitoring to explore what controls the temperature of speleothem forming drip water. Two contrasting sites, one with fast transient and one with slow constant dripping, in a temperate semi-arid location (Wellington, NSW, Australia), exhibit drip water temperatures which deviate significantly from the cave air temperature. We confirm the hypothesis that evaporative cooling is the dominant, but so far unattributed, control causing significant disequilibrium between drip water and host rock/air temperatures. The amount of cooling is dependent on the drip rate, relative humidity and ventilation. Our results have implications for the interpretation of temperature-sensitive, speleothem climate proxies such as δ18O, cave microecology and the use of heat as a tracer in karst. Understanding the processes controlling the temperature of speleothem-forming cave drip waters is vital for assessing the reliability of such deposits as archives of climate change. PMID:24895139

A small single-nozzle rainfall simulator to measure erosion response on different burn severities in southern British Columbia, Canada

NASA Astrophysics Data System (ADS)

Covert, Ashley; Jordan, Peter

2010-05-01

To study the effects of wildfire burn severity on runoff generation and soil erosion from high intensity rainfall, we constructed an effective yet simple rainfall simulator that was inexpensive, portable and easily operated by two people on steep, forested slopes in southern British Columbia, Canada. The entire apparatus, including simulator, pumps, hoses, collapsible water bladders and sample bottles, was designed to fit into a single full-sized pick-up truck. The three-legged simulator extended to approximately 3.3 metres above ground on steep slopes and used a single Spraying Systems 1/2HH-30WSQ nozzle which can easily be interchanged for other sized nozzles. Rainfall characteristics were measured using a digital camera which took images of the raindrops against a grid. Median drop size and velocity 5 cm above ground were measured and found to be 3/4 of the size of natural rain drops of that diameter class, and fell 7% faster than terminal velocity. The simulator was used for experiments on runoff and erosion on sites burned in 2007 by two wildfires in southern British Columbia. Simulations were repeated one and two years after the fires. Rainfall was simulated at an average rate of 67 mm hr-1 over a 1 m2 plot for 20 minutes. This rainfall rate is similar to the 100 year return period rainfall intensity for this duration at a nearby weather station. Simulations were conducted on five replicate 1 m2 plots in each experimental unit including high burn severity, moderate burn severity, unburned, and unburned with forest floor removed. During the simulation a sample was collected for 30 seconds every minute, with two additional samples until runoff ceased, resulting in 22 samples per simulation. Runoff, overland flow coefficient, infiltration and sediment yield were compared between treatments. Additional simulations were conducted immediately after a 2009 wildfire to test different mulch treatments. Typical results showed that runoff on plots with high burn severity and with forest floor removed was similar, reaching on average a steady rate of about 60% of rainfall rate after about 7 minutes. Runoff on unburned plots with intact forest floor was much lower, typically less than 20% of rainfall rate. Sediment yield was greatest on plots with forest floor removed, followed by severely burned plots. Sediment yield on unburned and moderately burned plots was very low to zero. These results are consistent with qualitative observations made following several extreme rainfall events on recent burns in the region.

Hydrograph simulation models of the Hillsborough and Alafia Rivers, Florida: a preliminary report

USGS Publications Warehouse

Turner, James F.

1972-01-01

Mathematical (digital) models that simulate flood hydrographs from rainfall records have been developed for the following gaging stations in the Hillsborough and Alafia River basins of west-central Florida: Hillsborough River near Tampa, Alafia River at Lithia, and north Prong Alafia River near Keysville. These models, which were developed from historical streamflow and and rainfall records, are based on rainfall-runoff and unit-hydrograph procedures involving an arbitrary separation of the flood hydrograph. These models assume the flood hydrograph to be composed of only two flow components, direct (storm) runoff, and base flow. Expressions describing these two flow components are derived from streamflow and rainfall records and are combined analytically to form algorithms (models), which are programmed for processing on a digital computing system. Most Hillsborough and Alafia River flood discharges can be simulated with expected relative errors less than or equal to 30 percent and flood peaks can be simulated with average relative errors less than 15 percent. Because of the inadequate rainfall network that is used in obtaining input data for the North Prong Alafia River model, simulated peaks are frequently in error by more than 40 percent, particularly for storms having highly variable areal rainfall distribution. Simulation errors are the result of rainfall sample errors and, to a lesser extent, model inadequacy. Data errors associated with the determination of mean basin precipitation are the result of the small number and poor areal distribution of rainfall stations available for use in the study. Model inadequacy, however, is attributed to the basic underlying theory, particularly the rainfall-runoff relation. These models broaden and enhance existing water-management capabilities within these basins by allowing the establishment and implementation of programs providing for continued development in these areas. Specifically, the models serve not only as a basis for forecasting floods, but also for simulating hydrologic information needed in flood-plain mapping and delineating and evaluating alternative flood control and abatement plans.

Rainfall-Runoff Simulations to Assess the Potential of SuDS for Mitigating Flooding in Highly Urbanized Catchments.

PubMed

Jato-Espino, Daniel; Charlesworth, Susanne M; Bayon, Joseba R; Warwick, Frank

2016-01-21

Sustainable Urban Drainage Systems (SuDS) constitute an alternative to conventional drainage when managing stormwater in cities, reducing the impact of urbanization by decreasing the amount of runoff generated by a rainfall event. This paper shows the potential benefits of installing different types of SuDS in preventing flooding in comparison with the common urban drainage strategies consisting of sewer networks of manholes and pipes. The impact of these systems on urban water was studied using Geographic Information Systems (GIS), which are useful tools when both delineating catchments and parameterizing the elements that define a stormwater drainage system. Taking these GIS-based data as inputs, a series of rainfall-runoff simulations were run in a real catchment located in the city of Donostia (Northern Spain) using stormwater computer models, in order to compare the flow rates and depths produced by a design storm before and after installing SuDS. The proposed methodology overcomes the lack of precision found in former GIS-based stormwater approaches when dealing with the modeling of highly urbanized catchments, while the results demonstrated the usefulness of these systems in reducing the volume of water generated after a rainfall event and their ability to prevent localized flooding and surcharges along the sewer network.

Research on the semi-distributed monthly rainfall runoff model at the Lancang River basin based on DEM

NASA Astrophysics Data System (ADS)

Liu, Gang; Zhao, Rong; Liu, Jiping; Zhang, Qingpu

2007-06-01

The Lancang River Basin is so narrow and its hydrological and meteorological information are so flexible. The Rainfall, evaporation, glacial melt water and groundwater affect the runoff whose replenishment forms changing notable with the season in different areas at the basin. Characters of different kind of distributed model and conceptual hydrological model are analyzed. A semi-distributed hydrological model of relation between monthly runoff and rainfall, temperate and soil type has been built in Changdu County based on Visual Basic and ArcObject. The way of discretization of distributed hydrological model was used in the model, and principles of conceptual model are taken into account. The sub-catchment of Changdu is divided into regular cells, and all kinds of hydrological and meteorological information and land use classes and slope extracted from 1:250000 digital elevation models are distributed in each cell. The model does not think of the rainfall-runoff hydro-physical process but use the conceptual model to simulate the whole contributes to the runoff of the area. The affection of evapotranspiration loss and underground water is taken into account at the same time. The spatial distribute characteristics of the monthly runoff in the area are simulated and analyzed with a few parameters.

Simulation of infiltration and redistribution of intense rainfall using Land Surface Models

NASA Astrophysics Data System (ADS)

Mueller, Anna; Verhoef, Anne; Cloke, Hannah

2016-04-01

Flooding from intense rainfall (FFIR) can cause widespread damage and disruption. Numerical Weather Prediction (NWP) models provide distributed information about atmospheric conditions, such as precipitation, that can lead to a flooding event. Short duration, high intensity rainfall events are generally poorly predicted by NWP models, because of the high spatiotemporal resolution required and because of the way the convective rainfall is described in the model. The resolution of NWP models is ever increasing. Better understanding of complex hydrological processes and the effect of scale is important in order to improve the prediction of magnitude and duration of such events, in the context of disaster management. Working as part of the NERC SINATRA project, we evaluated how the Land Surface Model (LSM) components of NWP models cope with high intensity rainfall input and subsequent infiltration problems. Both in terms of the amount of water infiltrated in the soil store, as well as the timing and the amount of surface and subsurface runoff generated. The models investigated are SWAP (Soil Water Air Plant, Alterra, the Netherlands, van Dam 1997), JULES (Joint UK Land Environment Simulator a component of Unified Model in UK Met Office, Best et al. 2011) and CHTESSEL (Carbon and Hydrology- Tiled ECMWF Scheme for Surface Exchanges over Land, Balsamo et al. 2009) We analysed the numerical aspects arising from discontinuities (or sharp gradients) in forcing and/or the model solution. These types of infiltration configurations were tested in the laboratory (Vachaud 1971), for some there are semi-analytical solutions (Philip 1957, Parlange 1972, Vanderborght 2005) or reference numerical solutions (Haverkamp 1977, van Dam 2000, Vanderborght 2005). The maximum infiltration by the surface, Imax, is in general dependent on atmospheric conditions, surface type, soil type, soil moisture content θ, and surface orographic factor σ. The models used differ in their approach to describe and deal with this top boundary condition definition. All three LSMs discretise the spatial derivative in the Richards equation (∂/∂z) using central finite differences, which is a 2nd order method, that according to Godunov's theorem is non-monotone. It is prone to producing non-physical oscillations in the solution. We performed a mesh and timestep dependence study for hypothetical soil columns and showed the presence of the oscillations in Jules and SWAP solutions. We also investigated the rainfall/runoff partition and redistribution in case of intense rainfall using these three models.

Can spatial patterns along climatic gradients predict ecosystem responses to climate change? Experimenting with reaction-diffusion simulations.

PubMed

Roitberg, Elena; Shoshany, Maxim

2017-01-01

Following a predicted decline in water resources in the Mediterranean Basin, we used reaction-diffusion equations to gain a better understanding of expected changes in properties of vegetation patterns that evolve along the rainfall transition between semi-arid and arid rainfall regions. Two types of scenarios were investigated: the first, a discrete scenario, where the potential consequences of climate change are represented by patterns evolving at discrete rainfall levels along a rainfall gradient. This scenario concerns space-for-time substitutions characteristic of the rainfall gradient hypothesis. The second, a continuous scenario, represents explicitly the effect of rainfall decline on patterns which evolved at different rainfall levels along the rainfall gradient prior to the climate change. The eccentricity of patterns that emerge through these two scenarios was found to decrease with decreasing rainfall, while their solidity increased. Due to their inverse modes of change, their ratio was found to be a highly sensitive indicator for pattern response to rainfall decline. An eccentricity ratio versus rainfall (ER:R) line was generalized from the results of the discrete experiment, where ERs above this line represent developed (recovered) patterns and ERs below this line represent degraded patterns. For the rainfall range of 1.2 to 0.8 mm/day, the continuous rainfall decline experiment with ERs that lie above the ER:R line, yielded patterns less affected by rainfall decline than would be expected according to the discrete representation of ecosystems' response. Thus, for this range, space-for-time substitution represents an overestimation of the consequences of the expected rainfall decline. For rainfall levels below 0.8 mm/day, eccentricity ratios from the discrete and continuous experiments practically converge to the same trend of pattern change along the ER:R line. Thus, the rainfall gradient hypothesis may be valid for regions characterized by this important rainfall range, which typically include desert fringe ecosystems.

How spatial and temporal rainfall variability affect runoff across basin scales: insights from field observations in the (semi-)urbanised Charlotte watershed

NASA Astrophysics Data System (ADS)

Ten Veldhuis, M. C.; Smith, J. A.; Zhou, Z.

2017-12-01

Impacts of rainfall variability on runoff response are highly scale-dependent. Sensitivity analyses based on hydrological model simulations have shown that impacts are likely to depend on combinations of storm type, basin versus storm scale, temporal versus spatial rainfall variability. So far, few of these conclusions have been confirmed on observational grounds, since high quality datasets of spatially variable rainfall and runoff over prolonged periods are rare. Here we investigate relationships between rainfall variability and runoff response based on 30 years of radar-rainfall datasets and flow measurements for 16 hydrological basins ranging from 7 to 111 km2. Basins vary not only in scale, but also in their degree of urbanisation. We investigated temporal and spatial variability characteristics of rainfall fields across a range of spatial and temporal scales to identify main drivers for variability in runoff response. We identified 3 ranges of basin size with different temporal versus spatial rainfall variability characteristics. Total rainfall volume proved to be the dominant agent determining runoff response at all basin scales, independent of their degree of urbanisation. Peak rainfall intensity and storm core volume are of secondary importance. This applies to all runoff parameters, including runoff volume, runoff peak, volume-to-peak and lag time. Position and movement of the storm with respect to the basin have a negligible influence on runoff response, with the exception of lag times in some of the larger basins. This highlights the importance of accuracy in rainfall estimation: getting the position right but the volume wrong will inevitably lead to large errors in runoff prediction. Our study helps to identify conditions where rainfall variability matters for correct estimation of the rainfall volume as well as the associated runoff response.

A subsurface drip irrigation system for weighing lysimetry

USDA-ARS?s Scientific Manuscript database

Large, precision weighing lysimeters can have accuracies as good as 0.04 mm equivalent depth of water, adequate for hourly and even half-hourly determinations of evapotranspiration (ET) rate from crops. Such data are important for testing and improving simulation models of the complex interactions o...

Surface runoff and soil erosion by difference of surface cover characteristics using by an oscillating rainfall simulator

NASA Astrophysics Data System (ADS)

Kim, J. K.; Kim, M. S.; Yang, D. Y.

2017-12-01

Sediment transfer within hill slope can be changed by the hydrologic characteristics of surface material on hill slope. To better understand sediment transfer of the past and future related to climate changes, studies for the changes of soil erosion due to hydrological characteristics changes by surface materials on hill slope are needed. To do so, on-situ rainfall simulating test was conducted on three different surface conditions, i.e. well covered with litter layer condition (a), undisturbed bare condition (b), and disturbed bare condition (c) and these results from rainfall simulating test were compared with that estimated using the Limburg Soil Erosion Model (LISEM). The result from the rainfall simulating tests showed differences in the infiltration rate (a > b > c) and the highest soil erosion rate was occurred on c condition. The result from model also was similar to those from rainfall simulating tests, however, the difference from the value of soil erosion rate between two results was quite large on b and c conditions. These results implied that the difference of surface conditions could change the surface runoff and soil erosion and the result from the erosion model might significantly underestimate on bare surface conditions rather than that from rainfall simulating test.

Effects of Timber Harvest on Fog Drip and Streamflow, Caspar Creek Experimental Watersheds, Mendocino County, California

Treesearch

Elizabeth Keppeler

2007-01-01

Within the second-growth redwood forest of the Caspar Creek watershed, fog drip was measured in 1998 at 12 sites where heavy fog drip was expected. The following year, two one-ha plots were each instrumented with six randomly sited 1.35 m2 fog-drip collectors and one additional collector in a nearby clearcut. Fog-drip totals were highly variable...

Microfluidic manipulation of magnetic flux domains in type-I superconductors: droplet formation, fusion and fission.

PubMed

Berdiyorov, G R; Milošević, M V; Hernández-Nieves, A D; Peeters, F M; Domínguez, D

2017-09-21

The magnetic flux domains in the intermediate state of type-I superconductors are known to resemble fluid droplets, and their dynamics in applied electric current is often cartooned as a "dripping faucet". Here we show, using the time-depended Ginzburg-Landau simulations, that microfluidic principles hold also for the determination of the size of the magnetic flux-droplet as a function of the applied current, as well as for the merger or splitting of those droplets in the presence of the nanoengineered obstacles for droplet motion. Differently from fluids, the flux-droplets in superconductors are quantized and dissipative objects, and their pinning/depinning, nucleation, and splitting occur in a discretized form, all traceable in the voltage measured across the sample. At larger applied currents, we demonstrate how obstacles can cause branching of laminar flux streams or their transformation into mobile droplets, as readily observed in experiments.

49 CFR 173.465 - Type A packaging tests.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., with contents, must be capable of withstanding the water spray, free drop, stacking and penetration... paragraph (b) of this section are met. (b) Water spray test. The water spray test must precede each test or test sequence prescribed in this section. The water spray test must simulate exposure to rainfall of...

High-resolution stochastic generation of extreme rainfall intensity for urban drainage modelling applications

NASA Astrophysics Data System (ADS)

Peleg, Nadav; Blumensaat, Frank; Molnar, Peter; Fatichi, Simone; Burlando, Paolo

2016-04-01

Urban drainage response is highly dependent on the spatial and temporal structure of rainfall. Therefore, measuring and simulating rainfall at a high spatial and temporal resolution is a fundamental step to fully assess urban drainage system reliability and related uncertainties. This is even more relevant when considering extreme rainfall events. However, the current space-time rainfall models have limitations in capturing extreme rainfall intensity statistics for short durations. Here, we use the STREAP (Space-Time Realizations of Areal Precipitation) model, which is a novel stochastic rainfall generator for simulating high-resolution rainfall fields that preserve the spatio-temporal structure of rainfall and its statistical characteristics. The model enables a generation of rain fields at 102 m and minute scales in a fast and computer-efficient way matching the requirements for hydrological analysis of urban drainage systems. The STREAP model was applied successfully in the past to generate high-resolution extreme rainfall intensities over a small domain. A sub-catchment in the city of Luzern (Switzerland) was chosen as a case study to: (i) evaluate the ability of STREAP to disaggregate extreme rainfall intensities for urban drainage applications; (ii) assessing the role of stochastic climate variability of rainfall in flow response and (iii) evaluate the degree of non-linearity between extreme rainfall intensity and system response (i.e. flow) for a small urban catchment. The channel flow at the catchment outlet is simulated by means of a calibrated hydrodynamic sewer model.

On the Numerical Study of Heavy Rainfall in Taiwan

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Chen, Ching-Sen; Chen, Yi-Leng; Jou, Ben Jong-Dao; Lin, Pay-Liam; Starr, David OC. (Technical Monitor)

2001-01-01

Heavy rainfall events are frequently observed over the western side of the CMR (central mountain range), which runs through Taiwan in a north-south orientation, in a southwesterly flow regime and over the northeastern side of the CMR in a northeasterly flow regime. Previous studies have revealed the mechanisms by which the heavy rainfall events are formed. Some of them have examined characteristics of the heavy rainfall via numerical simulations. In this paper, some of the previous numerical studies on heavy rainfall events around Taiwan during the Mei-Yu season (May and June), summer (non-typhoon cases) and autumn will be reviewed. Associated mechanisms proposed from observational studies will be reviewed first, and then characteristics of numerically simulated heavy rainfall events will be presented. The formation mechanisms of heavy rainfall from simulated results and from observational analysis are then compared and discussed. Based on these previous modeling studies, we will also discuss what are the major observations and modeling processes which will be needed for understanding the heavy precipitation in the future.

Diagnosing Hydrologic Flow Paths in Forest and Pasture Land Uses within the Panama Canal Watershed Using Simulated Rainfall and Electrical Resistivity Tomography

NASA Astrophysics Data System (ADS)

Ogden, F. L.; Mojica, A.; Kempema, E. W.; Briceno, J. C.; Regina, J. A.

2014-12-01

Hydrological processes in the humid tropics are poorly understood and an important topic when it comes to water management in the seasonal tropics. The Smithsonian Tropical Research Institute, Panama Canal Watershed Experiment, Agua Salud Project, seeks to understand these processes and quantify the long-term effects of different land cover and use across the Panama Canal Watershed. In this study we used an ARS-type rainfall simulator to apply rainfall rates up to 200 mm per hour over a 2m by 6m area on deep saprolitic soils in forest and pasture land covers. A salinity contrast added to the applied rainwater allowed observation of bulk flow paths and velocities in the subsurface. The observed effects of land cover and land use on hydrological response were striking. In the forest site, we were unable to produce surface runoff even after the application of 600 mm of rainfall in three hours, and observed flow in soils down to approximately 2 m depth, and no downslope macropore flow. In the pasture site, surface runoff was produced, and we measured the permeability of the area with applied rainfall. Observed flow paths were much shallower, less than 1 m depth, with significant macropore flow observed at downslope positions. We hypothesize that land use and land cover have significant impacts on flow paths as they affect creation, connectivity, and function of biologically created macropores in the soil.

Rainfall estimates for hydrological models: Comparing rain gauge, radar and microwave link data as input for the Wageningen Lowland Runoff Simulator (WALRUS)

NASA Astrophysics Data System (ADS)

Brauer, Claudia; Overeem, Aart; Uijlenhoet, Remko

2015-04-01

Several rainfall measurement techniques are available for hydrological applications, each with its own spatial and temporal resolution. We investigated the effect of differences in rainfall estimates on discharge simulations in a lowland catchment by forcing a novel rainfall-runoff model (WALRUS) with rainfall data from gauges, radars and microwave links. The hydrological model used for this analysis is the recently developed Wageningen Lowland Runoff Simulator (WALRUS). WALRUS is a rainfall-runoff model accounting for hydrological processes relevant to areas with shallow groundwater (e.g. groundwater-surface water feedback). Here, we used WALRUS for case studies in the Hupsel Brook catchment. We used two automatic rain gauges with hourly resolution, located inside the catchment (the base run) and 30 km northeast. Operational (real-time) and climatological (gauge-adjusted) C-band radar products and country-wide rainfall maps derived from microwave link data from a cellular telecommunication network were also used. Discharges simulated with these different inputs were compared to observations. Traditionally, the precipitation research community places emphasis on quantifying spatial errors and uncertainty, but for hydrological applications, temporal errors and uncertainty should be quantified as well. Its memory makes the hydrologic system sensitive to missed or badly timed rainfall events, but also emphasizes the effect of a bias in rainfall estimates. Systematic underestimation of rainfall by the uncorrected operational radar product leads to very dry model states and an increasing underestimation of discharge. Using the rain gauge 30 km northeast of the catchment yields good results for climatological studies, but not for forecasting individual floods. Simulating discharge using the maps derived from microwave link data and the gauge-adjusted radar product yields good results for both events and climatological studies. This indicates that these products can be used in catchments without gauges in or near the catchment. Uncertainty in rainfall forcing is a major source of uncertainty in discharge predictions, both with lumped and with distributed models. For lumped rainfall-runoff models, the main source of input uncertainty is associated with the way in which (effective) catchment-average rainfall is estimated. Improving rainfall measurements can improve the performance of rainfall-runoff models, indicating their potential for reducing flood damage through real-time control.

[Behind the scenes of the didactic of nursing science knowledge: role play simulation filmed for learning through "problematic situations"].

PubMed

Gineyt, Christine

2015-12-01

clinical simulation to teach expertise to nursing students plays an important role in nursing schools (IFSI). as recommended in the training frame of reference, students must develop skills from real situations. The objective of this study was to determine the importance of role play simulation of 'problematic situations' to boost the process of appropriation of nursing science knowledge and initiate the task of conceptualization among first year students when putting up a drip. this contextual research used qualitative data collected from students who answered three open post-simulation questions in order to communicate how they felt faced with this learning technique. This data was compared with that of two executive tutors who used an observation grid during the simulation. the students' answers have shown that this learning technique offered the possibility to develop dexterity in problem solving skills, to construct new knowledge and to memorize knowledge gained from university science and nursing care. The executive tutors have observed the construction of a meta-cognitive attitude suited to the conceptualization of action. during a change in the relationship with knowledge, the executive tutors noted that students are happy to learn different types of knowledge.

Controls on dripwater chemistry of Oregon Caves National Monument, northwestern United States

NASA Astrophysics Data System (ADS)

Rushdi, Ahmed I.; Ersek, Vasile; Mix, Alan C.; Clark, Peter U.

2018-02-01

Cave dripwater chemistry of Oregon Caves National Monument (OCNM) was studied, where the parameters pH, total alkalinity, calcium, magnesium, strontium, sodium and barium were analyzed at quasi-monthly intervals from 2005 to 2007. Different statistical analyses have been used to investigate the variability of the chemical parameters in the different sites in the OCNM cave system. The dripwater varies in response to seasonal changes in rainfall. The drip rates range from zero in summer to continuous flow in winter, closely following the rainfall intensity. Spatial variations of dripwater chemistry, which is nonlinearly related to dripwater discharge likely, reflect the chemical composition of bedrock and overlying soil, and the residence time of the ground water within the aquifer. The residence time of infiltrated water in bedrock cracks control the dissolution carbonate bedrock, reprecipitation of calcium carbonate and the degree of saturation of dripwater with respect to calcium carbonate minerals. Spatiotemporal fluctuations of dripwater Mg/Ca and Sr/Ca ratios are controlled by dissolution of carbonate bedrock and the degree of calcite reprecipitation in bedrock cracks. This suggests that trace elements in speleothem deposits at the OCNM may serve as paleoclimatological proxies for precipitation, if interpreted within the context of understanding local bedrock chemistry.

Storm-scale dynamics of bacterial community composition in throughfall and stemflow

NASA Astrophysics Data System (ADS)

Van Stan, J. T., II; Teachey, M. E.; Pound, P.; Ottesen, E. A.

2017-12-01

Transport of bacteria between ecosystem spheres can significantly affect microbially-mediated biogeochemical processes. During rainfall, there is a large, temporally-concentrated exchange of bacteria between the forest phyllosphere and the pedosphere by rain dripping from canopy surfaces, as throughfall (TF), and draining to the stem, as stemflow (SF). Many phyllosphere bacteria possibly transported by TF and SF have been linked to important litter and soil processes (like cyanobacteria and actinobacteria). Despite this, no work has applied high throughput DNA sequencing to assess the community composition of bacteria transported by TF and SF. We characterized bacterial community composition for TF and SF from an epiphyte-laden (Tillandsia usneoides L., Spanish moss) southern live oak (Quercus virginiana) forest in southeastern Georgia (USA) to address two hypotheses: that bacterial community composition will differ between (1) TF and SF, and (2) TF sampled beneath bare and epiphyte-laden canopy. Variability in family-level bacterial abundance, Bray-Curtis dissimilarity, and Shannon diversity index was greater between storms than between net rainfall fluxes. In fact, TF and SF bacterial communities were relatively similar for individual storms and may be driven by pre-storm atmospheric deposition rather than the communities affixed to leaves, bark, and epiphyte surfaces.

Water isotope tracers of tropical hydroclimate in a warming world

NASA Astrophysics Data System (ADS)

Konecky, B. L.; Noone, D.; Nusbaumer, J. M.; Cobb, K. M.; Di Nezio, P. N.; Otto-Bliesner, B. L.

2016-12-01

The tropical water cycle is projected to undergo substantial changes under a warming climate, but direct meteorological observations to contextualize these changes are rare prior to the 20th century. Stable oxygen and hydrogen isotope ratios (δ18O, δD) of environmental waters preserved in geologic archives are increasingly being used to reconstruct terrestrial rainfall over many decades to millions of years. However, a rising number of new, modern-day observations and model simulations have challenged previous interpretations of these isotopic signatures. This presentation systematically evaluates the three main influences on the δ18O and δD of modern precipitation - rainfall amount, cloud type, and moisture transport - from terrestrial stations throughout the tropics, and uses this interpretive framework to understand past changes in terrestrial tropical rainfall. Results indicate that cloud type and moisture transport have a larger influence on modern δ18O and δD of tropical precipitation than previously believed, indicating that isotope records track changes in cloud characteristics and circulation that accompany warmer and cooler climate states. We use our framework to investigate isotopic records of the land-based tropical rain belt during the Last Glacial Maximum, the period of warming following the Little Ice Age, and the 21st century. Proxy and observational data are compared with water isotope-enabled simulations with the Community Earth System Model in order to discuss how global warming and cooling may influence tropical terrestrial hydroclimate.

Fog interception by Ball moss (Tillandsia recurvata)

NASA Astrophysics Data System (ADS)

Guevara-Escobar, A.; Cervantes-Jiménez, M.; Suzán-Azpiri, H.; González-Sosa, E.; Hernández-Sandoval, L.; Malda-Barrera, G.; Martínez-Díaz, M.

2010-03-01

Interception losses are a major influence in the water yield of vegetated areas. For most storms, interception results in less water reaching the ground. However, fog drip or occult precipitation can result in negative interception because small drops are deposited on all plant surfaces and subsequently fall to the ground once vegetation storage capacities are exceeded. Fog drip is normally disregarded, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions through applying simulated rain or fog. The storage capacity was proportional to dry weight mass. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543±77 vs. 325±56 mg, p=0.048). The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted. Interception storage capacity (Cmin) was 0.19 and 0.54 mm for rainfall and fog respectively. T. recurvata contributed 20% to the rain interception of their shrub hosts: Acacia farnesiana and Prosopis laevigata. Meteorological data registered during one year at Cadereyta, México showed that radiative fog formation was possible during the dry season. The results showed the potential role of T. recurvata in capturing fog, which probably is a main source of water during the dry season that supports their reproductive and physiological activity at that time. The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water recharge, because in the laboratory experiments it took up to 12 h to reach saturation conditions when fog was applied.

Simulating the complex output of rainfall and hydrological processes using the information contained in large data sets: the Direct Sampling approach.

NASA Astrophysics Data System (ADS)

Oriani, Fabio

2017-04-01

The unpredictable nature of rainfall makes its estimation as much difficult as it is essential to hydrological applications. Stochastic simulation is often considered a convenient approach to asses the uncertainty of rainfall processes, but preserving their irregular behavior and variability at multiple scales is a challenge even for the most advanced techniques. In this presentation, an overview on the Direct Sampling technique [1] and its recent application to rainfall and hydrological data simulation [2, 3] is given. The algorithm, having its roots in multiple-point statistics, makes use of a training data set to simulate the outcome of a process without inferring any explicit probability measure: the data are simulated in time or space by sampling the training data set where a sufficiently similar group of neighbor data exists. This approach allows preserving complex statistical dependencies at different scales with a good approximation, while reducing the parameterization to the minimum. The straights and weaknesses of the Direct Sampling approach are shown through a series of applications to rainfall and hydrological data: from time-series simulation to spatial rainfall fields conditioned by elevation or a climate scenario. In the era of vast databases, is this data-driven approach a valid alternative to parametric simulation techniques? [1] Mariethoz G., Renard P., and Straubhaar J. (2010), The Direct Sampling method to perform multiple-point geostatistical simulations, Water. Rerous. Res., 46(11), http://dx.doi.org/10.1029/2008WR007621 [2] Oriani F., Straubhaar J., Renard P., and Mariethoz G. (2014), Simulation of rainfall time series from different climatic regions using the direct sampling technique, Hydrol. Earth Syst. Sci., 18, 3015-3031, http://dx.doi.org/10.5194/hess-18-3015-2014 [3] Oriani F., Borghi A., Straubhaar J., Mariethoz G., Renard P. (2016), Missing data simulation inside flow rate time-series using multiple-point statistics, Environ. Model. Softw., vol. 86, pp. 264 - 276, http://dx.doi.org/10.1016/j.envsoft.2016.10.002

Effects of Changes in Irrigation Practices and Aquifer Development on Groundwater Discharge to the Jobos Bay National Estuarine Research Reserve near Salinas, Puerto Rico

USGS Publications Warehouse

Kuniansky, Eve L.; Rodriguez, Jose M.

2010-01-01

Since 1990, about 75 acres of black mangroves have died in the Jobos Bay National Estuarine Research Reserve near Salinas, Puerto Rico. Although many factors can contribute to the mortality of mangroves, changes in irrigation practices, rainfall, and water use resulted in as much as 25 feet of drawdown in the potentiometric surface of the aquifer in the vicinity of the reserve between 1986 and 2002. To clarify the issue, the U.S. Geological Survey, in cooperation with the Puerto Rico Department of Natural and Environmental Resources, conducted a study to ascertain how aquifer development and changes in irrigation practices have affected groundwater levels and groundwater flow to the Mar Negro area of the reserve. Changes in groundwater flow to the mangrove swamp and bay from 1986 to 2004 were estimated in this study by developing and calibrating a numerical groundwater flow model. The transient simulations indicate that prior to 1994, high irrigation return flows more than offset the effect of reduced groundwater withdrawals. In this case, the simulated discharge to the coast in the modeled area was 19 million gallons per day. From 1994 through 2004, furrow irrigation was completely replaced by micro-drip irrigation, thus eliminating return flows and the simulated average coastal discharge was 7 million gallons per day, a reduction of 63 percent. The simulated average groundwater discharge to the coastal mangrove swamps in the reserve from 1986 to 1993 was 2 million gallons per day, compared to an average simulated discharge of 0.2 million gallons per day from 1994 to 2004. The average annual rainfall for each of these periods was 38 inches. The groundwater discharge to the coastal mangrove swamps in the Jobos Bay National Estuarine Research Reserve was estimated at about 0.5 million gallons per day for 2003-2004 because of higher than average annual rainfall during these 2 years. The groundwater flow model was used to test five alternatives for increasing groundwater discharge to the coastal mangrove swamps to approximately 1.4 million gallons per day: (1) artificially recharging the aquifer with injection wells or (2) by increasing irrigation return flow by going back to furrow irrigation; (3) termination of groundwater withdrawals near the mangroves; (4) reduction of groundwater withdrawals at irrigation wells by 50 percent; and (5) a combination of alternatives 2 and 4 increasing irrigation return flows and decreasing irrigation withdrawals. Each alternative assumed average climatic conditions and groundwater withdrawals at 2004 rates. Alternative 1 required 1.5 million gallons per day of injected water. Alternative 2 required flooding 958 acres with a rate of 1.84 million gallons per day if no crops are grown. Alternative 3 required the termination of 2.44 million gallons per day of withdrawals to achieve 1.34 million gallons per day of discharge to the mangroves. Alternative 4 did not achieve the objective with only 0.80 million gallons per day simulated discharge to the mangroves, while requiring a 1.26 million gallon per day reduction in groundwater withdrawals. Alternative 5 required flooding fields with additional 1.13 million gallons of day and the same reduction in groundwater withdrawals, but did achieve the objective of about 1.4 million gallons per day discharge to the mangroves. Alternative 1, incorporating injection wells near the reserve required the least amount of water to raise groundwater levels and maintain discharge of 1.4 million gallons per day through the mangroves.

Chemistry of through-fall and stem-flow leachate following rainfall simulation over pinyon and juniper

USDA-ARS?s Scientific Manuscript database

We hypothesized that leachate from pinyon and juniper canopies, following rainfall events, may contribute sizable levels of solutes and C to the soil surface. We quantified solutes and dissolved carbon in stem-flow (SF) and through-fall (TF) following replicated rainfall simulation events in a pinyo...

Rainfall-runoff model parameter estimation and uncertainty evaluation on small plots

USDA-ARS?s Scientific Manuscript database

Four seasonal rainfall simulations in 2009 and 2010 were applied to a field containing 36 plots (0.75 × 2 m each), resulting in 144 runoff events. In all simulations, a constant rate of rainfall was applied, then halted 60 minutes after initiation of runoff, with plot-scale monitoring of runoff ever...

Current and future groundwater withdrawals: Effects, management and energy policy options for a semi-arid Indian watershed

NASA Astrophysics Data System (ADS)

Sishodia, Rajendra P.; Shukla, Sanjay; Graham, Wendy D.; Wani, Suhas P.; Jones, James W.; Heaney, James

2017-12-01

Effects of future expansion/intensification of irrigated agriculture on groundwater and surface water levels and availability in a semi-arid watershed were evaluated using an integrated hydrologic model (MIKE SHE/MIKE 11) in conjunction with biophysical measurements. Improved water use efficiency, water storage, and energy policy options were evaluated for their ability to sustain the future (2035) increased groundwater withdrawals. Three future withdrawal scenarios (low = 20, medium = 30, high = 50 wells/100 km2/year) based on the historical rate of growth of irrigation wells were formulated. While well drying from falling groundwater levels was limited to drought and consecutive below average rainfall years, under the current (2015) withdrawals, significant increases in frequency and duration (17-97 days/year) of well drying along with 13-26% (19-37 mm) reductions in surface flows were predicted under the future withdrawals. Higher (27-108%) energy demands of existing irrigation pumps due to declining groundwater levels and reduced hydroelectric generation due to decreased surface flows would create a vicious water-food-energy nexus in the future. Crop failure, one of the main causes of farmers' emotional distress and death in the region, is predicted to exacerbate under the future withdrawal scenarios. Shift to negative net recharge (-63 mm) and early and prolonged drying of wells under the high scenario will reduce the groundwater availability and negatively affect crop production in more than 60% and 90% of cropped areas in the Rabi (November-February) and summer (March-May) seasons, respectively during a drought year. Individual and combined demand (drip irrigation and reduced farm electricity subsidy) and supply (water storage) management options improved groundwater levels and reduced well drying by 55-97 days/year compared to business-as-usual management under the high scenario. The combined management (50% drip conversion, 50% reduction in subsidy, and enhanced water storage) mitigated well drying even during drought and consecutive below average rainfall years under the high scenario. A conservative economic evaluation for management options under the high scenario showed increases in crop production and per farmer annual profits by 987-1397 during a drought year (average household income = 1520/year). A scale-up of results showed that diverting 50% state power subsidy (6 billion for 3-6 years) can almost entirely fund the conversion to drip irrigation (4.2 billion) and water storage structures (2.9 billion) and help meet the water supply demand of a 50% increase in irrigated area under the high scenario. Converting flood to drip irrigation in 50% of irrigated area under the high scenario can reduce the electric energy consumption (7 × 106Mwh/year) and carbon footprint (6000 Mt/year) of groundwater irrigation by 24% in the state. Management options considered can potentially create a sustainable water-food-energy nexus in the larger semi-arid hard rock region. Reducing the power subsidy will require a strong political will since it has been used as a tool to win the elections in India. Considering future agricultural intensification, timely interventions are needed to ensure the livelihood and well-being of millions of small- and medium-scale farmers that rely on low storage, hard rock aquifers in the semi-arid regions of the world.

Scavenging of ice-nucleating microorganisms from the atmosphere by artificial rain events

NASA Astrophysics Data System (ADS)

Hanlon, Regina; Powers, Craig; Failor, Kevin; Vinatzer, Boris; Schmale, David

2015-04-01

Little is known about how microorganisms are scavenged from the atmosphere during rainfall. Microorganisms are abundant and diverse in rain (precipitation) collected near the surface of the earth. Some of these rain-associated microorganisms produce proteins that catalyze the nucleation of ice crystals at significantly warmer temperatures than would normally be required for ice formation, suggesting that they may play important roles in weather, including the onset of precipitation. We conducted a series of field experiments to test the hypothesis that ice-nucleating microorganisms are scavenged from the atmosphere by rainfall. Thirteen artificial rain events were conducted off the side of the Smart Road Bridge in Blacksburg, VA, USA. In each event, sterile water was dispensed over the side of the bridge (simulated rainfall), and recovered in sterile containers following gravitational settling from the side of the bridge to an open fallow agricultural field below (a distance of ~55m from the release site to the collection site). Microbes scavenged from the artificial rain events were cultured on six different types of agar media (R2A, TSA, CA; +/- cycloheximide) and the ice nucleation activity was examined for colonies cultured from the different media types. Mean CFUs scavenged by artificial rain ranged from 83 to 196 CFUs/mL across all six media types. Ice-nucleating microorganisms were recovered from 85% (11/13) of the simulated rain events, and represented about 1% of the total number of colonies assayed from each event. Strikingly, this percentage is nearly identical to the percentage of culturable ice-nucleating microorganisms occurring in about half of the natural rain events studied to date in Blacksburg, Virginia. This work expands our knowledge of the scavenging properties of rain, and suggests that at least some ice nucleators in natural precipitation events may have been stripped from the atmosphere during rainfall, thus negating their potential role in the onset of precipitation.

Evaluation of satellite and simulated rainfall products for hydrological applications in the Notwane catchment, Botswana

NASA Astrophysics Data System (ADS)

Kenabatho, P. K.; Parida, B. P.; Moalafhi, D. B.

2017-08-01

In semi-arid catchments, hydrological modeling, water resources planning and management are hampered by insufficient spatial rainfall data which is usually derived from limited rain gauge networks. Satellite products are potential candidates to augment the limited spatial rainfall data in these areas. In this paper, the utility of the Tropical Rainfall Measuring Mission (TRMM) product (3B42 v7) is evaluated using data from the Notwane catchment in Botswana. In addition, rainfall simulations obtained from a multi-site stochastic rainfall model based on the generalised linear models (GLMs) were used as additional spatial rainfall estimates. These rainfall products were compared to the observed rainfall data obtained from six (6) rainfall stations available in the catchment for the period 1998-2012. The results show that in general the two approaches produce reasonable spatial rainfall estimates. However, the TRMM products provided better spatial rainfall estimates compared to the GLM rainfall outputs on an average, as more than 90% of the monthly rainfall variations were explained by the TRMM compared to 80% from the GLMs. However, there is still uncertainty associated mainly with limited rainfall stations, and the inability of the two products to capture unusually high rainfall values in the data sets. Despite this observation, rainfall indices computed to further assess the daily rainfall products (i.e. rainfall occurrence and amounts, length of dry spells) were adequately represented by the TRMM data compared to the GLMs. Performance from the GLMs is expected to improve with addition of further rainfall predictors. A combination of these rainfall products allows for reasonable spatial rainfall estimates and temporal (short term future) rainfall simulations from the TRMM and GLMs, respectively. The results have significant implications on water resources planning and management in the catchment which has, for the past three years, been experiencing prolonged droughts as shown by the drying of Gaborone dam (currently at a record low of 1.6% full), which is the main source of water supply to the city of Gaborone and neighbouring townships in Botswana.

E-Cigarettes and "Dripping" Among High-School Youth.

PubMed

Krishnan-Sarin, Suchitra; Morean, Meghan; Kong, Grace; Bold, Krysten W; Camenga, Deepa R; Cavallo, Dana A; Simon, Patricia; Wu, Ran

2017-03-01

Electronic cigarettes (e-cigarettes) electrically heat and vaporize e-liquids to produce inhalable vapors. These devices are being used to inhale vapors produced by dripping e-liquids directly onto heated atomizers. The current study conducts the first evaluation of the prevalence rates and reasons for using e-cigarettes for dripping among high school students. In the spring of 2015, students from 8 Connecticut high schools ( n = 7045) completed anonymous surveys that examined tobacco use behaviors and perceptions. We assessed prevalence rates of ever using e-cigarettes for dripping, reasons for dripping, and predictors of dripping behaviors among those who reported ever use of e-cigarettes. Among 1080 ever e-cigarette users, 26.1% of students reported ever using e-cigarettes for dripping. Reasons for dripping included produced thicker clouds of vapor (63.5%), made flavors taste better (38.7%), produced a stronger throat hit (27.7%), curiosity (21.6%), and other (7.5%). Logistic regression analyses indicated that male adolescents (odds ratio [OR] = 1.64), whites (OR = 1.46), and those who had tried multiple tobacco products (OR = 1.34) and had greater past-month e-cigarette use frequency (OR = 1.07) were more likely to use dripping ( P s < .05). These findings indicate that a substantial portion (∼1 in 4) of high school adolescents who had ever used e-cigarettes also report using the device for dripping. Future efforts must examine the progression and toxicity of the use of e-cigarettes for dripping among youth and educate them about the potential dangers of these behaviors. Copyright © 2017 by the American Academy of Pediatrics.

Designing laboratory rainfall simulation experiments to examine the effects of a layer of vegetative ash on soil hydrology in Mediterranean areas

NASA Astrophysics Data System (ADS)

Bodí, Merche B.; Cerdà, Artemi; Doerr, Stefan H.; Mataix-Solera, Jorge

2010-05-01

Vegetative ash formed during forest wildfires often blankets the ground. Some studies have found the ash layer to increases infiltration by storing rainfall and protecting the underlying soil from sealing (Cerdà, and Doerr, 2008; Woods and Balfour, 2008), but at the same time, others identified it as a potential cause of increased overland flow due to sealing the soil pores or crusting (Mallik et al., 1984; Onda et al., 2008). The variability in the effects of ash depends mainly on the ash type and temperature of combustion, ash thickness and soil type (Kinner and Moody, 2007; Larsen et al., 2009). In order to study the effect of the ash layer on the soil hydrology and soil erosion under i) intense thunderstorms, ii) wettable and water repellent soil and iii) different ash thicknesses, rainfall simulation experiments were performed in a small plot (0.09 m2) in order to reach the highest accuracy. The simulator comprises a constant head tank of 40x40 cm with 190 hypodermic needles of 0.5 mm. A randomization screen served to break up the raindrops and ensure random drop landing positions (Kamphorst, 1987). The average of the intensities applied in the experiment was 82.5 ± 4.13 mm h-1 during 40 minutes. In order to verify the constancy of the intensity it was measured before and after each simulation. The rainfall was conducted in a metal box of 30x30 cm within 1 m of distance from the randomization screen. The slope of the box was set at 10° (17%). It is designed to collect overland flow and subsurface flow through the soil. Each rainfall simulation was conducted on 3 cm of both wettable and water repellent soil (WDPT>7200s). They are the same soil but one transformed into hydrophobic. The treatments carried out are: a) bare soil, b) 5 mm of ash depth, c) 15 mm of ash depth and d) 30 mm of ash depth, with three replicates. The ash was collected from a wildfire and the thicknesses are in the range of the reported in the literature. The first replicate was used for analysis of water repellency, infiltration pattern and ash incorporation into the soil and the other replicates are used for a second rainfall, one after 24 hours and the other after being dried 4 days in the oven at 25°C. In total there were 40 simulations. Overland flow and subsurface drainage were collected at 1-minute intervals and the forms was stored every 5 min to allow determination of sediment concentrations, yield and erosion rates. The experiment was completed with the installation of two moisture sensors at 1.5 cm of the soil and four splash cups that allowed determining the splash detachment at the end on the simulation. The importance in this series of experiments is the reproducibility and comparison of the different thicknesses of ash with the wettable and repellent soil. The results demonstrate that ash is a key factor on the post-fire soil erosion and hydrology and that rainfall simulation is a key tool to improve knowledge on low frequency - high magnitude events. References Cerdà, A. and Doerr, S.H., 2008. The effect of ash and needle cover on surface runoff and erosion in the immediate post-fire period. Catena, 74: 256-263. Kamphorst, A., 1987. A small rainfall simulator for the determination of soil erodibility. Neth J Agric Sci 35, pp. 407-415. Kinner, D.A. and Moody, J.A., 2007. Infiltration and runoff measurements on steep burned hillslope using a rainfall simulator with variable rain intensities, U.S. Department of the Interior U.S. Geological Survey. Larsen, I.J. et al., 2009. Causes of post-fire runoff and erosion: water repellency, cover, or soil sealing? Soil Science SOciety American Journal 73: 1393-1407. Mallik, A.U., Gimingham, C.H. and Rahman, A.A., 1984. Ecological effects of heater burning. I. Water infiltration, moisture retention and porosity of surface soil. Journal of Ecology, 72: 767-776. Onda, Y., Dietrich, W.E. and Booker, F., 2008. Evolution of overland flow after a severe forest fire, Point Reyes, California. Catena, 72: 13-20. Woods, S.W. and Balfour, V., 2008. The effect of ash on runoff and erosion after a forest wildfire, Montana, U.S.A. International Journal of Wildland Fire, 17(5): 535-548.

Water and nitrogen requirements of subsurface drip irrigated pomegranate

USDA-ARS?s Scientific Manuscript database

Surface drip irrigation is a well-developed practice for both annual and perennial crops. The use of subsurface drip is a well-established practice in many annual row crops, e.g. tomatoes, strawberries, lettuce. However, the use of subsurface drip on perennial crops has been slow to develop. With th...

7 CFR 2902.60 - Turbine drip oils.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 15 2011-01-01 2011-01-01 false Turbine drip oils. 2902.60 Section 2902.60... Items § 2902.60 Turbine drip oils. (a) Definition. Products that are lubricants for use in drip lubrication systems for water well line shaft bearings, water turbine bearings for irrigation pumps, and other...

7 CFR 3201.60 - Turbine drip oils.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Designated Items § 3201.60 Turbine drip oils. (a) Definition. Products that are lubricants for use in drip lubrication systems for water well line shaft bearings, water turbine bearings for irrigation pumps, and other... 7 Agriculture 15 2013-01-01 2013-01-01 false Turbine drip oils. 3201.60 Section 3201.60...

7 CFR 3201.60 - Turbine drip oils.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Designated Items § 3201.60 Turbine drip oils. (a) Definition. Products that are lubricants for use in drip lubrication systems for water well line shaft bearings, water turbine bearings for irrigation pumps, and other... 7 Agriculture 15 2012-01-01 2012-01-01 false Turbine drip oils. 3201.60 Section 3201.60...

7 CFR 3201.60 - Turbine drip oils.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Designated Items § 3201.60 Turbine drip oils. (a) Definition. Products that are lubricants for use in drip lubrication systems for water well line shaft bearings, water turbine bearings for irrigation pumps, and other... 7 Agriculture 15 2014-01-01 2014-01-01 false Turbine drip oils. 3201.60 Section 3201.60...

Simulated transient thermal infrared emissions of forest canopies during rainfall events

NASA Astrophysics Data System (ADS)

Ballard, Jerrell R.; Hawkins, William R.; Howington, Stacy E.; Kala, Raju V.

2017-05-01

We describe the development of a centimeter-scale resolution simulation framework for a theoretical tree canopy that includes rainfall deposition, evaporation, and thermal infrared emittance. Rainfall is simulated as discrete raindrops with specified rate. The individual droplets will either fall through the canopy and intersect the ground; adhere to a leaf; bounce or shatter on impact with a leaf resulting in smaller droplets that are propagated through the canopy. Surface physical temperatures are individually determined by surface water evaporation, spatially varying within canopy wind velocities, solar radiation, and water vapor pressure. Results are validated by theoretical canopy gap and gross rainfall interception models.

Continuous state-space representation of a bucket-type rainfall-runoff model: a case study with the GR4 model using state-space GR4 (version 1.0)

NASA Astrophysics Data System (ADS)

Santos, Léonard; Thirel, Guillaume; Perrin, Charles

2018-04-01

In many conceptual rainfall-runoff models, the water balance differential equations are not explicitly formulated. These differential equations are solved sequentially by splitting the equations into terms that can be solved analytically with a technique called operator splitting. As a result, only the solutions of the split equations are used to present the different models. This article provides a methodology to make the governing water balance equations of a bucket-type rainfall-runoff model explicit and to solve them continuously. This is done by setting up a comprehensive state-space representation of the model. By representing it in this way, the operator splitting, which makes the structural analysis of the model more complex, could be removed. In this state-space representation, the lag functions (unit hydrographs), which are frequent in rainfall-runoff models and make the resolution of the representation difficult, are first replaced by a so-called Nash cascade and then solved with a robust numerical integration technique. To illustrate this methodology, the GR4J model is taken as an example. The substitution of the unit hydrographs with a Nash cascade, even if it modifies the model behaviour when solved using operator splitting, does not modify it when the state-space representation is solved using an implicit integration technique. Indeed, the flow time series simulated by the new representation of the model are very similar to those simulated by the classic model. The use of a robust numerical technique that approximates a continuous-time model also improves the lag parameter consistency across time steps and provides a more time-consistent model with time-independent parameters.

Travelers' Health: Water Disinfection for Travelers

MedlinePlus

... hand-pump or gravity-drip filters with various designs and types of filter media are commercially available ... salts, thus achieving desalination. One new portable filter design incorporates hollow fiber technology, which is a cluster ...

On the dust load and rainfall relationship in South Asia: an analysis from CMIP5

NASA Astrophysics Data System (ADS)

Singh, Charu; Ganguly, Dilip; Dash, S. K.

2018-01-01

This study is aimed at examining the consistency of the relationship between load of dust and rainfall simulated by different climate models and its implication for the Indian summer monsoon system. Monthly mean outputs of 12 climate models, obtained from the archive of the Coupled Model Intercomparison Project phase 5 (CMIP5) for the period 1951-2004, are analyzed to investigate the relationship between dust and rainfall. Comparative analysis of the model simulated precipitation with the India Meteorological Department (IMD) gridded rainfall, CRU TS3.21 and GPCP version 2.2 data sets show significant differences between the spatial patterns of JJAS rainfall as well as annual cycle of rainfall simulated by various models and observations. Similarly, significant inter-model differences are also noted in the simulation of load of dust, nevertheless it is further noted that most of the CMIP5 models are able to capture the major dust sources across the study region. Although the scatter plot analysis and the lead-lag pattern correlation between the dust load and the rainfall show strong relationship between the dust load over distant sources and the rainfall in the South Asian region in individual models, the temporal scale of this association indicates large differences amongst the models. Our results caution that it would be pre-mature to draw any robust conclusions on the time scale of the relationship between dust and the rainfall in the South Asian region based on either CMIP5 results or limited number of previous studies. Hence, we would like to emphasize upon the fact that any conclusions drawn on the relationship between the dust load and the South Asian rainfall using model simulation is highly dependent on the degree of complexity incorporated in those models such as the representation of aerosol life cycle, their interaction with clouds, precipitation and other components of the climate system.

Rainfall simulation and Structure-from-Motion photogrammetry for the analysis of soil water erosion in Mediterranean vineyards.

PubMed

Prosdocimi, Massimo; Burguet, Maria; Di Prima, Simone; Sofia, Giulia; Terol, Enric; Rodrigo Comino, Jesús; Cerdà, Artemi; Tarolli, Paolo

2017-01-01

Soil water erosion is a serious problem, especially in agricultural lands. Among these, vineyards deserve attention, because they constitute for the Mediterranean areas a type of land use affected by high soil losses. A significant problem related to the study of soil water erosion in these areas consists in the lack of a standardized procedure of collecting data and reporting results, mainly due to a variability among the measurement methods applied. Given this issue and the seriousness of soil water erosion in Mediterranean vineyards, this works aims to quantify the soil losses caused by simulated rainstorms, and compare them with each other depending on two different methodologies: (i) rainfall simulation and (ii) surface elevation change-based, relying on high-resolution Digital Elevation Models (DEMs) derived from a photogrammetric technique (Structure-from-Motion or SfM). The experiments were carried out in a typical Mediterranean vineyard, located in eastern Spain, at very fine scales. SfM data were obtained from one reflex camera and a smartphone built-in camera. An index of sediment connectivity was also applied to evaluate the potential effect of connectivity within the plots. DEMs derived from the smartphone and the reflex camera were comparable with each other in terms of accuracy and capability of estimating soil loss. Furthermore, soil loss estimated with the surface elevation change-based method resulted to be of the same order of magnitude of that one obtained with rainfall simulation, as long as the sediment connectivity within the plot was considered. High-resolution topography derived from SfM revealed to be essential in the sediment connectivity analysis and, therefore, in the estimation of eroded materials, when comparing them to those derived from the rainfall simulation methodology. The fact that smartphones built-in cameras could produce as much satisfying results as those derived from reflex cameras is a high value added for using SfM. Copyright © 2016 Elsevier B.V. All rights reserved.

An improved bias correction method of daily rainfall data using a sliding window technique for climate change impact assessment

NASA Astrophysics Data System (ADS)

Smitha, P. S.; Narasimhan, B.; Sudheer, K. P.; Annamalai, H.

2018-01-01

Regional climate models (RCMs) are used to downscale the coarse resolution General Circulation Model (GCM) outputs to a finer resolution for hydrological impact studies. However, RCM outputs often deviate from the observed climatological data, and therefore need bias correction before they are used for hydrological simulations. While there are a number of methods for bias correction, most of them use monthly statistics to derive correction factors, which may cause errors in the rainfall magnitude when applied on a daily scale. This study proposes a sliding window based daily correction factor derivations that help build reliable daily rainfall data from climate models. The procedure is applied to five existing bias correction methods, and is tested on six watersheds in different climatic zones of India for assessing the effectiveness of the corrected rainfall and the consequent hydrological simulations. The bias correction was performed on rainfall data downscaled using Conformal Cubic Atmospheric Model (CCAM) to 0.5° × 0.5° from two different CMIP5 models (CNRM-CM5.0, GFDL-CM3.0). The India Meteorological Department (IMD) gridded (0.25° × 0.25°) observed rainfall data was considered to test the effectiveness of the proposed bias correction method. The quantile-quantile (Q-Q) plots and Nash Sutcliffe efficiency (NSE) were employed for evaluation of different methods of bias correction. The analysis suggested that the proposed method effectively corrects the daily bias in rainfall as compared to using monthly factors. The methods such as local intensity scaling, modified power transformation and distribution mapping, which adjusted the wet day frequencies, performed superior compared to the other methods, which did not consider adjustment of wet day frequencies. The distribution mapping method with daily correction factors was able to replicate the daily rainfall pattern of observed data with NSE value above 0.81 over most parts of India. Hydrological simulations forced using the bias corrected rainfall (distribution mapping and modified power transformation methods that used the proposed daily correction factors) was similar to those simulated by the IMD rainfall. The results demonstrate that the methods and the time scales used for bias correction of RCM rainfall data have a larger impact on the accuracy of the daily rainfall and consequently the simulated streamflow. The analysis suggests that the distribution mapping with daily correction factors can be preferred for adjusting RCM rainfall data irrespective of seasons or climate zones for realistic simulation of streamflow.

A medium scale mobile rainfall simulator for experiments on soil erosion and soil hydrology

NASA Astrophysics Data System (ADS)

Kavka, Petr; Dostál, Tomáš; Iserloh, Thomas; Davidová, Tereza; Krása, Josef; David, Václav; Vopravil, Jan; Khel, Tomáš; Bauer, Miroslav

2015-04-01

Numerous types of rainfall simulators (RS) have been used to the study the behaviour of surface runoff and sediment transport caused by rainfall. It has been documented, that reproducibility and the knowledge of test conditions are essential for gathering necessary and comparable data. Therefore medium, to large scale field rainfall simulators are very desirable. Such devices are nevertheless very much time and laboratory consuming and their weakness is especially a high water consumption. A new, compact and mobile medium scale rainfall simulator has been developed under close cooperation of CTU Prague and Research Institute of Soil Conservation. The main idea was to develop a device, which is easily to handle by 4 persons, transportable with trailer behind an off-road car and independent of additional water sources and energy. Therefore, a special construction fixed on a standard trailer has been developed. It consists of an aggregate to produce power, an electric pump and a water tank with a capacity up to 1000 l. The pump can work in reverse mode, what allows filling the water tank from any source, including stream or pond. The capacity of the tank is normally sufficient for experiments with duration up to 30 minutes. The RS itself consist of a folding arm, which carries 4 nozzles (SS Full Jet 40WSQ), controlled by electromagnetic valves, which allow to set up desired rainfall intensity by opening intervals. A simple logical unit allows programming various schemes of operation of individual nozzles, to keep low pressure fluctuation in the system. The arm is first unfolded into total length of 9.6 m and then lifted up, using simple crab to its operation position which is 2.3 - 2.65 m above terrain surface. The distance between individual nozzles had been optimized based on number of calibrating experiments on 2.4 m. There is also special space at the trailer for transportation of metal sheets and collector (for experimental plot), additional equipment, tools and measurement devices. To prevent the wind effect, whole construction can be easily covered by tarpaulin. The experimental plot has a basic size of 9.5 x 2 m, however, we usually use only 8 x 2 m. The nozzles are fed with a water pressure of about 0.8 bars. Various schemes of opened nozzles allow varying rainfall intensities between 40 and 80 mm.h-1. Rainfall collectors were used to measure spatial rainfall distribution. The spatial rainfall distribution on the entire plot is higher than 80% (Christiansen-Uniformity Coefficient). Drop size distribution and drop fall velocities were analyzed by means of a Laser Precipitation Monitor (by Thies) with satisfactory results. The mean drop sizes ranging between 0.75 - 2.00 mm depending on applied intensity. Resulting kinetic energies ranging from 188 - 582 J m-2 mm-1. The measured rainfall variables show low fluctuations throughout the tests and are therefore reproducible in field investigations. The research has been supported by the research projects SGS14/180/OHK1/3T/11 and QJ330118.

Vegetation-rainfall feedbacks across the Sahel: a combined observational and modeling study

NASA Astrophysics Data System (ADS)

Yu, Y.; Notaro, M.; Wang, F.; Mao, J.; Shi, X.; Wei, Y.

2016-12-01

The Sahel rainfall is characterized by large interannual variability. Past modeling studies have concluded that the Sahel rainfall variability is primarily driven by oceanic forcings and amplified by land-atmosphere interactions. However, the relative importance of oceanic versus terrestrial drivers has never been assessed from observations. The current understanding of vegetation's impacts on climate, i.e. positive vegetation-rainfall feedback through the albedo, moisture, and momentum mechanisms, comes from untested models. Neither the positive vegetation-rainfall feedback, nor the underlying mechanisms, has been fully resolved in observations. The current study fills the knowledge gap about the observed vegetation-rainfall feedbacks, through the application of the multivariate statistical method Generalized Equilibrium Feedback Assessment (GEFA) to observational data. According to GEFA, the observed oceanic impacts dominate over terrestrial impacts on Sahel rainfall, except in the post-monsoon period. Positive leaf area index (LAI) anomalies favor an extended, wetter monsoon across the Sahel, largely due to moisture recycling. The albedo mechanism is not responsible for this positive vegetation feedback on the seasonal-interannual time scale, which is too short for a grass-desert transition. A low-level stabilization and subsidence is observed in response to increased LAI - potentially responsible for a negative vegetation-rainfall feedback. However, the positive moisture feedback overwhelms the negative momentum feedback, resulting in an observed positive vegetation-rainfall feedback. We further applied GEFA to a fully-coupled Community Earth System Model (CESM) control run, as an example of evaluating climate models against the GEFA-based observational benchmark. In contrast to the observed positive vegetation-rainfall feedbacks, CESM simulates a negative vegetation-rainfall feedback across Sahel, peaking in the pre-monsoon season. The simulated negative feedback is largely due to the low-level stabilization caused by increased LAI. Positive moisture feedback is present in the CESM simulation, but an order weaker than the observed and weaker than the negative momentum feedback, thereby leading to the simulated negative vegetation-rainfall feedbacks.

Tropical cyclone rainfall area controlled by relative sea surface temperature

PubMed Central

Lin, Yanluan; Zhao, Ming; Zhang, Minghua

2015-01-01

Tropical cyclone rainfall rates have been projected to increase in a warmer climate. The area coverage of tropical cyclones influences their impact on human lives, yet little is known about how tropical cyclone rainfall area will change in the future. Here, using satellite data and global atmospheric model simulations, we show that tropical cyclone rainfall area is controlled primarily by its environmental sea surface temperature (SST) relative to the tropical mean SST (that is, the relative SST), while rainfall rate increases with increasing absolute SST. Our result is consistent with previous numerical simulations that indicated tight relationships between tropical cyclone size and mid-tropospheric relative humidity. Global statistics of tropical cyclone rainfall area are not expected to change markedly under a warmer climate provided that SST change is relatively uniform, implying that increases in total rainfall will be confined to similar size domains with higher rainfall rates. PMID:25761457

Future climate change enhances rainfall seasonality in a regional model of western Maritime Continent

NASA Astrophysics Data System (ADS)

Kang, Suchul; Im, Eun-Soon; Eltahir, Elfatih A. B.

2018-03-01

In this study, future changes in rainfall due to global climate change are investigated over the western Maritime Continent based on dynamically downscaled climate projections using the MIT Regional Climate Model (MRCM) with 12 km horizontal resolution. A total of nine 30-year regional climate projections driven by multi-GCMs projections (CCSM4, MPI-ESM-MR and ACCESS1.0) under multi-scenarios of greenhouse gases emissions (Historical: 1976-2005, RCP4.5 and RCP8.5: 2071-2100) from phase 5 of the Coupled Model Inter-comparison Project (CMIP5) are analyzed. Focusing on dynamically downscaled rainfall fields, the associated systematic biases originating from GCM and MRCM are removed based on observations using Parametric Quantile Mapping method in order to enhance the reliability of future projections. The MRCM simulations with bias correction capture the spatial patterns of seasonal rainfall as well as the frequency distribution of daily rainfall. Based on projected rainfall changes under both RCP4.5 and RCP8.5 scenarios, the ensemble of MRCM simulations project a significant decrease in rainfall over the western Maritime Continent during the inter-monsoon periods while the change in rainfall is not relevant during wet season. The main mechanism behind the simulated decrease in rainfall is rooted in asymmetries of the projected changes in seasonal dynamics of the meridional circulation along different latitudes. The sinking motion, which is marginally positioned in the reference simulation, is enhanced and expanded under global climate change, particularly in RCP8.5 scenario during boreal fall season. The projected enhancement of rainfall seasonality over the western Maritime Continent suggests increased risk of water stress for natural ecosystems as well as man-made water resources reservoirs.

Use of a large-scale rainfall simulator reveals novel insights into stemflow generation

NASA Astrophysics Data System (ADS)

Levia, D. F., Jr.; Iida, S. I.; Nanko, K.; Sun, X.; Shinohara, Y.; Sakai, N.

2017-12-01

Detailed knowledge of stemflow generation and its effects on both hydrological and biogoechemical cycling is important to achieve a holistic understanding of forest ecosystems. Field studies and a smaller set of experiments performed under laboratory conditions have increased our process-based knowledge of stemflow production. Building upon these earlier works, a large-scale rainfall simulator was employed to deepen our understanding of stemflow generation processes. The use of the large-scale rainfall simulator provides a unique opportunity to examine a range of rainfall intensities under constant conditions that are difficult under natural conditions due to the variable nature of rainfall intensities in the field. Stemflow generation and production was examined for three species- Cryptomeria japonica D. Don (Japanese cedar), Chamaecyparis obtusa (Siebold & Zucc.) Endl. (Japanese cypress), Zelkova serrata Thunb. (Japanese zelkova)- under both leafed and leafless conditions at several different rainfall intensities (15, 20, 30, 40, 50, and 100 mm h-1) using a large-scale rainfall simulator in National Research Institute for Earth Science and Disaster Resilience (Tsukuba, Japan). Stemflow production and rates and funneling ratios were examined in relation to both rainfall intensity and canopy structure. Preliminary results indicate a dynamic and complex response of the funneling ratios of individual trees to different rainfall intensities among the species examined. This is partly the result of different canopy structures, hydrophobicity of vegetative surfaces, and differential wet-up processes across species and rainfall intensities. This presentation delves into these differences and attempts to distill them into generalizable patterns, which can advance our theories of stemflow generation processes and ultimately permit better stewardship of forest resources. ________________ Funding note: This research was supported by JSPS Invitation Fellowship for Research in Japan (Grant Award No.: S16088) and JSPS KAKENHI (Grant Award No.: JP15H05626).

Simulation of primary-slag melting behavior in the cohesive zone of a blast furnace, considering the effect of Al{sub 2}O{sub 3}, Fe{sub t}O, and basicity in the sinter ore

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hino, Mitsutaka; Nagasaka, Tetsuya; Katsumata, Akitoshi

1999-08-01

The alumina content in the iron ore imported to Japan is increasing year by year, and some problems in blast furnace operation, due to the use of the high-alumina-containing sinter, have already been reported. In order to clarify the mechanism of the harmful effect of alumina on the blast furnace operation, the behavior of the primary melt, which is formed in the sinter at the cohesive zone of the blast furnace, has been simulated by dripping slag through an iron or oxide funnel. The effects of basicity, Al{sub 2}O{sub 3}, and Fe{sub t}O contents in the five slag systems onmore » the dripping temperature and weight of slag remaining on the funnel have been discussed. It was found that the eutectic melt formed in the sinter would play an important role in the dripping behavior of the slag in the blast furnace through the fine porosity of the reduced iron and ore particles. Al{sub 2}O{sub 3} increased the weight of the slag remaining on the funnel, and its effect became very significant in the acidic and low-Fe{sub t}O-containing slag. It was estimated that the increase of the weight of the slag remaining on the funnel by Al{sub 2}O{sub 3} in the ore could result in a harmful effect on the permeability resistance and an indirect reduction rate of the sinter in the blast furnace.« less

Mobile Interventional Stroke Teams Lead to Faster Treatment Times for Thrombectomy in Large Vessel Occlusion.

PubMed

Wei, Daniel; Oxley, Thomas J; Nistal, Dominic A; Mascitelli, Justin R; Wilson, Natalie; Stein, Laura; Liang, John; Turkheimer, Lena M; Morey, Jacob R; Schwegel, Claire; Awad, Ahmed J; Shoirah, Hazem; Kellner, Christopher P; De Leacy, Reade A; Mayer, Stephan A; Tuhrim, Stanley; Paramasivam, Srinivasan; Mocco, J; Fifi, Johanna T

2017-12-01

Endovascular recanalization treatment for acute ischemic stroke is a complex, time-sensitive intervention. Trip-and-treat is an interhospital service delivery model that has not previously been evaluated in the literature and consists of a shared mobile interventional stroke team that travels to primary stroke centers to provide on-site interventional capability. We compared treatment times between the trip-and-treat model and the traditional drip-and-ship model. We performed a retrospective analysis on 86 consecutive eligible patients with acute ischemic stroke secondary to large vessel occlusion who received endovascular treatment at 4 hospitals in Manhattan. Patients were divided into 2 cohorts: trip-and-treat (n=39) and drip-and-ship (n=47). The primary outcome was initial door-to-puncture time, defined as the time between arrival at any hospital and arterial puncture. We also recorded and analyzed the times of last known well, IV-tPA (intravenous tissue-type plasminogen activator) administration, transfer, and reperfusion. Mean initial door-to-puncture time was 143 minutes for trip-and-treat and 222 minutes for drip-and-ship ( P <0.0001). Although there was a trend in longer puncture-to-recanalization times for trip-and-treat ( P =0.0887), initial door-to-recanalization was nonetheless 79 minutes faster for trip-and-treat ( P <0.0001). There was a trend in improved admission-to-discharge change in National Institutes of Health Stroke Scale for trip-and-treat compared with drip-and-ship ( P =0.0704). Compared with drip-and-ship, the trip-and-treat model demonstrated shorter treatment times for endovascular therapy in our series. The trip-and-treat model offers a valid alternative to current interhospital stroke transfers in urban environments. © 2017 American Heart Association, Inc.

Rainfall Downscaling Conditional on Upper-air Atmospheric Predictors: Improved Assessment of Rainfall Statistics in a Changing Climate

NASA Astrophysics Data System (ADS)

Langousis, Andreas; Mamalakis, Antonis; Deidda, Roberto; Marrocu, Marino

2015-04-01

To improve the level skill of Global Climate Models (GCMs) and Regional Climate Models (RCMs) in reproducing the statistics of rainfall at a basin level and at hydrologically relevant temporal scales (e.g. daily), two types of statistical approaches have been suggested. One is the statistical correction of climate model rainfall outputs using historical series of precipitation. The other is the use of stochastic models of rainfall to conditionally simulate precipitation series, based on large-scale atmospheric predictors produced by climate models (e.g. geopotential height, relative vorticity, divergence, mean sea level pressure). The latter approach, usually referred to as statistical rainfall downscaling, aims at reproducing the statistical character of rainfall, while accounting for the effects of large-scale atmospheric circulation (and, therefore, climate forcing) on rainfall statistics. While promising, statistical rainfall downscaling has not attracted much attention in recent years, since the suggested approaches involved complex (i.e. subjective or computationally intense) identification procedures of the local weather, in addition to demonstrating limited success in reproducing several statistical features of rainfall, such as seasonal variations, the distributions of dry and wet spell lengths, the distribution of the mean rainfall intensity inside wet periods, and the distribution of rainfall extremes. In an effort to remedy those shortcomings, Langousis and Kaleris (2014) developed a statistical framework for simulation of daily rainfall intensities conditional on upper air variables, which accurately reproduces the statistical character of rainfall at multiple time-scales. Here, we study the relative performance of: a) quantile-quantile (Q-Q) correction of climate model rainfall products, and b) the statistical downscaling scheme of Langousis and Kaleris (2014), in reproducing the statistical structure of rainfall, as well as rainfall extremes, at a regional level. This is done for an intermediate-sized catchment in Italy, i.e. the Flumendosa catchment, using climate model rainfall and atmospheric data from the ENSEMBLES project (http://ensembleseu.metoffice.com). In doing so, we split the historical rainfall record of mean areal precipitation (MAP) in 15-year calibration and 45-year validation periods, and compare the historical rainfall statistics to those obtained from: a) Q-Q corrected climate model rainfall products, and b) synthetic rainfall series generated by the suggested downscaling scheme. To our knowledge, this is the first time that climate model rainfall and statistically downscaled precipitation are compared to catchment-averaged MAP at a daily resolution. The obtained results are promising, since the proposed downscaling scheme is more accurate and robust in reproducing a number of historical rainfall statistics, independent of the climate model used and the length of the calibration period. This is particularly the case for the yearly rainfall maxima, where direct statistical correction of climate model rainfall outputs shows increased sensitivity to the length of the calibration period and the climate model used. The robustness of the suggested downscaling scheme in modeling rainfall extremes at a daily resolution, is a notable feature that can effectively be used to assess hydrologic risk at a regional level under changing climatic conditions. Acknowledgments The research project is implemented within the framework of the Action «Supporting Postdoctoral Researchers» of the Operational Program "Education and Lifelong Learning" (Action's Beneficiary: General Secretariat for Research and Technology), and is co-financed by the European Social Fund (ESF) and the Greek State. CRS4 highly acknowledges the contribution of the Sardinian regional authorities.

Modelling Hydrologic Processes in the Mekong River Basin Using a Distributed Model Driven by Satellite Precipitation and Rain Gauge Observations

PubMed Central

Wang, Wei; Lu, Hui; Yang, Dawen; Sothea, Khem; Jiao, Yang; Gao, Bin; Peng, Xueting; Pang, Zhiguo

2016-01-01

The Mekong River is the most important river in Southeast Asia. It has increasingly suffered from water-related problems due to economic development, population growth and climate change in the surrounding areas. In this study, we built a distributed Geomorphology-Based Hydrological Model (GBHM) of the Mekong River using remote sensing data and other publicly available data. Two numerical experiments were conducted using different rainfall data sets as model inputs. The data sets included rain gauge data from the Mekong River Commission (MRC) and remote sensing rainfall data from the Tropic Rainfall Measurement Mission (TRMM 3B42V7). Model calibration and validation were conducted for the two rainfall data sets. Compared to the observed discharge, both the gauge simulation and TRMM simulation performed well during the calibration period (1998–2001). However, the performance of the gauge simulation was worse than that of the TRMM simulation during the validation period (2002–2012). The TRMM simulation is more stable and reliable at different scales. Moreover, the calibration period was changed to 2, 4, and 8 years to test the impact of the calibration period length on the two simulations. The results suggest that longer calibration periods improved the GBHM performance during validation periods. In addition, the TRMM simulation is more stable and less sensitive to the calibration period length than is the gauge simulation. Further analysis reveals that the uneven distribution of rain gauges makes the input rainfall data less representative and more heterogeneous, worsening the simulation performance. Our results indicate that remotely sensed rainfall data may be more suitable for driving distributed hydrologic models, especially in basins with poor data quality or limited gauge availability. PMID:27010692

Modelling Hydrologic Processes in the Mekong River Basin Using a Distributed Model Driven by Satellite Precipitation and Rain Gauge Observations.

PubMed

Wang, Wei; Lu, Hui; Yang, Dawen; Sothea, Khem; Jiao, Yang; Gao, Bin; Peng, Xueting; Pang, Zhiguo

2016-01-01

The Mekong River is the most important river in Southeast Asia. It has increasingly suffered from water-related problems due to economic development, population growth and climate change in the surrounding areas. In this study, we built a distributed Geomorphology-Based Hydrological Model (GBHM) of the Mekong River using remote sensing data and other publicly available data. Two numerical experiments were conducted using different rainfall data sets as model inputs. The data sets included rain gauge data from the Mekong River Commission (MRC) and remote sensing rainfall data from the Tropic Rainfall Measurement Mission (TRMM 3B42V7). Model calibration and validation were conducted for the two rainfall data sets. Compared to the observed discharge, both the gauge simulation and TRMM simulation performed well during the calibration period (1998-2001). However, the performance of the gauge simulation was worse than that of the TRMM simulation during the validation period (2002-2012). The TRMM simulation is more stable and reliable at different scales. Moreover, the calibration period was changed to 2, 4, and 8 years to test the impact of the calibration period length on the two simulations. The results suggest that longer calibration periods improved the GBHM performance during validation periods. In addition, the TRMM simulation is more stable and less sensitive to the calibration period length than is the gauge simulation. Further analysis reveals that the uneven distribution of rain gauges makes the input rainfall data less representative and more heterogeneous, worsening the simulation performance. Our results indicate that remotely sensed rainfall data may be more suitable for driving distributed hydrologic models, especially in basins with poor data quality or limited gauge availability.

Evaluation of rainfall simulations over West Africa in dynamically downscaled CMIP5 global circulation models

NASA Astrophysics Data System (ADS)

Akinsanola, A. A.; Ajayi, V. O.; Adejare, A. T.; Adeyeri, O. E.; Gbode, I. E.; Ogunjobi, K. O.; Nikulin, G.; Abolude, A. T.

2018-04-01

This study presents evaluation of the ability of Rossby Centre Regional Climate Model (RCA4) driven by nine global circulation models (GCMs), to skilfully reproduce the key features of rainfall climatology over West Africa for the period of 1980-2005. The seasonal climatology and annual cycle of the RCA4 simulations were assessed over three homogenous subregions of West Africa (Guinea coast, Savannah, and Sahel) and evaluated using observed precipitation data from the Global Precipitation Climatology Project (GPCP). Furthermore, the model output was evaluated using a wide range of statistical measures. The interseasonal and interannual variability of the RCA4 were further assessed over the subregions and the whole of the West Africa domain. Results indicate that the RCA4 captures the spatial and interseasonal rainfall pattern adequately but exhibits a weak performance over the Guinea coast. Findings from the interannual rainfall variability indicate that the model performance is better over the larger West Africa domain than the subregions. The largest difference across the RCA4 simulated annual rainfall was found in the Sahel. Result from the Mann-Kendall test showed no significant trend for the 1980-2005 period in annual rainfall either in GPCP observation data or in the model simulations over West Africa. In many aspects, the RCA4 simulation driven by the HadGEM2-ES perform best over the region. The use of the multimodel ensemble mean has resulted to the improved representation of rainfall characteristics over the study domain.

Effect of irrigation techniques and strategies on water footprint of growing crops

NASA Astrophysics Data System (ADS)

Chukalla, A. D.; Krol, M. S.; Hoekstra, A. Y. Y.

2014-12-01

Reducing the water footprint (WF) of growing crops, the largest water user and a significant contributor to the WF of many consumer products, plays a significant role in integrated and sustainable water management. The water footprint for growing crop is accounted by relating the crop yield with the corresponding consumptive water use (CWU), which both can be adjusted by measures that affect the crop growth and root-zone soil water balance. This study explored the scope for reducing the water footprint of irrigated crops by experimenting set of field level technical and managerial measures: (i) irrigation technologies (Furrow, sprinkler, drip and sub-surface drip), (ii) irrigation strategies (full and a range of sustained and controlled deficit) and (iii) field management options (zero, organic and synthetic mulching). Ranges of cases were also considered: (a) Arid and semi-arid environment (b) Loam and Sandy-loam soil types and (c) for Potato, Wheat and Maize crops; under (c) wet, normal and dry years. AquaCrop, the water driven crop growth and soil water balance model, offered the opportunity to systematically experiment these measures on water consumption and yield. Further, the green and blue water footprints of growing crop corresponding to each measure were computed by separating the root zone fluxes of the AquaCrop output into the green and blue soil water stocks and their corresponding fluxes. Results showed that in arid environment reduction in irrigation supply, CWU and WF up to 300 mm, 80 mm and 75 m3/tonne respectively can be achieved for Maize by a combination of organic mulching and drip technology with controlled deficit irrigation strategies (10-20-30-40% deficit with reference to the full irrigation requirement). These reductions come with a yield drop of 0.54 tonne/ha. In the same environment under the absence of mulching practice, the sub-surface drip perform better in reducing CWU and WF of irrigated crops followed by drip and furrow irrigation technique. This rank though changes in non-moisture limiting condition (wet year) drip performing better in reducing the WF of growing crops than sub-surface drip. It was observed that with all range of irrigation techniques, strategies and field management practices there is more room in reducing the WF of growing crops in loam than sandy-loam soil.

Fog interception by Ball moss (Tillandsia recurvata)

NASA Astrophysics Data System (ADS)

Guevara-Escobar, A.; Cervantes-Jiménez, M.; Suzán-Azpiri, H.; González-Sosa, E.; Hernández-Sandoval, L.; Malda-Barrera, G.; Martínez-Díaz, M.

2011-08-01

Interception losses are a major influence in the water yield of vegetated areas. For most storms, rain interception results in less water reaching the ground. However, fog interception can increase the overall water storage capacity of the vegetation and once the storage is exceeded, fog drip is a common hydrological input. Fog interception is disregarded in water budgets of semiarid regions, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions and applying simulated rain or fog. Juvenile, vegetative specimens were used to determine the potential upperbound storage capacities. The storage capacity was proportional to dry weight mass. Interception storage capacity (Cmin) was 0.19 and 0.56 mm for rainfall and fog respectively. The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted by rain. T. recurvata contributed 20 % to the rain interception capacity of their shrub hosts: Acacia farnesiana and Prosopis laevigata and; also potentially intercepted 4.8 % of the annual rainfall. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543 ± 77 vs. 325 ± 56 mg, p = 0.048). The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water recharge, because potential storage capacity is very high, in the laboratory experiments it took up to 12 h at a rate of 0.26 l h-1 to reach saturation conditions when fog was applied.

Indo-Pacific hydroclimate over the past millennium and links with global climate variabilty

NASA Astrophysics Data System (ADS)

Griffiths, M. L.; Drysdale, R.; Kimbrough, A. K.; Hua, Q.; Johnson, K. R.; Gagan, M. K.; Cole, J. E.; Cook, B. I.; Zhao, J. X.; Hellstrom, J. C.; Hantoro, W. S.

2016-12-01

The El Niño-Southern Oscillation (ENSO) and Interdecadal Pacific Oscillation (IPO) are the dominant modes of hydroclimate variability in the tropical Pacific and have far-reaching impacts on Earth's climate. Experiments combining instrumental records with climate-model simulations have highlighted the dominant role of the Pacific Walker circulation in shaping recent trends in global temperatures (Kosaka and Xie, 2013, 2016). However, the paucity of high-resolution terrestrial paleoclimate records of deep atmospheric convection over the Indo-Pacific Warm Pool (IPWP) precludes a comprehensive assessment as to role of the tropical Pacific in modulating radiative-forced shifts in global temperature on multidecadal to centennial timescales. Here we present a suite of new high-resolution oxygen-isotope records from Indo-Pacific speleothems, which, based on modern rainfall and cave drip-water monitoring studies, along with trace element (Mg/Ca, Sr/Ca) analyses, are interpreted to reflect changes in Australasian monsoon variability during the Common Era (C.E.). Our results reveal a protracted decline in southern Indonesian monsoon rainfall between 1000-1400 C.E. but stronger between 1500-1900 C.E. These centennial-scale patterns over southern Indonesia are consistent with other proxy records from the region but anti-phased with records from India and China, supporting the paradigm that Northern Hemisphere cooling increased the interhemispheric thermal gradient, displacing the Australasian ITCZ southward. However, our findings are also compatible with a recent synthesis of paleohydrologic records for the Australasian monsoon region, which, collectively, suggest that rather than moving southward during the LIA, the latitudinal range of monsoon-ITCZ migration probably contracted equatorward (Yan et al., 2015). This proposed LIA ITCZ contraction likely occurred in parallel with a strengthening of the Walker circulation (as indicated through comparison with our hydroclimate records from the central-eastern equatorial Pacific Ocean and western Indian Ocean, and eastern Australia), and thus, the tropical Pacific may have played a critical role in amplifying the radiative-forced global cooling already underway.

Comparison of different synthetic 5-min rainfall time series on the results of rainfall runoff simulations in urban drainage modelling

NASA Astrophysics Data System (ADS)

Krämer, Stefan; Rohde, Sophia; Schröder, Kai; Belli, Aslan; Maßmann, Stefanie; Schönfeld, Martin; Henkel, Erik; Fuchs, Lothar

2015-04-01

The design of urban drainage systems with numerical simulation models requires long, continuous rainfall time series with high temporal resolution. However, suitable observed time series are rare. As a result, usual design concepts often use uncertain or unsuitable rainfall data, which renders them uneconomic or unsustainable. An expedient alternative to observed data is the use of long, synthetic rainfall time series as input for the simulation models. Within the project SYNOPSE, several different methods to generate synthetic rainfall data as input for urban drainage modelling are advanced, tested, and compared. Synthetic rainfall time series of three different precipitation model approaches, - one parametric stochastic model (alternating renewal approach), one non-parametric stochastic model (resampling approach), one downscaling approach from a regional climate model-, are provided for three catchments with different sewer system characteristics in different climate regions in Germany: - Hamburg (northern Germany): maritime climate, mean annual rainfall: 770 mm; combined sewer system length: 1.729 km (City center of Hamburg), storm water sewer system length (Hamburg Harburg): 168 km - Brunswick (Lower Saxony, northern Germany): transitional climate from maritime to continental, mean annual rainfall: 618 mm; sewer system length: 278 km, connected impervious area: 379 ha, height difference: 27 m - Friburg in Brisgau (southern Germany): Central European transitional climate, mean annual rainfall: 908 mm; sewer system length: 794 km, connected impervious area: 1 546 ha, height difference 284 m Hydrodynamic models are set up for each catchment to simulate rainfall runoff processes in the sewer systems. Long term event time series are extracted from the - three different synthetic rainfall time series (comprising up to 600 years continuous rainfall) provided for each catchment and - observed gauge rainfall (reference rainfall) according national hydraulic design standards. The synthetic and reference long term event time series are used as rainfall input for the hydrodynamic sewer models. For comparison of the synthetic rainfall time series against the reference rainfall and against each other the number of - surcharged manholes, - surcharges per manhole, - and the average surcharge volume per manhole are applied as hydraulic performance criteria. The results are discussed and assessed to answer the following questions: - Are the synthetic rainfall approaches suitable to generate high resolution rainfall series and do they produce, - in combination with numerical rainfall runoff models - valid results for design of urban drainage systems? - What are the bounds of uncertainty in the runoff results depending on the synthetic rainfall model and on the climate region? The work is carried out within the SYNOPSE project, funded by the German Federal Ministry of Education and Research (BMBF).

The Holocene Indian Summer Monsoon Variability Recorded in a Stalagmite From NE India.

NASA Astrophysics Data System (ADS)

Breitenbach, S.; Plessen, B.; Oberhänsli, H.; Marwan, N.; Lund, D.; Adkins, J.; Günther, D.; Fricker, M.; Haug, G.

2007-12-01

South Asian economies depend on the timely onset of the Indian Summer Monsoon (ISM), but understanding of the ISM variability is incomplete, due to lack of information on past ISM. Our stalagmite is the first well-dated climate record from the heart of the ISM region spanning the past 11,000 years. The speleothem was collected from Krem Umsynrang Cave, located 825 m above sea level in NE India. This region is influenced by the ISM, with more than 75% of annual rainfall falling during the monsoon season. The chronology of the stalagmite is based on 36 U/Th multi-collector ICP MS dates. Our data reveal profound changes in ISM rainfall and moisture balance. A strong increase of the ISM between 11.4 and 9.3 kyr BP is followed by a gradual decline over the course of the Holocene. This may be best explained by a strong coupling between ISM and the Intertropical Convergence Zone (ITCZ), with a stronger ISM during a more northerly position of the ITCZ. This long-term trend is punctuated by centennial to multi- to sub-decadal events of a weaker ISM. The most pronounced events occurred at 10.7, 8.5-8.1, 7.4, 4.4-4.0, 3.5, 1.4, 0.3 kyr BP. The δ13C record is interpreted to reflect centennial to decadal changes in the drip rate of the stalagmite. δ13C fractionation during periods of higher drip rates (i.e. times of longer residence time of percolating water) correspond with periods of a weaker ISM as inferred from our δ18O record. Our record shows in great detail periods of weaker ISM. They provide new insights on the sensitivity of terrestrial climate archives on the Indian subcontinent. Drought events recorded in our stalagmite correspond well with intervals of severe aridity known from other regions of the Asian monsoon. Moreover, our 11,000 year climate record shows that NE India experienced its driest conditions during the last three millennia.

Irrigation and fertigation with drip and alternative micro irrigation systems in northern highbush blueberry

USDA-ARS?s Scientific Manuscript database

The effects of nitrogen (N) fertigation using conventional drip and alternative micro irrigation systems were evaluated in six cultivars of northern highbush blueberry. The drip system consisted of two laterals of drip tubing, with 2 L/h in-line emitters (point source) spaced every 0.45 m, on each s...

[Effects of soil wetting pattern on the soil water-thermal environment and cotton root water consumption under mulched drip irrigation].

PubMed

Li, Dong-wei; Li, Ming-si; Liu, Dong; Lyu, Mou-chao; Jia, Yan-hui

2015-08-01

Abstract: To explore the effects of soil wetting pattern on soil water-thermal environment and water consumption of cotton root under mulched drip irrigation, a field experiment with three drip intensities (1.69, 3.46 and 6.33 L · h(-1)), was carried out in Shihezi, Xinjiang Autonomous Region. The soil matric potential, soil temperature, cotton root distribution and water consumption were measured during the growing period of cotton. The results showed that the main factor influencing the soil temperature of cotton under plastic mulch was sunlight. There was no significant difference in the soil temperature and root water uptake under different treatments. The distribution of soil matrix suction in cotton root zone under plastic mulch was more homogeneous under ' wide and shallow' soil wetting pattern (W633). Under the 'wide and shallow' soil wetting pattern, the average difference of cotton root water consumption between inner row and outer row was 0.67 mm · d(-1), which was favorable to the cotton growing trimly at both inner and outer rows; for the 'narrow and deep' soil wetting pattern (W169), the same index was 0.88 mm · d(-1), which was unfavorable to cotton growing uniformly at both inner and outer rows. So, we should select the broad-shallow type soil wetting pattern in the design of drip irrigation under mulch.

The Effect of Rainfall Measurement Technique and Its Spatiotemporal Resolution on Discharge Predictions in the Netherlands

NASA Astrophysics Data System (ADS)

Uijlenhoet, R.; Brauer, C.; Overeem, A.; Sassi, M.; Rios Gaona, M. F.

2014-12-01

Several rainfall measurement techniques are available for hydrological applications, each with its own spatial and temporal resolution. We investigated the effect of these spatiotemporal resolutions on discharge simulations in lowland catchments by forcing a novel rainfall-runoff model (WALRUS) with rainfall data from gauges, radars and microwave links. The hydrological model used for this analysis is the recently developed Wageningen Lowland Runoff Simulator (WALRUS). WALRUS is a rainfall-runoff model accounting for hydrological processes relevant to areas with shallow groundwater (e.g. groundwater-surface water feedback). Here, we used WALRUS for case studies in a freely draining lowland catchment and a polder with controlled water levels. We used rain gauge networks with automatic (hourly resolution but low spatial density) and manual gauges (high spatial density but daily resolution). Operational (real-time) and climatological (gauge-adjusted) C-band radar products and country-wide rainfall maps derived from microwave link data from a cellular telecommunication network were also used. Discharges simulated with these different inputs were compared to observations. We also investigated the effect of spatiotemporal resolution with a high-resolution X-band radar data set for catchments with different sizes. Uncertainty in rainfall forcing is a major source of uncertainty in discharge predictions, both with lumped and with distributed models. For lumped rainfall-runoff models, the main source of input uncertainty is associated with the way in which (effective) catchment-average rainfall is estimated. When catchments are divided into sub-catchments, rainfall spatial variability can become more important, especially during convective rainfall events, leading to spatially varying catchment wetness and spatially varying contribution of quick flow routes. Improving rainfall measurements and their spatiotemporal resolution can improve the performance of rainfall-runoff models, indicating their potential for reducing flood damage through real-time control.

The hydrological behaviour of extensive and intensive green roofs in a dry climate.

PubMed

Razzaghmanesh, M; Beecham, S

2014-11-15

This paper presents the results of a hydrological investigation of four medium scale green roofs that were set up at the University of South Australia. In this study, the potential of green roofs as a source control device was investigated over a 2 year period using four medium size green roof beds comprised of two growth media types and two media depths. During the term of this study, 226 rainfall events were recorded and these were representative of the Adelaide climate. In general, there were no statistically significant differences between the rainfall and runoff parameters for the intensive and extensive beds except for peak attenuation and peak runoff delay, for which higher values were recorded in the intensive beds. Longer dry periods generally resulted in higher retention coefficients and higher retention was also recorded in warmer seasons. The average retention coefficient for intensive systems (89%) was higher than for extensive systems (74%). It was shown that rainfall depth, intensity, duration and also average dry weather period between events can change the retention performance and runoff volume of the green roofs. Comparison of green and simulated conventional roofs indicated that the former were able to mitigate the peak of runoff and could delay the start of runoff. These characteristics are important for most source control measures. The recorded rainfall and runoff data displayed a non-linear relationship. Also, the results indicated that continuous time series modelling would be a more appropriate technique than using peak rainfall intensity methods for green roof design and simulation. Copyright © 2014 Elsevier B.V. All rights reserved.

Modulation of Heavy Rainfall in the Middle East and North Africa by Madden-Julian Oscillation Using High Resolution Atmospheric General Circulation Model

NASA Astrophysics Data System (ADS)

Deng, L.; Stenchikov, G. L.; McCabe, M. F.; Bangalath, H. K.

2014-12-01

Recently, the modulation of subtropical rainfall by the dominant tropical intraseasonal signal of the Madden-Julian Oscillation (MJO), has been explored through the discussion of the MJO-convection-induced Kelvin and Rossby wave related teleconnection patterns. Our study focuses on characterizing the modulation of heavy rainfall in the Middle East and North Africa (MENA) region by the MJO, using the Geophysical Fluid Dynamics Laboratory (GFDL) global High Resolution Atmospheric Model (HIRAM) simulations (25-km; 1979-2012) and a combination of available atmospheric products from satellite, in-situ and reanalysis data. The observed Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) and the simulated SST from GFDL's global coupled carbon-climate Earth System Models (ESM2M) are employed in HIRAM to investigate the sensitivity of the simulated heavy rainfall and MJO to SST. The future trend of the extreme rainfalls and their links to the MJO response to climate change are examined using HIRAM simulations of 2012-2050 with the RCP4.5 and RCP 8.5 scenarios to advance the possibility of characterization and forecasting of future extreme rainfall events in the MENA region.

Effects of ocean-atmosphere coupling on rainfall over the Indian Ocean and northwestern Pacific Ocean during boreal summer

NASA Astrophysics Data System (ADS)

Zhou, Z. Q.; Xie, S. P.; Zhou, W.

2016-12-01

Atmosphere general circulation model (AGCM), forced with specified SST, has been widely used in climate studies. On one hand, AGCM is much faster to run compared to coupled general circulation model (CGCM). Also, the identical SST forcing allows a clean evaluation of the atmospheric component of CGCM. On the other hand, the coupling between atmosphere and ocean is missed in such atmosphere-only simulations. It is not clear how such simplification could affect the simulate of the atmosphere. In this study, the impact of ocean-atmosphere coupling is studied by comparing a CGCM simulation with an AGCM simulation which is forced with monthly SSTs specified from the CGCM simulation. Particularly, we focus on the climatology and interannual variability of rainfall over the IONWP during boreal summer. The IONWP is a unique region with a strong negative correlation between sea surface temperature (SST) and rainfall during boreal summer on the interannual time scale. The lead/lag correlation analysis suggests a negative feedback of rainfall on SST, which is only reasonably captured by CGCMs. We find that the lack of the negative feedback in AGCM not only enhances the climatology and interannual variability of rainfall but also increases the internal variability of rainfall over the IONWP. A simple mechanism is proposed to explain such enhancement. In addition, AGCM is able to capture the large-scale rainfall pattern over the IONWP during boreal summer, this is because that rainfall here is caused by remote ENSO effect on the interannual time scale. Our results herein suggest that people should be more careful when using an AGCM for climate change studies.

Errors and uncertainties in regional climate simulations of rainfall variability over Tunisia: a multi-model and multi-member approach

NASA Astrophysics Data System (ADS)

Fathalli, Bilel; Pohl, Benjamin; Castel, Thierry; Safi, Mohamed Jomâa

2018-02-01

Temporal and spatial variability of rainfall over Tunisia (at 12 km spatial resolution) is analyzed in a multi-year (1992-2011) ten-member ensemble simulation performed using the WRF model, and a sample of regional climate hindcast simulations from Euro-CORDEX. RCM errors and skills are evaluated against a dense network of local rain gauges. Uncertainties arising, on the one hand, from the different model configurations and, on the other hand, from internal variability are furthermore quantified and ranked at different timescales using simple spread metrics. Overall, the WRF simulation shows good skill for simulating spatial patterns of rainfall amounts over Tunisia, marked by strong altitudinal and latitudinal gradients, as well as the rainfall interannual variability, in spite of systematic errors. Mean rainfall biases are wet in both DJF and JJA seasons for the WRF ensemble, while they are dry in winter and wet in summer for most of the used Euro-CORDEX models. The sign of mean annual rainfall biases over Tunisia can also change from one member of the WRF ensemble to another. Skills in regionalizing precipitation over Tunisia are season dependent, with better correlations and weaker biases in winter. Larger inter-member spreads are observed in summer, likely because of (1) an attenuated large-scale control on Mediterranean and Tunisian climate, and (2) a larger contribution of local convective rainfall to the seasonal amounts. Inter-model uncertainties are globally stronger than those attributed to model's internal variability. However, inter-member spreads can be of the same magnitude in summer, emphasizing the important stochastic nature of the summertime rainfall variability over Tunisia.

Water use efficiency and crop water balance of rainfed wheat in a semi-arid environment: sensitivity of future changes to projected climate changes and soil type

NASA Astrophysics Data System (ADS)

Yang, Yanmin; Liu, De Li; Anwar, Muhuddin Rajin; O'Leary, Garry; Macadam, Ian; Yang, Yonghui

2016-02-01

Wheat production is expected to be affected by climate change through changing components of the crop water balance such as rainfall, evapotranspiration (ET), runoff and drainage. We used the Agricultural Production Systems Simulator (APSIM)-wheat model to simulate the potential impact of climate change on field water balance, ET and water use efficiency (WUE) under the SRES A2 emissions scenario. We ran APSIM with daily climate data statistically downscaled from 18 Global Circulation Models (GCMs). Twelve soil types of varying plant available water holding capacity (PAWC) at six sites across semi-arid southeastern Australia were considered. Biases in the GCM-simulated climate data were bias-corrected against observations for the 1961-1999 baseline period. However, biases in the APSIM output data relative to APSIM simulations forced with climate observations remained. A secondary bias correction was therefore performed on the APSIM outputs. Bias-corrected APSIM outputs for a future period (2021-2040) were compared with APSIM outputs generated using observations for the baseline period to obtain future changes. The results show that effective rainfall was decreased over all sites due to decreased growing season rainfall. ET was decreased through reduced soil evaporation and crop transpiration. There were no significant changes in runoff at any site. The variation in deep drainage between sites was much greater than for runoff, ranging from less than a few millimetres at the drier sites to over 100 mm at the wetter. However, in general, the averaged drainage over different soil types were not significantly different between the baseline (1961-1999) and future period of 2021-2040 ( P > 0.05). For the wetter sites, the variations in the future changes in drainage and runoff between the 18 GCMs were larger than those of the drier sites. At the dry sites, the variation in drainage decreased as PAWC increased. Overall, water use efficiency based on transpiration (WUE_T) and ET (WUE_ET) increased by 1.1 to 1.6 and 0.7 to 1.3 kg ha-1 mm-1, respectively, over the baseline historical climate. Significant relationships between changes in wheat yield and PAWC were only seen at three sites. At the dry sites, the impact of a future climate under a soil of high PAWC was less than that under one of low PAWC. Conversely, the opposite response was seen at two wetter sites, highlighting the importance of PAWC and rainfall in determining the interactive response of crops to primary components of the water balance.

Changing On Diurnal Cycle Of Rainfall In Northern Coastal Of West Java

NASA Astrophysics Data System (ADS)

Yulihastin, E.; Hadi, T. W.; Ningsih, N. S.

2017-12-01

The floods event in the north of Java was largely due to persistent of rainfall that occurred in the morning which indicated of deviation of diurnal pattern of rainfall. The shift of the phase of diurnal rainfall cycle using TRMM satellite hourly data of 3B41RT on the rainy period of 2000-2016 exhibits over land from Late Afternoon-Early Midnight (LA-EM) to morning. The peak of the cycle changes from diurnal to semidiurnal with a peak occurring in LA-EM and morning. Location of rainfall which usually occurs in the oceans shifted into near coastal area. The classification of diurnal rainfall cycles based on composite analysis shows four types: Normal (N) Type (45.6%) with one peak rainfall occurring in the afternoon until night, Diurnal (D) Type (26%) with one peak and phase opposite to normal type, Semidiurnal (SD) Type (6.5 %) with two peaks and the main peak occurring in the afternoon until night, Third Diurnal (TD) Type (21.7%) with three peaks and the main peak occurs in the morning. The classification was confirmed using the objective method of Empirical Mode Decomposition (EMD) and obtained three IMFs representing three diurnal cycle modes of Type TD (67.8%) with the main rain peak taking place in the afternoon, Type D with rain peak occurring in the early hours (18.9%), and SD type (9.9%) with the first peak occurred in the afternoon. For D Type, the results also prove that the diurnal cycle with significant deviations in amplitude occurred in February 2002, 2004, 2008, 2014, wich is the maximum rainfall occurs in the EM. It also seems that in those years, rainfall intensity is concentrated on the northern coast of West Java while in the Java Sea rainfall was minimum.

Rainfall or parameter uncertainty? The power of sensitivity analysis on grouped factors

NASA Astrophysics Data System (ADS)

Nossent, Jiri; Pereira, Fernando; Bauwens, Willy

2017-04-01

Hydrological models are typically used to study and represent (a part of) the hydrological cycle. In general, the output of these models mostly depends on their input rainfall and parameter values. Both model parameters and input precipitation however, are characterized by uncertainties and, therefore, lead to uncertainty on the model output. Sensitivity analysis (SA) allows to assess and compare the importance of the different factors for this output uncertainty. Hereto, the rainfall uncertainty can be incorporated in the SA by representing it as a probabilistic multiplier. Such multiplier can be defined for the entire time series, or several of these factors can be determined for every recorded rainfall pulse or for hydrological independent storm events. As a consequence, the number of parameters included in the SA related to the rainfall uncertainty can be (much) lower or (much) higher than the number of model parameters. Although such analyses can yield interesting results, it remains challenging to determine which type of uncertainty will affect the model output most due to the different weight both types will have within the SA. In this study, we apply the variance based Sobol' sensitivity analysis method to two different hydrological simulators (NAM and HyMod) for four diverse watersheds. Besides the different number of model parameters (NAM: 11 parameters; HyMod: 5 parameters), the setup of our sensitivity and uncertainty analysis-combination is also varied by defining a variety of scenarios including diverse numbers of rainfall multipliers. To overcome the issue of the different number of factors and, thus, the different weights of the two types of uncertainty, we build on one of the advantageous properties of the Sobol' SA, i.e. treating grouped parameters as a single parameter. The latter results in a setup with a single factor for each uncertainty type and allows for a straightforward comparison of their importance. In general, the results show a clear influence of the weights in the different SA scenarios. However, working with grouped factors resolves this issue and leads to clear importance results.

Sensitivity of CONUS Summer Rainfall to the Selection of Cumulus Parameterization Schemes in NU-WRF Seasonal Simulations

NASA Technical Reports Server (NTRS)

Iguchi, Takamichi; Tao, Wei-Kuo; Wu, Di; Peters-Lidard, Christa; Santanello, Joseph A.; Kemp, Eric; Tian, Yudong; Case, Jonathan; Wang, Weile; Ferraro, Robert;

Impact of Assimilation on Heavy Rainfall Simulations Using WRF Model: Sensitivity of Assimilation Results to Background Error Statistics

NASA Astrophysics Data System (ADS)

Rakesh, V.; Kantharao, B.

2017-03-01

Data assimilation is considered as one of the effective tools for improving forecast skill of mesoscale models. However, for optimum utilization and effective assimilation of observations, many factors need to be taken into account while designing data assimilation methodology. One of the critical components that determines the amount and propagation observation information into the analysis, is model background error statistics (BES). The objective of this study is to quantify how BES in data assimilation impacts on simulation of heavy rainfall events over a southern state in India, Karnataka. Simulations of 40 heavy rainfall events were carried out using Weather Research and Forecasting Model with and without data assimilation. The assimilation experiments were conducted using global and regional BES while the experiment with no assimilation was used as the baseline for assessing the impact of data assimilation. The simulated rainfall is verified against high-resolution rain-gage observations over Karnataka. Statistical evaluation using several accuracy and skill measures shows that data assimilation has improved the heavy rainfall simulation. Our results showed that the experiment using regional BES outperformed the one which used global BES. Critical thermo-dynamic variables conducive for heavy rainfall like convective available potential energy simulated using regional BES is more realistic compared to global BES. It is pointed out that these results have important practical implications in design of forecast platforms while decision-making during extreme weather events

A coupled synoptic-hydrological model for climate change impact assessment

NASA Astrophysics Data System (ADS)

Wilby, Robert; Greenfield, Brian; Glenny, Cathy

1994-01-01

A coupled atmospheric-hydrological model is presented. Sequences of daily rainfall occurrence for the 20 year period 1971-1990 at sites in the British Isles are related to the Lamb's Weather Types (LWT) by using conditional probabilities. Time series of circulation patterns and hence rainfall were then generated using a Markov representation of matrices of transition probabilities between weather types. The resultant precipitation data were used as input to a semidistributed catchment model to simulate daily flows. The combined model successfully reproduced aspects of the daily weather, precipitation and flow regimes. A range of synoptic scenarios were further investigated with particular reference to low flows in the River Coln, UK. The modelling approach represents a means of translating general circulation model (GCM) climate change predictions at the macro-scale into hydrological concerns at the catchment scale.

Modeling climate change impacts on combined sewer overflow using synthetic precipitation time series.

PubMed

Bendel, David; Beck, Ferdinand; Dittmer, Ulrich

2013-01-01

In the presented study climate change impacts on combined sewer overflows (CSOs) in Baden-Wuerttemberg, Southern Germany, were assessed based on continuous long-term rainfall-runoff simulations. As input data, synthetic rainfall time series were used. The applied precipitation generator NiedSim-Klima accounts for climate change effects on precipitation patterns. Time series for the past (1961-1990) and future (2041-2050) were generated for various locations. Comparing the simulated CSO activity of both periods we observe significantly higher overflow frequencies for the future. Changes in overflow volume and overflow duration depend on the type of overflow structure. Both values will increase at simple CSO structures that merely divide the flow, whereas they will decrease when the CSO structure is combined with a storage tank. However, there is a wide variation between the results of different precipitation time series (representative for different locations).

The relative importance of different grass components in controlling runoff and erosion on a hillslope under simulated rainfall

NASA Astrophysics Data System (ADS)

Li, Changjia; Pan, Chengzhong

2018-03-01

The effects of vegetation cover on overland flow and erosion processes on hillslopes vary with vegetation type and spatial distribution and the different vegetation components, including the above- and below-ground biomass. However, few attempts have been made to quantify how these factors affect erosion processes. Field experimental plots (5 m × 2 m) with a slope of approximately 25° were constructed and simulated rainfall (60 mm hr-1) (Rainfall) and simulated rainfall combined with upslope overland flow (20 L min-1) (Rainfall + Flow) were applied. Three grass species were planted, specifically Astragalus adsurgens (A. adsurgens), Medicago sativa (M. sativa) and Cosmos bipinnatus (C. bipinnatus). To isolate and quantify the relative contributions of the above-ground grass parts (stems, litter cover and leaves) and the roots to reducing surface runoff and erosion, each of the three grass species was subjected to three treatments: intact grass control (IG), no litter or leaves (only the grass stems and roots were reserved) (NLL), and only roots remaining (OR). The results showed that planting grass significantly reduced overland flow rate and velocity and sediment yield, and the mean reductions were 21.8%, 29.1% and 67.1%, respectively. M. sativa performed the best in controlling water and soil losses due to its thick canopy and dense, fine roots. Grasses reduced soil erosion mainly during the early stage of overland flow generation. The above-ground grass parts primarily contributed to reducing overland flow rate and velocity, with mean relative contributions of 64% and 86%, respectively. The roots played a predominant role in reducing soil erosion, with mean contribution of 84%. Due to the impact of upslope inflow, overland flow rate and velocity and sediment yield increased under the Rainfall + Flow conditions. The results suggest that grass species on downslope parts of semi-arid hillslopes performed better in reducing water and soil losses. This study is beneficial for forage selection, allocation and management practices, such as forage harvesting, when implementing restoration strategies to control soil and water losses.

A new hydrological model for estimating extreme floods in the Alps

NASA Astrophysics Data System (ADS)

Receanu, R. G.; Hertig, J.-A.; Fallot, J.-M.

2012-04-01

Protection against flooding is very important for a country like Switzerland with a varied topography and many rivers and lakes. Because of the potential danger caused by extreme precipitation, structural and functional safety of large dams must be guaranteed to withstand the passage of an extreme flood. We introduce a new distributed hydrological model to calculate the PMF from a PMP which is spatially and temporally distributed using clouds. This model has permitted the estimation of extreme floods based on the distributed PMP and the taking into account of the specifics of alpine catchments, in particular the small size of the basins, the complex topography, the large lakes, snowmelt and glaciers. This is an important evolution compared to other models described in the literature, as they mainly use a uniform distribution of extreme precipitation all over the watershed. This paper presents the results of calculation with the developed rainfall-runoff model, taking into account measured rainfall and comparing results to observed flood events. This model includes three parts: surface runoff, underground flow and melting snow. Two Swiss watersheds are studied, for which rainfall data and flow rates are available for a considerably long period, including several episodes of heavy rainfall with high flow events. From these events, several simulations are performed to estimate the input model parameters such as soil roughness and average width of rivers in case of surface runoff. Following the same procedure, the parameters used in the underground flow simulation are also estimated indirectly, since direct underground flow and exfiltration measurements are difficult to obtain. A sensitivity analysis of the parameters is performed at the first step to define more precisely the boundary and initial conditions. The results for the two alpine basins, validated with the Nash equation, show a good correlation between the simulated and observed flows. This good correlation shows that the model is valid and gives us the confidence that the results can be extrapolated to phenomena of extreme rainfall of PMP type.

The role of stochastic storms on hillslope runoff generation and connectivity in a dryland basin

NASA Astrophysics Data System (ADS)

Michaelides, K.; Singer, M. B.; Mudd, S. M.

2016-12-01

Despite low annual rainfall, dryland basins can generate significant surface runoff during certain rainstorms, which can cause flash flooding and high rates of erosion. However, it remains challenging to anticipate the nature and frequency of runoff generation in hydrological systems which are driven by spatially and temporally stochastic rainstorms. In particular, the stochasticity of rainfall presents challenges to simulating the hydrological response of dryland basins and understanding flow connectivity from hillslopes to the channel. Here we simulate hillslope runoff generation using rainfall characteristics produced by a simple stochastic rainfall generator, which is based on a rich rainfall dataset from the Walnut Gulch Experimental Watershed (WGEW) in Arizona, USA. We assess hillslope runoff generation using the hydrological model, COUP2D, driven by a subset of characteristic output from multiple ensembles of decadal monsoonal rainfall from the stochastic rainfall generator. The rainfall generator operates across WGEW by simulating storms with areas smaller than the basin and enables explicit characterization of rainfall characteristics at any location. We combine the characteristics of rainfall intensity and duration with data on rainstorm area and location to model the surface runoff properties (depth, velocity, duration, distance downslope) on a range of hillslopes within the basin derived from LiDAR analysis. We also analyze connectivity of flow from hillslopes to the channel for various combinations of hillslopes and storms. This approach provides a framework for understanding spatial and temporal dynamics of runoff generation and connectivity that is faithful to the hydrological characteristics of dryland environments.

Stochastic generation of hourly rainstorm events in Johor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nojumuddin, Nur Syereena; Yusof, Fadhilah; Yusop, Zulkifli

2015-02-03

Engineers and researchers in water-related studies are often faced with the problem of having insufficient and long rainfall record. Practical and effective methods must be developed to generate unavailable data from limited available data. Therefore, this paper presents a Monte-Carlo based stochastic hourly rainfall generation model to complement the unavailable data. The Monte Carlo simulation used in this study is based on the best fit of storm characteristics. Hence, by using the Maximum Likelihood Estimation (MLE) and Anderson Darling goodness-of-fit test, lognormal appeared to be the best rainfall distribution. Therefore, the Monte Carlo simulation based on lognormal distribution was usedmore » in the study. The proposed model was verified by comparing the statistical moments of rainstorm characteristics from the combination of the observed rainstorm events under 10 years and simulated rainstorm events under 30 years of rainfall records with those under the entire 40 years of observed rainfall data based on the hourly rainfall data at the station J1 in Johor over the period of 1972–2011. The absolute percentage error of the duration-depth, duration-inter-event time and depth-inter-event time will be used as the accuracy test. The results showed the first four product-moments of the observed rainstorm characteristics were close with the simulated rainstorm characteristics. The proposed model can be used as a basis to derive rainfall intensity-duration frequency in Johor.« less

A spatio-temporal evaluation of the WRF physical parameterisations for numerical rainfall simulation in semi-humid and semi-arid catchments of Northern China

NASA Astrophysics Data System (ADS)

Tian, Jiyang; Liu, Jia; Wang, Jianhua; Li, Chuanzhe; Yu, Fuliang; Chu, Zhigang

2017-07-01

Mesoscale Numerical Weather Prediction systems can provide rainfall products at high resolutions in space and time, playing an increasingly more important role in water management and flood forecasting. The Weather Research and Forecasting (WRF) model is one of the most popular mesoscale systems and has been extensively used in research and practice. However, for hydrologists, an unsolved question must be addressed before each model application in a different target area. That is, how are the most appropriate combinations of physical parameterisations from the vast WRF library selected to provide the best downscaled rainfall? In this study, the WRF model was applied with 12 designed parameterisation schemes with different combinations of physical parameterisations, including microphysics, radiation, planetary boundary layer (PBL), land-surface model (LSM) and cumulus parameterisations. The selected study areas are two semi-humid and semi-arid catchments located in the Daqinghe River basin, Northern China. The performance of WRF with different parameterisation schemes is tested for simulating eight typical 24-h storm events with different evenness in space and time. In addition to the cumulative rainfall amount, the spatial and temporal patterns of the simulated rainfall are evaluated based on a two-dimensional composed verification statistic. Among the 12 parameterisation schemes, Scheme 4 outperforms the other schemes with the best average performance in simulating rainfall totals and temporal patterns; in contrast, Scheme 6 is generally a good choice for simulations of spatial rainfall distributions. Regarding the individual parameterisations, Single-Moment 6 (WSM6), Yonsei University (YSU), Kain-Fritsch (KF) and Grell-Devenyi (GD) are better choices for microphysics, planetary boundary layers (PBL) and cumulus parameterisations, respectively, in the study area. These findings provide helpful information for WRF rainfall downscaling in semi-humid and semi-arid areas. The methodologies to design and test the combination schemes of parameterisations can also be regarded as a reference for generating ensembles in numerical rainfall predictions using the WRF model.

Intra-Seasonal Rainfall Variations and Linkage with Kharif Crop Production: An Attempt to Evaluate Predictability of Sub-Seasonal Rainfall Events

NASA Astrophysics Data System (ADS)

Singh, Ankita; Ghosh, Kripan; Mohanty, U. C.

2018-03-01

The sub-seasonal variation of Indian summer monsoon rainfall highly impacts Kharif crop production in comparison with seasonal total rainfall. The rainfall frequency and intensity corresponding to various rainfall events are found to be highly related to crop production and therefore, the predictability of such events are considered to be diagnosed. Daily rainfall predictions are made available by one of the coupled dynamical model National Centers for Environmental Prediction Climate Forecast System (NCEPCFS). A large error in the simulation of daily rainfall sequence influences to take up a bias correction and for that reason, two approaches are used. The bias-corrected GCM is able to capture the inter-annual variability in rainfall events. Maximum prediction skill of frequency of less rainfall (LR) event is observed during the month of September and a similar result is also noticed for moderate rainfall event with maximum skill over the central parts of the country. On the other hand, the impact of rainfall weekly rainfall intensity is evaluated against the Kharif rice production. It is found that weekly rainfall intensity during July is having a significant impact on Kharif rice production, but the corresponding skill was found very low in GCM. The GCM are able to simulate the less and moderate rainfall frequency with significant skill.

Characteristics of aggregation of daily rainfall in a middle-latitudes region during a climate variability in annual rainfall amount

NASA Astrophysics Data System (ADS)

Lucero, Omar A.; Rozas, Daniel

Climate variability in annual rainfall occurs because the aggregation of daily rainfall changes. A topic open to debate is whether that change takes place because rainfall becomes more intense, or because it rains more often, or a combination of both. The answer to this question is of interest for water resources planning, hydrometeorological design, and agricultural management. Change in the number of rainy days can cause major disruptions in hydrological and ecological systems, with important economic and social effects. Furthermore, the characteristics of daily rainfall aggregation in ongoing climate variability provide a reference to evaluate the capability of GCM to simulate changes in the hydrologic cycle. In this research, we analyze changes in the aggregation of daily rainfall producing a climate positive trend in annual rainfall in central Argentina, in the southern middle-latitudes. This state-of-the-art agricultural region has a semiarid climate with dry and wet seasons. Weather effects in the region influence world-market prices of several crops. Results indicate that the strong positive trend in seasonal and annual rainfall amount is produced by an increase in number of rainy days. This increase takes place in the 3-month periods January-March (summer) and April-June (autumn). These are also the 3-month periods showing a positive trend in the mean of annual rainfall. The mean of the distribution of annual number of rainy day (ANRD) increased in 50% in a 36-year span (starting at 44 days/year). No statistically significant indications on time changes in the probability distribution of daily rainfall amount were found. Non-periodic fluctuations in the time series of annual rainfall were analyzed using an integral wavelet transform. Fluctuations with a time scale of about 10 and 20 years construct the trend in annual rainfall amount. These types of non-periodic fluctuations have been observed in other regions of the world. This suggests that results of this research could have further geographical validity.

Using Hydrus 2-D to assess the emitters optimal position for Eggplants under surface and subsurface drip irrigation

NASA Astrophysics Data System (ADS)

Ghazouani, Hiba; Autovino, Dario; Douh, Boutheina; Boujelben, Abdel Hamid; Provenznao, Giuseppe; Rallo, Giovanni

2014-05-01

The main objective of the work is to assess the emitters optimal position for Eggplant crop (Solanum melongena L.) in a sandy loam soil irrigated with surface or subsurface drip irrigation systems, by means of field measurements and simulations carried out with Hydrus-2D model. Initially, the performance of the model is evaluated on the basis of the comparison between simulated soil water contents (SWC) and the corresponding measured in two plots, in which laterals with coextruded emitters are laid on the soil surface (T0) and at 20 cm depth (T20), respectively. In order to choose the best position of the lateral, the results of different simulation runs, carried out by changing the installation depth of the lateral (5 cm, 15 cm and 45 cm) were compared in terms of ratio between actual transpiration and total amount of water provided during the entire growing season (WUE). Experiments were carried out, from April to June 2007, at Institut Supérieur Agronomique de Chott Mériem (Sousse, Tunisia). In the two plots, plants were spaced 0.40 m along the row and 1.2 m between the rows. Each plot was irrigated by means of laterals with coextruded emitters spaced 0.40 m and discharging a flow rate equal to 4.0 l h-1 at a nominal pressure of 100 kPa. In each plot, spatial and temporal variability of SWCs were acquired with a Time Domain Reflectometry probe (Trime-FM3), on a total of four 70 cm long access tubes, installed along the direction perpendicular to the plant row, at distances of 0, 20, 40 and 60 cm from the emitter. Irrigation water was supplied, accounting for the rainfall, every 7-10 days at the beginning of the crop cycle (March-April) and approximately once a week during the following stages till the harvesting (May-June), for a total of 15 one-hour watering. To run the model, soil evaporation, Ep, and crop transpiration, Tp were determined according to the modified FAO Penman-Monteith equation and the dual crop coefficient approach, whereas soil hydraulics and rooting system parameters were experimentally determined. Simulated SWCs resulted fairly close to the corresponding measured at different distances from the emitter and therefore the model was able to predict SWCs in the root zone with values of the Root Mean Square Error generally lower than 4%. This result is consequent to the appropriate schematization of the root distribution, as well as of the root water uptake. Simulations also evidenced the contribute of soil evaporation losses when laterals are installed from the soil surface to a 20 cm depth, whereas significant water losses by deep percolation occured at the highest installation depth. The values of WUE associated to the different examined installation depths tend to a very slight increase when the position of the lateral rises from 0 to 15 cm and start to decrease for the higher depths.

Field Verification Program (Upland Disposal): Prediction of Surface Runoff Water Quality from Black Rock Harbor Dredged Material Placed in an Upland Disposal Site.

DTIC Science & Technology

1987-03-01

Simulator was similar to the original rotating disk-type rainfall simulator but had several important design modifications ( Westerdahl and Skogerboe...exist- ing vegetation on the soil surface ( Westerdahl and Skogerboe 1982). A multiple-peaked natural storm event was selected from field data and pro... Westerdahl and Skogerboe 1982) and has been used as a standard storm event for comparison to natural storm events (Laws and Parsons 1943). Similar

Synergetic Combination of Radar Information and Gauge Measurements - with the Conflict between Two Types of Data Being Removed via Displacement and Downscaling

NASA Astrophysics Data System (ADS)

Yan, J.; Bardossy, A.

2017-12-01

Rain gauges are the foundation in hydrology to collect rainfall data, however, gauge measurements alone are limited at representing the complete rainfall distribution. On the other hand, the reliability of radar data is often limited because of the errors in the radar signal (e.g. clutter, variation of the vertical reflectivity profile, beam blockage, attenuation, etc). Thus, merging radar information and gauge rainfall measurements is in an area of active research. The merging method proposed here is to use the radar data in its [0, 1] format (p-value). The actual precipitation values come from the gauge measurements. At each measurement location, two types of data are available, the radar p-value and the gauge measurement in mm. It happens very frequently that there exists a contradiction between these two types of data. A very likely reason is the influence of the unknown process between the radar measurement height and the surface onto which the hydrometeors fall. A method for quantification of the impact of the unknown process is proposed to fix the conflict, but only to a certain degree. Another possible source that can explain the discrepancy between these two types of data is discretization, i.e., the spatial variability cannot be identified by coarse discretization. Thus, downscaling is also considered to further remove the conflict. Based on the p-value from the radar data and the precipitation from the gauge measurements, a distribution function can be built up. The ultimate goal is to simulate the precipitation field for nowcasting purpose. The conditions to be fulfilled by the simulated field is as the following: honoring the measurements at the gauge locations; sharing a similar pattern with the radar image; preserving the inherent covariance structure. The simulation approach employed here is random mixing. The study domain is located in Reutlingen, Baden-Wuerttemberg, Germany (Latitude 48.49N, Longitude 9.20E). The radar data are obtained from a C-band radar (Radar Tuerkheim) whereas the gauge measurements come from stations with 1-min time resolution.

Estimating preservative release from treated wood exposed to precipitation

Treesearch

Stan Lebow; Patricia Lebow; Daniel Foster

2008-01-01

Accelerated leaching methods are needed to better estimate emissions from treated wood used above ground or above water. In this study, we evaluated leaching methods using continuous immersion, dip immersion, and simulated rainfall approaches. Copper and/or boron emissions were measured for specimens treated with either chromated copper arsenate Type C (CCA-C) or a...

Simulation of the Onset of the Southeast Asian Monsoon During 1997 and 1998: The Impact of Surface Processes

NASA Technical Reports Server (NTRS)

Wang, Yansen; Tao, W.-K.; Lau, K.-M.; Wetzel, Peter J.

2003-01-01

The onset of the southeast Asian monsoon during 1997 and 1998 was simulated with a coupled mesoscale atmospheric model (MM5) and a detailed land surface model. The rainfall results from the simulations were compared with observed satellite data fiom the TRMM (Tropical Rainfall Measuring Mission) TMI (TRMM Microwave Imager) and GPCP (Global Precipitation Climatology Project). The simulation with the land surface model captured basic signatures of the monsoon onset processes and associated rainfall statistics. The sensitivity tests indicated that land surface processes had a greater impact on the simulated rainfall results than that of a small sea surface temperature change during the onset period. In both the 1997 and 1998 cases, the simulations were significantly improved by including the land surface processes. The results indicated that land surface processes played an important role in modifying the low-level wind field over two major branches of the circulation; the southwest low-level flow over the Indo- China peninsula and the northern cold front intrusion from southern China. The surface sensible and latent heat exchange between the land and atmosphere modified the lowlevel temperature distribution and gradient, and therefore the low-level. The more realistic forcing of the sensible and latent heat from the detailed land surface model improved the monsoon rainfall and associated wind simulation.

Ecogeochemistry of the subsurface food web at pH 0-2.5 in Iron Mountain, California, U.S.A.

USGS Publications Warehouse

Robbins, E.I.; Rodgers, T.M.; Alpers, Charles N.; Nordstrom, D. Kirk

2000-01-01

Pyrite oxidation in the underground mining environment of Iron Mountain, California, has created the most acidic pH values ever reported in aquatic systems. Sulfate values as high as 120 000 mg l-1 and iron as high as 27 600 mg l-1 have been measured in the mine water, which also carries abundant other dissolved metals including Al, Zn, Cu, Cd, Mn, Sb and Pb. Extreme acidity and high metal concentrations apparently do not preclude the presence of an underground acidophilic food web, which has developed with bacterial biomass at the base and heliozoans as top predators. Slimes, oil-like films, flexible and inflexible stalactites, sediments, water and precipitates were found to have distinctive communities. A variety of filamentous and non-filamentous bacteria grew in slimes in water having pH values < 1.0. Fungal hyphae colonize stalactites dripping pH 1.0 water; they may help to form these drip structures. Motile hypotrichous ciliates and bdelloid rotifers are particularly abundant in slimes having a pH of 1.5. Holdfasts of the iron bacterium Leptothrix discophora attach to biofilms covering pools of standing water having a pH of 2.5 in the mine. The mine is not a closed environment - people, forced air flow and massive flushing during high intensity rainfall provide intermittent contact between the surface and underground habitats, so the mine ecosystem probably is not a restricted one.

Ecogeochemistry of the subsurface food web at pH 0–2.5 in Iron Mountain, California, U.S.A.

USGS Publications Warehouse

Robbins, Eleanora I.; Rodgers , Teresa M.; Alpers, Charles N.; Nordstrom, D. Kirk

2000-01-01

Pyrite oxidation in the underground mining environment of Iron Mountain, California, has created the most acidic pH values ever reported in aquatic systems. Sulfate values as high as 120 000 mg l−1 and iron as high as 27 600 mg l−1 have been measured in the mine water, which also carries abundant other dissolved metals including Al, Zn, Cu, Cd, Mn, Sb and Pb. Extreme acidity and high metal concentrations apparently do not preclude the presence of an underground acidophilic food web, which has developed with bacterial biomass at the base and heliozoans as top predators. Slimes, oil-like films, flexible and inflexible stalactites, sediments, water and precipitates were found to have distinctive communities. A variety of filamentous and non-filamentous bacteria grew in slimes in water having pH values <1.0. Fungal hyphae colonize stalactites dripping pH 1.0 water; they may help to form these drip structures. Motile hypotrichous ciliates and bdelloid rotifers are particularly abundant in slimes having a pH of 1.5. Holdfasts of the iron bacterium Leptothrix discophora attach to biofilms covering pools of standing water having a pH of 2.5 in the mine. The mine is not a closed environment – people, forced air flow and massive flushing during high intensity rainfall provide intermittent contact between the surface and underground habitats, so the mine ecosystem probably is not a restricted one.

Analysis of convection-permitting simulations for capturing heavy rainfall events over Myanmar Region

NASA Astrophysics Data System (ADS)

Acierto, R. A. E.; Kawasaki, A.

2017-12-01

Perennial flooding due to heavy rainfall events causes strong impacts on the society and economy. With increasing pressures of rapid development and potential for climate change impacts, Myanmar experiences a rapid increase in disaster risk. Heavy rainfall hazard assessment is key on quantifying such disaster risk in both current and future conditions. Downscaling using Regional Climate Models (RCM) such as Weather Research and Forecast model have been used extensively for assessing such heavy rainfall events. However, usage of convective parameterizations can introduce large errors in simulating rainfall. Convective-permitting simulations have been used to deal with this problem by increasing the resolution of RCMs to 4km. This study focuses on the heavy rainfall events during the six-year (2010-2015) wet period season from May to September in Myanmar. The investigation primarily utilizes rain gauge observation for comparing downscaled heavy rainfall events in 4km resolution using ERA-Interim as boundary conditions using 12km-4km one-way nesting method. The study aims to provide basis for production of high-resolution climate projections over Myanmar in order to contribute for flood hazard and risk assessment.

WEPP and ANN models for simulating soil loss and runoff in a semi-arid Mediterranean region.

PubMed

Albaradeyia, Issa; Hani, Azzedine; Shahrour, Isam

2011-09-01

This paper presents the use of both the Water Erosion Prediction Project (WEPP) and the artificial neural network (ANN) for the prediction of runoff and soil loss in the central highland mountainous of the Palestinian territories. Analyses show that the soil erosion is highly dependent on both the rainfall depth and the rainfall event duration rather than on the rainfall intensity as mostly mentioned in the literature. The results obtained from the WEPP model for the soil loss and runoff disagree with the field data. The WEPP underestimates both the runoff and soil loss. Analyses conducted with the ANN agree well with the observation. In addition, the global network models developed using the data of all the land use type show a relatively unbiased estimation for both runoff and soil loss. The study showed that the ANN model could be used as a management tool for predicting runoff and soil loss.

Factors Contributing to the Off-Target Transport of Pyrethroid Insecticides From Urban Surfaces

PubMed Central

Jorgenson, Brant C.; Wissel-Tyson, Christopher; Young, Thomas M.

2013-01-01

Pyrethroid insecticides used in an urban and suburban context have been found in urban creek sediments and associated with toxicity in aquatic bioassays. The objectives of this study were to evaluate the main factors contributing to the off-target transport of pyrethroid insecticides from surfaces typical of residential landscapes. Controlled rainfall simulations over concrete, bare soil, and turf plots treated individually with pyrethroid insecticides in a suspension concentrate, an emulsifiable concentrate, or a granule formulation were conducted at different rainfall intensities and different product set-time intervals. Pyrethroid mass washoff varied by several orders of magnitude between experimental treatments. Suspension concentrate product application to concrete yielded significantly greater washoff than any other treatment; granule product application to turf yielded the least washoff. Fractional losses at 10 L of runoff ranged from 25.9% to 0.011% of pyrethroid mass applied and 10 L nominal mass losses ranged from 3,970 to 0.18 μg. Mass washoff depended principally on formulation and surface type combination and to a lesser degree set-time interval and rainfall intensity. Treatment effects were analyzed by ANOVA on main factors of formulation, surface type, and set time. Factor effects were not purely additive; a significant interaction between formulation and surface type was noted. PMID:22784034

Aspect of ECMWF downscaled Regional Climate Modeling in simulating Indian summer monsoon rainfall and dependencies on lateral boundary conditions

NASA Astrophysics Data System (ADS)

Ghosh, Soumik; Bhatla, R.; Mall, R. K.; Srivastava, Prashant K.; Sahai, A. K.

2018-03-01

Climate model faces considerable difficulties in simulating the rainfall characteristics of southwest summer monsoon. In this study, the dynamical downscaling of European Centre for Medium-Range Weather Forecast's (ECMWF's) ERA-Interim (EIN15) has been utilized for the simulation of Indian summer monsoon (ISM) through the Regional Climate Model version 4.3 (RegCM-4.3) over the South Asia Co-Ordinated Regional Climate Downscaling EXperiment (CORDEX) domain. The complexities of model simulation over a particular terrain are generally influenced by factors such as complex topography, coastal boundary, and lack of unbiased initial and lateral boundary conditions. In order to overcome some of these limitations, the RegCM-4.3 is employed for simulating the rainfall characteristics over the complex topographical conditions. For reliable rainfall simulation, implementations of numerous lower boundary conditions are forced in the RegCM-4.3 with specific horizontal grid resolution of 50 km over South Asia CORDEX domain. The analysis is considered for 30 years of climatological simulation of rainfall, outgoing longwave radiation (OLR), mean sea level pressure (MSLP), and wind with different vertical levels over the specified region. The dependency of model simulation with the forcing of EIN15 initial and lateral boundary conditions is used to understand the impact of simulated rainfall characteristics during different phases of summer monsoon. The results obtained from this study are used to evaluate the activity of initial conditions of zonal wind circulation speed, which causes an increase in the uncertainty of regional model output over the region under investigation. Further, the results showed that the EIN15 zonal wind circulation lacks sufficient speed over the specified region in a particular time, which was carried forward by the RegCM output and leads to a disrupted regional simulation in the climate model.

Performance of Sorghum Varieties under Variable Rainfall in Central Tanzania

PubMed Central

Tumbo, S. D.; Kihupi, N. I.; Rwehumbiza, Filbert B.

2017-01-01

Rainfall variability has a significant impact on crop production with manifestations in frequent crop failure in semiarid areas. This study used the parameterized APSIM crop model to investigate how rainfall variability may affect yields of improved sorghum varieties based on long-term historical rainfall and projected climate. Analyses of historical rainfall indicate a mix of nonsignificant and significant trends on the onset, cessation, and length of the growing season. The study confirmed that rainfall variability indeed affects yields of improved sorghum varieties. Further analyses of simulated sorghum yields based on seasonal rainfall distribution indicate the concurrence of lower grain yields with the 10-day dry spells during the cropping season. Simulation results for future sorghum response, however, show that impacts of rainfall variability on sorghum will be overridden by temperature increase. We conclude that, in the event where harms imposed by moisture stress in the study area are not abated, even improved sorghum varieties are likely to perform poorly. PMID:28536708

Performance of Sorghum Varieties under Variable Rainfall in Central Tanzania.

PubMed

Msongaleli, Barnabas M; Tumbo, S D; Kihupi, N I; Rwehumbiza, Filbert B

2017-01-01

Rainfall variability has a significant impact on crop production with manifestations in frequent crop failure in semiarid areas. This study used the parameterized APSIM crop model to investigate how rainfall variability may affect yields of improved sorghum varieties based on long-term historical rainfall and projected climate. Analyses of historical rainfall indicate a mix of nonsignificant and significant trends on the onset, cessation, and length of the growing season. The study confirmed that rainfall variability indeed affects yields of improved sorghum varieties. Further analyses of simulated sorghum yields based on seasonal rainfall distribution indicate the concurrence of lower grain yields with the 10-day dry spells during the cropping season. Simulation results for future sorghum response, however, show that impacts of rainfall variability on sorghum will be overridden by temperature increase. We conclude that, in the event where harms imposed by moisture stress in the study area are not abated, even improved sorghum varieties are likely to perform poorly.

Soil sealing and vesicular layer formation as initial structure development and its effect on infiltration

NASA Astrophysics Data System (ADS)

Badorreck, A.; Gerke, H. H.; Weller, U.; Vontobel, P.

2009-04-01

In the Lusatia mining district (NE-Germany) an artificial catchment was constructed to study initial ecosystem development and runoff generation. As a key process in this early stage, we investigate the surface structure dynamics as it strongly influences erosion, infiltration, matter dynamics, and vegetation establishment. The presented work focuses on observations of soil pore structure formation at the surface at five sites in the catchment and in an adjacent "younger" area composed of comparable sediments. Moreover we've conducted infiltration experiments in the lab and field to relate the soil pore structure to the hydraulic properties. The surface soil was sampled in cylindrical rings (10 cm³) down to 2 cm depth from which bulk density profiles were obtained using X-ray computed tomography (CT) (at UFZ- Halle, Germany) with a resolution of 0.084 mm. The influence of structure on infiltration was investigated using neutron radiography (at the NEUTRA facility of the Paul-Scherrer-Institut, Villigen, Switzerland) to visualise two-dimensional (2D) infiltration patterns. The slab-type samples were equilibrated to different initial water contents and then exposed to drip irrigation (to simulate rainfall) while a series of neutron radiographs were taken. In addition, field measurements with a miniature tension infiltrometer were conduced. The micro-tomographies exhibit formation of surface sealing whose thickness and intensity vary with silt and clay content. The CT images show several coarser- and finer-textured micro-layers at the sample surfaces that were formed as a consequence of repeated washing in of finer particles in underlying coarser sediment. In micro-depressions, the uppermost layers consist of sorted fine sand and silt due to wind erosion. Similar as for desert pavements, a vesicular pore structure developed in these sediments on top, but also scattered in fine sand- and silt-enriched micro-layers. The infiltration rates were severely affected by the surface crusts; however, the rates were independent of the vesicular pore layer.

Patient Selection for Drip and Ship Thrombolysis in Acute Ischemic Stroke

PubMed Central

Lyerly, Michael J.; Albright, Karen C.; Boehme, Amelia K.; Shahripour, Reza Bavarsad; Donnelly, John P.; Houston, James T.; Rawal, Pawan V.; Kapoor, Niren; Alvi, Muhammad; Sisson, April; Alexandrov, Anne W.; Alexandrov, Andrei V.

2017-01-01

Objectives The drip and ship model is a method used to deliver thrombolysis to acute stroke patients in facilities lacking onsite neurology coverage. We sought to determine whether our drip and ship population differs from patients treated directly at our stroke center (direct presenters). Methods We retrospectively reviewed consecutive patients who received thrombolysis at an outside facility with subsequent transfer to our center between 2009 and 2011. Patients received thrombolysis after telephone consultation with a stroke specialist. We examined demographics, vascular risk factors, laboratory values, and stroke severity in drip and ship patients compared with direct presenters. Results Ninety-six patients were identified who received thrombolysis by drip and ship compared with 212 direct presenters. The two groups did not differ with respect to sex, ethnicity, vascular risk factors, or admission glucose. The odds ratio (OR) of arriving at our hospital as a drip and ship for someone 80 years or older was 0.31 (95% confidence interval [CI] 0.15–0.61, P < 0.001). Only 21% of drip and ship patients were black versus 38% of direct presenters (OR 0.434, 95% CI 0.25–0.76, P = 0.004). Even after stratifying by age (<80 vs ≥80), a smaller proportion of drip and ship patients were black (OR 0.44, 95% CI 0.24–0.81, P = 0.008). Furthermore, we found that fewer black patients with severe strokes arrived by drip and ship (OR 0.33, 95% CI 0.11–0.98, P = 0.0028). Conclusions Our study showed that a smaller proportion of blacks and older adults arrived at our center by the drip and ship model. This may reflect differences in how patients are selected for thrombolysis and transfer to a higher level of care. PMID:26192934

Patient Selection for Drip and Ship Thrombolysis in Acute Ischemic Stroke.

PubMed

Lyerly, Michael J; Albright, Karen C; Boehme, Amelia K; Shahripour, Reza Bavarsad; Donnelly, John P; Houston, James T; Rawal, Pawan V; Kapoor, Niren; Alvi, Muhammad; Sisson, April; Alexandrov, Anne W; Alexandrov, Andrei V

2015-07-01

The drip and ship model is a method used to deliver thrombolysis to acute stroke patients in facilities lacking onsite neurology coverage. We sought to determine whether our drip and ship population differs from patients treated directly at our stroke center (direct presenters). We retrospectively reviewed consecutive patients who received thrombolysis at an outside facility with subsequent transfer to our center between 2009 and 2011. Patients received thrombolysis after telephone consultation with a stroke specialist. We examined demographics, vascular risk factors, laboratory values, and stroke severity in drip and ship patients compared with direct presenters. Ninety-six patients were identified who received thrombolysis by drip and ship compared with 212 direct presenters. The two groups did not differ with respect to sex, ethnicity, vascular risk factors, or admission glucose. The odds ratio (OR) of arriving at our hospital as a drip and ship for someone 80 years or older was 0.31 (95% confidence interval [CI] 0.15-0.61, P < 0.001). Only 21% of drip and ship patients were black versus 38% of direct presenters (OR 0.434, 95% CI 0.25-0.76, P = 0.004). Even after stratifying by age (<80 vs ≥80), a smaller proportion of drip and ship patients were black (OR 0.44, 95% CI 0.24-0.81, P = 0.008). Furthermore, we found that fewer black patients with severe strokes arrived by drip and ship (OR 0.33, 95% CI 0.11-0.98, P = 0.0028). Our study showed that a smaller proportion of blacks and older adults arrived at our center by the drip and ship model. This may reflect differences in how patients are selected for thrombolysis and transfer to a higher level of care.

High Severity Wildfire Effect On Rainfall Infiltration And Runoff: A Cellular Automata Based Simulation

NASA Astrophysics Data System (ADS)

Vergara-Blanco, J. E.; Leboeuf-Pasquier, J.; Benavides-Solorio, J. D. D.

2017-12-01

A simulation software that reproduces rainfall infiltration and runoff for a storm event in a particular forest area is presented. A cellular automaton is utilized to represent space and time. On the time scale, the simulation is composed by a sequence of discrete time steps. On the space scale, the simulation is composed of forest surface cells. The software takes into consideration rain intensity and length, individual forest cell soil absorption capacity evolution, and surface angle of inclination. The software is developed with the C++ programming language. The simulation is executed on a 100 ha area within La Primavera Forest in Jalisco, Mexico. Real soil texture for unburned terrain and high severity wildfire affected terrain is employed to recreate the specific infiltration profile. Historical rainfall data of a 92 minute event is used. The Horton infiltration equation is utilized for infiltration capacity calculation. A Digital Elevation Model (DEM) is employed to reproduce the surface topography. The DEM is displayed with a 3D mesh graph where individual surface cells can be observed. The plot colouring renders water content development at the cell level throughout the storm event. The simulation shows that the cumulative infiltration and runoff which take place at the surface cell level depend on the specific storm intensity, fluctuation and length, overall terrain topography, cell slope, and soil texture. Rainfall cumulative infiltration for unburned and high severity wildfire terrain are compared: unburned terrain exhibits a significantly higher amount of rainfall infiltration.It is concluded that a cellular automaton can be utilized with a C++ program to reproduce rainfall infiltration and runoff under diverse soil texture, topographic and rainfall conditions in a forest setting. This simulation is geared for an optimization program to pinpoint the locations of a series of forest land remediation efforts to support reforestation or to minimize runoff.

High-Resolution Simulation of Hurricane Bonnie (1998). Part 1; The Organization of Vertical Motion

NASA Technical Reports Server (NTRS)

Braun, Scott A.; Montgomery, Michael T.; Pu, Zhaoxia

2003-01-01

Hurricanes are well known for their strong winds and heavy rainfall, particularly in the intense rainband (eyewall) surrounding the calmer eye of the storm. In some hurricanes, the rainfall is distributed evenly around the eye so that it has a donut shape on radar images. In other cases, the rainfall is concentrated on one side of the eyewall and nearly absent on the other side and is said to be asymmetric. This study examines how the vertical air motions that produce the rainfall are distributed within the eyewall of an asymmetric hurricane and the factors that cause this pattern of rainfall. We use a sophisticated numerical forecast model to simulate Hurricane Bonnie, which occurred in late August of 1998 during a special NASA field experiment designed to study hurricanes. The simulation results suggest that vertical wind shear (a rapid change in wind speed or direction with height) caused the asymmetric rainfall and vertical air motion patterns by tilting the hurricane vortex and favoring upward air motions in the direction of tilt. Although the rainfall in the hurricane eyewall may surround more than half of the eye, the updrafts that produce the rainfall are concentrated in very small-scale, intense updraft cores that occupy only about 10% of the eyewall area. The model simulation suggests that the timing and location of individual updraft cores are controlled by intense, small-scale vortices (regions of rapidly swirling flow) in the eyewall and that the updrafts form when the vortices encounter low-level air moving into the eyewall.

Relationships between southeastern Australian rainfall and sea surface temperatures examined using a climate model

NASA Astrophysics Data System (ADS)

Watterson, I. G.

2010-05-01

Rainfall in southeastern Australia has declined in recent years, particularly during austral autumn over the state of Victoria. A recent study suggests that sea surface temperature (SST) variations in both the Indonesian Throughflow (ITF) region and in a meridional dipole in the central Indian Ocean have influenced Victorian late autumn rainfall since 1950. However, it remains unclear to what extent SSTs in these and other regions force such a teleconnection. Analysis of a 1080 year simulation by the climate model CSIRO Mk3.5 shows that the model Victorian rainfall is correlated rather realistically with SSTs but that part of the above relationships is due to the model ENSO. Furthermore, the remote patterns of pressure, rainfall, and land temperature greatly diminish when the data are lagged by 1 month, suggesting that the true forcing by the persisting SSTs is weak. In a series of simulations of the atmospheric Mk3.5 with idealized SST anomalies, raised SSTs to the east of Indonesia lower the simulated Australian rainfall, while those to the west raise it. A positive ITF anomaly lowers pressure over Australia, but with little effect on Victorian rainfall. The meridional dipole and SSTs to the west and southeast of Australia have little direct effect on southeastern Australia in the model. The results suggest that tropical SSTs predominate as an influence on Victorian rainfall. However, the SST indices appear to explain only a fraction of the observed trend, which in the case of decadal means remains within the range of unforced variability simulated by Mk3.5.

Use of High-Resolution Satellite Observations to Evaluate Cloud and Precipitation Statistics from Cloud-Resolving Model Simulations

NASA Astrophysics Data System (ADS)

Zhou, Y.; Tao, W.; Hou, A. Y.; Zeng, X.; Shie, C.

2007-12-01

The cloud and precipitation statistics simulated by 3D Goddard Cumulus Ensemble (GCE) model for different environmental conditions, i.e., the South China Sea Monsoon Experiment (SCSMEX), CRYSTAL-FACE, and KAWJEX are compared with Tropical Rainfall Measuring Mission (TRMM) TMI and PR rainfall measurements and as well as cloud observations from the Earth's Radiant Energy System (CERES) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments. It is found that GCE is capable of simulating major convective system development and reproducing total surface rainfall amount as compared with rainfall estimated from the soundings. The model presents large discrepancies in rain spectrum and vertical hydrometer profiles. The discrepancy in the precipitation field is also consistent with the cloud and radiation observations. The study will focus on the effects of large scale forcing and microphysics to the simulated model- observation discrepancies.

Cascade rainfall disaggregation application in U.S. Central Plains

USDA-ARS?s Scientific Manuscript database

Hourly rainfall are increasingly used in complex, process-based simulations of the environment. Long records of daily rainfall are common, but long continuous records of hourly rainfall are rare and must be developed. A Multiplicative Random Cascade (MRC) model is proposed to disaggregate observed d...

Spatial and temporal variability in the R-5 infiltration data set: Déjà vu and rainfall-runoff simulations

NASA Astrophysics Data System (ADS)

Loague, Keith; Kyriakidis, Phaedon C.

1997-12-01

This paper is a continuation of the event-based rainfall-runoff model evaluation study reported by Loague and Freeze [1985[. Here we reevaluate the performance of a quasi-physically based rainfall-runoff model for three large events from the well-known R-5 catchment. Five different statistical criteria are used to quantitatively judge model performance. Temporal variability in the large R-5 infiltration data set [Loague and Gander, 1990] is filtered by working in terms of permeability. The transformed data set is reanalyzed via geostatistical methods to model the spatial distribution of permeability across the R-5 catchment. We present new estimates of the spatial distribution of infiltration that are in turn used in our rainfall-runoff simulations with the Horton rainfall-runoff model. The new rainfall-runoff simulations, complicated by reinfiltration impacts at the smaller scales of characterization, indicate that the near-surface hydrologic response of the R-5 catchment is most probably dominated by a combination of the Horton and Dunne overland flow mechanisms.

Hydrologic Analysis of Ungauged Catchments For The Supply of Water For Irrigation On Railway Embankment Batters

NASA Astrophysics Data System (ADS)

Gyasi-Agyei, Y.; Nissen, D.

Water has been identified as a key component to the success of grass establishment on railway embankment batters (side slope) within Central Queensland, Australia, to control erosion. However, the region under study being semi-arid experiences less than 600 mm average annual rainfall occurring on about 60 days of the year. Culverts and bridges are integral part of railway embankments. They are used to cross water courses, be it an ephemeral creek or just a surface runoff path. Surface runoff through an ungauged railway embankment culvert is diverted to a temporary excavated pond located at the downstream side of the hydraulic structure. The temporary excavated pond water is used to feed an automated drip irrigation system, with solar as a source of energy to drive a pump. Railway embankment batter erosion remediation is timed in the wet season when irrigation is used to supplement natural rainfall. Hydrologic analysis of ungauged catchments for sizing the temporary excavated pond is presented. It is based on scenarios of runoff coefficient and curve number, and mass curve (Rippl diagram). Three years of continuous rainfall data (1997/1998 -1999/2000) were used to design a pond. The performance of the designed pond was evaluated in a field experiment during the next wet season (2000/2001). It supplied adequate water for irrigation as predicted by the hydrologic analysis during the grass establishment. This helped to achieve 100% grass cover on the railway embankment batter within 12 weeks. The proposed irrigation system has been demonstrated t o be feasible and cost effective.

A simplified rainfall-runoff stochastic simulation method for an application of the SCHADEX method to ungauged catchments.

NASA Astrophysics Data System (ADS)

Penot, David; Paquet, Emmanuel; Lang, Michel

2014-05-01

SCHADEX is a probabilistic method for extreme flood estimation, developed and applied since 2006 at Electricité de France (EDF) for dam spillway design [Paquet et al., 2013]. SCHADEX is based on a semi-continuous rainfall-runoff simulation process. The method has been built around two models: a Multi-Exponential Weather Pattern (MEWP) distribution for rainfall probability estimation [Garavaglia et al., 2010] and the MORDOR hydrological model. To use SCHADEX in ungauged context, rainfall distribution and hydrological model must be regionalized. The regionalization of the MEWP rainfall distribution can be managed with SPAZM, a daily rainfall interpolator [Gottardi et al., 2012] which provides reasonable estimates of point and areal rainfall up to hight quantiles. The main issue remains to regionalize MORDOR which is heavily parametrized. A much more simple model has been considered: the SCS model. It is a well known model for event simulation [USDA SCS, 1985; Beven, 2003] and it relies on only one parameter. Then, the idea is to use the SCS model instead of MORDOR within a simplified stochastic simulation scheme to produce a distribution of flood volume from an exhaustive crossing between rainy events and catchment saturation hazards. The presentation details this process and its capacity to generate a runoff distribution based on catchment areal rainfall distribution. The simulation method depends on a unique parameter Smax, the maximum initial loss of the catchment. Then an initial loss S (between zero and Smax) can be drawn to account for the variability of catchment state (between dry and saturated). The distribution of initial loss (or conversely, of catchment saturation, as modeled by MORDOR) seems closely linked to the catchment's regime, therefore easily to regionalize. The simulation takes into account a snow contribution for snow driven catchments, and an antecedent runoff. The presentation shows the results of this stochastic procedure applied on 80 French catchments and its capacity to represent the asymptotic behaviour of the runoff distribution. References: K. J. Beven. Rainfall-Runoff modelling The Primer, British Library, 2003. F. Garavaglia, J. Gailhard, E. Paquet, M. Lang, R. Garçon, and P. Bernardara. Introducing a rainfall compound distribution model based on weather patterns sub-sampling. Hydrology and Earth System Sciences, 14(6):951-964, 2010. F. Gottardi, C. Obled, J. Gailhard, and E. Paquet. Statistical reanalysis of precipitation fields based on ground network data and weather patterns : Application over french mountains. Journal of Hydrology, 432-433:154-167, 2012. ISSN 0022-1694. E. Paquet, F. Garavaglia, R Garçon, and J. Gailhard. The schadex method : a semi-continuous rainfall-runoff simulation for extreme flood estimation. Journal of Hydrology, 2013. USDA SCS, National Engineering Handbook, Supplement A, Section 4, Chapter 10. Whashington DC, 1985.

Effects of rainfall patterns and land cover on the subsurface flow generation of sloping Ferralsols in southern China

PubMed Central

Yang, Jie; Tang, Chongjun; Chen, Lihua; Liu, Yaojun; Wang, Lingyun

2017-01-01

Rainfall patterns and land cover are two important factors that affect the runoff generation process. To determine the surface and subsurface flows associated with different rainfall patterns on sloping Ferralsols under different land cover types, observational data related to surface and subsurface flows from 5 m × 15 m plots were collected from 2010 to 2012. The experiment was conducted to assess three land cover types (grass, litter cover and bare land) in the Jiangxi Provincial Soil and Water Conservation Ecological Park. During the study period, 114 natural rainfall events produced subsurface flow and were divided into four groups using k-means clustering according to rainfall duration, rainfall depth and maximum 30-min rainfall intensity. The results showed that the total runoff and surface flow values were highest for bare land under all four rainfall patterns and lowest for the covered plots. However, covered plots generated higher subsurface flow values than bare land. Moreover, the surface and subsurface flows associated with the three land cover types differed significantly under different rainfall patterns. Rainfall patterns with low intensities and long durations created more subsurface flow in the grass and litter cover types, whereas rainfall patterns with high intensities and short durations resulted in greater surface flow over bare land. Rainfall pattern I had the highest surface and subsurface flow values for the grass cover and litter cover types. The highest surface flow value and lowest subsurface flow value for bare land occurred under rainfall pattern IV. Rainfall pattern II generated the highest subsurface flow value for bare land. Therefore, grass or litter cover are able to convert more surface flow into subsurface flow under different rainfall patterns. The rainfall patterns studied had greater effects on subsurface flow than on total runoff and surface flow for covered surfaces, as well as a greater effect on surface flows associated with bare land. PMID:28792507

Rainfall pattern variability as climate change impact in The Wallacea Region

NASA Astrophysics Data System (ADS)

Pujiastuti, I.; Nurjani, E.

2018-04-01

The objective of the study is to observe the characteristic variability of rainfall pattern in the city located in every rainfall type, local (Kendari), monsoon (Manado), and equatorial (Palu). The result will be compared to determine which has the most significantly precipitation changing due to climate change impact. Rainfall variability in Indonesia illustrates precipitation variation thus the important variability is the variability of monthly rainfall. Monthly precipitation data for the period of 1961-2010 are collected from Indonesian Agency for Meteorological, Climatological, and Geophysical Agency. This data is calculated with the normal test statistical method to analyze rainfall variability. The result showed the pattern of trend and variability of rainfall in every city with the own characteristic which determines the rainfall type. Moreover, there is comparison of rainfall pattern changing between every rainfall type. This information is useful for climate change mitigation and adaptation strategies especially in water resource management form precipitation as well as the occurrence of meteorological disasters.

Sampling errors for satellite-derived tropical rainfall - Monte Carlo study using a space-time stochastic model

NASA Technical Reports Server (NTRS)

Bell, Thomas L.; Abdullah, A.; Martin, Russell L.; North, Gerald R.

1990-01-01

Estimates of monthly average rainfall based on satellite observations from a low earth orbit will differ from the true monthly average because the satellite observes a given area only intermittently. This sampling error inherent in satellite monitoring of rainfall would occur even if the satellite instruments could measure rainfall perfectly. The size of this error is estimated for a satellite system being studied at NASA, the Tropical Rainfall Measuring Mission (TRMM). First, the statistical description of rainfall on scales from 1 to 1000 km is examined in detail, based on rainfall data from the Global Atmospheric Research Project Atlantic Tropical Experiment (GATE). A TRMM-like satellite is flown over a two-dimensional time-evolving simulation of rainfall using a stochastic model with statistics tuned to agree with GATE statistics. The distribution of sampling errors found from many months of simulated observations is found to be nearly normal, even though the distribution of area-averaged rainfall is far from normal. For a range of orbits likely to be employed in TRMM, sampling error is found to be less than 10 percent of the mean for rainfall averaged over a 500 x 500 sq km area.

A protocol for conducting rainfall simulation to study soil runoff.

PubMed

Kibet, Leonard C; Saporito, Louis S; Allen, Arthur L; May, Eric B; Kleinman, Peter J A; Hashem, Fawzy M; Bryant, Ray B

2014-04-03

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The objective of this study was to characterize the effects of antecedent soil moisture content on the fate and transport of surface applied commercial urea, a common form of nitrogen (N) fertilizer, following a rainfall event that occurs within 24 hr after fertilizer application. Although urea is assumed to be readily hydrolyzed to ammonium and therefore not often available for transport, recent studies suggest that urea can be transported from agricultural soils to coastal waters where it is implicated in harmful algal blooms. A rainfall simulator was used to apply a consistent rate of uniform rainfall across packed soil boxes that had been prewetted to different soil moisture contents. By controlling rainfall and soil physical characteristics, the effects of antecedent soil moisture on urea loss were isolated. Wetter soils exhibited shorter time from rainfall initiation to runoff initiation, greater total volume of runoff, higher urea concentrations in runoff, and greater mass loadings of urea in runoff. These results also demonstrate the importance of controlling for antecedent soil moisture content in studies designed to isolate other variables, such as soil physical or chemical characteristics, slope, soil cover, management, or rainfall characteristics. Because rainfall simulators are designed to deliver raindrops of similar size and velocity as natural rainfall, studies conducted under a standardized protocol can yield valuable data that, in turn, can be used to develop models for predicting the fate and transport of pollutants in runoff.

A Protocol for Conducting Rainfall Simulation to Study Soil Runoff

PubMed Central

Kibet, Leonard C.; Saporito, Louis S.; Allen, Arthur L.; May, Eric B.; Kleinman, Peter J. A.; Hashem, Fawzy M.; Bryant, Ray B.

2014-01-01

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The objective of this study was to characterize the effects of antecedent soil moisture content on the fate and transport of surface applied commercial urea, a common form of nitrogen (N) fertilizer, following a rainfall event that occurs within 24 hr after fertilizer application. Although urea is assumed to be readily hydrolyzed to ammonium and therefore not often available for transport, recent studies suggest that urea can be transported from agricultural soils to coastal waters where it is implicated in harmful algal blooms. A rainfall simulator was used to apply a consistent rate of uniform rainfall across packed soil boxes that had been prewetted to different soil moisture contents. By controlling rainfall and soil physical characteristics, the effects of antecedent soil moisture on urea loss were isolated. Wetter soils exhibited shorter time from rainfall initiation to runoff initiation, greater total volume of runoff, higher urea concentrations in runoff, and greater mass loadings of urea in runoff. These results also demonstrate the importance of controlling for antecedent soil moisture content in studies designed to isolate other variables, such as soil physical or chemical characteristics, slope, soil cover, management, or rainfall characteristics. Because rainfall simulators are designed to deliver raindrops of similar size and velocity as natural rainfall, studies conducted under a standardized protocol can yield valuable data that, in turn, can be used to develop models for predicting the fate and transport of pollutants in runoff. PMID:24748061

Evaluating Satellite-based Rainfall Estimates for Basin-scale Hydrologic Modeling

NASA Astrophysics Data System (ADS)

Yilmaz, K. K.; Hogue, T. S.; Hsu, K.; Gupta, H. V.; Mahani, S. E.; Sorooshian, S.

2003-12-01

The reliability of any hydrologic simulation and basin outflow prediction effort depends primarily on the rainfall estimates. The problem of estimating rainfall becomes more obvious in basins with scarce or no rain gauges. We present an evaluation of satellite-based rainfall estimates for basin-scale hydrologic modeling with particular interest in ungauged basins. The initial phase of this study focuses on comparison of mean areal rainfall estimates from ground-based rain gauge network, NEXRAD radar Stage-III, and satellite-based PERSIANN (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks) and their influence on hydrologic model simulations over several basins in the U.S. Six-hourly accumulations of the above competing mean areal rainfall estimates are used as input to the Sacramento Soil Moisture Accounting Model. Preliminary experiments for the Leaf River Basin in Mississippi, for the period of March 2000 - June 2002, reveals that seasonality plays an important role in the comparison. There is an overestimation during the summer and underestimation during the winter in satellite-based rainfall with respect to the competing rainfall estimates. The consequence of this result on the hydrologic model is that simulated discharge underestimates the major observed peak discharges during early spring for the basin under study. Future research will entail developing correction procedures, which depend on different factors such as seasonality, geographic location and basin size, for satellite-based rainfall estimates over basins with dense rain gauge network and/or radar coverage. Extension of these correction procedures to satellite-based rainfall estimates over ungauged basins with similar characteristics has the potential for reducing the input uncertainty in ungauged basin modeling efforts.

Soil conservation service curve number: How to take into account spatial and temporal variability

NASA Astrophysics Data System (ADS)

Rianna, M.; Orlando, D.; Montesarchio, V.; Russo, F.; Napolitano, F.

2012-09-01

The most commonly used method to evaluate rainfall excess, is the Soil Conservation Service (SCS) runoff curve number model. This method is based on the determination of the CN valuethat is linked with a hydrological soil group, cover type, treatment, hydrologic condition and antecedent runoff condition. To calculate the antecedent runoff condition the standard procedure needs to calculate the rainfall over the entire basin during the five days previous to the beginning of the event in order to simulate and then to use that volume of rainfall to calculate the antecedent moisture condition (AMC). This is necessary in order to obtain the correct curve number value. The value of the modified parameter is then kept constant throughout the whole event. The aim of this work is to evaluate the possibility of improving the curve number method. The various assumptions are focused on modifying those related to rainfall and the determination of an AMC condition and their role in the determination of the value of the curve number parameter. In order to consider the spatial variability we assumed that the rainfall which influences the AMC and the CN value does not account for the rainfall over the entire basin, but for the rainfall within a single cell where the basin domain is discretized. Furthermore, in order to consider the temporal variability of rainfall we assumed that the value of the CN of the single cell is not maintained constant during the whole event, but instead varies throughout it according to the time interval used to define the AMC conditions.

Systematic errors in the simulation of the Asian summer monsoon: the role of rainfall variability on a range of time and space scales

NASA Astrophysics Data System (ADS)

Martin, Gill; Levine, Richard; Klingaman, Nicholas; Bush, Stephanie; Turner, Andrew; Woolnough, Steven

2015-04-01

Despite considerable efforts worldwide to improve model simulations of the Asian summer monsoon, significant biases still remain in climatological seasonal mean rainfall distribution, timing of the onset, and northward and eastward extent of the monsoon domain (Sperber et al., 2013). Many modelling studies have shown sensitivity to convection and boundary layer parameterization, cloud microphysics and land surface properties, as well as model resolution. Here we examine the problems in representing short-timescale rainfall variability (related to convection parameterization), problems in representing synoptic-scale systems such as monsoon depressions (related to model resolution), and the relationship of each of these with longer-term systematic biases. Analysis of the spatial distribution of rainfall intensity on a range of timescales ranging from ~30 minutes to daily, in the MetUM and in observations (where available), highlights how rainfall biases in the South Asian monsoon region on different timescales in different regions can be achieved in models through a combination of the incorrect frequency and/or intensity of rainfall. Over the Indian land area, the typical dry bias is related to sub-daily rainfall events being too infrequent, despite being too intense when they occur. In contrast, the wet bias regions over the equatorial Indian Ocean are mainly related to too frequent occurrence of lower-than-observed 3-hourly rainfall accumulations which result in too frequent occurrence of higher-than-observed daily rainfall accumulations. This analysis sheds light on the model deficiencies behind the climatological seasonal mean rainfall biases that many models exhibit in this region. Changing physical parameterizations alters this behaviour, with associated adjustments in the climatological rainfall distribution, although the latter is not always improved (Bush et al., 2014). This suggests a more complex interaction between the diabatic heating and the large-scale circulation than is indicated by the intensity and frequency of rainfall alone. Monsoon depressions and low pressure systems are important contributors to monsoon rainfall over central and northern India, areas where MetUM climate simulations typically show deficient monsoon rainfall. Analysis of MetUM climate simulations at resolutions ranging from N96 (~135km) to N512 (~25km) suggests that at lower resolution the numbers and intensities of monsoon depressions and low pressure systems and their associated rainfall are very low compared with re-analyses/observations. We show that there are substantial increases with horizontal resolution, but resolution is not the only factor. Idealised simulations, either using nudged atmospheric winds or initialised coupled hindcasts, which improve (strengthen) the mean state monsoon and cyclonic circulation over the Indian peninsula, also result in a substantial increase in monsoon depressions and associated rainfall. This suggests that a more realistic representation of monsoon depressions is possible even at lower resolution if the larger-scale systematic error pattern in the monsoon is improved.

Challenges with space-time rainfall in urban hydrology highlighted with a semi-distributed model using C-band and X-band radar data

NASA Astrophysics Data System (ADS)

da Silva Rocha Paz, Igor; Ichiba, Abdellah; Skouri-Plakali, Ilektra; Lee, Jisun; Gires, Auguste; Tchiguirinskaia, Ioulia; Schertzer, Daniel

2017-04-01

Climate change and global warming are expected to make precipitation events more frequent, more severe and more local. This may have serious consequences for human health, the environment, cultural heritage, economic activities, utilities and public service providers. Then precipitation risk and water management is a key challenge for densely populated urban areas. Applications derived from high (time and space) resolution observation of precipitations are to make our cities more weather-ready. Finer resolution data available from X-band dual radar measurements enhance engineering tools as used for urban planning policies as well as protection (mitigation/adaptation) strategies to tackle climate-change related weather events. For decades engineering tools have been developed to work conveniently either with very local rain gauge networks, or with mainly C-band weather radars that have gradually been set up for space-time remote sensing of precipitation. Most of the time, the C-band weather radars continue to be calibrated by the existing rain gauge networks. Inhomogeneous distributions of rain gauging networks lead to only a partial information on the rainfall fields. In fact, the statistics of measured rainfall is strongly biased by the fractality of the measuring networks. This fractality needs to be properly taken in to account to retrieve the original properties of the rainfall fields, in spite of the radar data calibration. In this presentation, with the help of multifractal analysis, we first demonstrate that the semi-distributed hydrological models statistically reduce the rainfall fields into rainfall measured by a much scarcer network of virtual rain gauges. For this purpose, we use C-band and X-band radar data. The first has a resolution of 1 km in space and 5 min in time and is in fact a product provided by RHEA SAS after treating the Météo-France C-band radar data. The latter is measured by the radar operated at Ecole des Ponts and has a resolution of 250 m in space and 3.4 min in time. The obtained results suggest that a proper rainfall data re-normalisation is needed either when comparing gauged rainfall with the radar data, or when quantifying the impacts of space-time variability within hydrological modelling. Then, we used the semi-distributed hydrological model InfoWorks CS operated by Veolia over the Bièvre catchment (Paris region) with the same two types of rainfall data as inputs. We simulated six events and analysed the hydrographs resulted from simulations with both data types to show the impacts of initially different resolutions of rainfall fields over the same catchment, especially in respect to the small-scale variability not measured by the C-band radar data. These results encourage us not only to argue the use of higher resolution rainfall data, compare to that has been so claimed in the literature, but also to emphasise the important role of nonlinear geophysics' methods in taking reliable decisions.

Do we really use rainfall observations consistent with reality in hydrological modelling?

NASA Astrophysics Data System (ADS)

Ciampalini, Rossano; Follain, Stéphane; Raclot, Damien; Crabit, Armand; Pastor, Amandine; Moussa, Roger; Le Bissonnais, Yves

2017-04-01

Spatial and temporal patterns in rainfall control how water reaches soil surface and interacts with soil properties (i.e., soil wetting, infiltration, saturation). Once a hydrological event is defined by a rainfall with its spatiotemporal variability and by some environmental parameters such as soil properties (including land use, topographic and anthropic features), the evidence shows that each parameter variation produces different, specific outputs (e.g., runoff, flooding etc.). In this study, we focus on the effect of rainfall patterns because, due to the difficulty to dispose of detailed data, their influence in modelling is frequently underestimated or neglected. A rainfall event affects a catchment non uniformly, it is spatially localized and its pattern moves in space and time. The way and the time how the water reaches the soil and saturates it respect to the geometry of the catchment deeply influences soil saturation, runoff, and then sediment delivery. This research, approaching a hypothetical, simple case, aims to stimulate the debate on the reliability of the rainfall quality used in hydrological / soil erosion modelling. We test on a small catchment of the south of France (Roujan, Languedoc Roussillon) the influence of rainfall variability with the use of a HD hybrid hydrological - soil erosion model, combining a cinematic wave with the St. Venant equation and a simplified "bucket" conceptual model for ground water, able to quantify the effect of different spatiotemporal patterns of a very-high-definition synthetic rainfall. Results indicate that rainfall spatiotemporal patterns are crucial simulating an erosive event: differences between spatially uniform rainfalls, as frequently adopted in simulations, and some hypothetical rainfall patterns here applied, reveal that the outcome of a simulated event can be highly underestimated.

Year to year variation of rainfall rate and rainfall regime in Ota, southwest Nigeria for the year 2012 to 2015

NASA Astrophysics Data System (ADS)

Omotosho, T. V.; Ometan, O. O.; Akinwumi, S. A.; Adewusi, O. M.; Boyo, A. O.; Singh, M. S. J.

2017-05-01

The tropics is characterized to have convective type of rainfall which has high occurrence of rainfall compared to the temperate regions of the world. In this paper, the accumulation of rainfall in Ota, Southwest, Nigeria (6° 42 N, 3° 14 E) has been analysed to present the one-minute rainfall rate and the predominant type of rainfall. Four years’ data used for this study was taken using the Davis Wireless vantage Pro2 weather station at Covenant University, Ota, Ogun State. The data collected were used to analyse the one-minute rainfall rate and different types of rainfall predominant in this region. For the prediction and modelling of rain attenuation at microwave frequencies for a region like the Nigeria at various percentage of time, one-minute rainfall rate is required. Nigeria falls into the P zone of 114 mm/hr. as per International Telecommunication Union - Recommendation (ITU-R). The analysis carried out indicated that the measured yearly averaged maximum one-minute rainfall rate for 2012, 2013, 2014 and 2015 are 157.7 mm/h, 148.0 mm/h, 241.2 mm/h and 157.3 mm/h respectively. It also indicated that the drizzle type of rainfall is predominant in contrast to established fact that thunderstorm occurs more in the tropics.

Simulation of extreme rainfall event of November 2009 over Jeddah, Saudi Arabia: the explicit role of topography and surface heating

NASA Astrophysics Data System (ADS)

Almazroui, Mansour; Raju, P. V. S.; Yusef, A.; Hussein, M. A. A.; Omar, M.

2018-04-01

In this paper, a nonhydrostatic Weather Research and Forecasting (WRF) model has been used to simulate the extreme precipitation event of 25 November 2009, over Jeddah, Saudi Arabia. The model is integrated in three nested (27, 9, and 3 km) domains with the initial and boundary forcing derived from the NCEP reanalysis datasets. As a control experiment, the model integrated for 48 h initiated at 0000 UTC on 24 November 2009. The simulated rainfall in the control experiment depicts in well agreement with Tropical Rainfall Measurement Mission rainfall estimates in terms of intensity as well as spatio-temporal distribution. Results indicate that a strong low-level (850 hPa) wind over Jeddah and surrounding regions enhanced the moisture and temperature gradient and created a conditionally unstable atmosphere that favored the development of the mesoscale system. The influences of topography and heat exchange process in the atmosphere were investigated on the development of extreme precipitation event; two sensitivity experiments are carried out: one without topography and another without exchange of surface heating to the atmosphere. The results depict that both surface heating and topography played crucial role in determining the spatial distribution and intensity of the extreme rainfall over Jeddah. The topography favored enhanced uplift motion that further strengthened the low-level jet and hence the rainfall over Jeddah and adjacent areas. On the other hand, the absence of surface heating considerably reduced the simulated rainfall by 30% as compared to the observations.

Convection anomalies associated with warm eddy at the coastal area

NASA Astrophysics Data System (ADS)

Shi, R.; Wang, D.

2017-12-01

A possible correlation between a warm eddy and thunderstorms and convective precipitations are investigated at the coastal area in the northwestern South China Sea. Compared to the climatological mean in August from 2006 to 2013, an extreme enhancement of thunderstorm activities and precipitation rate are identified at the southern offshore area of Hainan island in August 2010 when a strong and long-live warm eddy was observed near the coastline at the same time. The 3 hourly satellite data (TRMM) indicate that the nocturnal convections is strong offshore and that could be responsible for the extreme positive anomalies of thunderstorms and rainfall in August 2010. The TRMM data also show a small reduction of thunderstorm activities and rainfall on the island in the afternoon. Meanwhile, the Weather Research and Forecasting (WRF) model was applied to simulate the change of rainfall in August 2010. The WRF simulation of rainfall rate is comparable with the observation results while there is some difference in the spatial distribution. The WRF simulation successfully captured the strong offshore rainfall and the diurnal variation of rainfall in August 2010. The WRF simulation indicated that the different convergence induced by sea/land breeze could be one essential reason for the adjustment of thunderstorms and rainfall in 2010. The substantial connection between sea/land breeze and upper layer heat content modified by the warm eddy is still on ongoing and will be reported in the future work.

Strategy for introduction of rainwater management facility considering rainfall event applied on new apartment complex

NASA Astrophysics Data System (ADS)

KIM, H.; Lee, D. K.; Yoo, S.

2014-12-01

As regional torrential rains become frequent due to climate change, urban flooding happens very often. That is why it is necessary to prepare for integrated measures against a wide range of rainfall. This study proposes introduction of effective rainwater management facilities to maximize the rainwater runoff reductions and recover natural water circulation for unpredictable extreme rainfall in apartment complex scale. The study site is new apartment complex in Hanam located in east of Seoul, Korea. It has an area of 7.28ha and is analysed using the EPA-SWMM and STORM model. First, it is analyzed that green infrastructure(GI) had efficiency of flood reduction at the various rainfall events and soil characteristics, and then the most effective value of variables are derived. In case of rainfall event, Last 10 years data of 15 minutes were used for analysis. A comparison between A(686mm rainfall during 22days) and B(661mm/4days) knew that soil infiltration of A is 17.08% and B is 5.48% of the rainfall. Reduction of runoff after introduction of the GI of A is 24.76% and B is 6.56%. These results mean that GI is effective to small rainfall intensity, and artificial rainwater retarding reservoir is needed at extreme rainfall. Second, set of target year is conducted for the recovery of hydrological cycle at the predevelopment. And an amount of infiltration, evaporation, surface runoff of the target year and now is analysed on the basis of land coverage, and an arrangement of LID facilities. Third, rainwater management scenarios are established and simulated by the SWMM-LID. Rainwater management facilities include GI(green roof, porous pavement, vegetative swale, ecological pond, and raingarden), and artificial rainwater. Design scenarios are categorized five type: 1)no GI, 2)conventional GI design(current design), 3)intensive GI design, 4)GI design+rainwater retarding reservoir 5)maximized rainwater retarding reservoir. Intensive GI design is to have attribute value to obtain the maximum efficiency for each GI facility with in-depth experts interviews. Climate change scenario is also used to set the capacity of the rainwater management facilities considering the extreme precipitation. These all scenarios are not only simulated for calculating the hydrological balance but analysed the cost for each scenarios effect.

Effect of fabric mounting method and backing material on bloodstain patterns of drip stains on textiles.

PubMed

Chang, J Y M; Michielsen, S

2016-05-01

Textiles may provide valuable bloodstain evidence to help piece together events or activities at violent crime scenes. However, in spite of over 75 years of research, there are still difficulties encountered in many cases in the interpretation and identification of bloodstains on textiles. In this study, we dripped porcine blood onto three types of fabric (plain woven, single jersey knit, and denim) that are supported in four different ways (hard, taut, loose, and semi-hard, i.e., fabric laid on denim). These four mounting methods represent different ways in which a textile may be present when blood from a violent act lands on it. This study investigates how the fabric mounting method and backing material affect the appearance of drip stains on textiles. We found that bloodstain patterns formed on fabric lying flat on a hard surface were very different from when the same fabric was suspended loosely. We also found that bloodstains formed on the technical back of single jersey knit were vastly different from those on the technical face. Interestingly, some drip stains showed blood passing through the textile and leaving a stain behind it that resembled insect stains. By observing, recording, and describing how a blood stained textile is found or presented at the scene, the analyst may be able to better understand bloodstains and bloodstain patterns on textiles, which could be useful to confirm or refute a witness's account of how blood came to be where it was found after a bloodshed event.

Causes and Model Skill of the Persistent Intense Rainfall and Flooding in Paraguay during the Austral Summer 2015-2016

NASA Astrophysics Data System (ADS)

Doss-Gollin, J.; Munoz, A. G.; Pastén, M.

2017-12-01

During the austral summer 2015-16 severe flooding displaced over 150,000 people on the Paraguay River system in Paraguay, Argentina, and Southern Brazil. This flooding was out of phase with the typical seasonal cycle of the Paraguay River, and was driven by repeated intense rainfall events in the Lower Paraguay River basin. Using a weather typing approach within a diagnostic framework, we show that enhanced moisture inflow from the low-level jet and local convergence associated with baroclinic systems favored the development of mesoscale convective activity and enhanced precipitation. The observed circulation patterns were made more likely by the cross-timescale interactions of multiple climate mechanisms including the strong, mature El Niño event and an active Madden-Julien Oscillation in phases four and five. We also perform a comparison of the rainfall predictability using seasonal forecasts from the Latin American Observatory of Climate Events (OLE2) and sub-seasonal forecasts produced by the ECMWF. We find that the model output precipitation field exhibited limited skill at lead times beyond the synoptic timescale, but that a Model Output Statistics (MOS) approach, in which the leading principal components of the observed rainfall field are regressed on the leading principal components of model-simulated rainfall fields, substantially improves spatial representation of rainfall forecasts. Possible implications for flood preparedness are briefly discussed.

Evaluation of Rainfall-Runoff Models for Mediterranean Subcatchments

NASA Astrophysics Data System (ADS)

Cilek, A.; Berberoglu, S.; Donmez, C.

2016-06-01

The development and the application of rainfall-runoff models have been a corner-stone of hydrological research for many decades. The amount of rainfall and its intensity and variability control the generation of runoff and the erosional processes operating at different scales. These interactions can be greatly variable in Mediterranean catchments with marked hydrological fluctuations. The aim of the study was to evaluate the performance of rainfall-runoff model, for rainfall-runoff simulation in a Mediterranean subcatchment. The Pan-European Soil Erosion Risk Assessment (PESERA), a simplified hydrological process-based approach, was used in this study to combine hydrological surface runoff factors. In total 128 input layers derived from data set includes; climate, topography, land use, crop type, planting date, and soil characteristics, are required to run the model. Initial ground cover was estimated from the Landsat ETM data provided by ESA. This hydrological model was evaluated in terms of their performance in Goksu River Watershed, Turkey. It is located at the Central Eastern Mediterranean Basin of Turkey. The area is approximately 2000 km2. The landscape is dominated by bare ground, agricultural and forests. The average annual rainfall is 636.4mm. This study has a significant importance to evaluate different model performances in a complex Mediterranean basin. The results provided comprehensive insight including advantages and limitations of modelling approaches in the Mediterranean environment.

Internally Generated and Externally Forced Multidecadal Oceanic Modes and their Influence on the Summer Rainfall over East Asia

NASA Astrophysics Data System (ADS)

Si, D.; Hu, A.

2017-12-01

The interdecadal oceanic variabilities can be generated from both internal and external processes, and these variabilities can significantly modulate our climate on global and regional scale, such as the warming slowdown in the early 21st century, and the rainfall in East Asia. By analyzing simulations from a unique Community Earth System Model (CESM) Large Ensemble (CESM_LE) project, we show that the Interdecadal Pacific Oscillation (IPO) is primarily an internally generated oceanic variability, while the Atlantic Multidecadal Oscillation (AMO) may be an oceanic variability generated by internal oceanic processes and modulated by external forcings in the 20th century. Although the observed relationship between IPO and the Yangtze-Huaihe River valley (YHRV) summer rainfall in China is well simulated in both the preindustrial control and 20th century ensemble, none of the 20th century ensemble members can reproduce the observed time evolution of both IPO and YHRV due to the unpredictable nature of IPO on multidecade timescale. On the other hand, although CESM_LE cannot reproduce the observed relationship between AMO and Huanghe River valley (HRV) summer rainfall of China in the preindustrial control simulation, this relationship in the 20th century simulations is well reproduced, and the chance to reproduce the observed time evolution of both AMO and HRV rainfall is about 30%, indicating the important role of the interaction between the internal processes and the external forcing to realistically simulate the AMO and HRV rainfall.

Forward modeling to investigate inversion artifacts resulting from time-lapse electrical resistivity tomography during rainfall simulations

NASA Astrophysics Data System (ADS)

Carey, Austin M.; Paige, Ginger B.; Carr, Bradley J.; Dogan, Mine

2017-10-01

Time-lapse electrical resistivity tomography (ERT) is commonly used as a minimally invasive tool to study infiltration processes. In 2014, we conducted field studies coupling variable intensity rainfall simulation with high-resolution ERT to study the real-time partitioning of rainfall into surface and subsurface response. The significant contrast in resistivity in the subsurface from large changes in subsurface moisture resulted in artifacts during the inversion process of the time-lapse ERT data collected using a dipole-dipole electrode array. These artifacts, which are not representative of real subsurface moisture dynamics, have been shown to arise during time-lapse inversion of ERT data and may be subject to misinterpretation. Forward modeling of the infiltration process post field experiments using a two-layer system (saprolite overlain by a soil layer) was used to generate synthetic datasets. The synthetic data were used to investigate the influence of both changes in volumetric moisture content and electrode configuration on the development of the artifacts identified in the field datasets. For the dipole-dipole array, we found that a decrease in the resistivity of the bottom layer by 67% resulted in a 50% reduction in artifact development. Artifacts for the seven additional array configurations tested, ranged from a 19% increase in artifact development (using an extended dipole-dipole array) to as much as a 96% decrease in artifact development (using a wenner-alpha array), compared to that of the dipole-dipole array. Moreover, these arrays varied in their ability to accurately delineate the infiltration front. Model results showed that the modified pole-dipole array was able to accurately image the infiltration zone and presented fewer artifacts for our experiments. In this study, we identify an optimal array type for imaging rainfall-infiltration dynamics that reduces artifacts. The influence of moisture contrast between the infiltrating water and the bulk subsurface material was characterized and shown to be a major factor in contributing to artifact development. Through forward modeling, this study highlights the importance of considering array type and subsurface moisture conditions when using time-lapse resistivity to obtain reliable estimates of vadose zone flow processes during rainfall-infiltration events.

A sensitivity study of the coupled simulation of the Northeast Brazil rainfall variability

NASA Astrophysics Data System (ADS)

Misra, Vasubandhu

2007-06-01

Two long-term coupled ocean-land-atmosphere simulations with slightly different parameterization of the diagnostic shallow inversion clouds in the atmospheric general circulation model (AGCM) of the Center for Ocean-Land-Atmosphere Studies (COLA) coupled climate model are compared for their annual cycle and interannual variability of the northeast Brazil (NEB) rainfall variability. It is seen that the solar insolation affected by the changes to the shallow inversion clouds results in large scale changes to the gradients of the SST and the surface pressure. The latter in turn modulates the surface convergence and the associated Atlantic ITCZ precipitation and the NEB annual rainfall variability. In contrast, the differences in the NEB interannual rainfall variability between the two coupled simulations is attributed to their different remote ENSO forcing.

Tests of an experimental slash ignition unit

Treesearch

James L. Murphy; Harry E. Schimke

1965-01-01

A prototype ignition package containing an incendiary powder and designed for slash and brush burning jobs showed some promise, but the unit tested was not superior to such conventional devices as fusees, diesel backpack type flamethrowers, Very pistols, and drip torches.

The Impact of Aerosols on Cloud and Precipitation Processes: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Li, X.; Khain, A.; Simpson, S.

2005-01-01

Cloud microphysics are inevitable affected by the smoke particle (CCN, cloud condensation nuclei) size distributions below the clouds, Therefore, size distributions parameterized as spectral bin microphysics are needed to explicitly study the effect of atmospheric aerosol concentration on cloud development, rainfall production, and rainfall rates for convective clouds. Recently, a detailed spectral-bin microphysical scheme was implemented into the the Goddard Cumulus Ensemble (GCE) model. The formulation for the explicit spectral-bim microphysical processes is based on solving stochastic kinetic equations for the size distribution functions of water droplets (i.e., cloud droplets and raindrops), and several types of ice particles [i.e., pristine ice crystals (columnar and plate-like), snow (dendrites and aggregates), graupel and frozen drops/hail]. Each type is described by a special size distribution function containing many categories (i.e., 33 bins). Atmospheric aerosols are also described using number density size-distribution functions.

Accessing the capability of TRMM 3B42 V7 to simulate streamflow during extreme rain events: Case study for a Himalayan River Basin

NASA Astrophysics Data System (ADS)

Kumar, Brijesh; Lakshmi, Venkat

2018-03-01

The paper examines the quality of Tropical Rainfall Monitoring Mission (TRMM) 3B42 V7 precipitation product to simulate the streamflow using Soil Water Assessment Tool (SWAT) model for various rainfall intensities over the Himalayan region. The SWAT model has been set up for Gandak River Basin with 41 sub-basins and 420 HRUs. Five stream gauge locations are used to simulate the streamflow for a time span of 10 years (2000-2010). Daily streamflow for the simulation period is collected from Central Water Commission (CWC), India and Department of Hydrology and Meteorology (DHM), Nepal. The simulation results are found good in terms of Nash-Sutcliffe efficiency (NSE) {>}0.65, coefficient of determination (R2) {>}0.67 and Percentage Bias (PBIAS){<}15%, at each stream gauge sites. Thereafter, we have calculated the PBIAS and RMSE-observations standard deviation ratio (RSR) statistics between TRMM simulated and observed streamflow for various rainfall intensity classes, viz., light ({<}7.5 mm/d), moderate (7.5 to 35.4 mm/d), heavy (35.5 to 124.4 mm/d) and extremely heavy ({>}124.4 mm/d). The PBIAS and RSR show that TRMM simulated streamflow is suitable for moderate to heavy rainfall intensities. However, it does not perform well for light- and extremely-heavy rainfall intensities. The finding of the present work is useful for the problems related to water resources management, irrigation planning and hazard analysis over the Himalayan regions.

Statistical evaluation of rainfall-simulator and erosion testing procedure : final report.

DOT National Transportation Integrated Search

1977-01-01

The specific aims of this study were (1) to supply documentation of statistical repeatability and precision of the rainfall-simulator and to document the statistical repeatabiity of the soil-loss data when using the previously recommended tentative l...

A laboratory evaluation of the influence of weighing gauges performance on extreme events statistics

NASA Astrophysics Data System (ADS)

Colli, Matteo; Lanza, Luca

2014-05-01

The effects of inaccurate ground based rainfall measurements on the information derived from rain records is yet not much documented in the literature. La Barbera et al. (2002) investigated the propagation of the systematic mechanic errors of tipping bucket type rain gauges (TBR) into the most common statistics of rainfall extremes, e.g. in the assessment of the return period T (or the related non-exceedance probability) of short-duration/high intensity events. Colli et al. (2012) and Lanza et al. (2012) extended the analysis to a 22-years long precipitation data set obtained from a virtual weighing type gauge (WG). The artificial WG time series was obtained basing on real precipitation data measured at the meteo-station of the University of Genova and modelling the weighing gauge output as a linear dynamic system. This approximation was previously validated with dedicated laboratory experiments and is based on the evidence that the accuracy of WG measurements under real world/time varying rainfall conditions is mainly affected by the dynamic response of the gauge (as revealed during the last WMO Field Intercomparison of Rainfall Intensity Gauges). The investigation is now completed by analyzing actual measurements performed by two common weighing gauges, the OTT Pluvio2 load-cell gauge and the GEONOR T-200 vibrating-wire gauge, since both these instruments demonstrated very good performance under previous constant flow rate calibration efforts. A laboratory dynamic rainfall generation system has been arranged and validated in order to simulate a number of precipitation events with variable reference intensities. Such artificial events were generated basing on real world rainfall intensity (RI) records obtained from the meteo-station of the University of Genova so that the statistical structure of the time series is preserved. The influence of the WG RI measurements accuracy on the associated extreme events statistics is analyzed by comparing the original intensity-duration-frequency (IDF) curves with those obtained from the measuring of the simulated rain events. References: Colli, M., L.G. Lanza, and P. La Barbera, (2012). Weighing gauges measurement errors and the design rainfall for urban scale applications, 9th International Workshop On Precipitation In Urban Areas, 6-9 December, 2012, St. Moritz, Switzerland Lanza, L.G., M. Colli, and P. La Barbera (2012). On the influence of rain gauge performance on extreme events statistics: the case of weighing gauges, EGU General Assembly 2012, April 22th, Wien, Austria La Barbera, P., L.G. Lanza, and L. Stagi, (2002). Influence of systematic mechanical errors of tipping-bucket rain gauges on the statistics of rainfall extremes. Water Sci. Techn., 45(2), 1-9.

A simple lightning assimilation technique for improving ...

EPA Pesticide Factsheets

Convective rainfall is often a large source of error in retrospective modeling applications. In particular, positive rainfall biases commonly exist during summer months due to overactive convective parameterizations. In this study, lightning assimilation was applied in the Kain-Fritsch (KF) convective scheme to improve retrospective simulations using the Weather Research and Forecasting (WRF) model. The assimilation method has a straightforward approach: force KF deep convection where lightning is observed and, optionally, suppress deep convection where lightning is absent. WRF simulations were made with and without lightning assimilation over the continental United States for July 2012, July 2013, and January 2013. The simulations were evaluated against NCEP stage-IV precipitation data and MADIS near-surface meteorological observations. In general, the use of lightning assimilation considerably improves the simulation of summertime rainfall. For example, the July 2012 monthly averaged bias of 6 h accumulated rainfall is reduced from 0.54 to 0.07 mm and the spatial correlation is increased from 0.21 to 0.43 when lightning assimilation is used. Statistical measures of near-surface meteorological variables also are improved. Consistent improvements also are seen for the July 2013 case. These results suggest that this lightning assimilation technique has the potential to substantially improve simulation of warm-season rainfall in retrospective WRF applications. The

A Simple Lightning Assimilation Technique For Improving ...

EPA Pesticide Factsheets

Convective rainfall is often a large source of error in retrospective modeling applications. In particular, positive rainfall biases commonly exist during summer months due to overactive convective parameterizations. In this study, lightning assimilation was applied in the Kain-Fritsch (KF) convective scheme to improve retrospective simulations using the Weather Research and Forecasting (WRF) model. The assimilation method has a straightforward approach: Force KF deep convection where lightning is observed and, optionally, suppress deep convection where lightning is absent. WRF simulations were made with and without lightning assimilation over the continental United States for July 2012, July 2013, and January 2013. The simulations were evaluated against NCEP stage-IV precipitation data and MADIS near-surface meteorological observations. In general, the use of lightning assimilation considerably improves the simulation of summertime rainfall. For example, the July 2012 monthly-averaged bias of 6-h accumulated rainfall is reduced from 0.54 mm to 0.07 mm and the spatial correlation is increased from 0.21 to 0.43 when lightning assimilation is used. Statistical measures of near-surface meteorological variables also are improved. Consistent improvements also are seen for the July 2013 case. These results suggest that this lightning assimilation technique has the potential to substantially improve simulation of warm-season rainfall in retrospective WRF appli

Remote-Sensing-Based Evaluation of Relative Consumptive Use Between Flood- and Drip-Irrigated Fields

NASA Astrophysics Data System (ADS)

Martinez Baquero, G. F.; Jordan, D. L.; Whittaker, A. T.; Allen, R. G.

2013-12-01

Governments and water authorities are compelled to evaluate the impacts of agricultural irrigation on economic development and sustainability as water supply shortages continue to increase in many communities. One of the strategies commonly used to reduce such impacts is the conversion of traditional irrigation methods towards more water-efficient practices. As part of a larger effort by the New Mexico Interstate Stream Commission to understand the environmental and economic impact of converting from flood irrigation to drip irrigation, this study evaluates the water-saving effectiveness of drip irrigation in Deming, New Mexico, using a remote-sensing-based technique combined with ground data collection. The remote-sensing-based technique used relative temperature differences as a proxy for water use to show relative differences in crop consumptive use between flood- and drip-irrigated fields. Temperature analysis showed that, on average, drip-irrigated fields were cooler than flood-irrigated fields, indicating higher water use. The higher consumption of water by drip-irrigated fields was supported by a determination of evapotranspiration (ET) from all fields using the METRIC Landsat-based surface energy balance model. METRIC analysis yielded higher instantaneous ET for drip-irrigated fields when compared to flood-irrigated fields and confirmed that drip-irrigated fields consumed more water than flood-irrigated fields planted with the same crop. More water use generally results in more biomass and hence higher crop yield, and this too was confirmed by greater relative Normalized Difference Vegetation Index for the drip irrigated fields. Results from this study confirm previous estimates regarding the impacts of increased efficiency of drip irrigation on higher water consumption in the area (Ward and Pulido-Velazquez, 2008). The higher water consumption occurs with drip because, with the limited water supplies and regulated maximum limits on pumping amounts, the higher efficiency of drip enables producers to convert larger percentages of pumped ground-water into evapotranspiration and reduces the ';return' of percolation ';losses' back to the ground-water system that previously re-recharged the aquifer. This study illustrates the usefulness of remote sensing techniques to evaluate spatial patterns of ET by different irrigation methods. These results illustrate a first-step quantitative tool that can be used by water resources managers in formulation of policy to limit net water consumption and maintain reliable water supply sources.

Comparing a simple methodology to evaluate hydrodynamic parameters with rainfall simulation experiments

NASA Astrophysics Data System (ADS)

Di Prima, Simone; Bagarello, Vincenzo; Bautista, Inmaculada; Burguet, Maria; Cerdà, Artemi; Iovino, Massimo; Prosdocimi, Massimo

2016-04-01

Studying soil hydraulic properties is necessary for interpreting and simulating many hydrological processes having environmental and economic importance, such as rainfall partition into infiltration and runoff. The saturated hydraulic conductivity, Ks, exerts a dominating influence on the partitioning of rainfall in vertical and lateral flow paths. Therefore, estimates of Ks are essential for describing and modeling hydrological processes (Zimmermann et al., 2013). According to several investigations, Ks data collected by ponded infiltration tests could be expected to be unusable for interpreting field hydrological processes, and particularly infiltration. In fact, infiltration measured by ponding give us information about the soil maximum or potential infiltration rate (Cerdà, 1996). Moreover, especially for the hydrodynamic parameters, many replicated measurements have to be carried out to characterize an area of interest since they are known to vary widely both in space and time (Logsdon and Jaynes, 1996; Prieksat et al., 1994). Therefore, the technique to be applied at the near point scale should be simple and rapid. Bagarello et al. (2014) and Alagna et al. (2015) suggested that the Ks values determined by an infiltration experiment carried applying water at a relatively large distance from the soil surface could be more appropriate than those obtained with a low height of water pouring to explain surface runoff generation phenomena during intense rainfall events. These authors used the Beerkan Estimation of Soil Transfer parameters (BEST) procedure for complete soil hydraulic characterization (Lassabatère et al., 2006) to analyze the field infiltration experiment. This methodology, combining low and high height of water pouring, seems appropriate to test the effect of intense and prolonged rainfall events on the hydraulic characteristics of the surface soil layer. In fact, an intense and prolonged rainfall event has a perturbing effect on the soil surface and, reasonably, it can better be represented by the high runs than the low runs (Alagna et al., 2015). Obviously, this methodology is also simpler than an approach involving soil characterization both before and after natural or simulated rainfall since it needs less equipment and field work. On the other hand, rainfall simulation experiments are more realistic and accurate, but also more sophisticated and costly (Cerdà, 1997). Rainfall simulation is often used to measure the infiltration process (e.g., Bhardwaj and Singh, 1992; Cerdà, 1999, 1997, 1996; Cerdà and Doerr, 2007; Iserloh et al., 2013; Liu et al., 2011; Tricker, 1979), and it has become an important method for assessing the subjects of soil erosion and soil hydrological processes (Iserloh et al., 2013). Its application allows a quick, specific and reproducible assessment of the meaning and impact of several factors, such as slope, soil type (infiltration, permeability), soil moisture, splash effect of raindrops (aggregate stability), surface structure, vegetation cover and vegetation structure (Bowyer-Bower and Burt, 1989). The objectives of this investigation are: (i) to compare infiltration rates measured by applying water at a relatively large distance from the soil surface with those obtained by rainfall simulation experiments and (ii) to verify if the Ks values determined with the BEST procedure are in line with the occurrence of runoff measured with a more robust methodology. Acknowledgements The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 603498 (RECARE project). References Alagna, V., Bagarello, V., Di Prima, S., Giordano, G., Iovino, M., 2015. Testing infiltration run effects on the estimated hydrodynamic parameters of a sandy-loam soil. Submitted to Geoderma. Bagarello, V., Castellini, M., Di Prima, S., Iovino, M., 2014. Soil hydraulic properties determined by infiltration experiments and different heights of water pouring. Geoderma 213, 492-501. doi:10.1016/j.geoderma.2013.08.032 Bhardwaj, A., Singh, R., 1992. Development of a portable rainfall simulator infiltrometer for infiltration, runoff and erosion studies. Agricultural Water Management 22, 235-248. doi:10.1016/0378-3774(92)90028-U Bouwer, H., 1966. Rapid field measurement of air entry value and hydraulic conductivity of soil as significant parameters in flow system analysis. Water Resour. Res. 2, 729-738. doi:10.1029/WR002i004p00729 Bowyer-Bower, T.A.S., Burt, T.P., 1989. Rainfall simulators for investigating soil response to rainfall. Soil Technology 2, 1-16. doi:10.1016/S0933-3630(89)80002-9 Cerdà, A., 1999. Simuladores de lluvia y su aplicación a la Geomorfologia: estado de la cuestión. Cuadernos de investigación geográfica 45-84. Cerdà, A., 1997. Seasonal changes of the infiltration rates in a Mediterranean scrubland on limestone. Journal of Hydrology 198, 209-225. doi:10.1016/S0022-1694(96)03295-7 Cerdà, A., 1996. Seasonal variability of infiltration rates under contrasting slope conditions in southeast Spain. Geoderma 69, 217-232. doi:10.1016/0016-7061(95)00062-3 Cerdà, A., Doerr, S.H., 2007. Soil wettability, runoff and erodibility of major dry-Mediterranean land use types on calcareous soils. Hydrol. Process. 21, 2325-2336. doi:10.1002/hyp.6755 Iserloh, T., Ries, J.B., Arnáez, J., Boix-Fayos, C., Butzen, V., Cerdà, A., Echeverría, M.T., Fernández-Gálvez, J., Fister, W., Geißler, C., Gómez, J.A., Gómez-Macpherson, H., Kuhn, N.J., Lázaro, R., León, F.J., Martínez-Mena, M., Martínez-Murillo, J.F., Marzen, M., Mingorance, M.D., Ortigosa, L., Peters, P., Regüés, D., Ruiz-Sinoga, J.D., Scholten, T., Seeger, M., Solé-Benet, A., Wengel, R., Wirtz, S., 2013. European small portable rainfall simulators: A comparison of rainfall characteristics. CATENA 110, 100-112. doi:10.1016/j.catena.2013.05.013 Lassabatère, L., Angulo-Jaramillo, R., Soria Ugalde, J.M., Cuenca, R., Braud, I., Haverkamp, R., 2006. Beerkan Estimation of Soil Transfer Parameters through Infiltration Experiments - BEST. Soil Science Society of America Journal 70, 521. doi:10.2136/sssaj2005.0026 Liu, H., Lei, T.W., Zhao, J., Yuan, C.P., Fan, Y.T., Qu, L.Q., 2011. Effects of rainfall intensity and antecedent soil water content on soil infiltrability under rainfall conditions using the run off-on-out method. Journal of Hydrology 396, 24-32. doi:10.1016/j.jhydrol.2010.10.028 Logsdon, S.D., Jaynes, D.B., 1996. Spatial Variability of Hydraulic Conductivity in a Cultivated Field at Different Times. Soil Science Society of America Journal 60, 703. doi:10.2136/sssaj1996.03615995006000030003x Prieksat, M.A., Kaspar, T.C., Ankeny, M.D., 1994. Positional and Temporal Changes in Ponded Infiltration in a Corn Field. Soil Science Society of America Journal 58, 181. doi:10.2136/sssaj1994.03615995005800010026x Tricker, A.S., 1979. The design of a portable rainfall simulator infiltrometer. Journal of Hydrology 41, 143-147. doi:10.1016/0022-1694(79)90111-2 van De Giesen, N.C., Stomph, T.J., de Ridder, N., 2000. Scale effects of Hortonian overland flow and rainfall-runoff dynamics in a West African catena landscape. Hydrol. Process. 14, 165-175. doi:10.1002/(SICI)1099-1085(200001)14:1<165::AID-HYP920>3.0.CO;2-1 Zimmermann, A., Schinn, D.S., Francke, T., Elsenbeer, H., Zimmermann, B., 2013. Uncovering patterns of near-surface saturated hydraulic conductivity in an overland flow-controlled landscape. Geoderma 195-196, 1-11. doi:10.1016/j.geoderma.2012.11.002

Regional rainfall-runoff relations for simulation of streamflow for watersheds in Du Page County, Illinois

USGS Publications Warehouse

Duncker, James J.; Melching, Charles S.

1998-01-01

Rainfall and streamflow data collected from July 1986 through September 1993 were utilized to calibrate and verify a continuous-simulation rainfall-runoff model for three watersheds (11.8--18.0 square miles in area) in Du Page County. Classification of land cover into three categories of pervious (grassland, forest/wetland, and agricultural land) and one category of impervious subareas was sufficient to accurately simulate the rainfall-runoff relations for the three watersheds. Regional parameter sets were obtained by calibrating jointly all parameters except fraction of ground-water inflow that goes to inactive ground water (DEEPFR), interflow recession constant (IRC), and infiltration (INFILT) for runoff from all three watersheds. DEEPFR and IRC varied among the watersheds because of physical differences among the watersheds. Two values of INFILT were obtained: one representing the rainfall-runoff process on the silty and clayey soils on the uplands and lake plains that characterize Sawmill Creek, St. Joseph Creek, and eastern Du Page County; and one representing the rainfall-runoff process on the silty soils on uplands that characterize Kress Creek and parts of western Du Page County. Regional rainfall-runoff relations, defined through joint calibration of the rainfall-runoff model and verified for independent periods, presented in this report, allow estimation of runoff for watersheds in Du Page County with an error in the total water balance less than 4.0 percent; an average absolute error in the annual-flow estimates of 17.1 percent with the error rarely exceeding 25 percent for annual flows; and correlation coefficients and coefficients of model-fit efficiency for monthly flows of at least 87 and 76 percent, respectively. Close reproduction of the runoff-volume duration curves was obtained. A frequency analysis of storm-runoff volume indicates a tendency of the model to undersimulate large storms, which may result from underestimation of the amount of impervious land cover in the watershed and errors in measuring rainfall for convective storms. Overall, the results of regional calibration and verification of the rainfall-runoff model indicate the simulated rainfall-runoff relations are adequate for stormwater-management planning and design for watersheds in Du Page County.

Modeling Rainfall-Runoff Dynamics in Tropical, Urban Socio-Hydrological Systems: Green Infrastructure and Variable Precipitation Interception

NASA Astrophysics Data System (ADS)

Nytch, C. J.; Meléndez-Ackerman, E. J.

2014-12-01

There is a pressing need to generate spatially-explicit models of rainfall-runoff dynamics in the urban humid tropics that can characterize flow pathways and flood magnitudes in response to erratic precipitation events. To effectively simulate stormwater runoff processes at multiple scales, complex spatio-temporal parameters such as rainfall, evapotranspiration, and antecedent soil moisture conditions must be accurately represented, in addition to uniquely urban factors including stormwater conveyance structures and connectivity between green and gray infrastructure elements. In heavily urbanized San Juan, Puerto Rico, stream flashiness and frequent flooding are major issues, yet still lacking is a hydrological analysis that models the generation and movement of fluvial and pluvial stormwater through the watershed. Our research employs a novel and multifaceted approach to dealing with this problem that integrates 1) field-based rainfall interception and infiltration methodologies to quantify the hydrologic functions of natural and built infrastructure in San Juan; 2) remote sensing analysis to produce a fine-scale typology of green and gray cover types in the city and determine patterns of spatial distribution and connectivity; 3) assessment of precipitation and streamflow variability at local and basin-wide scales using satellite and radar precipitation estimates in concert with rainfall and stream gauge point data and participatory flood mapping; 4) simulation of historical, present-day, and future stormwater runoff scenarios with a fully distributed hydrologic model that couples diverse components of urban socio-hydrological systems from formal and informal knowledge sources; and 5) bias and uncertainty analysis of parameters and model structure within a Bayesian hierarchical framework. Preliminary results from the rainfall interception study suggest that canopy structure and leaf area index of different tree species contribute to variable throughfall and stemflow responses. Additional investigations are pending. The findings from this work will help inform urban planning and design, and build adaptive capacity to reduce flood vulnerability in the context of a changing climate.

Simulation of Urban Rainfall-Runoff in Piedmont Cities: A Case Study in Jinan City, China

NASA Astrophysics Data System (ADS)

Chang, X.; Xu, Z.; Zhao, G.; Li, H.

2017-12-01

During the past decades, frequent flooding disasters in urban areas resulted in catastrophic impacts such as human life casualties and property damages especially in piedmont cities due to its specific topography. In this study, a piedmont urban flooding model was developed in the Huangtaiqiao catchment based on SWMM. The sub-catchments in this piedmont area were divided into mountainous area, plain area and main urban area according to the variations of underlying surface topography. The impact of different routing mode and channel roughness on simulation results was quantitatively analyzed under different types of scenarios, and genetic algorithm was used to optimize model parameters. Results show that the simulation is poor (with a mean Nash coefficient of 0.61) when using the traditional routing mode in SWMM model, which usually ignores terrain variance in piedmont area. However, when the difference of routing mode, percent routed and channel roughness are considered, the prediction precision of model were significantly increased (with a mean Nash coefficient of 0.86), indicating that the difference of surface topography significantly affects the simulation results in piedmont cities. The relevant results would provide the scientific basis and technical support for rainfall-runoff simulation, flood control and disaster alleviation in piedmont cities.

Downscaling of Global Climate Change Estimates to Regional Scales: An Application to Iberian Rainfall in Wintertime.

NASA Astrophysics Data System (ADS)

von Storch, Hans; Zorita, Eduardo; Cubasch, Ulrich

1993-06-01

A statistical strategy to deduct regional-scale features from climate general circulation model (GCM) simulations has been designed and tested. The main idea is to interrelate the characteristic patterns of observed simultaneous variations of regional climate parameters and of large-scale atmospheric flow using the canonical correlation technique.The large-scale North Atlantic sea level pressure (SLP) is related to the regional, variable, winter (DJF) mean Iberian Peninsula rainfall. The skill of the resulting statistical model is shown by reproducing, to a good approximation, the winter mean Iberian rainfall from 1900 to present from the observed North Atlantic mean SLP distributions. It is shown that this observed relationship between these two variables is not well reproduced in the output of a general circulation model (GCM).The implications for Iberian rainfall changes as the response to increasing atmospheric greenhouse-gas concentrations simulated by two GCM experiments are examined with the proposed statistical model. In an instantaneous `2 C02' doubling experiment, using the simulated change of the mean North Atlantic SLP field to predict Iberian rainfall yields, there is an insignificant increase of area-averaged rainfall of 1 mm/month, with maximum values of 4 mm/month in the northwest of the peninsula. In contrast, for the four GCM grid points representing the Iberian Peninsula, the change is 10 mm/month, with a minimum of 19 mm/month in the southwest. In the second experiment, with the IPCC scenario A ("business as usual") increase Of C02, the statistical-model results partially differ from the directly simulated rainfall changes: in the experimental range of 100 years, the area-averaged rainfall decreases by 7 mm/month (statistical model), and by 9 mm/month (GCM); at the same time the amplitude of the interdecadal variability is quite different.

HD Hydrological modelling at catchment scale using rainfall radar observations

NASA Astrophysics Data System (ADS)

Ciampalini Rossano. Ciampalini@Gmail. Com), Rossano; Follain, Stéphane; Raclot, Damien; Crabit, Armand; Pastor, Amandine; Augas, Julien; Moussa, Roger; Colin, François; Le Bissonnais, Yves

2017-04-01

Hydrological simulations at catchment scale repose on the quality and data availability both for soil and rainfall data. Soil data are quite easy to be collected, although their quality depends on the resources devoted to this task, rainfall data observations, instead, need further effort because of their spatiotemporal variability. Rainfalls are normally recorded with rain gauges located in the catchment, they can provide detailed temporal data, but, the representativeness is limited to the point where the data are collected. Combining different gauges in space can provide a better representation of the rainfall event but the spatialization is often the main obstacle to obtain data close to the reality. Since several years, radar observations overcome this gap providing continuous data registration, that, when properly calibrated, can offer an adequate, continuous, cover in space and time for medium-wide catchments. Here, we use radar records for the south of the France on the La Peyne catchment with the protocol there adopted by the national meteo agency, with resolution of 1 km space and 5' time scale observations. We present here the realisation of a model able to perform from rainfall radar observations, continuous hydrological and soil erosion simulations. The model is semi-theoretically based, once it simulates water fluxes (infiltration-excess overland flow, saturation overland flow, infiltration and channel routing) with a cinematic wave using the St. Venant equation on a simplified "bucket" conceptual model for ground water, and, an empirical representation of sediment load as adopted in models such as STREAM-LANDSOIL (Cerdan et al., 2002, Ciampalini et al., 2012). The advantage of this approach is to furnish a dynamic representation - simulation of the rainfall-runoff events more easily than using spatialized rainfalls from meteo stations and to offer a new look on the spatial component of the events.

Simulation of the Onset of the Southeast Asian Monsoon During 1997 and 1998: The Impact of Surface Processes

NASA Technical Reports Server (NTRS)

Tao, W.-K.; Lau, W.; Baker, R.

2004-01-01

The onset of the southeast Asian monsoon during 1997 and 1998 was simulated with a coupled mesoscale atmospheric model (MM5) and a detailed land surface model. The rainfall results from the simulations were compared with observed satellite data from the TRMM (Tropical Rainfall Measuring Mission) TMI (TRMM Microwave Imager) and GPCP (Global Precipitation Climatology Project). The simulation with the land surface model captured basic signatures of the monsoon onset processes and associated rainfall statistics. The sensitivity tests indicated that land surface processes had a greater impact on the simulated rainfall results than that of a small sea surface temperature change during the onset period. In both the 1997 and 1998 cases, the simulations were significantly improved by including the land surface processes. The results indicated that land surface processes played an important role in modifying the low-level wind field over two major branches of the circulation; the southwest low-level flow over the Indo-China peninsula and the northern cold front intrusion from southern China. The surface sensible and latent heat exchange between the land and atmosphere modified the low-level temperature distribution and gradient, and therefore the low-level. The more realistic forcing of the sensible and latent heat from the detailed land surface model improved the monsoon rainfall and associated wind simulation. The model results will be compared to the simulation of the 6-7 May 2000 Missouri flash flood event. In addition, the impact of model initialization and land surface treatment on timing, intensity, and location of extreme precipitation will be examined.

Simulation of the Onset of the Southeast Asian Monsoon during 1997 and 1998: The Impact of Surface Processes

NASA Technical Reports Server (NTRS)

Tao, W.-K.; Wang, Y.; Lau, W.; Baker, R. D.

2004-01-01

The onset of the southeast Asian monsoon during 1997 and 1998 was simulated with a coupled mesoscale atmospheric model (MM5) and a detailed land surface model. The rainfall results from the simulations were compared with observed satellite data from the TRMM (Tropical Rainfall Measuring Mission) TMI (TRMM Microwave Imager) and GPCP (Global Precipitation Climatology Project). The simulation with the land surface model captured basic signatures of the monsoon onset processes and associated rainfall statistics. The sensitivity tests indicated that land surface processes had a greater impact on the simulated rainfall results than that of a small sea surface temperature change during the onset period. In both the 1997 and 1998 cases, the simulations were significantly improved by including the land surface processes. The results indicated that land surface processes played an important role in modifying the low-level wind field over two major branches of the circulation; the southwest low-level flow over the Indo-China peninsula and the northern cold front intrusion from southern China. The surface sensible and latent heat exchange between the land and atmosphere modified the low-level temperature distribution and gradient, and therefore the low-level. The more realistic forcing of the sensible and latent heat from the detailed land surface model improved the monsoon rainfall and associated wind simulation. The model results will be compared to the simulation of the 6-7 May 2000 Missouri flash flood event. In addition, the impact of model initialization and land surface treatment on timing, intensity, and location of extreme precipitation will be examined.

Influence of urban surface properties and rainfall characteristics on surface water flood outputs - insights from a physical modelling environment

NASA Astrophysics Data System (ADS)

Green, Daniel; Pattison, Ian; Yu, Dapeng

2017-04-01

Surface water (pluvial) flooding occurs when excess rainfall from intense precipitation events is unable to infiltrate into the subsurface or drain via natural or artificial drainage channels. Surface water flood events pose a major hazard to urban regions across the world, with nearly two thirds of flood damages in the UK being caused by surface water flood events. The perceived risk of surface water flooding appears to have increased in recent years due to several factors, including (i) precipitation increases associated with climatic change and variability; (ii) population growth meaning more people are occupying flood risk areas, and; (iii) land-use changes. Because urban areas are often associated with a high proportion of impermeable land-uses (e.g. tarmacked or paved surfaces and buildings) and a reduced coverage of vegetated, permeable surfaces, urban surface water flood risk during high intensity precipitation events is often exacerbated. To investigate the influence of urbanisation and terrestrial factors on surface water flood outputs, rainfall intensity, catchment slope, permeability, building density/layout scenarios were designed within a novel, 9m2 physical modelling environment. The two-tiered physical model used consists of (i) a low-cost, nozzle-type rainfall simulator component which is able to simulate consistent, uniformly distributed rainfall events of varying duration and intensity, and; (ii) a reconfigurable, modular plot surface. All experiments within the physical modelling environment were subjected to a spatiotemporally uniform 45-minute simulated rainfall event, while terrestrial factors on the physical model plot surface were altered systematically to investigate their hydrological response on modelled outflow and depth profiles. Results from the closed, controlled physical modelling experiments suggest that meteorological factors, such as the duration and intensity of simulated rainfall, and terrestrial factors, such as model slope, surface permeability and building density have a significant influence on physical model hydrological outputs. For example, changes in building density across the urban model catchment are shown to result in hydrographs having (i) a more rapid rising limb; (ii) higher peak discharges; (iii) a reduction in the total hydrograph time, and; (iv) a faster falling limb, with the dense building scenario having a 22% increase in peak discharge when compared to the no building scenario. Furthermore, the layout of buildings across the plot surface and their proximity to the outflow unit (i.e. downstream, upstream or to the side of the physical model outlet) is shown to influence outflow hydrograph response, with downstream concentrated building scenarios resulting in a delay in hydrograph onset time and a reduction in the time of the total outflow hydrograph event.

Vertical Motion Changes Related to North-East Brazil Rainfall Variability: a GCM Simulation

NASA Astrophysics Data System (ADS)

Roucou, Pascal; Oribe Rocha de Aragão, José; Harzallah, Ali; Fontaine, Bernard; Janicot, Serge

1996-08-01

The atmospheric structure over north-east Brazil during anomalous rainfall years is studied in the 11 levels of the outputs of the Laboratoire de Météorologie Dynamique atmospheric general circulation model (LMD AGCM). Seven 19-year simulations were performed using observed sea-surface temperature (SST) corresponding to the period 1970- 1988. The ensemble mean is calculated for each month of the period, leading to an ensemble-averaged simulation. The simulated March-April rainfall is in good agreement with observations. Correlations of simulated rainfall and three SST indices relative to the equatorial Pacific and northern and southern parts of the Atlantic Ocean exhibit stronger relationships in the simulation than in the observations. This is particularly true with the SST gradient in the Atlantic (Atlantic dipole). Analyses on 200 ;hPa velocity potential, vertical velocity, and vertical integral of the zonal component of mass flux are performed for years of abnormal rainfall and positive/negative SST anomalies in the Pacific and Atlantic oceans in March-April during the rainy season over the Nordeste region. The results at 200 hPa show a convergence anomaly over Nordeste and a divergence anomaly over the Pacific concomitant with dry seasons associated with warm SST anomalies in the Pacific and warm (cold) waters in the North (South) Atlantic. During drought years convection inside the ITCZ indicated by the vertical velocity exhibits a displacement of the convection zone corresponding to a northward migration of the ITCZ. The east-west circulation depicted by the zonal divergent mass flux shows subsiding motion over Nordeste and ascending motion over the Pacific in drought years, accompanied by warm waters in the eastern Pacific and warm/cold waters in northern/southern Atlantic. Rainfall variability of the Nordeste rainfall is linked mainly to vertical motion and SST variability through the migration of the ITCZ and the east-west circulation.

Characteristics of Heavy Summer Rainfall in Southwestern Taiwan in Relation to Orographic Effects

NASA Technical Reports Server (NTRS)

Chen, Ching-Sen; Chen, Wan-Chin; Tao, Wei-Kuo

2004-01-01

On the windward side of southwestern Taiwan, about a quarter to a half of all rainfall during mid-July through August from 1994 to 2000 came from convective systems embedded in the southwesterly monsoon flow. k this study, the causes of two heavy rainfall events (daily rainfall exceeding 100 mm day over at least three rainfall stations) observed over the slopes and/or lowlands of southwestern Taiwan were examined. Data from European Center for Medium-Range Weather Forecasts /Tropical Ocean- Global Atmosphere (EC/TOGA) analyses, the rainfall stations of the Automatic Rainfall and Meteorological Telemetry System (ARMTS) and the conventional surface stations over Taiwan, and the simulation results from a regional-scale numerical model were used to accomplish the objectives. In one event (393 mm day on 9 August 1999), heavy rainfall was observed over the windward slopes of southern Taiwan in a potentially unstable environment with very humid air around 850 hPa. The extreme accumulation was simulated and attributed to orographic lifting effects. No preexisting convection drifted in from the Taiwan Strait into western Taiwan.

Cave air and hydrological controls on prior calcite precipitation and stalagmite growth rates: Implications for palaeoclimate reconstructions using speleothems

NASA Astrophysics Data System (ADS)

Sherwin, Catherine M.; Baldini, James U. L.

2011-07-01

Hourly resolved cave air P and cave drip water hydrochemical data illustrate that calcite deposition on stalagmites can be modulated by prior calcite precipitation (PCP) on extremely short timescales. A very clear second-order covariation between cave air P and drip water Ca 2+ concentrations during the winter months demonstrates the effects of degassing-induced PCP on drip water chemistry. Estimating the strength of the cave air P control on PCP is possible because the PCP signal is so clear; at our drip site a one ppm shift in Ca 2+ concentrations requires a P shift of between 333 and 667 ppm. This value will undoubtedly vary from site to site, depending on drip water flow rate, residence time, drip water-cave air P differential, and availability of low P void spaces in the vadose zone above the cave. High-resolution cave environmental measurements were used to model calcite deposition on one stalagmite in Crag Cave, SW Ireland, and modelled growth over the study period (222 μm over 171 days) is extremely similar to the amount of actual calcite growth (240 μm) over the same time interval, strongly suggesting that equations used to estimate stalagmite growth rates are valid. Although cave air P appears to control drip water hydrochemistry in the winter, drip water dilution caused by rain events may have played a larger role during the summer, as evidenced by a series of sudden drops in Ca 2+ concentrations (dilution) followed by much more gradual increases in drip water Ca 2+ concentrations (slow addition of diffuse water). This research demonstrates that PCP on stalactites, cave ceilings, and void spaces within the karst above the cave partially controls drip water chemistry, and that thorough characterisation of this process at individual caves is necessary to most accurately interpret climate records from those sites.

The Relationship Between Anomalous Presummer Extreme Rainfall Over South China and Synoptic Disturbances

NASA Astrophysics Data System (ADS)

Huang, Ling; Luo, Yali; Zhang, Da-Lin

2018-04-01

A spectral analysis of daily rainfall data has been performed to investigate extreme rainfall events in south China during the presummer rainy seasons between 1998 and 2015 (excluding 1999, 2006, 2011, and 2014). The results reveal a dominant frequency mode at the synoptic scale with pronounced positive rainfall anomalies. By analyzing the synoptic-scale bandpass-filtered anomalous circulations, 24 extreme rainfall episodes (defined as those with a daily rainfall amount in the top 5%) are categorized into "cyclone" (15) and "trough" (8) types, with the remaining events as an "anticyclone" type, according to the primary anomalous weather system contributing to each extreme rainfall episode. The 15 cyclone-type episodes are further separated into (11) lower- and (4) upper-tropospheric migratory anomalies. An analysis of their anomalous fields shows that both types could be traced back to the generation of cyclonic anomalies downstream of the Tibetan Plateau, except for two episodes of lower-tropospheric migratory anomalies originating over the South China Sea. However, a lower-tropospheric cyclonic anomaly appears during all phases in the former type, but only in the wettest phase in the latter type, with its peak disturbance occurring immediately beneath an upper-level warm anomaly. The production of extreme rainfall in the trough-type episodes is closely related to a deep trough anomaly extending from an intense cyclonic anomaly over north China, which in turn could be traced back to a midlatitude Rossby wave train passing by the Tibetan Plateau. The results have important implications for understanding the origin, structure, and evolution of synoptic disturbances associated with the presummer extreme rainfall in south China.

Fluid leakage near the percolation threshold

NASA Astrophysics Data System (ADS)

Dapp, Wolf B.; Müser, Martin H.

2016-02-01

Percolation is a concept widely used in many fields of research and refers to the propagation of substances through porous media (e.g., coffee filtering), or the behaviour of complex networks (e.g., spreading of diseases). Percolation theory asserts that most percolative processes are universal, that is, the emergent powerlaws only depend on the general, statistical features of the macroscopic system, but not on specific details of the random realisation. In contrast, our computer simulations of the leakage through a seal—applying common assumptions of elasticity, contact mechanics, and fluid dynamics—show that the critical behaviour (how the flow ceases near the sealing point) solely depends on the microscopic details of the last constriction. It appears fundamentally impossible to accurately predict from statistical properties of the surfaces alone how strongly we have to tighten a water tap to make it stop dripping and also how it starts dripping once we loosen it again.

Commercial application of rainfall simulation

NASA Astrophysics Data System (ADS)

Loch, Rob J.

2010-05-01

Landloch Pty Ltd is a commercial consulting firm, providing advice on a range of land management issues to the mining and construction industries in Australia. As part of the company's day-to-day operations, rainfall simulation is used to assess material erodibility and to investigate a range of site attributes. (Landloch does carry out research projects, though such are not its core business.) When treated as an everyday working tool, several aspects of rainfall simulation practice are distinctively modified. Firstly, the equipment used is regularly maintained, and regularly upgraded with a primary focus on ease, safety, and efficiency of use and on reliability of function. As well, trained and experienced technical support is considered essential. Landloch's chief technician has over 10 years experience in running rainfall simulators at locations across Australia and in Africa and the Pacific. Secondly, the specific experimental conditions established for each set of rainfall simulator runs are carefully considered to ensure that they accurately represent the field conditions to which the data will be subsequently applied. Considerations here include: • wetting and drying cycles to ensure material consolidation and/or cementation if appropriate; • careful attention to water quality if dealing with clay soils or with amendments such as gypsum; • strong focus on ensuring that the erosion processes considered are those of greatest importance to the field situation of concern; and • detailed description of both material and plot properties, to increase the potential for data to be applicable to a wider range of projects and investigations. Other important company procedures include: • For each project, the scientist or engineer responsible for analysing and reporting rainfall simulator data is present during the running of all field plots, as it is essential that they be aware of any specific conditions that may have developed when the plots were subjected to rain; and • Regular calibration of all equipment. In general, typical errors when rainfall simulation is carried out by inexperienced researchers include: • Failure to accurately measure rainfall rates (the most common error); • Inappropriate initial conditions, including wetting treatments; • Use of inappropriately small plots - relating to our concern at the erosion processes considered be those of genuine field relevance; • Inappropriate rainfall kinetic energies; and • Failure to observe critical processes operating on the study plots, such as saturation excess or the presence of impeding layers at shallow depths. Landloch regularly uses erodibility data to design stable batter profiles for minesite waste dumps. Subsequent monitoring of designed dumps has confirmed that modelled erosion rates are consistent with those subsequently measured under field conditions.

A comparison of methods to estimate future sub-daily design rainfall

NASA Astrophysics Data System (ADS)

Li, J.; Johnson, F.; Evans, J.; Sharma, A.

2017-12-01

Warmer temperatures are expected to increase extreme short-duration rainfall due to the increased moisture-holding capacity of the atmosphere. While attention has been paid to the impacts of climate change on future design rainfalls at daily or longer time scales, the potential changes in short duration design rainfalls have been often overlooked due to the limited availability of sub-daily projections and observations. This study uses a high-resolution regional climate model (RCM) to predict the changes in sub-daily design rainfalls for the Greater Sydney region in Australia. Sixteen methods for predicting changes to sub-daily future extremes are assessed based on different options for bias correction, disaggregation and frequency analysis. A Monte Carlo cross-validation procedure is employed to evaluate the skill of each method in estimating the design rainfall for the current climate. It is found that bias correction significantly improves the accuracy of the design rainfall estimated for the current climate. For 1 h events, bias correcting the hourly annual maximum rainfall simulated by the RCM produces design rainfall closest to observations, whereas for multi-hour events, disaggregating the daily rainfall total is recommended. This suggests that the RCM fails to simulate the observed multi-duration rainfall persistence, which is a common issue for most climate models. Despite the significant differences in the estimated design rainfalls between different methods, all methods lead to an increase in design rainfalls across the majority of the study region.

Simulation of rainfall-runoff for major flash flood events in Karachi

NASA Astrophysics Data System (ADS)

Zafar, Sumaira

2016-07-01

Metropolitan city Karachi has strategic importance for Pakistan. With the each passing decade the city is facing urban sprawl and rapid population growth. These rapid changes directly affecting the natural resources of city including its drainage pattern. Karachi has three major cities Malir River with the catchment area of 2252 sqkm and Lyari River has catchment area about 470.4 sqkm. These are non-perennial rivers and active only during storms. Change of natural surfaces into hard pavement causing an increase in rainfall-runoff response. Curve Number is increased which is now causing flash floods in the urban locality of Karachi. There is only one gauge installed on the upstream of the river but there no record for the discharge. Only one gauge located at the upstream is not sufficient for discharge measurements. To simulate the maximum discharge of Malir River rainfall (1985 to 2014) data were collected from Pakistan meteorological department. Major rainfall events use to simulate the rainfall runoff. Maximum rainfall-runoff response was recorded in during 1994, 2007 and 2013. This runoff causes damages and inundation in floodplain areas of Karachi. These flash flooding events not only damage the property but also cause losses of lives

Multifractal characterisation of a simulated surface flow: A case study with Multi-Hydro in Jouy-en-Josas, France

NASA Astrophysics Data System (ADS)

Gires, Auguste; Abbes, Jean-Baptiste; da Silva Rocha Paz, Igor; Tchiguirinskaia, Ioulia; Schertzer, Daniel

2018-03-01

In this paper we suggest to innovatively use scaling laws and more specifically Universal Multifractals (UM) to analyse simulated surface runoff and compare the retrieved scaling features with the rainfall ones. The methodology is tested on a 3 km2 semi-urbanised with a steep slope study area located in the Paris area along the Bièvre River. First Multi-Hydro, a fully distributed model is validated on this catchment for four rainfall events measured with the help of a C-band radar. The uncertainty associated with small scale unmeasured rainfall, i.e. occurring below the 1 km × 1 km × 5 min observation scale, is quantified with the help of stochastic downscaled rainfall fields. It is rather significant for simulated flow and more limited on overland water depth for these rainfall events. Overland depth is found to exhibit a scaling behaviour over small scales (10 m-80 m) which can be related to fractal features of the sewer network. No direct and obvious dependency between the overland depth multifractal features (quality of the scaling and UM parameters) and the rainfall ones was found.

Safety and Time Course of Drip-and-Ship in Treatment of Acute Ischemic Stroke.

PubMed

Ishihara, Hideyuki; Oka, Fumiaki; Oku, Takayuki; Shinoyama, Mizuya; Suehiro, Eiichi; Sugimoto, Kazutaka; Suzuki, Michiyasu

2017-11-01

The drip-and-ship approach allows intravenous tissue plasminogen activator therapy and adjuvant endovascular treatment in acute ischemic stroke, even in rural areas. Here, we examined the safety and time course of the drip-and-ship approach. Fifty consecutive cases treated with the drip-and-ship approach (drip-and-ship group) in June 2009 to March 2016 were retrospectively examined. Changes in mean blood pressure, systemic complications, and neurological complications were compared according to method of transportation. Time courses were compared between drip-and-ship and direct admission groups during the same period. In the drip-and-ship group, 33 and 17 patients were transferred to hospital by ambulance and helicopter, respectively. One patient suffered hemorrhagic infarction during transportation by ambulance. Mean blood pressure change was lower in patients transferred by helicopter than ambulance (<5 mmHg versus 12.2 mmHg, respectively). The mean onset-to-door times in the drip-and-ship and direct admission groups were 71 and 64 minutes, respectively, and mean door-to-needle times were 70 and 47 minutes, respectively (P =.002). Although mean transportation time from the primary stroke hospital to our hospital was 32 minutes, the entry-to-exit time from the primary stroke hospital was 113 minutes. Thereafter, there was an average delay of 100 minutes until reperfusion compared with the direct admission group. Drip-and-ship was relatively safe in this small series. Transportation by helicopter was less stressful for acute ischemic stroke patients. It is important to reduce door-to-needle time and needle-to-departure time in the primary stroke hospital to minimize the time until treatment in cases of acute ischemic stroke. Copyright © 2017. Published by Elsevier Inc.

Effects of application methods of metam sodium and plastic covers on horizontal and vertical distributions of methyl isothiocyanate in bedded field plots.

PubMed

Ou, Li-Tse; Thomas, John E; Allen, L Hartwell; Vu, Joseph C; Dickson, Donald W

2006-08-01

This study was conducted to examine the effects of three application methods of metam sodium (broadcast, single irrigation drip tape delivery, and double irrigation drip tape delivery) and two plastic covers (polyethylene film and virtually impermeable film) on volatilization and on horizontal and vertical distributions of the biologically active product of metam sodium, methyl isothiocyanate (MITC), in field plots in a Florida sandy soil. Volatilization of MITC from field beds lasted for about 20 hours after completion of metam sodium application regardless of application methods. Virtually impermeable film (VIF) was a better barrier to reduce volatilization loss than polyethylene film (PE). Since water was not applied during broadcast application, MITC was mainly retained in the shallow soil layer (0- to 20-cm depth) and downward movement of MITC was limited to about 30 cm. Large values of standard deviation indicated that initial spatial distribution of MITC in the root zone (10- and 20-cm depths) of the two broadcast applied beds covered with PE or VIF was variable. Twice more water was delivered through the single drip tape than through individual tapes of double drip tape treatments during drip application of metam sodium. More water from the single drip tape likely facilitated downward movement of MITC to at least 60-cm depth, but MITC did not penetrate to this depth in the double drip tape beds. On the other hand, horizontal distribution of MITC in the root zone (10- and 20-cm depths) in the double drip tape beds was more uniform than in the single drip tape beds. More MITC was retained in the subsurface of the VIF-covered beds regardless of application methods than in the PE-covered beds.

Modelling soil erosion in rainfed vineyards of northeast of Spain under climate change: effects of increasing rainfall intensity

NASA Astrophysics Data System (ADS)

Concepción Ramos, Maria

2017-04-01

This aim of the research was to analyse the effect of rainfall distribution and intensity on soil erosion in vines cultivated in the Mediterranean under the projected climate change scenario. The simulations were done at plot scale using the WEPP model. Climatic data for the period 1996-2014 were obtained from a meteorological station located 6km far from the plot. Soil characteristics such as texture, organic matter content, water retention capacity and infiltration were analysed. Runoff and soil losses were measured at four locations within the plot during 4 years and used to calibrate and validate the model. According to evidences recorded in the area, changes of rainfall intensities of 10 and 20% were considered for different rainfall distributions. The simulations were extended to the predicted changes for 2030, 2050 and 2070 based on the HadGEM2-CC under the Representative Concentration Pathways (RCPs) 8.5 scenario. WEPP model provided a suitable prediction of the seasonal runoff and erosion as simulated relatively well the runoff and erosion of the most important events although some deficiencies were found for those events that produced low runoff. The simulation confirmed the contribution of the extreme events to annual erosion rates in 70%, on average. The model responded to changes in precipitation predicted under a climate change scenario with a decrease of runoff and erosion, and with higher erosion rates for an increase in rainfall intensity. A 10% increase may imply erosion rates up to 22% greater for the scenario 2030, and despite the predicted decrease in precipitation for the scenario 2050, soil losses may be up to 40% greater than at present for some rainfall distributions and intensity rainfall increases of 20%. These findings show the need of considering rainfall intensity as one of the main driven factors when soil erosion rates under climate change are predicted. Keywords: extreme events, rainfall distribution, runoff, soil losses, wines, WEPP.

South Asian summer monsoon breaks: Process-based diagnostics in HIRHAM5

NASA Astrophysics Data System (ADS)

Hanf, Franziska S.; Annamalai, H.; Rinke, Annette; Dethloff, Klaus

2017-05-01

This study assesses the ability of a high-resolution downscaling simulation with the regional climate model (RCM) HIRHAM5 in capturing the monsoon basic state and boreal summer intraseasonal variability (BSISV) over South Asia with focus on moist and radiative processes during 1979-2012. A process-based vertically integrated moist static energy (MSE) budget is performed to understand the model's fidelity in representing leading processes that govern the monsoon breaks over continental India. In the climatology (June-September) HIRHAM5 simulates a dry bias over central India in association with descent throughout the free troposphere. Sources of dry bias are interpreted as (i) near-equatorial Rossby wave response forced by excess rainfall over the southern Bay of Bengal promotes anomalous descent to its northwest and (ii) excessive rainfall over near-equatorial Arabian Sea and Bay of Bengal anchor a "local Hadley-type" circulation with descent anomalies over continental India. Compared with observations HIRHAM5 captures the leading processes that account for breaks, although with generally reduced amplitudes over central India. In the model too, anomalous dry advection and net radiative cooling are responsible for the initiation and maintenance of breaks, respectively. However, weaker contributions of all adiabatic MSE budget terms, and an inconsistent relationship between negative rainfall anomalies and radiative cooling reveals shortcomings in HIRHAM5's moisture-radiation interaction. Our study directly implies that process-based budget diagnostics are necessary, apart from just checking the northward propagation feature to examine RCM's fidelity to simulate BSISV.

POLYNOMIAL-BASED DISAGGREGATION OF HOURLY RAINFALL FOR CONTINUOUS HYDROLOGIC SIMULATION

EPA Science Inventory

Hydrologic modeling of urban watersheds for designs and analyses of stormwater conveyance facilities can be performed in either an event-based or continuous fashion. Continuous simulation requires, among other things, the use of a time series of rainfall amounts. However, for urb...

Parameter Tuning and Calibration of RegCM3 with MIT-Emanuel Cumulus Parameterization Scheme over CORDEX East Asian Domain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou, Liwei; Qian, Yun; Zhou, Tianjun

2014-10-01

In this study, we calibrated the performance of regional climate model RegCM3 with Massachusetts Institute of Technology (MIT)-Emanuel cumulus parameterization scheme over CORDEX East Asia domain by tuning the selected seven parameters through multiple very fast simulated annealing (MVFSA) sampling method. The seven parameters were selected based on previous studies, which customized the RegCM3 with MIT-Emanuel scheme through three different ways by using the sensitivity experiments. The responses of model results to the seven parameters were investigated. Since the monthly total rainfall is constrained, the simulated spatial pattern of rainfall and the probability density function (PDF) distribution of daily rainfallmore » rates are significantly improved in the optimal simulation. Sensitivity analysis suggest that the parameter “relative humidity criteria” (RH), which has not been considered in the default simulation, has the largest effect on the model results. The responses of total rainfall over different regions to RH were examined. Positive responses of total rainfall to RH are found over northern equatorial western Pacific, which are contributed by the positive responses of explicit rainfall. Followed by an increase of RH, the increases of the low-level convergence and the associated increases in cloud water favor the increase of the explicit rainfall. The identified optimal parameters constrained by the total rainfall have positive effects on the low-level circulation and the surface air temperature. Furthermore, the optimized parameters based on the extreme case are suitable for a normal case and the model’s new version with mixed convection scheme.« less

The western Pacific monsoon in CMIP5 models: Model evaluation and projections

NASA Astrophysics Data System (ADS)

Brown, Josephine R.; Colman, Robert A.; Moise, Aurel F.; Smith, Ian N.

2013-11-01

ability of 35 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to simulate the western Pacific (WP) monsoon is evaluated over four representative regions around Timor, New Guinea, the Solomon Islands and Palau. Coupled model simulations are compared with atmosphere-only model simulations (with observed sea surface temperatures, SSTs) to determine the impact of SST biases on model performance. Overall, the CMIP5 models simulate the WP monsoon better than previous-generation Coupled Model Intercomparison Project Phase 3 (CMIP3) models, but some systematic biases remain. The atmosphere-only models are better able to simulate the seasonal cycle of zonal winds than the coupled models, but display comparable biases in the rainfall. The CMIP5 models are able to capture features of interannual variability in response to the El Niño-Southern Oscillation. In climate projections under the RCP8.5 scenario, monsoon rainfall is increased over most of the WP monsoon domain, while wind changes are small. Widespread rainfall increases at low latitudes in the summer hemisphere appear robust as a large majority of models agree on the sign of the change. There is less agreement on rainfall changes in winter. Interannual variability of monsoon wet season rainfall is increased in a warmer climate, particularly over Palau, Timor and the Solomon Islands. A subset of the models showing greatest skill in the current climate confirms the overall projections, although showing markedly smaller rainfall increases in the western equatorial Pacific. The changes found here may have large impacts on Pacific island countries influenced by the WP monsoon.

Combined effects of constant versus variable intensity simulated rainfall and reduced tillage management on cotton preemergence herbicide runoff.

PubMed

Potter, Thomas L; Truman, Clint C; Strickland, Timothy C; Bosch, David D; Webster, Theodore M; Franklin, Dorcas H; Bednarz, Craig W

2006-01-01

Pesticide runoff research relies heavily on rainfall simulation experiments. Most are conducted at a constant intensity, i.e., at a fixed rainfall rate; however, large differences in natural rainfall intensity is common. To assess implications we quantified runoff of two herbicides, fluometuron and pendimethalin, and applied preemergence after planting cotton on Tifton loamy sand. Rainfall at constant and variable intensity patterns representative of late spring thunderstorms in the Atlantic Coastal Plain region of Georgia (USA) were simulated on 6-m2 plots under strip- (ST) and conventional-tillage (CT) management. The variable pattern produced significantly higher runoff rates of both compounds from CT but not ST plots. However, on an event-basis, runoff totals (% applied) were not significantly different, with one exception: fluometuron runoff from CT plots. There was about 25% more fluometuron runoff with the variable versus the constant intensity pattern (P = 0.10). Study results suggest that conduct of simulations using variable intensity storm patterns may provide more representative rainfall simulation-based estimates of pesticide runoff and that the greatest impacts will be observed with CT. The study also found significantly more fluometuron in runoff from ST than CT plots. Further work is needed to determine whether this behavior may be generalized to other active ingredients with similar properties [low K(oc) (organic carbon partition coefficient) approximately 100 mL g(-1); high water solubility approximately 100 mg L(-1)]. If so, it should be considered when making tillage-specific herbicide recommendations to reduce runoff potential.

Spatial structure of monthly rainfall measurements average over 25 years and trends of the hourly variability of a current rainy day in Rwanda.

NASA Astrophysics Data System (ADS)

Nduwayezu, Emmanuel; Kanevski, Mikhail; Jaboyedoff, Michel

2013-04-01

Climate plays a vital role in a wide range of socio-economic activities of most nations particularly of developing countries. Climate (rainfall) plays a central role in agriculture which is the main stay of the Rwandan economy and community livelihood and activities. The majority of the Rwandan population (81,1% in 2010) relies on rain fed agriculture for their livelihoods, and the impacts of variability in climate patterns are already being felt. Climate-related events like heavy rainfall or too little rainfall are becoming more frequent and are impacting on human wellbeing.The torrential rainfall that occurs every year in Rwanda could disturb the circulation for many days, damages houses, infrastructures and causes heavy economic losses and deaths. Four rainfall seasons have been identified, corresponding to the four thermal Earth ones in the south hemisphere: the normal season (summer), the rainy season (autumn), the dry season (winter) and the normo-rainy season (spring). Globally, the spatial rainfall decreasing from West to East, especially in October (spring) and February (summer) suggests an «Atlantic monsoon influence» while the homogeneous spatial rainfall distribution suggests an «Inter-tropical front» mechanism. What is the hourly variability in this mountainous area? Is there any correlation with the identified zones of the monthly average series (from 1965 to 1990 established by the Rwandan meteorological services)? Where could we have hazards with several consecutive rainy days (using forecasted datas from the Norwegian Meteorological Institute)? Spatio-temporal analysis allows for identifying and explaining large-scale anomalies which are useful for understanding hydrological characteristics and subsequently predicting these hydrological events. The objective of our current research (Rainfall variability) is to proceed to an evaluation of the potential rainfall risk by applying advanced geospatial modelling tools in Rwanda: geostatistical predictions and simulations, machine learning algorithm (different types of neural networks) and GIS. Hybrid models - mixing geostatistics and machine learning, will be applied to study spatial non-stationarity of rainfall fields. The research will include rainfalls variability mapping and probabilistic analyses of extreme events. Key words: rainfall variability, Rwanda, extreme event, model, mapping, geostatistics.

Scaling of hydrologic and erosion parameters derived from rainfall simulation

NASA Astrophysics Data System (ADS)

Sheridan, Gary; Lane, Patrick; Noske, Philip; Sherwin, Christopher

2010-05-01

Rainfall simulation experiments conducted at the temporal scale of minutes and the spatial scale of meters are often used to derive parameters for erosion and water quality models that operate at much larger temporal and spatial scales. While such parameterization is convenient, there has been little effort to validate this approach via nested experiments across these scales. In this paper we first review the literature relevant to some of these long acknowledged issues. We then present rainfall simulation and erosion plot data from a range of sources, including mining, roading, and forestry, to explore the issues associated with the scaling of parameters such as infiltration properties and erodibility coefficients.

A model of nitrous oxide evolution from soil driven by rainfall events. I - Model structure and sensitivity. II - Model applications

NASA Technical Reports Server (NTRS)

Changsheng, LI; Frolking, Steve; Frolking, Tod A.

1992-01-01

Simulations of N2O and CO2 emissions from soils were conducted with a rain-event driven, process-oriented model (DNDC) of nitrogen and carbon cycling processes in soils. The magnitude and trends of simulated N2O (or N2O + N2) and CO2 emissions were consistent with the results obtained in field experiments. The successful simulation of these emissions from the range of soil types examined demonstrates that the DNDC will be a useful tool for the study of linkages among climate, soil-atmosphere interactions, land use, and trace gas fluxes.

Observed and simulated hydrologic response for a first-order catchment during extreme rainfall 3 years after wildfire disturbance

USGS Publications Warehouse

Ebel, Brian A.; Rengers, Francis K.; Tucker, Gregory E.

2016-01-01

Hydrologic response to extreme rainfall in disturbed landscapes is poorly understood because of the paucity of measurements. A unique opportunity presented itself when extreme rainfall in September 2013 fell on a headwater catchment (i.e., <1 ha) in Colorado, USA that had previously been burned by a wildfire in 2010. We compared measurements of soil-hydraulic properties, soil saturation from subsurface sensors, and estimated peak runoff during the extreme rainfall with numerical simulations of runoff generation and subsurface hydrologic response during this event. The simulations were used to explore differences in runoff generation between the wildfire-affected headwater catchment, a simulated unburned case, and for uniform versus spatially variable parameterizations of soil-hydraulic properties that affect infiltration and runoff generation in burned landscapes. Despite 3 years of elapsed time since the 2010 wildfire, observations and simulations pointed to substantial surface runoff generation in the wildfire-affected headwater catchment by the infiltration-excess mechanism while no surface runoff was generated in the unburned case. The surface runoff generation was the result of incomplete recovery of soil-hydraulic properties in the burned area, suggesting recovery takes longer than 3 years. Moreover, spatially variable soil-hydraulic property parameterizations produced longer duration but lower peak-flow infiltration-excess runoff, compared to uniform parameterization, which may have important hillslope sediment export and geomorphologic implications during long duration, extreme rainfall. The majority of the simulated surface runoff in the spatially variable cases came from connected near-channel contributing areas, which was a substantially smaller contributing area than the uniform simulations.

Rainfall-triggered shallow landslides at catchment scale: Threshold mechanics-based modeling for abruptness and localization

NASA Astrophysics Data System (ADS)

von Ruette, J.; Lehmann, P.; Or, D.

2013-10-01

Rainfall-induced shallow landslides may occur abruptly without distinct precursors and could span a wide range of soil mass released during a triggering event. We present a rainfall-induced landslide-triggering model for steep catchments with surfaces represented as an assembly of hydrologically and mechanically interconnected soil columns. The abruptness of failure was captured by defining local strength thresholds for mechanical bonds linking soil and bedrock and adjacent columns, whereby a failure of a single bond may initiate a chain reaction of subsequent failures, culminating in local mass release (a landslide). The catchment-scale hydromechanical landslide-triggering model (CHLT) was applied to results from two event-based landslide inventories triggered by two rainfall events in 2002 and 2005 in two nearby catchments located in the Prealps in Switzerland. Rainfall radar data, surface elevation and vegetation maps, and a soil production model for soil depth distribution were used for hydromechanical modeling of failure patterns for the two rainfall events at spatial and temporal resolutions of 2.5 m and 0.02 h, respectively. The CHLT model enabled systematic evaluation of the effects of soil type, mechanical reinforcement (soil cohesion and lateral root strength), and initial soil water content on landslide characteristics. We compared various landslide metrics and spatial distribution of simulated landslides in subcatchments with observed inventory data. Model parameters were optimized for the short but intense rainfall event in 2002, and the calibrated model was then applied for the 2005 rainfall, yielding reasonable predictions of landslide events and volumes and statistically reproducing localized landslide patterns similar to inventory data. The model provides a means for identifying local hot spots and offers insights into the dynamics of locally resolved landslide hazards in mountainous regions.

Exploring the Variability of Short-term Precipitation and Hydrological Response of Small Czech Watersheds

NASA Astrophysics Data System (ADS)

Kavka, Petr; Strouhal, Ludek; Weyskrabova, Lenka; Müller, Miloslav; Kozant, Petr

2017-04-01

The short-term rainfall temporal distribution is known to have a significant effect on the small watersheds' hydrological response. In Czech Republic there are limited publicly available data on rainfall patterns of short-term precipitation. On one side there are catalogues of very short-term synthetic rainfalls used in urban drainage planning and on the other side hourly distribution of daily totals of rainfalls with long return period for larger catchments analyses. This contribution introduces the preliminary outcomes of a running three years' project, which should bridge this gap and provide such data and methodology to the community of scientists, state administration as well as design planners. Six generalized 6-hours hyetographs with 1 minute resolution were derived from 10 years of radar and gauging stations data. These hyetographs are accompanied with information concerning the region of occurrence as well as their frequency related to the rainfall amount. In the next step these hyetographs are used in a complex sensitivity analysis focused on a rainfall-runoff response of small watersheds. This analysis takes into account the uncertainty related to type of the hydrological model, watershed characteristics and main model routines parameterization. Five models with different methods and structure are considered and each model is applied on 5 characteristic watersheds selected from a classification of 7700 small Czech watersheds. For each combination of model and watershed 30, rainfall scenarios were simulated and other scenarios will be used to address the parameters uncertainty. In the last step the variability of outputs will be assessed in the context of economic impacts on design of landscape water structures or mitigation measures. The research is supported by the grant QJ1520265 of the Czech Ministry of Agriculture, rainfall data were provided by the Czech Hydrometeorological Institute.

Selection of meteorological parameters affecting rainfall estimation using neuro-fuzzy computing methodology

NASA Astrophysics Data System (ADS)

Hashim, Roslan; Roy, Chandrabhushan; Motamedi, Shervin; Shamshirband, Shahaboddin; Petković, Dalibor; Gocic, Milan; Lee, Siew Cheng

2016-05-01

Rainfall is a complex atmospheric process that varies over time and space. Researchers have used various empirical and numerical methods to enhance estimation of rainfall intensity. We developed a novel prediction model in this study, with the emphasis on accuracy to identify the most significant meteorological parameters having effect on rainfall. For this, we used five input parameters: wet day frequency (dwet), vapor pressure (e̅a), and maximum and minimum air temperatures (Tmax and Tmin) as well as cloud cover (cc). The data were obtained from the Indian Meteorological Department for the Patna city, Bihar, India. Further, a type of soft-computing method, known as the adaptive-neuro-fuzzy inference system (ANFIS), was applied to the available data. In this respect, the observation data from 1901 to 2000 were employed for testing, validating, and estimating monthly rainfall via the simulated model. In addition, the ANFIS process for variable selection was implemented to detect the predominant variables affecting the rainfall prediction. Finally, the performance of the model was compared to other soft-computing approaches, including the artificial neural network (ANN), support vector machine (SVM), extreme learning machine (ELM), and genetic programming (GP). The results revealed that ANN, ELM, ANFIS, SVM, and GP had R2 of 0.9531, 0.9572, 0.9764, 0.9525, and 0.9526, respectively. Therefore, we conclude that the ANFIS is the best method among all to predict monthly rainfall. Moreover, dwet was found to be the most influential parameter for rainfall prediction, and the best predictor of accuracy. This study also identified sets of two and three meteorological parameters that show the best predictions.

WRF simulation of a severe hailstorm over Baramati: a study into the space-time evolution

NASA Astrophysics Data System (ADS)

Murthy, B. S.; Latha, R.; Madhuparna, H.

2018-04-01

Space-time evolution of a severe hailstorm occurred over the western India as revealed by WRF-ARW simulations are presented. We simulated a specific event centered over Baramati (18.15°N, 74.58°E, 537 m AMSL) on March 9, 2014. A physical mechanism, proposed as a conceptual model, signifies the role of multiple convective cells organizing through outflows leading to a cold frontal type flow, in the presence of a low over the northern Arabian Sea, propagates from NW to SE triggering deep convection and precipitation. A `U' shaped cold pool encircled by a converging boundary forms to the north of Baramati due to precipitation behind the moisture convergence line with strong updrafts ( 15 ms-1) leading to convective clouds extending up to 8 km in a narrow region of 30 km. The outflows from the convective clouds merge with the opposing southerly or southwesterly winds from the Arabian Sea and southerly or southeasterly winds from the Bay of Bengal resulting in moisture convergence (maximum 80 × 10-3 g kg-1 s-1). The vertical profile of the area-averaged moisture convergence over the cold pool shows strong convergence above 850 hPa and divergence near the surface indicating elevated convection. Radar reflectivity (50-60 dBZ) and vertical component of vorticity maximum ( 0.01-0.14 s-1) are observed along the convergence zone. Stratiform clouds ahead of the squall line and parallel wind flow at 850 hPa and nearly perpendicular flow at higher levels relative to squall line as evidenced by relatively low and wide-spread reflectivity suggests that organizational mode of squall line may be categorized as `Mixed Mode' type where northern part can be a parallel stratiform while the southern part resembles with a leading stratiform. Simulated rainfall (grid scale 27 km) leads the observed rainfall by 1 h while its magnitude is 2 times of the observed rainfall (grid scale 100 km) derived from Kalpana-1. Thus, this study indicates that under synoptically favorable conditions, WRF-ARW could simulate thunderstorm evolution reasonably well although there is some space-time error which might, perhaps, be the reason for lower CAPE (observed by upper air sounding) on the simulation day.

Daily Practice: Ethics in Leadership

ERIC Educational Resources Information Center

DePree, Chauncey M., Jr.; Jude, Rebecca K.

2010-01-01

The classic question, "Should business schools teach ethics?" is not often asked anymore given the drip, drip, drip of business corruption reported in the news. Even skeptics allow that business ethics education could not hurt and might improve the ethics of business leaders. Furthermore, universities, colleges, and business accrediting…

A comparison of precision mobile drip irrigation, LESA and LEPA

USDA-ARS?s Scientific Manuscript database

Precision mobile drip irrigation (PMDI) is a surface drip irrigation system fitted onto moving sprinkler systems that applies water through the driplines as they are dragged across the field. This application method can conserve water by limiting runoff, and reducing evaporative losses since the wat...

Impact of rainfall pattern on interrill erosion process

USDA-ARS?s Scientific Manuscript database

The impact of rainfall pattern on the interrill erosion process is not fully understood despite its importance. Systematic rainfall simulation experiments involving different rain intensities, stages, intensity sequences, and surface cover conditions were conducted to investigate the impacts of rain...

Predictability of two types of El Niño and their climate impacts in boreal spring to summer in coupled models

NASA Astrophysics Data System (ADS)

Lee, Ray Wai-Ki; Tam, Chi-Yung; Sohn, Soo-Jin; Ahn, Joong-Bae

2017-12-01

The predictability of the two El Niño types and their different impacts on the East Asian climate from boreal spring to summer have been studied, based on coupled general circulation models (CGCM) simulations from the APEC Climate Center (APCC) multi-model ensemble (MME) hindcast experiments. It was found that both the spatial pattern and temporal persistence of canonical (eastern Pacific type) El Niño sea surface temperature (SST) are much better simulated than those for El Niño Modoki (central Pacific type). In particular, most models tend to have El Niño Modoki events that decay too quickly, in comparison to those observed. The ability of these models in distinguishing between the two types of ENSO has also been assessed. Based on the MME average, the two ENSO types become less and less differentiated in the model environment as the forecast leadtime increases. Regarding the climate impact of ENSO, in spring during canonical El Niño, coupled models can reasonably capture the anomalous low-level anticyclone over the western north Pacific (WNP)/Philippine Sea area, as well as rainfall over coastal East Asia. However, most models have difficulties in predicting the springtime dry signal over Indochina to South China Sea (SCS) when El Niño Modoki occurs. This is related to the location of the simulated anomalous anticyclone in this region, which is displaced eastward over SCS relative to the observed. In boreal summer, coupled models still exhibit some skills in predicting the East Asian rainfall during canonical El Nino, but not for El Niño Modoki. Overall, models' performance in spring to summer precipitation forecasts is dictated by their ability in capturing the low-level anticyclonic feature over the WNP/SCS area. The latter in turn is likely to be affected by the realism of the time mean monsoon circulation in models.

Impact of animal waste application on runoff water quality in field experimental plots.

PubMed

Hill, Dagne D; Owens, William E; Tchoounwou, Paul B

2005-08-01

Animal waste from dairy and poultry operations is an economical and commonly used fertilizer in the state of Louisiana. The application of animal waste to pasture lands not only is a source of fertilizer, but also allows for a convenient method of waste disposal. The disposal of animal wastes on land is a potential nonpoint source of water degradation. Water degradation and human health is a major concern when considering the disposal of large quantities of animal waste. The objective of this research was to determine the effect of animal waste application on biological (fecal coliform, Enterobacter spp. and Escherichia coli) and physical/chemical (temperature, pH, nitrate nitrogen, ammonia nitrogen, phosphate, copper, zinc, and sulfate) characteristics of runoff water in experimental plots. The effects of the application of animal waste have been evaluated by utilizing experimental plots and simulated rainfall events. Samples of runoff water were collected and analyzed for fecal coliforms. Fecal coliforms isolated from these samples were identified to the species level. Chemical analysis was performed following standard test protocols. An analysis of temperature, ammonia nitrogen, nitrate nitrogen, iron, copper, phosphate, potassium, sulfate, zinc and bacterial levels was performed following standard test protocols as presented in Standard Methods for the Examination of Water and Wastewater [1]. In the experimental plots, less time was required in the tilled broiler litter plots for the measured chemicals to decrease below the initial pre-treatment levels. A decrease of over 50% was noted between the first and second rainfall events for sulfate levels. This decrease was seen after only four simulated rainfall events in tilled broiler litter plots whereas broiler litter plots required eight simulated rainfall events to show this same type of reduction. A reverse trend was seen in the broiler litter plots and the tilled broiler plots for potassium. Bacteria numbers present after the simulated rainfall events were above 200/100 ml of sample water. It can be concluded that: 1) non-point source pollution has a significant effect on bacterial and nutrients levels in runoff water and in water resources; 2) land application of animal waste for soil fertilization makes a significant contribution to water pollution; 3) the use of tilling can significantly reduce the amount of nutrients available in runoff water.

Impact of Animal Waste Application on Runoff Water Quality in Field Experimental Plots

PubMed Central

Hill, Dagne D.; Owens, William E.; Tchounwou, Paul B.

2005-01-01

Animal waste from dairy and poultry operations is an economical and commonly used fertilizer in the state of Louisiana. The application of animal waste to pasture lands not only is a source of fertilizer, but also allows for a convenient method of waste disposal. The disposal of animal wastes on land is a potential nonpoint source of water degradation. Water degradation and human health is a major concern when considering the disposal of large quantities of animal waste. The objective of this research was to determine the effect of animal waste application on biological (fecal coliform, Enterobacter spp. and Escherichia coli) and physical/chemical (temperature, pH, nitrate nitrogen, ammonia nitrogen, phosphate, copper, zinc, and sulfate) characteristics of runoff water in experimental plots. The effects of the application of animal waste have been evaluated by utilizing experimental plots and simulated rainfall events. Samples of runoff water were collected and analyzed for fecal coliforms. Fecal coliforms isolated from these samples were identified to the species level. Chemical analysis was performed following standard test protocols. An analysis of temperature, ammonia nitrogen, nitrate nitrogen, iron, copper, phosphate, potassium, sulfate, zinc and bacterial levels was performed following standard test protocols as presented in Standard Methods for the Examination of Water and Wastewater [1]. In the experimental plots, less time was required in the tilled broiler litter plots for the measured chemicals to decrease below the initial pre-treatment levels. A decrease of over 50% was noted between the first and second rainfall events for sulfate levels. This decrease was seen after only four simulated rainfall events in tilled broiler litter plots whereas broiler litter plots required eight simulated rainfall events to show this same type of reduction. A reverse trend was seen in the broiler litter plots and the tilled broiler plots for potassium. Bacteria numbers present after the simulated rainfall events were above 200/100 ml of sample water. It can be concluded that: 1) non-point source pollution has a significant effect on bacterial and nutrients levels in runoff water and in water resources; 2) land application of animal waste for soil fertilization makes a significant contribution to water pollution; 3) the use of tilling can significantly reduce the amount of nutrients available in runoff water. PMID:16705834

Effect of simulated rainfall and weathering on release of preservative elements from CCA treated wood

Treesearch

Stan Lebow; R. Sam Williams; Patricia Lebow

2003-01-01

The release of arsenic from wood pressure-treated with chromated copper arsenate (CCA) can be decreased by application of wood finishes, but little is known about the types of finishes that are best suited for this purpose. This study evaluated the effects of finish water repellent content and ultraviolet (UV) radiation on the release of arsenic, copper, and chromium...

Evaluating the efficacy of wood shreds for mitigating erosion

Treesearch

Randy B. Foltz; Natalie S. Copeland

2009-01-01

An erosion control product made by shredding on-site woody materials was evaluated for mitigating erosion through a series of rainfall simulations. Tests were conducted on bare soil and soil with 30, 50, and 70% cover on a coarse and a fine-grained soil. Results indicated that the wood product known as wood shreds reduced runoff and soil loss from both soil types....

The added value of convection permitting simulations of extreme precipitation events over the eastern Mediterranean

NASA Astrophysics Data System (ADS)

Zittis, G.; Bruggeman, A.; Camera, C.; Hadjinicolaou, P.; Lelieveld, J.

2017-07-01

Climate change is expected to substantially influence precipitation amounts and distribution. To improve simulations of extreme rainfall events, we analyzed the performance of different convection and microphysics parameterizations of the WRF (Weather Research and Forecasting) model at very high horizontal resolutions (12, 4 and 1 km). Our study focused on the eastern Mediterranean climate change hot-spot. Five extreme rainfall events over Cyprus were identified from observations and were dynamically downscaled from the ERA-Interim (EI) dataset with WRF. We applied an objective ranking scheme, using a 1-km gridded observational dataset over Cyprus and six different performance metrics, to investigate the skill of the WRF configurations. We evaluated the rainfall timing and amounts for the different resolutions, and discussed the observational uncertainty over the particular extreme events by comparing three gridded precipitation datasets (E-OBS, APHRODITE and CHIRPS). Simulations with WRF capture rainfall over the eastern Mediterranean reasonably well for three of the five selected extreme events. For these three cases, the WRF simulations improved the ERA-Interim data, which strongly underestimate the rainfall extremes over Cyprus. The best model performance is obtained for the January 1989 event, simulated with an average bias of 4% and a modified Nash-Sutcliff of 0.72 for the 5-member ensemble of the 1-km simulations. We found overall added value for the convection-permitting simulations, especially over regions of high-elevation. Interestingly, for some cases the intermediate 4-km nest was found to outperform the 1-km simulations for low-elevation coastal parts of Cyprus. Finally, we identified significant and inconsistent discrepancies between the three, state of the art, gridded precipitation datasets for the tested events, highlighting the observational uncertainty in the region.

Impacts of rainfall variability and expected rainfall changes on cost-effective adaptation of water systems to climate change.

PubMed

van der Pol, T D; van Ierland, E C; Gabbert, S; Weikard, H-P; Hendrix, E M T

2015-05-01

Stormwater drainage and other water systems are vulnerable to changes in rainfall and runoff and need to be adapted to climate change. This paper studies impacts of rainfall variability and changing return periods of rainfall extremes on cost-effective adaptation of water systems to climate change given a predefined system performance target, for example a flood risk standard. Rainfall variability causes system performance estimates to be volatile. These estimates may be used to recurrently evaluate system performance. This paper presents a model for this setting, and develops a solution method to identify cost-effective investments in stormwater drainage adaptations. Runoff and water levels are simulated with rainfall from stationary rainfall distributions, and time series of annual rainfall maxima are simulated for a climate scenario. Cost-effective investment strategies are determined by dynamic programming. The method is applied to study the choice of volume for a storage basin in a Dutch polder. We find that 'white noise', i.e. trend-free variability of rainfall, might cause earlier re-investment than expected under projected changes in rainfall. The risk of early re-investment may be reduced by increasing initial investment. This can be cost-effective if the investment involves fixed costs. Increasing initial investments, therefore, not only increases water system robustness to structural changes in rainfall, but could also offer insurance against additional costs that would occur if system performance is underestimated and re-investment becomes inevitable. Copyright © 2015 Elsevier Ltd. All rights reserved.

Drip bloodstain appearance on inclined apparel fabrics: Effect of prior-laundering, fibre content and fabric structure.

PubMed

de Castro, Therese C; Carr, Debra J; Taylor, Michael C; Kieser, Jules A; Duncan, Warwick

2016-09-01

The interaction of blood and fabrics is currently a 'hot topic', since the understanding and interpretation of these stains is still in its infancy. A recent simplified perpendicular impact experimental programme considering bloodstains generated on fabrics laid the foundations for understanding more complex scenarios. Blood rarely impacts apparel fabrics perpendicular; therefore a systematic study was conducted to characterise the appearance of drip stains on inclined fabrics. The final drip stain appearance for 45° and 15° impact angles on torso apparel fabrics (100% cotton plain woven, 100% polyester plain woven, a blend of polyester and cotton plain woven and 100% cotton single jersey knit) that had been laundered for six, 26 and 52 cycles prior to testing was investigated. The relationship between drop parameters (height and volume), angle and the stain characteristics (parent stain area, axis 1 and 2 and number of satellite stains) for each fabric was examined using analysis of variance. The appearance of the drip stains on these fabrics was distorted, in comparison to drip stains on hard-smooth surface. Examining the parent stain allowed for classification of stains occurring at an angle, however the same could not be said for the satellite stains produced. All of the dried stains visible on the surface of the fabric were larger than just after the impacting event, indicating within fabric spreading of blood due to capillary force (wicking). The cotton-containing fabrics spread the blood within the fabrics in all directions along the stain's circumference, while spreading within the polyester plain woven fabric occurred in only the weft (width of the fabric) and warp (length) directions. Laundering affected the formation of bloodstain on the blend plain woven fabric at both impact angles, although not all characteristics were significantly affected for the three impact conditions considered. The bloodstain characteristics varied due to the fibre content and fabric structure for both impact angles investigated. It is therefore necessary to consider the age of the fabric (which is fabric specific), the fibre type (including blends) and the fabric structure, before interpreting bloodstain patterns. An understanding of this simplified inclined drip stain interaction has been investigated to generate a basis for more complex interactions, such as spatter bloodstains. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Impact of atmospheric circulation types on southwest Asian dust and Indian summer monsoon rainfall

NASA Astrophysics Data System (ADS)

Kaskaoutis, D. G.; Houssos, E. E.; Solmon, F.; Legrand, M.; Rashki, A.; Dumka, U. C.; Francois, P.; Gautam, R.; Singh, R. P.

2018-03-01

This study examines the meteorological feedback on dust aerosols and rainfall over the Arabian Sea and India during the summer monsoon using satellite data, re-analysis and a regional climate model. Based on days with excess aerosol loading over the central Ganges basin during May - September, two distinct atmospheric circulation types (weather clusters) are identified, which are associated with different dust-aerosol and rainfall distributions over south Asia, highlighting the role of meteorology on dust emissions and monsoon rainfall. Each cluster is characterized by different patterns of mean sea level pressure (MSLP), geopotential height at 700 hPa (Z700) and wind fields at 1000 hPa and at 700 hPa, thus modulating changes in dust-aerosol loading over the Arabian Sea. One cluster is associated with deepening of the Indian/Pakistan thermal low leading to (i) increased cyclonicity and thermal convection over northwestern India and Arabian Peninsula, (ii) intensification of the southwest monsoon off the Horn of Africa, iii) increase in dust emissions from Rub-Al-Khali and Somalian deserts, (iv) excess dust accumulation over the Arabian Sea and, (v) strengthening of the convergence of humid air masses and larger precipitation over Indian landmass compared to the other cluster. The RegCM4.4 model simulations for dust-aerosol and precipitation distributions support the meteorological fields and satellite observations, while the precipitation over India is positively correlated with the aerosol loading over the Arabian Sea on daily basis for both weather clusters. This study highlights the key role of meteorology and atmospheric dynamics on dust life cycle and rainfall over the monsoon-influenced south Asia.

The error and bias of supplementing a short, arid climate, rainfall record with regional vs. global frequency analysis

NASA Astrophysics Data System (ADS)

Endreny, Theodore A.; Pashiardis, Stelios

2007-02-01

SummaryRobust and accurate estimates of rainfall frequencies are difficult to make with short, and arid-climate, rainfall records, however new regional and global methods were used to supplement such a constrained 15-34 yr record in Cyprus. The impact of supplementing rainfall frequency analysis with the regional and global approaches was measured with relative bias and root mean square error (RMSE) values. Analysis considered 42 stations with 8 time intervals (5-360 min) in four regions delineated by proximity to sea and elevation. Regional statistical algorithms found the sites passed discordancy tests of coefficient of variation, skewness and kurtosis, while heterogeneity tests revealed the regions were homogeneous to mildly heterogeneous. Rainfall depths were simulated in the regional analysis method 500 times, and then goodness of fit tests identified the best candidate distribution as the general extreme value (GEV) Type II. In the regional analysis, the method of L-moments was used to estimate location, shape, and scale parameters. In the global based analysis, the distribution was a priori prescribed as GEV Type II, a shape parameter was a priori set to 0.15, and a time interval term was constructed to use one set of parameters for all time intervals. Relative RMSE values were approximately equal at 10% for the regional and global method when regions were compared, but when time intervals were compared the global method RMSE had a parabolic-shaped time interval trend. Relative bias values were also approximately equal for both methods when regions were compared, but again a parabolic-shaped time interval trend was found for the global method. The global method relative RMSE and bias trended with time interval, which may be caused by fitting a single scale value for all time intervals.

Weather model performance on extreme rainfall events simulation's over Western Iberian Peninsula

NASA Astrophysics Data System (ADS)

Pereira, S. C.; Carvalho, A. C.; Ferreira, J.; Nunes, J. P.; Kaiser, J. J.; Rocha, A.

2012-08-01

This study evaluates the performance of the WRF-ARW numerical weather model in simulating the spatial and temporal patterns of an extreme rainfall period over a complex orographic region in north-central Portugal. The analysis was performed for the December month of 2009, during the Portugal Mainland rainy season. The heavy rainfall to extreme heavy rainfall periods were due to several low surface pressure's systems associated with frontal surfaces. The total amount of precipitation for December exceeded, in average, the climatological mean for the 1971-2000 time period in +89 mm, varying from 190 mm (south part of the country) to 1175 mm (north part of the country). Three model runs were conducted to assess possible improvements in model performance: (1) the WRF-ARW is forced with the initial fields from a global domain model (RunRef); (2) data assimilation for a specific location (RunObsN) is included; (3) nudging is used to adjust the analysis field (RunGridN). Model performance was evaluated against an observed hourly precipitation dataset of 15 rainfall stations using several statistical parameters. The WRF-ARW model reproduced well the temporal rainfall patterns but tended to overestimate precipitation amounts. The RunGridN simulation provided the best results but model performance of the other two runs was good too, so that the selected extreme rainfall episode was successfully reproduced.

On the influence of simulated SST warming on rainfall projections in the Indo-Pacific domain: an AGCM study

NASA Astrophysics Data System (ADS)

Zhang, Huqiang; Zhao, Y.; Moise, A.; Ye, H.; Colman, R.; Roff, G.; Zhao, M.

2018-02-01

Significant uncertainty exists in regional climate change projections, particularly for rainfall and other hydro-climate variables. In this study, we conduct a series of Atmospheric General Circulation Model (AGCM) experiments with different future sea surface temperature (SST) warming simulated by a range of coupled climate models. They allow us to assess the extent to which uncertainty from current coupled climate model rainfall projections can be attributed to their simulated SST warming. Nine CMIP5 model-simulated global SST warming anomalies have been super-imposed onto the current SSTs simulated by the Australian climate model ACCESS1.3. The ACCESS1.3 SST-forced experiments closely reproduce rainfall means and interannual variations as in its own fully coupled experiments. Although different global SST warming intensities explain well the inter-model difference in global mean precipitation changes, at regional scales the SST influence vary significantly. SST warming explains about 20-25% of the patterns of precipitation changes in each of the four/five models in its rainfall projections over the oceans in the Indo-Pacific domain, but there are also a couple of models in which different SST warming explains little of their precipitation pattern changes. The influence is weaker again for rainfall changes over land. Roughly similar levels of contribution can be attributed to different atmospheric responses to SST warming in these models. The weak SST influence in our study could be due to the experimental setup applied: superimposing different SST warming anomalies onto the same SSTs simulated for current climate by ACCESS1.3 rather than directly using model-simulated past and future SSTs. Similar modelling and analysis from other modelling groups with more carefully designed experiments are needed to tease out uncertainties caused by different SST warming patterns, different SST mean biases and different model physical/dynamical responses to the same underlying SST forcing.

Realism of Indian Summer Monsoon Simulation in a Quarter Degree Global Climate Model

NASA Astrophysics Data System (ADS)

Salunke, P.; Mishra, S. K.; Sahany, S.; Gupta, K.

2017-12-01

This study assesses the fidelity of Indian Summer Monsoon (ISM) simulations using a global model at an ultra-high horizontal resolution (UHR) of 0.25°. The model used was the atmospheric component of the Community Earth System Model version 1.2.0 (CESM 1.2.0) developed at the National Center for Atmospheric Research (NCAR). Precipitation and temperature over the Indian region were analyzed for a wide range of space and time scales to evaluate the fidelity of the model under UHR, with special emphasis on the ISM simulations during the period of June-through-September (JJAS). Comparing the UHR simulations with observed data from the India Meteorological Department (IMD) over the Indian land, it was found that 0.25° resolution significantly improved spatial rainfall patterns over many regions, including the Western Ghats and the South-Eastern peninsula as compared to the standard model resolution. Convective and large-scale rainfall components were analyzed using the European Centre for Medium Range Weather Forecast (ECMWF) Re-Analysis (ERA)-Interim (ERA-I) data and it was found that at 0.25° resolution, there was an overall increase in the large-scale component and an associated decrease in the convective component of rainfall as compared to the standard model resolution. Analysis of the diurnal cycle of rainfall suggests a significant improvement in the phase characteristics simulated by the UHR model as compared to the standard model resolution. Analysis of the annual cycle of rainfall, however, failed to show any significant improvement in the UHR model as compared to the standard version. Surface temperature analysis showed small improvements in the UHR model simulations as compared to the standard version. Thus, one may conclude that there are some significant improvements in the ISM simulations using a 0.25° global model, although there is still plenty of scope for further improvement in certain aspects of the annual cycle of rainfall.

Corn yield and economic return with nitrogen applied through drip tubing

USDA-ARS?s Scientific Manuscript database

A two year project was established to determine corn (Zea mays, L) yield response to subsurface (SSDI) and surface (SDI) drip irrigation systems at various nitrogen fertilizer rates. Nitrogen was applied through the drip system at two nitrogen levels in three split applications. Supplemental dry N ...

Geochemical characteristics of cave drip water respond to ENSO based on a 6-year monitoring work in Yangkou Cave, Southwest China

NASA Astrophysics Data System (ADS)

Chen, Chao-Jun; Li, Ting-Yong

2018-06-01

The scientific explanation of speleothem δ18O in Chinese monsoon region is a greatly debated issue. Modern cave monitoring combined with instrument observation maybe is an essential solution to deal with this issue. During the period from 2011 to 2016, we monitored local precipitation, soil water in three soil profiles, and six drip water sites in Yangkou Cave, which is located in Chongqing City, Southwest China. This article presents measurements about δ18O, δD and Mg/Ca ratios of drip water and compared these geochemical proxies with contemporaneous atmospheric circulations. The main conclusions are: (1) As water migrates from precipitation to soil water to cave drip water, the amplitudes of seasonal variations in δD and δ18O decreased gradually. Due to the existence of complex hydrogeological conditions, the range of variation and the seasonal characteristics of δD and δ18O differ among the drip sites where samples were collected, but the interannual variability is nearly the same. The drip water Mg/Ca ratios are mainly regulated by changes in hydrological conditions in the epikarst zone, with higher values during winter months than that during summer months. (2) When an El Niño event occurs, the Western Pacific Subtropical High (WPSH) is migrated westward, and the production of near-source water vapor from the western Pacific and the South China Sea increases, leading to higher δ18O values in the precipitation and the cave drip water. The drip water Mg/Ca ratios were significantly lower with increased summer precipitation. On the other hand, during La Niña events, the WPSH is migrated eastward, and inputs of water vapor that has traveled greater distances (from the Indian Ocean) become comparatively important, resulting in lower δ18O values in the precipitation and the cave drip water. The drip water Mg/Ca ratios were higher with decreased summer precipitation. In summary, the interannual variability of δ18O in the drip waters of Yangkou Cave reflects changes in water vapor sources caused by atmospheric circulation patterns. Mg/Ca ratios respond to changes of precipitation and CO2 in soil and can be used to reconstruct abnormal drought or flood events.

The Effects of More Extreme Rainfall Patterns on Infiltration and Nutrient Losses in Agricultural Soils

NASA Astrophysics Data System (ADS)

Hess, L.; Basso, B.; Hinckley, E. L. S.; Robertson, G. P.; Matson, P. A.

2015-12-01

In the coming century, the proportion of total rainfall that falls in heavy storm events is expected to increase in many areas, especially in the US Midwest, a major agricultural region. These changes in rainfall patterns may have consequences for hydrologic flow and nutrient losses, especially in agricultural soils, with potentially negative consequences for receiving ground- and surface waters. We used a tracer experiment to examine how more extreme rainfall patterns may affect the movement of water and solutes through an agricultural soil profile in the upper Midwest, and to what extent tillage may moderate these effects. Two rainfall patterns were created with 5m x 5m rainout shelters at the Kellogg Biological Station LTER site in replicated plots with either conventional tillage or no-till management. Control rainfall treatments received water 3x per week, and extreme rainfall treatments received the same total amount of water but once every two weeks, to simulate less frequent but larger storms. In April 2015, potassium bromide (KBr) was added as a conservative tracer of water flow to all plots, and Br- concentrations in soil water at 1.2m depth were measured weekly from April through July. Soil water Br- concentrations increased and peaked more quickly under the extreme rainfall treatment, suggesting increased infiltration and solute transfer to depth compared to soils exposed to control rainfall patterns. Soil water Br- also increased and peaked more quickly in no-till than in conventional tillage treatments, indicating differences in flow paths between management systems. Soil moisture measured every 15 minutes at 10, 40, and 100cm depths corroborates tracer experiment results: rainfall events simulated in extreme rainfall treatments led to large increases in deep soil moisture, while the smaller rainfall events simulated under control conditions did not. Deep soil moisture in no-till treatments also increased sooner after water application as compared to in conventional soils. Our results suggest that exposure to more extreme rainfall patterns will likely increase infiltration depth and nutrient losses in agricultural soils. In particular, soils under no-till management, which leads to development of preferential flow paths, may be particularly vulnerable to vertical nutrient losses.

Rainfall-runoff characteristics and effects of increased urban density on streamflow and infiltration in the eastern part of the San Jacinto River basin, Riverside County, California

USGS Publications Warehouse

Guay, Joel R.

2002-01-01

To better understand the rainfall-runoff characteristics of the eastern part of the San Jacinto River Basin and to estimate the effects of increased urbanization on streamflow, channel infiltration, and land-surface infiltration, a long-term (1950?98) time series of monthly flows in and out of the channels and land surfaces were simulated using the Hydrologic Simulation Program- FORTRAN (HSPF) rainfall-runoff model. Channel and land-surface infiltration includes rainfall or runoff that infiltrates past the zone of evapotranspiration and may become ground-water recharge. The study area encompasses about 256 square miles of the San Jacinto River drainage basin in Riverside County, California. Daily streamflow (for periods with available data between 1950 and 1998), and daily rainfall and evaporation (1950?98) data; monthly reservoir storage data (1961?98); and estimated mean annual reservoir inflow data (for 1974 conditions) were used to calibrate the rainfall-runoff model. Measured and simulated mean annual streamflows for the San Jacinto River near San Jacinto streamflow-gaging station (North-South Fork subbasin) for 1950?91 and 1997?98 were 14,000 and 14,200 acre-feet, respectively, a difference of 1.4 percent. The standard error of the mean for measured and simulated annual streamflow in the North-South Fork subbasin was 3,520 and 3,160 acre-feet, respectively. Measured and simulated mean annual streamflows for the Bautista Creek streamflow-gaging station (Bautista Creek subbasin) for 1950?98 were 980 acre-feet and 991 acre-feet, respectively, a difference of 1.1 percent. The standard error of the mean for measured and simulated annual streamflow in the Bautista Creek subbasin was 299 and 217 acre-feet, respectively. Measured and simulated annual streamflows for the San Jacinto River above State Street near San Jacinto streamflow-gaging station (Poppet subbasin) for 1998 were 23,400 and 23,500 acre-feet, respectively, a difference of 0.4 percent. The simulated mean annual streamflow for the State Street gaging station at the outlet of the study basin and the simulated mean annual basin infiltration (combined infiltration from all the channels and land surfaces) were 8,720 and 41,600 acre-feet, respectively, for water years 1950-98. Simulated annual streamflow at the State Street gaging station ranged from 16.8 acre-feet in water year 1961 to 70,400 acre-feet in water year 1993, and simulated basin infiltration ranged from 2,770 acre-feet in water year 1961 to 149,000 acre-feet in water year 1983.The effects of increased urbanization on the hydrology of the study basin were evaluated by increasing the size of the effective impervious and non-effective impervious urban areas simulated in the calibrated rainfall-runoff model by 50 and 100 percent, respectively. The rainfall-runoff model simulated a long-term time series of monthly flows in and out of the channels and land surfaces using daily rainfall and potential evaporation data for water years 1950?98. Increasing the effective impervious and non-effective impervious urban areas by 100 percent resulted in a 5-percent increase in simulated mean annual streamflow at the State Street gaging station, and a 2.2-percent increase in simulated basin infiltration. Results of a frequency analysis of the simulated annual streamflow at the State Street gaging station showed that when effective impervious and non-effective impervious areas were increased 100 percent, simulated annual streamflow increased about 100 percent for low-flow conditions and was unchanged for high-flow conditions. The simulated increase in streamflow at the State Street gaging station potentially could infiltrate along the stream channel further downstream, outside of the model area.

Characterizing Satellite Rainfall Errors based on Land Use and Land Cover and Tracing Error Source in Hydrologic Model Simulation

NASA Astrophysics Data System (ADS)

Gebregiorgis, A. S.; Peters-Lidard, C. D.; Tian, Y.; Hossain, F.

2011-12-01

Hydrologic modeling has benefited from operational production of high resolution satellite rainfall products. The global coverage, near-real time availability, spatial and temporal sampling resolutions have advanced the application of physically based semi-distributed and distributed hydrologic models for wide range of environmental decision making processes. Despite these successes, the existence of uncertainties due to indirect way of satellite rainfall estimates and hydrologic models themselves remain a challenge in making meaningful and more evocative predictions. This study comprises breaking down of total satellite rainfall error into three independent components (hit bias, missed precipitation and false alarm), characterizing them as function of land use and land cover (LULC), and tracing back the source of simulated soil moisture and runoff error in physically based distributed hydrologic model. Here, we asked "on what way the three independent total bias components, hit bias, missed, and false precipitation, affect the estimation of soil moisture and runoff in physically based hydrologic models?" To understand the clear picture of the outlined question above, we implemented a systematic approach by characterizing and decomposing the total satellite rainfall error as a function of land use and land cover in Mississippi basin. This will help us to understand the major source of soil moisture and runoff errors in hydrologic model simulation and trace back the information to algorithm development and sensor type which ultimately helps to improve algorithms better and will improve application and data assimilation in future for GPM. For forest and woodland and human land use system, the soil moisture was mainly dictated by the total bias for 3B42-RT, CMORPH, and PERSIANN products. On the other side, runoff error was largely dominated by hit bias than the total bias. This difference occurred due to the presence of missed precipitation which is a major contributor to the total bias both during the summer and winter seasons. Missed precipitation, most likely light rain and rain over snow cover, has significant effect on soil moisture and are less capable of producing runoff that results runoff dependency on the hit bias only.

Water Conservation Education with a Rainfall Simulator.

ERIC Educational Resources Information Center

Kok, Hans; Kessen, Shelly

1997-01-01

Describes a program in which a rainfall simulator was used to promote water conservation by showing water infiltration, water runoff, and soil erosion. The demonstrations provided a good background for the discussion of issues such as water conservation, crop rotation, and conservation tillage practices. The program raised awareness of…

Efficient Meshfree Large Deformation Simulation of Rainfall Induced Soil Slope Failure

NASA Astrophysics Data System (ADS)

Wang, Dongdong; Li, Ling

2010-05-01

An efficient Lagrangian Galerkin meshfree framework is presented for large deformation simulation of rainfall-induced soil slope failure. Detailed coupled soil-rainfall seepage equations are given for the proposed formulation. This nonlinear meshfree formulation is featured by the Lagrangian stabilized conforming nodal integration method where the low cost nature of nodal integration approach is kept and at the same time the numerical stability is maintained. The initiation and evolution of progressive failure in the soil slope is modeled by the coupled constitutive equations of isotropic damage and Drucker-Prager pressure-dependent plasticity. The gradient smoothing in the stabilized conforming integration also serves as a non-local regularization of material instability and consequently the present method is capable of effectively capture the shear band failure. The efficacy of the present method is demonstrated by simulating the rainfall-induced failure of two typical soil slopes.

Aerosol-induced changes in summer rainfall and circulation in the Australasian region: a study using single-forcing climate simulations

NASA Astrophysics Data System (ADS)

Rotstayn, L. D.; Jeffrey, S. J.; Collier, M. A.; Dravitzki, S. M.; Hirst, A. C.; Syktus, J. I.; Wong, K. K.

2012-02-01

We use a coupled atmosphere-ocean global climate model (CSIRO-Mk3.6) to investigate the roles of different forcing agents as drivers of summer rainfall trends in the Australasian region. Our results suggest that anthropogenic aerosols have contributed to the observed multi-decadal rainfall increase over north-western Australia. As part of the Coupled Model Intercomparison Project Phase 5 (CMIP5), we performed multiple 10-member ensembles of historical climate change, which are analysed for the period 1951-2010. The historical runs include ensembles driven by "all forcings" (HIST), all forcings except anthropogenic aerosols (NO_AA) and forcing only from long-lived greenhouse gases (GHGAS). Anthropogenic aerosol-induced effects in a warming climate are calculated from the difference of HIST minus NO_AA. We also compare a 10-member 21st century ensemble driven by Representative Concentration Pathway 4.5 (RCP4.5). Simulated aerosol-induced rainfall trends over the Indo-Pacific region for austral summer and boreal summer show a distinct contrast. In boreal summer, there is a southward shift of equatorial rainfall, consistent with the idea that anthropogenic aerosols have suppressed Asian monsoonal rainfall, and caused a southward shift of the local Hadley circulation. In austral summer, the aerosol-induced response more closely resembles a westward shift and strengthening of the upward branch of the Walker circulation, rather than a coherent southward shift of regional tropical rainfall. Thus the mechanism by which anthropogenic aerosols may affect Australian summer rainfall is unclear. Focusing on summer rainfall trends over north-western Australia (NWA), we find that CSIRO-Mk3.6 simulates a strong rainfall decrease in RCP4.5, whereas simulated trends in HIST are weak and insignificant during 1951-2010. The weak rainfall trends in HIST are due to compensating effects of different forcing agents: there is a significant decrease in GHGAS, offset by an aerosol-induced increase in HIST minus NO_AA. However, the magnitude of the observed NWA rainfall trend is not captured by the ensemble mean of HIST minus NO_AA, or by 440 unforced 60-yr trends calculated from a 500-yr pre-industrial control run. This suggests that the observed trend includes both a forced and unforced component. We investigate the mechanism of simulated and observed NWA rainfall changes by exploring changes in circulation over the Indo-Pacific region. The key circulation feature associated with the rainfall increase is a lower-tropospheric cyclonic circulation trend off the coast of NWA. In the model, it induces moisture convergence and upward motion over NWA. The cyclonic anomaly is present in trends calculated from HIST minus NO_AA and from reanalyses. Further analysis suggests that the cyclonic circulation trend in HIST minus NO_AA may be initiated as a Rossby wave response to positive convective heating anomalies south of the equator during November, when the aerosol-induced response of the model over the Indian Ocean still resembles that in boreal summer (i.e. a southward shift of equatorial rainfall). The aerosol-induced enhancement of the cyclonic circulation and associated monsoonal rainfall becomes progressively stronger from December to March, suggesting that there is a positive feedback between the source of latent heat (the Australian monsoon) and the cyclonic circulation. CSIRO-Mk3.6 indicates that anthropogenic aerosols may have masked greenhouse gas-induced changes in rainfall over NWA and in circulation over the wider Indo-Pacific region: simulated trends in RCP4.5 resemble a stronger version of those in GHGAS, and are very different from those in HIST. Further research is needed to better understand the mechanisms and the extent to which these findings are model-dependent.

TRMM- and GPM-based precipitation analysis and modelling in the Tropical Andes

NASA Astrophysics Data System (ADS)

Manz, Bastian; Buytaert, Wouter; Zulkafli, Zed; Onof, Christian

2016-04-01

Despite wide-spread applications of satellite-based precipitation products (SPPs) throughout the TRMM-era, the scarcity of ground-based in-situ data (high density gauge networks, rainfall radar) in many hydro-meteorologically important regions, such as tropical mountain environments, has limited our ability to evaluate both SPPs and individual satellite-based sensors as well as accurately model or merge rainfall at high spatial resolutions, particularly with respect to extremes. This has restricted both the understanding of sensor behaviour and performance controls in such regions as well as the accuracy of precipitation estimates and respective hydrological applications ranging from water resources management to early warning systems. Here we report on our recent research into precipitation analysis and modelling using various TRMM and GPM products (2A25, 3B42 and IMERG) in the tropical Andes. In an initial study, 78 high-frequency (10-min) recording gauges in Colombia and Ecuador are used to generate a ground-based validation dataset for evaluation of instantaneous TRMM Precipitation Radar (TPR) overpasses from the 2A25 product. Detection ability, precipitation time-series, empirical distributions and statistical moments are evaluated with respect to regional climatological differences, seasonal behaviour, rainfall types and detection thresholds. Results confirmed previous findings from extra-tropical regions of over-estimation of low rainfall intensities and under-estimation of the highest 10% of rainfall intensities by the TPR. However, in spite of evident regionalised performance differences as a function of local climatological regimes, the TPR provides an accurate estimate of climatological annual and seasonal rainfall means. On this basis, high-resolution (5 km) climatological maps are derived for the entire tropical Andes. The second objective of this work is to improve the local precipitation estimation accuracy and representation of spatial patterns of extreme rainfall probabilities over the region. For this purpose, an ensemble of high-resolution rainfall fields is generated by stochastic simulation using space-time averaged, coarse-scale (daily, 0.25°) satellite-based rainfall inputs (TRMM 3B42/ -RT) and the high-resolution climatological information derived from the TPR as spatial disaggregation proxies. For evaluation and merging, gridded ground-based rainfall fields are generated from gauge data using sequential simulation. Satellite and ground-based ensembles are subsequently merged using an inverse error weighting scheme. The model was tested over a case study in the Colombian Andes with optional coarse-scale bias correction prior to disaggregation and merging. The resulting outputs were assessed in the context of Generalized Extreme Value theory and showed improved estimation of extreme rainfall probabilities compared to the original TMPA inputs. Initial findings using GPM-IMERG inputs are also presented.

Modeling rainfall-runoff relationship using multivariate GARCH model

NASA Astrophysics Data System (ADS)

Modarres, R.; Ouarda, T. B. M. J.

2013-08-01

The traditional hydrologic time series approaches are used for modeling, simulating and forecasting conditional mean of hydrologic variables but neglect their time varying variance or the second order moment. This paper introduces the multivariate Generalized Autoregressive Conditional Heteroscedasticity (MGARCH) modeling approach to show how the variance-covariance relationship between hydrologic variables varies in time. These approaches are also useful to estimate the dynamic conditional correlation between hydrologic variables. To illustrate the novelty and usefulness of MGARCH models in hydrology, two major types of MGARCH models, the bivariate diagonal VECH and constant conditional correlation (CCC) models are applied to show the variance-covariance structure and cdynamic correlation in a rainfall-runoff process. The bivariate diagonal VECH-GARCH(1,1) and CCC-GARCH(1,1) models indicated both short-run and long-run persistency in the conditional variance-covariance matrix of the rainfall-runoff process. The conditional variance of rainfall appears to have a stronger persistency, especially long-run persistency, than the conditional variance of streamflow which shows a short-lived drastic increasing pattern and a stronger short-run persistency. The conditional covariance and conditional correlation coefficients have different features for each bivariate rainfall-runoff process with different degrees of stationarity and dynamic nonlinearity. The spatial and temporal pattern of variance-covariance features may reflect the signature of different physical and hydrological variables such as drainage area, topography, soil moisture and ground water fluctuations on the strength, stationarity and nonlinearity of the conditional variance-covariance for a rainfall-runoff process.

Climate change induced rainfall patterns affect wheat productivity and agroecosystem functioning dependent on soil types

NASA Astrophysics Data System (ADS)

Tabi Tataw, James; Baier, Fabian; Krottenthaler, Florian; Pachler, Bernadette; Schwaiger, Elisabeth; Whylidal, Stefan; Formayer, Herbert; Hösch, Johannes; Baumgarten, Andreas; Zaller, Johann G.

2014-05-01

Wheat is a crop of global importance supplying more than half of the world's population with carbohydrates. We examined, whether climate change induced rainfall patterns towards less frequent but heavier events alter wheat agroecosystem productivity and functioning under three different soil types. Therefore, in a full-factorial experiment Triticum aestivum L. was cultivated in 3 m2 lysimeter plots containing the soil types sandy calcaric phaeozem, gleyic phaeozem or calcic chernozem. Prognosticated rainfall patterns based on regionalised climate change model calculations were compared with current long-term rainfall patterns; each treatment combination was replicated three times. Future rainfall patterns significantly reduced wheat growth and yield, reduced the leaf area index, accelerated crop development, reduced arbuscular mycorrhizal fungi colonisation of roots, increased weed density and the stable carbon isotope signature (δ13C) of both old and young wheat leaves. Different soil types affected wheat growth and yield, ecosystem root production as well as weed abundance and biomass. The interaction between climate and soil type was significant only for the harvest index. Our results suggest that even slight changes in rainfall patterns can significantly affect the functioning of wheat agroecosystems. These rainfall effects seemed to be little influenced by soil types suggesting more general impacts of climate change across different soil types. Wheat production under future conditions will likely become more challenging as further concurrent climate change factors become prevalent.

Western Pacific emergent constraint lowers projected increase in Indian summer monsoon rainfall

NASA Astrophysics Data System (ADS)

Li, Gen; Xie, Shang-Ping; He, Chao; Chen, Zesheng

2017-10-01

The agrarian-based socioeconomic livelihood of densely populated South Asian countries is vulnerable to modest changes in Indian summer monsoon (ISM) rainfall. How the ISM rainfall will evolve is a question of broad scientific and socioeconomic importance. In response to increased greenhouse gas (GHG) forcing, climate models commonly project an increase in ISM rainfall. This wetter ISM projection, however, does not consider large model errors in both the mean state and ocean warming pattern. Here we identify a relationship between biases in simulated present climate and future ISM projections in a multi-model ensemble: models with excessive present-day precipitation over the tropical western Pacific tend to project a larger increase in ISM rainfall under GHG forcing because of too strong a negative cloud-radiation feedback on sea surface temperature. The excessive negative feedback suppresses the local ocean surface warming, strengthening ISM rainfall projections via atmospheric circulation. We calibrate the ISM rainfall projections using this `present-future relationship’ and observed western Pacific precipitation. The correction reduces by about 50% of the projected rainfall increase over the broad ISM region. Our study identifies an improved simulation of western Pacific convection as a priority for reliable ISM projections.

Convective and microphysics parameterization impact on simulating heavy rainfall in Semarang (case study on February 12th, 2015)

NASA Astrophysics Data System (ADS)

Faridatussafura, Nurzaka; Wandala, Agie

2018-05-01

The meteorological model WRF-ARW version 3.8.1 is used for simulating the heavy rainfall in Semarang that occurred on February 12th, 2015. Two different convective schemes and two different microphysics scheme in a nested configuration were chosen. The sensitivity of those schemes in capturing the extreme weather event has been tested. GFS data were used for the initial and boundary condition. Verification on the twenty-four hours accumulated rainfall using GSMaPsatellite data shows that Kain-Fritsch convective scheme and Lin microphysics scheme is the best combination scheme among the others. The combination also gives the highest success ratio value in placing high intensity rainfall area. Based on the ROC diagram, KF-Lin shows the best performance in detecting high intensity rainfall. However, the combination still has high bias value.

Relating Convective and Stratiform Rain to Latent Heating

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Lang, Stephen; Zeng, Xiping; Shige, Shoichi; Takayabu, Yukari

2010-01-01

The relationship among surface rainfall, its intensity, and its associated stratiform amount is established by examining observed precipitation data from the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR). The results show that for moderate-high stratiform fractions, rain probabilities are strongly skewed toward light rain intensities. For convective-type rain, the peak probability of occurrence shifts to higher intensities but is still significantly skewed toward weaker rain rates. The main differences between the distributions for oceanic and continental rain are for heavily convective rain. The peak occurrence, as well as the tail of the distribution containing the extreme events, is shifted to higher intensities for continental rain. For rainy areas sampled at 0.58 horizontal resolution, the occurrence of conditional rain rates over 100 mm/day is significantly higher over land. Distributions of rain intensity versus stratiform fraction for simulated precipitation data obtained from cloud-resolving model (CRM) simulations are quite similar to those from the satellite, providing a basis for mapping simulated cloud quantities to the satellite observations. An improved convective-stratiform heating (CSH) algorithm is developed based on two sources of information: gridded rainfall quantities (i.e., the conditional intensity and the stratiform fraction) observed from the TRMM PR and synthetic cloud process data (i.e., latent heating, eddy heat flux convergence, and radiative heating/cooling) obtained from CRM simulations of convective cloud systems. The new CSH algorithm-derived heating has a noticeably different heating structure over both ocean and land regions compared to the previous CSH algorithm. Major differences between the new and old algorithms include a significant increase in the amount of low- and midlevel heating, a downward emphasis in the level of maximum cloud heating by about 1 km, and a larger variance between land and ocean in the new CSH algorithm.

Rainfall and sheet power model for interrill erosion in steep slope

NASA Astrophysics Data System (ADS)

Shin, Seung Sook; Deog Park, Sand; Nam, Myeong Jun

2015-04-01

The two-phase process of interrill erosion consist of the splash and detachment of individual particles from soil mass by impact of raindrops and the transport by erosive running water. Most experimental results showed that the effect of interaction between rainfall impact and surface runoff increases soil erosion in low or gentle slope. Especially, the combination of rain splash and sheet flow is the dominant runoff and erosion mechanism occurring on most steep hillslopes. In this study, a rainfall simulation was conducted to evaluate interrill erosion in steep slope with cover or non-cover. The kinetic energy of raindrops of rainfall simulator was measured by disdrometer used to measure the drop size distribution and velocity of falling raindrops and showed about 0.563 rate of that calculated from empirical equation between rainfall kinetic energy and rainfall intensity. Surface and subsurface runoff and sediment yield depended on rainfall intensity, gradient of slope, and existence of cover. Sediment from steep plots under rainfall simulator is greatly reduced by existence of the strip cover that the kinetic energy of raindrop approximates to zero. Soil erosion in steep slope with non-cover was nearly 4.93 times of that measured in plots with strip cover although runoff was only 1.82 times. The equation of a rainfall and sheet power was used to evaluate sediment yields in steep slope with cover or non-cover. The power model successfully explained physical processes for interrill erosion that combination of raindrop impact and sheet flow increases greatly soil erosion in steep slope. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(No. 2013R1A1A3011962).

An assessment of the feasibility of the use of satellite-only rainfall estimates for the hydrological monitoring in central Italy

NASA Astrophysics Data System (ADS)

Campo, Lorenzo; Caparrini, Francesca

2013-04-01

The need for accurate distributed hydrological modelling has constantly increased in last years for several purposes: agricultural applications, water resources management, hydrological balance at watershed scale, floods forecast. The main input for the hydrological numerical models is rainfall data that present, at the same time, a large availability of measures (in gauged regions, with respect to other micro-meteorological variables) and the most complex spatial patterns. While also in presence of densely gauged watersheds the spatial interpolation of the rainfall is a non-trivial problem, due to the spatial intermittence of the variable (especially at finer temporal scales), ungauged regions need an alternative source of rainfall data in order to perform the hydrological modelling. Such source can be constituted by the satellite-estimated rainfall fields, with reference to both geostationary and polar-orbit platforms. In this work the rainfall product obtained by the Aqua-AIRS sensor were used in order to assess the feasibility of the use of satellite-based rainfall as input for distributed hydrological modelling. The MOBIDIC (MOdello di BIlancio Distribuito e Continuo) model, developed at the Department of civil and Environmental Engineering of the University of Florence and operationally used by Tuscany Region and Umbria Region for flood prediction and management, was used for the experiments. In particular three experiments were carried on: a) hydrological simulation with the use of rain-gauges data, b) simulation with the use of satellite-only rainfall estimates, c) simulation with the combined use of the two sources of data in order to obtain an optimal estimate of the actual rainfall fields. The domain of the study was the central Italy. Several critical events occurred in the area were analyzed. A discussion of the results is provided.

Challenges in predicting and simulating summer rainfall in the eastern China

NASA Astrophysics Data System (ADS)

Liang, Ping; Hu, Zeng-Zhen; Liu, Yunyun; Yuan, Xing; Li, Xiaofan; Jiang, Xingwen

2018-05-01

To demonstrate the challenge of summer rainfall prediction and simulation in the eastern China, in this work, we examine the skill of the state-of-the-art climate models, evaluate the impact of sea surface temperature (SST) on forecast skill and estimate the predictability by using perfect model approach. The challenge is further demonstrated by assessing the ability of various reanalyses in capturing the observed summer rainfall variability in the eastern China and by examining the biases in reanalyses and in a climate model. Summer rainfall forecasts (hindcasts) initiated in May from eight seasonal forecast systems have low forecast skill with linear correlation of - 0.3 to 0.5 with observations. The low forecast skill is consistent with the low perfect model score ( 0.1-0.3) of atmospheric model forced by observed SST, due to the fact that external forcing (SST) may play a secondary role in the summer rainfall variation in the eastern China. This is a common feature for the climate variation over the middle and high latitude lands, where the internal dynamical processes dominate the rainfall variation in the eastern China and lead to low predictability, and external forcing (such as SST) plays a secondary role and is associated with predictable fraction. Even the reanalysis rainfall has some remarkable disagreements with the observation. Statistically, more than 20% of the observed variance is not captured by the mean of six reanalyses. Among the reanalyses, JRA55 stands out as the most reliable one. In addition, the reanalyses and climate model have pronounced biases in simulating the mean rainfall. These defaults mean an additional challenge in predicting the summer rainfall variability in the eastern China that has low predictability in nature.

Robust effects of cloud superparameterization on simulated daily rainfall intensity statistics across multiple versions of the Community Earth System Model

DOE PAGES

Kooperman, Gabriel J.; Pritchard, Michael S.; Burt, Melissa A.; ...

2016-02-01

This study evaluates several important statistics of daily rainfall based on frequency and amount distributions as simulated by a global climate model whose precipitation does not depend on convective parameterization—Super-Parameterized Community Atmosphere Model (SPCAM). Three superparameterized and conventional versions of CAM, coupled within the Community Earth System Model (CESM1 and CCSM4), are compared against two modern rainfall products (GPCP 1DD and TRMM 3B42) to discriminate robust effects of superparameterization that emerge across multiple versions. The geographic pattern of annual-mean rainfall is mostly insensitive to superparameterization, with only slight improvements in the double-ITCZ bias. However, unfolding intensity distributions reveal several improvementsmore » in the character of rainfall simulated by SPCAM. The rainfall rate that delivers the most accumulated rain (i.e., amount mode) is systematically too weak in all versions of CAM relative to TRMM 3B42 and does not improve with horizontal resolution. It is improved by superparameterization though, with higher modes in regions of tropical wave, Madden-Julian Oscillation, and monsoon activity. Superparameterization produces better representations of extreme rates compared to TRMM 3B42, without sensitivity to horizontal resolution seen in CAM. SPCAM produces more dry days over land and fewer over the ocean. Updates to CAM’s low cloud parameterizations have narrowed the frequency peak of light rain, converging toward SPCAM. Poleward of 50°, where more rainfall is produced by resolved-scale processes in CAM, few differences discriminate the rainfall properties of the two models. Lastly, these results are discussed in light of their implication for future rainfall changes in response to climate forcing.« less

Experimental Exploration on Rainfall-induced Mass Re-mobilization after Giant Earthquake: A case study in Wenchuan earthquake hit region, China

NASA Astrophysics Data System (ADS)

Yang, Zongji; Bogaard, Thom. A.; Qiao, Jianping; Jiang, Yuanjun

2015-04-01

Prevention and mitigation of rainfall induced geological hazards after the Ms=8 Wenchuan earthquake on May 12th, 2008 were gained more significance for the rebuild of earthquake hit regions in China. After the Wenchuan earthquake, there were thousands of slopes failure, which were much more susceptible to subsequent heavy rainfall and many even transformed into potential debris flows. An typical example can be found in the catastrophic disaster occurred in Zhongxing County, Chengdu City on 10th July, 2013 in which the unknown fractured slope up the mountain was triggered by a downpour and transformed into subsequent debris flow which wiped the community downstream, about 200 victims were reported in that tragic event. The transform patterns of rainfall-induced mass re-mobilization was categorized into three major type as the erosion of fractured slopes, initiate on loosen deposit and outbreak of landslide (debris flow) dams according to vast field investigation in the earthquake hit region. Despite the widespread and hidden characters,the complexity of the process also demonstrated in the transforms of the mass re-mobilized by the erosion of both gravity and streams in the small watersheds which have never been reported before the giant Wenchuan Earthquake in many regions. As a result, an increasing number of questions for disaster relief and mitigation were proposed including the threshold of early warning and measurement of the volume for the design of mitigation measures on rainfall-induced mass re-mobilization in debris flow gullies. This study is aimed for answer the essential questions about the threshold and amount of mass initiation triggered by the subsequent rainfall in post earthquake time. In this study, experimental tests were carried out for simulating the failure of the rainfall-induced mass re-mobilization in respectively in a natural co-seismic fractured slope outside and the debris flow simulation platform inside the laboratory. A natural fractured slope was selected to conduct the field experimental test,after the field experimental test, the correlation of rainfall parameters, deformation criterion and water content as well as the failure volume of gravity erosion was investigated. In addition, the loosen mass re-mobilized by the stream was also simulated by the model experiment by which the correlation of rainfall thresholds, and the initial volume of mass triggered by the flow was analyzed. Thus, the threshold and volume measurement model for the initiation of mass re-mobilization were proposed by means of this experimental research. Despite of the fact that the simplicity of the model derived from experimental and empirical method and some drawbacks connected with the uncertainty and complexity of the geological phenomenon, the proposed method have contributed a lot in application for the early warning and prevention of mass transformed debris flows in earthquake hit region, China.

Hydraulic properties for interrill erosion on steep slopes using a portable rainfall simulator

NASA Astrophysics Data System (ADS)

Shin, Seung Sook; Hwang, Yoonhee; Deog Park, Sang; Yun, Minu; Park, Sangyeon

2017-04-01

The hydraulic parameters for sheet flow on steep slopes have been not frequently measured because the shallow flow depth and slow flow velocity are difficult to measure. In this study hydraulic values of sheet flow were analyzed to evaluate interrill erosion on steep slopes. A portable rainfall simulator was used to conduct interrill erosion test. The kinetic energy of rainfall simulator was obtained by disdrometer being capable of measuring the drop size distribution and velocity of falling raindrops. The sheet flow velocity was determined by the taken time for a dye transferring fixed points using video images. Surface runoff discharge and sediment yield increased with increase of rainfall intensity and kinetic energy and slope steepness. Especially sediment yield was strongly correlated with sheet flow velocity. The maximum velocity of sheet flow was 2.3cm/s under rainfall intensity of 126.8mm/h and slope steepness of 53.2%. The sheet flow was laminar and subcritical flow as the flow Reynolds number and Froude number are respectively the ranges of 10 22 and 0.05 0.25. The roughness coefficient (Manning's n) for sheet flow on steep slopes was relatively large compared to them on the gentle slope. Keywords: Sheet flow velocity; Rainfall simulator; Interrill erosion; Steep slope This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP) (No. 2015R1C1A2A01055469).

Linkage between canopy water storage and drop size distributions of leaf drips

NASA Astrophysics Data System (ADS)

Nanko, Kazuki; Watanabe, Ai; Hotta, Norifumi; Suzuki, Masakazu

2013-04-01

Differences in drop size distribution (DSD) of leaf drips among tree species have been estimated and physically interpreted to clarify the leaf drip generation process. Leaf drip generation experiments for nine species were conducted in an indoor location without foliage vibration using an automatic mist spray. Broad-leaved species produced a similar DSD among species whose leaves had a matte surface and a second similar DSD among species whose leaves had a coated surface. The matte broad leaves produced a larger and wider range of DSDs than the coated broad leaves. Coated coniferous needles had a wider range of DSDs than the coated broad leaves and different DSDs were observed for different species. The species with shorter dense needles generated a larger DSD. The leaf drip diameter was calculated through the estimation of a state of equilibrium of a hanging drop on the leaves based on physical theory. The calculations indicated that the maximum diameter of leaf drips was determined by the contact angle, and the range of DSDs was determined by the variation in contact length and the contact diameter at the hanging points. The results revealed that leaf drip DSD changed due to variations in leaf hydrophobicity, leaf roughness, leaf geometry and leaf inclination among the different tree species. This study allows the modelization of throughfall DSD. Furthermore, it indicates the possibility of interpreting canopy water processes from canopy water storage to drainage through the contact angle and leaf drip DSD. The part of this study is published in Nanko et al. (2013, Agric. Forest. Meteorol. 169, 74-84).

Vallerani Micro-Catchment Infiltration Dynamics and Erosion from Simulated Rainfall and Concentrated Flow

NASA Astrophysics Data System (ADS)

Founds, M. J.; McGwire, K.; Weltz, M.

2017-12-01

Critical research gaps in rangeland hydrology still exist on the impact of conservation practices on erosion and subsequent mobilization of dissolved solids to streams. This study develops the scientific foundation necessary to better understand how a restoration strategy using a Vallerani Plow can be optimized to minimize erosion from rainfall impact and concentrated flow. Use of the Vallerani system has been proposed for use in the Upper Colorado River Basin (UCRB), where rapidly eroding rangelands contribute high salt loads to the Colorado River at a significant economic cost. The poster presentation will document the findings from a series of physical rainfall and concentrated flow simulations taking place at an experimental site northeast of Reno, NV in early August. A Walnut Gulch Rainfall simulator is used to apply variable intensity and duration rainfall events to micro-catchment structures created by the Vallerani Plow. The erosion and deposition caused by simulated rainfall will be captured from multi-angle photography using structure from motion (SFM) to create sub-centimeter 3-D models between each rainfall event. A rill-simulator also will be used to apply large volumes of concentrated flow to Vallerani micro-catchments, testing the point at which their infiltration capacity is exceeded and micro-catchments are overtopped. This information is important to adequately space structures on a given hillslope so that chances of failure are minimized. Measurements of saturated hydraulic conductivity and sorptivity from a Guelph Permeameter will be compared to the experimental results in order to develop an efficient method for surveying new terrain for treatment with the Vallerani plow. The effect of micro-catchments on surface flow and erosion will eventually be incorporated into the process-based Rangeland Hydrology and Erosion Model (RHEM) to create a tool that provides decision makers with quantitative estimates of potential reductions in erosion when using the Vallerani System to restore highly erosive rangelands within the UCRB.

The extent of wind-induced undercatch in the UK winter storms of 2015

NASA Astrophysics Data System (ADS)

Pollock, Michael; Colli, Matteo; Stagnaro, Mattia; Quinn, Paul; Dutton, Mark; O'Donnell, Greg; Wilkinson, Mark; Black, Andrew; O'Connell, Enda; Lanza, Luca

2016-04-01

The most widely used device for measuring rainfall is the rain gauge, of which the tipping bucket (TBR) is the most prevalent type. Rain gauges are considered by many to be the most accurate method currently available. The data they produce are used in flood-forecasting and flood risk management, water resource management, hydrological modelling and evaluating impacts on climate change; to name but a few. Rain gauges may provide the most accurate measurement of rainfall at a point in space and time, but they are subject to errors - and some gauges are more prone than others. The most significant error is the 'wind-induced undercatch'. This is caused by the gauge itself contributing to an acceleration of the wind speed near the orifice, which disturbs and distorts the airflow. The trajectories of precipitation particles are affected, resulting in an undercatch. Results from Computational Fluid Dynamics (CFD) simulations, presented herein, describe in detail the physical processes contributing to this. High resolution field measurements of rainfall and wind are collected at four field research stations in the UK. Each site is equipped with juxtaposed rain gauges with different funnel profiles, in addition to a WMO reference pit rain gauge measurement. These data describe the rainfall measurement uncertainty. The sites were selected to represent the prevalent rainfall regimes observed in the UK. Two research stations are on the west coast; which is prone to frontal weather systems and storms swept in from the Atlantic, often enhanced by orography. Two are located in the east. Rural lowland and upland areas are represented, both in the west and the east. Urban sites will also have significant undercatch problems but are outside the scope of this study. Data from the four research stations are analysed for the 2015 winter storms which caused devastating flooding in the west of the UK, particularly Cumbria and the Scottish Borders, where two of the sites are located. An assessment of the effect of wind on the rainfall catch during these large storm events is presented for each research station. Based on a reference pit rain gauge, the undercatch for these events is calculated. The difference in rainfall catch between several types of rain gauge mounted at variable heights is also investigated. This work aims to demonstrate the importance of improving the accuracy of rainfall measurements, and to emphasise the need to provide an assessment of the measurement uncertainty. A knowledge gap exists in the understanding of precisely how physical phenomena are contributing to wind-induced undercatch. For instance, a priori, the effect of the wind on the rainfall catch will change depending upon the dimensions of the rain droplets. Rainfall 'type' and rainfall intensity may be able to inform corrections, but rigorous multi-variate statistical analysis of high resolution measurements will be key to the success of these procedures. As the spatio-temporal distribution of rainfall can be highly variable, and each measurement location is different; it is a challenging undertaking to understand and pin down the fundamental processes responsible for the wind-induced undercatch.

Regional climate modeling over the Maritime Continent: Assessment of RegCM3-BATS1e and RegCM3-IBIS

NASA Astrophysics Data System (ADS)

Gianotti, R. L.; Zhang, D.; Eltahir, E. A.

2010-12-01

Despite its importance to global rainfall and circulation processes, the Maritime Continent remains a region that is poorly simulated by climate models. Relatively few studies have been undertaken using a model with fine enough resolution to capture the small-scale spatial heterogeneity of this region and associated land-atmosphere interactions. These studies have shown that even regional climate models (RCMs) struggle to reproduce the climate of this region, particularly the diurnal cycle of rainfall. This study builds on previous work by undertaking a more thorough evaluation of RCM performance in simulating the timing and intensity of rainfall over the Maritime Continent, with identification of major sources of error. An assessment was conducted of the Regional Climate Model Version 3 (RegCM3) used in a coupled system with two land surface schemes: Biosphere Atmosphere Transfer System Version 1e (BATS1e) and Integrated Biosphere Simulator (IBIS). The model’s performance in simulating precipitation was evaluated against the 3-hourly TRMM 3B42 product, with some validation provided of this TRMM product against ground station meteorological data. It is found that the model suffers from three major errors in the rainfall histogram: underestimation of the frequency of dry periods, overestimation of the frequency of low intensity rainfall, and underestimation of the frequency of high intensity rainfall. Additionally, the model shows error in the timing of the diurnal rainfall peak, particularly over land surfaces. These four errors were largely insensitive to the choice of boundary conditions, convective parameterization scheme or land surface scheme. The presence of a wet or dry bias in the simulated volumes of rainfall was, however, dependent on the choice of convection scheme and boundary conditions. This study also showed that the coupled model system has significant error in overestimation of latent heat flux and evapotranspiration from the land surface, and specifically overestimation of interception loss with concurrent underestimation of transpiration, irrespective of the land surface scheme used. Discussion of the origin of these errors is provided, with some suggestions for improvement.

South-France caves monitoring : present day cave air dynamics characterization,paleoclimatic and archaeological interests

NASA Astrophysics Data System (ADS)

Bourges, F.; Genty, D.; Genthon, P.; Mangin, A.; D'Hulst, D.

2012-04-01

Cave climatic environment survey covers different sort of analyses on air and water, and has various interests from the conservation of prehistoric caves to the study of paleoclimates. Depending on the purpose, the cave monitoring can be entirely automatic or combine both automatic and manual data acquisitions. Apparatus are adapted to cave environment to measure specific parameters (i.e. drip rate, air humidity, CO2) and during the long-term monitorings, several generations of techniques have been used. We present here examples of cave monitoring (1996 →) from South-France: Chauvet, Orgnac (Ardèche), Esparros (Hautes-Pyrénées) and Villars (Dordogne). In all these sites, we obtained among the longest series of climatic parameters of inside the caves, coupled sometimes with geochemical and isotopic analyses on air and seepage water, which allow to better understand cave air circulation behaviour and their sensitivity to the external climatic and environmental variations. High precision temperature measurements in Orgnac and Chauvet caves, coupled with pCO2 and radon analyses, allowed the reconstruction of seasonal air circulation patterns in each cave. While the Chauvet and Esparros caves are quite confined environments with temperature changes mainly controlled by air pressure variations, the Orgnac cave, like most caves, shows a well marked summer/winter regime alternation. Quantification of air flows of known CO2 concentration allowed the calculation of carbon fluxes toward the earth atmosphere which is estimated to about 340 gm-2yr-1. Since 15 years, the monitoring made in the Villars cave at two different levels has shown that the air temperature displays small seasonal variations in the upper galleries while it is not detectable in the lower ones. Average annual temperature difference between these two levels is of more than 1°C, showing that local differences in a single cave can be significant. A global warming trend likely correlated with local external temperature changes is observed in both levels since the beginning of the monitoring in 1996 which is not the case in Chauvet and Esparros caves. The stable isotope composition of the seepage water of the Villars cave and drip rates measured under several stalactites give precious information about the mixture of the rainfall infiltration signal in the unsaturated zone; these long isotopic series are discussed and compared with the rainfall (quantity and isotopic composition) sampled at this site.

Analysis of Vadose Hydrology at Jinapsan Cave, Guam, Mariana Islands

NASA Astrophysics Data System (ADS)

Bautista, K. K.; Jenson, J. W.; Lander, M.; Noronha, A. L.; Righetti, T.

2016-12-01

Six years of monthly data were analyzed from an active tropical limestone cave in Guam, the southernmost of the Mariana Islands, in the western Pacific Ocean. The purpose of this study was to characterize vadose processes of aquifer recharge in the Plio-Pleistocene Mariana Limestone, which occupies about 75% of the surface of the Northern Guam Lens Aquifer, which produces 90% of the island's drinking water. This hydrogeologic study was conducted concurrent with paleoclimate research, in which correlative data on CO2 and other cave meteorological parameters are also collected. For this study, a ground survey grid was established on the surface above the cave, a vegetated talus slope at the foot of the >150-m cliff in the Mariana Limestone behind the cave. Cave and vadose zone 3-D models were constructed from the surface survey and an interior cave survey. Cross sections display talus slope features (33°), notational talus grain size distribution, inferred epikarst and vadose layer dimensions, cave slope (-34°) and structural and geomorphic features of the cave, including a brackish sea-level pool at the cave bottom. GIS products include georeferenced cave boundary and cave room shapefiles. A plan-view map displays significant boulder talus and limestone forest trees, cave entrance location and the underlying cave boundary and fractures mapped on the cave ceiling. Thicknesses of the talus and vadose bedrock sections range from 1.3 to 17.0 meters and 1.7 to 46.4 meters, respectively. Drip rate and discharge rate data from 7 cave stations are presented in graphs showing varying responses between percolation and changes in rainfall during wet (Jul-Dec) and dry (Jan-Jun) seasons. Three stations exhibited fast responses to wet season rainfall, which gradually dropped during the dry season. Two of these stations are at separate cave ceiling fractures. The third is indiscernible from its distance (>4m) above the floor. Three stations exhibited slow responses in both wet and dry seasons, which may be attributed to matrix percolation. One station exhibited slow responses, except for three consecutive months of fast response, a probable effect of short-term pathway rerouting. One slow percolation station also showed a semi-diurnal pattern in its drip rate, which correlates with the atmospheric tidal signal.

Rainfall estimation with TFR model using Ensemble Kalman filter

NASA Astrophysics Data System (ADS)

Asyiqotur Rohmah, Nabila; Apriliani, Erna

2018-03-01

Rainfall fluctuation can affect condition of other environment, correlated with economic activity and public health. The increasing of global average temperature is influenced by the increasing of CO2 in the atmosphere, which caused climate change. Meanwhile, the forests as carbon sinks that help keep the carbon cycle and climate change mitigation. Climate change caused by rainfall intensity deviations can affect the economy of a region, and even countries. It encourages research on rainfall associated with an area of forest. In this study, the mathematics model that used is a model which describes the global temperatures, forest cover, and seasonal rainfall called the TFR (temperature, forest cover, and rainfall) model. The model will be discretized first, and then it will be estimated by the method of Ensemble Kalman Filter (EnKF). The result shows that the more ensembles used in estimation, the better the result is. Also, the accurateness of simulation result is influenced by measurement variable. If a variable is measurement data, the result of simulation is better.

Early warnings of the potential for malaria transmission in Rural Africa using the Hydrology, Entomology and Malaria Transmission Simulator (HYDREMATS)

NASA Astrophysics Data System (ADS)

Yamana, T. K.; Eltahir, E. A.

2010-12-01

Early warnings of malaria transmission allow health officials to better prepare for future epidemics. Monitoring rainfall is recognized as an important part of malaria early warning systems, as outlined by the Roll Back Malaria Initiative. The Hydrology, Entomology and Malaria Simulator (HYDREMATS) is a mechanistic model that relates rainfall to malaria transmission, and could be used to provide early warnings of malaria epidemics. HYDREMATS is used to make predictions of mosquito populations and vectorial capacity for 2005, 2006, and 2007 in Banizoumbou village in western Niger. HYDREMATS is forced by observed rainfall, followed by a rainfall prediction based on the seasonal mean rainfall for a period two or four weeks into the future. Predictions made using this method provided reasonable estimates of mosquito populations and vectorial capacity, two to four weeks in advance. The predictions were significantly improved compared to those made when HYDREMATS was forced with seasonal mean rainfall alone.

Optimizing fumigation efficiency by doubling drip line number and using low permeability film in raised-bed production systems

USDA-ARS?s Scientific Manuscript database

Southern California strawberries are planted in raised-beds covered by polyethylene (PE) film and typically are irrigated with two drip lines placed near the bed surface. To control soil-borne pests, fumigants are commonly applied through the drip lines prior to transplanting strawberries, but effic...

Improving fumigation efficiency by increasing drip-tape number and using low permeability film in raised-bed production systems

USDA-ARS?s Scientific Manuscript database

Drip fumigation is commonly used for controlling soilborne pests in raised-bed strawberry production systems in California. However, the high emission loss and poor pest control indicate that the current fumigation practice with two drip tapes and polyethylene film (PE) covering need to be improved....

40 CFR 63.1007 - Pumps in light liquid service standards.

Code of Federal Regulations, 2012 CFR

2012-07-01

... inspection each calendar week for indications of liquids dripping from the pump seal. The owner or operator... indications of liquids dripping from the pump seal, a leak is detected. Unless the owner or operator... indications of liquids dripping. (e) Special provisions for pumps—(1) Dual mechanical seal pumps. Each pump...

40 CFR 63.1007 - Pumps in light liquid service standards.

Code of Federal Regulations, 2014 CFR

2014-07-01

... inspection each calendar week for indications of liquids dripping from the pump seal. The owner or operator... indications of liquids dripping from the pump seal, a leak is detected. Unless the owner or operator... indications of liquids dripping. (e) Special provisions for pumps—(1) Dual mechanical seal pumps. Each pump...

40 CFR 63.1007 - Pumps in light liquid service standards.

Code of Federal Regulations, 2013 CFR

2013-07-01

... inspection each calendar week for indications of liquids dripping from the pump seal. The owner or operator... indications of liquids dripping from the pump seal, a leak is detected. Unless the owner or operator... indications of liquids dripping. (e) Special provisions for pumps—(1) Dual mechanical seal pumps. Each pump...

40 CFR 265.442 - Design and installation of new drip pads.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 26 2011-07-01 2011-07-01 false Design and installation of new drip pads. 265.442 Section 265.442 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) INTERIM STATUS STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Drip Pads §...

Performance of precision mobile drip irrigation in the Texas High Plains region

USDA-ARS?s Scientific Manuscript database

Mobile drip irrigation (MDI) technology adapts driplines to the drop hoses of moving sprinkler systems to apply water as the drip lines are pulled across the field. There is interest in this technology among farmers in the Texas High Plains region to help sustain irrigated agriculture. However, info...

Simulation and Sensitivity in a Nested Modeling System for South America. Part II: GCM Boundary Forcing.

NASA Astrophysics Data System (ADS)

Rojas, Maisa; Seth, Anji

2003-08-01

of this study, the RegCM's ability to simulate circulation and rainfall observed in the two extreme seasons was demonstrated when driven at the lateral boundaries by reanalyzed forcing. Seasonal integrations with the RegCM driven by GCM ensemble-derived lateral boundary forcing demonstrate that the nested model responds well to the SST forcing, by capturing the major features of the circulation and rainfall differences between the two years. The GCM-driven model also improves upon the monthly evolution of rainfall compared with that from the GCM. However, the nested model rainfall simulations for the two seasons are degraded compared with those from the reanalyses-driven RegCM integrations. The poor location of the Atlantic intertropical convergence zone (ITCZ) in the GCM leads to excess rainfall in Nordeste in the nested model.An expanded domain was tested, wherein the RegCM was permitted more internal freedom to respond to SST and regional orographic forcing. Results show that the RegCM is able to improve the location of the ITCZ, and the seasonal evolution of rainfall in Nordeste, the Amazon region, and the southeastern region of Brazil. However, it remains that the limiting factor in the skill of the nested modeling system is the quality of the lateral boundary forcing provided by the global model.

Hydrological control of large hurricane-induced lahars: evidence from rainfall-runoff modeling, seismic and video monitoring

NASA Astrophysics Data System (ADS)

Capra, Lucia; Coviello, Velio; Borselli, Lorenzo; Márquez-Ramírez, Víctor-Hugo; Arámbula-Mendoza, Raul

2018-03-01

The Volcán de Colima, one of the most active volcanoes in Mexico, is commonly affected by tropical rains related to hurricanes that form over the Pacific Ocean. In 2011, 2013 and 2015 hurricanes Jova, Manuel and Patricia, respectively, triggered tropical storms that deposited up to 400 mm of rain in 36 h, with maximum intensities of 50 mm h -1. The effects were devastating, with the formation of multiple lahars along La Lumbre and Montegrande ravines, which are the most active channels in sediment delivery on the south-southwest flank of the volcano. Deep erosion along the river channels and several marginal landslides were observed, and the arrival of block-rich flow fronts resulted in damages to bridges and paved roads in the distal reaches of the ravines. The temporal sequence of these flow events is reconstructed and analyzed using monitoring data (including video images, seismic records and rainfall data) with respect to the rainfall characteristics and the hydrologic response of the watersheds based on rainfall-runoff numerical simulation. For the studied events, lahars occurred 5-6 h after the onset of rainfall, lasted several hours and were characterized by several pulses with block-rich fronts and a maximum flow discharge of 900 m3 s -1. Rainfall-runoff simulations were performer using the SCS-curve number and the Green-Ampt infiltration models, providing a similar result in the detection of simulated maximum watershed peaks discharge. Results show different behavior for the arrival times of the first lahar pulses that correlate with the simulated catchment's peak discharge for La Lumbre ravine and with the peaks in rainfall intensity for Montegrande ravine. This different behavior is related to the area and shape of the two watersheds. Nevertheless, in all analyzed cases, the largest lahar pulse always corresponds with the last one and correlates with the simulated maximum peak discharge of these catchments. Data presented here show that flow pulses within a lahar are not randomly distributed in time, and they can be correlated with rainfall peak intensity and/or watershed discharge, depending on the watershed area and shape. This outcome has important implications for hazard assessment during extreme hydro-meteorological events, as it could help in providing real-time alerts. A theoretical rainfall distribution curve was designed for Volcán de Colima based on the rainfall and time distribution of hurricanes Manuel and Patricia. This can be used to run simulations using weather forecasts prior to the actual event, in order to estimate the arrival time of main lahar pulses, usually characterized by block-rich fronts, which are responsible for most of the damage to infrastructure and loss of goods and lives.

Effect of ionizing radiation on the physiological activities of ethanol extract from hizikia fusiformis cooking drips.

PubMed

Kim, Hyun-Joo; Choi, Jong-il; Kim, Duk-Jin; Kim, Jae-Hun; Soo Chun, Byeong; Hyun Ahn, Dong; Sun Yook, Hong; Byun, Myung-Woo; Kim, Mi-Jung; Shin, Myung-Gon; Lee, Ju-Woon

2009-01-01

Although the byproduct from Hizikia fusiformis industry had many nutrients, it is being wasted. In this study, the physiological activities of cooking drip extracts from H. fusiformis (CDHF) were determined to investigate the effect of a gamma and an electron beam irradiations. DPPH radical scavenging activity and tyrosinase and ACE inhibition effects of the gamma and electron beam irradiated CDHF extracts were increased with increasing irradiation dose. These were reasoned by the increase in the content of the total polyphenolic compound of CDHF by the gamma and electron beam irradiation. There were no differences for the radiation types. These results show that ionizing radiation could be used for enhancing the functional activity of CDHF which is a major by-product in Hizikia fusiformis processing, in various applications.

Adjusting Satellite Rainfall Error in Mountainous Areas for Flood Modeling Applications

NASA Astrophysics Data System (ADS)

Zhang, X.; Anagnostou, E. N.; Astitha, M.; Vergara, H. J.; Gourley, J. J.; Hong, Y.

2014-12-01

This study aims to investigate the use of high-resolution Numerical Weather Prediction (NWP) for evaluating biases of satellite rainfall estimates of flood-inducing storms in mountainous areas and associated improvements in flood modeling. Satellite-retrieved precipitation has been considered as a feasible data source for global-scale flood modeling, given that satellite has the spatial coverage advantage over in situ (rain gauges and radar) observations particularly over mountainous areas. However, orographically induced heavy precipitation events tend to be underestimated and spatially smoothed by satellite products, which error propagates non-linearly in flood simulations.We apply a recently developed retrieval error and resolution effect correction method (Zhang et al. 2013*) on the NOAA Climate Prediction Center morphing technique (CMORPH) product based on NWP analysis (or forecasting in the case of real-time satellite products). The NWP rainfall is derived from the Weather Research and Forecasting Model (WRF) set up with high spatial resolution (1-2 km) and explicit treatment of precipitation microphysics.In this study we will show results on NWP-adjusted CMORPH rain rates based on tropical cyclones and a convective precipitation event measured during NASA's IPHEX experiment in the South Appalachian region. We will use hydrologic simulations over different basins in the region to evaluate propagation of bias correction in flood simulations. We show that the adjustment reduced the underestimation of high rain rates thus moderating the strong rainfall magnitude dependence of CMORPH rainfall bias, which results in significant improvement in flood peak simulations. Further study over Blue Nile Basin (western Ethiopia) will be investigated and included in the presentation. *Zhang, X. et al. 2013: Using NWP Simulations in Satellite Rainfall Estimation of Heavy Precipitation Events over Mountainous Areas. J. Hydrometeor, 14, 1844-1858.

Downscaling of global climate change estimates to regional scales: An application to Iberian rainfall in wintertime

DOE Office of Scientific and Technical Information (OSTI.GOV)

von Storch, H.; Zorita, E.; Cubasch, U.

A statistical strategy to deduct regional-scale features from climate general circulation model (GCM) simulations has been designed and tested. The main idea is to interrelate the characteristic patterns of observed simultaneous variations of regional climate parameters and of large-scale atmospheric flow using the canonical correlation technique. The large-scale North Atlantic sea level pressure (SLP) is related to the regional, variable, winter (DJF) mean Iberian Peninsula rainfall. The skill of the resulting statistical model is shown by reproducing, to a good approximation, the winter mean Iberian rainfall from 1900 to present from the observed North Atlantic mean SLP distributions. It ismore » shown that this observed relationship between these two variables is not well reproduced in the output of a general circulation model (GCM). The implications for Iberian rainfall changes as the response to increasing atmospheric greenhouse-gas concentrations simulated by two GCM experiments are examined with the proposed statistical model. In an instantaneous [open quotes]2 CO[sub 2][close quotes] doubling experiment, using the simulated change of the mean North Atlantic SLP field to predict Iberian rainfall yields, there is an insignificant increase of area-averaged rainfall of I mm/month, with maximum values of 4 mm/month in the northwest of the peninsula. In contrast, for the four GCM grid points representing the lberian Peninsula, the change is - 10 mm/month, with a minimum of - 19 mm/month in the southwest. In the second experiment, with the IPCC scenario A ([open quotes]business as usual[close quotes]) increase of CO[sub 2], the statistical-model results partially differ from the directly simulated rainfall changes: in the experimental range of 100 years, the area-averaged rainfall decreases by 7 mm/month (statistical model), and by 9 mm/month (GCM); at the same time the amplitude of the interdecadal variability is quite different. 17 refs., 10 figs.« less

Estimation of typhoon rainfall in GaoPing River: A Multivariate Maximum Entropy Method

NASA Astrophysics Data System (ADS)

Pei-Jui, Wu; Hwa-Lung, Yu

2016-04-01

The heavy rainfall from typhoons is the main factor of the natural disaster in Taiwan, which causes the significant loss of human lives and properties. Statistically average 3.5 typhoons invade Taiwan every year, and the serious typhoon, Morakot in 2009, impacted Taiwan in recorded history. Because the duration, path and intensity of typhoon, also affect the temporal and spatial rainfall type in specific region , finding the characteristics of the typhoon rainfall type is advantageous when we try to estimate the quantity of rainfall. This study developed a rainfall prediction model and can be divided three parts. First, using the EEOF(extended empirical orthogonal function) to classify the typhoon events, and decompose the standard rainfall type of all stations of each typhoon event into the EOF and PC(principal component). So we can classify the typhoon events which vary similarly in temporally and spatially as the similar typhoon types. Next, according to the classification above, we construct the PDF(probability density function) in different space and time by means of using the multivariate maximum entropy from the first to forth moment statistically. Therefore, we can get the probability of each stations of each time. Final we use the BME(Bayesian Maximum Entropy method) to construct the typhoon rainfall prediction model , and to estimate the rainfall for the case of GaoPing river which located in south of Taiwan.This study could be useful for typhoon rainfall predictions in future and suitable to government for the typhoon disaster prevention .

Simulated peak flows and water-surface profiles for Scott Creek near Sylva, North Carolina

USGS Publications Warehouse

Pope, B.F.

1996-01-01

Peak flows were simulated for Scott Creek, just upstream from Sylva, in Jackson County, North Carolina, in order to provide Jackson County officials with information that can be used to improve preparation for and response to flash floods along the reach of Scott Creek that flows through Sylva. A U.S. Geological Survey rainfall-runoff model was calibrated using observed rainfall and streamflow data collected from March 1994 through September 1995. Standard errors for calibration were 34 percent for runoff volumes and 21 percent for peak flows. The calibrated model was used to simulate peak flows resulting from syn- thetic rainfall amounts of 1.0, 2.5, 5.0, and 7.5 inches in 24-hour periods. For each rainfall amount, peak flows were simulated under low-, moderate-, and high-antecedent soil-moisture conditions, represented by selected 3-month periods of daily rainfall and evaporation record from nearby climatic-data measuring stations. Simulated peak flows ranged from 89 to 10,100 cubic feet per second. Profiles of water-surface elevations for selected observed and simu- lated peak flows were computed for the reach of Scott Creek that flows through Sylva, North Carolina. The profiles were computed using the U.S. Army Corps of Engineers HEC-2 Water Surface Profiles computer program and channel cross-section data collected by the Tennessee Valley Authority. The stage-discharge relation for Scott Creek at the simulation site has changed since the collection of the cross-section data. These changes, however, are such that the water-surface profiles presented in this report likely overestimate the true water-surface elevations at the simulation site for a given peak flow

A remote drip infusion monitoring system employing Bluetooth.

PubMed

Amano, Hikaru; Ogawa, Hidekuni; Maki, Hiromichi; Tsukamoto, Sosuke; Yonezawa, Yoshiharu; Caldwell, W Morton

2012-01-01

We have developed a remote drip infusion monitoring system for use in hospitals. The system consists of several infusion monitoring devices and a central monitor. The infusion monitoring device employing a Bluetooth module can detect the drip infusion rate and an empty infusion solution bag, and then these data are sent to the central monitor placed at the nurses' station via the Bluetooth. The central monitor receives the data from several infusion monitoring devices and then displays graphically them. Therefore, the developed system can monitor intensively the drip infusion situation of the several patients at the nurses' station.

Bacterial content in runoff from simulated rainfall applied to plots amended with poultry litter

USDA-ARS?s Scientific Manuscript database

To evaluate potential bacterial runoff from poultry litter, litter was applied to test plots and exposed to simulated rainfall 1, 8 or 15 d after litter application. Runoff samples were tested for Salmonella and Campylobacter, two bacterial pathogens commonly associated with poultry, as well as com...

Rainfall–runoff model parameter estimation and uncertainty evaluation on small plots

EPA Science Inventory

Four seasonal rainfall simulations in 2009 and 2010were applied to a field containing 36 plots (0.75 × 2 m each), resulting in 144 runoff events. In all simulations, a constant rate of rainfall was applied then halted 60min after initiation of runoff, with plot-scale monitoring o...

Reduced-complexity multi-site rainfall generation: one million years over night using the model TripleM

NASA Astrophysics Data System (ADS)

Breinl, Korbinian; Di Baldassarre, Giuliano; Girons Lopez, Marc

2017-04-01

We assess uncertainties of multi-site rainfall generation across spatial scales and different climatic conditions. Many research subjects in earth sciences such as floods, droughts or water balance simulations require the generation of long rainfall time series. In large study areas the simulation at multiple sites becomes indispensable to account for the spatial rainfall variability, but becomes more complex compared to a single site due to the intermittent nature of rainfall. Weather generators can be used for extrapolating rainfall time series, and various models have been presented in the literature. Even though the large majority of multi-site rainfall generators is based on similar methods, such as resampling techniques or Markovian processes, they often become too complex. We think that this complexity has been a limit for the application of such tools. Furthermore, the majority of multi-site rainfall generators found in the literature are either not publicly available or intended for being applied at small geographical scales, often only in temperate climates. Here we present a revised, and now publicly available, version of a multi-site rainfall generation code first applied in 2014 in Austria and France, which we call TripleM (Multisite Markov Model). We test this fast and robust code with daily rainfall observations from the United States, in a subtropical, tropical and temperate climate, using rain gauge networks with a maximum site distance above 1,000km, thereby generating one million years of synthetic time series. The modelling of these one million years takes one night on a recent desktop computer. In this research, we first start the simulations with a small station network of three sites and progressively increase the number of sites and the spatial extent, and analyze the changing uncertainties for multiple statistical metrics such as dry and wet spells, rainfall autocorrelation, lagged cross correlations and the inter-annual rainfall variability. Our study contributes to the scientific community of earth sciences and the ongoing debate on extreme precipitation in a changing climate by making a stable, and very easily applicable, multi-site rainfall generation code available to the research community and providing a better understanding of the performance of multi-site rainfall generation depending on spatial scales and climatic conditions.

Interannual Tropical Rainfall Variability in General Circulation Model Simulations Associated with the Atmospheric Model Intercomparison Project.

NASA Astrophysics Data System (ADS)

Sperber, K. R.; Palmer, T. N.

1996-11-01

The interannual variability of rainfall over the Indian subcontinent, the African Sahel, and the Nordeste region of Brazil have been evaluated in 32 models for the period 1979-88 as part of the Atmospheric Model Intercomparison Project (AMIP). The interannual variations of Nordeste rainfall are the most readily captured, owing to the intimate link with Pacific and Atlantic sea surface temperatures. The precipitation variations over India and the Sahel are less well simulated. Additionally, an Indian monsoon wind shear index was calculated for each model. Evaluation of the interannual variability of a wind shear index over the summer monsoon region indicates that the models exhibit greater fidelity in capturing the large-scale dynamic fluctuations than the regional-scale rainfall variations. A rainfall/SST teleconnection quality control was used to objectively stratify model performance. Skill scores improved for those models that qualitatively simulated the observed rainfall/El Niño- Southern Oscillation SST correlation pattern. This subset of models also had a rainfall climatology that was in better agreement with observations, indicating a link between systematic model error and the ability to simulate interannual variations.A suite of six European Centre for Medium-Range Weather Forecasts (ECMWF) AMIP runs (differing only in their initial conditions) have also been examined. As observed, all-India rainfall was enhanced in 1988 relative to 1987 in each of these realizations. All-India rainfall variability during other years showed little or no predictability, possibly due to internal chaotic dynamics associated with intraseasonal monsoon fluctuations and/or unpredictable land surface process interactions. The interannual variations of Nordeste rainfall were best represented. The State University of New York at Albany/National Center for Atmospheric Research Genesis model was run in five initial condition realizations. In this model, the Nordeste rainfall variability was also best reproduced. However, for all regions the skill was less than that of the ECMWF model.The relationships of the all-India and Sahel rainfall/SST teleconnections with horizontal resolution, convection scheme closure, and numerics have been evaluated. Models with resolution T42 performed more poorly than lower-resolution models. The higher resolution models were predominantly spectral. At low resolution, spectral versus gridpoint numerics performed with nearly equal verisimilitude. At low resolution, moisture convergence closure was slightly more preferable than other convective closure techniques. At high resolution, the models that used moisture convergence closure performed very poorly, suggesting that moisture convergence may be problematic for models with horizontal resolution T42.

Rainfall: State of the Science

NASA Astrophysics Data System (ADS)

Testik, Firat Y.; Gebremichael, Mekonnen

Rainfall: State of the Science offers the most up-to-date knowledge on the fundamental and practical aspects of rainfall. Each chapter, self-contained and written by prominent scientists in their respective fields, provides three forms of information: fundamental principles, detailed overview of current knowledge and description of existing methods, and emerging techniques and future research directions. The book discusses • Rainfall microphysics: raindrop morphodynamics, interactions, size distribution, and evolution • Rainfall measurement and estimation: ground-based direct measurement (disdrometer and rain gauge), weather radar rainfall estimation, polarimetric radar rainfall estimation, and satellite rainfall estimation • Statistical analyses: intensity-duration-frequency curves, frequency analysis of extreme events, spatial analyses, simulation and disaggregation, ensemble approach for radar rainfall uncertainty, and uncertainty analysis of satellite rainfall products The book is tailored to be an indispensable reference for researchers, practitioners, and graduate students who study any aspect of rainfall or utilize rainfall information in various science and engineering disciplines.

New Indices to Evaluate the Effects of Rainfall Pattern on Runoff and Soil Loss under Different Vegetation in the Loess Plateau, China.

NASA Astrophysics Data System (ADS)

Liu, J.; Gao, G.; Jiao, L.; Fu, B.

2016-12-01

The rainfall amount, density and duration were commonly used to evaluate the influences of rainfall on runoff and soil loss, which could completely express the information of rainfall, especially rainfall pattern. In this study, the peak zone of rainfall intensity (PZRI) and intra-event intermittency of rainfall (IERI) were developed to detect the effects of rainfall pattern on runoff and soil loss under different land cover types in the Loess Plateau of China. The runoff and soil loss of three vegetation types (Prunus armeniaca, Artemisia sacrorum and Andropogon yunnanensis) and bare land were measured from 2012 to 2015. The PZRI was significantly correlated with average rainfall intensity (I) and maximum rainfall intensity in 30 minutes (I30). The runoff coefficient (RC) and soil loss were not significantly correlated with I, but they were significantly affected by I30 and PZRI (p<0.05). The greater value of IERI indicated more proportion of PZRI in rainfall duration, and there was positive correlation between IERI and RC. It was showed that the RC was most correlated with PZRI, whereas the correlation between soil loss and I30 was most significant under all cover types. This indicated that the changes of rainfall pattern had more effects on runoff than soil loss. In addition, the position of PZRI in the rainfall profile had an important role on runoff and soil loss. RC and soil loss under bare land was most sensitive to the occurrence period of rainfall peak, followed by Prunus armeniaca, Artemisia sacrorum and Andropogon yunnanensis.

The effect of the fires on gypseous soil properties: changes of the hydrology and splash resistance.

NASA Astrophysics Data System (ADS)

León, J.; Seeger, M.; Echeverría, M.; Badía, D.; Peters, P.

2012-04-01

Mediterranean ecosystems have been severely affected by fires in the last decades. Due to social and economical changes, wildfires have caused hydrological and geomorphologic changes to be more pronounced, resulting in enhanced soil erosion. Soil heating caused by fires affects soil aggregates stability, water infiltration and may generate hydrophobicity. In order to understand how wildfire affects soil hydrological behavior in general, and splash and runoff processes in particular, of gypsum soils,it is advantageous to use a rainfall simulator. In August 2009 a large forest fire affected 6700 ha in Remolinos (NW Zaragoza, Spain). The area is covered by shrubs such as gorse (Genista scorpius L.), broom (Retama sphaerocarpa L.) and rosemary (Rosmarinus officinalis L.), and with small areas occupied by Aleppo pine (Pinus halepensis Mill) and Kermes evergreen-oak (Quercus coccifera L.). This region has a semarid Mediterranean climate, with an average annual rainfall ca 560 mm and a mean annual temperature of 12.5°C, resulting in an estimated climatic water deficit of ca. 400mm. The relief consists of stepped slopes (200-748 m), on two different types of soil have developed: Renzic Phaeozem, on limestone, and Haplic Gypsisol, on gypsum (IUSS, 2006). Within this study, we wanted to investigate the differences in affection by fire of the different soil types, as it may be caused by different fire intensities. Therefore, both soil types were sampled after fire. Also, similar locations were sampled which were not affected by the wildfires. With this, we could differentiate 4 treatments: burnt and unburnt pine forest and burnt and unburnt shrub on gypseous soils. We designed a set of lab experiments to elucidate the effect of heat on soil composition, aggregate stability, and splash susceptibility. Samples were taken using cylinders of 5 cm depth. Under laboratory conditions were measured pH, CE, organic matter (OM), soil aggregates stability (SAS), bulk density, porosity and mineralogical changes, using 5 subsamples of each treatment. The samples were heated at different temperatures (105 °C and 205 °C) in an oven for 30 min to simulated different fire intensities, for comparison. A set was only air dried (35 °C). To study the splash effect of the gypsum soils were use small scale rainfall simulator in laboratory, applying a rainfall intensity of 47 mm h-1 during 20 min, resulting in a kinetic energy of 8.94 J m-2 mm-1. The gross loss of material of each of the undisturbed samples was measured after 20 minutes of simulation. The pH is slightly alkaline and oscillates between 7.93-8.32, depending on soil cover type, and is highest under burnt pine forest. The EC (2.08-5.01 mS cm-1) did not change after heating of the unburnt shrub cover, but in the soil under burnt pine forest, the EC was lowered with increasing temperature. The OM content is moderate (3.73-4.85 %), and higher on burnt soils, increasing also with an increase of treatment temperature. The SAS (43.17-75.92 %) is strongly depending on the temperature applied, and was found higher on the burnt surfaces. The gypsum content of the soils is moderate to high (11.30-39.58 %), but decreases with the treatment at 205°C. The soil loss by splash vaied between 0.9 to 2.8 g (per sample) after 20 min of rainfall simulation. Highest losses were found on burnt surfaces. The results show that fire and temperature affects not all characteristics of soils. Acknowledgements: This research was supported by the Ministry of Science and Innovation BES-2008-003056, the CETSUS project (CGL2007-66644-C04-04/HIDCLI) and the Geomorphology and Global Change Research Group (D.G.A., 2011). The Spanish Army has supported this work at the San Gregorio CENAF.

Greenhouse and field-based studies on the distribution of dimethoate in cotton and its effect on Tetranychus urticae by drip irrigation.

PubMed

He, Jiangtao; Zhou, Lijuan; Yao, Qiang; Liu, Bo; Xu, Hanhong; Huang, Jiguang

2018-01-01

The two-spotted spider mite, Tetranychus urticae Koch is an important pest of cotton. We investigated the efficacy of dimethoate in controlling T. urticae by drip irrigation. Greenhouse and field experiments were carried out to determine the efficacy of dimethoate to T. urticae and the absorption and distribution of dimethoate in cotton. Greenhouse results showed that cotton leaves received higher amounts of dimethoate compared with cotton roots and stems, with higher amounts in young leaves compared with old leaves and cotyledon having the lowest amounts among leaves. Field results showed the efficacy of dimethoate to T. urticae by drip irrigation varied by volume of dripping water, soil pH and dimethoate dosage. Dimethoate applied at 3.00 kg ha -1 with 200 m 3  ha -1 water at weak acidic soil pH (5.70-6.70) through drip irrigation can obtain satisfactory control efficacy (81.49%, 7 days) to T. urticae, without negatively impacting on its natural enemy Neoseiulus cucumeris. The residue of dimethoate in all cotton seed samples were not detectable. These results demonstrate the effectiveness of applying dimethoate by drip irrigation for control of T. urticae on cotton. This knowledge could aid in the applicability of dimethoate by drip irrigation for field management of T. urticae populations. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Effects of alternate drip irrigation and superabsorbent polymers on growth and water use of young coffee tree.

PubMed

Liu, Xiaogang; Li, Fusheng; Yang, Qiliang; Wang, Xinle

2016-07-01

To obtain optimal irrigation management for young coffee tree, the effects of alternate drip irrigation (ADI) and superabsorbent polymers on physiology, growth, dry mass accumulation and water use on one-year old Coffea arabica L. tree were investigated. This experiment had three drip irrigation methods, i.e., conventional drip irrigation (CDI), alternate drip irrigation (ADI) and fixed drip irrigation (FDI), and two levels of superabsorbent polymers, i.e., no superabsorbent polymers (NSAP) and added superabsorbent polymers (SAP). Compared to CDI, ADI saved irrigation water by 32.1% and increased water use efficiency (WUE) by 29.9%. SAP increased root-shoot ratio, total dry mass and WUE by 20.3, 24.9 and 33.0%, respectively, when compared to NSAP. Compared to CDI with NSAP treatment, ADI with SAP treatment increased total dry mass by 13.8% and saved irrigation water by 34.4%, thus increased WUE by 73.4%, and it increased root activity, the contents of chlorophyll and soluble sugar in leaves by 162.4, 38.0 and 8.5%, but reduced the contents of proline and malondialdehyde in leaves by 7.2 and 9.7%, respectively. Thus, alternate drip irrigation with superabsorbent polymers increased the growth and WUE of young Coffea arabica L. tree and was optimal irrigation management for young coffee tree.

Usage of drip drops as stimuli in an auditory P300 BCI paradigm.

PubMed

Huang, Minqiang; Jin, Jing; Zhang, Yu; Hu, Dewen; Wang, Xingyu

2018-02-01

Recently, many auditory BCIs are using beeps as auditory stimuli, while beeps sound unnatural and unpleasant for some people. It is proved that natural sounds make people feel comfortable, decrease fatigue, and improve the performance of auditory BCI systems. Drip drop is a kind of natural sounds that makes humans feel relaxed and comfortable. In this work, three kinds of drip drops were used as stimuli in an auditory-based BCI system to improve the user-friendness of the system. This study explored whether drip drops could be used as stimuli in the auditory BCI system. The auditory BCI paradigm with drip-drop stimuli, which was called the drip-drop paradigm (DP), was compared with the auditory paradigm with beep stimuli, also known as the beep paradigm (BP), in items of event-related potential amplitudes, online accuracies and scores on the likability and difficulty to demonstrate the advantages of DP. DP obtained significantly higher online accuracy and information transfer rate than the BP ( p  < 0.05, Wilcoxon signed test; p  < 0.05, Wilcoxon signed test). Besides, DP obtained higher scores on the likability with no significant difference on the difficulty ( p  < 0.05, Wilcoxon signed test). The results showed that the drip drops were reliable acoustic materials as stimuli in an auditory BCI system.

Forty years experience in developing and using rainfall simulators under tropical and Mediterranean conditions

NASA Astrophysics Data System (ADS)

Pla-Sentís, Ildefonso; Nacci, Silvana

2010-05-01

Rainfall simulation has been used as a practical tool for evaluating the interaction of falling water drops on the soil surface, to measure both stability of soil aggregates to drop impact and water infiltration rates. In both cases it is tried to simulate the effects of natural rainfall, which usually occurs at very different, variable and erratic rates and intensities. One of the main arguments against the use of rainfall simulators is the difficulty to reproduce the size, final velocity and kinetic energy of the drops in natural rainfall. Since the early 70´s we have been developing and using different kinds of rainfall simulators, both at laboratory and field levels, and under tropical and Mediterranean soil and climate conditions, in flat and sloping lands. They have been mainly used to evaluate the relative effects of different land use and management, including different cropping systems, tillage practices, surface soil conditioning, surface covers, etc. on soil water infiltration, on runoff and on erosion. Our experience is that in any case it is impossible to reproduce the variable size distribution and terminal velocity of raindrops, and the variable changes in intensity of natural storms, under a particular climate condition. In spite of this, with the use of rainfall simulators it is possible to obtain very good information, which if it is properly interpreted in relation to each particular condition (land and crop management, rainfall characteristics, measurement conditions, etc.) may be used as one of the parameters for deducing and modelling soil water balance and soil moisture regime under different land use and management and variable climate conditions. Due to the possibility for a better control of the intensity of simulated rainfall and of the size of water drops, and the possibility to make more repeated measurements under very variable soil and land conditions, both in the laboratory and specially in the field, the better results have been obtained with small size 500-1000 cm2, easily dismantled, drop former simulators, than with larger, nozzle, or more sophisticated equipments. In this contribution there are presented some of the rainfall simulators developed and used by the main author, and some of the results obtained in different studies of practical problems under tropical and Mediterranean conditions. References Pla, I.,G.Campero, y R.Useche.1974.Physical degradación of agricultural soils in the Western Plains of Venezuela. "Trans.10th Int.Cong.Soil.Sci.Soc". 1:231-240. .Moscú Pla, I. 1975.Effects of bitumen emulsion and polyacrilamide on some physical properties of Venezuelan soils. En "Soil Sci. Soc. Am. Special Publication"• 7. 35-46. Madison. Wisconsin . (USA). Pla, I. 1977.Aggregate size and erosion control on sloping land treated with hydrophobic bitumen emulsion."Soil Conservation and Management in the Humid Tropics".109-115. John Wiley & Sons. Pla, I.1981.Simuladores de lluvia para el estudio de relaciones suelo-agua bajo agricultura de secano en los trópicos. Rev. Fac. Agron. XII(1-2):81-93.Maracay (Venezuela) Pla, I. 1986.A routine laboratory index to predict the effects of soil sealing on soil and water conservation. En "Assesment of Soil Surface Sealing and Crusting". 154-162.State Univ. of Ghent.Gante (Bélgica Pla, I., M.C. Ramos, S. Nacci, F. Fonseca y X. Abreu. 2005. Soil moisture regime in dryland vineyards of Catalunya (Spain) as influenced by climate, soil and land management. "Integrated Soil and Water Management for Orchard Development". FAO Land and Water Bulletin 10. 41-49. Roma (Italia).

A new concept to study the effect of climate change on different flood types

NASA Astrophysics Data System (ADS)

Nissen, Katrin; Nied, Manuela; Pardowitz, Tobias; Ulbrich, Uwe; Merz, Bruno

2014-05-01

Flooding is triggered by the interaction of various processes. Especially important are the hydrological conditions prior to the event (e.g. soil saturation, snow cover) and the meteorological conditions during flood development (e.g. rainfall, temperature). Depending on these (pre-) conditions different flood types may develop such as long-rain floods, short-rain floods, flash floods, snowmelt floods and rain-on-snow floods. A new concept taking these factors into account is introduced and applied to flooding in the Elbe River basin. During the period September 1957 to August 2002, 82 flood events are identified and classified according to their flood type. The hydrological and meteorological conditions at each day during the analysis period are detemined. In case of the hydrological conditions, a soil moisture pattern classification is carried out. Soil moisture is simulated with a rainfall-runoff model driven by atmospheric observations. Days of similar soil moisture patterns are identified by a principle component analysis and a subsequent cluster analysis on the leading principal components. The meteorological conditions are identified by applying a cluster analysis to the geopotential height, temperature and humidity fields of the ERA40 reanalysis data set using the SANDRA cluster algorithm. We are able to identify specific pattern combinations of hydrological pre-conditions and meteorological conditions which favour different flood types. Based on these results it is possible to analyse the effect of climate change on different flood types. As an example we show first results obtained using an ensemble of climate scenario simulations of ECHAM5 MPIOM model, taking only the changes in the meteorological conditions into account. According to the simulations, the frequency of the meteorological patterns favouring long-rain, short-rain and flash floods will not change significantly under future climate conditions. A significant increase is, however, predicted for the amount of precipitation associated with many of the relevant meteorological patterns. The increase varies between 12 and 67% depending on the weather pattern.

A web-based Tamsui River flood early-warning system with correction of real-time water stage using monitoring data

NASA Astrophysics Data System (ADS)

Liao, H. Y.; Lin, Y. J.; Chang, H. K.; Shang, R. K.; Kuo, H. C.; Lai, J. S.; Tan, Y. C.

2017-12-01

Taiwan encounters heavy rainfalls frequently. There are three to four typhoons striking Taiwan every year. To provide lead time for reducing flood damage, this study attempt to build a flood early-warning system (FEWS) in Tanshui River using time series correction techniques. The predicted rainfall is used as the input for the rainfall-runoff model. Then, the discharges calculated by the rainfall-runoff model is converted to the 1-D river routing model. The 1-D river routing model will output the simulating water stages in 487 cross sections for the future 48-hr. The downstream water stage at the estuary in 1-D river routing model is provided by storm surge simulation. Next, the water stages of 487 cross sections are corrected by time series model such as autoregressive (AR) model using real-time water stage measurements to improve the predicted accuracy. The results of simulated water stages are displayed on a web-based platform. In addition, the models can be performed remotely by any users with web browsers through a user interface. The on-line video surveillance images, real-time monitoring water stages, and rainfalls can also be shown on this platform. If the simulated water stage exceeds the embankments of Tanshui River, the alerting lights of FEWS will be flashing on the screen. This platform runs periodically and automatically to generate the simulation graphic data of flood water stages for flood disaster prevention and decision making.

Interactions and Survival of Enteric Viruses in Soil Materials

PubMed Central

Sobsey, Mark D.; Dean, Cheryl H.; Knuckles, Maurice E.; Wagner, Ray A.

1980-01-01

There were marked differences in the abilities of eight different soil materials to remove and retain viruses from settled sewage, but for each soil material the behavior of two different viruses, poliovirus type 1 and reovirus type 3, was often similar. Virus adsorption to soil materials was rapid, the majority occurring within 15 min. Clayey materials efficiently adsorbed both viruses from wastewater over a range of pH and total dissolved solids levels. Sands and organic soil materials were comparatively poor adsorbents, but in some cases their ability to adsorb viruses increased at low pH and with the addition of total dissolved solids or divalent cations. Viruses in suspensions of soil material in settled sewage survived for considerable time periods, despite microbial activity. In some cases virus survival was prolonged in suspensions of soil materials compared to soil-free controls. Although sandy and organic soil materials were poor virus adsorbents when suspended in wastewater, they gave ≥95% virus removal from intermittently applied wastewater as unsaturated, 10-cm-deep columns. However, considerable quantities of the retained viruses were washed from the columns by simulated rainfall. Under the same conditions, clayey soil material removed ≥99.9995% of the viruses from applied wastewater, and none were washed from the columns by simulated rainfall. PMID:6250478

Progress Towards Achieving the Challenge of Indian Summer Monsoon Climate Simulation in a Coupled Ocean-Atmosphere Model

NASA Astrophysics Data System (ADS)

Hazra, Anupam; Chaudhari, Hemantkumar S.; Saha, Subodh Kumar; Pokhrel, Samir; Goswami, B. N.

2017-10-01

Simulation of the spatial and temporal structure of the monsoon intraseasonal oscillations (MISOs), which have effects on the seasonal mean and annual cycle of Indian summer monsoon (ISM) rainfall, remains a grand challenge for the state-of-the-art global coupled models. Biases in simulation of the amplitude and northward propagation of MISOs and related dry rainfall bias over ISM region in climate models are limiting the current skill of monsoon prediction. Recent observations indicate that the convective microphysics of clouds may be critical in simulating the observed MISOs. The hypothesis is strongly supported by high fidelity in simulation of the amplitude and space-time spectra of MISO by a coupled climate model, when our physically based modified cloud microphysics scheme is implemented in conjunction with a modified new Simple Arakawa Schubert (nSAS) convective parameterization scheme. Improved simulation of MISOs appears to have been aided by much improved simulation of the observed high cloud fraction and convective to stratiform rain fractions and resulted into a much improved simulation of the ISM rainfall, monsoon onset, and the annual cycle.

The influence of synthetic hyetograph parameters on simulation results of runoff from urban catchment

NASA Astrophysics Data System (ADS)

Mazurkiewicz, Karolina; Skotnicki, Marcin

2018-02-01

The paper presents the results of analysis of the influence of the maximum intensity (peak) location in the synthetic hyetograph and rainfall duration on the maximum outflow from urban catchment. For the calculation Chicago hyetographs with a duration from 15 minutes to 180 minutes and peak location between 20% and 50% of the total rainfall duration were design. Runoff simulation was performed using the SWMM5 program for three models of urban catchment with area from 0.9 km2 to 6.7 km2. It was found that the increase in the rainfall peak location causes the increase in the maximum outflow up to 17%. For a given catchment the greatest maximum outflow is generated by the rainfall, which time to peak corresponds to the flow time through the catchment. Presented results may be useful for choosing the rainfall parameters for storm sewer systems modeling.

40 CFR 264.572 - Design and installation of new drip pads.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 26 2011-07-01 2011-07-01 false Design and installation of new drip pads. 264.572 Section 264.572 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR OWNERS AND OPERATORS OF HAZARDOUS WASTE TREATMENT, STORAGE, AND DISPOSAL FACILITIES Drip Pads § 264.572 Design...

Sensing water from subsurface drip irrigation laterals: In situ sensors, weighing lysimeters and COSMOS under vegetated and bare conditions

USDA-ARS?s Scientific Manuscript database

Characterization of soil water dynamics in the root zone under subsurface drip irrigated (SDI) is complicated by the three dimensional nature of water fluxes from drip emitters plus the fluxes, if any, of water from precipitation. In addition, soil water sensing systems may differ in their operating...

Evaluation of different rainfall products over India for the summer monsoon

NASA Astrophysics Data System (ADS)

Prakash, Satya; Mitra, Ashis; Turner, Andrew; Collins, Mathew; AchutoRao, Krishna

2015-04-01

Summer rainfall over India forms an integral part of the Asian monsoon, which plays a key role in the global water cycle and climate system through coupled atmospheric and oceanic processes. Accurate prediction of Indian summer monsoon rainfall and its variability at various spatiotemporal scales are crucial for agriculture, water resources and hydroelectric-power sectors. Reliable rainfall observations are very important for verification of numerical model outputs and model development. However, high spatiotemporal variability of rainfall makes it difficult to measure adequately with ground-based instruments over a large region of various surface types from deserts to oceans. A number of multi-satellite rainfall products are available to users at different spatial and temporal scales. Each rainfall product has some advantages as well as limitations, hence it is essential to find a suitable region-specific data set among these rainfall products for a particular user application, such as water resources, agricultural modelling etc. In this study, we examine seasonal-mean and daily rainfall datasets for monsoon model validation. First, six multi-satellite and gauge-only rainfall products were evaluated over India at seasonal scale for 27 (JJAS 1979-2005) summer monsoon seasons against gridded 0.5-degree IMD gauge-based rainfall. Various skill metrics are computed to assess the potential of these data sets in representation of large-scale monsoon rainfall at all-India and sub-regional scales. Among the gauge-only data sets, APHRODITE and GPCC appear to outperform the others whereas GPCP is better than CMAP in the merged multi-satellite category. However, there are significant differences among these data sets indicating uncertainty in the observed rainfall over this region, with important implications for the evaluation of model simulations. At the daily scale, TRMM TMPA-3B42 is one of the best available products and is widely used for various hydro-meteorological applications. The existing version 6 (V6) products of TRMM underwent major changes and version 7 (V7) products were released in late 2012, and we compare these to the IMD daily gridded data over the 1998-2010 period. We show a clear improvement in V7 over V6 in the South Asian monsoon region using various skill metrics. Over typical monsoon rainfall zones, biases are improved by 5-10% in V7 over higher-rainfall regions. These results will help users to select appropriate rainfall product for their application. With the recent launch of the GPM Core Observatory, the release of a more advanced high-resolution multi-satellite rainfall product is expected soon.

Transverse mixing of simulated piscicides in small montane streams

USGS Publications Warehouse

Brown, Peter J.; Ard, Jenifer L.; Zale, Alexander V.

2012-01-01

Thorough mixing of piscicides into receiving waters is important for efficient and effective fish eradication. However, no guidance exists for the placement of drip stations with respect to mixing. Salt (NaCl) was used as a tracer to measure the mixing rates of center versus edge applications in riffle–pool, straight, and meandering sections of montane streams. The tracer was applied at either the center or the edge of a channel and measured with a conductivity meter across a downstream grid to determine the distances at which transverse mixing was complete. No advantage was accrued by applying piscicides in different types of channels because transverse mixing distance did not differ among them. However, mixing distance was significantly shorter at center applications. Chemicals entering a stream at the center of the channel mixed thoroughly within 10 stream widths, whereas chemicals entering a stream channel at the edge mixed thoroughly within 20 stream widths.

A First Approach to Global Runoff Simulation using Satellite Rainfall Estimation

NASA Technical Reports Server (NTRS)

Hong, Yang; Adler, Robert F.; Hossain, Faisal; Curtis, Scott; Huffman, George J.

2007-01-01

Many hydrological models have been introduced in the hydrological literature to predict runoff but few of these have become common planning or decision-making tools, either because the data requirements are substantial or because the modeling processes are too complicated for operational application. On the other hand, progress in regional or global rainfall-runoff simulation has been constrained by the difficulty of measuring spatiotemporal variability of the primary causative factor, i.e. rainfall fluxes, continuously over space and time. Building on progress in remote sensing technology, researchers have improved the accuracy, coverage, and resolution of rainfall estimates by combining imagery from infrared, passive microwave, and space-borne radar sensors. Motivated by the recent increasing availability of global remote sensing data for estimating precipitation and describing land surface characteristics, this note reports a ballpark assessment of quasi-global runoff computed by incorporating satellite rainfall data and other remote sensing products in a relatively simple rainfall-runoff simulation approach: the Natural Resources Conservation Service (NRCS) runoff Curve Number (CN) method. Using an Antecedent Precipitation Index (API) as a proxy of antecedent moisture conditions, this note estimates time-varying NRCS-CN values determined by the 5-day normalized API. Driven by multi-year (1998-2006) Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis, quasi-global runoff was retrospectively simulated with the NRCS-CN method and compared to Global Runoff Data Centre data at global and catchment scales. Results demonstrated the potential for using this simple method when diagnosing runoff values from satellite rainfall for the globe and for medium to large river basins. This work was done with the simple NRCS-CN method as a first-cut approach to understanding the challenges that lie ahead in advancing the satellite-based inference of global runoff. We expect that the successes and limitations revealed in this study will lay the basis for applying more advanced methods to capture the dynamic variability of the global hydrologic process for global runoff monltongin real time. The essential ingredient in this work is the use of global satellite-based rainfall estimation.

Attribution of Extreme Rainfall from Landfalling Tropical Cyclones to Climate Change for the Eastern United States

NASA Astrophysics Data System (ADS)

Liu, M.; Yang, L.; Smith, J. A.; Vecchi, G. A.

2017-12-01

Extreme rainfall and flooding associated with landfalling tropical cyclones (TC) is responsible for vast socioeconomic losses and fatalities. Landfalling tropical cyclones are an important element of extreme rainfall and flood peak distributions in the eastern United States. Record floods for USGS stream gauging stations over the eastern US are closely tied to landfalling hurricanes. A small number of storms account for the largest record floods, most notably Hurricanes Diane (1955) and Agnes (1972). The question we address is: if the synoptic conditions accompanying those hurricanes were to be repeated in the future, how would the thermodynamic and dynamic storm properties and associated extreme rainfall differ in response to climate change? We examine three hurricanes: Diane (1955), Agnes (1972) and Irene (2011), due to the contrasts in structure/evolution properties and their important roles in dictating the upper tail properties of extreme rainfall and flood frequency over eastern US. Extreme rainfall from Diane is more localized as the storm maintains tropical characteristics, while synoptic-scale vertical motion associated with extratropical transition is a central feature for extreme rainfall induced by Agnes. Our analyses are based on ensemble simulations using the Weather Research and Forecasting (WRF) model, considering combinations of different physics options (i.e., microphysics, boundary layer schemes). The initial and boundary conditions of WRF simulations for the present-day climate are using the Twentieth Century Reanalysis (20thCR). A sub-selection of GCMs is used, as part of phase 5 of the Coupled Model Intercomparison Project (CMIP5), to provide future climate projections. For future simulations, changes in model fields (i.e., temperature, humidity, geopotential height) between present-day and future climate are first derived and then added to the same 20thCR initial and boundary data used for the present-day simulations, and the ensemble is rerun using identical model configurations. Response of extreme rainfall as well as changes in thermodynamic and dynamic storm properties will be presented and analyzed. Contrasting responses across the three storm events to climate change will shed light on critical environmental factors for TC-related extreme rainfall over eastern US.

Response of runoff and soil loss to reforestation and rainfall type in red soil region of southern China.

PubMed

Huang, Zhigang; Ouyang, Zhiyun; Li, Fengrui; Zheng, Hua; Wang, Xiaoke

2010-01-01

To evaluate the long-term effects of reforestation types on soil erosion on degraded land, vegetation and soil properties under conventional sloping farmland (CSF) and three different reforestation types including a Pinus massoniana secondary forest (PSF), an Eucommia ulmoides artificial economic forest (EEF) and a natural succession type forest (NST), were investigated at runoff plot scale over a six-year period in a red soil region of southern China. One hundred and thirty erosive rainfall events generating runoff in plots were grouped into four rainfall types by means of K-mean clustering method. Erosive rainfall type I is the dominant rainfall type. The amount of runoff and the soil loss under erosive rainfall type III were the most, followed by rain-fall type II, IV and I. Compared with CSF treatment, reforestation treatments decreased the average annual runoff depth and the soil loss by 25.5%-61.8% and 93.9%-96.2% during the study period respectively. Meanwhile, runoff depth at PSF and EEF treatments was significantly lower than that in NST treatment, but no significant difference existed in soil erosion modulus among the three reforestation treatments. This is mainly due to the improved vegetation properties (i.e., vegetation coverage, biomass of above- and below-ground and litter-fall mass) and soil properties (i.e., bulk density, total porosity, infiltration rate and organic carbon content) in the three reforestation treatments compared to CSF treatment. The PSF and EEF are recommended as the preferred reforestation types to control runoff and soil erosion in the red soil region of southern China, with the NST potentially being used as an important supplement.

Ajustement statistique des simulations climatiques : l'exemple des précipitations saisonnières de l'Amérique tropicaleStatistical adjustment of simulated climate: example of seasonal rainfall of tropical America.

NASA Astrophysics Data System (ADS)

Moron, Vincent; Navarra, Antonio

2000-05-01

This study presents the skill of the seasonal rainfall of tropical America from an ensemble of three 34-year general circulation model (ECHAM 4) simulations forced with observed sea surface temperature between 1961 and 1994. The skill gives a first idea of the amount of potential predictability if the sea surface temperatures are perfectly known some time in advance. We use statistical post-processing based on the leading modes (extracted from Singular Value Decomposition of the covariance matrix between observed and simulated rainfall fields) to improve the raw skill obtained by simple comparison between observations and simulations. It is shown that 36-55 % of the observed seasonal variability is explained by the simulations on a regional basis. Skill is greatest for Brazilian Nordeste (March-May), but also for northern South America or the Caribbean basin in June-September or northern Amazonia in September-November for example.

Optimal designs of bioretention cells in shallow groundwater

NASA Astrophysics Data System (ADS)

Zhang, K.; Chui, T. F. M.

2017-12-01

Bioretention cells, as one representative low impact development practices, have been proved to be effective in controlling surface runoff, removing pollutants and recharging groundwater. However, they are often not recommended in shallow groundwater areas due to potential groundwater pollution, reduction in runoff control performance and groundwater drainage through the underdrain. Most design guidelines only require a minimum distance between bioretention cell bottom and seasonal high groundwater table without guiding the design of bioretention cells to mitigate the problem of shallow groundwater. This study therefore proposed some design recommendations of bioretention cells for different rainfall runoff loads, native soil types and initial water table depths. A variably saturated flow model was employed to conduct event-based simulations on one single hypothetical bioretention cell in shallow groundwater, which was calibrated using experimental and simulation data of an on-site bioretention cell. A wide range of climatic and geophysical factors (i.e. initial groundwater depths, native soils, rainfall runoff loads) and bioretention designs (i.e. media soil types and underdrain sizes) were considered. Surface runoff reduction, time before groundwater mound formation, as well as maximum height of groundwater mound were evaluated. Less-permeable media types (i.e. sandy loam) are recommended in areas with many extreme rainfall events (i.e. 40 - 70 mm/h or larger) and of shallower groundwater, which can better protect groundwater from mounding and possibly contamination although may slightly compromise the runoff control performance. For areas having seasonal high groundwater table of 0 - 1 m below bioretention bottom, underdrain is recommended to maintain good infiltration capacity without draining groundwater. However, underdrain is not recommended for areas of groundwater table always near or above the bioretention bottom, only if an impermeable sheet is added. Generally, groundwater interference is a concern only when groundwater table is above 1 - 2.5 m below bioretention bottom and runoff loads are very high. The results of this study overall could benefit the implementation of bioretention cells in shallow groundwater areas, and the establishment of relevant design guidelines.

Assessment of two versions of regional climate model in simulating the Indian Summer Monsoon over South Asia CORDEX domain

NASA Astrophysics Data System (ADS)

Pattnayak, K. C.; Panda, S. K.; Saraswat, Vaishali; Dash, S. K.

2018-04-01

This study assess the performance of two versions of Regional Climate Model (RegCM) in simulating the Indian summer monsoon over South Asia for the period 1998 to 2003 with an aim of conducting future climate change simulations. Two sets of experiments were carried out with two different versions of RegCM (viz. RegCM4.2 and RegCM4.3) with the lateral boundary forcings provided from European Center for Medium Range Weather Forecast Reanalysis (ERA-interim) at 50 km horizontal resolution. The major updates in RegCM4.3 in comparison to the older version RegCM4.2 are the inclusion of measured solar irradiance in place of hardcoded solar constant and additional layers in the stratosphere. The analysis shows that the Indian summer monsoon rainfall, moisture flux and surface net downward shortwave flux are better represented in RegCM4.3 than that in the RegCM4.2 simulations. Excessive moisture flux in the RegCM4.2 simulation over the northern Arabian Sea and Peninsular India resulted in an overestimation of rainfall over the Western Ghats, Peninsular region as a result of which the all India rainfall has been overestimated. RegCM4.3 has performed well over India as a whole as well as its four rainfall homogenous zones in reproducing the mean monsoon rainfall and inter-annual variation of rainfall. Further, the monsoon onset, low-level Somali Jet and the upper level tropical easterly jet are better represented in the RegCM4.3 than RegCM4.2. Thus, RegCM4.3 has performed better in simulating the mean summer monsoon circulation over the South Asia. Hence, RegCM4.3 may be used to study the future climate change over the South Asia.

Blood, sweat, tears and success of technology transfer long-term controlled-release of herbicides: Root-growth-inhibiting biobarrier technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Voris, P.; Cataldo, D.A.; Burton, F.G.

Through the unique combination of polymers with a herbicidally active dinitroaniline, a cylinderical pellet (9mm long and 9mm in diameter) was developed that continuously releases a herbicide for a period of up to 100 years. Equilibrium concentration of the herbicide in soil adjacent to the pellet and the bioactive lifetime of the device cam be adjusted by changing the size of the pellet; the type of polymer; the type, quality, and quantity of carrier; and/or the concentration and type of dinitroaniline used. Commercial products that have been developed under a Federal Technology Transfer Program that utilize this technology include: (1)more » ROOT-SHIELD, a root repelling sewer gasket for concrete, clay, and PVC sewer lines, (2) BIOBARRIER, a spun-bonded polypropylene geotextile fabric developed to prevent root growth from invading septic tanks; penetrating under roadways, and along the edge of sidewalks, airport runways, and tennis courts, and for landscaped areas; and (3) ROOT-GUARD, a plastic drip irrigation emitter designed to protect buried drip irrigation systems from being plugged by roots. 17 refs., 4 figs., 6 tabs.« less

Planting Patterns and Deficit Irrigation Strategies to Improve Wheat Production and Water Use Efficiency under Simulated Rainfall Conditions

PubMed Central

Ali, Shahzad; Xu, Yueyue; Ma, Xiangcheng; Ahmad, Irshad; Kamran, Muhammad; Dong, Zhaoyun; Cai, Tie; Jia, Qianmin; Ren, Xiaolong; Zhang, Peng; Jia, Zhikuan

2017-01-01

The ridge furrow (RF) rainwater harvesting system is an efficient way to enhance rainwater accessibility for crops and increase winter wheat productivity in semi-arid regions. However, the RF system has not been promoted widely in the semi-arid regions, which primarily exist in remote hilly areas. To exploit its efficiency on a large-scale, the RF system needs to be tested at different amounts of simulated precipitation combined with deficit irrigation. Therefore, in during the 2015–16 and 2016–17 winter wheat growing seasons, we examined the effects of two planting patterns: (1) the RF system and (2) traditional flat planting (TF) with three deficit irrigation levels (150, 75, 0 mm) under three simulated rainfall intensity (1: 275, 2: 200, 3: 125 mm), and determined soil water storage profile, evapotranspiration rate, grain filling rate, biomass, grain yield, and net economic return. Over the two study years, the RF treatment with 200 mm simulated rainfall and 150 mm deficit irrigation (RF2150) significantly (P < 0.05) increased soil water storage in the depth of (200 cm); reduced ET at the field scale by 33%; increased total dry matter accumulation per plant; increased the grain-filling rate; and improved biomass (11%) and grain (19%) yields. The RF2150 treatment thus achieved a higher WUE (76%) and RIWP (21%) compared to TF. Grain-filling rates, grain weight of superior and inferior grains, and net economic profit of winter wheat responded positively to simulated rainfall and deficit irrigation under both planting patterns. The 200 mm simulated rainfall amount was more economical than other precipitation amounts, and led to slight increases in soil water storage, total dry matter per plant, and grain yield; there were no significant differences when the simulated rainfall was increased beyond 200 mm. The highest (12,593 Yuan ha−1) net income profit was attained using the RF system at 200 mm rainfall and 150 mm deficit irrigation, which also led to significantly higher grain yield, WUE, and RIWP than all other treatments. Thus, we recommend the RF2150 treatment for higher productivity, income profit, and improve WUE in the dry-land farming system of China. PMID:28878787

Drip tectonics and the enigmatic uplift of the Central Anatolian Plateau.

PubMed

Göğüş, Oğuz H; Pysklywec, Russell N; Şengör, A M C; Gün, Erkan

2017-11-16

Lithospheric drips have been interpreted for various regions around the globe to account for the recycling of the continental lithosphere and rapid plateau uplift. However, the validity of such hypothesis is not well documented in the context of geological, geophysical and petrological observations that are tested against geodynamical models. Here we propose that the folding of the Central Anatolian (Kırşehir) arc led to thickening of the lithosphere and onset of "dripping" of the arc root. Our geodynamic model explains the seismic data showing missing lithosphere and a remnant structure characteristic of a dripping arc root, as well as enigmatic >1 km uplift over the entire plateau, Cappadocia and Galatia volcanism at the southern and northern plateau margins since ~10 Ma, respectively. Models show that arc root removal yields initial surface subsidence that inverts >1 km of uplift as the vertical loading and crustal deformation change during drip evolution.

Coordinating management of water, salinity and trace elements for cotton under mulched drip irrigation with brackish water

NASA Astrophysics Data System (ADS)

Jin, M.; Chen, W.; Liang, X.

2016-12-01

Rational irrigation with brackish water can increase crop production, but irrational use may cause soil salinization. In order to understand the relationships among water, salt, and nutrient (including trace elements) and find rational schemes to manage water, salinity and nutrient in cotton fields, field and pot experiments were conducted in an arid area of southern Xinjiang, northwest China. Field experiments were performed from 2008 to 2015, and involved mulched drip irrigation during the growing season and flood irrigation afterwards. The average cotton yield of seven years varied between 3,575 and 5,095 kg/ha, and the irrigation water productivity between 0.91 and 1.16 kg/m3. With the progress of brackish water irrigation, Cu, Fe, Mn, and Na showed strong aggregation in topsoil at the narrow row, whereas the contents of Ca and K decreased in the order of inter-mulch gap, the wide inter row, and the narrow row. The contents of Cu, Fe, Mn, Ca and K in root soil reduced with cotton growth, whereas Na increased. Although mulched drip irrigation during the growing season resulted in an increase in salinity in the root zone, flood irrigation after harvesting leached the accumulated salts below background levels. Based on experiments a scheme for coordinating management of soil water, salt, and nutrient is proposed, that is, under the planting pattern of one mulch, two drip lines and four rows, the alternative irrigation plus a flood irrigation after harvesting or before seeding was the ideal scheme. Numerical simulations using solute transport model coupled with the root solute uptake based on the experiments and extended by another 20 years, suggest that the mulched drip irrigation using alternatively fresh and brackish water during the growing season and flood irrigation with fresh water after harvesting, is a sustainable irrigation practice that should not lead to soil salinization. Pot experiments with trace elements and different saline water showed significantly antagonistic effects on cotton growth and yield between NaCl and Mn or Zn or B. Zn concentration in irrigation water under salinity stress affected the uptake of nutrient elements and caused the different contents of nutrient elements in cotton, and influenced cotton growth and yields.

Continuous rainfall simulation for regional flood risk assessment - application in the Austrian Alps

NASA Astrophysics Data System (ADS)

Salinas, Jose Luis; Nester, Thomas; Komma, Jürgen; Blöschl, Günter

2017-04-01

Generation of realistic synthetic spatial rainfall is of pivotal importance for assessing regional hydroclimatic hazard as the input for long term rainfall-runoff simulations. The correct reproduction of the observed rainfall characteristics, such as regional intensity-duration-frequency curves, is necessary to adequately model the magnitude and frequency of the flood peaks. Furthermore, the replication of the observed rainfall spatial and temporal correlations allows to model important other hydrological features like antecedent soil moisture conditions before extreme rainfall events. In this work, we present an application in the Tirol region (Austrian alps) of a modification of the model presented by Bardossy and Platte (1992), where precipitation is modeled on a station basis as a mutivariate autoregressive model (mAr) in a Normal space, and then transformed to a Gamma-distributed space. For the sake of simplicity, the parameters of the Gamma distributions are assumed to vary monthly according to a sinusoidal function, and are calibrated trying to simultaneously reproduce i) mean annual rainfall, ii) mean daily rainfall amounts, iii) standard deviations of daily rainfall amounts, and iv) 24-hours intensity duration frequency curve. The calibration of the spatial and temporal correlation parameters is performed in a way that the intensity-duration-frequency curves aggregated at different spatial and temporal scales reproduce the measured ones. Bardossy, A., and E. J. Plate (1992), Space-time model for daily rainfall using atmospheric circulation patterns, Water Resour. Res., 28(5), 1247-1259, doi:10.1029/91WR02589.

Estimation of debris flow critical rainfall thresholds by a physically-based model

NASA Astrophysics Data System (ADS)

Papa, M. N.; Medina, V.; Ciervo, F.; Bateman, A.

2012-11-01

Real time assessment of debris flow hazard is fundamental for setting up warning systems that can mitigate its risk. A convenient method to assess the possible occurrence of a debris flow is the comparison of measured and forecasted rainfall with rainfall threshold curves (RTC). Empirical derivation of the RTC from the analysis of rainfall characteristics of past events is not possible when the database of observed debris flows is poor or when the environment changes with time. For landslides triggered debris flows, the above limitations may be overcome through the methodology here presented, based on the derivation of RTC from a physically based model. The critical RTC are derived from mathematical and numerical simulations based on the infinite-slope stability model in which land instability is governed by the increase in groundwater pressure due to rainfall. The effect of rainfall infiltration on landside occurrence is modelled trough a reduced form of the Richards equation. The simulations are performed in a virtual basin, representative of the studied basin, taking into account the uncertainties linked with the definition of the characteristics of the soil. A large number of calculations are performed combining different values of the rainfall characteristics (intensity and duration of event rainfall and intensity of antecedent rainfall). For each combination of rainfall characteristics, the percentage of the basin that is unstable is computed. The obtained database is opportunely elaborated to derive RTC curves. The methodology is implemented and tested on a small basin of the Amalfi Coast (South Italy).

Lattice Boltzmann method for rain-induced overland flow

NASA Astrophysics Data System (ADS)

Ding, Yu; Liu, Haifei; Peng, Yong; Xing, Liming

2018-07-01

Complex rainfall situations can generate overland flow with complex hydrodynamic characteristics, affecting the surface configuration (i.e. sheet erosion) and environment to varying degrees. Reliable numerical simulations can provide a scientific method for the optimization of environmental management. A mesoscopic numerical method, the lattice Boltzmann method, was employed to simulate overland flows. To deal with complex rainfall, two schemes were introduced to improve the lattice Boltzmann equation and the local equilibrium function, respectively. Four typical cases with differences in rainfall, bed roughness, and slopes were selected to test the accuracy and applicability of the proposed schemes. It was found that the simulated results were in good agreement with the experimental data, analytical values, and the results produced by other models.

Modeling effectiveness of management practices for flood mitigation using GIS spatial analysis functions in Upper Cilliwung watershed

NASA Astrophysics Data System (ADS)

Darma Tarigan, Suria

2016-01-01

Flooding is caused by excessive rainfall flowing downstream as cumulative surface runoff. Flooding event is a result of complex interaction of natural system components such as rainfall events, land use, soil, topography and channel characteristics. Modeling flooding event as a result of interaction of those components is a central theme in watershed management. The model is usually used to test performance of various management practices in flood mitigation. There are various types of management practices for flood mitigation including vegetative and structural management practices. Existing hydrological model such as SWAT and HEC-HMS models have limitation to accommodate discrete management practices such as infiltration well, small farm reservoir, silt pits in its analysis due to the lumped structure of these models. Aim of this research is to use raster spatial analysis functions of Geo-Information System (RGIS-HM) to model flooding event in Ciliwung watershed and to simulate impact of discrete management practices on surface runoff reduction. The model was validated using flooding data event of Ciliwung watershed on 29 January 2004. The hourly hydrograph data and rainfall data were available during period of model validation. The model validation provided good result with Nash-Suthcliff efficiency of 0.8. We also compared the RGIS-HM with Netlogo Hydrological Model (NL-HM). The RGIS-HM has similar capability with NL-HM in simulating discrete management practices in watershed scale.

Experimental study on influence of vegetation coverage on runoff in wind-water erosion crisscross region

NASA Astrophysics Data System (ADS)

Wang, Jinhua; Zhang, Ronggang; Sun, Juan

2018-02-01

Using artificial rainfall simulation method, 23 simulation experiments were carried out in water-wind erosion crisscross region in order to analyze the influence of vegetation coverage on runoff and sediment yield. The experimental plots are standard plots with a length of 20m, width of 5m and slope of 15 degrees. The simulation experiments were conducted in different vegetation coverage experimental plots based on three different rainfall intensities. According to the experimental observation data, the influence of vegetation coverage on runoff and infiltration was analyzed. Vegetation coverage has a significant impact on runoff, and the higher the vegetation coverage is, the smaller the runoff is. Under the condition of 0.6mm/min rainfall intensity, the runoff volume from the experimental plot with 18% vegetation coverage was 1.2 times of the runoff from the experimental with 30% vegetation coverage. What’s more, the difference of runoff is more obvious in higher rainfall intensity. If the rainfall intensity reaches 1.32mm/min, the runoff from the experimental plot with 11% vegetation coverage is about 2 times as large as the runoff from the experimental plot with 53%vegetation coverage. Under the condition of small rainfall intensity, the starting time of runoff in the experimental plot with higher vegetation coverage is later than that in the experimental plot with low vegetation coverage. However, under the condition of heavy rainfall intensity, there is no obvious difference in the beginning time of runoff. In addition, the higher the vegetation coverage is, the deeper the rainfall infiltration depth is.The results can provide reference for ecological construction carried out in wind erosion crisscross region with serious soil erosion.

Influence of development stage and disturbance of physical and biological soil crusts on soil water erosion

NASA Astrophysics Data System (ADS)

Chamizo, S.; Cantón, Y.; Lázaro, R.; Solé-Benet, A.; Calvo-Cases, A.; Miralles, I.; Domingo, F.

2009-04-01

Most soils exposed to rainfall are prone to sealing and crusting processes causing physical soil crusts (PSCs). When climate and soil stability conditions are suitable, PSCs can be consolidated by a complex community consisting of cyanobacteria, bacteria, green algae, microfungi, lichens and bryophytes, which are collectively known as biological soil crust (BSC). The influence of soil crusts on erosion processes is complex: crusts may reduce detachment, increasing soil stability and protecting soil against raindrop impact, although that protection will depend on the type of soil crust and the stage of development; they can also build up runoff, suggesting that downstream erosion may actually be increased or favoured water harvesting to vegetated areas. On the other hand, BSCs have been demonstrated to be very vulnerable to disturbance which in turn can lead to accelerate soil erosion and other forms of land degradation. Incorporation of the response of different type of soil crusts and the effects of their disturbance is highly likely to improve the prediction of runoff and water erosion models in arid and semi-arid catchments. The objective of this work is to analyse the erosional response of PSCs and BSCs in different stages of their development and subject to distinct disturbances when extreme rainfalls intensities are applied at plot scale in semiarid environments. Small plots on the most representative crust types, corresponding to different stages of crust development, in two semiarid ecosystems in SE Spain, El Cautivo (in the Tabernas Desert) and Amoladeras (in the Natural Park Cabo de Gata-Níjar), were selected and three disturbance treatments were applied on each crust type: a) no disturbance (control), b) trampling, stepping 100 times over the crust and c) scraping. Two consecutive rainfall simulation experiments (50 mm/h rainfall intensity) were carried out on each plot: the first on dry soil and the second, 30 minutes later, on wet soil conditions. Samples of runoff were collected regularly during the rainfall simulation and sediments in runoff extracted later in laboratory. Erosion rates were significantly different at both sites, being lower in Amoladeras than in El Cautivo due to a flatter topography and a higher infiltration capacity of the sandy soils with higher organic matter content. There were not significant differences on total erosion rates between the first and the second rainfall event, as consequence of the increase of runoff under wet conditions. In El Cautivo, the erosion rates significantly decreased as crust development stage increased. However, in Amoladeras, the erosion was low in all crust types and there were not significant differences on erosion rates among the crust development stages. Among treatments, in El Cautivo, scraping and trampling promoted significant higher erosion rates than undisturbed crust, but no significant differences were found between both treatments, except for the lichen-dominated crust. In Amoladeras, no significant differences on erosion rates between the undisturbed and the trampled crust were found since in this area trampling did not have an important effect. Although the removal of the crust in semiarid environments, at local scale, always increased erosion, the effects of crust disturbance on erosion varied depending on the ecosystem, with stronger erosional effects in badland areas with a silty substrate and steep topography than in areas with a flat topography and a coarser soil texture.

Assessment of a climate model to reproduce rainfall variability and extremes over Southern Africa

NASA Astrophysics Data System (ADS)

Williams, C. J. R.; Kniveton, D. R.; Layberry, R.

2010-01-01

It is increasingly accepted that any possible climate change will not only have an influence on mean climate but may also significantly alter climatic variability. A change in the distribution and magnitude of extreme rainfall events (associated with changing variability), such as droughts or flooding, may have a far greater impact on human and natural systems than a changing mean. This issue is of particular importance for environmentally vulnerable regions such as southern Africa. The sub-continent is considered especially vulnerable to and ill-equipped (in terms of adaptation) for extreme events, due to a number of factors including extensive poverty, famine, disease and political instability. Rainfall variability and the identification of rainfall extremes is a function of scale, so high spatial and temporal resolution data are preferred to identify extreme events and accurately predict future variability. The majority of previous climate model verification studies have compared model output with observational data at monthly timescales. In this research, the assessment of ability of a state of the art climate model to simulate climate at daily timescales is carried out using satellite-derived rainfall data from the Microwave Infrared Rainfall Algorithm (MIRA). This dataset covers the period from 1993 to 2002 and the whole of southern Africa at a spatial resolution of 0.1° longitude/latitude. This paper concentrates primarily on the ability of the model to simulate the spatial and temporal patterns of present-day rainfall variability over southern Africa and is not intended to discuss possible future changes in climate as these have been documented elsewhere. Simulations of current climate from the UK Meteorological Office Hadley Centre's climate model, in both regional and global mode, are firstly compared to the MIRA dataset at daily timescales. Secondly, the ability of the model to reproduce daily rainfall extremes is assessed, again by a comparison with extremes from the MIRA dataset. The results suggest that the model reproduces the number and spatial distribution of rainfall extremes with some accuracy, but that mean rainfall and rainfall variability is under-estimated (over-estimated) over wet (dry) regions of southern Africa.

Interannual Rainfall Variability in North-East Brazil: Observation and Model Simulation

NASA Astrophysics Data System (ADS)

Harzallah, A.; Rocha de Aragão, J. O.; Sadourny, R.

1996-08-01

The relationship between interannual variability of rainfall in north-east Brazil and tropical sea-surface temperature is studied using observations and model simulations. The simulated precipitation is the average of seven independent realizations performed using the Laboratoire de Météorologie Dynamique atmospheric general model forced by the 1970-1988 observed sea-surface temperature. The model reproduces very well the rainfall anomalies (correlation of 091 between observed and modelled anomalies). The study confirms that precipitation in north-east Brazil is highly correlated to the sea-surface temperature in the tropical Atlantic and Pacific oceans. Using the singular value decomposition method, we find that Nordeste rainfall is modulated by two independent oscillations, both governed by the Atlantic dipole, but one involving only the Pacific, the other one having a period of about 10 years. Correlations between precipitation in north-east Brazil during February-May and the sea-surface temperature 6 months earlier indicate that both modes are essential to estimate the quality of the rainy season.

Deciphering the expression of climate change within the Lower Colorado River basin by stochastic simulation of convective rainfall

NASA Astrophysics Data System (ADS)

Bliss Singer, Michael; Michaelides, Katerina

2017-10-01

In drylands, convective rainstorms typically control runoff, streamflow, water supply and flood risk to human populations, and ecological water availability at multiple spatial scales. Since drainage basin water balance is sensitive to climate, it is important to improve characterization of convective rainstorms in a manner that enables statistical assessment of rainfall at high spatial and temporal resolution, and the prediction of plausible manifestations of climate change. Here we present a simple rainstorm generator, STORM, for convective storm simulation. It was created using data from a rain gauge network in one dryland drainage basin, but is applicable anywhere. We employ STORM to assess watershed rainfall under climate change simulations that reflect differences in wetness/storminess, and thus provide insight into observed or projected regional hydrologic trends. Our analysis documents historical, regional climate change manifesting as a multidecadal decline in rainfall intensity, which we suggest has negatively impacted ephemeral runoff in the Lower Colorado River basin, but has not contributed substantially to regional negative streamflow trends.

Derivation of flood frequency curves in poorly gauged Mediterranean catchments using a simple stochastic hydrological rainfall-runoff model

NASA Astrophysics Data System (ADS)

Aronica, G. T.; Candela, A.

2007-12-01

SummaryIn this paper a Monte Carlo procedure for deriving frequency distributions of peak flows using a semi-distributed stochastic rainfall-runoff model is presented. The rainfall-runoff model here used is very simple one, with a limited number of parameters and practically does not require any calibration, resulting in a robust tool for those catchments which are partially or poorly gauged. The procedure is based on three modules: a stochastic rainfall generator module, a hydrologic loss module and a flood routing module. In the rainfall generator module the rainfall storm, i.e. the maximum rainfall depth for a fixed duration, is assumed to follow the two components extreme value (TCEV) distribution whose parameters have been estimated at regional scale for Sicily. The catchment response has been modelled by using the Soil Conservation Service-Curve Number (SCS-CN) method, in a semi-distributed form, for the transformation of total rainfall to effective rainfall and simple form of IUH for the flood routing. Here, SCS-CN method is implemented in probabilistic form with respect to prior-to-storm conditions, allowing to relax the classical iso-frequency assumption between rainfall and peak flow. The procedure is tested on six practical case studies where synthetic FFC (flood frequency curve) were obtained starting from model variables distributions by simulating 5000 flood events combining 5000 values of total rainfall depth for the storm duration and AMC (antecedent moisture conditions) conditions. The application of this procedure showed how Monte Carlo simulation technique can reproduce the observed flood frequency curves with reasonable accuracy over a wide range of return periods using a simple and parsimonious approach, limited data input and without any calibration of the rainfall-runoff model.

Potential sensitivity of warm season precipitation to urbanization extents: Modeling study in Beijing-Tianjin-Hebei urban agglomeration in China

NASA Astrophysics Data System (ADS)

Wang, Jun; Feng, Jinming; Yan, Zhongwei

2015-09-01

In this study, we investigated how different degrees of urbanization affect local and regional rainfall using high-resolution simulations based on the Weather Research and Forecasting Model. The extreme rainfall event of 21 July 2012 in Beijing was simulated for three representative urban land use distributions (no urbanization, early urbanization level of 1980, and recent urbanization level of 2009). Results suggest that urban modification of rainfall is potentially sensitive to urban land use condition. Rainfall was increased significantly over the downwind Beijing metropolis because of the effects of early urbanization; however, recent conditions of high urban development caused no significant increase. Further comparative analysis revealed that positive urban thermodynamical effects (i.e., urban warming, increased sensible heat transportation, and enhanced convergence and vertical motions) play major roles in urban modification of rainfall during the early urbanization stage. However, after cities expand to a certain extent (i.e., urban agglomeration), the regional moisture depression induced by the prevalence of impervious urban land has an effect on atmospheric instability energy, which might negate the city's positive impact on regional rainfall. Additional results from regional climate simulations for 10 Julys confirm this supposition. Given the explosive urban population growth and increasing demand for freshwater in cities, the potential negative effects of the urban environment on precipitation are worth investigation, particularly in rapidly developing countries and regions.

Difference infiltrometer: a method to measure temporally variable infiltration rates during rainstorms

USGS Publications Warehouse

Moody, John A.; Ebel, Brian A.

2012-01-01

We developed a difference infiltrometer to measure time series of non-steady infiltration rates during rainstorms at the point scale. The infiltrometer uses two, tipping bucket rain gages. One gage measures rainfall onto, and the other measures runoff from, a small circular plot about 0.5-m in diameter. The small size allows the infiltration rate to be computed as the difference of the cumulative rainfall and cumulative runoff without having to route water through a large plot. Difference infiltrometers were deployed in an area burned by the 2010 Fourmile Canyon Fire near Boulder, Colorado, USA, and data were collected during the summer of 2011. The difference infiltrometer demonstrated the capability to capture different magnitudes of infiltration rates and temporal variability associated with convective (high intensity, short duration) and cyclonic (low intensity, long duration) rainstorms. Data from the difference infiltrometer were used to estimate saturated hydraulic conductivity of soil affected by the heat from a wildfire. The difference infiltrometer is portable and can be deployed in rugged, steep terrain and does not require the transport of water, as many rainfall simulators require, because it uses natural rainfall. It can be used to assess infiltration models, determine runoff coefficients, identify rainfall depth or rainfall intensity thresholds to initiate runoff, estimate parameters for infiltration models, and compare remediation treatments on disturbed landscapes. The difference infiltrometer can be linked with other types of soil monitoring equipment in long-term studies for detecting temporal and spatial variability at multiple time scales and in nested designs where it can be linked to hillslope and basin-scale runoff responses.

Computational analysis of drop formation before and after the first singularity: the fate of free and satellite drops during simple dripping and DOD drop formation

NASA Astrophysics Data System (ADS)

Chen, Alvin U.; Basaran, Osman A.

2000-11-01

Drop formation from a capillary --- dripping mode --- or an ink jet nozzle --- drop-on-demand (DOD) mode --- falls into a class of scientifically challenging yet practically useful free surface flows that exhibit a finite time singularity, i.e. the breakup of an initially single liquid mass into two or more fragments. While computational tools to model such problems have been developed recently, they lack the accuracy needed to quantitatively predict all the dynamics observed in experiments. Here we present a new finite element method (FEM) based on a robust algorithm for elliptic mesh generation and remeshing to handle extremely large interface deformations. The new algorithm allows continuation of computations beyond the first singularity to track fates of both primary and any satellite drops. The accuracy of the computations is demonstrated by comparison of simulations with experimental measurements made possible with an ultra high-speed digital imager capable of recording 100 million frames per second.

Depth-dependent inactivation of Escherichia coli and Enterococcus faecalis in soil after manure application and simulated rainfall

USDA-ARS?s Scientific Manuscript database

E.coli and Enterococcus serve as important water quality indicator organisms. Rainfall action on manured fields and pastures releases these organisms into soil with infiltrating water. They can then be released back to runoff during subsequent rainfall or irrigation events as soil solution interacts...

Runoff and erosion response of simulated waste burial covers in a semi-arid environment

USGS Publications Warehouse

Bent, G.C.; Goff, B.F.; Rightmire, K.G.; Sidle, R.C.

1999-01-01

Control of runoff (reducing infiltration) and erosion at shallow land burials is necessary in order to assure environmentally safe disposal of low-level radioactive-waste and other waste products. This study evaluated the runoff and erosion response of two perennial grass species on simulated waste burial covers at Idaho National Engineering and Environmental Laboratory (INEEL). Rainfall simulations were applied to three plots covered by crested wheatgrass [Agropyron desertorum (Fischer ex Link) Shultes], three plots covered by streambank wheatgrass [Elymus lanceolatus (Scribner and Smith) Gould spp. lanceolatus], and one bare plot. Average total runoff for rainfall simulations in 1987, 1989, and 1990 was 42 percent greater on streambank wheatgrass plots than on crested wheatgrass plots. Average total soil loss for rainfall simulations in 1987 and 1990 was 105 percent greater on streambank wheatgrass plots than on crested wheatgrass plots. Total runoff and soil loss from natural rainfall and snowmelt events during 1987 were 25 and 105 percent greater, respectively, on streambank wheatgrass plots than on crested wheatgrass plots. Thus, crested wheatgrass appears to be better suited in revegetation of waste burial covers at INEEL than streambank wheatgrass due to its much lower erosion rate and only slightly higher infiltration rate (lower runoff rate).

Rainfall simulators - innovations seeking rainfall uniformity and automatic flow rate measurements

NASA Astrophysics Data System (ADS)

Bauer, Miroslav; Kavka, Petr; Strouhal, Luděk; Dostál, Tomáš; Krása, Josef

2016-04-01

Field rainfall simulators are used worldwide for many experimental purposes, such as runoff generation and soil erosion research. At CTU in Prague a laboratory simulator with swinging nozzles VeeJet has been operated since 2001. Since 2012 an additional terrain simulator is being used with 4 fixed FullJet 40WSQ nozzles with 2,4 m spacing and operating over two simultaneously sprinkled experimental plots sizing 8x2 and 1x1 m. In parallel to other research projects a specific problem was solved: improving rainfall spatial uniformity and overall intensity and surface runoff measurements. These fundamental variables significantly affect investigated processes as well as resulting water balance of the plot, therefore they need to be determined as accurately as possible. Although the original nozzles setting produced (commonly used) Christiansen uniformity index CU over 80 %, detailed measurements proved this index insufficient and showed many unrequired rainfall extremes within the plot. Moreover the number of rainfall intensity scenarios was limited and some of them required problematic multi-pressure operation of the water distribution system. Therefore the simulator was subjected to many substantial changes in 2015. Innovations ranged from pump intensification to control unit upgrade. As essential change was considered increase in number of nozzles to 9 in total and reducing their spacing to 1,2 m. However new uniformity measurements did not bring any significant improvement. Tested scenarios showed equal standard deviations of interpolated intensity rasters and equal or slightly lower CU index. Imperfections of sprinkling nozzles were found to be the limiting factor. Still many other benefits were brought with the new setup. Whole experimental plot 10x2 m is better covered with the rainfall while the water consumption is retained. Nozzles are triggered in triplets, which enables more rainfall intensity scenarios. Water distribution system is more stable due to single pressure operating mode, which is ensured by the pressure probe controlled electromagnetic valve. Previous experiments implied the need of automatic continuous measurements of selected variables. To this end the control unit was equipped with a datalogger. In a several seconds time step it collects the values of water pressure, nozzle-valves operation, control point rainfall intensity from a tipping bucket rain gauge, topsoil moisture from several Theta ML2x probes and most recently the plot outlet runoff rate. For a continuous runoff rate measurement a 0,4-foot HS-flume was constructed and equipped with S18U ultrasonic sensor. Assemble setting was optimised both in flow rate laboratory flume and in laboratory rainfall simulator. Namely the rating curves for particular flume bottom slopes were derived. Employment of the flume in the terrain is scheduled for the experimental season 2016, but laboratory results already show sufficient measurement accuracy and are promising in terms of experimental campaigns simplification. The abovementioned activities have been supported by the research grants SGS14/180/OHK1/3T/11, QJ1530181, QJ1520265 and QJ1330118.

Are revised models better models? A skill score assessment of regional interannual variability

NASA Astrophysics Data System (ADS)

Sperber, Kenneth R.; Participating AMIP Modelling Groups

1999-05-01

Various skill scores are used to assess the performance of revised models relative to their original configurations. The interannual variability of all-India, Sahel and Nordeste rainfall and summer monsoon windshear is examined in integrations performed under the experimental design of the Atmospheric Model Intercomparison Project. For the indices considered, the revised models exhibit greater fidelity at simulating the observed interannual variability. Interannual variability of all-India rainfall is better simulated by models that have a more realistic rainfall climatology in the vicinity of India, indicating the beneficial effect of reducing systematic model error.

Are revised models better models? A skill score assessment of regional interannual variability

NASA Astrophysics Data System (ADS)

Participating AMIP Modelling Groups,; Sperber, Kenneth R.

Various skill scores are used to assess the performance of revised models relative to their original configurations. The interannual variability of all-India, Sahel and Nordeste rainfall and summer monsoon windshear is examined in integrations performed under the experimental design of the Atmospheric Model Intercomparison Project. For the indices considered, the revised models exhibit greater fidelity at simulating the observed interannual variability. Interannual variability of all-India rainfall is better simulated by models that have a more realistic rainfall climatology in the vicinity of India, indicating the beneficial effect of reducing systematic model error.

Process-based rainfall interception by small trees in Northern China: The effect of rainfall traits and crown structure characteristics

Treesearch

Xiang Li; Qingfu Xiao; Jianzhi Niu; Salli Dymond; Natalie S. van Doorn; Xinxiao Yu; Baoyuan Xie; Xizhi Lv; Kebin Zhang; Jiao Li

2016-01-01

Rainfall interception by a tree's crown is one of the most important hydrological processes in an ecosystem, yet the mechanisms of interception are not well understood. A process-based experiment was conducted under five simulated rainfall intensities (from 10 to 150 mm h−1) to directly quantify tree crown interception and examine the effect...

An evaluation of the uncertainty of extreme events statistics at the WMO/CIMO Lead Centre on precipitation intensity

NASA Astrophysics Data System (ADS)

Colli, M.; Lanza, L. G.; La Barbera, P.

2012-12-01

Improving the quality of point-scale rainfall measurements is a crucial issue fostered in recent years by the WMO Commission for Instruments and Methods of Observation (CIMO) by providing recommendations on the standardization of equipment and exposure, instrument calibration and data correction as a consequence of various comparative campaigns involving manufacturers and national meteorological services from the participating countries. The WMO/CIMO Lead Centre on Precipitation Intensity (LC) was recently constituted, in a joint effort between the Dep. of Civil, Chemical and Environmental Engineering of the University of Genova and the Italian Air Force Met Service, gathering the considerable asset of data and information achieved by the past infield and laboratory campaigns with the aim of researching novel methodologies for improving the accuracy of rainfall intensity (RI) measurement techniques. Among the ongoing experimental activities carried out by the LC laboratory particular attention is paid to the reliability evaluation of extreme rainfall events statistics , a common tool in the engineering practice for urban and non urban drainage system design, based on real world observations obtained from weighing gauges. Extreme events statistics were proven already to be highly affected by the traditional tipping-bucket rain gauge RI measurement inaccuracy (La Barbera et al., 2002) and the time resolution of the available RI series certainly constitutes another key-factor in the reliability of the derived hyetographs. The present work reports the LC laboratory efforts in assembling a rainfall simulation system to reproduce the inner temporal structure of the rainfall process by means of dedicated calibration and validation tests. This allowed testing of catching type rain gauges under non-steady flow conditions and quantifying, in a first instance, the dynamic behaviour of the investigated instruments. Considerations about the influence of the dynamic response on the uncertainty budget of modern rain gauges is also shown . The analysis proceeds with the laboratory simulation of the annual maximum rainfall events recorded for different durations at the Villa Cambiaso meteo-station (University of Genova) over the last two decades. Results are reported and discussed in a comparative form involving the derived extreme events statistics. REFERENCES La Barbera P., Lanza L.G. and Stagi L. (2002). Influence of systematic mechanical errors of tipping-bucket rain gauges on the statistics of rainfall extremes. Water Sci. Techn., 45(2), 1-9. Colli M., Lanza L.G., and Chan P.W. (2011). Co-located tipping-bucket and optical drop counter RI measurements and a simulated correction algorithm, Atmos. Res., doi:10.1016/j.atmosres.2011.07.018 Colli M., Lanza L.G., La Barbera P. (2012). Weighing gauges measurement errors and the design rainfall for urban scale applications. 9th International workshop on precipitation in urban areas. St.Moritz, Switzerland, 6-9 December 2012 Lanza L.G. and Vuerich E. (2009). The WMO Field Intercomparison of Rain Intensity Gauges. Atmos. Res., 94, 534-543.

Censored rainfall modelling for estimation of fine-scale extremes

NASA Astrophysics Data System (ADS)

Cross, David; Onof, Christian; Winter, Hugo; Bernardara, Pietro

2018-01-01

Reliable estimation of rainfall extremes is essential for drainage system design, flood mitigation, and risk quantification. However, traditional techniques lack physical realism and extrapolation can be highly uncertain. In this study, we improve the physical basis for short-duration extreme rainfall estimation by simulating the heavy portion of the rainfall record mechanistically using the Bartlett-Lewis rectangular pulse (BLRP) model. Mechanistic rainfall models have had a tendency to underestimate rainfall extremes at fine temporal scales. Despite this, the simple process representation of rectangular pulse models is appealing in the context of extreme rainfall estimation because it emulates the known phenomenology of rainfall generation. A censored approach to Bartlett-Lewis model calibration is proposed and performed for single-site rainfall from two gauges in the UK and Germany. Extreme rainfall estimation is performed for each gauge at the 5, 15, and 60 min resolutions, and considerations for censor selection discussed.

Rainfall Across the Globe: Precipitation. The Role of Landmass in Monsoon Development. The Relationship Between Precipitation and Sea Surface Temperature on Decadal Time Scales

NASA Technical Reports Server (NTRS)

Chao, Winston; Schubert, Siegfried; Suarez, Max; Pegion, Philip

2000-01-01

The numerical simulation of precipitation helps scientists understand the complex mechanisms that determine how and why rainfall is distributed across the globe. Simulation aids in the development of forecastin,g efforts that inform policies regarding the management of water resources. Precipitation modeling also provides short-term warnings, for emergencies such as flash floods and mudslides. Just as precipitation modeling can warn of an impending abundance of rainfall, it can help anticipate the absence of rainfall in drought. What constitutes a drought? A meteorological drought simply means that an area is getting a significantly lower amount of rain than usual over a prolonged period of time and an agricultural drought is based on the level of soil moisture.

The potential for remote sensing and hydrologic modelling to assess the spatio-temporal dynamics of ponds in the Ferlo Region (Senegal)

NASA Astrophysics Data System (ADS)

Soti, V.; Puech, C.; Lo Seen, D.; Bertran, A.; Vignolles, C.; Mondet, B.; Dessay, N.; Tran, A.

2010-08-01

In the Ferlo Region in Senegal, livestock depend on temporary ponds for water but are exposed to the Rift Valley Fever (RVF), a disease transmitted to herds by mosquitoes which develop in these ponds. Mosquito abundance is related to the emptying and filling phases of the ponds, and in order to study the epidemiology of RVF, pond modelling is required. In the context of a data scarce region, a simple hydrologic model which makes use of remote sensing data was developed to simulate pond water dynamics from daily rainfall. Two sets of ponds were considered: those located in the main stream of the Ferlo Valley whose hydrological dynamics are essentially due to runoff, and the ponds located outside, which are smaller and whose filling mechanisms are mainly due to direct rainfall. Separate calibrations and validations were made for each set of ponds. Calibration was performed from daily field data (rainfall, water level) collected during the 2001 and 2002 rainy seasons and from three different sources of remote sensing data: 1) very high spatial resolution optical satellite images to access pond location and surface area at given dates, 2) Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Digital Elevation Model (DEM) data to estimate pond catchment area and 3) Tropical Rainfall Measuring Mission (TRMM) data for rainfall estimates. The model was applied to all ponds of the study area, the results were validated and a sensitivity analysis was performed. Water height simulations using gauge rainfall as input were compared to water level measurements from four ponds and Nash coefficients >0.7 were obtained. Comparison with simulations using TRMM rainfall data gave mixed results, with poor water height simulations for the year 2001 and good estimations for the year 2002. A pond map derived from a Quickbird satellite image was used to assess model accuracy for simulating pond water areas for all the ponds of the study area. The validation showed that modelled water areas were mostly underestimated but significantly correlated, particularly for the larger ponds. The results of the sensitivity analysis showed that parameters relative to pond shape and catchment area estimation have less effects on model simulation than parameters relative to soil properties (rainfall threshold causing runoff in dry soils and the coefficient expressing soil moisture decrease with time) or the water loss coefficient. Overall, our results demonstrate the possibility of using a simple hydrologic model with remote sensing data to track pond water heights and water areas in a homogeneous arid area.

Mulch your tomatoes to fight weeds, retain soil moisture and save money

USDA-ARS?s Scientific Manuscript database

An on-farm experiment was conducted to determine whether different types of mulches were a cost-effective means of weed management in organic tomato production. Three mulch treatment, bare soil, straw and grass, were applied to drip-irrigated tomatoes at a depth of 7.5 cm. Weed biomass was reduced s...

Impact of the 2015/2016 El Niño event on rainwater and cave dripwater isotopes in Northern Borneo

NASA Astrophysics Data System (ADS)

Ellis, S. A.; Cobb, K. M.; Moerman, J. W.; Bennett, A. L.; Gerstner, H.; Malang, J.; Wong, C. I.

2017-12-01

Paleoclimate reconstructions of past hydrological variability are primarily comprised of water isotope timeseries, and vastly extend sparse instrumental precipitation data from many key areas of the world. At Gunung Mulu National Park in Northern Borneo (4N 115E), stalagmite oxygen isotope (δ18O) records provide a view of western tropical Pacific hydroclimate across much of the last 500,000 years [Partin et al. 2007, Carolin et al. 2013, 2016] including a recent study of past ENSO extremes across the Holocene [Chen et al. 2016]. The climatic interpretation of the N. Borneo stalagmite δ18O records is based on analysis of a 6.5-yr-long timeseries of daily rainfall δ18O, and companion timeseries of cave dripwater δ18O from Gunung Mulu [Moerman et al. 2013, 2014]. Taken together, these studies demonstrate rainfall δ18O acts as a robust proxy for regional convective activity (via the amount effect), which is transmitted into the caves over a period of 2-10 months. However, these findings are highly dependent on the magnitude of the observed changes during the study period, which did not include a strong El Nino event. Here we present an extension of the world's longest running daily rainfall δ18O time series and biweekly cave dripwater δ18O timeseries to span the period from 2012 to 2017, creating an 11-yr-long timeseries for analysis of climatic and karst influences on observed rainwater and dripwater δ18O. Most notably, our new time series captures the very strong 2015/2016 El Niño event. Dramatic reductions in rainfall at Mulu ( 25% across DJF) were accompanied by a 6‰ increase in rainfall δ18O. Cave dripwaters also record the influence of 2015/2016 El Niño event through significantly reduced drip rates as well as 2-4‰, increases in dripwater δ18O. We present compelling evidence that dripwater residence times vary across the expanded time-series - most notably during the 2015/2016 El Niño event. Our results carry important implications for the interpretation of high-resolution stalagmite δ18O timeseries from our site as well as other stalagmite reconstruction sites around the world, given that most studies assume a relatively constant dripwater residence time.

The influence of El Niño-Southern Oscillation regimes on eastern African vegetation and its future implications under the RCP8.5 warming scenario

NASA Astrophysics Data System (ADS)

Fer, Istem; Tietjen, Britta; Jeltsch, Florian; Wolff, Christian

2017-09-01

The El Niño-Southern Oscillation (ENSO) is the main driver of the interannual variability in eastern African rainfall, with a significant impact on vegetation and agriculture and dire consequences for food and social security. In this study, we identify and quantify the ENSO contribution to the eastern African rainfall variability to forecast future eastern African vegetation response to rainfall variability related to a predicted intensified ENSO. To differentiate the vegetation variability due to ENSO, we removed the ENSO signal from the climate data using empirical orthogonal teleconnection (EOT) analysis. Then, we simulated the ecosystem carbon and water fluxes under the historical climate without components related to ENSO teleconnections. We found ENSO-driven patterns in vegetation response and confirmed that EOT analysis can successfully produce coupled tropical Pacific sea surface temperature-eastern African rainfall teleconnection from observed datasets. We further simulated eastern African vegetation response under future climate change as it is projected by climate models and under future climate change combined with a predicted increased ENSO intensity. Our EOT analysis highlights that climate simulations are still not good at capturing rainfall variability due to ENSO, and as we show here the future vegetation would be different from what is simulated under these climate model outputs lacking accurate ENSO contribution. We simulated considerable differences in eastern African vegetation growth under the influence of an intensified ENSO regime which will bring further environmental stress to a region with a reduced capacity to adapt effects of global climate change and food security.

Aerosol and Urban Land Use Effect on Rainfall Around Cities in Indo-Gangetic Basin From Observations and Cloud Resolving Model Simulations

NASA Astrophysics Data System (ADS)

Sarangi, Chandan; Tripathi, S. N.; Qian, Yun; Kumar, Shailendra; Ruby Leung, L.

2018-04-01

Coupling of urban land use land cover (LULC) and aerosol loading on rainfall around cities in the Gangetic Basin (GB) is examined here. Long-term observations illustrate more rainfall at urban core and climatological downwind regions compared to the upwind regions of Kanpur, a metropolitan area located in central GB. In addition, analysis of a 15 day cloud resolving simulation using the Weather Research and Forecasting model also illustrated similar rainfall pattern around other major cities in the GB. Interestingly, the enhancement of downwind rainfall was greater than that over urban regions, and it was positively associated with both the urban area of the city and ambient aerosol loading during the propagating storm. Further, to gain a process-level understanding, a typical storm that propagated northwestward across Kanpur was simulated using Weather Research and Forecasting under three different scenarios. Case 1 has realistic LULC representation of Kanpur, while the grids representing the Kanpur urban region were replaced by cropland LULC pattern in Case 2. Comparison illustrated that urban heat island effect caused convergence of winds and moisture in the lower troposphere, which enhances convection over urban region and induced more rainfall over the urban core compared to upwind regions. Case 3 is similar to Case 1 but lower aerosol concentration (by a factor of 100) over the storm region. Analysis shows that aerosol-induced microphysical changes delay the initiation of warm rain (over the upwind region) but enhance ice phase particle formation in latter stages (over the urban and downwind regions) resulting in increase in downwind rainfall.

Convective Systems Over the South China Sea: Cloud-Resolving Model Simulations

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Shie, C.-L.; Johnson, D.; Simpson, J.; Braun, S.; Johnson, R.; Ciesielski, P. E.; Starr, David OC. (Technical Monitor)

2002-01-01

The South China Sea Monsoon Experiment (SCSMEX) was conducted in May-June 1998. One of its major objectives is to better understand the key physical processes for the onset and evolution of the summer monsoon over Southeast Asia and southern China. Multiple observation platforms (e.g., upper-air soundings, Doppler radar, ships, wind profilers, radiometers, etc.) during SCSMEX provided a first attempt at investigating the detailed characteristics of convective storms and air pattern changes associated with monsoons over the South China Sea region. SCSMEX also provided rainfall estimates which allows for comparisons with those obtained from the Tropical Rainfall Measuring Mission (TRMM), a low earth orbit satellite designed to measure rainfall from space. The Goddard Cumulus Ensemble (GCE) model (with 1-km grid size) is used to understand and quantify the precipitation processes associated with the summer monsoon over the South China Sea. This is the first (loud-resolving model used to simulate precipitation processes in this particular region. The GCE-model results captured many of the observed precipitation characteristics because it used a fine grid size. For example, the temporal variation of the simulated rainfall compares quite well to the sounding-estimated rainfall variation. The time and domain-averaged temperature (heating/cooling) and water vapor (drying/ moistening) budgets are in good agreement with observations. The GCE-model-simulated rainfall amount also agrees well with TRMM rainfall data. The results show there is more evaporation from the ocean surface prior to the onset of the monsoon than after the on-et of monsoon when rainfall increases. Forcing due to net radiation (solar heating minus longwave cooling) is responsible for about 25% of the precipitation in SCSMEX The transfer of heat from the ocean into the atmosphere does not contribute significantly to the rainfall in SCSMEX. Model sensitivity tests indicated that total rain production is reduced 17-18% in runs neglecting the ice phase. The SCSMEX results are compared to other GCE-model-simulated weather systems that developed during other field campaigns (i.e., west Pacific warm pool region, eastern Atlantic region and central USA). Large-scale forcing vie temperature and water vapor tendency, is the major energy source for net condensation in the tropical cases. The effects of large-scale cooling exceed that of large-scale moistening in the west pacific warm pool region and eastern Atlantic region. For SCSMEX, however, the effects of large-scale moistening predominate. Net radiation and sensible and latent hc,it fluxes play a much more important role in the central USA.

Rainfall continuous time stochastic simulation for a wet climate in the Cantabric Coast

NASA Astrophysics Data System (ADS)

Rebole, Juan P.; Lopez, Jose J.; Garcia-Guzman, Adela

2010-05-01

Rain is the result of a series of complex atmospheric processes which are influenced by numerous factors. This complexity makes its simulation practically unfeasible from a physical basis, advising the use of stochastic diagrams. These diagrams, which are based on observed characteristics (Todorovic and Woolhiser, 1975), allow the introduction of renewal alternating processes, that account for the occurrence of rainfall at different time lapses (Markov chains are a particular case, where lapses can be described by exponential distributions). Thus, a sequential rainfall process can be defined as a temporal series in which rainfall events (periods in which rainfall is recorded) alternate with non rain events (periods in which no rainfall is recorded). The variables of a temporal rain sequence have been characterized (duration of the rainfall event, duration of the non rainfall event, average intensity of the rain in the rain event, and a temporal distribution of the amount of rain in the rain event) in a wet climate such as that of the coastal area of Guipúzcoa. The study has been performed from two series recorded at the meteorological stations of Igueldo-San Sebastián and Fuenterrabia / Airport (data every ten minutes and for its hourly aggregation). As a result of this work, the variables satisfactorily fitted the following distribution functions: the duration of the rain event to a exponential function; the duration of the dry event to a truncated exponential mixed distribution; the average intensity to a Weibull distribution; and the distribution of the rain fallen to the Beta distribution. The characterization was made for an hourly aggregation of the recorded interval of ten minutes. The parameters of the fitting functions were better obtained by means of the maximum likelihood method than the moment method. The parameters obtained from the characterization were used to develop a stochastic rainfall process simulation model by means of a three states Markov chain (Hutchinson, 1990), performed in an hourly basis by García-Guzmán (1993) and Castro et al. (1997, 2005 ). Simulation process results were valid in the hourly case for all the four described variables, with a slightly better response in Fuenterrabia than in Igueldo. In summary, all the variables were better simulated in Fuenterrabia than in Igueldo. Fuenterrabia data series is shorter and with longer sequences without missing data, compared to Igueldo. The latter shows higher number of missing data events, whereas its mean duration is longer in Fuenterrabia.

Soil erosion predictions from a landscape evolution model - An assessment of a post-mining landform using spatial climate change analogues.

PubMed

Hancock, G R; Verdon-Kidd, D; Lowry, J B C

2017-12-01

Landscape Evolution Modelling (LEM) technologies provide a means by which it is possible to simulate the long-term geomorphic stability of a conceptual rehabilitated landform. However, simulations rarely consider the potential effects of anthropogenic climate change and consequently risk not accounting for the range of rainfall variability that might be expected in both the near and far future. One issue is that high resolution (both spatial and temporal) rainfall projections incorporating the potential effects of greenhouse forcing are required as input. However, projections of rainfall change are still highly uncertain for many regions, particularly at sub annual/seasonal scales. This is the case for northern Australia, where a decrease or an increase in rainfall post 2030 is considered equally likely based on climate model simulations. The aim of this study is therefore to investigate a spatial analogue approach to develop point scale hourly rainfall scenarios to be used as input to the CAESAR - Lisflood LEM to test the sensitivity of the geomorphic stability of a conceptual rehabilitated landform to potential changes in climate. Importantly, the scenarios incorporate the range of projected potential increase/decrease in rainfall for northern Australia and capture the expected envelope of erosion rates and erosion patterns (i.e. where erosion and deposition occurs) over a 100year modelled period. We show that all rainfall scenarios produce sediment output and gullying greater than that of the surrounding natural system, however a 'wetter' future climate produces the highest output. Importantly, incorporating analogue rainfall scenarios into LEM has the capacity to both improve landform design and enhance the modelling software. Further, the method can be easily transferred to other sites (both nationally and internationally) where rainfall variability is significant and climate change impacts are uncertain. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.

North Pacific Westerly Jet Influence of the Winter Hawaii Rainfall in the last 21,000 years

NASA Astrophysics Data System (ADS)

Li, S.; Elison Timm, O.

2017-12-01

Hawaii rainfall has a strong seasonality which has more rainfall during the winter than summer. Part of the winter rainfall is from extratropical weather disturbances. Kona lows (KL) are important contributors to the annual rainfall budget of the Hawaiian Islands. KL activity is found to have a strong relationship with the North Pacific climate variability. The goal of the research is to test the hypothesis that changes in the strength and position of the upper level zonal wind jet is a key driver for regional rainfall changes. The main objectives are (1) to identify the relationship between North Pacific westerly jet strength and KL activity in present day climate, (2) to test the stability of this relationship under past climatic conditions, and (3) to explore the teleconnection between Hawaii and North America. For the present-day analysis of the westerly jet, the zonal wind at 250hPa is used from ERA-interim data from 1979-2014. The potential vorticity is used as a measure of extratropical synoptic activity. The Hawaii Rainfall Index is from the Rainfall Atlas of Hawaii (seasonal means, 1920-2012). For the paleoclimatic study, the transient TraCE-21ka simulation is used for the zonal wind - Hawaii rainfall analysis. The results of present-day analysis show that when the jet extends farther into the eastern Pacific sector the Kona Low activity is reduced, less winter rainfall is observed over Hawaii and more rainfall over the California region. The jet position-rainfall relationship was investigated within the TrACE-21 simulation. For the TraCE-21ka dataset, there is an increasing rainfall trend from 21kBP to 14kBP; this period coincides with a gradual decrease in the strength of the westerly wind jet. The results show that the westerly jet strength has a strong influence of the Kona Low activity and the rainfall over Hawaii both in the present and the past.

Identification of deficiencies in seasonal rainfall simulated by CMIP5 climate models

NASA Astrophysics Data System (ADS)

Dunning, Caroline M.; Allan, Richard P.; Black, Emily

2017-11-01

An objective technique for analysing seasonality, in terms of regime, progression and timing of the wet seasons, is applied in the evaluation of CMIP5 simulations across continental Africa. Atmosphere-only and coupled integrations capture the gross observed patterns of seasonal progression and give mean onset/cessation dates within 18 days of the observational dates for 11 of the 13 regions considered. Accurate representation of seasonality over central-southern Africa and West Africa (excluding the southern coastline) adds credence for future projected changes in seasonality here. However, coupled simulations exhibit timing biases over the Horn of Africa, with the long rains 20 days late on average. Although both sets of simulations detect biannual rainfall seasonal cycles for East and Central Africa, coupled simulations fail to capture the biannual regime over the southern West African coastline. This is linked with errors in the Gulf of Guinea sea surface temperature (SST) and deficient representation of the SST/rainfall relationship.

A simple stochastic rainstorm generator for simulating spatially and temporally varying rainfall

NASA Astrophysics Data System (ADS)

Singer, M. B.; Michaelides, K.; Nichols, M.; Nearing, M. A.

2016-12-01

In semi-arid to arid drainage basins, rainstorms often control both water supply and flood risk to marginal communities of people. They also govern the availability of water to vegetation and other ecological communities, as well as spatial patterns of sediment, nutrient, and contaminant transport and deposition on local to basin scales. All of these landscape responses are sensitive to changes in climate that are projected to occur throughout western North America. Thus, it is important to improve characterization of rainstorms in a manner that enables statistical assessment of rainfall at spatial scales below that of existing gauging networks and the prediction of plausible manifestations of climate change. Here we present a simple, stochastic rainstorm generator that was created using data from a rich and dense network of rain gauges at the Walnut Gulch Experimental Watershed (WGEW) in SE Arizona, but which is applicable anywhere. We describe our methods for assembling pdfs of relevant rainstorm characteristics including total annual rainfall, storm area, storm center location, and storm duration. We also generate five fitted intensity-duration curves and apply a spatial rainfall gradient to generate precipitation at spatial scales below gauge spacing. The model then runs by Monte Carlo simulation in which a total annual rainfall is selected before we generate rainstorms until the annual precipitation total is reached. The procedure continues for decadal simulations. Thus, we keep track of the hydrologic impact of individual storms and the integral of precipitation over multiple decades. We first test the model using ensemble predictions until we reach statistical similarity to the input data from WGEW. We then employ the model to assess decadal precipitation under simulations of climate change in which we separately vary the distribution of total annual rainfall (trend in moisture) and the intensity-duration curves used for simulation (trends in storminess). We demonstrate the model output through spatial maps of rainfall and through statistical comparisons of relevant parameters and distributions. Finally, discuss how the model can be used to understand basin-scale hydrology in terms of soil moisture, runoff, and erosion.

Dynamical downscaling of historical climate over CORDEX East Asia domain: A comparison of regional ocean-atmosphere coupled model to stand-alone RCM simulations

NASA Astrophysics Data System (ADS)

Zou, Liwei; Zhou, Tianjun; Peng, Dongdong

2016-02-01

The FROALS (flexible regional ocean-atmosphere-land system) model, a regional ocean-atmosphere coupled model, has been applied to the Coordinated Regional Downscaling Experiment (CORDEX) East Asia domain. Driven by historical simulations from a global climate system model, dynamical downscaling for the period from 1980 to 2005 has been conducted at a uniform horizontal resolution of 50 km. The impacts of regional air-sea couplings on the simulations of East Asian summer monsoon rainfall have been investigated, and comparisons have been made to corresponding simulations performed using a stand-alone regional climate model (RCM). The added value of the FROALS model with respect to the driving global climate model was evident in terms of both climatology and the interannual variability of summer rainfall over East China by the contributions of both the high horizontal resolution and the reasonably simulated convergence of the moisture fluxes. Compared with the stand-alone RCM simulations, the spatial pattern of the simulated low-level monsoon flow over East Asia and the western North Pacific was improved in the FROALS model due to its inclusion of regional air-sea coupling. The results indicated that the simulated sea surface temperature (SSTs) resulting from the regional air-sea coupling were lower than those derived directly from the driving global model over the western North Pacific north of 15°N. These colder SSTs had both positive and negative effects. On the one hand, they strengthened the western Pacific subtropical high, which improved the simulation of the summer monsoon circulation over East Asia. On the other hand, the colder SSTs suppressed surface evaporation and favored weaker local interannual variability in the SST, which led to less summer rainfall and weaker interannual rainfall variability over the Korean Peninsula and Japan. Overall, the reference simulation performed using the FROALS model is reasonable in terms of rainfall over the land area of East Asia and will become the basis for the generation of climate change scenarios for the CORDEX East Asia domain that will be described in future reports.

Wet season water distribution in a tropical Andean cloud forest of Boyacá (Colombia) during the dry climate of El Niño

NASA Astrophysics Data System (ADS)

Garcia-Santos, G.; Berdugo, M. B.

2010-07-01

Fog has been demonstrated as the only source of moisture during the dry climate of El Niño in the tropical Andean cloud forest of Boyacá region in Colombia, yet its importance for the forest is virtually unknown. We assessed fog water distribution during the wet season inside the forest and outside in a practically deforested area. Water intercepted by plant was measured at different vertical stratus. Soil moisture in the first centimetres was also measured. During the anomalous drier wet season there was lack of rainfall and the total recorded cloud water was lower compared with the same period during the previous year. Our results indicated that the upper part of the forest mass intercepts most of the fog water compared with lower stratus when the fog event starts. However upper most stratus became rapidly drier after the event, which is explained because water is released to the atmosphere due to high heat atmosphere-leaves interface fluctuations caused by wind and solar radiation, flows towards a different water potential and drips from the leaves. Low amount of fog dripped from tree foliage into the soil, indicating a large water storage capacity of the epiphyte and bryophyte vegetation. Despite the small amount of throughfall, understory vegetation and litter remained wet, which might be explained by the water flowing through the epiphyte vegetation or the high capacity of the understory to absorb moisture from the air. Soil water did not infiltrate in depth, which underlines the importance of fog as water and cool source for seedling growth and shallow rooted understory species, especially during drier conditions.

Competing effects of groundwater withdrawals and climate change on water availability in semi-arid India

NASA Astrophysics Data System (ADS)

Sishodia, R. P.; Shukla, S.

2017-12-01

India, a global leader in groundwater use (250 km3/yr), is experiencing groundwater depletion. There has been a 130-fold increase in number of irrigation wells since 1960. Anticipated future increase in groundwater demand is likely to exacerbate the water availability in the semi-arid regions of India. Depending on the direction of change, future climate change may either worsen or enhance the water availability. This study uses an integrated hydrologic modeling approach (MIKE SHE MIKE 11) to compare and combine the effects of future (2040-2069) increased groundwater withdrawals and climate change on surface and groundwater flows and availability for an agricultural watershed in semi-arid south India. Modeling results showed that increased groundwater withdrawals in the future resulted in reduced surface flows (25%) and increased frequency and duration (90 days/yr) of well drying. In contrast, projected future increase in rainfall (7-43%) under the changed climate showed increased groundwater recharge (15-67%) and surface flows (9-155%). Modeling results suggest that the positive effects of climate change may enhance the water availability in this semi-arid region of India. However, in combination with increased withdrawals, climate change was shown to increase the well drying and reduce the water availability especially during dry years. A combination of management options such as flood to drip conversion, energy subsidy reductions and water storage can support increased groundwater irrigated area in the future while mitigating the well drying. A cost-benefit analysis showed that dispersed water storage and flood to drip conversion can be highly cost-effective in this semi-arid region. The study results suggest that the government and management policies need to be focused towards an integrated management of demand and supply to create a sustainable food-water-energy nexus in the region.

A Stand-Alone Demography and Landscape Structure Module for Earth System Models: Integration with Inventory Data from Temperate and Boreal Forests

NASA Astrophysics Data System (ADS)

Hess, L.; Basso, B.; Hinckley, E. L. S.; Robertson, G. P.; Matson, P. A.

2014-12-01

In the coming century, the proportion of total rainfall that falls in heavy storm events is expected to increase in many areas, especially in the US Midwest, a major agricultural region. These changes in rainfall patterns may have consequences for hydrologic flow and nutrient losses, especially in agricultural soils, with potentially negative consequences for receiving ground- and surface waters. We used a tracer experiment to examine how more extreme rainfall patterns may affect the movement of water and solutes through an agricultural soil profile in the upper Midwest, and to what extent tillage may moderate these effects. Two rainfall patterns were created with 5m x 5m rainout shelters at the Kellogg Biological Station LTER site in replicated plots with either conventional tillage or no-till management. Control rainfall treatments received water 3x per week, and extreme rainfall treatments received the same total amount of water but once every two weeks, to simulate less frequent but larger storms. In April 2015, potassium bromide (KBr) was added as a conservative tracer of water flow to all plots, and Br- concentrations in soil water at 1.2m depth were measured weekly from April through July. Soil water Br- concentrations increased and peaked more quickly under the extreme rainfall treatment, suggesting increased infiltration and solute transfer to depth compared to soils exposed to control rainfall patterns. Soil water Br- also increased and peaked more quickly in no-till than in conventional tillage treatments, indicating differences in flow paths between management systems. Soil moisture measured every 15 minutes at 10, 40, and 100cm depths corroborates tracer experiment results: rainfall events simulated in extreme rainfall treatments led to large increases in deep soil moisture, while the smaller rainfall events simulated under control conditions did not. Deep soil moisture in no-till treatments also increased sooner after water application as compared to in conventional soils. Our results suggest that exposure to more extreme rainfall patterns will likely increase infiltration depth and nutrient losses in agricultural soils. In particular, soils under no-till management, which leads to development of preferential flow paths, may be particularly vulnerable to vertical nutrient losses.

Controlling factors for infiltration on undisturbed hillslopes in unmanaged plantation forests

NASA Astrophysics Data System (ADS)

Hiraoka, Marino; Onda, Yuichi; Gomi, Takashi; Mizugaki, Shigeru; Nanko, Kazuki; Kato, Hiroaki

2017-04-01

Infiltration into the soil is a crucial factor for predicting overland flow generation. Infiltration capacity strongly relates to ground vegetation, soil characteristics, or both. For revealing controlling factors for infiltration capacity, we conducted in-situ rainfall simulation using an oscillating-nozzle type rainfall simulator at 26 plots with different ground cover conditions of unmanaged Japanese cypress (Chamaecyparis obtusa) plantations. For wide-ranging vegetation cover condition (0-100%), infiltration capacity widely varied (5-322 mm/h) and had positive correlations with indices of ground vegetation and ground litter (p < 0.01). For a limited vegetation cover condition (0-20%), the range of infiltration capacity (7-114 mm/h) was associated with ground litter thickness (p < 0.05), and difference in soil organic matter and difference in soil bulk density. Principal component analysis showed that the first and second principal components (70% of total variation) related to changes in above- and below-ground biomass and changes in pores in soil. Our findings showed that development of ground vegetation alters hydrological processes of surface soil through changes in soil characteristics via the propagation of belowground biomass development.

Rainfall variability and extremes over southern Africa: assessment of a climate model to reproduce daily extremes

NASA Astrophysics Data System (ADS)

Williams, C.; Kniveton, D.; Layberry, R.

2009-04-01

It is increasingly accepted that that any possible climate change will not only have an influence on mean climate but may also significantly alter climatic variability. A change in the distribution and magnitude of extreme rainfall events (associated with changing variability), such as droughts or flooding, may have a far greater impact on human and natural systems than a changing mean. This issue is of particular importance for environmentally vulnerable regions such as southern Africa. The subcontinent is considered especially vulnerable to and ill-equipped (in terms of adaptation) for extreme events, due to a number of factors including extensive poverty, famine, disease and political instability. Rainfall variability and the identification of rainfall extremes is a function of scale, so high spatial and temporal resolution data are preferred to identify extreme events and accurately predict future variability. The majority of previous climate model verification studies have compared model output with observational data at monthly timescales. In this research, the assessment of ability of a state of the art climate model to simulate climate at daily timescales is carried out using satellite derived rainfall data from the Microwave Infra-Red Algorithm (MIRA). This dataset covers the period from 1993-2002 and the whole of southern Africa at a spatial resolution of 0.1 degree longitude/latitude. The ability of a climate model to simulate current climate provides some indication of how much confidence can be applied to its future predictions. In this paper, simulations of current climate from the UK Meteorological Office Hadley Centre's climate model, in both regional and global mode, are firstly compared to the MIRA dataset at daily timescales. This concentrates primarily on the ability of the model to simulate the spatial and temporal patterns of rainfall variability over southern Africa. Secondly, the ability of the model to reproduce daily rainfall extremes will be assessed, again by a comparison with extremes from the MIRA dataset.

Effects of episodic rainfall on a subterranean estuary

NASA Astrophysics Data System (ADS)

Yu, Xiayang; Xin, Pei; Lu, Chunhui; Robinson, Clare; Li, Ling; Barry, D. A.

2017-07-01

Numerical simulations were conducted to examine the effect of episodic rainfall on nearshore groundwater dynamics in a tidally influenced unconfined coastal aquifer, with a focus on both long-term (yearly) and short-term (daily) behavior of submarine groundwater discharge (SGD) and seawater intrusion (SWI). The results showed nonlinear interactions among the processes driven by rainfall, tides, and density gradients. Rainfall-induced infiltration increased the yearly averaged fresh groundwater discharge to the ocean but reduced the extents of the saltwater wedge and upper saline plume as well as the total rate of seawater circulation through both zones. Overall, the net effect of the interactions led to an increase of the SGD. The nearshore groundwater responded to individual rainfall events in a delayed and cumulative fashion, as evident in the variations of daily averaged SGD and salt stored in the saltwater wedge (quantifying the extent of SWI). A generalized linear model (GLM) along with a Gamma distribution function was developed to describe the delayed and prolonged effect of rainfall events on short-term groundwater behavior. This model validated with results of daily averaged SGD and SWI from the simulations of groundwater and solute transport using independent rainfall data sets, performed well in predicting the behavior of the nearshore groundwater system under the combined influence of episodic rainfall, tides, and density gradients. The findings and developed GLM form a basis for evaluating and predicting SGD, SWI, and associated mass fluxes from unconfined coastal aquifers under natural conditions, including episodic rainfall.

Projecting Changes in S. Florida Rainfall for the 21st century: Scenarios, Downscaling and Analysis

NASA Astrophysics Data System (ADS)

Cioffi, F.; Lall, U.; Monti, A.

2013-12-01

A Non-Homogeneous hidden Markov Models (NHMM) is developed using a 65-years record (1948-2012) of daily rainfall amount at nineteen stations in South Florida and re-analysis atmospheric fields of Temperature (T) at 1000 hPa, Geo Potential Height (GPH) at 1000 hPa, Meridional Winds (MW) and Zonal Winds (ZW) at 850 hPa, and Zonal Winds on the specific latitude of 27N (ZW27N) from 10 to 1000 hPa. The NHMM fitted is then used for predicting future rainfall patterns under global warming scenario (RCP8.5), using predictors from the CMCC-CMS simulations from 1950-2100. The model directly includes a consideration of seasonality through changes in the driving variables thus addressing the question of how future changes in seasonality of precipitation can also be modeled. The results of the simulations obtained by using the downscaling model NHMM, with predictors derived from the simulations of CMCC-CMS CGM, in the worst conditions of global warming as simulated by RCP8.5 scenario, seems to indicate that, as a consequence of increase of CO2 concentration and temperature, South Florida should be subjected to more frequent dry conditions for the most part of the year, due mainly to a reduction of number of wet days and, at the same time, the territory should be also affected by extreme rainfall events that are more intense than the present ones. What appears from results is an increases of rainfall variability. This scenario seems coherent with the trends of rainfall patterns observed in the XX century. An investigation on the causes of such hydrologic changes, and specifically on the role of North Atlantic Subtropical High is pursued.

Performance and efficiency of geotextile-supported erosion control measures during simulated rainfall events

NASA Astrophysics Data System (ADS)

Obriejetan, Michael; Rauch, Hans Peter; Florineth, Florin

2013-04-01

Erosion control systems consisting of technical and biological components are widely accepted and proven to work well if installed properly with regard to site-specific parameters. A wide range of implementation measures for this specific protection purpose is existent and new, in particular technical solutions are constantly introduced into the market. Nevertheless, especially vegetation aspects of erosion control measures are frequently disregarded and should be considered enhanced against the backdrop of the development and realization of adaptation strategies in an altering environment due to climate change associated effects. Technical auxiliaries such as geotextiles typically used for slope protection (nettings, blankets, turf reinforcement mats etc.) address specific features and due to structural and material diversity, differing effects on sediment yield, surface runoff and vegetational development seem evident. Nevertheless there is a knowledge gap concerning the mutual interaction processes between technical and biological components respectively specific comparable data on erosion-reducing effects of technical-biological erosion protection systems are insufficient. In this context, an experimental arrangement was set up to study the correlated influences of geotextiles and vegetation and determine its (combined) effects on surface runoff and soil loss during simulated heavy rainfall events. Sowing vessels serve as testing facilities which are filled with top soil under application of various organic and synthetic geotextiles and by using a reliable drought resistant seed mixture. Regular vegetational monitoring as well as two rainfall simulation runs with four repetitions of each variant were conducted. Therefore a portable rainfall simulator with standardized rainfall intensity of 240 mm h-1 and three minute rainfall duration was used to stress these systems on different stages of plant development at an inclination of 30 degrees. First results show significant differences between the systems referring to sediment yield and runoff amount respectively vegetation development.

Attribution of Extreme Rainfall Events in the South of France Using EURO-CORDEX Simulations

NASA Astrophysics Data System (ADS)

Luu, L. N.; Vautard, R.; Yiou, P.

2017-12-01

The Mediterranean region regularly undergoes episodes of intense precipitation in the fall season that exceed 300mm a day. This study focuses on the role of climate change on the dynamics of the events that occur in the South of France. We used an ensemble of 10 EURO-CORDEX model simulations with two horizontal resolutions (EUR-11: 0.11° and EUR-44: 0.44°) for the attribution of extreme rainfall in the fall in the Cevennes mountain range (South of France). The biases of the simulations were corrected with simple scaling adjustment and a quantile correction (CDFt). This produces five datasets including EUR-44 and EUR-11 with and without scaling adjustment and CDFt-EUR-11, on which we test the impact of resolution and bias correction on the extremes. Those datasets, after pooling all of models together, are fitted by a stationary Generalized Extreme Value distribution for several periods to estimate a climate change signal in the tail of distribution of extreme rainfall in the Cévenne region. Those changes are then interpreted by a scaling model that links extreme rainfall with mean and maximum daily temperature. The results show that higher-resolution simulations with bias adjustment provide a robust and confident increase of intensity and likelihood of occurrence of autumn extreme rainfall in the area in current climate in comparison with historical climate. The probability (exceedance probability) of 1-in-1000-year event in historical climate may increase by a factor of 1.8 under current climate with a confident interval of 0.4 to 5.3 following the CDFt bias-adjusted EUR-11. The change of magnitude appears to follow the Clausius-Clapeyron relation that indicates a 7% increase in rainfall per 1oC increase in temperature.

Simulation of localized heavy precipitation in South Korea on 20 June 2014: sensitivity test of integration time-step size and an effect of topographic resolution using WRF model

NASA Astrophysics Data System (ADS)

Roh, Joon-Woo; Jee, Joon-Bum; Lim, A.-Young; Choi, Young-Jean

2015-04-01

Korean warm-season rainfall, accounting for about three-fourths of the annual precipitation, is primarily caused by Changma front, which is a kind of the East Asian summer monsoon, and localized heavy rainfall with convective instability. Various physical mechanisms potentially exert influences on heavy precipitation over South Korea. Representatively, the middle latitude and subtropical weather fronts, associated with a quasi-stationary moisture convergence zone among varying air masses, make up one of the main rain-bearing synoptic scale systems. Localized heavy rainfall events in South Korea generally arise from mesoscale convective systems embedded in these synoptic scale disturbances along the Changma front or convective instabilities resulted from unstable air mass including the direct or indirect effect of typhoons. In recent years, torrential rainfalls, which are more than 30mm/hour of precipitation amount, in warm-season has increased threefold in Seoul, which is a metropolitan city in South Korea. In order to investigate multiple potential causes of warm-season localized heavy precipitation in South Korea, a localized heavy precipitation case took place on 20 June 2014 at Seoul. This case was mainly seen to be caused by short-wave trough, which is associated with baroclinic instability in the northwest of Korea, and a thermal low, which has high moist and warm air through analysis. This structure showed convective scale torrential rain was embedded in the dynamic and in the thermodynamic structures. In addition to, a sensitivity of rainfall amount and maximum rainfall location to the integration time-step sizes was investigated in the simulations of a localized heavy precipitation case using Weather Research and Forecasting model. The simulation of time-step sizes of 9-27s corresponding to a horizontal resolution of 4.5km and 1.5km varied slightly difference of the maximum rainfall amount. However, the sensitivity of spatial patterns and temporal variations in rainfall were relatively small for the time-step sizes. The effect of topography was also important in the localized heavy precipitation simulation.

Rainfall variability and extremes over southern Africa: Assessment of a climate model to reproduce daily extremes

NASA Astrophysics Data System (ADS)

Williams, C. J. R.; Kniveton, D. R.; Layberry, R.

2009-04-01

It is increasingly accepted that that any possible climate change will not only have an influence on mean climate but may also significantly alter climatic variability. A change in the distribution and magnitude of extreme rainfall events (associated with changing variability), such as droughts or flooding, may have a far greater impact on human and natural systems than a changing mean. This issue is of particular importance for environmentally vulnerable regions such as southern Africa. The subcontinent is considered especially vulnerable to and ill-equipped (in terms of adaptation) for extreme events, due to a number of factors including extensive poverty, famine, disease and political instability. Rainfall variability and the identification of rainfall extremes is a function of scale, so high spatial and temporal resolution data are preferred to identify extreme events and accurately predict future variability. The majority of previous climate model verification studies have compared model output with observational data at monthly timescales. In this research, the assessment of ability of a state of the art climate model to simulate climate at daily timescales is carried out using satellite derived rainfall data from the Microwave Infra-Red Algorithm (MIRA). This dataset covers the period from 1993-2002 and the whole of southern Africa at a spatial resolution of 0.1 degree longitude/latitude. The ability of a climate model to simulate current climate provides some indication of how much confidence can be applied to its future predictions. In this paper, simulations of current climate from the UK Meteorological Office Hadley Centre's climate model, in both regional and global mode, are firstly compared to the MIRA dataset at daily timescales. This concentrates primarily on the ability of the model to simulate the spatial and temporal patterns of rainfall variability over southern Africa. Secondly, the ability of the model to reproduce daily rainfall extremes will be assessed, again by a comparison with extremes from the MIRA dataset. The paper will conclude by discussing the user needs of satellite rainfall retrievals from a climate change modelling prospective.

Evaluation of CMIP5 twentieth century rainfall simulation over the equatorial East Africa

NASA Astrophysics Data System (ADS)

Ongoma, Victor; Chen, Haishan; Gao, Chujie

2018-02-01

This study assesses the performance of 22 Coupled Model Intercomparison Project Phase 5 (CMIP5) historical simulations of rainfall over East Africa (EA) against reanalyzed datasets during 1951-2005. The datasets were sourced from Global Precipitation Climatology Centre (GPCC) and Climate Research Unit (CRU). The metrics used to rank CMIP5 Global Circulation Models (GCMs) based on their performance in reproducing the observed rainfall include correlation coefficient, standard deviation, bias, percentage bias, root mean square error, and trend. Performances of individual models vary widely. The overall performance of the models over EA is generally low. The models reproduce the observed bimodal rainfall over EA. However, majority of them overestimate and underestimate the October-December (OND) and March-May (MAM) rainfall, respectively. The monthly (inter-annual) correlation between model and reanalyzed is high (low). More than a third of the models show a positive bias of the annual rainfall. High standard deviation in rainfall is recorded in the Lake Victoria Basin, central Kenya, and eastern Tanzania. A number of models reproduce the spatial standard deviation of rainfall during MAM season as compared to OND. The top eight models that produce rainfall over EA relatively well are as follows: CanESM2, CESM1-CAM5, CMCC-CESM, CNRM-CM5, CSIRO-Mk3-6-0, EC-EARTH, INMCM4, and MICROC5. Although these results form a fairly good basis for selection of GCMs for carrying out climate projections and downscaling over EA, it is evident that there is still need for critical improvement in rainfall-related processes in the models assessed. Therefore, climate users are advised to use the projections of rainfall from CMIP5 models over EA cautiously when making decisions on adaptation to or mitigation of climate change.

The effects of compound danshen dripping pills and human umbilical cord blood mononuclear cell transplant after acute myocardial infarction.

PubMed

Jun, Yi; Chunju, Yuan; Qi, Ai; Liuxia, Deng; Guolong, Yu

2014-04-01

The low frequency of survival of stem cells implanted in the myocardium after acute myocardial infarction may be caused by inflammation and oxidative stress in the myocardial microenvironment. We evaluated the effects of a traditional Chinese medicine, Compound Danshen Dripping Pills, on the cardiac microenvironment and cardiac function when used alone or in combination with human umbilical cord blood mononuclear cell transplant after acute myocardial infarction. After surgically induced acute myocardial infarction, rabbits were treated with Compound Danshen Dripping Pills alone or in combination with human umbilical cord blood mononuclear cell transplant. Evaluation included histology, measurement of left ventricular ejection fraction and fractional shortening, leukocyte count, count of green fluorescent protein positive cells, superoxide dismutase activity, and malondialdehyde content. Combination treatment with Compound Danshen Dripping Pills and human umbilical cord blood mononuclear cell transplant significantly increased the survival of implanted cells, inhibited cardiac cell apoptosis, decreased oxidative stress, decreased the inflammatory response, and improved cardiac function. Rabbits treated with either Compound Danshen Dripping Pills or human umbilical cord blood mononuclear cells alone had improvement in these effects compared with untreated control rabbits. Combination therapy with Compound Danshen Dripping Pills and human umbilical cord blood mononuclear cells may improve cardiac function and morphology after acute myocardial infarction.

Visible light exposure reduces the drip loss of fresh-cut watermelon.

PubMed

Wang, Yubin; Li, Wu; Cai, Wenqian; Ma, Yue; Xu, Yong; Zhao, Xiaoyan; Zhang, Chao

2018-05-01

Drip loss of fresh-cut watermelon has become a concern for both producers and consumers. The effect of visible light exposure on the drip loss of fresh-cut watermelon was evaluated. Visible light treatments of 3000 and 10 Lux were applied to fresh-cut watermelon at 4 °C during the shelf life for 5 days, with light exposure of 150 Lux as the control. The drip loss of the fresh-cut watermelon at 3000 Lux was 74.8% of that at 150 Lux on the fifth day, and the moisture evaporation at 3000 Lux was 1.89 times that at 150 Lux. Moreover, the light exposure of 3000 Lux reduced the activity of polygalacturonase, which is a key hydrolase related to cell wall degradation. The cell wall degradation ratio of the fresh-cut watermelon at 3000 Lux was 81.7% of that at 150 Lux on the fifth day. Overall, light exposure of 3000 Lux reduced drip loss by accelerating moisture evaporation in fresh-cut watermelon, as well as by reducing the activity of polygalacturonase and the ratio of cell wall degradation. Hence, exposing the fresh-cut watermelon to visible light of 3000 Lux during the shelf life was a feasible way of reducing drip loss.

Short-Range Prediction of Monsoon Precipitation by NCMRWF Regional Unified Model with Explicit Convection

NASA Astrophysics Data System (ADS)

Mamgain, Ashu; Rajagopal, E. N.; Mitra, A. K.; Webster, S.

2018-03-01

There are increasing efforts towards the prediction of high-impact weather systems and understanding of related dynamical and physical processes. High-resolution numerical model simulations can be used directly to model the impact at fine-scale details. Improvement in forecast accuracy can help in disaster management planning and execution. National Centre for Medium Range Weather Forecasting (NCMRWF) has implemented high-resolution regional unified modeling system with explicit convection embedded within coarser resolution global model with parameterized convection. The models configurations are based on UK Met Office unified seamless modeling system. Recent land use/land cover data (2012-2013) obtained from Indian Space Research Organisation (ISRO) are also used in model simulations. Results based on short-range forecast of both the global and regional models over India for a month indicate that convection-permitting simulations by the high-resolution regional model is able to reduce the dry bias over southern parts of West Coast and monsoon trough zone with more intense rainfall mainly towards northern parts of monsoon trough zone. Regional model with explicit convection has significantly improved the phase of the diurnal cycle of rainfall as compared to the global model. Results from two monsoon depression cases during study period show substantial improvement in details of rainfall pattern. Many categories in rainfall defined for operational forecast purposes by Indian forecasters are also well represented in case of convection-permitting high-resolution simulations. For the statistics of number of days within a range of rain categories between `No-Rain' and `Heavy Rain', the regional model is outperforming the global model in all the ranges. In the very heavy and extremely heavy categories, the regional simulations show overestimation of rainfall days. Global model with parameterized convection have tendency to overestimate the light rainfall days and underestimate the heavy rain days compared to the observation data.

Rainfall threshold definition using an entropy decision approach and radar data

NASA Astrophysics Data System (ADS)

Montesarchio, V.; Ridolfi, E.; Russo, F.; Napolitano, F.

2011-07-01

Flash flood events are floods characterised by a very rapid response of basins to storms, often resulting in loss of life and property damage. Due to the specific space-time scale of this type of flood, the lead time available for triggering civil protection measures is typically short. Rainfall threshold values specify the amount of precipitation for a given duration that generates a critical discharge in a given river cross section. If the threshold values are exceeded, it can produce a critical situation in river sites exposed to alluvial risk. It is therefore possible to directly compare the observed or forecasted precipitation with critical reference values, without running online real-time forecasting systems. The focus of this study is the Mignone River basin, located in Central Italy. The critical rainfall threshold values are evaluated by minimising a utility function based on the informative entropy concept and by using a simulation approach based on radar data. The study concludes with a system performance analysis, in terms of correctly issued warnings, false alarms and missed alarms.

Urban pluvial flood prediction: a case study evaluating radar rainfall nowcasts and numerical weather prediction models as model inputs.

PubMed

Thorndahl, Søren; Nielsen, Jesper Ellerbæk; Jensen, David Getreuer

2016-12-01

Flooding produced by high-intensive local rainfall and drainage system capacity exceedance can have severe impacts in cities. In order to prepare cities for these types of flood events - especially in the future climate - it is valuable to be able to simulate these events numerically, both historically and in real-time. There is a rather untested potential in real-time prediction of urban floods. In this paper, radar data observations with different spatial and temporal resolution, radar nowcasts of 0-2 h leadtime, and numerical weather models with leadtimes up to 24 h are used as inputs to an integrated flood and drainage systems model in order to investigate the relative difference between different inputs in predicting future floods. The system is tested on the small town of Lystrup in Denmark, which was flooded in 2012 and 2014. Results show it is possible to generate detailed flood maps in real-time with high resolution radar rainfall data, but rather limited forecast performance in predicting floods with leadtimes more than half an hour.

Multiphase flow in geometrically simple fracture intersections

USGS Publications Warehouse

Basagaoglu, H.; Meakin, P.; Green, C.T.; Mathew, M.; ,

2006-01-01

A two-dimensional lattice Boltzmann (LB) model with fluid-fluid and solid-fluid interaction potentials was used to study gravity-driven flow in geometrically simple fracture intersections. Simulated scenarios included fluid dripping from a fracture aperture, two-phase flow through intersecting fractures and thin-film flow on smooth and undulating solid surfaces. Qualitative comparisons with recently published experimental findings indicate that for these scenarios the LB model captured the underlying physics reasonably well.

2D Relativistic MHD simulations of the Kruskal-Schwarzschild instability in a relativistic striped wind

NASA Astrophysics Data System (ADS)

Gill, Ramandeep; Granot, Jonathan; Lyubarsky, Yuri

2018-03-01

We study the linear and non-linear development of the Kruskal-Schwarzchild instability in a relativisitically expanding striped wind. This instability is the generalization of Rayleigh-Taylor instability in the presence of a magnetic field. It has been suggested to produce a self-sustained acceleration mechanism in strongly magnetized outflows found in active galactic nuclei, gamma-ray bursts, and micro-quasars. The instability leads to magnetic reconnection, but in contrast with steady-state Sweet-Parker reconnection, the dissipation rate is not limited by the current layer's small aspect ratio. We performed two-dimensional (2D) relativistic magnetohydrodynamic (RMHD) simulations featuring two cold and highly magnetized (1 ≤ σ ≤ 103) plasma layers with an anti-parallel magnetic field separated by a thin layer of relativistically hot plasma with a local effective gravity induced by the outflow's acceleration. Our simulations show how the heavier relativistically hot plasma in the reconnecting layer drips out and allows oppositely oriented magnetic field lines to reconnect. The instability's growth rate in the linear regime matches the predictions of linear stability analysis. We find turbulence rather than an ordered bulk flow near the reconnection region, with turbulent velocities up to ˜0.1c, largely independent of model parameters. However, the magnetic energy dissipation rate is found to be much slower, corresponding to an effective ordered bulk velocity inflow into the reconnection region vin = βinc of 10-3 ≲ βin ≲ 5 × 10-3. This occurs due to the slow evacuation of hot plasma from the current layer, largely because of the Kelvin-Helmholtz instability experienced by the dripping plasma. 3D RMHD simulations are needed to further investigate the non-linear regime.

Blood drop size in passive dripping from weapons.

PubMed

Kabaliuk, N; Jermy, M C; Morison, K; Stotesbury, T; Taylor, M C; Williams, E

2013-05-10

Passive dripping, the slow dripping of blood under gravity, is responsible for some bloodstains found at crime scenes, particularly drip trails left by a person moving through the scene. Previous work by other authors has established relationships, under ideal conditions, between the size of the stain, the number of spines and satellite stains, the roughness of the surface, the size of the blood droplet and the height from which it falls. To apply these relationships to infer the height of fall requires independent knowledge of the size of the droplet. This work aims to measure the size of droplets falling from objects representative of hand-held weapons. Pig blood was used, with density, surface tension and viscosity controlled to fall within the normal range for human blood. Distilled water was also tested as a reference. Drips were formed from stainless steel objects with different roughnesses including cylinders of diameter between 10 and 100 mm, and flat plates. Small radius objects including a knife and a wrench were also tested. High speed images of the falling drops were captured. The primary blood drop size ranged from 4.15±0.11 mm up to 6.15±0.15 mm (depending on the object), with the smaller values from sharper objects. The primary drop size correlated only weakly with surface roughness, over the roughness range studied. The number of accompanying droplets increased with the object size, but no significant correlation with surface texture was observed. Dripping of blood produced slightly smaller drops, with more accompanying droplets, than dripping water. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Evolution of the East African rift: Drip magmatism, lithospheric thinning and mafic volcanism

NASA Astrophysics Data System (ADS)

Furman, Tanya; Nelson, Wendy R.; Elkins-Tanton, Linda T.

2016-07-01

The origin of the Ethiopian-Yemeni Oligocene flood basalt province is widely interpreted as representing mafic volcanism associated with the Afar mantle plume head, with minor contributions from the lithospheric mantle. We reinterpret the geochemical compositions of primitive Oligocene basalts and picrites as requiring a far more significant contribution from the metasomatized subcontinental lithospheric mantle than has been recognized previously. This region displays the fingerprints of mantle plume and lithospheric drip magmatism as predicted from numerical models. Metasomatized mantle lithosphere is not dynamically stable, and heating above the upwelling Afar plume caused metasomatized lithosphere with a significant pyroxenite component to drip into the asthenosphere and melt. This process generated the HT2 lavas observed today in restricted portions of Ethiopia and Yemen now separated by the Red Sea, suggesting a fundamental link between drip magmatism and the onset of rifting. Coeval HT1 and LT lavas, in contrast, were not generated by drip melting but instead originated from shallower, dominantly anhydrous peridotite. Looking more broadly across the East African Rift System in time and space, geochemical data support small volume volcanic events in Turkana (N. Kenya), Chyulu Hills (S. Kenya) and the Virunga province (Western Rift) to be derived ultimately from drip melting. The removal of the gravitationally unstable, metasomatized portion of the subcontinental lithospheric mantle via dripping is correlated in each case with periods of rapid uplift. The combined influence of thermo-mechanically thinned lithosphere and the Afar plume together thus controlled the locus of continental rift initiation between Africa and Arabia and provide dynamic support for the Ethiopian plateau.

Geochemical signal in drip waters and carbonates from three year monitoring of Drac Cave in Mallorca (Western Mediterranean)

NASA Astrophysics Data System (ADS)

Cacho, Isabel; Cisneros, Mercé; Torner, Judit; Moreno, Ana; Stoll, Heather; Bladé, Ileana; Fornos, Joan

2016-04-01

In order to establish the potential connection between climatic conditions over Mallorca and the chemistry of speleothem growths, a still ongoing monitoring exercise is in development in Drac Cave in Mallorca (Spain) starting from April 2013. This location in the Western Mediterranean was selected to represent Mediterranean semi-arid climatic conditions within a wider monitoring plan covering a transect across the northern part of the Iberian Peninsula, from the Catabric realm, across the Pyrenees and Iberian ranges until the Mediterranean, within the framework of the OPERA research project. Drip waters have been recovered at weakly resolution and carbonate precipitates represent seasonal periods. This monitoring is complemented with drip water and carbonate collection at seasonal scale in another cave close to Drac Cave. This second cave was selected in order to represent comparable climatic conditions but far of any human land-intervention since the Drac cave is partially located under an urban developed area, although drip water and carbonate collection is performed in a location bellow autochthonous forest. First results show that drip flow has a rather constant rate along the year even though the large contrast on rain availability. In contrast, chemical signal of the drip waters shows a rapid response (few days) to changes in rain patterns but of relatively small magnitude. Isotopes in the carbonate precipitates present a seasonal signal and trend that reflect changes in the drip water composition. This data set, although preliminary, will be discussed in the context of the changing meteorological conditions of the last three years.

The impact of fire on the geochemistry of speleothem-forming drip water in a sub-alpine cave.

PubMed

Coleborn, Katie; Baker, Andy; Treble, Pauline C; Andersen, Martin S; Baker, Andrew; Tadros, Carol V; Tozer, Mark; Fairchild, Ian J; Spate, Andy; Meehan, Sophia

2018-06-12

Fire dramatically modifies the surface environment by combusting vegetation and changing soil properties. Despite this well-documented impact on the surface environment, there has been limited research into the impact of fire events on karst, caves and speleothems. Here we report the first experiment designed to investigate the short-term impacts of a prescribed fire on speleothem-forming cave drip water geochemistry. Before and after the fire, water was collected on a bi-monthly basis from 18 drip sites in South Glory Cave, New South Wales, Australia. Two months post-fire, there was an increase in B, Si, Na, Fe and Pb concentrations at all drip sites. We conclude that this response is most likely due to the transport of soluble ash-derived elements from the surface to the cave drip water below. A significant deviation in stable water isotopic composition from the local meteoric water line was also observed at six of the sites. We hypothesise that this was due to partial evaporation of soil water resulting in isotopic enrichment of drip waters. Our results demonstrate that even low-severity prescribed fires can have an impact on speleothem-forming cave drip water geochemistry. These findings are significant because firstly, fires need to be considered when interpreting past climate from speleothem δ 18 O isotope and trace element records, particularly in fire prone regions such as Australia, North America, south west Europe, Russia and China. Secondly, it supports research that demonstrates speleothems could be potential proxy records for past fires. Copyright © 2017 Elsevier B.V. All rights reserved.