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.

Gamma-radiation monitoring in post-tectonic biotitic granites at Celorico da Beira

NASA Astrophysics Data System (ADS)

Domingos, Filipa; Barbosa, Susana; Pereira, Alcides; Neves, Luís

2017-04-01

Despite its obvious relevance, the effect of meteorological variables such as temperature, pressure, wind, rainfall and particularly humidity on the temporal variability of natural radiation is complex and still not fully understood. Moreover, the nature of their influence with increasing depth is also poorly understood. Thereby, two boreholes were set 3 m apart in the region of Celorico da Beira within post-tectonic biotitic granites of the Beiras Batolith. Continuous measurements were obtained with identical gamma-ray scintillometers deployed at depths of 1 and 6 m during a 6 month period in the years of 2014 and 2015. Temperature, relative humidity, pressure, rainfall, wind speed and direction were measured at the site, as well as temperature and relative humidity inside the boreholes, with the aim of assessing the influence of meteorological parameters on the temporal variability of gamma radiation at two distinct depths. Both time series display a complex temporal structure including multiyear, seasonal and daily variability. At 1 m depth, a daily periodicity on the gamma ray counts time series was noticed with daily maxima occurring most frequently from 8 to 12 p.m. and daily minima between 8 and 12 a.m.. At 6 m depth, maximum and minimum daily means occurred with approximately a 10 h lag from the above. Gamma radiation data exhibited fairly strong correlations with temperature and relative humidity, however, varying with depth. Gamma radiation counts increased with increasing temperature and decreasing relative humidity at 1 m depth, while at a 6 m depth the opposite was recorded, with counts increasing with relative humidity and decreasing with temperature. Wind speed was shown to be inversely related with counts at 6 m depth, while positively correlated at 1 m depth. Pressure and rainfall had minor effects on both short-term and long-term gamma radiation counts.

Evaluation and prediction of anomalous El Niño generated rainfalls in Peruvian and Ecuadorian coastal zone

NASA Astrophysics Data System (ADS)

Cadier, E.; Rossel, F.; Pouyaud, B.; Raymond, M.

2003-04-01

Coastal regions of Southern Ecuador and Northern Peru rainfalls are well known for their sensitivity to the El Niño/Southern Oscillation (ENSO) phenomenon. New monthly rainfall index series were set up from a network of 200 rainfall stations in the Ecuadorian and Peruvian coastal region. Throughout the study, rainfall was modelled keeping a distinction between a "dependent" data set used as a training period and an "independent" portion of the record reserved for validation. Multiple regression models were proposed to predict monthly rainfall in the Guayaquil and in northern coastal Peru, using as predictors, sea surface temperature, precipitation, meridional and zonal wind in the eastern equatorial Pacific. Then, the resulting equations were used to predict rainfall anomalies in the independent data set. In the Guayaquil zone, there is considerable predictable expertise for the rainy months of the year, the best predictability being assessed from March to May. The multiple linear correlations explain 60 to 82% of the monthly-precipitation variance. Northern coastal Ecuadorian region's preseason rainfall is the most powerful predictor for the rainy season peak in Guayaquil, while the eastern equatorial Pacific sea surface temperature is the most powerful predictor for the end of rainy season. KEY WORDS: El Niño, Rainfall Prediction, Ecuador.

Variations of Sea Surface Temperature, Wind Stress, and Rainfall over the Tropical Atlantic and South America.

NASA Astrophysics Data System (ADS)

Nobre, Paulo; Srukla, J.

1996-10-01

Empirical orthogonal functions (E0Fs) and composite analyses are used to investigate the development of sea surface temperature (SST) anomaly patterns over the tropical Atlantic. The evolution of large-scale rainfall anomaly patterns over the equatorial Atlantic and South America are also investigated. 71e EOF analyses revealed that a pattern of anomalous SST and wind stress asymmetric relative to the equator is the dominant mode of interannual and longer variability over the tropical Atlantic. The most important findings of this study are as follows.Atmospheric circulation anomalies precede the development of basinwide anomalous SST patterns over the tropical Atlantic. Anomalous SST originate off the African coast simultaneously with atmospheric circulation anomalies and expand westward afterward. The time lag between wind stress relaxation (strengthening) and maximum SST warming (cooling) is about two months.Anomalous atmospheric circulation patterns over northern tropical Atlantic are phase locked to the seasonal cycle. Composite fields of SLP and wind stress over northern tropical Atlantic can be distinguished from random only within a few months preceding the March-May (MAM) season. Observational evidence is presented to show that the El Niño-Southern Oscillation phenomenon in the Pacific influences atmospheric circulation and SST anomalies over northern tropical Atlantic through atmospheric teleconnection patterns into higher latitudes of the Northern Hemisphere.The well-known droughts over northeastern Brazil (Nordeste) are a local manifestation of a much larger-scale rainfall anomaly pattern encompassing the whole equatorial Atlantic and Amazon region. Negative rainfall anomalies to the south of the equator during MAM, which is the rainy season for the Nordeste region, are related to an early withdrawal of the intertropical convergence zone toward the warm SST anomalies over the northern tropical Atlantic. Also, it is shown that precipitation anomalies over southern and northern parts of the Nordeste are out of phase: drought years over the northern Nordeste are commonly preceded by wetter years over the southern Nordeste, and vice versa.

The stable isotope amount effect: New insights from NEXRAD echo tops, Luquillo Mountains, Puerto Rico

USGS Publications Warehouse

Scholl, Martha A.; Shanley, James B.; Zegarra, Jan Paul; Coplen, Tyler B.

2009-01-01

The stable isotope amount effect has often been invoked to explain patterns of isotopic composition of rainfall in the tropics. This paper describes a new approach, correlating the isotopic composition of precipitation with cloud height and atmospheric temperature using NEXRAD radar echo tops, which are a measure of the maximum altitude of rainfall within the clouds. The seasonal differences in echo top altitudes and their corresponding temperatures are correlated with the isotopic composition of rainfall. These results offer another factor to consider in interpretation of the seasonal variation in isotopic composition of tropical rainfall, which has previously been linked to amount or rainout effects and not to temperature effects. Rain and cloud water isotope collectors in the Luquillo Mountains in northeastern Puerto Rico were sampled monthly for three years and precipitation was analyzed for δ18O and δ2H. Precipitation enriched in 18O and 2H occurred during the winter dry season (approximately December–May) and was associated with a weather pattern of trade wind showers and frontal systems. During the summer rainy season (approximately June–November), precipitation was depleted in 18O and 2H and originated in low pressure systems and convection associated with waves embedded in the prevailing easterly airflow. Rain substantially depleted in 18O and 2H compared to the aforementioned weather patterns occurred during large low pressure systems. Weather analysis showed that 29% of rain input to the Luquillo Mountains was trade wind orographic rainfall, and 30% of rainfall could be attributed to easterly waves and low pressure systems. Isotopic signatures associated with these major climate patterns can be used to determine their influence on streamflow and groundwater recharge and to monitor possible effects of climate change on regional water resources.

Throughfall under a teak plantation in Thailand: a multifactorial analysis on the effects of canopy phenology and meteorological conditions

NASA Astrophysics Data System (ADS)

Tanaka, N.; Levia, D. F., Jr.; Igarashi, Y.; Nanko, K.; Yoshifuji, N.; Tanaka, K.; Chatchai, T.; Suzuki, M.; Kumagai, T.

2014-12-01

Teak (Tectona grandis Linn. f.) plantations cover vast areas throughout Southeast Asia and are of great economic importance. This study has sought to increase our understanding of throughfall inputs under teak by analyzing the abiotic and biotic factors governing throughfall amounts and throughfall ratios in relation to three canopy phenophases (leafless, leafing, and leafed). There is no rain during the brief leaf senescence phenophase. Daily data was available for both throughfall volumes and depths as well as leaf area index. Detailed meteorological data were available in situ every ten minutes. Leveraging this high-resolution field data, we employed boosted regression trees (BRT) analysis to identify the primary controls on throughfall amount and ratio during each of the three canopy phenophases. Whereas throughfall amounts were always dominated by the magnitude of rainfall (as expected), throughfall ratios were governed by a suite of predictor variables during each phenophase. The BRT analysis demonstrated that throughfall ratio in the leafless phase was most influenced (in descending order of importance) by air temperature, rainfall amount, maximum wind speed, and rainfall intensity. Throughfall ratio in the leafed phenophase was dominated by rainfall amount which exerted 54.0% of the relative influence. The leafing phenophase was an intermediate case where rainfall amount, air temperature, and vapor pressure deficit were most important. Our results highlight the fact that throughfall ratios are differentially influenced by a suite of meteorological variables during leafless, leafing, and leafed phenophases. Abiotic variables (rainfall amount, air temperature, vapor pressure deficit, and maximum wind speed) trumped leaf area index and stand density in their effect on throughfall ratio. The leafing phenophase, while transitional in nature and short in duration, has a detectable and unique impact on water inputs to teak plantations. Further work is clearly needed to better gauge the importance of the leaf emergence period to the stemflow hydrology and forest biogeochemistry of teak plantations.

The Relationship Between Monthdisease Incidence Rate and Climatic Factor of Classical Swine Fever

NASA Astrophysics Data System (ADS)

Wang, Hongbin; Xu, Danning; Xiao, Jianhua; Zhang, Ru; Dong, Jing

The Swine Fever is a kind of acute, highly infective epidemic disease of animals; it is name as Classical Swine Fever (CSF) by World animal Health organization. Meteorological factors such as temperature, air pressure and rainfall affect the epidemic of CSF significantly through intermediary agent and CSF viral directly. However there is significant difference among different region for mode of effects. Accordingly, the analyze must adopt different methods. The dependability between incidence rate each month of CSF and meteorological factors from 1999 to 2004 was analyzed in this paper. The function of meteorological factors on CSF was explored and internal law was expected to be discovered. The correlation between the incidence rate of Swine Fever and meteorological factors, thus the foundation analysis of the early warning and the decision-making was made, the result indicated that the incidence rate of CSF has negative correlation with temperature, rainfall, cloudage; relative humidity has positive correlation with disease; for air pressure, except average air pressure of one month, other air pressure factors have positive correlation with disease; for wind speed, except Difference among moths of wind speed and average temperature of one month. have positive correlation with disease, other wind speed factors has negative correlation with disease.

A quantitative assessment of the contributions of climatic indicators to changes in nutrients and oxygen levels in a shallow reservoir in China

NASA Astrophysics Data System (ADS)

Zhang, Chen; Zhang, Wenna; Liu, Hanan; Gao, Xueping; Huang, Yixuan

2017-06-01

Climate change has an indirect effect on water quality in freshwater ecosystems, but it is difficult to assess the contribution of climate change to the complex system. This study explored to what extent climatic indicators (air temperature, wind speed, and rainfall) influence nutrients and oxygen levels in a shallow reservoir, Yuqiao Reservoir, China. The study comprises three parts—describing the temporal trends of climatic indicators and water quality parameters during the period 1992-2011, analyzing the potential impacts of climate on water quality, and finally developing a quantitative assessment to evaluate how climatic factors govern nutrient levels in the reservoir. Our analyses showed that the reservoir experienced substantial cold periods (1992-2001) followed by a warm period (2002-2011). The results showed that increasing air temperature in spring, autumn, and winter and increasing annual wind speed decrease total phosphorus (TP) concentration in the reservoir in spring, summer, and winter. According to the quantitative assessment, the increase in air temperature in spring and winter had a larger contribution to the decrease in TP concentration (47.2 and 64.1%), compared with the influence from decreased wind speed and rainfall. The field data suggest that nutrients decline due to enhanced uptake by macrophytes in years when spring was warmer and the macrophytes started to grow earlier in the season. The increasing wind speed and air temperature in spring also significantly contribute to the increase in dissolved oxygen concentration. This study helps managers to foresee how potential future climate change might influence water quality in similar lake ecosystems.

The local and global climate forcings induced inhomogeneity of Indian rainfall.

PubMed

Nair, P J; Chakraborty, A; Varikoden, H; Francis, P A; Kuttippurath, J

2018-04-16

India is home for more than a billion people and its economy is largely based on agrarian society. Therefore, rainfall received not only decides its livelihood, but also influences its water security and economy. This situation warrants continuous surveillance and analysis of Indian rainfall. These kinds of studies would also help forecasters to better tune their models for accurate weather prediction. Here, we introduce a new method for estimating variability and trends in rainfall over different climate regions of India. The method based on multiple linear regression helps to assess contributions of different remote and local climate forcings to seasonal and regional inhomogeneity in rainfall. We show that the Indian Summer Monsoon Rainfall (ISMR) variability is governed by Eastern and Central Pacific El Niño Southern Oscillation, equatorial zonal winds, Atlantic zonal mode and surface temperatures of the Arabian Sea and Bay of Bengal, and the North East Monsoon Rainfall variability is controlled by the sea surface temperature of the North Atlantic and extratropial oceans. Also, our analyses reveal significant positive trends (0.43 mm/day/dec) in the North West for ISMR in the 1979-2017 period. This study cautions against the significant changes in Indian rainfall in a perspective of global climate change.

Distinctive Features of Surface Winds over Indian Ocean Between Strong and Weak Indian Summer Monsoons: Implications With Respect To Regional Rainfall Change in India

NASA Astrophysics Data System (ADS)

Zheng, Y.; Bourassa, M. A.; Ali, M. M.

2017-12-01

This observational study focuses on characterizing the surface winds in the Arabian Sea (AS), the Bay of Bengal (BoB), and the southern Indian Ocean (SIO) with special reference to the strong and weak Indian summer monsoon rainfall (ISMR) using the latest daily gridded rainfall dataset provided by the Indian Meteorological Department (IMD) and the Cross-Calibrated Multi-Platform (CCMP) gridded wind product version 2.0 produced by Remote Sensing System (RSS) over the overlapped period 1991-2014. The potential links between surface winds and Indian regional rainfall are also examined. Results indicate that the surface wind speeds in AS and BoB during June-August are almost similar during strong ISMRs and weak ISMRs, whereas significant discrepancies are observed during September. By contrast, the surface wind speeds in SIO during June-August are found to be significantly different between strong and weak ISMRs, where they are similar during September. The significant differences in monthly mean surface wind convergence between strong and weak ISMRs are not coherent in space in the three regions. However, the probability density function (PDF) distributions of daily mean area-averaged values are distinctive between strong and weak ISMRs in the three regions. The correlation analysis indicates the area-averaged surface wind speeds in AS and the area-averaged wind convergence in BoB are highly correlated with regional rainfall for both strong and weak ISMRs. The wind convergence in BoB during strong ISMRs is relatively better correlated with regional rainfall than during weak ISMRs. The surface winds in SIO do not greatly affect Indian rainfall in short timescales, however, they will ultimately affect the strength of monsoon circulation by modulating Indian Ocean Dipole (IOD) mode via atmosphere-ocean interactions.

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.

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

Ispen, J.; Deane, M.; Ingenito, F.E.

Comparison was made of industrial morbidity and absenteeism from upper respiratory disease with various measures of pollution and weather. Tests were conducted of workers visiting dispensaries of two plants in metropolitan Philadelphia and those working for the telephone company. Weekly morbidity was significantly correlated with temperature (r = -0.614), smoke shade (r = 0.556), particulate SO/sub 4/ (r = 0.289), and particulate matter (r = 0.264). Seasonal variation was in all variables. Pollution measures were inversely related to temperature. Particulate and SO/sub 4/ were inversely related to rainfall. SO/sub 4/ was inversely related to wind velocity. Daily correlations show day-of-weekmore » effect with lower morbidity and pollution on weekends. Higher prevalence/incidence ratio in winter was found. High morbidity was preceded by a week with low temperatures, high relative humidity, high wind velocity, and high pollutant levels, and accompanied by low temperatures, high relative humidity, and high wind.« less

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.

Hydroelectric production from Brazil's São Francisco River could cease due to climate change and inter-annual variability.

PubMed

de Jong, Pieter; Tanajura, Clemente Augusto Souza; Sánchez, Antonio Santos; Dargaville, Roger; Kiperstok, Asher; Torres, Ednildo Andrade

2018-09-01

By the end of this century higher temperatures and significantly reduced rainfall are projected for the Brazilian North and Northeast (NE) regions due to Global Warming. This study examines the impact of these long-term rainfall changes on the Brazilian Northeast's hydroelectric production. Various studies that use different IPCC models are examined in order to determine the average rainfall reduction by the year 2100 in comparison to baseline data from the end of the 20th century. It was found that average annual rainfall in the NE region could decrease by approximately 25-50% depending on the emissions scenario. Analysis of historical rainfall data in the São Francisco basin during the last 57years already shows a decline of more than 25% from the 1961-90 long-term average. Moreover, average annual rainfall in the basin has been below its long-term average every year bar one since 1992. If this declining trend continues, rainfall reduction in the basin could be even more severe than the most pessimistic model projections. That is, the marked drop in average rainfall projected for 2100, based on the IPCC high emissions scenario, could actually eventuate before 2050. Due to the elasticity factor between rainfall and streamflow and because of increased amounts of irrigation in the São Francisco basin, the reduction in the NE's average hydroelectric production in the coming decades could be double the predicted decline in rainfall. Conversely, it is estimated that wind power potential in the Brazilian NE will increase substantially by 2100. Therefore both wind and solar power will need to be significantly exploited in order for the NE region to sustainably replace lost hydroelectric production. Copyright © 2018 Elsevier B.V. All rights reserved.

The prediction of the impact of climatic factors on short-term electric power load based on the big data of smart city

NASA Astrophysics Data System (ADS)

Qiu, Yunfei; Li, Xizhong; Zheng, Wei; Hu, Qinghe; Wei, Zhanmeng; Yue, Yaqin

2017-08-01

The climate changes have great impact on the residents’ electricity consumption, so the study on the impact of climatic factors on electric power load is of significance. In this paper, the effects of the data of temperature, rainfall and wind of smart city on short-term power load is studied to predict power load. The authors studied the relation between power load and daily temperature, rainfall and wind in the 31 days of January of one year. In the research, the authors used the Matlab neural network toolbox to establish the combinational forecasting model. The authors trained the original input data continuously to get the internal rules inside the data and used the rules to predict the daily power load in the next January. The prediction method relies on the accuracy of weather forecasting. If the weather forecasting is different from the actual weather, we need to correct the climatic factors to ensure accurate prediction.

Climate Change and Its Impact on the Eco-Environment of the Three-Rivers Headwater Region on the Tibetan Plateau, China.

PubMed

Jiang, Chong; Zhang, Linbo

2015-09-25

This study analyzes the impact of climate change on the eco-environment of the Three-Rivers Headwater Region (TRHR), Tibetan Plateau, China. Temperature and precipitation experienced sharp increases in this region during the past 57 years. A dramatic increase in winter temperatures contributed to a rise in average annual temperatures. Moreover, annual runoff in the Lancang (LRB) and Yangtze (YARB) river basins showed an increasing trend, compared to a slight decrease in the Yellow River Basin (YRB). Runoff is predominantly influenced by rainfall, which is controlled by several monsoon systems. The water temperature in the YRB and YARB increased significantly from 1958 to 2007 (p < 0.001), driven by air temperature changes. Additionally, owing to warming and wetting trends in the TRHR, the net primary productivity (NPP) and normalized difference vegetation index (NDVI) showed significant increasing trends during the past half-century. Furthermore, although an increase in water erosion due to rainfall erosivity was observed, wind speeds declined significantly, causing a decline in wind erosion, as well as the frequency and duration of sandstorms. A clear regional warming trend caused an obvious increasing trend in glacier runoff, with a maximum value observed in the 2000s.

Climate Change and Its Impact on the Eco-Environment of the Three-Rivers Headwater Region on the Tibetan Plateau, China

PubMed Central

Jiang, Chong; Zhang, Linbo

2015-01-01

This study analyzes the impact of climate change on the eco-environment of the Three-Rivers Headwater Region (TRHR), Tibetan Plateau, China. Temperature and precipitation experienced sharp increases in this region during the past 57 years. A dramatic increase in winter temperatures contributed to a rise in average annual temperatures. Moreover, annual runoff in the Lancang (LRB) and Yangtze (YARB) river basins showed an increasing trend, compared to a slight decrease in the Yellow River Basin (YRB). Runoff is predominantly influenced by rainfall, which is controlled by several monsoon systems. The water temperature in the YRB and YARB increased significantly from 1958 to 2007 (p < 0.001), driven by air temperature changes. Additionally, owing to warming and wetting trends in the TRHR, the net primary productivity (NPP) and normalized difference vegetation index (NDVI) showed significant increasing trends during the past half-century. Furthermore, although an increase in water erosion due to rainfall erosivity was observed, wind speeds declined significantly, causing a decline in wind erosion, as well as the frequency and duration of sandstorms. A clear regional warming trend caused an obvious increasing trend in glacier runoff, with a maximum value observed in the 2000s. PMID:26404333

Determining hydroclimatic extreme events over the south-central Andes

NASA Astrophysics Data System (ADS)

RamezaniZiarani, Maryam; Bookhagen, Bodo; Schmidt, Torsten; Wickert, Jens; de la Torre, Alejandro; Volkholz, Jan

2017-04-01

The south-central Andes in NW Argentina are characterized by a strong rainfall asymmetry. In the east-west direction exists one of the steepest rainfall gradients on Earth, resulting from the large topographic differences in this region. In addition, in the north-south direction the rainfall intensity varies as the climatic regime shifts from the tropical central Andes to the subtropical south-central Andes. In this study, we investigate hydroclimatic extreme events over the south-central Andes using ERA-Interim reanalysis data of the ECMWF (European Centre for Medium-Range Weather Forecasts), the high resolution regional climate model (COSMO-CLM) data and TRMM (Tropical Rainfall Measuring Mission) data. We divide the area in three different study regions based on elevation: The high-elevation Altiplano-Puna plateau, an intermediate area characterized by intramontane basins, and the foreland area. We analyze the correlations between climatic variables, such as specific humidity, zonal wind component, meridional wind component and extreme rainfall events in all three domains. The results show that there is a high positive temporal correlation between extreme rainfall events (90th and 99th percentile rainfall) and extreme specific humidity events (90th and 99th percentile specific humidity). In addition, the temporal variations analysis represents a trend of increasing specific humidity with time during time period (1994-2013) over the Altiplano-Puna plateau which is in agreement with rainfall trend. Regarding zonal winds, our results indicate that 99th percentile rainfall events over the Altiplano-Puna plateau coincide temporally with strong easterly winds from intermountain and foreland regions in the east. In addition, the results regarding the meridional wind component represent strong northerly winds in the foreland region coincide temporally with 99th percentile rainfall over the Altiplano-Puna plateau.

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)

A study of the correlation between dengue and weather in Kandy City, Sri Lanka (2003 -2012) and lessons learned.

PubMed

Ehelepola, N D B; Ariyaratne, Kusalika; Buddhadasa, W M N P; Ratnayake, Sunil; Wickramasinghe, Malani

2015-09-24

Weather variables affect dengue transmission. This study aimed to identify a dengue weather correlation pattern in Kandy, Sri Lanka, compare the results with results of similar studies, and establish ways for better control and prevention of dengue. We collected data on reported dengue cases in Kandy and mid-year population data from 2003 to 2012, and calculated weekly incidences. We obtained daily weather data from two weather stations and converted it into weekly data. We studied correlation patterns between dengue incidence and weather variables using the wavelet time series analysis, and then calculated cross-correlation coefficients to find magnitudes of correlations. We found a positive correlation between dengue incidence and rainfall in millimeters, the number of rainy and wet days, the minimum temperature, and the night and daytime, as well as average, humidity, mostly with a five- to seven-week lag. Additionally, we found correlations between dengue incidence and maximum and average temperatures, hours of sunshine, and wind, with longer lag periods. Dengue incidences showed a negative correlation with wind run. Our results showed that rainfall, temperature, humidity, hours of sunshine, and wind are correlated with local dengue incidence. We have suggested ways to improve dengue management routines and to control it in these times of global warming. We also noticed that the results of dengue weather correlation studies can vary depending on the data analysis.

Elements of a predictive model for determining beach closures on a real time basis: the case of 63rd Street Beach Chicago

USGS Publications Warehouse

Olyphant, Greg A.; Whitman, Richard L.

2004-01-01

Data on hydrometeorological conditions and E. coli concentration were simultaneously collected on 57 occasions during the summer of 2000 at 63rd Street Beach, Chicago, Illinois. The data were used to identify and calibrate a statistical regression model aimed at predicting when the bacterial concentration of the beach water was above or below the level considered safe for full body contact. A wide range of hydrological, meteorological, and water quality variables were evaluated as possible predictive variables. These included wind speed and direction, incoming solar radiation (insolation), various time frames of rainfall, air temperature, lake stage and wave height, and water temperature, specific conductance, dissolved oxygen, pH, and turbidity. The best-fit model combined real-time measurements of wind direction and speed (onshore component of resultant wind vector), rainfall, insolation, lake stage, water temperature and turbidity to predict the geometric mean E.coliconcentration in the swimming zone of the beach. The model, which contained both additive and multiplicative (interaction) terms, accounted for 71% of the observed variability in the log E. coliconcentrations. A comparison between model predictions of when the beach should be closed and when the actualbacterial concentrations were above or below the 235 cfu 100 ml-1 threshold value, indicated that the model accurately predicted openingsversus closures 88% of the time.

Based on the rainfall system platform raindrops research and analysis of pressure loss

NASA Astrophysics Data System (ADS)

Cao, Gang; Sun, Jian

2018-01-01

With the rapid development of China’s military career, land, sea and air force all services and equipment of modern equipment need to be in the rain test, and verify its might suffer during transportation, storage or use a different environment temperature lower water or use underwater, the water is derived from the heavy rain, the wind and rain, sprinkler system, splash water, water wheel, a violent shock waves or use underwater, etcTest the product performance and quality, under the condition of rainfall system platform in the process of development, how to control the raindrops pressure loss becomes the key to whether the system can simulate the real rainfall [1], this paper is according to the rainfall intensity, nozzle flow resistance, meet water flow of rain pressure loss calculation and analysis, and system arrangement of the optimal solution of rainfall is obtained [2].

Stable isotope ratios in rainfall and water vapour at Bangalore, Southern India during the monsoon period of 2013

NASA Astrophysics Data System (ADS)

Peethambaran, Rahul; Ghosh, Prosenjit

2015-04-01

Rainwater and water vapour were collected during monsoon rainfall from Bangalore station to identifying the signature of moisture sources. Moisture responsible for the rainfall originates from Arabian Sea and Bay of Bengal and advected to the station together with vapour generated from the local . Total no of samples includes 72 for water vapour and 81 for rainwater respectively. The mean difference between water vapour and rainwater was found to be -13.27±2.5 ‰ for δ18O, -100±9 ‰ for δD, which was calculated from monthly mean values of water vapour and rainwater. The most enriched samples of rainwater and water vapour were found during the pre monsoon months which correspond to temperature maximum at the study location. Lighter isotopic ratios were recorded in samples collected during the starting of monsoon showers which goes to further depletion in δ18O during the period of post monsoon. This was mainly due to the change in the prevailing wind direction from southwest to northeast. Local Meteoric Water Line (LMWL) generated for rainwater (d = 7.49 δ 18O + 5.2555, R² = 0.93) equation suggesting enrichment due to evaporation. Local Vapour Line (LVL) (d = 7.5248 δ 18O + 6.6534,R² = 0.8957) indicates the dominance of vapor from local source. The time series of d-xcess of rainwater and water vapor reveals large variability, coinciding with the presence of transported and local sources. It was observed that rainwater and water vapor exhibits higher values indicating re-evaporation from the region. Repetition of this feature demonstrated pattern of moisture recycling in the atmosphere and the contribution of continental evaporation and transpiration. The sensitivity of isotopes to the sudden change in wind direction was documented by an abrupt variations in the isotope values. Such changes in wind patterns were mostly associated with the prevalence of low pressure depression systems during the monsoon periods. Detailed analysis on role of wind patterns and air parcel trajectories, atmospheric parameters such as rainfall, temperature and relative humidity and quantitative estimation of local source moisture source contributions will be discussed at the time of presentation.

Interannual and intra-annual variability of rainfall in Haiti (1905-2005)

NASA Astrophysics Data System (ADS)

Moron, Vincent; Frelat, Romain; Jean-Jeune, Pierre Karly; Gaucherel, Cédric

2015-08-01

The interannual variability of annual and monthly rainfall in Haiti is examined from a database of 78 rain gauges in 1905-2005. The spatial coherence of annual rainfall is rather low, which is partly due to Haiti's rugged landscape, complex shoreline, and surrounding warm waters (mean sea surface temperatures >27 °C from May to December). The interannual variation of monthly rainfall is mostly shaped by the intensity of the low-level winds across the Caribbean Sea, leading to a drier- (or wetter-) than-average rainy season associated with easterly (or westerly) anomalies, increasing (or decreasing) winds. The varying speed of low-level easterlies across the Caribbean basin may reflect at least four different processes during the year: (1) an anomalous trough/ridge over the western edge of the Azores high from December to February, peaking in January; (2) a zonal pressure gradient between Eastern Pacific and the tropical Northern Atlantic from May/June to September, with a peak in August (i.e. lower-than-average rainfall in Haiti is associated with positive sea level pressure anomalies over the tropical North Atlantic and negative sea level pressure anomalies over the Eastern Pacific); (3) a local ocean-atmosphere coupling between the speed of the Caribbean Low Level Jet and the meridional sea surface temperature (SST) gradient across the Caribbean basin (i.e. colder-than-average SST in the southern Caribbean sea is associated with increased easterlies and below-average rainfall in Haiti). This coupling is triggered when the warmest Caribbean waters move northward toward the Gulf of Mexico; (4) in October/November, a drier- (or wetter-) than-usual rainy season is related to an almost closed anticyclonic (or cyclonic) anomaly located ENE of Haiti on the SW edge of the Azores high. This suggests a main control of the interannual variations of rainfall by intensity, track and/or recurrence of tropical depressions traveling northeast of Haiti. During this period, the teleconnection of Haitian rainfall with synchronous Atlantic and Eastern Pacific SST is at a minimum.

Quasi-Equilibrium States in the Tropics Simulated by a Cloud-Resolving Model. Part 1; Specific Features and Budget Analysis

NASA Technical Reports Server (NTRS)

Shie, C.-L.; Tao, W.-K.; Simpson, J.; Sui, C.-H.; Starr, David OC. (Technical Monitor)

2001-01-01

A series of long-term integrations using the two-dimensional Goddard Cumulus Ensemble (GCE) model were performed by altering imposed environmental components to produce various quasi-equilibrium thermodynamic states. Model results show that the genesis of a warm/wet quasi-equilibrium state is mainly due to either strong vertical wind shear (from nudging) or large surface fluxes (from strong surface winds), while a cold/dry quasi-equilibrium state is attributed to a remarkably weakened mixed-wind shear (from vertical mixing due to deep convection) along with weak surface winds. In general, latent heat flux and net large-scale temperature forcing, the two dominant physical processes, dominate in the beginning stage of the simulated convective systems, then considerably weaken in the final stage, which leads to quasi-equilibrium states. A higher thermodynamic regime is found to produce a larger rainfall amount, as convective clouds are the leading source of rainfall over stratiform clouds even though the former occupy much less area. Moreover, convective clouds are more likely to occur in the presence of strong surface winds (latent heat flux), while stratiform clouds (especially the well-organized type) are favored in conditions with strong wind shear (large-scale forcing). The convective systems, which consist of distinct cloud types due to the variation in horizontal winds, are also found to propagate differently. Accordingly, convective systems with mixed-wind shear generally propagate in the direction of shear, while the system with strong (multidirectional) wind shear propagates in a more complex way. Based on the results from the temperature (Q1) and moisture (Q2) budgets, cloud-scale eddies are found to act as a hydrodynamic 'vehicle' that cascades the heat and moisture vertically. Several other specific features such as atmospheric stability, CAPE, and mass fluxes are also investigated and found to be significantly different between diverse quasi-equilibrium states. Detailed comparisons between the various states are presented.

Asthma and climatic conditions: experience from Bermuda, an isolated island community.

PubMed Central

Carey, M J; Cordon, I

1986-01-01

A retrospective study of patients attending the emergency department with acute asthma was performed in Bermuda. Climatic data (barometric pressure, rainfall, humidity, and wind strength and direction) were obtained and compared with frequency of exacerbations of asthma. Three factors--namely, relative humidity, average daily temperature, and northeasterly winds--were found to be related to worsening asthma. Owing to Bermuda's lack of pollution and aeroallergens it was thought that these weather parameters had a direct effect on the asthmatic population. PMID:3094682

How East Asian westerly jet's meridional position affects the summer rainfall in Yangtze-Huaihe River Valley?

NASA Astrophysics Data System (ADS)

Wang, Shixin; Zuo, Hongchao; Zhao, Shuman; Zhang, Jiankai; Lu, Sha

2017-03-01

Existing studies show that the change in the meridional position of East Asian westerly jet (EAWJ) is associated with rainfall anomalies in Yangtze-Huaihe River Valley (YHRV) in summer. However, the dynamic mechanism has not been resolved yet. The present study reveals underlying mechanisms for this impact for early summer and midsummer, separately. Mechanism1: associated with EAWJ's anomalously southward displacement, the 500-hPa westerly wind over YHRV is strengthened through midtropospheric horizontal circulation anomalies; the westerly anomalies are related to the formation of warm advection anomalies over YHRV, which cause increased rainfall through adiabatic ascent motion and convective activities; the major difference in these processes between early summer and midsummer is the midtropospheric circulation anomaly pattern. Mechanism 2: associated with EAWJ's anomalously southward displacement, the large day-to-day variability of midtropospheric temperature advection in midlatitudes is displaced southward by the jet's trapping transient eddies; this change enhances the day-to-day variability of temperature advection over YHRV, which in turn causes the increased rainfall in most part of YHRV through "lower-bound effect" (rainfall amount can not become negative); there is not much difference in these processes between early summer and midsummer.

Exploring the spatio-temporal relationship between two key aeroallergens and meteorological variables in the United Kingdom

NASA Astrophysics Data System (ADS)

Khwarahm, Nabaz; Dash, Jadunandan; Atkinson, Peter M.; Newnham, R. M.; Skjøth, C. A.; Adams-Groom, B.; Caulton, Eric; Head, K.

2014-05-01

Constructing accurate predictive models for grass and birch pollen in the air, the two most important aeroallergens, for areas with variable climate conditions such as the United Kingdom, require better understanding of the relationships between pollen count in the air and meteorological variables. Variations in daily birch and grass pollen counts and their relationship with daily meteorological variables were investigated for nine pollen monitoring sites for the period 2000-2010 in the United Kingdom. An active pollen count sampling method was employed at each of the monitoring stations to sample pollen from the atmosphere. The mechanism of this method is based on the volumetric spore traps of Hirst design (Hirst in Ann Appl Biol 39(2):257-265, 1952). The pollen season (start date, finish date) for grass and birch were determined using a first derivative method. Meteorological variables such as daily rainfall; maximum, minimum and average temperatures; cumulative sum of Sunshine duration; wind speed; and relative humidity were related to the grass and birch pollen counts for the pre-peak, post peak and the entire pollen season. The meteorological variables were correlated with the pollen count data for the following temporal supports: same-day, 1-day prior, 1-day mean prior, 3-day mean prior, 7-day mean prior. The direction of influence (positive/negative) of meteorological variables on pollen count varied for birch and grass, and also varied when the pollen season was treated as a whole season, or was segmented into the pre-peak and post-peak seasons. Maximum temperature, sunshine duration and rainfall were the most important variables influencing the count of grass pollen in the atmosphere. Both maximum temperature (pre-peak) and sunshine produced a strong positive correlation, and rain produced a strong negative correlation with grass pollen count in the air. Similarly, average temperature, wind speed and rainfall were the most important variables influencing the count of birch pollen in the air. Both wind speed and rain produced a negative correlation with birch pollen count in the air and average temperature produced a positive correlation.

Identification of tipping elements of the Indian Summer Monsoon using climate network approach

NASA Astrophysics Data System (ADS)

Stolbova, Veronika; Surovyatkina, Elena; Kurths, Jurgen

2015-04-01

Spatial and temporal variability of the rainfall is a vital question for more than one billion of people inhabiting the Indian subcontinent. Indian Summer Monsoon (ISM) rainfall is crucial for India's economy, social welfare, and environment and large efforts are being put into predicting the Indian Summer Monsoon. For predictability of the ISM, it is crucial to identify tipping elements - regions over the Indian subcontinent which play a key role in the spatial organization of the Indian monsoon system. Here, we use climate network approach for identification of such tipping elements of the ISM. First, we build climate networks of the extreme rainfall, surface air temperature and pressure over the Indian subcontinent for pre-monsoon, monsoon and post-monsoon seasons. We construct network of extreme rainfall event using observational satellite data from 1998 to 2012 from the Tropical Rainfall Measuring Mission (TRMM 3B42V7) and reanalysis gridded daily rainfall data for a time period of 57 years (1951-2007) (Asian Precipitation Highly Resolved Observational Data Integration Towards the Evaluation of Water Resources, APHRODITE). For the network of surface air temperature and pressure fields, we use re-analysis data provided by the National Center for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR). Second, we filter out data by coarse-graining the network through network measures, and identify tipping regions of the ISM. Finally, we compare obtained results of the network analysis with surface wind fields and show that occurrence of the tipping elements is mostly caused by monsoonal wind circulation, migration of the Intertropical Convergence Zone (ITCZ) and Westerlies. We conclude that climate network approach enables to select the most informative regions for the ISM, providing realistic description of the ISM dynamics with fewer data, and also help to identify tipping regions of the ISM. Obtained tipping elements deserve a special attention for the meteorologists and can be used as markers of the ISM variability.

Panic anxiety, under the weather?

NASA Astrophysics Data System (ADS)

Bulbena, A.; Pailhez, G.; Aceña, R.; Cunillera, J.; Rius, A.; Garcia-Ribera, C.; Gutiérrez, J.; Rojo, C.

2005-03-01

The relationship between weather conditions and psychiatric disorders has been a continuous subject of speculation due to contradictory findings. This study attempts to further clarify this relationship by focussing on specific conditions such as panic attacks and non-panic anxiety in relation to specific meteorological variables. All psychiatric emergencies attended at a general hospital in Barcelona (Spain) during 2002 with anxiety as main complaint were classified as panic or non-panic anxiety according to strict independent and retrospective criteria. Both groups were assessed and compared with meteorological data (wind speed and direction, daily rainfall, temperature, humidity and solar radiation). Seasons and weekend days were also included as independent variables. Non-parametric statistics were used throughout since most variables do not follow a normal distribution. Logistic regression models were applied to predict days with and without the clinical condition. Episodes of panic were three times more common with the poniente wind (hot wind), twice less often with rainfall, and one and a half times more common in autumn than in other seasons. These three trends (hot wind, rainfall and autumn) were accumulative for panic episodes in a logistic regression formula. Significant reduction of episodes on weekends was found only for non-panic episodes. Panic attacks, unlike other anxiety episodes, in a psychiatric emergency department in Barcelona seem to show significant meteorotropism. Assessing specific disorders instead of overall emergencies or other variables of a more general quality could shed new light on the relationship between weather conditions and behaviour.

The role of external forcing and Pacific trade winds in recent changes of the global climate system

NASA Astrophysics Data System (ADS)

Friedman, Andrew; Gastineau, Guillaume; Khodri, Myriam

2017-04-01

The Pacific trade winds experienced an unprecedented strengthening since the mid 1990s. Several studies have proposed that the increased Pacific trade winds were associated with the reduced rate of global mean surface temperature warming in the first decade of the 21st century, as well as far-reaching atmospheric teleconnections. We designed a set of ensemble partial coupling experiments using the IPSL-CM5A-LR coupled model that allow us to cleanly distinguish the influence of Pacific trade wind variability from that of external forcing over the past few decades. In this study, we quantify the respective impacts of these processes on surface temperature, ocean heat content, and atmospheric teleconnections. We designed two ensembles of coupled simulations using partial coupling with the IPSL-CM5A-LR model to separate the Pacific internal variability and that of external radiative forcing. We prescribe surface wind stress in the tropical Pacific (20°S to 20°N) from 1979-2014 in two ensembles of 30 members each: (1) Prescribed climatological model wind stress, which allows us to estimate the influence of external radiative forcing in the absence of variability within the Pacific Ocean. (2) Wind stress anomalies from ERA-Interim reanalysis added to the model wind stress climatology, which accounts for the effects of both external radiative forcing and the wind stress variability. We find that the observed wind stress anomalies account for the pattern of eastern tropical Pacific cooling when compared to the climatology experiment, so that it resembles the observed trends from 1992-2011. The tropical Pacific shows dominant heat uptake in the western Pacific above the 20°C isotherm, which contributed to slow the warming of tropical SST during the 2000s. The trade wind increase is associated with a strengthening of the Pacific Walker circulation, and zonal shifts in tropical rainfall. Despite tropical SST biases which affect the response of tropical rainfall and the location of deep convection, the wind stress anomaly forcing effectively simulates the wave train pattern emanating from the tropical Pacific, and associated extratropical teleconnections such as a weakening of the Aleutian Low and drought in North America.

Near-surface salinity and temperature structure observed with dual-sensor drifters in the subtropical South Pacific

NASA Astrophysics Data System (ADS)

Dong, Shenfu; Volkov, Denis; Goni, Gustavo; Lumpkin, Rick; Foltz, Gregory R.

2017-07-01

Three surface drifters equipped with temperature and salinity sensors at 0.2 and 5 m depths were deployed in April/May 2015 in the subtropical South Pacific with the objective of measuring near-surface salinity differences seen by satellite and in situ sensors and examining the causes of these differences. Measurements from these drifters indicate that water at a depth of 0.2 m is about 0.013 psu fresher than at 5 m and about 0.024°C warmer. Events with large temperature and salinity differences between the two depths are caused by anomalies in surface freshwater and heat fluxes, modulated by wind. While surface freshening and cooling occurs during rainfall events, surface salinification is generally observed under weak wind conditions (≤4 m/s). Further examination of the drifter measurements demonstrates that (i) the amount of surface freshening and strength of the vertical salinity gradient heavily depend on wind speed during rain events, (ii) salinity differences between 0.2 and 5 m are positively correlated with the corresponding temperature differences for cases with surface salinification, and (iii) temperature exhibits a diurnal cycle at both depths, whereas the diurnal cycle of salinity is observed only at 0.2 m when the wind speed is less than 6 m/s. The amplitudes of the diurnal cycles of temperature at both depths decrease with increasing wind speed. The mean diurnal cycle of surface salinity is dominated by events with winds less than 2 m/s.

Near-surface Salinity and Temperature structure Observed with Dual-Sensor Drifters in the Subtropical South Pacific

NASA Astrophysics Data System (ADS)

Dong, S.; Volkov, D.; Goni, G. J.; Lumpkin, R.; Foltz, G. R.

2017-12-01

Three surface drifters equipped with temperature and salinity sensors at 0.2 m and 5 m depths were deployed in April/May 2015 in the subtropical South Pacific with the objective of measuring near-surface salinity differences seen by satellite and in situ sensors and examining the causes of these differences. Measurements from these drifters indicate that water at a depth of 0.2 m is about 0.013 psu fresher than at 5 m and about 0.024°C warmer. Events with large temperature and salinity differences between the two depths are caused by anomalies in surface freshwater and heat fluxes, modulated by wind. While surface freshening and cooling occurs during rainfall events, surface salinification is generally observed under weak wind conditions (≤4 m/s). Further examination of the drifter measurements demonstrates that (i) the amount of surface freshening and strength of the vertical salinity gradient heavily depend on wind speed during rain events, (ii) salinity differences between 0.2 m and 5 m are positively correlated with the corresponding temperature differences for cases with surface salinification, and (iii) temperature exhibits a diurnal cycle at both depths, whereas the diurnal cycle of salinity is observed only at 0.2 m when the wind speed is less than 6 m/s. The amplitudes of the diurnal cycles of temperature at both depths decrease with increasing wind speed. The mean diurnal cycle of surface salinity is dominated by events with winds less than 2 m/s.

The calculation from weather records of the requirement for clothing insulation

NASA Astrophysics Data System (ADS)

Mount, L. E.; Brown, D.

1985-12-01

Standard meteorological measurements of dry bulb temperature, wind speed, sunshine, cloud cover and rainfall are used to calculate the clothing insulation required by man for thermal comfort under given weather conditions. The calculation is based on earlier work on the effect of weather on sensible (non-evaporative) heat loss from sheep, which used the relation between heat flow, thermal insulation and the difference between body and environmental temperatures. Clothing insulation for man is estimated in two ways: as clothing (Ic) that is impervious to the effects of wind and rain; and as the equivalent depth of sheep fleece (fm), which is not impervious. This allows the assessment of wind chill for a range of clothing of varied penetration by wind instead of for only one type of garment. Results are given as daily means calculated from hourly measurements throughout 1973 for Plymouth (on the south coast of Britain) and Aberdeen (on the far northeast coast of Britain). Wind chill is estimated both by its effect on fm requirement and by the fall in air temperature that would be needed to produce under still-air conditions the same demand for fm that occurs in the actual environment. The monthly mean fm requirement is reduced by about 40% when the effect of wind is removed. When wind chill is estimated as an equivalent fall in air temperature it approximates to 1 K per knot wind speed measured at the standard meteorological height of 10 m.

Remote rainfall sensing for landslide hazard analysis

USGS Publications Warehouse

Wieczorek, Gerald F.; McWreath, Harry; Davenport, Clay

2001-01-01

Methods of assessing landslide hazards and providing warnings are becoming more advanced as remote sensing of rainfall provides more detailed temporal and spatial data on rainfall distribution. Two recent landslide disasters are examined noting the potential for using remotely sensed rainfall data for landslide hazard analysis. For the June 27, 1995, storm in Madison County, Virginia, USA, National Weather Service WSR-88D Doppler radar provided rainfall estimates based on a relation between cloud reflectivity and moisture content on a 1 sq. km. resolution every 6 minutes. Ground-based measurements of rainfall intensity and precipitation total, in addition to landslide timing and distribution, were compared with the radar-derived rainfall data. For the December 14-16, 1999, storm in Vargas State, Venezuela, infrared sensing from the GOES-8 satellite of cloud top temperatures provided the basis for NOAA/NESDIS rainfall estimates on a 16 sq. km. resolution every 30 minutes. These rainfall estimates were also compared with ground-based measurements of rainfall and landslide distribution. In both examples, the remotely sensed data either overestimated or underestimated ground-based values by up to a factor of 2. The factors that influenced the accuracy of rainfall data include spatial registration and map projection, as well as prevailing wind direction, cloud orientation, and topography.

Near-surface Salinity and Temperature Structure Observed with Dual-Sensor Drifters in the Subtropical South Pacific

NASA Astrophysics Data System (ADS)

Dong, Shenfu; Goni, Gustavo; Volkov, Denis; Lumpkin, Rick; Foltz, Gregory

2017-04-01

Three surface drifters equipped with temperature and salinity sensors at 0.2 m and 5 m depths were deployed in April/May 2015 in the subtropical South Pacific Ocean with the objective of measuring near-surface salinity differences seen by satellite and in situ sensors and examining the causes of the differences. Measurements from these drifters indicate that, on average, water at a depth of 0.2 m is about 0.013 psu fresher than at 5 m and about 0.024°C warmer. Events with large temperature and salinity differences between the two depths often occur when surface winds are weak. In addition to the expected surface freshening and cooling during rainfall events, surface salinification occurs under weak wind conditions when there is strong surface warming that enhances evaporation and upper ocean stratification. Further examination of the drifter measurements demonstrate that (i) the amount of surface freshening and vertical salinity gradient heavily depend on wind speed during rain events, (ii) salinity differences between 0.2 m and 5 m are positively correlated with the corresponding temperature differences, and (iii) temperature exhibits a diurnal cycle at both depths, whereas the diurnal cycle of salinity is observed only at 0.2 m when the wind speed is less than 4 m/s. Its phase is consistent with diurnal changes in surface temperature-induced evaporation. Below a wind speed of 6 m/s, the amplitudes of the diurnal cycles of temperature at both depths decrease with increasing wind speed. Wind speed also affects the phasing of the diurnal cycle of T5m with the time of maximum T5m increasing gradually with decreasing wind speed. Wind speed does not affect the phasing of the diurnal cycle of T0.2m. At 0.2 m and 5 m, the diurnal cycle of temperature also depends on surface solar radiation, with the amplitude and time of diurnal maximum increasing as solar radiation increases.

Air temperature, wind speed, and wind direction in the National Petroleum Reserve—Alaska and the Arctic National Wildlife Refuge, 1998–2011

USGS Publications Warehouse

Urban, Frank E.; Clow, Gary D.

2013-01-01

This report provides air temperature, wind speed, and wind direction data collected on Federal lands in Arctic Alaska over the period August 1998 to July 2011 by the U.S. Department of the Interior's climate monitoring array, part of the Global Terrestrial Network for Permafrost. In addition to presenting data, this report also describes monitoring, data collection, and quality control methodology. This array of 16 monitoring stations spans 68.5°N to 70.5°N and 142.5°W to 161°W, an area of roughly 150,000 square kilometers. Climate summaries are presented along with provisional quality-controlled data. Data collection is ongoing and includes several additional climate variables to be released in subsequent reports, including ground temperature and soil moisture, snow depth, rainfall, up- and downwelling shortwave radiation, and atmospheric pressure. These data were collected by the U.S. Geological Survey in close collaboration with the Bureau of Land Management and the U.S. Fish and Wildlife Service.

Thermodynamic and dynamic structure of atmosphere over the east coast of Peninsular Malaysia during the passage of a cold surge

NASA Astrophysics Data System (ADS)

Samah, Azizan Abu; Babu, C. A.; Varikoden, Hamza; Jayakrishnan, P. R.; Hai, Ooi See

2016-08-01

An intense field observation was carried out for a better understanding of cold surge features over Peninsular Malaysia during the winter monsoon season. The study utilizes vertical profiles of temperature, humidity and wind at high vertical and temporal resolution over Kota Bharu, situated in the east coast of Peninsular Malaysia. LCL were elevated during the passage of the cold surge as the relative humidity values decreased during the passage of cold surge. Level of Free Convection were below 800 hPa and equilibrium levels were close to the LFC in most of the cases. Convective available potential energy and convection inhibition energy values were small during most of the observations. Absence of local heating and instability mechanism are responsible for the peculiar thermodynamic structure during the passage of the cold surge. The wind in the lower atmosphere became northeasterly and was strong during the entire cold surge period. A slight increase in temperature near the surface and a drop in temperature just above the surface were marked by the passage of the cold surge. A remarkable increase in specific humidity was observed between 970 and 900 hPa during the cold surge period. Further, synoptic scale features were analyzed to identify the mechanism responsible for heavy rainfall. Low level convergence, upper level divergence and cyclonic vorticity prevailed over the region during the heavy rainfall event. Dynamic structure of the atmosphere as part of the organized convection associated with the winter monsoon was responsible for the vertical lifting and subsequent rainfall.

Indian summer monsoon rainfall variability during 2014 and 2015 and associated Indo-Pacific upper ocean temperature patterns

NASA Astrophysics Data System (ADS)

Kakatkar, Rashmi; Gnanaseelan, C.; Chowdary, J. S.; Parekh, Anant; Deepa, J. S.

2018-02-01

In this study, factors responsible for the deficit Indian Summer Monsoon (ISM) rainfall in 2014 and 2015 and the ability of Indian Institute of Tropical Meteorology-Global Ocean Data Assimilation System (IITM-GODAS) in representing the oceanic features are examined. IITM-GODAS has been used to provide initial conditions for seasonal forecast in India during 2014 and 2015. The years 2014 and 2015 witnessed deficit ISM rainfall but were evolved from two entirely different preconditions over Pacific. This raises concern over the present understanding of the role of Pacific Ocean on ISM variability. Analysis reveals that the mechanisms associated with the rainfall deficit over the Indian Subcontinent are different in the two years. It is found that remote forcing in summer of 2015 due to El Niño is mostly responsible for the deficit monsoon rainfall through changes in Walker circulation and large-scale subsidence. In the case of the summer of 2014, both local circulation with anomalous anticyclone over central India and intrusion of mid-latitude dry winds from north have contributed for the deficit rainfall. In addition to the above, Tropical Indian Ocean (TIO) sea surface temperature (SST) and remote forcing from Pacific Ocean also modulated the ISM rainfall. It is observed that Pacific SST warming has extended westward in 2014, making it a basin scale warming unlike the strong El Niño year 2015. The eastern equatorial Indian Ocean is anomalously warmer than west in summer of 2014, and vice versa in 2015. These differences in SST in both tropical Pacific and TIO have considerable impact on ISM rainfall in 2014 and 2015. The study reveals that initializing coupled forecast models with proper upper ocean temperature over the Indo-Pacific is therefore essential for improved model forecast. It is important to note that the IITM-GODAS which assimilates only array for real-time geostrophic oceanography (ARGO) temperature and salinity profiles could capture most of the observed surface and subsurface temperature variations from early spring to summer during the years 2014 and 2015 over the Indo-Pacific region. This study highlights the importance of maintaining observing systems such as ARGO for accurate monsoon forecast.

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.

Prediction model for peninsular Indian summer monsoon rainfall using data mining and statistical approaches

NASA Astrophysics Data System (ADS)

Vathsala, H.; Koolagudi, Shashidhar G.

2017-01-01

In this paper we discuss a data mining application for predicting peninsular Indian summer monsoon rainfall, and propose an algorithm that combine data mining and statistical techniques. We select likely predictors based on association rules that have the highest confidence levels. We then cluster the selected predictors to reduce their dimensions and use cluster membership values for classification. We derive the predictors from local conditions in southern India, including mean sea level pressure, wind speed, and maximum and minimum temperatures. The global condition variables include southern oscillation and Indian Ocean dipole conditions. The algorithm predicts rainfall in five categories: Flood, Excess, Normal, Deficit and Drought. We use closed itemset mining, cluster membership calculations and a multilayer perceptron function in the algorithm to predict monsoon rainfall in peninsular India. Using Indian Institute of Tropical Meteorology data, we found the prediction accuracy of our proposed approach to be exceptionally good.

Range Atmospheric and Oceanic Environmental Support Capabilities

DTIC Science & Technology

2011-12-01

Precipitation location/intensity, thunderstorm location/intensity, rainfall/flash flood warning, hydrometer characterization, wind warnings, and...intensity, lightning monitoring, rainfall and flash flood warning, hydrometer characterization, and wind warnings. b. Satellite: MTSAT, GOES-10

Effect of topography on microclimate in southwestern Wisconsin.

Treesearch

Richard S. Sartz

1972-01-01

Ridge and coulee terrain has little effect on point rainfall, but snowpack accumulation is affected by degree of slope and aspect. North slopes accumulate about 50% more snow. Soil water depletion is little affected by aspect. South slopes receive more insulation than north slopes, but temperature differences are slight and may result more from wind differences than...

Merging weather data with materials response data during outdoor exposure

Treesearch

R. Sam Williams; Anand Sanadi; Corey Halpin; Christopher White

2002-01-01

As part of an outdoor exposure protocol for a study of sealants, a full weather station was installed at the Forest Products Laboratory field test site near Madison, Wisconsin. Tem-perature, relative humidity, rainfall, ultraviolet (UV) radiation at 18 different wavelengths, and wind speed and direction are continuously measured. Using a specially designed apparatus,...

Isotopic composition of waters from Ethiopia and Kenya: Insights into moisture sources for eastern Africa

NASA Astrophysics Data System (ADS)

Levin, Naomi E.; Zipser, Edward J.; Cerling, Thure E.

2009-12-01

Oxygen and deuterium isotopic values of meteoric waters from Ethiopia are unusually high when compared to waters from other high-elevation settings in Africa and worldwide. These high values are well documented; however, the climatic processes responsible for the isotopic anomalies in Ethiopian waters have not been thoroughly investigated. We use isotopic data from waters and remote data products to demonstrate how different moisture sources affect the distribution of stable isotopes in waters from eastern Africa. Oxygen and deuterium stable isotopic data from 349 surface and near-surface groundwaters indicate isotopic distinctions between waters in Ethiopia and Kenya and confirm the anomalous nature of Ethiopian waters. Remote data products from the Tropical Rainfall Measuring Mission (TRMM) and National Centers for Environmental Prediction (NCEP) reanalysis project show strong westerly and southwesterly components to low-level winds during precipitation events in western and central Ethiopia. This is in contrast to the easterly and southeasterly winds that bring rainfall to Kenya and southeastern Ethiopia. Large regions of high equivalent potential temperatures (θe) at low levels over the Sudd and the Congo Basin demonstrate the potential for these areas as sources of moisture and convective instability. The combination of wind direction data from Ethiopia and θe distribution in Africa indicates that transpired moisture from the Sudd and the Congo Basin is likely responsible for the high isotopic values of rainfall in Ethiopia.

[Impact of wind-water alternate erosion on the characteristics of sediment particles].

PubMed

Tuo, Deng-Feng; Xu, Ming-Xiang; Ma, Xin-Xin; Zheng, Shi-Qing

2014-02-01

Wind and water are the two dominant erosion agents that caused soil and water losses in the wind-water alternate erosion region on the Loess Plateau. It is meaningful to study the impact of wind-water alternate erosion on the characteristics of soil particles for understanding the response of soil quality and environment to erosion. Through wind tunnel combined rainfall simulation, this paper studied the characteristics of the erosive sediment particles under the effect of wind-water alternate erosion. The results showed that the particles of 0-1 cm soil were coarsened by wind erosion at the wind speeds of 11 and 14 m x s(-1) compared with no wind erosion. Soil fine particles (< 0.01 mm) decreased by 9.8%-10.8%, and coarse particles (> 0.05 mm) increased by 16.8%-20.8%. The physical property of surface soil was changed by the wind erosion, which, in turn, caused an increase in finer particles content in the sediment. Compared with no wind erosion, fine particles (< 0.01 mm) in sediment under the water-wind alternate erosion increased by 2.7%-18.9% , and coarse particles (> 0.05 mm) decreased by 3.7%-9.3%. However, the changing trend of erosive sediment particles after the wind erosion at wind speeds of 11 and 14 m x s(-1) was different along with the rainfall intensity and duration. The erosive sediment particles at the rainfall intensities of 60, 80, 100 mm x h(-1) changed to greater extents than at the 150 mm x h(-1) rainfall intensity with longer than 15 min runoff flowing.

Global meteorological influences on the record UK rainfall of winter 2013-14

NASA Astrophysics Data System (ADS)

Knight, Jeff R.; Maidens, Anna; Watson, Peter A. G.; Andrews, Martin; Belcher, Stephen; Brunet, Gilbert; Fereday, David; Folland, Chris K.; Scaife, Adam A.; Slingo, Julia

2017-07-01

The UK experienced record average rainfall in winter 2013-14, leading to widespread and prolonged flooding. The immediate cause of this exceptional rainfall was a very strong and persistent cyclonic atmospheric circulation over the North East Atlantic Ocean. This was related to a very strong North Atlantic jet stream which resulted in numerous damaging wind storms. These exceptional meteorological conditions have led to renewed questions about whether anthropogenic climate change is noticeably influencing extreme weather. The regional weather pattern responsible for the extreme UK winter coincided with highly anomalous conditions across the globe. We assess the contributions from various possible remote forcing regions using sets of ocean-atmosphere model relaxation experiments, where winds and temperatures are constrained to be similar to those observed in winter 2013-14 within specified atmospheric domains. We find that influences from the tropics were likely to have played a significant role in the development of the unusual extra-tropical circulation, including a role for the tropical Atlantic sector. Additionally, a stronger and more stable stratospheric polar vortex, likely associated with a strong westerly phase of the stratospheric Quasi-Biennial Oscillation (QBO), appears to have contributed to the extreme conditions. While intrinsic climatic variability clearly has the largest effect on the generation of extremes, results from an analysis which segregates circulation-related and residual rainfall variability suggest that emerging climate change signals made a secondary contribution to extreme rainfall in winter 2013-14.

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.

Organization of vertical shear of wind and daily variability of monsoon rainfall

NASA Astrophysics Data System (ADS)

Gouda, K. C.; Goswami, P.

2016-10-01

Very little is known about the mechanisms that govern the day to day variability of the Indian summer monsoon (ISM) rainfall; in the current dominant view, the daily rainfall is essentially a result of chaotic dynamics. Most studies in the past have thus considered monsoon in terms of its seasonal (June-September) or monthly rainfall. We show here that the daily rainfall in June is associated with vertical shear of horizontal winds at specific scales. While vertical shear had been used in the past to investigate interannual variability of seasonal rainfall, rarely any effort has been made to examine daily rainfall. Our work shows that, at least during June, the daily rainfall variability of ISM rainfall is associated with a large scale dynamical coherence in the sense that the vertical shear averaged over large spatial extents are significantly correlated with area-averaged daily rainfall. An important finding from our work is the existence of a clearly delineated monsoon shear domain (MSD) with strong coherence between area-averaged shear and area-averaged daily rainfall in June; this association of daily rainfall is not significant with shear over only MSD. Another important feature is that the association between daily rainfall and vertical shear is present only during the month of June. Thus while ISM (June-September) is a single seasonal system, it is important to consider the dynamics and variation of June independently of the seasonal ISM rainfall. The association between large-scale organization of circulation and daily rainfall is suggested as a basis for attempting prediction of daily rainfall by ensuring accurate simulation of wind shear.

Use of geostationary meteorological satellite images in convective rain estimation for flash-flood forecasting

NASA Astrophysics Data System (ADS)

Wardah, T.; Abu Bakar, S. H.; Bardossy, A.; Maznorizan, M.

2008-07-01

SummaryFrequent flash-floods causing immense devastation in the Klang River Basin of Malaysia necessitate an improvement in the real-time forecasting systems being used. The use of meteorological satellite images in estimating rainfall has become an attractive option for improving the performance of flood forecasting-and-warning systems. In this study, a rainfall estimation algorithm using the infrared (IR) information from the Geostationary Meteorological Satellite-5 (GMS-5) is developed for potential input in a flood forecasting system. Data from the records of GMS-5 IR images have been retrieved for selected convective cells to be trained with the radar rain rate in a back-propagation neural network. The selected data as inputs to the neural network, are five parameters having a significant correlation with the radar rain rate: namely, the cloud-top brightness-temperature of the pixel of interest, the mean and the standard deviation of the temperatures of the surrounding five by five pixels, the rate of temperature change, and the sobel operator that indicates the temperature gradient. In addition, three numerical weather prediction (NWP) products, namely the precipitable water content, relative humidity, and vertical wind, are also included as inputs. The algorithm is applied for the areal rainfall estimation in the upper Klang River Basin and compared with another technique that uses power-law regression between the cloud-top brightness-temperature and radar rain rate. Results from both techniques are validated against previously recorded Thiessen areal-averaged rainfall values with coefficient correlation values of 0.77 and 0.91 for the power-law regression and the artificial neural network (ANN) technique, respectively. An extra lead time of around 2 h is gained when the satellite-based ANN rainfall estimation is coupled with a rainfall-runoff model to forecast a flash-flood event in the upper Klang River Basin.

Seasat microwave wind and rain observations in severe tropical and midlatitude marine storms

NASA Technical Reports Server (NTRS)

Black, P. G.; Hawkins, J. D.; Gentry, R. C.; Cardone, V. J.

1985-01-01

Initial results of studies concerning Seasat measurements in and around tropical and severe midlatitude cyclones over the open ocean are presented, together with an assessment of their accuracy and usefulness. Complementary measurements of surface wind speed and direction, rainfall rate, and the sea surface temperature obtained with the Seasat-A Satellite Scatterometer (SASS), the Scanning Multichannel Microwave Radiometer (SMMR), and the Seasat SAR are analyzed. The Seasat data for the Hurrricanes Fico, Ella, and Greta and the QE II storm are compared with data obtained from aircraft, buoys, and ships. It is shown that the SASS-derived wind speeds are accurate to within 10 percent, and the directions are accurate to within 20 percent. In general, the SASS estimates tend to measure light winds too high and intense winds too low. The errors of the SMMR-derived measurements of the winds in hurricanes tend to be higher than those of the SASS-derived measurements.

Biophysical response of dryland soils to rainfall: implications for wind erosion

NASA Astrophysics Data System (ADS)

Bullard, J. E.; Strong, C. L.; Aubault, H.

2016-12-01

Dryland soils can be highly susceptible to wind erosion due to low vegetation cover. The formation of physical and biological soil crusts between vascular plants can exert some control on the soil surface erodibility. The development of these crusts is highly dependent on rainfall which causes sediment compaction and aggregate breakdown, and triggers photosynthetic activity and an increase soil organic matter within biological soil crusts. Using controlled field experiments, this study tests how biological soil crusts in different dryland geomorphic settings respond to various rainfall amounts (0, 5 or 10 mm) and how this in turn affects the resistance of soils to wind erosion. Results show that 10 mm of rainfall triggers more intense photosynthetic activity (high fluorescence) and a greater increase in extracellular polysaccharide content in biological crusts than 5 mm of rainfall but that the duration of photosynthetic activity is comparable for both quantities of rain. These biological responses have little impact on surface resistance, but results show that soils are more susceptible to wind erosion after rainfall events than in their initial dry state. This unexpected result could be explained by the detachment of surface sediments by raindrop impact and overland flow. The study highlights the complexity of soil erodibility at small scale which is driven by rain, wind and crust, and a necessity to understand how the spatial heterogeneity of crust and their ecophysiology alters small scale processes.

Month-to-month variability of Indian summer monsoon rainfall in 2016: role of the Indo-Pacific climatic conditions

NASA Astrophysics Data System (ADS)

Chowdary, Jasti S.; Srinivas, G.; Du, Yan; Gopinath, K.; Gnanaseelan, C.; Parekh, Anant; Singh, Prem

2018-03-01

Indian summer monsoon (ISM) rainfall during 2016 exhibited a prominent month-to-month fluctuations over India, with below normal rainfall in June and August and above normal rainfall in July. The factors determining the month-to-month fluctuations in ISM rainfall during 2016 are investigated with main focus on the Indo-Pacific climatic anomalies. Warm sea surface temperature (SST) anomalies associated with super El Niño 2015 disappeared by early summer 2016 over the central and eastern Pacific. On the other hand, negative Indian Ocean dipole (IOD) like SST anomaly pattern over the equatorial Indian Ocean and anomalous anticyclonic circulation over the western North Pacific (WNP) are reported in summer 2016 concurrently with decaying El Niño/developing La Niña phase. Observations revealed that the low rainfall over central north India in June is due to moisture divergence caused by the westward extension of ridge corresponding to WNP anticyclone and subsidence induced by local Hadley cell partly related to negative IOD. Low level convergence of southeasterly wind from Bay of Bengal associated with weak WNP anticyclone and northwesterly wind corresponding to anticyclonic circulation over the northwest India remarkably contributed to positive rainfall in July over most of the Indian subcontinent. While reduced rainfall over the Indian subcontinent in August 2016 is associated with the anomalous moisture transport from ISM region to WNP region, in contrast to July, due to local cyclogenesis corroborated by number of tropical cyclones in the WNP. In addition to this, subsidence related to strong convection supported by cyclonic circulation over the WNP also resulted in low rainfall over the ISM region. Coupled General Circulation model sensitivity experiments confirmed that strong convective activities associated with cyclonic circulation over the WNP is primarily responsible for the observed negative ISM rainfall anomalies in August 2016. It is noted that the Indo-Western Pacific circulation anomalies in August 2016 are well predicted when the coupled model is initiated with initial conditions from end of July and beginning of August compared to May. This analysis suggests the importance of the WNP circulation in forcing strong sub-seasonal/month to month rainfall variations over India.

Interdecadal Change in SST Anomalies Associated with Winter Rainfall over South China

NASA Astrophysics Data System (ADS)

Liantong, Z.

2012-04-01

The present study investigates the interdecadal change in winter (January-February-March, or "JFM") rainfall over South China and in South China JFM rainfall-sea surface temperature (SST) relationship by using station observations for the period of 1958-2002, the Met Office Hadley Center's SST data for the period of 1900-2008, and the ERA-40 re-analysis for the period of 1958-2002. It is found that the relationship between South China JFM rainfall and SST experienced an obvious interdecadal change around the year 1978. The analyses show that the JFM rainfall anomalies during 1960-1977 and 1978-2002 were closely associated with the South China Sea (SCS) SST and El Niño-Southern Oscillation (ENSO), respectively. Moreover, southwesterly anomalies at 700 hPa dominate over the South China Sea for positive SCS SST anomaly years during 1960-1977, and for El Niño years during 1978-2002, respectively. These wind anomalies, which are associated with the enhancement of the western Pacific subtropical high, transport more moisture into South China, favoring increases in rainfall. KEY WORDS: ENSO; SCS SST; South China winter rainfall, western Pacific subtropical high.

Synoptic weather types associated with critical fire weather

Treesearch

Mark J. Schroeder; Monte Glovinsky; Virgil F. Hendricks; Frank C. Hood; Melvin K. Hull; Henry L. Jacobson; Robert Kirkpatrick; Daniel W. Krueger; Lester P. Mallory; Albert G. Oeztel; Robert H. Reese; Leo A. Sergius; Charles E. Syverson

1964-01-01

Recognizing that weather is an important factor in the spread of both urban and wildland fires, a study was made of the synoptic weather patterns and types which produce strong winds, low relative humidities, high temperatures, and lack of rainfall--the conditions conducive to rapid fire spread. Such historic fires as the San Francisco fire of 1906, the Berkeley fire...

Socioeconomic impacts of climate change on rural communities in the United States

Treesearch

Pankaj Lal; Janaki Alavalapati; D Evan Mercer

2011-01-01

Climate change refers to any distinct change in measures of climate such as temperature, rainfall, snow, or wind patterns lasting for decades or longer (USEPA 2009). In the last decade, there has been a clear consensus among scientists that the world is experiencing a rapid global climate change, much of it attributable to anthropogenic activities. The extent of...

Seasonal Evolution and Variability Associated with the West African Monsoon System

NASA Technical Reports Server (NTRS)

Gu, Guojun; Adler, Robert F.

2003-01-01

In this study, we investigate the seasonal variations in surface rainfall and associated large-scale processes in the tropical eastern Atlantic and West African region. The 5-yr (1998-2002) high-quality TRMM rainfall, sea surface temperature (SST), water vapor and cloud liquid water observations are applied along with the NCEP/NCAR reanalysis wind components and a 3-yr (2000-2002) Quickscat satellite-observed surface wind product. Major mean rainfall over West Africa tends to be concentrated in two regions and is observed in two different seasons, manifesting an abrupt shift of the mean rainfall zone during June-July. (i) Near the Gulf of Guinea (about 5 degN), intense convection and rainfall are seen during April-June and roughly follow the seasonality of SST in the tropical eastern Atlantic. (ii) Along the latitudes of about 10 deg. N over the interior West African continent, a second intense rain belt begins to develop from July and remains there during the later summer season. This belt co-exists with a northwardmoved African Easterly Jet (AEJ) and its accompanying horizonal and vertical shear zones, the appearance and intensification of an upper tropospheric Tropical Easterly Jet (TEJ), and a strong low-level westerly flow. Westward-propagating wave signals [ i e . , African easterly waves (AEWs)] dominate the synoptic-scale variability during July-September, in contrast to the evident eastward-propagating wave signals during May- June. The abrupt shift of mean rainfall zone thus turns out to be a combination of two different physical processes: (i) Evident seasonal cycles in the tropical eastern Atlantic ocean which modulate convection and rainfall in the Gulf of Guinea by means of SST thermal forcing and SST-related meridional gradient; (ii) The interaction among the AEJ, TEJ, low-level westerly flow, moist convection and AEWs during July-September which modulates rainfall variability in the interior West Africa, primarily within the ITCZ rain band. Evident seasonality in synoptic-scale wave signals is shown to be a good evidence for this seasonal evolution.

Best convective parameterization scheme within RegCM4 to downscale CMIP5 multi-model data for the CORDEX-MENA/Arab domain

NASA Astrophysics Data System (ADS)

Almazroui, Mansour; Islam, Md. Nazrul; Al-Khalaf, A. K.; Saeed, Fahad

2016-05-01

A suitable convective parameterization scheme within Regional Climate Model version 4.3.4 (RegCM4) developed by the Abdus Salam International Centre for Theoretical Physics, Trieste, Italy, is investigated through 12 sensitivity runs for the period 2000-2010. RegCM4 is driven with European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim 6-hourly boundary condition fields for the CORDEX-MENA/Arab domain. Besides ERA-Interim lateral boundary conditions data, the Climatic Research Unit (CRU) data is also used to assess the performance of RegCM4. Different statistical measures are taken into consideration in assessing model performance for 11 sub-domains throughout the analysis domain, out of which 7 (4) sub-domains give drier (wetter) conditions for the area of interest. There is no common best option for the simulation of both rainfall and temperature (with lowest bias); however, one option each for temperature and rainfall has been found to be superior among the 12 options investigated in this study. These best options for the two variables vary from region to region as well. Overall, RegCM4 simulates large pressure and water vapor values along with lower wind speeds compared to the driving fields, which are the key sources of bias in simulating rainfall and temperature. Based on the climatic characteristics of most of the Arab countries located within the study domain, the drier sub-domains are given priority in the selection of a suitable convective scheme, albeit with a compromise for both rainfall and temperature simulations. The most suitable option Grell over Land and Emanuel over Ocean in wet (GLEO wet) delivers a rainfall wet bias of 2.96 % and a temperature cold bias of 0.26 °C, compared to CRU data. An ensemble derived from all 12 runs provides unsatisfactory results for rainfall (28.92 %) and temperature (-0.54 °C) bias in the drier region because some options highly overestimate rainfall (reaching up to 200 %) and underestimate temperature (reaching up to -1.16 °C). Overall, a suitable option (GLEO wet) is recommended for downscaling the Coupled Model Intercomparison Project Phase 5 (CMIP5) multi-model database using RegCM4 for the CORDEX-MENA/Arab domain for its use in future climate change impact studies.

Energy budgets and a climate space diagram for the turtle, Chrysemys scripta

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

Foley, R. E.

1976-01-01

Heat energy budgets were computed and a steady state climate space was generated for a 1000 g red-eared turtle (Chrysemys scripta). Evaporative water loss (EWL) was measured from C. scripta at three wind speeds (10-400 cm sec/sup -1/) and at four air temperatures (5 to 35/sup 0/C) in a wind tunnel. EWL increased as air temperature and wind speed increased. Smaller turtles dehydrated at a faster rate than large turtles. Heat transfer by convection was measured from aluminum castings of C. scripta at three temperature differences between casting and air (..delta..T 15/sup 0/, 10/sup 0/ and 5/sup 0/C) for threemore » windspeeds (10 to 400 cm sec/sup -1/). Convective heat transfer coefficients increased as wind speed and ..delta..T increased. Wind speed has a large effect on the shape of the climate space. At high wind speeds, heat loss by evaporation and convection are greatly increased. In still air (10 cm sec/sup -1/), a turtle cannot remain exposed to full sunlight when air temperatures exceed 19/sup 0/C. When wind speed increases to 400 cm sec/sup -1/, the turtle can bask for long periods of time at temperatures as high as 32/sup 0/C. Basking patterns of C. scripta probably shift from a unimodal pattern in the spring to a bimodal pattern in summer and return to a unimodal pattern in fall. Terrestrial activity may be extensive in the spring and fall but is limited during the hot summer months to periods of rainfall. Nesting activities cannot occur around solar noon because increased metabolic heat loading and high solar radiation intensity could cause death.« less

Influence of Environmental Factors and Human Activity on the Presence of Salmonella Serovars in a Marine Environment

PubMed Central

Martinez-Urtaza, Jaime; Saco, Montserrat; de Novoa, Jacobo; Perez-Piñeiro, Pelayo; Peiteado, Jesus; Lozano-Leon, Antonio; Garcia-Martin, Oscar

2004-01-01

The temporal and spatial distribution of Salmonella contamination in the coastal waters of Galicia (northwestern Spain) relative to contamination events with different environmental factors (temperature, wind, hours of sunlight, rainfall, and river flow) were investigated over a 4-year period. Salmonellae were isolated from 127 of 5,384 samples of molluscs and seawater (2.4%), and no significant differences (P < 0.05) between isolates obtained in different years were observed. The incidence of salmonellae was significantly higher in water column samples (2.9%) than in those taken from the marine benthos (0.7%). Of the 127 strains of Salmonella isolated, 20 different serovars were identified. Salmonella enterica serovar Senftenberg was the predominant serovar, being represented by 54 isolates (42.5%), followed by serovar Typhimurium (19 isolates [15%]) and serovar Agona (12 isolates [9.4%]). Serovar Senftenberg was detected at specific points on the coast and could not be related to any of the environmental parameters analyzed. All serovars except Salmonella serovar Senftenberg were found principally in the southern coastal areas close to the mouths of rivers, and their incidence was associated with high southwestern wind and rainfall. Using multiple logistic regression analysis models, the prevalence of salmonellae was best explained by environmental parameters on the day prior to sampling. Understanding this relationship may be useful for the control of molluscan shellfish harvests, with wind and rainfall serving as triggers for closure. PMID:15066800

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.

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.

Pollution characteristics and influencing factors of atmospheric particulate matter (PM2.5) in Chang-Zhu-Tan area

NASA Astrophysics Data System (ADS)

Zhang, Yong; Jiang, Wulin

2018-01-01

Using the same time data of PM2.5 concentration and meteorology from May 1st to May 31st in 2013 in Chang-Zhu-Tan area. This paper analyses the variation characteristics of PM2.5 concentration and the correlations between the variation characteristics and meteorological factors. In view of time, the results showed that the 24-h PM2.5 concentration varied with the two peaks and two valleys styles in Chang-Zhu-Tan area. And the daily PM2.5 concentration tends to the instability and great variation characteristics with the multi-peaks and multi-valleys style. In view of space, PM2.5 concentration values of the three cities from high to low are Zhuzhou>Xiangtan>Changsha. For cities and suburbs, PM2.5 concentration values of central towns are greater than that of the suburbs in Changsha and Xiangtan; however, the PM2.5 concentration values of the central town in Zhuzhou are slightly lower than the suburbs. At the same time, the correlation analysis between PM2.5 concentration and meteorological factors showed that the correlation from high to low was the relative air humidity>soil temperature>air temperature>soil humidity> wind velocity>rainfall. Among the above meteorological factors, wind velocity, rainfall, air temperature, soil temperature and soil humidity are negatively correlated with PM2.5 concentration, but the relationship between relative air humidity and PM2.5 concentration is a positive correlation.

Summer Leeside Rainfall Maxima over the Island of Hawaii

NASA Astrophysics Data System (ADS)

Huang, Y. F.; Chen, Y. L.

2016-12-01

The Kona area on the leeside in the island of Hawaii has distinctive summer rainfall maxima. The primary physical processes for the summer rainfall maxima in Kona are analyzed by comparing it with the winter rainfall. The annual and diurnal cycles there are investigated by employing the Fifth-generation Pennsylvania State University-NCAR Mesoscale Model coupled with the advanced land surface model from June 2004 and February 2010. During the summer, the nocturnal rainfall maximum adjacent to the Kona coast is larger than in winter because of the stronger, moister westerly reversed flow and offshore flow in summer. Comparisons between winter trade-wind days and winter mean show that the leeside Kona rainfall offshore in winter mainly occurs under trade-wind conditions. Moreover, the model results also attest to the impact of moisture content on the Kona leeside rainfall offshore. Comparisons between winter and summer trade-wind days indicate that upslope flows on the Kona slopes are stronger and the moisture content from the westerly reversed flow is higher in summer than in winter. The rainfall maximum on the lower Kona slopes is more pronounced in summer than in winter as a result of enhanced orographic lifting due to stronger upslope flow in the afternoon hours and the moister westerly reversed flow offshore, which merges with the upslope flow inland.

Global warming induced hybrid rainy seasons in the Sahel

NASA Astrophysics Data System (ADS)

Salack, Seyni; Klein, Cornelia; Giannini, Alessandra; Sarr, Benoit; Worou, Omonlola N.; Belko, Nouhoun; Bliefernicht, Jan; Kunstman, Harald

2016-10-01

The small rainfall recovery observed over the Sahel, concomitant with a regional climate warming, conceals some drought features that exacerbate food security. The new rainfall features include false start and early cessation of rainy seasons, increased frequency of intense daily rainfall, increasing number of hot nights and warm days and a decreasing trend in diurnal temperature range. Here, we explain these mixed dry/wet seasonal rainfall features which are called hybrid rainy seasons by delving into observed data consensus on the reduction in rainfall amount, its spatial coverage, timing and erratic distribution of events, and other atmospheric variables crucial in agro-climatic monitoring and seasonal forecasting. Further composite investigations of seasonal droughts, oceans warming and the regional atmospheric circulation nexus reveal that the low-to-mid-level atmospheric winds pattern, often stationary relative to either strong or neutral El-Niño-Southern-Oscillations drought patterns, associates to basin warmings in the North Atlantic and the Mediterranean Sea to trigger hybrid rainy seasons in the Sahel. More challenging to rain-fed farming systems, our results suggest that these new rainfall conditions will most likely be sustained by global warming, reshaping thereby our understanding of food insecurity in this region.

A distinction between summer rainy season and summer monsoon season over the Central Highlands of Vietnam

NASA Astrophysics Data System (ADS)

Ngo-Thanh, Huong; Ngo-Duc, Thanh; Nguyen-Hong, Hanh; Baker, Peter; Phan-Van, Tan

2018-05-01

The daily rainfall data at 13 stations over the Central Highlands (CH) Vietnam were collected for the period 1981-2014. Two different sets of criteria using daily observed rainfall and 850 hPa daily reanalysis wind data were applied to determine the onset (retreat) dates of the summer rainy season (RS) and summer monsoon (SM) season, respectively. Over the study period, the mean RS and SM onset dates were April 20 and May 13 with standard deviations of 17.4 and 17.8 days, respectively. The mean RS and SM retreat dates were November 1 and September 30 with standard deviations of 17.9 and 10.2 days, respectively . The year-to-year variations of the onset dates and the rainfall amount within the RS and SM season were closely linked with the preceding winter and spring sea surface temperature in the central-eastern and western Pacific. It was also found that the onset dates were significantly correlated with the RS and SM rainfall amount.

Evaluating weather factors and material response during outdoor exposure to determine accelerated test protocols for predicting service life

Treesearch

R. Sam Williams; Steven Lacher; Corey Halpin; Christopher White

2005-01-01

To develop service life prediction methods for the study of sealants, a fully instrumented weather station was installed at an outdoor test site near Madison, WI. Temperature, relative humidiy, rainfall, ultraviolet (UV) radiation at 18 wavelengths, and wind speed and direction are being continuously measured and stored. The weather data can be integrated over time to...

NFLUX PRE: Validation of New Specific Humidity, Surface Air Temperature, and Wind Speed Algorithms for Ascending/Descending Directions and Clear or Cloudy Conditions

DTIC Science & Technology

2015-06-18

providing all three surface state variables: TA, QA, and U10. It flies as part of the “A-Train” afternoon constellation (see http://atrain.nasa.gov...Chao (2006). Rainfall Estimation of Mesoscale Convective Systems using AMSU-A data during the Mei-Yu Season . Terr. Atmos. Ocean. Sci., 17, 91-109

Mixing to Monsoons: Air-Sea Interactions in the Bay of Bengal

NASA Astrophysics Data System (ADS)

Lucas, A. J.; Shroyer, E. L.; Wijesekera, H. W.; Fernando, H. J. S.; D'Asaro, E.; Ravichandran, M.; Jinadasa, S. U. P.; MacKinnon, J. A.; Nash, J. D.; Sharma, R.; Centurioni, L.; Farrar, J. T.; Weller, R.; Pinkel, R.; Mahadevan, A.; Sengupta, D.; Tandon, A.

2014-07-01

More than 1 billion people depend on rainfall from the South Asian monsoon for their livelihoods. Summertime monsoonal precipitation is highly variable on intraseasonal time scales, with alternating "active" and "break" periods. These intraseasonal oscillations in large-scale atmospheric convection and winds are closely tied to 1°C-2°C variations of sea surface temperature in the Bay of Bengal.

On the asymmetric distribution of shear-relative typhoon rainfall

NASA Astrophysics Data System (ADS)

Gao, Si; Zhai, Shunan; Li, Tim; Chen, Zhifan

2018-02-01

The Tropical Rainfall Measuring Mission (TRMM) 3B42 precipitation, the National Centers for Environmental Prediction (NCEP) Final analysis and the Regional Specialized Meteorological Center (RSMC) Tokyo best-track data during 2000-2015 are used to compare spatial rainfall distribution associated with Northwest Pacific tropical cyclones (TCs) with different vertical wind shear directions and investigate possible mechanisms. Results show that the maximum TC rainfall are all located in the downshear left quadrant regardless of shear direction, and TCs with easterly shear have greater magnitudes of rainfall than those with westerly shear, consistent with previous studies. Rainfall amount of a TC is related to its relative position and proximity from the western Pacific subtropical high (WPSH) and the intensity of water vapor transport, and low-level jet is favorable for water vapor transport. The maximum of vertically integrated moisture flux convergence (MFC) are located on the downshear side regardless of shear direction, and the contribution of wind convergence to the total MFC is far larger than that of moisture advection. The cyclonic displacement of the maximum rainfall relative to the maximum MFC is possibly due to advection of hydrometeors by low- and middle-level cyclonic circulation of TCs. The relationship between TC rainfall and the WPSH through water vapor transport and vertical wind shear implies that TC rainfall may be highly predictable given the high predictability of the WPSH.

Origins and interrelationship of Intraseasonal rainfall variations around the Maritime Continent during boreal winter

NASA Astrophysics Data System (ADS)

Cao, Xi; Wu, Renguang

2018-04-01

Large intraseasonal rainfall variations are identified over the southern South China Sea (SSCS), tropical southeastern Indian Ocean (SEIO), and east coast of the Philippines (EPHI) in boreal winter. The present study contrasts origins and propagations and investigates interrelations of intraseasonal rainfall variations on the 10-20- and 30-60-day time scales in these regions. Different origins are identified for intraseasonal rainfall anomalies over the SSCS, SEIO, and EPHI on both time scales. On the 10-20-day time scale, strong northerly or northeasterly wind anomalies related to the East Asian winter monsoon (EAWM) play a major role in intraseasonal rainfall variations over the SSCS and EPHI. On the 30-60-day time scale, both the intraseasonal signal from the tropical Indian Ocean and the EAWM-related wind anomalies contribute to intraseasonal rainfall variations over the SSCS, whereas the EAWM-related wind anomalies have a major contribution to the intraseasonal rainfall variations over the EPHI. No relation is detected between the intraseasonal rainfall variations over the SEIO and the EAWM on both the 10-20-day and 30-60-day time scales. The anomalies associated with intraseasonal rainfall variations over the SSCS and EPHI propagate northwestward and northeastward, respectively, on the 10-20- and 30-60-day time scales. The intraseasonal rainfall anomalies display northwestward and northward propagation over the Bay of Bengal, respectively, on the 10-20- and 30-60-day time scales.

Precipitation isotopes link regional climate patterns to water supply in a tropical mountain forest, eastern Puerto Rico

USGS Publications Warehouse

Scholl, Martha A.; Murphy, Sheila F.

2014-01-01

Like many mountainous areas in the tropics, watersheds in the Luquillo Mountains of eastern Puerto Rico have abundant rainfall and stream discharge and provide much of the water supply for the densely populated metropolitan areas nearby. Projected changes in regional temperature and atmospheric dynamics as a result of global warming suggest that water availability will be affected by changes in rainfall patterns. It is essential to understand the relative importance of different weather systems to water supply to determine how changes in rainfall patterns, interacting with geology and vegetation, will affect the water balance. To help determine the links between climate and water availability, stable isotope signatures of precipitation from different weather systems were established to identify those that are most important in maintaining streamflow and groundwater recharge. Precipitation stable isotope values in the Luquillo Mountains had a large range, from fog/cloud water with δ2H, δ18O values as high as +12 ‰, −0.73 ‰ to tropical storm rain with values as low as −127 ‰, −16.8 ‰. Temporal isotope values exhibit a reverse seasonality from those observed in higher latitude continental watersheds, with higher isotopic values in the winter and lower values in the summer. Despite the higher volume of convective and low-pressure system rainfall, stable isotope analyses indicated that under the current rainfall regime, frequent trade -wind orographic showers contribute much of the groundwater recharge and stream base flow. Analysis of rain events using 20 years of 15 -minute resolution data at a mountain station (643 m) showed an increasing trend in rainfall amount, in agreement with increased precipitable water in the atmosphere, but differing from climate model projections of drying in the region. The mean intensity of rain events also showed an increasing trend. The determination of recharge sources from stable isotope tracers indicates that water supply will be affected if regional atmospheric dynamics change trade- wind orographic rainfall patterns in the Caribbean.

The role of mountain precipitation as a drought buffer in Puerto Rico: Assessing natural systems' resilience to change

NASA Astrophysics Data System (ADS)

Scholl, M. A.; Clark, K. E.; Van Beusekom, A.; Shanley, J. B.; Torres-Sanchez, A.; Murphy, S. F.; Gonzalez, G.

2017-12-01

Like many island and coastal areas, the Luquillo Mountains of Puerto Rico receive orographic precipitation (rain and cloud water), maintaining headwater streamflow and allowing diverse forest ecosystems to thrive. Although rainfall from regional-scale convective systems is greater in volume, multiple lines of evidence (stable isotope tracers; precipitation amount, frequency, and intensity; cloud immersion; regional cloud dynamics; weather analysis) show that trade-wind orographic precipitation contributes significantly to streamflow, soil water, and shallow groundwater. Ceilometer data and time-lapse photography of cloud-immersed conditions at the mountain indicated a seasonally invariant, sustained overnight regime of cloud water precipitation, in addition to the abundant rainfall in the mountains. Rising ocean temperatures and a warming tropical climate lead to questions about persistence of the trade-wind associated orographic precipitation and the resilience of similar mountain ecosystems to change. Projections for Caribbean climate change include amplification of trade winds; less frequent, more intense large convective systems; and a warming ocean. These may have opposing effects on mountain precipitation, increasing uncertainty about processes that mitigate drought. Field studies provide insights regarding these questions. Ceilometer and satellite observations showed cloud base is higher over the mountains than in the surrounding Caribbean region; with the trade-wind inversion cap, further rise in cloud base may produce shallower clouds and reduced precipitation. We analyzed the February-October 2015 drought, characterized by strong El Niño conditions, an absence of tropical storm systems, and reduced convection in easterly waves. Combined δ2H, δ18O and d-excess signatures of streamflow indicated precipitation was derived from shallow convective systems, trade-wind showers and cloud water. During severe drought on the island, streamflow-sustaining rainfall at the mountain station at 640 m persisted, albeit with 19% lower frequency and 52% fewer large (>10 mm) rain events than the 20-year average. Clearly, resilience of the mountain forest ecosystem and of streamflow to drought periods depends on orographic precipitation.

The relevance of wind-driven rain for future soil erosion research

NASA Astrophysics Data System (ADS)

Fister, Wolfgang; Marzen, Miriam; Iserloh, Thomas; Seeger, Manuel; Heckrath, Goswin; Greenwood, Philip; Kuhn, Nikolaus J.; Ries, Johannes B.

2014-05-01

The influence of wind on falling raindrops and its potential to alter soil erosion rates was already proposed during the 1960s, but never really reached broad awareness in the soil erosion research community. Laboratory investigations over the last 15 years confirmed earlier findings and have proven that wind modifies the characteristics of falling raindrops in many ways. Most importantly, the impact angles and impact frequencies, as well as the drop velocities, drop sizes and hence the kinetic energy are modified. Consequently, the results of laboratory experiments on highly disturbed, loose, and mostly sandy substrates indicate that soil detachment and transport/splash distances of particles increase under the influence of wind. However, these experiments cannot reflect the complexity of naturally developed soils and a direct transfer of these findings to field conditions is therefore limited. So far, only a few field studies have reported increased erosion rates due to splash drift or increased runoff by wind-driven rain. Because of the lack of simultaneous reference measurements without the influence of wind, these studies were not able to discriminate between the different processes and thus couldn not clearly prove the relevance of wind-driven rainfall. Despite all these findings, the awareness of this phenomenon is, in our opinion, still limited. Almost all rainfall simulations exclude the factor of wind as a disturbance to reach more representative rainfall conditions on the plot. We think, that among other reasons, this underestimation of the influence of wind could be due to the absence of an adequate measurement device to simulate these processes and additionally, due to the fact that the relevance of wind-driven rain in a landscape context has not yet been proven. To overcome this lack of a useful device, and to take the research from the laboratory to the field on real soils again, the first portable wind and rainfall simulator was developed within this PhD-project. By measuring soil erosion rates on the same plot, both with and without wind application, the influence of wind on soil detachment and erosion rates can now clearly be determined. Field experiments with the Portable Wind and Rainfall Simulator, which were carried out in Andalusia (Spain), in Wageningen (The Netherlands), and in Foulum (Denmark) during and within 3 years after finishing the PhD-project, aimed to improve the knowledge of processes involved, and to show the relevance of wind-driven rainfall erosion. The results indicate that the influence of wind depends on the complexity of the landscape. In an environment with homogenous conditions (loose sand mixture) and only a few variable factors (i.e. no vegetation, no surface roughness, no slope), like the test site in Wageningen, the increase of erosion rates due to the influence of wind could be seen in almost every test run. This clear influence of wind decreased with the amount of involved factors from agricultural soils in Denmark with a homogenous sandy texture and steep slopes, to highly degraded abandoned/fallow land with thick soil crusts and a clay-silt texture in Andalusia. The results obtained by "simple" rainfall simulations, therefore, clearly underestimate soil erosion rates, depending on the environment. This could, in our opinion, have strong implications for future soil erosion research and modelling.

Using nudging to improve global-regional dynamic consistency in limited-area climate modeling: What should we nudge?

NASA Astrophysics Data System (ADS)

Omrani, Hiba; Drobinski, Philippe; Dubos, Thomas

2015-03-01

Regional climate modelling sometimes requires that the regional model be nudged towards the large-scale driving data to avoid the development of inconsistencies between them. These inconsistencies are known to produce large surface temperature and rainfall artefacts. Therefore, it is essential to maintain the synoptic circulation within the simulation domain consistent with the synoptic circulation at the domain boundaries. Nudging techniques, initially developed for data assimilation purposes, are increasingly used in regional climate modeling and offer a workaround to this issue. In this context, several questions on the "optimal" use of nudging are still open. In this study we focus on a specific question which is: What variable should we nudge? in order to maintain the consistencies between the regional model and the driving fields as much as possible. For that, a "Big Brother Experiment", where a reference atmospheric state is known, is conducted using the weather research and forecasting (WRF) model over the Euro-Mediterranean region. A set of 22 3-month simulations is performed with different sets of nudged variables and nudging options (no nudging, indiscriminate nudging, spectral nudging) for summer and winter. The results show that nudging clearly improves the model capacity to reproduce the reference fields. However the skill scores depend on the set of variables used to nudge the regional climate simulations. Nudging the tropospheric horizontal wind is by far the key variable to nudge to simulate correctly surface temperature and wind, and rainfall. To a lesser extent, nudging tropospheric temperature also contributes to significantly improve the simulations. Indeed, nudging tropospheric wind or temperature directly impacts the simulation of the tropospheric geopotential height and thus the synoptic scale atmospheric circulation. Nudging moisture improves the precipitation but the impact on the other fields (wind and temperature) is not significant. As an immediate consequence, nudging tropospheric wind, temperature and moisture in WRF gives by far the best results with respect to the Big-Brother simulation. However, we noticed that a residual bias of the geopotential height persists due to a negative surface pressure anomaly which suggests that surface pressure is the missing quantity to nudge. Nudging the geopotential has no discernible effect. Finally, it should be noted that the proposed strategy ensures a dynamical consistency between the driving field and the simulated small-scale field but it does not ensure the best "observed" fine scale field because of the possible impact of incorrect driving large-scale field.

A Geospatial Database for Wind and Solar Energy Applications: The Kingdom of Bahrain Study Case

NASA Astrophysics Data System (ADS)

Al-Joburi, Khalil; Dahman, Nidal

2017-11-01

This research is aimed at designing, implementing, and testing a geospatial database for wind and solar energy applications in the Kingdom of Bahrain. All decision making needed to determine economic feasibility and establish site location for wind turbines or solar panels depends primarily on geospatial feature theme information and non-spatial (attribute) data for wind, solar, rainfall, temperature and weather characteristics of a particular region. Spatial data includes, but is not limited to, digital elevation, slopes, land use, zonings, parks, population density, road utility maps, and other related information. Digital elevations for over 450,000 spot at 50 m spatial horizontal resolution plus field surveying and GPS (at selected locations) was obtained from the Surveying and Land Registration Bureau (SLRB). Road, utilities, and population density are obtained from the Central Information Organization (CIO). Land use zoning, recreational parks, and other data are obtained from the Ministry of Municipalities and Agricultural Affairs. Wind, solar, humidity, rainfall, and temperature data are obtained from the Ministry of Transportation, Civil Aviation Section. LandSat Satellite and others images are obtained from NASA and online sources respectively. The collected geospatial data was geo-referenced to Ain el-Abd UTM Zone 39 North. 3D Digital Elevation Model (DEM)-50 m spatial resolutions was created using SLRB spot elevations. Slope and aspect maps were generate based on the DEM. Supervised image classification to identify open spaces was performed utilizing satellite images. Other geospatial data was converted to raster format with the same cell resolution. Non-spatial data are entered as an attribute to spatial features. To eliminate ambiguous solution, multi-criteria GIS model is developed based on, vector (discrete point, line, and polygon representations) as well as raster model (continuous representation). The model was tested at the Al-Areen proposed project, a relatively small area (15 km2). Optimum site spatial location for the location of wind turbines and solar panels was determined and initial results indicates that the combination of wind and solar energy would be sufficient for the project to meet the energy demand at the present per capita consummation rate..

Indonesian Rainfall Characteristic Based on the EAR and WPR Data Analysis

NASA Astrophysics Data System (ADS)

Hermawan, Eddy

2010-05-01

As one of the most real product of the joint research between RISH (Research Institute for Sustainable Humanosphere) of Kyoto University, Japan with the National Institute of Aeronautics and Space (LAPAN), is being applied the Equatorial Atmosphere Radar (EAR) at Kototabang, Bukittinggi, West Sumatera that has already operated since June, 2001. The other one, since March 2007, has also operated the other radar that called as WPR (Wind Profiling Radar) at Pontianak and Biak station under the JAMSTEC (Japan Marine Science Technology), Japan. Those radars give a good chance for the Indonesian young scientist to apply those data in applicable research for many people. One of them is the behavior of Indonesian rainfall variability over Kototabang, Pontianak, and Biak, respectively. This is very important, since rainfall is one of the most important parameter that has direct effect to daily living, not only in wet season (suspected related to flooding) or dry season (suspected related to drought) than normal condition. We understood that until now, no many significant result obtained from those data, especially from WPR, not only since that data is still new one, but also related well to the limitation of the other suppport data, facility (hardware and software), also the man power (reseracher) working on that data analysis. Based on this condition, the main purpose of this study is to investigate the Indonesian rainfall behavior, especially over Kototabang, Pontianak, and Biak, respectively. The others are we would like to investigate the pattern of zonal wind variation along the Indian Ocean passing away to Indonesia region, to investigate the MJO (Madden Julian Oscillation) phenomenon, and to investigate the relationship or correlation between rainfall and zonal wind variation. The results show that in the wet season (DJF=December-January-February), Kototabang and surrounded area is dominated by the Westerly wind that mostly contains of water vapor. While, in the dry season (JJA=June-July-August), the Easterly wind dominates this area. This condition, is a little bit different with Pontianak that mostly is dominated by the Westerly wind, both in wet and dry season. While, in Biak, the Easterly wind dominates, both in wet and dry season. We found also the zonal wind propagation over those cities, Kototabang, Pontianak, and Biak are about 45 days, 45 days, and 55 days oscillation. Although, we found a small positive correlation between the zonal wind variation with rainfall intensity over those area (below than 0.5), but it is still significant statistically. Keywords : EAR, WPR, HARIMAU, and Rainfall

The Tropical Rainfall Measuring (TRMM) - What Have We Learned and What Does the Future Hold?

NASA Technical Reports Server (NTRS)

Kummerow, C.; Hong, Y.; Olsen, W. S.

2000-01-01

Rainfall is important in the hydrological cycle and to the lives and welfare of humans. In addition to being a life-giving resource, rainfall processes also plays a crucial role in the dynamics of the global atmospheric circulation. Three-fourths of the energy that drives the atmospheric wind circulation comes from the latent heat released by tropical precipitation. It varies greatly in space and time. The rain-producing cloud systems may last several hours or days. Their dimensions range from 10 km to several hundred km. This makes it difficult to incorporate rainfall directly large-scale weather and climate models. Until the end of 1997, precipitation in the global tropics was not known to within a factor of two. Regarding "global warming", the various large-scale models differed among themselves in the predicted magnitude of the warming and in the expected regional effects of these temperature and moisture changes. The Tropical Rainfall Measuring Mission (TRMM) satellite has yielded important interim results related to rainfall observations, data assimilation and model forecast skills when rainfall data is assimilated. This talk will summarize where the TRMM science team is with regards to answering some of these important scientific challenges, as well as discuss the future Global Precipitation Mission which will provide 3 hourly rainfall coverage and offers some unique collaborative potential for NOAA and NASA.

Trends of rainfall regime in Peninsular Malaysia during northeast and southwest monsoons

NASA Astrophysics Data System (ADS)

Chooi Tan, Kok

2018-04-01

The trends of rainfall regime in Peninsular Malaysia is mainly affected by the seasonal monsoon. The aim of this study is to investigate the impact of northeast and southwest monsoons on the monthly rainfall patterns over Badenoch Estate, Kedah. In addition, the synoptic maps of wind vector also being developed to identify the wind pattern over Peninsular Malaysia from 2007 – 2016. On the other hand, the archived daily rainfall data is acquired from Malaysian Meteorological Department. The temporal and trends of the monthly and annual rainfall over the study area have been analysed from 2007 to 2016. Overall, the average annual precipitation over the study area from 2007 to 2016 recorded by rain gauge is 2562.35 mm per year.

Diagnostics of Rainfall Anomalies in the Nordeste During the Global Weather Experiment

NASA Technical Reports Server (NTRS)

Sikdar, D. M.

1984-01-01

The relationship of the daily variability of large-scale pressure, cloudiness and upper level wind patterns over the Brazil-Atlantic sector during March/April 1979 to rainfall anomalies in northern Nordeste was investigated. The experiment divides the rainy season (March/April) of 1979 into wet and dry days, then composites bright cloudiness, sea level pressure, and upper level wind fields with respect to persistent rainfall episodes. Wet and dry anomalies are analyzed along with seasonal mean conditions.

Coherent response of the Indo-African boreal summer monsoon to Pacific SST captured in Ethiopian rain δ18O

NASA Astrophysics Data System (ADS)

Madhavan, M.; Palliyil, L. R.; Ramesh, R.

2017-12-01

Pacific Sea Surface Temperature (SST) plays an important role in the inter-annual to inter-decadal variability of boreal monsoons. We identified a common mode of inter annual variability in the Indian and African boreal summer monsoon (June to September) rainfalls, which is linked to Pacific SSTs, using Empirical Orthogonal Function (EOF) analysis. Temporal coefficients (Principle component: PC1) of the leading mode of variability (EOF-1) is well correlated with the Indian summer monsoon rainfall and Sahel rainfall. About forty year long monthly observations of δ18O (and δD) at Addis Ababa, Ethiopia show a strong association with PC1 (r=0.69 for δ18O and r=0.75 for δD). Analysis of SST, sea level pressure and lower tropospheric winds suggest that 18O depletion in Ethiopian rainfall (and wet phases of PC1) is associated with cooler eastern tropical Pacific and warmer western Pacific and strengthening of Pacific subtropical high in both the hemispheres. Associated changes in the trade winds cause enhanced westerly moisture transport into the Indian subcontinent and northern Africa and cause enhanced rainfall. The intrusion of Atlantic westerly component of moisture transport at Addis Ababa during wet phases of PC1 is clearly recorded in δ18O of rain. We also observe the same common mode of variability (EOF1) of Indo-African boreal summer monsoon rain on decadal time scales. A 100 year long δ18O record of actively growing speleothem from the Mechara cave, Ethiopia, matches very well with the PC1 on the decadal time scale. This highlights the potential of speleothem δ18O and leaf wax δD from Ethiopia to investigate the natural variability and teleconnections of Indo-African boreal monsoon.

Response of Tropical Forests to Intense Climate Variability and Rainfall Anomaly over the Last Decade

NASA Astrophysics Data System (ADS)

Saatchi, S.; Asefi, S.

2012-04-01

During the last decade, strong precipitation anomalies resulted from increased sea surface temperature in the tropical Atlantic, have caused extensive drying trends in rainforests of western Amazonia, exerting water stress, tree mortality, biomass loss, and large-scale fire disturbance. In contrast, there have been no reports on large-scale disturbance in rainforests of west and central Africa, though being exposed to similar intensity of climate variability. Using data from Tropical Rainfall Mapping Mission (TRMM) (1999-2010), and time series of rainfall observations from meteorological stations (1971-2000), we show that both Amazonian and African rainforest experienced strong precipitation anomalies from 2005-2010. We monitored the response of forest to the climate variability by analyzing the canopy water content observed by SeaWinds Ku-band Scatterometer (QSCAT) (1999-2009) and found that more than 70 million ha of forests in western Amazonia experienced a strong water deficit during the dry season of 2005 and a closely corresponding decline in canopy backscatter that persisted until the next major drought in 2010. This decline in backscatter has been attributed to loss of canopy water content and large-scale tree mortality corroborated by ground and airborne observations. However, no strong impacts was observed on tropical forests of Africa, suggesting that the African rainforest may have more resilience to droughts. We tested this hypothesis by examining the seasonal rainfall patterns, maximum water deficit, and the surface temperature variations. Results show that there is a complex pattern of low annual rainfall, moderate seasonality, and lower surface temperature in Central Africa compared to Amazonia, indicating potentially a lower evapotranspiration circumventing strong water deficits

Response of Tropical Forests to Intense Climate Variability and Rainfall Anomaly of Last Decade

NASA Astrophysics Data System (ADS)

Saatchi, S. S.; Asefi Najafabady, S.

2011-12-01

During the last decade, strong precipitation anomalies resulted from increased sea surface temperature in the tropical Atlantic, have caused extensive drying trends in rainforests of western Amazonia, exerting water stress, tree mortality, biomass loss, and large-scale fire disturbance. In contrast, there have been no reports on large-scale disturbance in rainforests of west and central Africa, though being exposed to similar intensity of climate variability. Using data from Tropical Rainfall Mapping Mission (TRMM) (1999-2010), and time series of rainfall observations from meteorological stations (1971-2000), we show that both Amazonian and African rainforest experienced strong precipitation anomalies from 2005-2010. We monitored the response of forest to the climate variability by analyzing the canopy water content observed by SeaWinds Ku-band Scatterometer (QSCAT) (1999-2009) and found that more than 70 million ha of forests in western Amazonia experienced a strong water deficit during the dry season of 2005 and a closely corresponding decline in canopy backscatter that persisted until the next major drought in 2010. This decline in backscatter has been attributed to loss of canopy water content and large-scale tree mortality corroborated by ground and airborne observations. However, no strong impacts was observed on tropical forests of Africa, suggesting that the African rainforest may have more resilience to droughts. We tested this hypothesis by examining the seasonal rainfall patterns, maximum water deficit, and the surface temperature variations. Results show that there is a complex pattern of low annual rainfall, moderate seasonality, and lower surface temperature in Central Africa compared to Amazonia, indicating potentially a lower evapotranspiration circumventing strong water deficits.

Erodibility of waste (Loess) soils from construction sites under water and wind erosional forces.

PubMed

Tanner, Smadar; Katra, Itzhak; Argaman, Eli; Ben-Hur, Meni

2018-03-01

Excess soils from construction sites (waste soils) become a problem when exposed to soil erosion by water or wind. Understanding waste soil erodibility can contribute to its proper reuse for various surface applications. The general objective of the study was to provide a better understanding of the effects of soil properties on erodibility of waste soils excavated from various depths in a semiarid region under rainfall and wind erosive forces. Soil samples excavated from the topsoil (0-0.3m) and subsoil layers (0.3-0.9 and >1m depths) were subjected to simulated rainfall and wind. Under rainfall erosive forces, the subsoils were more erodible than the topsoil, in contrast to the results obtained under wind erosive forces. Exchangeable sodium percentage was the main factor controlling soil erodibility (K i ) under rainfall, and a significant logarithmic regression line was found between these two parameters. In addition, a significant, linear regression was found between K i and slaking values for the studied soil samples, suggesting that the former can be predicted from the latter. Soil erodibility under wind erosion force was controlled mainly by the dry aggregate characteristics (mean weight diameter and aggregate density): their higher values in the subsoil layers resulted in lower soil erodibility compared to the topsoil. Copyright © 2017 Elsevier B.V. All rights reserved.

On the development of summer thunderstorms in the city of São Paulo: Mean meteorological characteristics and pollution effect

NASA Astrophysics Data System (ADS)

Morales Rodriguez, Carlos A.; da Rocha, Rosmeri P.; Bombardi, Rodrigo

2010-05-01

This study investigates how the summer thunderstorms developed over the city of São Paulo and if the pollution might affect its development or characteristics during the austral summer (December-January-February-March, DJFM months). A total of 605 days from December 1999 to March 2004 was separated as 241 thunderstorms days (TDs) and 364 non-thunderstorm days (NTDs). The analyses are performed by using hourly measurements of air temperature ( T), web-bulb temperature ( Tw), surface atmospheric pressure ( P), wind velocity and direction, rainfall and thunder and lightning observations collected at the Meteorological Station of the University of São Paulo in conjunction with aerosol measurements obtained by AERONET (Aerosol Robotic Network), and the NCEP-DOE (National Centers for Environmental Prediction Department of Energy) reanalysis and radiosondes. The wind diurnal cycle shows that for TDs the morning flow is from the northwest rotating to the southeast after 16:00 local time (LT) and it remains from the east until the night. For the NTDs, the wind is well characterized by the sea-breeze circulation that in the morning has the wind blowing from the northeast and in the afternoon from the southeast. The TDs show that the air temperature diurnal cycle presents higher amplitude and the maximum temperature of the day is 3.2 °C higher than in NTDs. Another important factor found is the difference between moisture that is higher during TDs. In terms of precipitation, the TDs represent 40% of total of days analyzed and those days are responsible for more than 60% of the total rain accumulation during the summer, for instance 50% of the TDs had more than 15.5 mm day - 1 while the NTDs had 4 mm day - 1 . Moreover, the rainfall distribution shows that TDs have higher rainfall rate intensities and an afternoon precipitation maximum; while in the NTDs there isn't a defined precipitation diurnal cycle. The wind and temperature fields from NCEP reanalysis concur with the local weather station and radiosonde observations. The NCEP composites show that TDs are controlled by synoptic circulation characterized by a pre-frontal situation, with a baroclinic zone situated at southern part of São Paulo. In terms of pollution, this study employed the AERONET data to obtain the main aerosol characteristics in the atmospheric column for both TDs and NTDs. The particle size distribution and particle volume size distribution have similar concentrations for both TDs and NTDs and present a similar fine and coarse mode mean radius. In respect to the atmospheric loading, the aerosol optical depth (AOD) at different frequencies presented closed mean values for both TDs and NTDs that were statistically significant at 95% level. The spectral dependency of those values in conjunction with the Angstrom parameter reveal the higher concentration of the fine mode particles that are more likely to be hygroscopic and from urban areas. In summary, no significant aerosol effect could be found on the development of summer thunderstorms, suggesting the strong synoptic control by the baroclinic forcing for deep convective development.

A sound budget for the southeastern Bering Sea: measuring wind, rainfall, shipping, and other sources of underwater sound.

PubMed

Nystuen, Jeffrey A; Moore, Sue E; Stabeno, Phyllis J

2010-07-01

Ambient sound in the ocean contains quantifiable information about the marine environment. A passive aquatic listener (PAL) was deployed at a long-term mooring site in the southeastern Bering Sea from 27 April through 28 September 2004. This was a chain mooring with lots of clanking. However, the sampling strategy of the PAL filtered through this noise and allowed the background sound field to be quantified for natural signals. Distinctive signals include the sound from wind, drizzle and rain. These sources dominate the sound budget and their intensity can be used to quantify wind speed and rainfall rate. The wind speed measurement has an accuracy of +/-0.4 m s(-1) when compared to a buoy-mounted anemometer. The rainfall rate measurement is consistent with a land-based measurement in the Aleutian chain at Cold Bay, AK (170 km south of the mooring location). Other identifiable sounds include ships and short transient tones. The PAL was designed to reject transients in the range important for quantification of wind speed and rainfall, but serendipitously recorded peaks in the sound spectrum between 200 Hz and 3 kHz. Some of these tones are consistent with whale calls, but most are apparently associated with mooring self-noise.

Possible influence of Asian polar vertex contraction on rainfall deficits in China in autumn

NASA Astrophysics Data System (ADS)

Zhu, Xian; Wei, Zhigang; Dong, Wenjie; Li, Zhenchao; Zheng, Zhiyuan; Chen, Chen; Chen, Guangyu; Liu, Yajing

2018-06-01

The mechanisms governing variations in autumn precipitation are complicated and influenced by a number factors. This paper analyses the characteristics of autumn precipitation in China and investigates the influence of Asian polar vertex contraction on rainfall deficits in China and relevant mechanisms. Autumn precipitation decreased significantly from 1961 to 2012 in mid- and southern China, and the area of the Asia polar vortex (AAV) has decreased significantly since 1988. Asian polar vertex contraction is found to be an important factor in these autumn rainfall deficits in China through the following mechanism. Asian polar vertex contraction causes anomalously high geopotential heights in East Asia (from 25°N to 55°N) and low heights north of 65°N in the upper and lower troposphere, weakening meridional gradients in geopotential height. In the upper troposphere, the westerly and northerly winds are strengthened over high latitudes and westerly winds and the subtropical westerly jet are weakened over the East Asian mid-latitudes. In the lower troposphere, westerly winds are strengthened over high latitudes, westerly winds are weakened in East Asia and along the southern periphery of the Tibetan Plateau, and northerly winds in mid- and southern China are clearly strengthened. Hence, autumn rainfall decreases in mid- and southern China.

Climate variability and environmental stress in the Sudan-Sahel zone of West Africa.

PubMed

Mertz, Ole; D'haen, Sarah; Maiga, Abdou; Moussa, Ibrahim Bouzou; Barbier, Bruno; Diouf, Awa; Diallo, Drissa; Da, Evariste Dapola; Dabi, Daniel

2012-06-01

Environmental change in the Sudan-Sahel region of West Africa (SSWA) has been much debated since the droughts of the 1970s. In this article we assess climate variability and environmental stress in the region. Households in Senegal, Mali, Burkina Faso, Niger, and Nigeria were asked about climatic changes and their perceptions were compared across north-south and west-east rainfall gradients. More than 80% of all households found that rainfall had decreased, especially in the wettest areas. Increases in wind speeds and temperature were perceived by an overall 60-80% of households. Contrary to household perceptions, observed rainfall patterns showed an increasing trend over the past 20 years. However, August rainfall declined, and could therefore potentially explain the contrasting negative household perceptions of rainfall trends. Most households reported degradation of soils, water resources, vegetation, and fauna, but more so in the 500-900 mm zones. Adaptation measures to counter environmental degradation included use of manure, reforestation, soil and water conservation, and protection of fauna and vegetation. The results raise concerns for future environmental management in the region, especially in the 500-900 mm zones and the western part of SSWA.

Simulation of Tropical Rainfall Variability

NASA Astrophysics Data System (ADS)

Bader, J.; Latif, M.

2002-12-01

The impact of sea surface temperature (SST) - especially the role of the tropical Atlantic meridional SST gradient and the El Nino-Southern Oscillation - on precipitation is investigated with the atmospheric general circulation model ECHAM4/T42. Ensemble experiments - driven with observed SST - show that Atlantic SST has a significant influence on precipitation over West Africa and northeast Brazil. SST sensitivity experiments were performed in which the climatological SST was enhanced or decreased by one Kelvin in certain ocean areas. Changing SST in the eastern tropical Atlantic caused only significant changes along the Guinea Coast, with a positive anomaly (SSTA) increasing rainfall and a negative SSTA reducing it. The response was nearly linear. Changing SST in other ocean areas caused significant changes over West Africa, especially in the Sahel area. The response is found to be non linear, with only negative SSTA leading to significant reduction in Sahel rainfall. Also, the impact of the SSTAs from the different ocean regions was not additive with respect to the rainfall. The influence of SST on precipitation over northeast Brazil (Nordeste) was also investigated. Three experiments were performed in which the climatological SST was enhanced/decreased or decreased/enhanced by one Kelvin in the North/South Atlantic and increased by two Kelvin in the Nino3 ocean area. All experiments caused significant changes over Nordeste, with an enhanced/reduced SST gradient in the Atlantic increasing/reducing rainfall. The response was nearly linear. The main effect of the Atlantic SST gradient was a shift of the ITCZ, caused by trade wind changes. The ''El Nino'' event generates a significant reduction in Nordeste rainfall. A significant positive SLP anomaly occurs in northeast Brazil which may be associated with the descending branch of the Walker circulation. Also a significant positive SLP over the Atlantic from 30S to 10N north occurs. This results in a reduced SLP gradient from the subtropical highs to the equator and a weakening of the trade winds.

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.

Estimation of Rainfall Rates from Passive Microwave Remote Sensing.

NASA Astrophysics Data System (ADS)

Sharma, Awdhesh Kumar

Rainfall rates have been estimated using the passive microwave and visible/infrared remote sensing techniques. Data of September 14, 1978 from the Scanning Multichannel Microwave Radiometer (SMMR) on board SEA SAT-A and the Visible and Infrared Spin Scan Radiometer (VISSR) on board GOES-W (Geostationary Operational Environmental Satellite - West) was obtained and analyzed for rainfall rate retrieval. Microwave brightness temperatures (MBT) are simulated, using the microwave radiative transfer model (MRTM) and atmospheric scattering models. These MBT were computed as a function of rates of rainfall from precipitating clouds which are in a combined phase of ice and water. Microwave extinction due to ice and liquid water are calculated using Mie-theory and Gamma drop size distributions. Microwave absorption due to oxygen and water vapor are based on the schemes given by Rosenkranz, and Barret and Chung. The scattering phase matrix involved in the MRTM is found using Eddington's two stream approximation. The surface effects due to winds and foam are included through the ocean surface emissivity model. Rainfall rates are then inverted from MBT using the optimization technique "Leaps and Bounds" and multiple linear regression leading to a relationship between the rainfall rates and MBT. This relationship has been used to infer the oceanic rainfall rates from SMMR data. The VISSR data has been inverted for the rainfall rates using Griffith's scheme. This scheme provides an independent means of estimating rainfall rates for cross checking SMMR estimates. The inferred rainfall rates from both techniques have been plotted on a world map for comparison. A reasonably good correlation has been obtained between the two estimates.

Rainfall prediction with backpropagation method

NASA Astrophysics Data System (ADS)

Wahyuni, E. G.; Fauzan, L. M. F.; Abriyani, F.; Muchlis, N. F.; Ulfa, M.

2018-03-01

Rainfall is an important factor in many fields, such as aviation and agriculture. Although it has been assisted by technology but the accuracy can not reach 100% and there is still the possibility of error. Though current rainfall prediction information is needed in various fields, such as agriculture and aviation fields. In the field of agriculture, to obtain abundant and quality yields, farmers are very dependent on weather conditions, especially rainfall. Rainfall is one of the factors that affect the safety of aircraft. To overcome the problems above, then it’s required a system that can accurately predict rainfall. In predicting rainfall, artificial neural network modeling is applied in this research. The method used in modeling this artificial neural network is backpropagation method. Backpropagation methods can result in better performance in repetitive exercises. This means that the weight of the ANN interconnection can approach the weight it should be. Another advantage of this method is the ability in the learning process adaptively and multilayer owned on this method there is a process of weight changes so as to minimize error (fault tolerance). Therefore, this method can guarantee good system resilience and consistently work well. The network is designed using 4 input variables, namely air temperature, air humidity, wind speed, and sunshine duration and 3 output variables ie low rainfall, medium rainfall, and high rainfall. Based on the research that has been done, the network can be used properly, as evidenced by the results of the prediction of the system precipitation is the same as the results of manual calculations.

Short-term effects of meteorological factors on hand, foot and mouth disease among children in Shenzhen, China: Non-linearity, threshold and interaction.

PubMed

Zhang, Zhen; Xie, Xu; Chen, Xiliang; Li, Yuan; Lu, Yan; Mei, Shujiang; Liao, Yuxue; Lin, Hualiang

2016-01-01

Various meteorological factors have been associated with hand, foot and mouth disease (HFMD) among children; however, fewer studies have examined the non-linearity and interaction among the meteorological factors. A generalized additive model with a log link allowing Poisson auto-regression and over-dispersion was applied to investigate the short-term effects daily meteorological factors on children HFMD with adjustment of potential confounding factors. We found positive effects of mean temperature and wind speed, the excess relative risk (ERR) was 2.75% (95% CI: 1.98%, 3.53%) for one degree increase in daily mean temperature on lag day 6, and 3.93% (95% CI: 2.16% to 5.73%) for 1m/s increase in wind speed on lag day 3. We found a non-linear effect of relative humidity with thresholds with the low threshold at 45% and high threshold at 85%, within which there was positive effect, the ERR was 1.06% (95% CI: 0.85% to 1.27%) for 1 percent increase in relative humidity on lag day 5. No significant effect was observed for rainfall and sunshine duration. For the interactive effects, we found a weak additive interaction between mean temperature and relative humidity, and slightly antagonistic interaction between mean temperature and wind speed, and between relative humidity and wind speed in the additive models, but the interactions were not statistically significant. This study suggests that mean temperature, relative humidity and wind speed might be risk factors of children HFMD in Shenzhen, and the interaction analysis indicates that these meteorological factors might have played their roles individually. Copyright © 2015 Elsevier B.V. All rights reserved.

Variability of CO2 fugacity at the western edge of the tropical Atlantic Ocean from the 8°N to 38°W PIRATA buoy

NASA Astrophysics Data System (ADS)

Bruto, Leonardo; Araujo, Moacyr; Noriega, Carlos; Veleda, Dóris; Lefèvre, Nathalie

2017-06-01

Hourly data of CO2 fugacity (fCO2) at 8°N-38°W were analyzed from 2008 to 2011. Analyses of wind, rainfall, temperature and salinity data from the buoy indicated two distinct seasonal periods. The first period (January to July) had a mean fCO2 of 378.9 μatm (n = 7512). During this period, in which the study area was characterized by small salinity variations, the fCO2 is mainly controlled by sea surface temperature (SST) variations (fCO2 = 24.4*SST-281.1, r2 = 0.8). During the second period (August-December), the mean fCO2 was 421.9 μatm (n = 11571). During these months, the region is subjected to the simultaneous action of (a) rainfall induced by the presence of the Intertropical Convergence Zone (ITCZ); (b) arrival of fresh water from the Amazon River plume that is transported to the east by the North Equatorial Countercurrent (NECC) after the retroflection of the North Brazil Current (NBC); and (c) vertical input of CO2-rich water due to Ekman pumping. The data indicated the existence of high-frequency fCO2 variability (periods less than 24 h). This high variability is related to two different mechanisms. In the first mechanism, fCO2 increases are associated to rapid increases in SST and are attributed to the diurnal cycle of solar radiation. In addition, low wind speed contributes to SST rising by inhibiting vertical mixing. In the second mechanism, fCO2 decreases are associated to SSS decreases caused by heavy rainfall.

The Influence of Soil Moisture and Wind on Rainfall Distribution and Intensity in Florida

NASA Technical Reports Server (NTRS)

Baker, R. David; Lynn, Barry H.; Boone, Aaron; Tao, Wei-Kuo

1998-01-01

Land surface processes play a key role in water and energy budgets of the hydrological cycle. For example, the distribution of soil moisture will affect sensible and latent heat fluxes, which in turn may dramatically influence the location and intensity of precipitation. However, mean wind conditions also strongly influence the distribution of precipitation. The relative importance of soil moisture and wind on rainfall location and intensity remains uncertain. Here, we examine the influence of soil moisture distribution and wind distribution on precipitation in the Florida peninsula using the 3-D Goddard Cumulus Ensemble (GCE) cloud model Coupled with the Parameterization for Land-Atmosphere-Cloud Exchange (PLACE) land surface model. This study utilizes data collected on 27 July 1991 in central Florida during the Convection and Precipitation Electrification Experiment (CaPE). The idealized numerical experiments consider a block of land (the Florida peninsula) bordered on the east and on the west by ocean. The initial soil moisture distribution is derived from an offline PLACE simulation, and the initial environmental wind profile is determined from the CaPE sounding network. Using the factor separation technique, the precise contribution of soil moisture and wind to rainfall distribution and intensity is determined.

Influence of meteorological variables on rainfall partitioning for deciduous and coniferous tree species in urban area

NASA Astrophysics Data System (ADS)

Zabret, Katarina; Rakovec, Jože; Šraj, Mojca

2018-03-01

Rainfall partitioning is an important part of the ecohydrological cycle, influenced by numerous variables. Rainfall partitioning for pine (Pinus nigra Arnold) and birch (Betula pendula Roth.) trees was measured from January 2014 to June 2017 in an urban area of Ljubljana, Slovenia. 180 events from more than three years of observations were analyzed, focusing on 13 meteorological variables, including the number of raindrops, their diameter, and velocity. Regression tree and boosted regression tree analyses were performed to evaluate the influence of the variables on rainfall interception loss, throughfall, and stemflow in different phenoseasons. The amount of rainfall was recognized as the most influential variable, followed by rainfall intensity and the number of raindrops. Higher rainfall amount, intensity, and the number of drops decreased percentage of rainfall interception loss. Rainfall amount and intensity were the most influential on interception loss by birch and pine trees during the leafed and leafless periods, respectively. Lower wind speed was found to increase throughfall, whereas wind direction had no significant influence. Consideration of drop size spectrum properties proved to be important, since the number of drops, drop diameter, and median volume diameter were often recognized as important influential variables.

Not Out of Control: Analysis of the Federal Disaster Spending Trend

DTIC Science & Technology

2016-03-01

included heavy rain, excessive rainfall, tropical storms, hurricanes, flooding, coastal flooding, wind, straight line winds, high winds, tornadoes ...straight line winds, tornadoes , high winds, coastal flooding, soil saturation, and mud flow.174 Despite the high number of severe storm declarations over

A Northward Shift of the North Atlantic Ocean Intertropical Convergence Zone in Response to Summertime Saharan Dust Outbreaks

NASA Technical Reports Server (NTRS)

Wilcox, Eric M.; Lau, K. M.; Kim, Kyu-Myong

2010-01-01

The influence on the summertime North Atlantic Ocean inter-tropical convergence zone (ITCZ) of Saharan dust outbreaks is explored using nine years of continuous satellite observations and atmospheric reanalysis products. During dust outbreak events rainfall along the ITCZ shifts northward by 1 to 4 degrees latitude. Dust outbreaks coincide with warmer lower-tropospheric temperatures compared to low dust conditions, which is attributable to advection of the warm Saharan Air Layer, enhanced subtropical subsidence, and radiative heating of dust. The enhanced positive meridional temperature gradient coincident with dust outbreaks is accompanied by an acceleration of the easterly winds on the n011h side of the African Easterly Jet (AEJ). The center of the positive vorticity region south of the AEJ moves north drawing the center of low-level convergence and ITCZ rainfall northward with it. The enhanced precipitation on the north side of the ITCZ occurs in spite of widespread sea surface temperature cooling north of the ITCZ owing to reduced surface solar insolation by dust scattering.

Dynamical Downscaling of Climate Change over the Hawaiian Islands

NASA Astrophysics Data System (ADS)

Wang, Y.; Zhang, C.; Hamilton, K. P.; Lauer, A.

2015-12-01

The pseudo-global-warming (PGW) method was applied to the Hawaii Regional Climate Model (HRCM) to dynamically downscale the projected climate in the late 21st century over the Hawaiian Islands. The initial and boundary conditions were adopted from MERRA reanalysis and NOAA SST data for the present-day simulations. The global warming increments constructed from the CMIP3 multi-model ensemble mean were added to the reanalysis and SST data to perform the future climate simulations. We found that the Hawaiian Islands are vulnerable to global warming effects and the changes are diverse due to the varied topography. The windward side will have more clouds and receive more rainfall. The increase of the moisture in the boundary layer makes the major contribution. On the contrary, the leeward side will have less clouds and rainfall. The clouds and rain can slightly slow down the warming trend over the windward side. The temperature increases almost linearly with the terrain height. Cloud base and top heights will slightly decline in response to the slightly lower trade wind inversion base height, while the trade wind occurrence frequency will increase by about 8% in the future. More extreme rainfall events will occur in the warming climate over the Hawaiian Islands. And the snow cover on the top of Mauna Kea and Mauna Loa will nearly disappear in the future winter.

The impact of monsoon intraseasonal variability on renewable power generation in India

NASA Astrophysics Data System (ADS)

Dunning, C. M.; Turner, A. G.; Brayshaw, D. J.

2015-06-01

India is increasingly investing in renewable technology to meet rising energy demands, with hydropower and other renewables comprising one-third of current installed capacity. Installed wind-power is projected to increase 5-fold by 2035 (to nearly 100GW) under the International Energy Agency's New Policies scenario. However, renewable electricity generation is dependent upon the prevailing meteorology, which is strongly influenced by monsoon variability. Prosperity and widespread electrification are increasing the demand for air conditioning, especially during the warm summer. This study uses multi-decadal observations and meteorological reanalysis data to assess the impact of intraseasonal monsoon variability on the balance of electricity supply from wind-power and temperature-related demand in India. Active monsoon phases are characterized by vigorous convection and heavy rainfall over central India. This results in lower temperatures giving lower cooling energy demand, while strong westerly winds yield high wind-power output. In contrast, monsoon breaks are characterized by suppressed precipitation, with higher temperatures and hence greater demand for cooling, and lower wind-power output across much of India. The opposing relationship between wind-power supply and cooling demand during active phases (low demand, high supply) and breaks (high demand, low supply) suggests that monsoon variability will tend to exacerbate fluctuations in the so-called demand-net-wind (i.e., electrical demand that must be supplied from non-wind sources). This study may have important implications for the design of power systems and for investment decisions in conventional schedulable generation facilities (such as coal and gas) that are used to maintain the supply/demand balance. In particular, if it is assumed (as is common) that the generated wind-power operates as a price-taker (i.e., wind farm operators always wish to sell their power, irrespective of price) then investors in conventional facilities will face additional weather-volatility through the monsoonal impact on the length and frequency of production periods (i.e. their load-duration curves).

Climatic factors associated with amyotrophic lateral sclerosis: a spatial analysis from Taiwan.

PubMed

Tsai, Ching-Piao; Tzu-Chi Lee, Charles

2013-11-01

Few studies have assessed the spatial association of amyotrophic lateral sclerosis (ALS) incidence in the world. The aim of this study was to identify the association of climatic factors and ALS incidence in Taiwan. A total of 1,434 subjects with the primary diagnosis of ALS between years 1997 and 2008 were identified in the national health insurance research database. The diagnosis was also verified by the national health insurance programme, which had issued and providing them with "serious disabling disease (SDD) certificates". Local indicators of spatial association were employed to investigate spatial clustering of age-standardised incidence ratios in the townships of the study area. Spatial regression was utilised to reveal any association of annual average climatic factors and ALS incidence for the 12-year study period. The climatic factors included the annual average time of sunlight exposure, average temperature, maximum temperature, minimum temperature, atmospheric pressure, rainfall, relative humidity and wind speed with spatial autocorrelation controlled. Significant correlations were only found for exposure to sunlight and rainfall and it was similar in both genders. The annual average of the former was found to be negatively correlated with ALS, while the latter was positively correlated with ALS incidence. While accepting that ALS is most probably multifactorial, it was concluded that sunlight deprivation and/or rainfall are associated to some degree with ALS incidence in Taiwan.

Accuracy evaluation of ClimGen weather generator and daily to hourly disaggregation methods in tropical conditions

NASA Astrophysics Data System (ADS)

Safeeq, Mohammad; Fares, Ali

2011-12-01

Daily and sub-daily weather data are often required for hydrological and environmental modeling. Various weather generator programs have been used to generate synthetic climate data where observed climate data are limited. In this study, a weather data generator, ClimGen, was evaluated for generating information on daily precipitation, temperature, and wind speed at four tropical watersheds located in Hawai`i, USA. We also evaluated different daily to sub-daily weather data disaggregation methods for precipitation, air temperature, dew point temperature, and wind speed at Mākaha watershed. The hydrologic significance values of the different disaggregation methods were evaluated using Distributed Hydrology Soil Vegetation Model. MuDRain and diurnal method performed well over uniform distribution in disaggregating daily precipitation. However, the diurnal method is more consistent if accurate estimates of hourly precipitation intensities are desired. All of the air temperature disaggregation methods performed reasonably well, but goodness-of-fit statistics were slightly better for sine curve model with 2 h lag. Cosine model performed better than random model in disaggregating daily wind speed. The largest differences in annual water balance were related to wind speed followed by precipitation and dew point temperature. Simulated hourly streamflow, evapotranspiration, and groundwater recharge were less sensitive to the method of disaggregating daily air temperature. ClimGen performed well in generating the minimum and maximum temperature and wind speed. However, for precipitation, it clearly underestimated the number of extreme rainfall events with an intensity of >100 mm/day in all four locations. ClimGen was unable to replicate the distribution of observed precipitation at three locations (Honolulu, Kahului, and Hilo). ClimGen was able to reproduce the distributions of observed minimum temperature at Kahului and wind speed at Kahului and Hilo. Although the weather data generation and disaggregation methods were concentrated in a few Hawaiian watersheds, the results presented can be used to similar mountainous location settings, as well as any specific locations aimed at furthering the site-specific performance evaluation of these tested models.

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.

Assessing weather effects on dengue disease in Malaysia.

PubMed

Cheong, Yoon Ling; Burkart, Katrin; Leitão, Pedro J; Lakes, Tobia

2013-11-26

The number of dengue cases has been increasing on a global level in recent years, and particularly so in Malaysia, yet little is known about the effects of weather for identifying the short-term risk of dengue for the population. The aim of this paper is to estimate the weather effects on dengue disease accounting for non-linear temporal effects in Selangor, Kuala Lumpur and Putrajaya, Malaysia, from 2008 to 2010. We selected the weather parameters with a Poisson generalized additive model, and then assessed the effects of minimum temperature, bi-weekly accumulated rainfall and wind speed on dengue cases using a distributed non-linear lag model while adjusting for trend, day-of-week and week of the year. We found that the relative risk of dengue cases is positively associated with increased minimum temperature at a cumulative percentage change of 11.92% (95% CI: 4.41-32.19), from 25.4 °C to 26.5 °C, with the highest effect delayed by 51 days. Increasing bi-weekly accumulated rainfall had a positively strong effect on dengue cases at a cumulative percentage change of 21.45% (95% CI: 8.96, 51.37), from 215 mm to 302 mm, with the highest effect delayed by 26-28 days. The wind speed is negatively associated with dengue cases. The estimated lagged effects can be adapted in the dengue early warning system to assist in vector control and prevention plan.

[Prevalence of respiratory syncytial virus infection in hospitalized children at a children's hospital and effects of climate change on the prevalence in Suzhou, China].

PubMed

Geng, Jia; Guo, Wan-Liang; Zhang, Xue-Lan

2015-05-01

To investigate the prevalence of respiratory syncytial virus (RSV) infection in hospitalized children and the relationship between the prevalence and the climate change in Suzhou, China. A total of 42 664 nasopharyngeal secretions from hospitalized children with acute respiratory infection at the Suzhou Children's Hospital were screened for RSV antigens using direct immunofluorescence. Monthly meteorological data (mean monthly air temperature, monthly relative humidity, monthly rainfall, total monthly sunshine duration, and mean monthly wind velocity) in Suzhou between 2001 and 2011 were collected. The correlations between RSV detection rate and climatic factors were evaluated using correlation and stepwise regression analysis. The annual RSV infection rate in hospitalized children with respiratory infection in the Suzhou Children's Hospital varied between 11.85% and 27.30% from 2001 to 2011. In the 9 epidemic seasons, each spanning from November to April of the next year, from 2001 to 2010, the RSV detection rates were 40.75%, 22.72%, 39.93%, 27.37%, 42.71%, 21.28%, 38.57%, 19.86%, and 29.73%, respectively; there were significant differences in the detection rate between the epidemic seasons. The monthly RSV detection rate was negatively correlated with mean monthly air temperature, total monthly sunshine duration, monthly rainfall, monthly relative humidity, and mean monthly wind velocity (P<0.05). Stepwise regression analysis showed that mean monthly air temperature fitted into a linear model (R(2)=0.64, P<0.01). From 2001 to 2011, RSV infection in Suzhou was predominantly prevalent between November and April of the next year. As a whole, the infection rate of RSV reached a peak every other year. Air temperature played an important role in the epidemics of RSV infection in Suzhou.

Effects of Atlantic warm pool variability over climate of South America tropical transition zone

NASA Astrophysics Data System (ADS)

Ricaurte Villota, Constanza; Romero-Rodríguez, Deisy; Andrés Ordoñez-Zuñiga, Silvio; Murcia-Riaño, Magnolia; Coca-Domínguez, Oswaldo

2016-04-01

Colombia is located in the northwestern corner of South America in a climatically complex region due to the influence processes modulators of climate both the Pacific and Atlantic region, becoming in a transition zone between phenomena of northern and southern hemisphere. Variations in the climatic conditions of this region, especially rainfall, have been attributed to the influence of the El Nino Southern Oscillation (ENSO), but little is known about the interaction within Atlantic Ocean and specifically Caribbean Sea with the environmental conditions of this region. In this work We studied the influence of the Atlantic Warm Pool (AWP) on the Colombian Caribbean (CC) climate using data of Sea Surface Temperature (SST) between 1900 - 2014 from ERSST V4, compared with in situ data SIMAC (National System for Coral Reef Monitoring in Colombia - INVEMAR), rainfall between 1953-2013 of meteorological stations located at main airports in the Colombian Caribbean zone, administered by IDEAM, and winds data between 2003 - 2014 from WindSat sensor. The parameters analyzed showed spatial differences throughout the study area. SST anomalies, representing the variability of the AWP, showed to be associated with Multidecadal Atlantic Oscillation (AMO) and with the index of sea surface temperature of the North-tropical Atlantic (NTA), the variations was on 3 to 5 years on the ENSO scale and of approximately 11 years possibly related to solar cycles. Rainfall anomalies in the central and northern CC respond to changes in SST, while in the south zone these are not fully engage and show a high relationship with the ENSO. Finally, the winds also respond to changes in SST and showed a signal approximately 90 days possibly related to the Madden-Julian Oscillation, whose intensity depends on the CC region being analyzed. The results confirm that region is a transition zone in which operate several forcing, the variability of climate conditions is difficult to attribute only one, as ENSO, since the role of the AWP in the climate of this region and especially in the central part proves to be decisive, probably due to changes in moisture and heat flows transferred to the atmosphere.

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

Aziz, Mohd Khairul Bazli Mohd, E-mail: mkbazli@yahoo.com; Yusof, Fadhilah, E-mail: fadhilahy@utm.my; Daud, Zalina Mohd, E-mail: zalina@ic.utm.my

Recently, many rainfall network design techniques have been developed, discussed and compared by many researchers. Present day hydrological studies require higher levels of accuracy from collected data. In numerous basins, the rain gauge stations are located without clear scientific understanding. In this study, an attempt is made to redesign rain gauge network for Johor, Malaysia in order to meet the required level of accuracy preset by rainfall data users. The existing network of 84 rain gauges in Johor is optimized and redesigned into a new locations by using rainfall, humidity, solar radiation, temperature and wind speed data collected during themore » monsoon season (November - February) of 1975 until 2008. This study used the combination of geostatistics method (variance-reduction method) and simulated annealing as the algorithm of optimization during the redesigned proses. The result shows that the new rain gauge location provides minimum value of estimated variance. This shows that the combination of geostatistics method (variance-reduction method) and simulated annealing is successful in the development of the new optimum rain gauge system.« less

A preliminary look at the impact of warming Mediterranean Sea temperatures on some aspects of extreme thunderstorm events in Italy

NASA Astrophysics Data System (ADS)

Gallus, William; Parodi, Antonio; Miglietta, Marcello; Maugeri, Maurizio

2017-04-01

As the global climate has warmed in recent decades, interest has grown in the impacts on extreme events associated with thunderstorms such as tornadoes and intense rainfall that can cause flash flooding. Because warmer temperatures allow the atmosphere to contain larger values of water vapor, it is generally accepted that short-term rainfall may become more intense in a future warmer climate. Regarding tornadoes, it is more difficult to say what might happen since although increased temperatures and humidity in the lowest part of the troposphere should increase thermodynamic instability, allowing for stronger thunderstorm updrafts, vertical wind shear necessary for storm-scale rotation may decrease as the pole to equator temperature gradient weakens. The Mediterranean Sea is an important source for moisture that fuels thunderstorms in Italy, and it has been warming faster than most water bodies in recent decades. The present study uses three methods to gain preliminary insight into the role that the warming Mediterranean may have on tornadoes and thunderstorms with intense rainfall in Italy. First, a historical archive of Italian tornadoes has been updated for the 1990s, and it will be used along with other data from the European Severe Weather Database to discuss possible trends in tornado occurrence. Second, convection-allowing Weather Research and Forecasting (WRF) model simulations have been performed for three extreme events to examine sensitivity to both the sea surface temperatures and other model parameters. These events include a flash flood-producing storm event near Milan, a non-tornadic severe hail event in far northeastern Italy, and the Mira EF-4 tornado of July 2015. Sensitivities in rainfall amount, radar reflectivity and storm structure, and storm rotation will be discussed. Finally, changes in the frequency of intense mesoscale convective system events in and near the Ligurian Sea, inferred from the presence of strong convergence lines in EXPRESS-Hydro regional climate model output, will be examined.

The response of land-falling tropical cyclone characteristics to projected climate change in northeast Australia

NASA Astrophysics Data System (ADS)

Parker, Chelsea L.; Bruyère, Cindy L.; Mooney, Priscilla A.; Lynch, Amanda H.

2018-01-01

Land-falling tropical cyclones along the Queensland coastline can result in serious and widespread damage. However, the effects of climate change on cyclone characteristics such as intensity, trajectory, rainfall, and especially translation speed and size are not well-understood. This study explores the relative change in the characteristics of three case studies by comparing the simulated tropical cyclones under current climate conditions with simulations of the same systems under future climate conditions. Simulations are performed with the Weather Research and Forecasting Model and environmental conditions for the future climate are obtained from the Community Earth System Model using a pseudo global warming technique. Results demonstrate a consistent response of increasing intensity through reduced central pressure (by up to 11 hPa), increased wind speeds (by 5-10% on average), and increased rainfall (by up to 27% for average hourly rainfall rates). The responses of other characteristics were variable and governed by either the location and trajectory of the current climate cyclone or the change in the steering flow. The cyclone that traveled furthest poleward encountered a larger climate perturbation, resulting in a larger proportional increase in size, rainfall rate, and wind speeds. The projected monthly average change in the 500 mb winds with climate change governed the alteration in the both the trajectory and translation speed for each case. The simulated changes have serious implications for damage to coastal settlements, infrastructure, and ecosystems through increased wind speeds, storm surge, rainfall, and potentially increased size of some systems.

Trapping of Momentum due to Low Salinity Water in the north Bay of Bengal

NASA Astrophysics Data System (ADS)

Chaudhuri, D.; Tandon, A.; Farrar, T.; Weller, R. A.; Venkatesan, R.; S, S.; MacKinnon, J. A.; D'Asaro, E. A.; Sengupta, D.

2016-02-01

We study the relation between near-surface ocean stratification and upper ocean currents (momentum) during the diurnal cycle and subseasonal "active-break cycle" of the summer monsoon in the north Bay of Bengal. We use time series of hourly observations from NIOT moorings BD08, BD09 and an INCOIS mooring near 18 N, 89 E in 2013, and data collected during two research cruises of ORV Sagar Nidhi in August-September 2014 and 2015. Our analyses are based on upper ocean profiles of temperature, salinity and density (from moorings and a shipborne underway conductivity-temperature-depth profiler), velocity (Acoustic Doppler Current Profiler), and surface forcing (meterology sensors on moored buoy and ship). Monsoon breaks are characterized by low rainfall, low wind speed (0-5 m/s) and high incident shortwave radiation, whereas active phases are marked by intense rainfall, high wind speed (8-16 m/s) and low incident sunlight. Our main findings are: (i) Net surface heat flux is positive (ocean gains heat) during break spells, and sea surface temperature (SST) rises by upto 1.5 C in 1-2 weeks. (ii) During breaks, day-night SST difference can reach 1.5C; mixed layer depth (MLD) shoals to 5m during day time, and deepens to 15-20 m by late night/early morning. (iii) During active spells, SST cools on subseasonal scales; MLD is deep (exceeding 20 m), and diurnal re-stratification is weak or absent. (iv) Once very low-salinity water (<30 psu) from rivers arrives at the moorings in late August, MLD remains shallow, and is insensitive to subseasonal changes in surface forcing. (v) Moored data and high-resolution observations from the summer 2014 and 2015 cruises reveal trapping of momentum from winds in a relatively thin surface layer when surface salinity is low and the shallow stratification is strong. Results of ingoing analyses will be presented at the meeting.

Modelling the fate of the Tijuana River discharge plume

NASA Astrophysics Data System (ADS)

van Ormondt, M.; Terrill, E.; Hibler, L. F.; van Dongeren, A. R.

2010-12-01

After rainfall events, the Tijuana River discharges excess runoff into the ocean in a highly turbid plume. The runoff waters contain large suspended solids concentrations, as well as high levels of toxic contaminants, bacteria, and hepatitis and enteroviruses. Public health hazards posed by the effluent often result in beach closures for several kilometers northward along the U.S. shoreline. A Delft3D model has been set up to predict the fate of the Tijuana River plume. The model takes into account the effects of tides, wind, waves, salinity, and temperature stratification. Heat exchange with the atmosphere is also included. The model consists of a relatively coarse outer domain and a high-resolution surf zone domain that are coupled with Domain Decomposition. The offshore boundary conditions are obtained from the larger NCOM SoCal model (operated by the US Navy) that spans the entire Southern California Bight. A number of discharge events are investigated, in which model results are validated against a wide range of field measurements in the San Diego Bight. These include HF Radar surface currents, REMUS tracks, drifter deployments, satellite imagery, as well as current and temperature profile measurements at a number of locations. The model is able to reproduce the observed current and temperature patterns reasonably well. Under calm conditions, the model results suggest that the hydrodynamics in the San Diego Bight are largely governed by internal waves. During rainfall events, which are typically accompanied by strong winds and high waves, wind and wave driven currents become dominant. An analysis will be made of what conditions determine the trapping and mixing of the plume inside the surfzone and/or the propagation of the plume through the breakers and onto the coastal shelf. The model is now also running in operational mode. Three day forecasts are made every 24 hours. This study was funded by the Office of Naval Research.

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.

Influences of the Agulhas Current on South African terrestrial climate as inferred from speleothem stable isotope records

NASA Astrophysics Data System (ADS)

Braun, K.; Bar-Matthews, M.; Ayalon, A.; Marean, C.; Herries, A. I. R.; Zahn, R.; Matthews, A.

2012-04-01

South African (SA) climate is strongly influenced by the circulation systems surrounding the subcontinent. The warm tropical Agulhas Current provides large amounts of moisture, transported onshore by south-easterly trade winds during summer. As the trade wind shifts north during winter, the south-western tip of SA is especially affected by temperate westerlies. High amounts of rainfall from the Benguela region off the west coast then only affect the very south-west of the country. This seasonal pattern creates a highly variable terrestrial climate, characterized by strong E-W gradients in the seasonal distribution and amount of rainfall. As summer and winter rain is derived from sources with different properties (density, salinity, temperature), the rainfall also displays seasonal isotopic compositional variations, as for example the present mean δ18O of rainfall in Mossel Bay located in the transition region varies from ~0.13‰ in January to -6.05‰ in July. Vegetation type (C3 vs C4) also follows the rainfall regime with C4 vegetation dominating in the summer rainfall region. As part of the GATEWAYS project, speleothems are used as an excellent, high resolution, precisely dated archive of terrestrial paleoenvironmental conditions[1]. This study focuses on a speleothem record from Crevice Cave on the South African south coast (near Mossel Bay), covering the interval between ~111 and ~53 ka[1,2]. At present, the area is influenced by both summer and winter rainfall, and has mostly C3 type vegetation. Variations in the past show more positive δ18O and δ13C values in the interval corresponding to the glacial MIS 4 and indicate increased summer rainfall and C4 vegetation. This contradicts the common assumption that MIS 4 was characterized by a northward shift of the climatic belts over SA and an increase of winter rainfall and C3 vegetation in the cave area[3]. Comparison of the record to marine sediment cores from the Agulhas Retroflection area[4] and the Cape Basin[5,6] as well as an ice-core record from Antarctica[7] reveal that the speleothem δ18O and δ13C are more closely related to the sea surface temperature shifts in the Agulhas region and Antarctica (with lower δ18O and δ13C values corresponding to higher temperatures) than to the influence of global ice-volume related changes in the isotopic composition of the ocean. A contemporary record from a cave site situated ~92 km inland from Mossel Bay (E-Flux Cave, Klein Karoo) shows a very different signal, corresponding to overall changes in Obliquity[8]. The influence of the Agulhas Current is thus apparent on the coast, but reduced inland. [1] Bar-Matthews, M. et al. 2010. Quaternary Science Reviews 29 p2131. [2] Braun, K. et al. 2011. Conference Abstract, Climate Change - The Karst Record 6. Birmingham England p27. [3] Chase, B. M. & Meadows, M. E., 2007. Earth-Science Reviews 84 p103. [4] Cortese, G. et al. 2004. Earth and Planetary Science Letters 222 p767. [5] Martínez-Méndez, G. et al. (2010). Paleoceanography 25(PA4227): doi:10.1029/2009PA001879. [6] Peeters, F. J. C. et al. 2004. Nature 430 p661. [7] Petit, J. R. et al. 1999. Nature 399 p429. [8] Berger, A. L. 1978. Quaternary Research 9 p139.

Potential of collocated radiometer and wind profiler observations for monsoon studies

NASA Astrophysics Data System (ADS)

Balaji, B.; Prabha, Thara V.; Jaya Rao, Y.; Kiran, T.; Dinesh, G.; Chakravarty, Kaustav; Sonbawne, S. M.; Rajeevan, M.

2017-09-01

Collocated observations from microwave radiometer and wind profiler are used in a pilot study during the monsoon period to derive information on the thermodynamics and winds and association with rainfall characteristics. These instruments were operated throughout the monsoon season of 2015. Continuous vertical profiles of winds, temperature and humidity show significant promise for understanding the low-level jet, its periodicity and its association with moisture transport, clouds and precipitation embedded within the monsoon large-scale convection. Observations showed mutually beneficial in explaining variability that are part of the low frequency oscillations and the diurnal variability during monsoon. These observations highlight the importance of locally driven convective systems, in the presence of weak moisture transport over the area. The episodic moisture convergence showed a periodicity of 9 days which matches with the subsequent convection and precipitation and thermodynamic regimes. Inferences from the diurnal cycle of moisture transport and the convective activity, relationship with the low-level jet characteristics and thermodynamics are also illustrated.

Will surface winds weaken in response to global warming?

NASA Astrophysics Data System (ADS)

Ma, Jian; Foltz, Gregory R.; Soden, Brian J.; Huang, Gang; He, Jie; Dong, Changming

2016-12-01

The surface Walker and tropical tropospheric circulations have been inferred to slow down from historical observations and model projections, yet analysis of large-scale surface wind predictions is lacking. Satellite measurements of surface wind speed indicate strengthening trends averaged over the global and tropical oceans that are supported by precipitation and evaporation changes. Here we use corrected anemometer-based observations to show that the surface wind speed has not decreased in the averaged tropical oceans, despite its reduction in the region of the Walker circulation. Historical simulations and future projections for climate change also suggest a near-zero wind speed trend averaged in space, regardless of the Walker cell change. In the tropics, the sea surface temperature pattern effect acts against the large-scale circulation slow-down. For higher latitudes, the surface winds shift poleward along with the eddy-driven mid-latitude westerlies, resulting in a very small contribution to the global change in surface wind speed. Despite its importance for surface wind speed change, the influence of the SST pattern change on global-mean rainfall is insignificant since it cannot substantially alter the global energy balance. As a result, the precipitation response to global warming remains ‘muted’ relative to atmospheric moisture increase. Our results therefore show consistency between projections and observations of surface winds and precipitation.

Effects of Weather, Time, and Pollution Level on the Amount of Particulate Matter Deposited on Leaves of Ligustrum lucidum

PubMed Central

Wang, Huixia; Shi, Hui; Wang, Yanhui

2015-01-01

This paper investigated the spatial and temporal variations in the amounts of PM accumulated on leaves of Ligustrum lucidum, a common evergreen tree species in North China. The effects of rainfall and wind on the amounts of PM deposited on foliage were also determined. The amounts of PM (g·m−2) retained by leaves of L. lucidum differed significantly among the sites (from 0.96 to 5.56) and over time (from 2.51 to 4.48). The largest amounts of PM on foliage of L. lucidum were observed on plants growing at the most polluted site. During the year, the highest and lowest accumulation of PM occurred in November and August, respectively. A considerable proportion of the accumulated PM on leaves was removed by rainfall events (28–48% of PM) and strong winds (27–36% of PM), and more precipitation or higher maximum wind speed could remove more PM from leaves. Rainfall removed mainly large and coarse particles, while fine particles adhered more strongly to the foliage. These results suggested that the effects of local weather conditions (e.g., rainfall, strong wind), different seasons, and pollution levels should be considered in evaluating total PM accumulation on leaves. PMID:25685849

Effects of weather, time, and pollution level on the amount of particulate matter deposited on leaves of Ligustrum lucidum.

PubMed

Wang, Huixia; Shi, Hui; Wang, Yanhui

2015-01-01

This paper investigated the spatial and temporal variations in the amounts of PM accumulated on leaves of Ligustrum lucidum, a common evergreen tree species in North China. The effects of rainfall and wind on the amounts of PM deposited on foliage were also determined. The amounts of PM (g · m(-2)) retained by leaves of L. lucidum differed significantly among the sites (from 0.96 to 5.56) and over time (from 2.51 to 4.48). The largest amounts of PM on foliage of L. lucidum were observed on plants growing at the most polluted site. During the year, the highest and lowest accumulation of PM occurred in November and August, respectively. A considerable proportion of the accumulated PM on leaves was removed by rainfall events (28-48% of PM) and strong winds (27-36% of PM), and more precipitation or higher maximum wind speed could remove more PM from leaves. Rainfall removed mainly large and coarse particles, while fine particles adhered more strongly to the foliage. These results suggested that the effects of local weather conditions (e.g., rainfall, strong wind), different seasons, and pollution levels should be considered in evaluating total PM accumulation on leaves.

Variational Assimilation of Global Microwave Rainfall Retrievals: Physical and Dynamical Impact on GEOS Analyses and Forecasts

NASA Technical Reports Server (NTRS)

Lin, Xin; Zhang, Sara Q.; Hou, Arthur Y.

2006-01-01

Global microwave rainfall retrievals from a 5-satellite constellation, including TMI from TRMM, SSWI from DMSP F13, F14 and F15, and AMSR-E from EOS-AQUA, are assimilated into the NASA Goddard Earth Observing System (GEOS) Data Assimilation System (DAS) using a 1-D variational continuous assimilation (VCA) algorithm. The physical and dynamical impact of rainfall assimilation on GEOS analyses and forecasts is examined at various temporal and spatial scales. This study demonstrates that the 1-D VCA algorithm, which was originally developed and evaluated for rainfall assimilations over tropical oceans, can effectively assimilate satellite microwave rainfall retrievals and improve GEOS analyses over both the Tropics and the extratropics where the atmospheric processes are dominated by different large-scale dynamics and moist physics, and also over the land, where rainfall estimates from passive microwave radiometers are believed to be less accurate. Results show that rainfall assimilation renders the GEOS analysis physically and dynamically more consistent with the observed precipitation at the monthly-mean and 6-hour time scales. Over regions where the model precipitation tends to misbehave in distinctly different rainy regimes, the 1-D VCA algorithm, by compensating for errors in the model s moist time-tendency in a 6-h analysis window, is able to bring the rainfall analysis closer to the observed. The radiation and cloud fields also tend to be in better agreement with independent satellite observations in the rainfall-assimilation m especially over regions where rainfall analyses indicate large improvements. Assimilation experiments with and without rainfall data for a midlatitude frontal system clearly indicates that the GEOS analysis is improved through changes in the thermodynamic and dynamic fields that respond to the rainfall assimilation. The synoptic structures of temperature, moisture, winds, divergence, and vertical motion, as well as vorticity are more realistically captured across the front. Short-term forecasts using initial conditions assimilated with rainfall data also show slight improvements. 1

[Dust storms trend in the Capital Circle of China over the past 50 years and its correlation with temperature, precipitation and wind].

PubMed

Chen, Yu-fu; Tang, Hai-ping

2005-01-01

The trends of number of dust storm days of the selected 11 meteorological stations from their established year to 2000 as well as their correlations with temperature, precipitation and wind are revealed. The number of dust storm days of the Capital Circle of China is distinctly variable in space and time. The numbers of dust storm days of the western area are far more than those of the eastern area. The interannual variability of number of dust storm days is remarkable. The number of dust storm days of the following 7 stations, Erlianhaote, Abaga, Xilinhaote, Fengning, Zhangjiakou, Huailai and Beijing, declined along the past decades, but those of the other four stations had no significant upward or downward trends. There is a marked seasonality of the number of dust storm days, and the maximum was in April. The correlation between number of dust storm days and number of days of mean wind velocity > 5 m/s, which is critical wind velocity to entrain sand into the air, was strongest among the three climatic factor. There were significant positive correlations between the number of dust storm days and number of days of mean wind velocity > 5 m/s in 6 stations. The second strongest climatic factor correlated with the number of dust storm days is temperature. There are significant negative correlations between the number of dust storm days and mean annual temperature, mean winter temperature, mean spring temperature in 3 or 4 stations. The correlation between the number of dust storm days and precipitation is weakest. Only one station, Zhurihe, showes significant negative correlation between the number of dust storm days and spring rainfall. There are 4 stations whose number of dust storm days don't significantly correlate with the climate. In the end, the spatial-temporal variability of dust storms and its relation with climate in the Capital Circle of China were discussed thoroughly.

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.

Soil slip/debris flow localized by site attributes and wind-driven rain in the San Francisco Bay region storm of January 1982

USGS Publications Warehouse

Pike, R.J.; Sobieszczyk, S.

2008-01-01

GIS analysis at 30-m resolution reveals that effectiveness of slope-destabilizing processes in the San Francisco Bay area varies with compass direction. Nearly half the soil slip/debris flows mapped after the catastrophic rainstorm of 3-5 January 1982 occurred on slopes that face S to WSW, whereas fewer than one-quarter have a northerly aspect. Azimuthal analysis of hillside properties for susceptible terrain near the city of Oakland suggests that the skewed aspect of these landslides primarily reflects vegetation type, ridge and valley alignment, and storm-wind direction. Bedrock geology, soil expansivity, and terrain height and gradient also were influential but less so; the role of surface curvature is not wholly resolved. Normalising soil-slip aspect by that of the region's NNW-striking topography shifts the modal azimuth of soil-slip aspect from SW to SE, the direction of origin of winds during the 1982 storm-but opposite that of the prevailing WNW winds. Wind from a constant direction increases rainfall on windward slopes while diminishing it on leeward slopes, generating a modelled difference in hydrologically effective rainfall of up to 2:1 on steep hillsides in the Oakland area. This contrast is consistent with numerical simulations of wind-driven rain and with rainfall thresholds for debris-flow activity. We conclude that storm winds from the SE in January 1982 raised the vulnerability of the Bay region's many S-facing hillsides, most of which are covered in shallow-rooted shrub and grass that offer minimal resistance to soil slip. Wind-driven rainfall also appears to have controlled debris-flow location in a major 1998 storm and probably others. Incorporating this overlooked influence into GIS models of debris-flow likelihood would improve predictions of the hazard in central California and elsewhere.

Influence of land-surface evapotranspiration on the earth's climate

NASA Technical Reports Server (NTRS)

Shukla, J.; Mintz, Y.

1982-01-01

Land-surface evapotranspiration is shown to strongly influence global fields of rainfall, temperature and motion by calculations using a numerical model of the atmosphere, confirming the general belief in the importance of evapotranspiration-producing surface vegetation for the earth's climate. The current version of the Goddard Laboratory atmospheric general circulation model is used in the present experiment, in which conservation equations for mass, momentum, moisture and energy are expressed in finite-difference form for a spherical grid to calculate (1) surface pressure field evolution, and (2) the wind, temperature, and water vapor fields at nine levels between the surface and a 20 km height.

Automated Statistical Forecast Method to 36-48H ahead of Storm Wind and Dangerous Precipitation at the Mediterranean Region

NASA Astrophysics Data System (ADS)

Perekhodtseva, E. V.

2009-09-01

Development of successful method of forecast of storm winds, including squalls and tornadoes and heavy rainfalls, that often result in human and material losses, could allow one to take proper measures against destruction of buildings and to protect people. Well-in-advance successful forecast (from 12 hours to 48 hour) makes possible to reduce the losses. Prediction of the phenomena involved is a very difficult problem for synoptic till recently. The existing graphic and calculation methods still depend on subjective decision of an operator. Nowadays in Russia there is no hydrodynamic model for forecast of the maximal precipitation and wind velocity V> 25m/c, hence the main tools of objective forecast are statistical methods using the dependence of the phenomena involved on a number of atmospheric parameters (predictors). Statistical decisive rule of the alternative and probability forecast of these events was obtained in accordance with the concept of "perfect prognosis" using the data of objective analysis. For this purpose the different teaching samples of present and absent of this storm wind and rainfalls were automatically arranged that include the values of forty physically substantiated potential predictors. Then the empirical statistical method was used that involved diagonalization of the mean correlation matrix R of the predictors and extraction of diagonal blocks of strongly correlated predictors. Thus for these phenomena the most informative predictors were selected without loosing information. The statistical decisive rules for diagnosis and prognosis of the phenomena involved U(X) were calculated for choosing informative vector-predictor. We used the criterion of distance of Mahalanobis and criterion of minimum of entropy by Vapnik-Chervonenkis for the selection predictors. Successful development of hydrodynamic models for short-term forecast and improvement of 36-48h forecasts of pressure, temperature and others parameters allowed us to use the prognostic fields of those models for calculations of the discriminant functions in the nodes of the grid 150x150km and the values of probabilities P of dangerous wind and thus to get fully automated forecasts. In order to change to the alternative forecast the author proposes the empirical threshold values specified for this phenomenon and advance period 36 hours. In the accordance to the Pirsey-Obukhov criterion (T), the success of these automated statistical methods of forecast of squalls and tornadoes to 36 -48 hours ahead and heavy rainfalls in the warm season for the territory of Italy, Spain and Balkan countries is T = 1-a-b=0,54: 0,78 after author experiments. A lot of examples of very successful forecasts of summer storm wind and heavy rainfalls over the Italy and Spain territory are submitted at this report. The same decisive rules were applied to the forecast of these phenomena during cold period in this year too. This winter heavy snowfalls in Spain and in Italy and storm wind at this territory were observed very often. And our forecasts are successful.

Exploratory Long-Range Models to Estimate Summer Climate Variability over Southern Africa.

NASA Astrophysics Data System (ADS)

Jury, Mark R.; Mulenga, Henry M.; Mason, Simon J.

1999-07-01

Teleconnection predictors are explored using multivariate regression models in an effort to estimate southern African summer rainfall and climate impacts one season in advance. The preliminary statistical formulations include many variables influenced by the El Niño-Southern Oscillation (ENSO) such as tropical sea surface temperatures (SST) in the Indian and Atlantic Oceans. Atmospheric circulation responses to ENSO include the alternation of tropical zonal winds over Africa and changes in convective activity within oceanic monsoon troughs. Numerous hemispheric-scale datasets are employed to extract predictors and include global indexes (Southern Oscillation index and quasi-biennial oscillation), SST principal component scores for the global oceans, indexes of tropical convection (outgoing longwave radiation), air pressure, and surface and upper winds over the Indian and Atlantic Oceans. Climatic targets include subseasonal, area-averaged rainfall over South Africa and the Zambezi river basin, and South Africa's annual maize yield. Predictors and targets overlap in the years 1971-93, the defined training period. Each target time series is fitted by an optimum group of predictors from the preceding spring, in a linear multivariate formulation. To limit artificial skill, predictors are restricted to three, providing 17 degrees of freedom. Models with colinear predictors are screened out, and persistence of the target time series is considered. The late summer rainfall models achieve a mean r2 fit of 72%, contributed largely through ENSO modulation. Early summer rainfall cross validation correlations are lower (61%). A conceptual understanding of the climate dynamics and ocean-atmosphere coupling processes inherent in the exploratory models is outlined.Seasonal outlooks based on the exploratory models could help mitigate the impacts of southern Africa's fluctuating climate. It is believed that an advance warning of drought risk and seasonal rainfall prospects will improve the economic growth potential of southern Africa and provide additional security for food and water supplies.

Flight thresholds and seasonal variations in flight activity of the light-brown apple moth, Epiphyas postvittana (Walk.) (Tortricidae), in Victoria, Australia.

PubMed

Danthanarayana, W

1976-12-01

The flight activity of Epiphyas postvittana was studied at two sites near Melbourne with the aid of suction traps, over a period of 4 years. Maximum numbers were found to fly during the period September to March with peak activity coinciding with the emergence of winter, spring and summer generation moths. E. postivittana is predominantly a nocturnal flier with maximum activity around 20.00-24.00 h. The lower temperature threshold of flight was 8-11°C. The upper temperature threshold varied from 20-21°C, 24-25°C and 27-28°C for the winter, spring and summer generation moths respectively. Flight was highly influenced by the prevailing wind. The lower wind speed threshold was 0.5-0.8 m -s and the upper wind speed threshold was 2.6-2.7 m -s . The relationship between wind speed and the amount of flight was non-linear, with the frequency of flights decreasing sharply with increasing wind speed. No flights occurred at wind speeds greater than 2.8 m -s . Variation in relative humidity had no influence on flight, but lack of rain favoured flight. The amount of flight activity and the amount of rainfall were negatively correlated; flights did not occur when the daily precipitation exceeded 32.5 mm, and with a precipitation exceeding 39 mm no flights could be expected. The value of these findings to pest control programmes is discussed.

Latitudinal variation in summer monsoon rainfall over Western Ghat of India and its association with global sea surface temperatures.

PubMed

Revadekar, J V; Varikoden, Hamza; Murumkar, P K; Ahmed, S A

2018-02-01

The Western Ghats (WG) of India are basically north-south oriented mountains having narrow zonal width with a steep rising western face. The summer monsoon winds during June to September passing over the Arabian Sea are obstructed by the WG and thus orographically uplift to produce moderate-to-heavy precipitation over the region. However, it is seen that characteristic features of rainfall distribution during the season vary from north to south. Also its correlation with all-India summer monsoon rainfall increases from south to north. In the present study, an attempt is also made to examine long-term as well as short-term trends and variability in summer monsoon rainfall over different subdivisions of WG using monthly rainfall data for the period 1871-2014. Konkan & Goa and Coastal Karnataka show increase in rainfall from 1871 to 2014 in all individual summer monsoon months. Short-term trend analysis based on 31-year sliding window indicates that the trends are not monotonous, but has epochal behavior. In recent epoch, magnitudes of negative trends are consistently decreasing and have changed its sign to positive during 1985-2014. It has been observed that Indian Ocean Dipole (IOD) plays a dominant positive role in rainfall over entire WG in all summer monsoon months, whereas role of Nino regions are asymmetric over WG rainfall. Indian summer monsoon is known for its negative relationship with Nino SST. Negative correlations are also seen for WG rainfall with Nino regions but only during onset and withdrawal phase. During peak monsoon months July and August subdivisions of WG mostly show positive correlation with Nino SST. Copyright © 2017 Elsevier B.V. All rights reserved.

On the dynamic forcing of short-term climate fluctuations by feedback mechanisms

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

Reiter, E.R.

1979-09-01

The energies involved in the general circulation of the atmosphere, especially the zonal available potential energy, show considerable interannual variability, suggesting the presence of various internal feedback mechanisms in the ocean-atmosphere system. Sea-surface temperature (SST) variations appear to have some effect on the hydrological cycle. The possible existence of feedback mechanisms between ocean and atmosphere seem to be evident in some of the data from the North Pacific and North Atlantic. One of these proposed mechanisms involves the variation in the convergence between the North and South Pacific trade-wind systems and is strongly reflected in rainfall variability within the drymore » region of the equatorial Pacific. Similar variations appear in low-latitude SST anomalies. The convergence between the two trade-wind systems in the Atlantic region also undergoes marked interannual variations. This quasi-biennial oscillation (QBO) in trade-wind convergence over the Atlantic appears to be tied to the global QBO of equatorial stratospheric winds and to regional rainfall regimes in the dry region of northeastern Brazil. A variability pattern of SST's with a QBO has been detected off the coast of Senegal, in the Gulf of Guinea and even in the Gulf Stream as it leaves the North American continental shelf. Possible physical connections between some of these QBO's are pointed out by a hypothetical feedback model. It is also suggested that interaction of a QBO with the annual cycle may lead to beating frequencies resembling climatic trends of a duration of several years.« less

Causes of Upper-Ocean Temperature Anomalies in the Tropical North Atlantic

NASA Astrophysics Data System (ADS)

Rugg, A.; Foltz, G. R.; Perez, R. C.

2016-02-01

Hurricane activity and regional rainfall are strongly impacted by upper ocean conditions in the tropical North Atlantic, defined as the region between the equator and 20°N. A previous study analyzed a strong cold sea surface temperature (SST) anomaly that developed in this region during early 2009 and was recorded by the Pilot Research Array in the Tropical Atlantic (PIRATA) moored buoy at 4°N, 23°W (Foltz et al. 2012). The same mooring shows a similar cold anomaly in the spring of 2015 as well as a strong warm anomaly in 2010, offering the opportunity for a more comprehensive analysis of the causes of these events. In this study we examine the main causes of the observed temperature anomalies between 1998 and 2015. Basin-scale conditions during these events are analyzed using satellite SST, wind, and rain data, as well as temperature and salinity profiles from the NCEP Global Ocean Data Assimilation System. A more detailed analysis is conducted using ten years of direct measurements from the PIRATA mooring at 4°N, 23°W. Results show that the cooling and warming anomalies were caused primarily by wind-driven changes in surface evaporative cooling, mixed layer depth, and upper-ocean vertical velocity. Anomalies in surface solar radiation acted to damp the wind-driven SST anomalies in the latitude bands of the ITCZ (3°-8°N). Basin-scale analyses also suggest a strong connection between the observed SST anomalies and the Atlantic Meridional Mode, a well-known pattern of SST and surface wind anomalies spanning the tropical Atlantic.

Diagnosing Possible Anthropogenic Contributions to Heavy Colorado Rainfall in September 2013

NASA Astrophysics Data System (ADS)

Pall, Pardeep; Patricola, Christina; Wehner, Michael; Stone, Dáithí; Paciorek, Christopher; Collins, William

2015-04-01

Unusually heavy rainfall occurred over the Colorado Front Range during early September 2013, with record or near-record totals recorded in several locations. It was associated predominantly with a stationary large-scale weather pattern (akin to the North American Monsoon, which occurs earlier in the year) that drove a strong plume of deep moisture inland from the Gulf of Mexico against the Front Range foothills. The resulting floods across the South Platte River basin impacted several thousands of people and many homes, roads, and businesses. To diagnose possible anthropogenic contributions to the odds of such heavy rainfall, we adapt an existing event attribution paradigm of modelling an 'event that was' for September 2013 and comparing it to a modelled 'event that might have been' for that same time but for the absence of historical anthropogenic drivers of climate. Specifically, we first perform 'event that was' simulations with the regional Weather Research and Forecasting (WRF) model at 12 km resolution over North America, driven by NCEP2 re-analysis. We then re-simulate, having adjusted the re-analysis to 'event that might have been conditions' by modifying atmospheric greenhouse gas and other pollutant concentrations, temperature, humidity, and winds, as well as sea ice coverage, and sea-surface temperatures - all according to estimates from global climate model simulations. Thus our findings are highly conditional on the driving re-analysis and adjustments therein, but the setup allows us to elucidate possible mechanisms responsible for heavy Colorado rainfall in September 2013. Our model results suggests that, given an insignificant change in the pattern of large-scale driving weather, there is an increase in atmospheric water vapour under anthropogenic climate warming leading to a substantial increase in the probability of heavy rainfall occurring over the South Platte River basin in September 2013.

Diagnosing Possible Anthropogenic Contributions to Heavy Colorado Rainfall in September 2013

NASA Astrophysics Data System (ADS)

Pall, P.; Patricola, C. M.; Wehner, M. F.; Stone, D. A.; Paciorek, C. J.; Collins, W.

2014-12-01

Unusually heavy rainfall occurred over the Colorado Front Range during early September 2013, with record or near-record totals recorded in several locations. It was associated predominantly with a stationary large-scale weather pattern (akin to the North American Monsoon, which occurs earlier in the year) that drove a strong plume of deep moisture inland from the Gulf of Mexico against the Front Range foothills. The resulting floods impacted several thousands of people and many homes, roads, and businesses. To diagnose possible anthropogenic contributions to the odds of such heavy rainfall, we adapt an existing event attribution paradigm of modelling a 'world that was' for September 2013 and comparing it to a modelled 'world that might have been' for that same time but for the absence of historical anthropogenic drivers of climate. Specifically, we first perform 'world that was' simulations with the regional WRF model at 12 km resolution over North America, driven by NCEP2 re-analysis. We then re-simulate, having adjusted the re-analysis to 'world that might have been conditions' by modifying atmospheric greenhouse gas and other pollutant concentrations, temperature, humidity, and winds, as well as sea ice coverage, and sea-surface temperatures - all according to estimates from global climate model simulations. Thus our findings are highly conditional on the driving re-analysis and adjustments therein, but the setup allows us to elucidate possible mechanisms responsible for heavy Colorado rainfall in September 2013. For example, preliminary analysis suggests that, given no change in the pattern of large-scale driving weather, there is an increase in atmospheric water vapour under anthropogenic climate warming leading to a substantial increase in the odds of heavy rainfall over the Front Range.

Validation of crowdsourced automatic rain gauge measurements in Amsterdam

NASA Astrophysics Data System (ADS)

de Vos, Lotte; Leijnse, Hidde; Overeem, Aart; Uijlenhoet, Remko

2016-04-01

The increasing number of privately owned weather stations and the facilitating role the internet to make this data publicly available, has led to several online platforms that collect and visualize crowdsourced weather data. This has resulted in ever increasing freely available datasets of weather measurements generated by amateur weather enthusiasts. Because of the lack of quality control and the frequent absence of metadata, these measurements are often considered as unreliable. Given the often large variability of weather variables in space and time, and the generally low number of official weather stations, this growing quantity of crowdsourced data may become an important additional source of information. Amateur weather observations have become more frequent over the past decade due to weather stations becoming more user-friendly and affordable. The variables measured by these weather stations are temperature, pressure and dew point, and in some cases wind and rainfall. Meteorological data from crowdsourced automatic weather stations in cities have primarily been used to examine the urban heat island effect. Thus far, these studies have focused on the comparison of the crowdsourced station temperature measurements with a nearby WMO-standard weather station, which is often located in a rural area or the outskirts of a city, generally not being representative of the city center. Instead of temperature, the rainfall measurements by the stations are examined. This research focuses on the combined ability of a large number of privately owned weather stations in an urban setting to correctly monitor rainfall. A set of 64 automatic weather stations distributed over Amsterdam (The Netherlands) that have at least 3 months of precipitation measurement during one year are evaluated. Precipitation measurements from stations are compared to a merged radar-gauge precipitation product. Disregarding sudden jumps in station measured precipitation, the accumulative rainfall over time in most stations showed an underestimation of rainfall compared to the accumulative values found in the corresponding radar pixel of the reference. Special consideration is given to the identification of faulty measurements without the need to obtain additional meta-data, such as setup and surroundings. This validation will show the potential of crowdsourced automatic weather stations for future urban rainfall monitoring.

Met Éireann high resolution reanalysis for Ireland

NASA Astrophysics Data System (ADS)

Gleeson, Emily; Whelan, Eoin; Hanley, John

2017-03-01

The Irish Meteorological Service, Met Éireann, has carried out a 35-year very high resolution (2.5 km horizontal grid) regional climate reanalysis for Ireland using the ALADIN-HIRLAM numerical weather prediction system. This article provides an overview of the reanalysis, called MÉRA, as well as a preliminary analysis of surface parameters including screen level temperature, 10 m wind speeds, mean sea-level pressure (MSLP), soil temperatures, soil moisture and 24 h rainfall accumulations. The quality of the 3-D variational data assimilation used in the reanalysis is also assessed. Preliminary analysis shows that it takes almost 12 months to spin up the deep soil in terms of moisture, justifying the choice of running year-long spin up periods. Overall, the model performed consistently over the time period. Small biases were found in screen-level temperatures (less than -0.5 °C), MSLP (within 0.5 hPa) and 10 m wind speed (up to 0.5 m s-1) Soil temperatures are well represented by the model. 24 h accumulations of precipitation generally exhibit a small positive bias of ˜ 1 mm per day and negative biases over mountains due to a mismatch between the model orography and the geography of the region. MÉRA outperforms the ERA-Interim reanalysis, particularly in terms of standard deviations in screen-level temperatures and surface winds. This dataset is the first of its kind for Ireland that will be made publically available during spring 2017.

Influence of Offshore Initial Moisture Field and Convection on the Development of Coastal Convection in a Heavy Rainfall Event over South China during the Pre-summer Rainy Season

NASA Astrophysics Data System (ADS)

Lu, Rong; Sun, Jianhua; Fu, Shenming

2017-04-01

This paper utilizes the observation data from the Southern China Monsoon Rainfall Experiment (SCMREX) and the numerical experiments to investigate the influence of moisture amount and convection development over the northern South China Sea on a heavy rainfall event in coastal South China on May 8, 2014. Intensive sounding and wind profiles data reveal that there existed a convergence region formed by the southwesterly and easterly jet in the Pearl River delta, which provided favorable conditions for the development of convection. Whether the initial relative humidity field was increased or decreased in the offshore area, or turning off sensible and latent heat release from the cumulus and microphysical processes, had significant effects on the intensity and movement of convection in the coastal areas of Guangdong owing to the adjustment of temperature and wind fields. Especially, when increasing offshore initial humidity, prosperous sea convection modified the circulation in the entire simulation area, and suppressed the development of convection over land. Moreover, if sensible and latent heat from cumulus and microphysical processes was turned off, the low-level jets could reach further north, and the convective system moved to the northeast in the later stage. These experiments indicate that offshore initial moisture filed and convection activity are indeed important for precipitation forecast in the coastal areas, therefore it's necessary to enhance offshore observation and data assimilation methods in the future.

Prognostic Aspects of Sub-seasonal Rainfall Characteristics using the Outputs of General Circulation Model: An Application of Statistical Downscaling and Temporal Disaggregation

NASA Astrophysics Data System (ADS)

Singh, A.; Mohanty, U. C.; Ghosh, K.

2015-12-01

Most regions of India experience varied rainfall duration during the southwest monsoon, changes in which exhibit major impact not only agriculture, but also other sectors like hydrology, agriculture, food and fodder storage etc. In addition, changes in sub-seasonal rainfall characteristics highly impact the rice production. As part of the endeavor seasonal climate outlook, as well as information for weather within climate may be helpful for advance planning and risk management in agriculture. The General Circulation Model (GCM) provide an alternative to gather information for weather within climate but variability is very low in comparison to observation. On the other hand, the spatial resolution of GCM predicted rainfall is not found at the observed station/grid point. To tackle the problem, initially a statistical downscaling over 19 station of Odisha state is undertaken using the atmospheric parameters predicted by a GCM (NCEP-CFSv2). For the purpose, an extended domain is taken for analyzing the significant zone for the atmospheric parameters like zonal wind at 850hPa, Sea Surface Temperature (SST), geopotential height. A statistical model using the pattern projection method is further developed based on empirical orthogonal function. The downscaled rainfall is found better in association with station observation in comparison to raw GCM prediction in view of deterministic and probabilistic skill measure. Further, the sub-seasonal and seasonal forecast from the GCMs can be used at different time steps for risk management. Therefore, downscaled seasonal/monthly rainfall is further converted to sub-seasonal/daily time scale using a non-homogeneous markov model. The simulated weather sequences are further compared with the observed sequence in view of categorical rainfall events. The outcomes suggest that the rainfall amount are overestimated for excess rainfall and henceforth larger excess rainfall events can be realized. The skill for prediction of rainfall events corresponding to lower thresholds is found higher. A detail discussion regarding skill of spatial downscale rainfall at observed stations and its further representation of sub-seasonal characteristics (spells, less rainfall, heavy rainfall, and moderate rainfall events) of rainfall for disaggregated outputs will be presented.

Observed formation of easterly waves over northeast Africa

NASA Astrophysics Data System (ADS)

Jury, Mark R.

2018-06-01

This study explores the thermodynamic and kinematic features of easterly waves over northeast Africa in July-September season 2005-2015. A daily African easterly wave (AEW) index is formulated from transient satellite rainfall and reanalysis vorticity, and the ten most intense cases are studied by composite analysis. Surface moisture is advected from central Africa towards the Red Sea during AEW formation. The anomalous 600 hPa wind circulation is comprized of a cyclonic-south anticyclonic-north rotor pair and accentuated easterly jet along 17N. Composite convection is initiated over Ethiopia and subsequently intensifies following interaction with a zonal circulation located downstream. Composite AEW temperature anomalies reveal a cool lower-warm upper layer heating profile. 2-8 day variance of satellite OLR reaches a maximum over the southern Arabian Peninsula, suggesting an upstream role for surface heating and the Somali Jet. The large scale environment is analyzed by regression of the AEW index onto daily fields of rainfall, surface air pressure and temperature in July-September season ( N = 1004). The rainfall regression reflects a westward propagating AEW wave-train of higher values on 13N and lower values on 7N with a longitude spacing of 25°. The air pressure and temperature regression features a N-S dipole indicating an anomalous northward ITCZ. A low pressure signal west of the Maritime Continent coupled with a warm zone across the South Indian Ocean coincides with AEW formation over the eastern Sahel.

Impact of meteorological factors on the incidence of bacillary dysentery in Beijing, China: A time series analysis (1970-2012).

PubMed

Yan, Long; Wang, Hong; Zhang, Xuan; Li, Ming-Yue; He, Juan

2017-01-01

Influence of meteorological variables on the transmission of bacillary dysentery (BD) is under investigated topic and effective forecasting models as public health tool are lacking. This paper aimed to quantify the relationship between meteorological variables and BD cases in Beijing and to establish an effective forecasting model. A time series analysis was conducted in the Beijing area based upon monthly data on weather variables (i.e. temperature, rainfall, relative humidity, vapor pressure, and wind speed) and on the number of BD cases during the period 1970-2012. Autoregressive integrated moving average models with explanatory variables (ARIMAX) were built based on the data from 1970 to 2004. Prediction of monthly BD cases from 2005 to 2012 was made using the established models. The prediction accuracy was evaluated by the mean square error (MSE). Firstly, temperature with 2-month and 7-month lags and rainfall with 12-month lag were found positively correlated with the number of BD cases in Beijing. Secondly, ARIMAX model with covariates of temperature with 7-month lag (β = 0.021, 95% confidence interval(CI): 0.004-0.038) and rainfall with 12-month lag (β = 0.023, 95% CI: 0.009-0.037) displayed the highest prediction accuracy. The ARIMAX model developed in this study showed an accurate goodness of fit and precise prediction accuracy in the short term, which would be beneficial for government departments to take early public health measures to prevent and control possible BD popularity.

The past, present and future of African dust.

PubMed

Evan, Amato T; Flamant, Cyrille; Gaetani, Marco; Guichard, Françoise

2016-03-24

African dust emission and transport exhibits variability on diurnal to decadal timescales and is known to influence processes such as Amazon productivity, Atlantic climate modes, regional atmospheric composition and radiative balance and precipitation in the Sahel. To elucidate the role of African dust in the climate system, it is necessary to understand the factors governing its emission and transport. However, African dust is correlated with seemingly disparate atmospheric phenomena, including the El Niño/Southern Oscillation, the North Atlantic Oscillation, the meridional position of the intertropical convergence zone, Sahelian rainfall and surface temperatures over the Sahara Desert, all of which obfuscate the connection between dust and climate. Here we show that the surface wind field responsible for most of the variability in North African dust emission reflects the topography of the Sahara, owing to orographic acceleration of the surface flow. As such, the correlations between dust and various climate phenomena probably arise from the projection of the winds associated with these phenomena onto an orographically controlled pattern of wind variability. A 161-year time series of dust from 1851 to 2011, created by projecting this wind field pattern onto surface winds from a historical reanalysis, suggests that the highest concentrations of dust occurred from the 1910s to the 1940s and the 1970s to the 1980s, and that there have been three periods of persistent anomalously low dust concentrations--in the 1860s, 1950s and 2000s. Projections of the wind pattern onto climate models give a statistically significant downward trend in African dust emission and transport as greenhouse gas concentrations increase over the twenty-first century, potentially associated with a slow-down of the tropical circulation. Such a dust feedback, which is not represented in climate models, may be of benefit to human and ecosystem health in West Africa via improved air quality and increased rainfall. This feedback may also enhance warming of the tropical North Atlantic, which would make the basin more suitable for hurricane formation and growth.

2010 weather and aeolian sand-transport data from the Colorado River corridor, Grand Canyon, Arizona

USGS Publications Warehouse

Dealy, Timothy P.; East, Amy E.; Fairley, Helen C.

2014-01-01

Measurements of weather parameters and aeolian sand transport were made in 2010 near selected archeological sites in the Colorado River corridor through Grand Canyon, Arizona. Data collected in 2010 indicate event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Differences in weather patterns between 2009 and 2010 included a slightly later spring windy season, greater spring precipitation and annual rainfall totals, and a later onset and length of the reduced diurnal barometric-pressure fluctuations commonly associated with summer monsoon conditions. The increase in spring precipitation was consistent with the 2010 spring El Niño conditions compared to the 2009 spring La Niña conditions, whereas the subsequent transition to an El Niño-Southern Oscillation neutral phase appeared to delay the reduction in diurnal barometric fluctuations.

A new technology for harnessing the dye polluted water and dye collection in a chemical factory.

PubMed

Pu, J P; Pu, P M; Hu, C H; Qian, J L; Pu, J X; Hua, J K

2001-04-01

A new technology for harnessing the dye polluted water and dye collection was developed. It is based on the enhanced evaporation by using solar, wind and air temperature energy and additional heat-electric energy. It consists of four parts: (1) evaporation carrier system (evaporation carrier and frame for evaporation carrier) for polluted water; (2) polluted water circulating system (pumping-spraying-collecting); (3) heating system; (4) workshop with polluted water reservoir-tanks and rainfall prevention roof. The polluted water was (heated in case necessary) sprayed to the evaporation carrier system and the water was evaporated when it moved in the space and downward along the carrier mainly by using natural (solar, wind and air temperature energy). In case, when there is no roof for the carrier system, the polluted water can be stored in the reservoirs (storage volume for about 20 days). The first 10-25 mm rainfall also need to be stored in the reservoirs to meet the state standard for discharging wastewater. The dye may be collected at the surface in the reservoir-tanks and the crystallized salt may be collected at the bottom plate. The black-color wastewater released by the factory is no more discharged to the surface water system of Taihu Lake Basin. About 2 kg dye and 200 kg industrial salt may be collected from each tone of the polluted water. The non-pollution production of dye may be realized by using this technology with environmental, economical and social benefits.

Assessing Weather Effects on Dengue Disease in Malaysia

PubMed Central

Cheong, Yoon Ling; Burkart, Katrin; Leitão, Pedro J.; Lakes, Tobia

2013-01-01

The number of dengue cases has been increasing on a global level in recent years, and particularly so in Malaysia, yet little is known about the effects of weather for identifying the short-term risk of dengue for the population. The aim of this paper is to estimate the weather effects on dengue disease accounting for non-linear temporal effects in Selangor, Kuala Lumpur and Putrajaya, Malaysia, from 2008 to 2010. We selected the weather parameters with a Poisson generalized additive model, and then assessed the effects of minimum temperature, bi-weekly accumulated rainfall and wind speed on dengue cases using a distributed non-linear lag model while adjusting for trend, day-of-week and week of the year. We found that the relative risk of dengue cases is positively associated with increased minimum temperature at a cumulative percentage change of 11.92% (95% CI: 4.41–32.19), from 25.4 °C to 26.5 °C, with the highest effect delayed by 51 days. Increasing bi-weekly accumulated rainfall had a positively strong effect on dengue cases at a cumulative percentage change of 21.45% (95% CI: 8.96, 51.37), from 215 mm to 302 mm, with the highest effect delayed by 26–28 days. The wind speed is negatively associated with dengue cases. The estimated lagged effects can be adapted in the dengue early warning system to assist in vector control and prevention plan. PMID:24287855

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.

An Investigation of the Influence of Urban Areas on Rainfall Using a Cloud-Mesoscale Model and TRMM Satellite

NASA Technical Reports Server (NTRS)

Shepherd, J. Marshall; Starr, David OC (Technical Monitor)

2002-01-01

The urban heat island (UHI) has become a widely acknowledged, observed, and researched phenomena because of its broad implications. It is estimated that by the year 2025, 80% of the world's population will live in cities (UNFP, 1999). The UHI has been documented in the literature to affect local and regional temperature distributions, wind patterns and air quality. The UHI can also impact the development of clouds and precipitation in and around cities. This paper will focus primarily on the UHI's impact on precipitation. In the past 30 years, several observational and climatological studies have theorized that the UHI can have a significant influence on mesoscale circulations and resulting precipitation (see Shepherd et al. 2002 for a thorough review). More recent studies have continued to validate and extend the findings from pre and post-METROMEX investigations. Shepherd et al. (2002) was one of the first (and possibly the first) attempts to identify rainfall modification by urban areas using satellite-based rainfall measurements. Using a 15-month (spanning three years) analysis of mean rainfall rates, the cities of Atlanta, Montgomery, Dallas, Waco, and San Antonio were examined. Shepherd et al. (2002) found that the average percentage increase in mean rainfall rate in a hypothesized "downwind maximum impact area" over an "upwind control area" was 28.4% with a range of 14.6 to 51%. The typical distance of the downwind rainfall rate anomaly from the urban center was 30-60 km, consistent with earlier studies. This fact provides confidence that UHI-rainfall effects are real and detectable by TRMM satellite estimates.

A search for solar related changes in tropospheric weather

NASA Technical Reports Server (NTRS)

Mohanakumar, K.

1989-01-01

The possibility that solar variations associated with the 11-year solar cycle may be the cause of the changes in tropospheric weather and climate has been the subject to scientific investigation for several decades. Meteorologists are greatly concerned with the changes in tropospheric phenomena. An attempt was made to find solar activity related changes in tropospheric weather, by the modulation of the quasi-biennial oscillation (QBO) of zonal wind at 50 mb. Rainfall and surface temperature data for a period of about three solar cycles, 1953 to 1988, from various stations in the Indian subcontinent were utilized. By extension, a possible teleconnection was looked for between the temperature changes in middle atmospheric levels and surface temperature when the data are stratified according to east or west phase of the QBO. The temperature data were averaged for January and February to represent the winter temperature and for July and August to represent the summer temperature.

Dengue transmission based on urban environmental gradients in different cities of Pakistan.

PubMed

Khalid, Bushra; Ghaffar, Abdul

2015-03-01

This study focuses on the dengue transmission in different regions of Pakistan. For this purpose, the data of dengue cases for 2009-2012 from four different cities (Rawalpindi, Islamabad, Lahore, and Karachi) of the country is collected, evaluated, and compiled. To identify the reasons and regions of higher risk of Dengue transmission, land use classification, analysis of climate covariates and drainage patterns was done. Analysis involves processing of SPOT 5 10 m, Landsat TM 30 m data sets, and SRTM 90 m digital elevation models by using remote sensing and GIS techniques. The results are based on the change in urbanization and population density, analysis of temperature, rainfall, and wind speed; calculation of drainage patterns including stream features, flow accumulation, and drainage density of the study areas. Results suggest that the low elevation areas with calm winds and minimum temperatures higher than the normal, rapid increase in unplanned urbanization, low flow accumulation, and higher drainage density areas favor the dengue transmission.

Variability in rainfall over tropical Australia during summer and relationships with the Bilybara High

NASA Astrophysics Data System (ADS)

Reason, C. J. C.

2018-04-01

Variability in summer rainfall over tropical Australia, defined here as that part of the continent north of 25° S, and its linkages with regional circulation are examined. In particular, relationships with the mid-level anticyclone (termed the Bilybara High) that exists over the northwestern Australia/Timor Sea region between August and April are considered. This High forms to the southwest of the upper-level anticyclone via a balance between the upper-level divergence over the region of tropical precipitation maximum and planetary vorticity advection and moves south and strengthens during the spring and summer. It is shown that variations in the strength and position of the Bilybara High are related to anomalies in precipitation and temperature over large parts of tropical Australia as well as some areas in the south and southeast of the landmass. Some of the interannual variations in the High are related to ENSO, but there are also a number of neutral years with large anomalies in the High and hence in rainfall. On decadal time scales, a strong relationship exists between the leading mode of tropical Australian rainfall and the Bilybara High. On both interannual and decadal scales, the relationships between the High and the regional rainfall involve changes in the monsoonal northwesterlies blowing towards northern Australia, and further south, in the easterly trade winds over the region.

Climate Prediction for Brazil's Nordeste: Performance of Empirical and Numerical Modeling Methods.

NASA Astrophysics Data System (ADS)

Moura, Antonio Divino; Hastenrath, Stefan

2004-07-01

Comparisons of performance of climate forecast methods require consistency in the predictand and a long common reference period. For Brazil's Nordeste, empirical methods developed at the University of Wisconsin use preseason (October January) rainfall and January indices of the fields of meridional wind component and sea surface temperature (SST) in the tropical Atlantic and the equatorial Pacific as input to stepwise multiple regression and neural networking. These are used to predict the March June rainfall at a network of 27 stations. An experiment at the International Research Institute for Climate Prediction, Columbia University, with a numerical model (ECHAM4.5) used global SST information through February to predict the March June rainfall at three grid points in the Nordeste. The predictands for the empirical and numerical model forecasts are correlated at +0.96, and the period common to the independent portion of record of the empirical prediction and the numerical modeling is 1968 99. Over this period, predicted versus observed rainfall are evaluated in terms of correlation, root-mean-square error, absolute error, and bias. Performance is high for both approaches. Numerical modeling produces a correlation of +0.68, moderate errors, and strong negative bias. For the empirical methods, errors and bias are small, and correlations of +0.73 and +0.82 are reached between predicted and observed rainfall.

Ten-Year Climatology of Summertime Diurnal Rainfall Rate Over the Conterminous U.S.

NASA Technical Reports Server (NTRS)

Matsui, Toshihisa; Mocko, David; Lee, Myong-In; Tao, Wei-Kuo; Suarez, Max J.; Pielke, Roger A., Sr.

2010-01-01

Diurnal cycles of summertime rainfall rates are examined over the conterminous United States, using radar-gauge assimilated hourly rainfall data. As in earlier studies, rainfall diurnal composites show a well-defined region of rainfall propagation over the Great Plains and an afternoon maximum area over the south and eastern portion of the United States. Zonal phase speeds of rainfall in three different small domains are estimated, and rainfall propagation speeds are compared with background zonal wind speeds. Unique rainfall propagation speeds in three different regions can be explained by the evolution of latent-heat theory linked to the convective available potential energy, than by gust-front induced or gravity wave propagation mechanisms.

The Relative Importance of Convective and Trade-wind Orographic Precipitation to Streamflow in the Luquillo Mountains, Eastern Puerto Rico

NASA Astrophysics Data System (ADS)

Scholl, M. A.; Shanley, J. B.; Occhi, M.; Scatena, F. N.

2012-12-01

Like many mountainous areas in the tropics, watersheds in the Luquillo Mountains of Puerto Rico (18.3° N) have abundant rainfall and stream discharge, but relatively little storage capacity. Therefore, the water supply is vulnerable to drought and water availability may be affected by projected changes in regional temperature and atmospheric dynamics due to global warming. To help determine the links between climate and water availability, precipitation patterns were analyzed, and stable-isotope signatures of precipitation from different seasonal weather systems were established to identify those that are most important in maintaining streamflow and groundwater recharge. Stable isotope data include cloud water, rainfall, throughfall, streamflow, and groundwater from the Rio Mameyes and Rio Icacos/ Rio Blanco watersheds. Precipitation inputs have a wide range of stable isotope values, from fog/cloud water with δ2H and δ18O averaging +3.2‰, -1.74‰ respectively, to tropical storm rain with values as low as -154‰, -20.4‰. Spatial and temporal patterns of water isotopic values on this Caribbean island are different than higher latitude, continental watersheds. The data exhibit a 'reverse seasonality', with higher isotopic values in winter and lower values in summer; and stable isotope values of stream water do not decrease as expected with increasing altitude, because of cloud water input. Rain isotopic values vary predictably with local and mesoscale weather patterns and correlate strongly with cloud altitude. This correlation allows us to assign isotopic signatures to different sources of precipitation, and to investigate which climate patterns contribute to streamflow and groundwater recharge. At a measurement site at 615 m in the Luquillo Mountains, the average length of time between rain events was 15 h, and 45% of the rain events were <2 mm, reflecting the frequent small rain events of the trade-wind orographic rainfall weather pattern. Long-term average streamflow isotopic composition indicates a disproportionately large contribution of this trade-wind precipitation to streamflow, highlighting the importance of this climate pattern to the hydrology of the watersheds. Isotopic composition of groundwater suggests a slightly higher proportion of convective precipitation, but still smaller than in total rainfall. Hydrograph separation experiments yielded information on stormflow characteristics, with quantification of contributing sources determined from water isotopes and solute chemistry. The evidence that intense convective rain events run off and light trade-wind showers appear to contribute much of the baseflow indicates that the area may undergo a change in water supply if the trade-wind orographic precipitation dynamics in the Caribbean are affected by future climate change.

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.

WIND DIRECTIONS ALOFT AND EFFECTS OF SEEDING ON PRECIPITATION IN THE WHITETOP EXPERIMENT*

PubMed Central

Lovasich, Jeanne L.; Neyman, Jerzy; Scott, Elizabeth L.; Smith, Jerome A.

1969-01-01

The subdivision of all the experimental days of the Whitetop project into two approximately equal groups, group W with predominantly westerly winds aloft and group E with frequent easterly winds, shows a remarkable difference in the apparent effect of seeding. On W days there was no detectable effect of seeding on rainfall. On E days with seeding, the average 24 hour precipitation in an area of about 100,000 square miles was significantly less than that without seeding by 46 per cent of the latter. The decrease resulted from a “decapitation” of the usual afternoon rise in rainfall. It may be significant that the afternoon maximum of natural precipitation on E days occurs some two hours later than on W days. If the actual cause of the differences in rainfall was seeding, then the loss of water resulting from operational, rather than experimental, seeding would have averaged eight million acre-feet per summer. PMID:16591800

Multiscale analyses on a massive immigration process of Sogatella furcifera (Horváth) in south-central China: influences of synoptic-scale meteorological conditions and topography

NASA Astrophysics Data System (ADS)

Wu, Qiu-Lin; Westbrook, John K.; Hu, Gao; Lu, Ming-Hong; Liu, Wan-Cai; Sword, Gregory A.; Zhai, Bao-Ping

2018-04-01

Mass landings of migrating white-backed planthopper, Sogatella furcifera (Horváth), can lead to severe outbreaks that cause heavy losses for rice production in East Asia. South-central China is the main infestation area on the annual migration loop of S. furcifera between the northern Indo-China Peninsula and mainland China; however, rice planthopper species are not able to survive in this region over winter. In this study, a trajectory analysis of movements from population source areas and a spatiotemporal dynamic analysis of mesoscale and synoptic weather conditions from 7 to 10 May 2012 were conducted using the weather research and forecasting (WRF) model to identify source areas of immigrants and determine how weather and topographic terrain influence insect landing. A sensitivity experiment was conducted with reduced topography using the WRF model to explain the associations among rainfall, topography, and light-trap catches of S. furcifera. The trajectory modeling results suggest that the source areas of S. furcifera immigrants into south-central China from 8 to 10 May were mainly southern Guangxi, northern Vietnam, and north-central Vietnam. The appearance of enormous catches of immigrant S. furcifera coincided with a period of rainstorms. The formation of transporting southerly winds was strongly associated with the topographic terrain. Additionally, the rainfall distribution and intensity over south-central China significantly decreased when topography was reduced in the model and were directly affected by wind circulation, which was associated with mountainous terrain that caused strong convection. This study indicates that migrating populations of S. furcifera were carried by the southwesterly low-level jets and that topographically induced convergent winds, precipitation, low temperatures, and wind shear acted as key factors that led to massive landings.

Multiscale analyses on a massive immigration process of Sogatella furcifera (Horváth) in south-central China: influences of synoptic-scale meteorological conditions and topography.

PubMed

Wu, Qiu-Lin; Westbrook, John K; Hu, Gao; Lu, Ming-Hong; Liu, Wan-Cai; Sword, Gregory A; Zhai, Bao-Ping

2018-04-30

Mass landings of migrating white-backed planthopper, Sogatella furcifera (Horváth), can lead to severe outbreaks that cause heavy losses for rice production in East Asia. South-central China is the main infestation area on the annual migration loop of S. furcifera between the northern Indo-China Peninsula and mainland China; however, rice planthopper species are not able to survive in this region over winter. In this study, a trajectory analysis of movements from population source areas and a spatiotemporal dynamic analysis of mesoscale and synoptic weather conditions from 7 to 10 May 2012 were conducted using the weather research and forecasting (WRF) model to identify source areas of immigrants and determine how weather and topographic terrain influence insect landing. A sensitivity experiment was conducted with reduced topography using the WRF model to explain the associations among rainfall, topography, and light-trap catches of S. furcifera. The trajectory modeling results suggest that the source areas of S. furcifera immigrants into south-central China from 8 to 10 May were mainly southern Guangxi, northern Vietnam, and north-central Vietnam. The appearance of enormous catches of immigrant S. furcifera coincided with a period of rainstorms. The formation of transporting southerly winds was strongly associated with the topographic terrain. Additionally, the rainfall distribution and intensity over south-central China significantly decreased when topography was reduced in the model and were directly affected by wind circulation, which was associated with mountainous terrain that caused strong convection. This study indicates that migrating populations of S. furcifera were carried by the southwesterly low-level jets and that topographically induced convergent winds, precipitation, low temperatures, and wind shear acted as key factors that led to massive landings.

Mechanics of Interrill Erosion with Wind-Driven Rain (WDR)

USDA-ARS?s Scientific Manuscript database

This article provides an evaluation analysis for the performance of the interrill component of the Water Erosion Prediction Project (WEPP) model for Wind-Driven Rain (WDR) events. The interrill delivery rates (Di) were collected in the wind tunnel rainfall simulator facility of the International Cen...

Variability of the recent climate of eastern Africa

NASA Astrophysics Data System (ADS)

Schreck, Carl J., III; Semazzi, Fredrick H. M.

2004-05-01

The primary objective of this study is to investigate the recent variability of the eastern African climate. The region of interest is also known as the Greater Horn of Africa (GHA), and comprises the countries of Burundi, Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia, Sudan, Uganda, and Tanzania.The analysis was based primarily on the construction of empirical orthogonal functions (EOFs) of gauge rainfall data and on CPC Merged Analysis of Precipitation (CMAP) data, derived from a combination of rain-gauge observations and satellite estimates. The investigation is based on the period 1961-2001 for the short rains season of eastern Africa of October through to December. The EOF analysis was supplemented by projection of National Centers for Environmental Prediction wind data onto the rainfall eigenmodes to understand the rainfall-circulation relationships. Furthermore, correlation and composite analyses have been performed with the Climatic Research Unit globally averaged surface-temperature time series to explore the potential relationship between the climate of eastern Africa and global warming.The most dominant mode of variability (EOF1) based on CMAP data over eastern Africa corresponds to El Niño-southern oscillation (ENSO) climate variability. It is associated with above-normal rainfall amounts during the short rains throughout the entire region, except for Sudan. The corresponding anomalous low-level circulation is dominated by easterly inflow from the Indian Ocean, and to a lesser extent the Congo tropical rain forest, into the positive rainfall anomaly region that extends across most of eastern Africa. The easterly inflow into eastern Africa is part of diffluent outflow from the maritime continent during the warm ENSO events. The second eastern African EOF (trend mode) is associated with decadal variability. In distinct contrast from the ENSO mode pattern, the trend mode is characterized by positive rainfall anomalies over the northern sector of eastern Africa and opposite conditions over the southern sector. This rainfall trend mode eluded detection in previous studies that did not include recent decades of data, because the signal was still relatively weak. The wind projection onto this mode indicates that the primary flow that feeds the positive anomaly region over the northern part of eastern Africa emanates primarily from the rainfall-deficient southern region of eastern Africa and Sudan. Although we do not assign attribution of the trend mode to global warming (in part because of the relatively short period of analysis), the evidence, based on our results and previous studies, strongly suggests a potential connection.

Indian Monsoon Depression: Climatology and Variability

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

Yoon, Jin-Ho; Huang, Wan-Ru

The monsoon climate is traditionally characterized by large seasonal rainfall and reversal of wind direction (e.g., Krishnamurti 1979). Most importantly this rainfall is the major source of fresh water to various human activities such as agriculture. The Indian subcontinent resides at the core of the Southeast Asian summer monsoon system, with the monsoon trough extended from northern India across Indochina to the Western Tropical Pacific (WTP). Large fraction of annual rainfall occurs during the summer monsoon season, i.e., June - August with two distinct maxima. One is located over the Bay of Bengal with rainfall extending northwestward into eastern andmore » central India, and the other along the west coast of India where the lower level moist wind meets the Western Ghat Mountains (Saha and Bavardeckar 1976). The rest of the Indian subcontinent receives relatively less rainfall. Various weather systems such as tropical cyclones and weak disturbances contribute to monsoon rainfall (Ramage 1971). Among these systems, the most efficient rain-producing system is known as the Indian monsoon depression (hereafter MD). This MD is critical for monsoon rainfall because: (i) it occurs about six times during each summer monsoon season, (ii) it propagates deeply into the continent and produces large amounts of rainfall along its track, and (iii) about half of the monsoon rainfall is contributed to by the MDs (e.g., Krishnamurti 1979). Therefore, understanding various properties of the MD is a key towards comprehending the veracity of the Indian summer monsoon and especially its hydrological process.« less

Tropical warm pool rainfall variability and impact on upper ocean variability throughout the Madden-Julian oscillation

NASA Astrophysics Data System (ADS)

Thompson, Elizabeth J.

Heating and rain freshening often stabilize the upper tropical ocean, bringing the ocean mixed layer depth to the sea surface. Thin mixed layer depths concentrate subsequent fluxes of heat, momentum, and freshwater in a thin layer. Rapid heating and cooling of the tropical sea surface is important for controlling or triggering atmospheric convection. Ocean mixed layer depth and SST variability due to rainfall events have not been as comprehensively explored as the ocean's response to heating or momentum fluxes, but are very important to understand in the tropical warm pool where precipitation exceeds evaporation and many climate phenomena such as ENSO and the MJO (Madden Julian Oscillation) originate. The first part of the dissertation investigates tropical, oceanic convective and stratiform rainfall variability and determines how to most accurately estimate rainfall accumulation with radar from each rain type. The second, main part of the dissertation uses central Indian Ocean salinity and temperature microstructure measurements and surrounding radar-derived rainfall maps throughout two DYNAMO MJO events to determine the impact of precipitating systems on upper-ocean mixed layer depth and resulting SST variability. The ocean mixed layer was as shallow as 0-5 m during 528/1071 observation hours throughout 2 MJOs (54% of the data record). Out of 43 observation days, thirty-eight near-surface mixed layer depth events were attributed to freshwater stabilization, called rain-formed mixed layers (RFLs). Thirty other mixed layer stratification events were classified as diurnal warm layers (DWLs) due to stable temperature stratification by daytime heating. RFLs and DWLs were observed to interact in two ways: 1) RFLs fill preexisting DWLs and add to total near-surface mixed layer stratification, which occurred ten times; 2) RFLs last long enough to heat, creating a new DWL on top of the RFL, which happened nine times. These combination stratification events were responsible for the highest SST warming rates and some of the highest SSTs leading up to the most active precipitation and wind stage of the each MJO. DWLs without RFL interaction helped produce the highest SSTs in suppressed MJO conditions. As storm intensity, frequency, duration, and the ability of storms to maintain stratiform rain areas increased, RFLS became more common in the disturbed and active MJO phases. Along with the barrier layer, DWL and RFL stratification events helped suppress wind-mixing, cooling, and mixed layer deepening throughout the MJO. We hypothesize that both salinity and temperature stratification events, and their interactions, are important for controlling SST variability and therefore MJO initiation in the Indian Ocean. Most RFLs were caused by submesoscale and mesoscale convective systems with stratiform rain components and local rain accumulations above 10 mm but with winds mostly below 8 m s-1. We hypothesize that the stratiform rain components of storms helped stratify the ocean by providing weak but widespread, steady, long-lived freshwater fluxes. Although generally limited to rain rates ≤ 10 mm hr-1, it is demonstrated that stratiform rain can exert a strong buoyancy flux into the ocean, i.e. as high as maximum daytime solar heating. Storm morphology and the preexisting vertical structure of ocean stability were critical in determining ocean mixed layer depth variability in the presence of rain. Therefore, we suggest that high spatial and temporal resolution coupled ocean-atmosphere models that can parameterize or resolve storm morphology as well as ocean mixed layer and barrier layer evolution are needed to reproduce the diurnal and intraseasonal SST variability documented throughout the MJO.

Numerical simulation of mesoscale surface pressure features with trailing stratiform squall lines using WRF -ARW model over Gangetic West Bengal region

NASA Astrophysics Data System (ADS)

Dawn, Soma; Satyanarayana, A. N. V.

2018-01-01

In the present study, an attempt has been made to investigate the simulation of mesoscale surface pressure patterns like pre-squall mesolow, mesohigh and wake low associated with leading convective line-trailing stratiform (TS) squall lines over Gangetic West Bengal (GWB). For this purpose, a two way interactive triple nested domain with high resolution WRF model having2 km grid length in the innermost domain is used. The model simulated results are compared with the available in-situ observations obtained as a part of Severe Thunderstorm: Observations and Regional Modeling (STORM) programme, reflectivity products of Doppler Weather Radar (DWR) Kolkata and TRMM rainfall. Three TS squall lines (15 May 2009, 5 May 2010 and 7 May 2010) are chosen during pre-monsoon thunderstorm season for this study. The model simulated results of diurnal variation of temperature, relative humidity, wind speed and direction at the station Kharagpur in GWB region reveal a sudden fall in temperature, increase in the amount of relative humidity and sudden rise in wind speed during the arrival of the storms. Such results are well comparable with the observations though there are some leading or lagging of time in respect of actual occurrences of such events. The study indicates that the model is able to predict the occurrences of three typical surface pressure features namely: pre-squall mesolow, meso high and wake low. The predicted surface parameters like accumulated rainfall, maximum reflectivity and vertical profiles (temperature, relative humidity and winds) are well accorded with the observations. The convective and stratiform precipitation region of the TS squall lines are well represented by the model. A strong downdraft is observed to be a contributory factor for formation of mesohigh in the convective region of the squall line. Wake low is observed to reside in the stratiform rain region and the descending dry air at this place has triggered the wake low through adiabatic warming. This study has established the usefulness of the high resolution model in predicting trailing stratiform squall lines and its associated features over the study region.

Observed Recent Trends in Tropical Cyclone Rainfall Over Major Ocean Basins

NASA Technical Reports Server (NTRS)

Lau, K. M.; Zhou, Y. P.

2011-01-01

In this study, we use Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Climatology Project (GPCP) rainfall data together with historical storm track records to examine the trend of tropical cyclone (TC) rainfall in major ocean basins during recent decades (1980-2007). We find that accumulated total rainfall along storm tracks for all tropical cyclones shows a weak positive trend over the whole tropics. However, total rainfall associated with weak storms, and intense storms (Category 4-5) both show significant positive trends, while total rainfall associated with intermediate storms (Category1-3) show a significant negative trend. Storm intensity defined as total rain produced per unit storm also shows increasing trend for all storm types. Basin-wide, from the first half (1980-1993) to the second half (1994-2007) of the data period, the North Atlantic shows the pronounced increase in TC number and TC rainfall while the Northeast Pacific shows a significant decrease in all storm types. Except for the Northeast Pacific, all other major basins (North Atlantic, Northwest Pacific, Southern Oceans, and Northern Indian Ocean) show a significant increase in total number and rainfall amount in Category 4-5 storms. Overall, trends in TC rainfall in different ocean basins are consistent with long-term changes in the ambient large-scale environment, including SST, vertical wind shear, sea level pressure, mid-tropospheric humidity, and Maximum Potential Intensity (MPI). Notably the pronounced positive (negative) trend of TC rainfall in the North Atlantic (Northeast Pacific) appears to be related to the most (least) rapid increase in SST and MPI, and the largest decrease (increase) in vertical wind shear in the region, relative to other ocean basins.

The weekly associations between climatic factors and Plasmodium vivax and Plasmodium falciparum malaria in China, 2005-2014.

PubMed

Hundessa, Samuel; Williams, Gail; Li, Shanshan; Guo, Jinpeng; Zhang, Wenyi; Guo, Yuming

2017-05-01

Meteorological factors play a crucial role in malaria transmission, but limited evidence is available from China. This study aimed to estimate the weekly associations between meteorological factors and Plasmodium vivax and Plasmodium falciparum malaria in China. The Distributed Lag Non-Linear Model was used to examine non-linearity and delayed effects of average temperature, rainfall, relative humidity, sunshine hours, wind speed and atmospheric pressure on malaria. Average temperature was associated with P. vivax and P. falciparum cases over long ranges of lags. The effect was more immediate on P. vivax (0-6 weeks) than on P. falciparum (1-9 weeks). Relative humidity was associated with P. vivax and P. falciparum over 8-10 weeks and 5-8 weeks lag, respectively. A significant effect of wind speed on P. vivax was observed at 0-2 weeks lag, but no association was found with P. falciparum. Rainfall had a decreasing effect on P. vivax, but no association was found with P. falciparum. Sunshine hours were negatively associated with P. falciparum, but the association was unclear for P. vixax. However, the effects of atmospheric pressure on both malaria types were not significant at any lag. Our study highlights a substantial effect of weekly climatic factors on P. vivax and P. falciparum malaria transmission in China, with different lags. This provides an evidence base for health authorities in developing a malaria early-warning system. © The Author 2017. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

The Impacts of Amazon Deforestation on Pacific Climate

NASA Astrophysics Data System (ADS)

Lindsey, Leah

Variability in eastern Pacific sea surface temperatures (SSTs) associated with the El Nino Southern Oscillation are known to affect Amazonian precipitation, but to what extent do changing Amazonian vegetation and rainfall impact eastern Pacific SST? The Amazon rainforest is threatened by many factors including climate change and clearing for agricultural reasons. Forest fires and dieback are more likely due to increased frequency and intensity of droughts in the region. It is possible that extensive Amazon deforestation can enhance El Nino conditions by weakening the Walker circulation. Correlations between annual rainfall rates over the Amazon and other atmospheric parameters (global precipitation, surface air temperature, low cloud amount, 500 hPa vertical velocity, surface winds, and 200 hPa winds) over the eastern Pacific indicate strong relationships among these fields. Maps of these correlations (teleconnection maps) reveal that when the Amazon is rainy SSTs in the central and eastern Pacific are cold, rainfall is suppressed over the central and eastern Pacific, low clouds are prominent over the eastern and southeastern Pacific, and subsidence over the central and eastern Pacific is enhanced. Precipitation in the Amazon is also consistent with a strong Walker circulation (La Nina conditions), manifest as strong correlations with the easterly surface and westerly 200 hPa zonal winds. Coupling between Amazon rainfall and these fields are seen in observations and model data. Correlations were calculated using data from observations, reanalysis data, two models under the Coupled Model Intercomparison Project/Atmospheric Model Intercomparison Project (CMIP5/AMIP), and an AMIP run with the model used in this study, the Community Earth System Model (CESM1.1.1). Although the correlations between Amazon precipitation and the aforementioned fields are strong, they do not show causality. In order to investigate the impact of tropical South American deforestation on the Pacific climate, numerical experiments were performed using the CESM. Amazon deforestation was studied in an idealized world where a single continent was covered in forest and then, in a separate simulation, covered in grassland. Four different sets of simulations were carried out: 1) the baseline idealized set-up with prescribed SST, 2) another with an Andes-like mountain range, 3) a simulation with a slab ocean model rather than prescribed SST, and 4) a simulation repeated with the standard Community Atmosphere Model (CAM4) replaced by the Superparameterized version (SP-CAM). The continent in these simulations was compared to the Amazon, and the ocean to the west of the continent was compared to the eastern Pacific. All of the simulations showed a strong warming of around 3-4°C over the continent going from forest to grassland. A notable decrease in precipitation over land of about 1-3 mm day-1 and increase to the west of the continent of about 1-2 mm day-1 was also observed in most of the simulations. The simulations with the slab ocean model showed enhanced precipitation changes with a corresponding decrease of 2-4 mm day-1 over land and increase of 3-5 mm day-1 west of the continent. Simulations that used the SP-CAM showed very small changes in precipitation, which was likely due to the decreased spin-up time allowed for these simulations. The decrease in the surface roughness and reduction in the evapotranspiration for the simulations with grassland contributed to these changes in surface temperature and precipitation. The conversion of forest to grassland in our experiments imply that deforestation can lead to weakening of the Walker circulation by weakening easterly surface winds and westerly upper tropospheric winds. These findings suggest that large-scale Amazon deforestation is capable of enhancing El Nino conditions.

Frequency of extreme Sahelian storms tripled since 1982 in satellite observations.

PubMed

Taylor, Christopher M; Belušić, Danijel; Guichard, Françoise; Parker, Douglas J; Vischel, Théo; Bock, Olivier; Harris, Phil P; Janicot, Serge; Klein, Cornelia; Panthou, Gérémy

2017-04-26

The hydrological cycle is expected to intensify under global warming, with studies reporting more frequent extreme rain events in many regions of the world, and predicting increases in future flood frequency. Such early, predominantly mid-latitude observations are essential because of shortcomings within climate models in their depiction of convective rainfall. A globally important group of intense storms-mesoscale convective systems (MCSs)-poses a particular challenge, because they organize dynamically on spatial scales that cannot be resolved by conventional climate models. Here, we use 35 years of satellite observations from the West African Sahel to reveal a persistent increase in the frequency of the most intense MCSs. Sahelian storms are some of the most powerful on the planet, and rain gauges in this region have recorded a rise in 'extreme' daily rainfall totals. We find that intense MCS frequency is only weakly related to the multidecadal recovery of Sahel annual rainfall, but is highly correlated with global land temperatures. Analysis of trends across Africa reveals that MCS intensification is limited to a narrow band south of the Sahara desert. During this period, wet-season Sahelian temperatures have not risen, ruling out the possibility that rainfall has intensified in response to locally warmer conditions. On the other hand, the meridional temperature gradient spanning the Sahel has increased in recent decades, consistent with anthropogenic forcing driving enhanced Saharan warming. We argue that Saharan warming intensifies convection within Sahelian MCSs through increased wind shear and changes to the Saharan air layer. The meridional gradient is projected to strengthen throughout the twenty-first century, suggesting that the Sahel will experience particularly marked increases in extreme rain. The remarkably rapid intensification of Sahelian MCSs since the 1980s sheds new light on the response of organized tropical convection to global warming, and challenges conventional projections made by general circulation models.

Varying Influence of Different Forcings on the Indo-Pacific Warm Pool Climate

NASA Astrophysics Data System (ADS)

Mohtadi, M.; Huang, E.; Hollstein, M.; Chen, Y.; Schefuß, E.; Rosenthal, Y.; Prange, M.; Oppo, D.; Liu, J.; Steinke, S.; Martinez-Mendez, G.; Tian, J.; Moffa-Sanchez, P.; Lückge, A.

2017-12-01

Proxy records of rainfall in marine archives from the eastern and western parts of the Indo-Pacific Warm Pool (IPWP) vary at precessional band and suggest a dominant role of orbital forcing by modulating monsoon rainfall and the position of the Inter Tropical Convergence Zone. Rainfall changes recorded in marine archives from the northern South China Sea reveal a more complex history. They are largely consistent with those recorded in the Chinese cave speleothems during glacial periods, but show opposite changes during interglacial peaks that coincide with strong Northern Hemisphere summer insolation maxima. During glacial periods, the establishment of massive Northern Hemisphere ice sheets and the exposure of broad continental shelves in East and Southeast Asia alter the large-scale routes and amounts of water vapor transport onto land relative to interglacials. Precipitation over China during glacials varies at precessional band and is dominated by water vapor transport from the nearby tropical and northwest Pacific, resulting in consistent changes in precipitation over large areas. In the absence of ice forcing during peak interglacials with a strong summer insolation, the low-level southerly monsoonal winds mainly of the Indian Ocean origin penetrate further landward and rainout along their path over China. Subsurface temperatures from the IPWP lack changes on glacial-interglacial timescales but follow the obliquity cycle, and suggest that obliquity-paced climate variations at mid-latitudes remotely control subsurface temperatures in the IPWP. Temperature and rainfall in the IPWP respond primarily to abrupt climate changes in the North Atlantic on millennial timescales, and to ENSO and solar forcing on interannual to decadal timescales. In summary, results from marine records reveal that the IPWP climate is sensitive to changes in spatial and temporal distribution of heat by many types of forcing, the influence of which seems to vary in time and space.

Evaluation of empirical relationships between extreme rainfall and daily maximum temperature in Australia

NASA Astrophysics Data System (ADS)

Herath, Sujeewa Malwila; Sarukkalige, Ranjan; Nguyen, Van Thanh Van

2018-01-01

Understanding the relationships between extreme daily and sub-daily rainfall events and their governing factors is important in order to analyse the properties of extreme rainfall events in a changing climate. Atmospheric temperature is one of the dominant climate variables which has a strong relationship with extreme rainfall events. In this study, a temperature-rainfall binning technique is used to evaluate the dependency of extreme rainfall on daily maximum temperature. The Clausius-Clapeyron (C-C) relation was found to describe the relationship between daily maximum temperature and a range of rainfall durations from 6 min up to 24 h for seven Australian weather stations, the stations being located in Adelaide, Brisbane, Canberra, Darwin, Melbourne, Perth and Sydney. The analysis shows that the rainfall - temperature scaling varies with location, temperature and rainfall duration. The Darwin Airport station shows a negative scaling relationship, while the other six stations show a positive relationship. To identify the trend in scaling relationship over time the same analysis is conducted using data covering 10 year periods. Results indicate that the dependency of extreme rainfall on temperature also varies with the analysis period. Further, this dependency shows an increasing trend for more extreme short duration rainfall and a decreasing trend for average long duration rainfall events at most stations. Seasonal variations of the scale changing trends were analysed by categorizing the summer and autumn seasons in one group and the winter and spring seasons in another group. Most of 99th percentile of 6 min, 1 h and 24 h rain durations at Perth, Melbourne and Sydney stations show increasing trend for both groups while Adelaide and Darwin show decreasing trend. Furthermore, majority of scaling trend of 50th percentile are decreasing for both groups.

Urticaceae pollen concentration in the atmosphere of North Western Spain.

PubMed

Vega-Maray, Ana Maria; Valencia-Barrera, Rosa; Fernandez-Gonzalez, Delia; Fraile, Roberto

2003-01-01

Plants of the Urticaceae family can develop into a pest on soils enriched with nitrogen. Urticaceae pollen is a biohazard because it elicits severe pollinosis. Pollen grains were sampled by using a Lanzoni seven-day-recording trap from February 1995-December 2000 in the atmosphere of the city of Ponferrada (Leon, North Western Spain). The Spearman test was used to analyse the statistical correlation between Urticaceae pollen and certain meteorological factors in different main pollination periods. Maximum values are reached in June and July, minimum levels are recorded in January and December. The parameters bearing the greatest positive influence on the occurrence of Urticaceae pollen grains are: temperature (maximum, minimum and mean), humidity (absolute, wet-bulb temperature, dew point and mixing ratio) and south western wind direction; negative parameters are: relative humidity, rainfall and period without wind. The highest correlation coefficients were obtained with temperature and wet-bulb. Absolute humidity and wet-bulb temperature yielded better correlation than relative humidity; hence, these two parameters must be included in this type of study. The use of one main pollination period or another in statistical analysis has an influence on the coefficient value. The behaviour of the pollen grains in the atmosphere during the year also influences the results.

Secure Automated Microgrid Energy System (SAMES)

DTIC Science & Technology

2016-12-01

with embedded algorithm to share power between each other; • Wind Turbine (WT) Simulator, max 80 kW (4×20 kW), 480 V, Running Wind Generation...Temp, Rain, Wind ........................ 39 Figure 22. Point Loma, Box and Whisker Plot, Hourly Sum of Consumption ............................ 40...Figure 27. Coronado, Consumption vs Average Daily SD Temp, Rainfall, Wind ....................... 44 Figure 28. Naval Base Point Loma, One Line, Solar

Analysis of Impact of Tropical Cyclone Blance on Rainfall at Kupang Region Based on Atmospheric Condition and Satellite Imagery

NASA Astrophysics Data System (ADS)

Roguna, S.; Saragih, I. J. A.; Siregar, P. S.; Julius, A. M.

2018-04-01

The Tropical Depression previously identified on March 3, 2017, at Arafuru Sea has grown to Tropical Cyclone Blance on March 5, 2017. The existence of Tropical Cyclone Blance gave impacts like increasing rainfall for some regions in Indonesia until March 7, 2017, such as Kupang. The increase of rainfall cannot be separated from the atmospheric dynamics related to convection processes and the formation of clouds. Analysis of weather parameters is made such as vorticity to observe vertical motion over the study area, vertical velocity to see the speed of lift force in the atmosphere, wind to see patterns of air mass distribution and rainfall to see the increase of rainfall compared to several days before the cyclone. Analysis of satellite imagery data is used as supporting analysis to see clouds imagery and movement direction of the cyclone. The results of weather parameters analysis show strong vorticity and lift force of air mass support the growth of Cumulonimbus clouds, cyclonic patterns on wind streamline and significant increase of rainfall compared to previous days. The results of satellite imagery analysis show the convective clouds over Kupang and surrounding areas when this phenomena and cyclone pattern moved down from Arafuru Sea towards the western part of Australia.

Correlation of spring spore concentrations and meteorological conditions in Tulsa, Oklahoma

NASA Astrophysics Data System (ADS)

Troutt, C.; Levetin, E.

Different spore types are abundant in the atmosphere depending on the weather conditions. Ascospores generally follow precipitation, while spore types such as Alternaria and Cladosporium are abundant in dry conditions. This project attempted to correlate fungal spore concentrations with meteorological data from Tulsa, Oklahoma during May 1998 and May 1999. Air samples were collected and analyzed by the 12-traverse method. The spore types included were Cladosporium, Alternaria, Epicoccum, Curvularia, Pithomyces, Drechslera, smut spores, ascospores, basidiospores, and other spores. Weather variables included precipitation levels, temperature, dew point, air pressure, wind speed, wind direction and wind gusts. There were over 242.57 mm of rainfall in May 1999 and only 64.01 mm in May 1998. The most abundant spore types during May 1998 and May 1999 were Cladosporium, ascospores, and basidiospores. Results showed that there were significant differences in the dry-air spora between May 1998 and May 1999. There were twice as many Cladosporium in May 1998 as in May 1999; both ascospores and basidiospores showed little change. Multiple regression analysis was used to determine which meteorological variables influenced spore concentrations. Results showed that there was no single model for all spore types. Different combinations of factors were predictors of concentration for the various fungi examined; however, temperature and dew point seemed to be the most important meteorological factors.

Observed changes in extremes of daily rainfall and temperature in Jemma Sub-Basin, Upper Blue Nile Basin, Ethiopia

NASA Astrophysics Data System (ADS)

Worku, Gebrekidan; Teferi, Ermias; Bantider, Amare; Dile, Yihun T.

2018-02-01

Climate variability has been a threat to the socio-economic development of Ethiopia. This paper examined the changes in rainfall, minimum, and maximum temperature extremes of Jemma Sub-Basin of the Upper Blue Nile Basin for the period of 1981 to 2014. The nonparametric Mann-Kendall, seasonal Mann-Kendall, and Sen's slope estimator were used to estimate annual trends. Ten rainfall and 12 temperature indices were used to study changes in rainfall and temperature extremes. The results showed an increasing trend of annual and summer rainfall in more than 78% of the stations and a decreasing trend of spring rainfall in most of the stations. An increase in rainfall extreme events was detected in the majority of the stations. Several rainfall extreme indices showed wetting trends in the sub-basin, whereas limited indices indicated dryness in most of the stations. Annual maximum and minimum temperature and extreme temperature indices showed warming trend in the sub-basin. Presence of extreme rainfall and a warming trend of extreme temperature indices may suggest signs of climate change in the Jemma Sub-Basin. This study, therefore, recommended the need for exploring climate induced risks and implementing appropriate climate change adaptation and mitigation strategies.

Blow me down: A new perspective on Aloe dichotoma mortality from windthrow

PubMed Central

2014-01-01

Background Windthrow, the uprooting of trees during storms associated with strong winds, is a well-established cause of mortality in temperate regions of the world, often with large ecological consequences. However, this phenomenon has received little attention within arid regions and is not well documented in southern Africa. Slow rates of post-disturbance recovery and projected increases in extreme weather events in arid areas mean that windthrow could be more common and have bigger impacts on these ecosystems in the future. This is of concern due to slow rates of post-disturbance recovery in arid systems and projected increases in extreme weather events in these areas. This study investigated the spatial pattern, magnitude and likely causes of windthrown mortality in relation to other forms of mortality in Aloe dichotoma, an iconic arid-adapted arborescent succulent and southern Africa climate change indicator species. Results We found that windthrown mortality was greatest within the equatorward summer rainfall zone (SRZ) of its distribution (mean = 31%, n = 11), and was derived almost exclusively from the larger adult age class. A logistic modelling exercise indicated that windthrown mortality was strongly associated with greater amounts of warm season (summer) rainfall in the SRZ, higher wind speeds, and leptosols. A statistically significant interaction term between higher summer rainfall and wind speeds further increased the odds of being windthrown. While these results would benefit from improvements in the resolution of wind and substrate data, they do support the hypothesised mechanism for windthrow in A. dichotoma. This involves powerful storm gusts associated with either the current or subsequent rainfall event, heavy convective rainfall, and an associated increase in soil malleability. Shallow rooting depths in gravel-rich soils and an inflexible, top-heavy canopy structure make individuals especially prone to windthrown mortality during storms. Conclusions Results highlight the importance of this previously unrecognised form of mortality in A. dichotoma, especially since it seems to disproportionately affect reproductively mature adult individuals in an infrequently recruiting species. Smaller, more geographically isolated and adult dominated populations in the summer rainfall zone are likely to be more vulnerable to localised extinction due to windthrow events. PMID:24641794

Blow me down: a new perspective on Aloe dichotoma mortality from windthrow.

PubMed

Jack, Samuel Linton; Hoffman, Michael Timm; Rohde, Rick Frederick; Durbach, Ian; Archibald, Margaret

2014-03-18

Windthrow, the uprooting of trees during storms associated with strong winds, is a well-established cause of mortality in temperate regions of the world, often with large ecological consequences. However, this phenomenon has received little attention within arid regions and is not well documented in southern Africa. Slow rates of post-disturbance recovery and projected increases in extreme weather events in arid areas mean that windthrow could be more common and have bigger impacts on these ecosystems in the future. This is of concern due to slow rates of post-disturbance recovery in arid systems and projected increases in extreme weather events in these areas. This study investigated the spatial pattern, magnitude and likely causes of windthrown mortality in relation to other forms of mortality in Aloe dichotoma, an iconic arid-adapted arborescent succulent and southern Africa climate change indicator species. We found that windthrown mortality was greatest within the equatorward summer rainfall zone (SRZ) of its distribution (mean = 31%, n = 11), and was derived almost exclusively from the larger adult age class. A logistic modelling exercise indicated that windthrown mortality was strongly associated with greater amounts of warm season (summer) rainfall in the SRZ, higher wind speeds, and leptosols. A statistically significant interaction term between higher summer rainfall and wind speeds further increased the odds of being windthrown. While these results would benefit from improvements in the resolution of wind and substrate data, they do support the hypothesised mechanism for windthrow in A. dichotoma. This involves powerful storm gusts associated with either the current or subsequent rainfall event, heavy convective rainfall, and an associated increase in soil malleability. Shallow rooting depths in gravel-rich soils and an inflexible, top-heavy canopy structure make individuals especially prone to windthrown mortality during storms. Results highlight the importance of this previously unrecognised form of mortality in A. dichotoma, especially since it seems to disproportionately affect reproductively mature adult individuals in an infrequently recruiting species. Smaller, more geographically isolated and adult dominated populations in the summer rainfall zone are likely to be more vulnerable to localised extinction due to windthrow events.

Weathering a Dynamic Seascape: Influences of Wind and Rain on a Seabird’s Year-Round Activity Budgets

PubMed Central

Pistorius, Pierre A.; Hindell, Mark A.; Tremblay, Yann; Rishworth, Gavin M.

2015-01-01

How animals respond to varying environmental conditions is fundamental to ecology and is a question that has gained impetus due to mounting evidence indicating negative effects of global change on biodiversity. Behavioural plasticity is one mechanism that enables individuals and species to deal with environmental changes, yet for many taxa information on behavioural parameters and their capacity to change are lacking or restricted to certain periods within the annual cycle. This is particularly true for seabirds where year-round behavioural information is intrinsically challenging to acquire due to their reliance on the marine environment where they are difficult to study. Using data from over 13,000 foraging trips throughout the annual cycle, acquired using new-generation automated VHF technology, we described sex-specific, year-round activity budgets in Cape gannets. Using these data we investigated the role of weather (wind and rain) on foraging activity and time allocated to nest attendance. Foraging activity was clearly influenced by wind speed, wind direction and rainfall during and outside the breeding season. Generally, strong wind conditions throughout the year resulted in relatively short foraging trips. Birds spent longer periods foraging when rainfall was moderate. Nest attendance, which was sex-specific outside of the breeding season, was also influenced by meteorological conditions. Large amounts of rainfall (> 2.5 mm per hour) and strong winds (> 13 m s-1) resulted in gannets spending shorter amounts of time at their nests. We discuss these findings in terms of life history strategies and implications for the use of seabirds as bio-indicators. PMID:26581108

A methodology for investigating interdependencies between measured throughfall, meteorological variables and canopy structure on a small catchment.

NASA Astrophysics Data System (ADS)

Maurer, Thomas; Gustavos Trujillo Siliézar, Carlos; Oeser, Anne; Pohle, Ina; Hinz, Christoph

2016-04-01

In evolving initial landscapes, vegetation development depends on a variety of feedback effects. One of the less understood feedback loops is the interaction between throughfall and plant canopy development. The amount of throughfall is governed by the characteristics of the vegetation canopy, whereas vegetation pattern evolution may in turn depend on the spatio-temporal distribution of throughfall. Meteorological factors that may influence throughfall, while at the same time interacting with the canopy, are e.g. wind speed, wind direction and rainfall intensity. Our objective is to investigate how throughfall, vegetation canopy and meteorological variables interact in an exemplary eco-hydrological system in its initial development phase, in which the canopy is very heterogeneous and rapidly changing. For that purpose, we developed a methodological approach combining field methods, raster image analysis and multivariate statistics. The research area for this study is the Hühnerwasser ('Chicken Creek') catchment in Lower Lusatia, Brandenburg, Germany, where after eight years of succession, the spatial distribution of plant species is highly heterogeneous, leading to increasingly differentiated throughfall patterns. The constructed 6-ha catchment offers ideal conditions for our study due to the rapidly changing vegetation structure and the availability of complementary monitoring data. Throughfall data were obtained by 50 tipping bucket rain gauges arranged in two transects and connected via a wireless sensor network that cover the predominant vegetation types on the catchment (locust copses, dense sallow thorn bushes and reeds, base herbaceous and medium-rise small-reed vegetation, and open areas covered by moss and lichens). The spatial configuration of the vegetation canopy for each measurement site was described via digital image analysis of hemispheric photographs of the canopy using the ArcGIS Spatial Analyst, GapLight and ImageJ software. Meteorological data from two on-site weather stations (wind direction, wind speed, air temperature, air humidity, insolation, soil temperature, precipitation) were provided by the 'Research Platform Chicken Creek' (https://www.tu-cottbus.de/projekte/en/oekosysteme/startseite.html). Data were combined and multivariate statistical analysis (PCA, cluster analysis, regression trees) were conducted using the R-software to i) obtain statistical indices describing the relevant characteristics of the data and ii) to identify the determining factors for throughfall intensity. The methodology is currently tested and results will be presented. Preliminary evaluation of the image analysis approach showed only marginal, systematic deviation of results for the different software tools applied, which makes the developed workflow a viable tool for canopy characterization. Results from this study will have a broad spectrum of possible applications, for instance the development / calibration of rainfall interception models, the incorporation into eco-hydrological models, or to test the fault tolerance of wireless rainfall sensor networks.

Integrated Assessments of the Impact of Climate Change on Agriculture: An Overview of AgMIP Regional Research in South Asia

NASA Technical Reports Server (NTRS)

McDermid, Sonali P.; Dileepkumar, Guntuku; Murthy, K. M. Dakshina; Nedumaran, S.; Singh, Piara; Srinivasa, Chukka; Gangwar, B.; Subash, N.; Ahmad, Ashfaq; Zubair, Lareef;

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.

An isotope hydrology study of the Kilauea volcano area, Hawaii

USGS Publications Warehouse

Scholl, M.A.; Ingebritsen, S.E.; Janik, C.J.; Kauahikaua, J.P.

1995-01-01

Isotope tracer methods were used to determine flow paths, recharge areas, and relative age for ground water in the Kilauea volcano area on the Island of Hawaii. Stable isotopes in rainfall show three distinct isotopic gradients with elevation, which are correlated with trade-wind, rain shadow, and high-elevation climatological patterns. Temporal variations in isotopic composition of precipitation are controlled more by the frequency of large storms than b.y seasonal temperature fluctuations. Consistency in results between two separate areas with rainfall caused by tradewinds and thermally-driven upslope airflow suggests that isotopic gradients with elevation may be similar on other islands in the tradewind belt, especially the other Hawaiian Islands, which have similar climatology and temperature lapse rates. Areal contrasts in ground-water stable isotopes and tritium indicate that the volcanic ri~ zones compartmentalize the regional ground-water system. Tritium levels in ground water within and downgradient of Kilauea's ri~ zones indicate relatively long residence times. Part of Kilauea's Southwest Ri~ Zone appears to act as a conduit for water from higher elevation, but there is no evidence for extensive down-ri~ flow in the lower East Ri~ Zone.

Observational Analysis of Two Contrasting Monsoon Years

NASA Astrophysics Data System (ADS)

Karri, S.; Ahmad, R.; Sujata, P.; Jose, S.; Sreenivas, G.; Maurya, D. K.

2014-11-01

The Indian summer monsoon rainfall contributes about 75 % of the total annual rainfall and exhibits considerable interannual variations. The agricultural economy of the country depends mainly on the monsoon rainfall. The long-range forecast of the monsoon rainfall is, therefore of significant importance in agricultural planning and other economic activities of the country. There are various parameters which influence the amount of rainfall received during the monsoon. Some of the important parameters considered by the Indian Meteorological Department (IMD) for the study of monsoon are Outgoing Longwave Radiation (OLR), moisture content of the atmosphere, zonal wind speed, low level vorticity, pressure gradient etc. Compared to the Long Period Average (LPA) value of rain fall, the country as a whole received higher amount of rainfall in June, 2013 (34 % more than LPA). The same month showed considerable decrease next year as the amount of rainfall received was around 43 % less compared to LPA. This drastic difference of monsoon prompted to study the behaviour of some of the monsoon relevant parameters. In this study we have considered five atmospheric parameters as the indicators of monsoon behaviour namely vertical relative humidity, OLR, aerosol optical depth (AOD), wind at 850 hPa and mean sea level pressure (MSLP). In the initial analysis of weekly OLR difference for year 2013 and 2014 shows positive values in the month of May over north-western parts of India (region of heat low). This should result in a weaker monsoon in 2014. This is substantiated by the rainfall data received for various stations over India. Inference made based on the analysis of RH profiles coupled with AOD values is in agreement with the rainfall over the corresponding stations.

Meteorological conditions for the triggering of landslides in Asturias (NW Spain). A preliminary analysis of synoptic patterns.

NASA Astrophysics Data System (ADS)

Valenzuela, Pablo; Iglesias, Miguel; José Domínguez-Cuesta, María; Mora García, Manuel Antonio

2017-04-01

Asturias is one of the most landslide prone areas in the NW of Spain, where those phenomena cause every year large economic loses and sometimes personal injuries or fatalities. Most of landslides take place during intense rainfall events, which point out precipitation as the main triggering factor. Regional climate is characterized by average annual precipitation and temperature of 960 mm and 13.3°C respectively. Rainfall distribution throughout the year allows the definition of a humid period between October and May, characterized by the succession of frontal systems, and a considerable dry period between June and September, when heavy short storm episodes are usual. BAPA landslide database (http://geol.uniovi.es/BAPA) gathers more than 500 landslide records located with high temporal reliability for eight hydrological years between October 2008 and September 2016. Eight periods with a high concentration of landslides and significant precipitation records have been selected for the study within this time span. Meteorological conditions which took place during each period have been characterized by using data from the National Oceanic and Atmospheric Administration of the EEUU (NCAR/NCEP Reanalysis 1) through the free software Grid Analysis and Display System (GrADS). Seven parameters have been used to characterize each synoptic situation: (i) 500 hPa temperature, (ii) 500 hPa geopotential height, (iii) 850 hPa temperature, (iv) 850 hPa geopotential height, (v) 925hPa wind, (vi) specific humidity, and (vii) sea level pressure. The final goal is to establish a conceptual model of the most frequent synoptic meteorological patterns which generate rainfall-triggered landslide events in Asturias during the humid and dry periods.

Multiproxy Reduced-Dimension Reconstruction of Holocene Tropical Pacific SST Fields and Indian Monsoon Variability

NASA Astrophysics Data System (ADS)

Gill, E.; Rajagopalan, B.; Molnar, P. H.; Marchitto, T. M., Jr.; Kushnir, Y.

2016-12-01

We develop a multiproxy reduced-dimension methodology that blends magnesium calcium (Mg/Ca) and alkenone (UK'37) paleo sea surface temperature (SST) records from the eastern and western equatorial Pacific to recreate snapshots of full field SSTs and zonal wind anomalies from 10 to 2 ka BP in 2000-year increments. In the reconstruction, the zonal SST difference (average west Pacific SST minus average east Pacific SST) is largest at 10 ka (0.26°C), with coldest SST anomalies of -0.9°C in the eastern equatorial Pacific and concurrent easterly maximum zonal wind anomalies of 7 m s-1 throughout the central Pacific. From 10 to 2 ka, the entire equatorial Pacific warms, but at a faster rate in the east than in the west. These patterns are broadly consistent with previous inferences of reduced El Niño-Southern Oscillation variability associated with a cooler and/or "La Niña-like" state during the early to middle Holocene. At present there is a strong negative correlation between tropical pacific SSTs and Indian summer monsoon strength. Assuming ENSO-monsoon teleconnections were the same during early Holocene, we would expect a cooler tropical Pacific to enhance the summer Indian monsoon. To test this idea, we used the same tropical Pacific SST proxy records and a similar reduced-dimension technique to reconstruct fields of Arabian Sea wind-stress curl and Indian summer monsoon precipitation. Reconstructions for 10 ka reveal wind-stress curl anomalies of 30% greater than present day off the coastlines of Oman and Yemen, which suggest greater coastal upwelling and an enhanced monsoon jet during this time. Spatial rainfall reconstructions reveal the greatest difference in precipitation at 10 ka over the core monsoon region ( 20-60% greater than present day). Specifically, reconstructions from 10 ka reveal 40-60% greater rainfall over North West India, a region home to abundant paleo-lake records spanning the Holocene but is at present remarkably dry ( 200-450 mm of annual rainfall). These findings advance the hypothesis that teleconnections from the tropical Pacific contributed to, if not accounted for, greater early to middle Holocene wetness over India as recorded by various (e.g., cave, lacustrine, river discharge) paleoclimate proxies throughout the monsoon region.

The influence of climate, topography and land-use on the hydrology of ephemeral upland catchments

NASA Astrophysics Data System (ADS)

Daly, E.; Webb, J.; Dresel, E.

2016-12-01

We report on an on-going project aimed at determining the effects of climate variability and land use change on water resources in ephemeral productive catchments. Meteorological data (including rainfall, solar radiation, air temperature, humidity and wind speed), streamflow and groundwater levels were collected continuously for over five years in seven ephemeral catchments in southeastern Australia. The catchments, dominated by either pasture for grazing (four) or Eucalyptus globulus (blue gum) plantations of different ages (three), were located in three different geological settings. Rainfall varied from higher than the long-term average of this area for the initial years of the study period to much drier than the long-term average for the last two years. Groundwater levels in the farm sites remained stable or slightly increased through the study period, while levels declined in all the plantation catchments, where evapotranspiration rates were greater than rainfall. The trees intercept groundwater recharge and in some areas of the catchments directly access groundwater. Streamflow occurred mainly during winter, with short-term flows in summer caused by sporadic large rainfall events. Despite the large annual rainfall variability, flow rates in each year were similar in most catchments, with the duration of flow being important in determining the annual flow. The frequency rather than the amount of rainfall events determines the generation of streamflow in the two catchments with steeper slopes. The effect of the tree plantations on streamflow varied from a substantial reduction in one catchment to no effect in another, where the tree rows are oriented predominantly downslope, allowing greater runoff. In the third plantation catchment, geology is the main driver of runoff due to capture into underlying karst conduits.

Intrinsic Coupled Ocean-Atmosphere Modes of the Asian Summer Monsoon: A Re-assessment of Monsoon-ENSO Relationships

NASA Technical Reports Server (NTRS)

Lau, K.-M.; Wu, H. T.

2000-01-01

Using global rainfall and sea surface temperature (SST) data for the past two decades (1979-1998), we have investigated the intrinsic modes of Asian summer monsoon (ASM) and ENSO co-variability. Three recurring ASM rainfall-SST coupled modes were identified. The first is a basin scale mode that features SST and rainfall variability over the entire tropics (including the ASM region), identifiable with those occurring during El Nino or La Nina. This mode is further characterized by a pronounced biennial variation in ASM rainfall and SST associated with fluctuations of the anomalous Walker circulation that occur during El Nino/La Nina transitions. The second mode comprises mixed regional and basin-scale rainfall and SST signals, with pronounced intraseasonal and interannual variabilities. This mode features a SST pattern associated with a developing La Nina, with a pronounced low level anticyclone in the subtropics of the western Pacific off the coast of East Asia. The third mode depicts an east-west rainfall and SST dipole across the southern equatorial Indian Ocean, most likely stemming from coupled ocean-atmosphere processes within the ASM region. This mode also possesses a decadal time scale and a linear trend, which are not associated with El Nino/La Nina variability. Possible causes of year-to-year rainfall variability over the ASM and sub-regions have been evaluated from a reconstruction of the observed rainfall from singular eigenvectors of the coupled modes. It is found that while basin-scale SST can account for portions of ASM rainfall variability during ENSO events (up to 60% in 1998), regional processes can accounts up to 20-25% of the rainfall variability in typical non-ENSO years. Stronger monsoon-ENSO relationship tends to occur in the boreal summer immediately preceding a pronounced La Nina, i.e., 1998, 1988 and 1983. Based on these results, we discuss the possible impacts of the ASM on ENSO variability via the west Pacific anticyclone and articulate a hypothesis that anomalous wind forcings derived from the anticyclone may be instrumental in inducing a strong biennial modulation to natural ENSO cycles.

Ecogeomorphology of Sand Dunes Shaped by Vegetation

NASA Astrophysics Data System (ADS)

Tsoar, H.

2014-12-01

Two dune types associated with vegetation are known: Parabolic and Vegetated Linear Dunes (VLDs), the latters are the dominant dune type in the world deserts. Parabolic dunes are formed in humid, sub-humid and semi-arid environments (rather than arid) where vegetation is nearby. VLDs are known today in semiarid and arid lands where the average yearly rainfall is ≥100 mm, enough to support sparse cover of vegetation. These two dune types are formed by unidirectional winds although they demonstrate a different form and have a distinct dynamics. Conceptual and mathematical models of dunes mobility and stability, based on three control parameters: wind power (DP), average annual precipitation (p), and the human impact parameter (μ) show that where human impact is negligible the effect of wind power (DP) on vegetative cover is substantial. The average yearly rainfall of 60-80 mm is the threshold of annual average rainfall for vegetation growth on dune sand. The model is shown to follow a hysteresis path, which explains the bistability of active and stabilized dunes under the same climatic conditions with respect to wind power. We have discerned formation of parabolic dunes from barchans and transverse dunes in the coastal plain of Israel where a decrease in human activity during the second half of the 20th century caused establishment of vegetation on the crest of the dunes, a process that changed the dynamics of these barchans and transverse dunes and led to a change in the shape of the windward slope from convex to concave. These dunes gradually became parabolic. It seems that VLDs in Australia or the Kalahari have always been vegetated to some degree, though the shrubs were sparser in colder periods when the aeolian erosion was sizeable. Those ancient conditions are characterized by higher wind power and lower rainfall that can reduce, but not completely destroy, the vegetation cover, leading to the formation of lee (shadow) dunes behind each shrub. Formation of such VLDs can occur today in some coasts where the wind is quite strong and the rain can support some shrubs.

Pattern Analysis of El Nino and La Nina Phenomenon Based on Sea Surface Temperature (SST) and Rainfall Intensity using Oceanic Nino Index (ONI) in West Java Area

NASA Astrophysics Data System (ADS)

Prasetyo, Yudo; Nabilah, Farras

2017-12-01

Climate change occurs in 1998-2016 brings significant alteration in the earth surface. It is affects an extremely anomaly temperature such as El Nino and La Nina or mostly known as ENSO (El Nino Southern Oscillation). West Java is one of the regions in Indonesia that encounters the impact of this phenomenon. Climate change due to ENSO also affects food production and other commodities. In this research, processing data method is conducted using programming language to process SST data and rainfall data from 1998 to 2016. The data are sea surface temperature from NOAA satellite, SST Reynolds (Sea Surface Temperature) and daily rainfall temperature from TRMM satellite. Data examination is done using analysis of rainfall spatial pattern and sea surface temperature (SST) where is affected by El Nino and La Nina phenomenon. This research results distribution map of SST and rainfall for each season to find out the impacts of El Nino and La Nina around West Java. El Nino and La Nina in Java Sea are occurring every August to February. During El Nino, sea surface temperature is between 27°C - 28°C with average temperature on 27.71°C. Rainfall intensity is 1.0 mm/day - 2.0 mm/day and the average are 1.63 mm/day. During La Nina, sea surface temperature is between 29°C - 30°C with average temperature on 29.06°C. Rainfall intensity is 9.0 mm/day - 10 mm/day, and the average is 9.74 mm/day. The correlation between rainfall and SST is 0,413 which is expresses a fairly strong correlation between parameters. The conclusion is, during La Nina SST and rainfall increase. While during El Nino SST and rainfall decrease. Hopefully this research could be a guideline to plan disaster mitigation in West Java region that is related extreme climate change.

Wind Shear Identification with the Retrieval Wind of Doppler Wearth Radar

NASA Astrophysics Data System (ADS)

Zhou, S.; Cui, Y.; Zheng, H.; Zhang, T.

2018-05-01

A new method, which based on the wind field retrieval algorithm of Volume Velocity Process (VVP), has been used to identified the intensity of wind shear occurred in a severe convection process in Guangzhou. The intensity of wind shear's strength shown that new cells would be more likely to generate in areas where the magnitude generally larger than 3.0 m/(s*km). Moreover, in the areas of potential areas of rainfall, the wind shear's strength would larger than 4.5 m/(s*km). This wind shear identify method is very helpful to forecasting severe convections' moving and developments.

Environmental Factors Related to a Semiarid Climate Influence the Freezability of Sperm from Collared Peccaries (Pecari tajacu Linnaeus, 1758).

PubMed

Maia, Keilla M; Souza, Ana L P; Praxedes, Erica C G; Bezerra, Luana G P; Silva, Andreia M; Campos, Livia B; Moreira, Samara S J; Apolinário, Carlos A C; Souza, João B F; Silva, Alexandre R

2018-04-30

The influence of environmental factors in a semiarid climate on characteristics of fresh and frozen/thawed sperm collected from collared peccaries (Pecari tajacu) was assessed. Semen from 11 male collared peccaries was collected by electroejaculation during the peaks of the dry and rainy periods while rainfall indices, air temperatures, relative humidity levels, and wind speeds were measured. The number, motility, morphology, osmotic response, and membrane integrity of sperm in the collected ejaculates were assessed. Samples were then frozen in liquid nitrogen, thawed, and reassessed. The rainfall index of the rainy period (73.2 mm) was significantly higher than that of the dry period (13.6 mm) and the relative humidity was significantly higher during the rainy period (74.6%) than it was during the dry period (66.8%). Air temperature and wind speed did not differ between the two periods. Characteristics of sperm in the fresh samples were not affected by environmental parameters. In contrast, computerized analysis revealed that sperm in samples frozen during the rainy period exhibited better post-thaw membrane integrity (28.6 ± 6%), motility (29.5 ± 7.7%), and rapid sperm population (13.7 ± 6.2%) than did sperm in samples frozen during the dry period (23.4 ± 3% membrane integrity, 14.6 ± 4.1% motility, and 4.1 ± 1.2% rapid sperm; p < 0.05). Other characteristics of the frozen/thawed sperm did not differ depending on the period in which they were collected. We demonstrated that environmental parameters did not affect the quality of fresh sperm, but could influence the freezability of sperm collected from collared peccaries raised under a semiarid climate.

Effects of environmental variables on invasive amphibian activity: Using model selection on quantiles for counts

USGS Publications Warehouse

Muller, Benjamin J.; Cade, Brian S.; Schwarzkoph, Lin

2018-01-01

Many different factors influence animal activity. Often, the value of an environmental variable may influence significantly the upper or lower tails of the activity distribution. For describing relationships with heterogeneous boundaries, quantile regressions predict a quantile of the conditional distribution of the dependent variable. A quantile count model extends linear quantile regression methods to discrete response variables, and is useful if activity is quantified by trapping, where there may be many tied (equal) values in the activity distribution, over a small range of discrete values. Additionally, different environmental variables in combination may have synergistic or antagonistic effects on activity, so examining their effects together, in a modeling framework, is a useful approach. Thus, model selection on quantile counts can be used to determine the relative importance of different variables in determining activity, across the entire distribution of capture results. We conducted model selection on quantile count models to describe the factors affecting activity (numbers of captures) of cane toads (Rhinella marina) in response to several environmental variables (humidity, temperature, rainfall, wind speed, and moon luminosity) over eleven months of trapping. Environmental effects on activity are understudied in this pest animal. In the dry season, model selection on quantile count models suggested that rainfall positively affected activity, especially near the lower tails of the activity distribution. In the wet season, wind speed limited activity near the maximum of the distribution, while minimum activity increased with minimum temperature. This statistical methodology allowed us to explore, in depth, how environmental factors influenced activity across the entire distribution, and is applicable to any survey or trapping regime, in which environmental variables affect activity.

The effects of daily weather variables on psychosis admissions to psychiatric hospitals

NASA Astrophysics Data System (ADS)

McWilliams, Stephen; Kinsella, Anthony; O'Callaghan, Eadbhard

2013-07-01

Several studies have noted seasonal variations in admission rates of patients with psychotic illnesses. However, the changeable daily meteorological patterns within seasons have never been examined in any great depth in the context of admission rates. A handful of small studies have posed interesting questions regarding a potential link between psychiatric admission rates and meteorological variables such as environmental temperature (especially heat waves) and sunshine. In this study, we used simple non-parametric testing and more complex ARIMA and time-series regression analysis to examine whether daily meteorological patterns (wind speed and direction, barometric pressure, rainfall, sunshine, sunlight and temperature) exert an influence on admission rates for psychotic disorders across 12 regions in Ireland. Although there were some weak but interesting trends for temperature, barometric pressure and sunshine, the meteorological patterns ultimately did not exert a clinically significant influence over admissions for psychosis. Further analysis is needed.

Spatial variation of deterministic chaos in mean daily temperature and rainfall over Nigeria

NASA Astrophysics Data System (ADS)

Fuwape, I. A.; Ogunjo, S. T.; Oluyamo, S. S.; Rabiu, A. B.

2017-10-01

Daily rainfall and temperature data from 47 locations across Nigeria for the 36-year period 1979-2014 were treated to time series analysis technique to investigate some nonlinear trends in rainfall and temperature data. Some quantifiers such as Lyapunov exponents, correlation dimension, and entropy were obtained for the various locations. Positive Lyapunov exponents were obtained for the time series of mean daily rainfall for all locations in the southern part of Nigeria while negative Lyapunov exponents were obtained for all locations in the Northern part of Nigeria. The mean daily temperature had positive Lyapunov exponent values (0.35-1.6) for all the locations. Attempts were made in reconstructing the phase space of time series of rainfall and temperature.

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.

The effects of low-tide rainfall on metal content of suspended sediment in the Sacramento-San Joaquin Delta

NASA Astrophysics Data System (ADS)

Moskalski, S. M.; Torres, R.; Bizimis, M.; Bergamaschi, B. A.; Fleck, J.; Goni, M. A.

2012-12-01

Rain falling near low tide is capable of eroding and transporting cohesive sediment from marsh and mudflat surfaces. Given that metals adsorb strongly to silt- and clay-sized particles, it is conceivable that lowtide rainfall may also liberate previously-deposited metals from storage in intertidal sediment. To investigate the potential for rainfall as an agent of remobilization of metals, this study tested the hypothesis of sediment, and therefore metals and nutrients, mobilization during these punctuated low-tide rainfall events. Water samples were collected during low-tide rain events in winter and wind resuspension events in summer from a marsh in central California. The concentrations of suspended sediment, particulate organic carbon and nitrogen, and total adsorbed concentration (mass of metal per volume of filtered water) of most metals were higher during a low tide rainfall event than during wind-only and fair-weather events. Metal contents (mass of metal per mass of sediment) were also greater during the rain event for most metals. Principle components analysis and the relationships between total adsorbed metals and SSC suggest rainfall during low tide can mobilize a different source of sediment than the background sediment available for tidal and wind-wave resuspension. The metal content of bulk sediment samples from around the study area could not be matched satisfactorily to the suspended sediment in any of the events, implying that bulk sediment should not be used to extrapolate to suspended sediment in terms of adsorbed metal content. Some of the adsorbed metals were present during the rain event in amounts that could be toxic, depending on the actual bioavailability of the metals.; Summary plots of measured organic parameters. (A) POC (B) PN (C) C:N (D) total leachable metal concentration, sum of all measured metals. The solid line inside box is the median and the dashed line is the mean.

Enhancement of orographic precipitation in Jeju Island during the passage of Typhoon Khanun (2012)

NASA Astrophysics Data System (ADS)

Lee, Jung-Tae; Ko, Kyeong-Yeon; Lee, Dong-In; You, Cheol-Hwan; Liou, Yu-Chieng

2018-03-01

Typhoon Khanun caused over 226 mm of accumulated rainfall for 6 h (0700 to 1300 UTC), localized around the summit of Mt. Halla (height 1950 m), with a slanted rainfall pattern to the northeast. In this study, we investigated the enhancement mechanism for precipitation near the mountains as the typhoon passed over Jeju Island via dual-Doppler radar analysis and simple trajectory of passive tracers using a retrieved wind field. The analysis of vertical profiles of the mountain region show marked features matching the geophysical conditions. In the central mountain region, a strong wind (≥ 7 m s- 1) helps to lift low-level air up the mountain. The time taken for lifting is longer than the theoretical time required for raindrop growth via condensation. The falling particles (seeder) from the upper cloud were also one of the reasons for an increase in rainfall via the accretion process from uplifted cloud water (feeder). The lifted air and falling particles both contributed to the heavy rainfall in the central region. In contrast, on the leeward side, the seeder-feeder mechanism was important in the formation of strong radar reflectivity. The snow particles (above 5 km) were accelerated by strong downward winds (≤-6 m s- 1). Meanwhile, the nonlinear jumping flow (hydraulic jump) raised feeders (shifted from the windward side) to the upper level where particles fall. To support these development processes, a numerical simulation using cloud-resolving model theoretically carried out. The accreting of hydrometeors may be one of the key reasons why the lee side has strong radar reflectivity, and a lee side weighted rainfall pattern even though lee side includes no strong upward air motion.

Convective cell development and propagation in a mesoscale convective complex

NASA Technical Reports Server (NTRS)

Ahn, Yoo-Shin; Brundidge, Kenneth C.

1987-01-01

A case study was made of the mesoscale convective complex (MCC) which occurred over southern Oklahoma and northern Texas on 27 May 1981. This storm moved in an eastsoutheasterly direction and during much of its lifetime was observable by radars at Oklahoma City, Ok. and Stephenville, Tx. It was found that the direction of cell (VIP level 3 or more reflectivity) propagation was somewhat erratic but approximately the same as the system (VIP level 1 reflectivity) movement and the ambient wind. New cells developed along and behind the gust front make it appear that once the MCC is initiated, a synergistic relationship exists between the gust front and the MCC. The relationship between rainfall patterns and amounts and the infrared (IR) temperature field in the satellite imagery were examined. The 210 K isotherm of GOES IR imagery was found to encompass the rain area of the storm. The heaviest rainfall was in the vicinity of the VIP level 3 cells and mostly contained within the 205 K isotherm of GOES IR imagery.

[Ammonia volatilization loss of nitrogen fertilizer from rice field and wet deposition of atmospheric nitrogen in rice growing season].

PubMed

Su, Chengguo; Yin, Bin; Zhu, Zhaoliang; Shen, Qirong

2003-11-01

Plot and field experiments showed that the NH3 volatilization loss from rice field reached its maximum in 1-3 days after N-fertilization, which was affected by the local climate conditions (e.g., sun illumination, temperature, humidity, wind speed, and rainfall), fertilization time, and ammonium concentration in surface water of the rice field. The wet deposition of atmospheric nitrogen was correlated with the application rate of N fertilizer and the rainfall. The amount of nitrogen brought into soil or surface water by the wet deposition in rice growing season reached 7.5 kg.hm-2. The percent of NH4(+)-N in the wet deposition was about 39.8%-73.2%, with an average of 55.5%. There was a significant correlation of total ammonia volatilization loss with the average concentration of NH4(+)-N in wet deposition and total amount of wet deposition in rice growing season.

The influence of sea surface temperature on the intensity and associated storm surge of tropical cyclone Yasi: a sensitivity study

NASA Astrophysics Data System (ADS)

Lavender, Sally L.; Hoeke, Ron K.; Abbs, Deborah J.

2018-03-01

Tropical cyclones (TCs) result in widespread damage associated with strong winds, heavy rainfall and storm surge. TC Yasi was one of the most powerful TCs to impact the Queensland coast since records began. Prior to Yasi, the SSTs in the Coral Sea were higher than average by 1-2 °C, primarily due to the 2010/2011 La Niña event. In this study, a conceptually simple idealised sensitivity analysis is performed using a high-resolution regional model to gain insight into the influence of SST on the track, size, intensity and associated rainfall of TC Yasi. A set of nine simulations with uniform SST anomalies of between -4 and 4 °C applied to the observed SSTs are analysed. The resulting surface winds and pressure are used to force a barotropic storm surge model to examine the influence of SST on the associated storm surge of TC Yasi. An increase in SST results in an increase in intensity, precipitation and integrated kinetic energy of the storm; however, there is little influence on track prior to landfall. In addition to an increase in precipitation, there is a change in the spatial distribution of precipitation as the SST increases. Decreases in SSTs result in an increase in the radius of maximum winds due to an increase in the asymmetry of the storm, although the radius of gale-force winds decreases. These changes in the TC characteristics also lead to changes in the associated storm surge. Generally, cooler (warmer) SSTs lead to reduced (enhanced) maximum storm surges. However, the increase in surge reaches a maximum with an increase in SST of 2 °C. Any further increase in SST does not affect the maximum surge but the total area and duration of the simulated surge increases with increasing upper ocean temperatures. A large decrease in maximum storm surge height occurs when a negative SST anomaly is applied, suggesting if TC Yasi had occurred during non-La Niña conditions the associated storm surge may have been greatly diminished, with a decrease in storm surge height of over 3 m when the SST is reduced by 2 °C. In summary, increases in SST lead to an increase in the potential destructiveness of TCs with regard to intensity, precipitation and storm surge, although this relationship is not linear.

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 UK portrait of wind-induced undercatch in rainfall measurement

NASA Astrophysics Data System (ADS)

Pollock, Michael; Quinn, Paul; O'Donnell, Greg; Colli, Matteo; Dutton, Mark; Black, Andrew; Wilkinson, Mark; Kilsby, Chris; Stagnaro, Mattia; Lanza, Luca; O'Connell, Enda

2017-04-01

Rainfall is vital to life; civilisation depends upon it. Changing local and regional rainfall regimes toward more intense storm events (e.g. in the UK), increases the existing challenge of accurately measuring and modelling rainfall. Data from rain gauges, often considered to provide the most accurate practicable measure of precipitation at a point in space in time, play a critical role. They are used for, inter alia, flood forecasting and flood risk management; radar calibration and numerical weather prediction models; urban planning and drainage; and water resource management and hydrological modelling. Despite the key importance of these measurements, they remain susceptible to fundamental sources of systematic error which are often not considered when rainfall data are used. Inaccuracies in measurements are compounded in modelling applications by producing potentially misleading or incorrect results; it is therefore of great importance to understand and present uncertainty in observations. Standard practice is to mount rain gauges above the ground surface. This configuration obstructs the prevailing wind which causes an acceleration of airflow above the orifice. Precipitation is deflected away from the orifice and lands 'downstream' of the area represented by the gauge measurement, reducing its collection efficiency (CE). This phenomenon is commonly referred to as 'wind-induced undercatch'. The physical shape of a gauge bears a significant impact on its CE. Computational Fluid Dynamics (CFD) simulations are used to investigate how different shapes of precipitation gauge are affected by the wind. CFD modelling is supported by high-resolution field measurements at several exposed 'Hydro-Met' research stations in the UK. These sites are occupied by rain gauges which are scrutinised in the CFD analyses. The reference measurements at all sites are made within a WMO reference pit, where the rain gauge is mounted with its orifice at ground level and surrounded by an appropriate grid structure. 'Undercatch' exhibited within UK storms, not captured by operational gauge networks in the UK, is quantified and presented in this study. Results from CFD modelling and the field studies show that gauge shape and mounting height significantly affect the extent of the undercatch. 'Aerodynamic' gauges following a 'champagne flute' or a 'funnel' profile were demonstrated by both to have significant advantages over conventional gauge shapes, in terms of improving the CE. This study presents the latest analyses, and proposes the possible extent of rainfall underestimation within the UK, with particular reference to its hydrology.

Potential Predictability and Prediction Skill for Southern Peru Summertime Rainfall

NASA Astrophysics Data System (ADS)

WU, S.; Notaro, M.; Vavrus, S. J.; Mortensen, E.; Block, P. J.; Montgomery, R. J.; De Pierola, J. N.; Sanchez, C.

2016-12-01

The central Andes receive over 50% of annual climatological rainfall during the short period of January-March. This summertime rainfall exhibits strong interannual and decadal variability, including severe drought events that incur devastating societal impacts and cause agricultural communities and mining facilities to compete for limited water resources. An improved seasonal prediction skill of summertime rainfall would aid in water resource planning and allocation across the water-limited southern Peru. While various underlying mechanisms have been proposed by past studies for the drivers of interannual variability in summertime rainfall across southern Peru, such as the El Niño-Southern Oscillation (ENSO), Madden Julian Oscillation (MJO), and extratropical forcings, operational forecasts continue to be largely based on rudimentary ENSO-based indices, such as NINO3.4, justifying further exploration of predictive skill. In order to bridge this gap between the understanding of driving mechanisms and the operational forecast, we performed systematic studies on the predictability and prediction skill of southern Peru summertime rainfall by constructing statistical forecast models using best available weather station and reanalysis datasets. At first, by assuming the first two empirical orthogonal functions (EOFs) of summertime rainfall are predictable, the potential predictability skill was evaluated for southern Peru. Then, we constructed a simple regression model, based on the time series of tropical Pacific sea-surface temperatures (SSTs), and a more advanced Linear Inverse Model (LIM), based on the EOFs of tropical ocean SSTs and large-scale atmosphere variables from reanalysis. Our results show that the LIM model consistently outperforms the more rudimentary regression models on the forecast skill of domain averaged precipitation index and individual station indices. The improvement of forecast correlation skill ranges from 10% to over 200% for different stations. Further analysis shows that this advantage of LIM is likely to arise from its representation of local zonal winds and the position of Intertropical Convergence Zone (ITCZ).

Impact of Sea Level Rise on Storm Surge and Inundation in the Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Veeramony, J.

2016-12-01

Assessing the impact of climate change on surge and inundation due to tropical cyclones is important for coastal adaptation as well as mitigation efforts. Changes in global climate increase vulnerability of coastal environments to the threat posed by severe storms in a number of ways. Both the intensity of future storms as well as the return periods of more severe storms are expected to increase signficantly. Increasing mean sea levels lead to more areas being inundated due to storm surge and bring the threat of inundation further inland. Rainfall associated with severe storms are also expected to increase substantially, which will add to the intensity of inland flooding and coastal inundation. In this study, we will examine the effects of sea level rise and increasing rainfall intensity using Hurricane Ike as the baseline. The Delft3D modeling system will be set up in nested mode, with the outermost nest covering the Gulf of Mexico. The system will be run in a coupled mode, modeling both waves and the hydrodynamics. The baseline simulation will use the atmospheric forcing which consists of the NOAA H*Wind (Powell et all 1998) for the core hurricane characteristics blended with reanalyzed background winds to create a smooth wind field. The rainfall estimates are obtained from TRMM. From this baseline, a set of simulations will be performed to show the impact of sea level rise and increased rainfall activity on flooding and inundation along theTexas-Lousiana coast.

Relating rainfall characteristics to cloud top temperatures at different scales

NASA Astrophysics Data System (ADS)

Klein, Cornelia; Belušić, Danijel; Taylor, Christopher

2017-04-01

Extreme rainfall from mesoscale convective systems (MCS) poses a threat to lives and livelihoods of the West African population through increasingly frequent devastating flooding and loss of crops. However, despite the significant impact of such extreme events, the dominant processes favouring their occurrence are still under debate. In the data-sparse West African region, rainfall radar data from the Tropical Rainfall Measuring Mission (TRMM) gives invaluable information on the distribution and frequency of extreme rainfall. The TRMM 2A25 product provides a 15-year dataset of snapshots of surface rainfall from 2-4 overpasses per day. Whilst this sampling captures the overall rainfall characteristics, it is neither long nor frequent enough to diagnose changes in MCS properties, which may be linked to the trend towards rainfall intensification in the region. On the other hand, Meteosat geostationary satellites provide long-term sub-hourly records of cloud top temperatures, raising the possibility of combining these with the high-quality rainfall data from TRMM. In this study, we relate TRMM 2A25 rainfall to Meteosat Second Generation (MSG) cloud top temperatures, which are available from 2004 at 15 minutes intervals, to get a more detailed picture of the structure of intense rainfall within the life cycle of MCS. We find TRMM rainfall intensities within an MCS to be strongly coupled with MSG cloud top temperatures: the probability for extreme rainfall increases from <10% for minimum temperatures warmer than -40°C to over 70% when temperatures drop below -70°C, confirming the potential in analysing cloud-top temperatures as a proxy for extreme rain. The sheer size of MCS raises the question which scales of sub-cloud structures are more likely to be associated with extreme rain than others. In the end, this information could help to associate scale changes in cloud top temperatures with processes that affect the probability of extreme rain. We use 2D continuous wavelets to decompose cloud top temperatures into power spectra at scales between 15 and 200km. From these, cloud sub-structures are identified as circular areas of respective scale with local power maxima in their centre. These areas are then mapped onto coinciding TRMM rainfall, allowing us to assign rainfall fields to sub-cloud features of different scales. We find a higher probability for extreme rainfall for cloud features above a scale of 30km, with features 100km contributing most to the number of extreme rainfall pixels. Over the average diurnal cycle, the number of smaller cloud features between 15-60km shows an increase between 15 - 1700UTC, gradually developing into larger ones. The maximum of extreme rainfall pixels around 1900UTC coincides with a peak for scales 100km, suggesting a dominant role of these scales for intense rain for the analysed cloud type. Our results demonstrate the suitability of 2D wavelet decomposition for the analysis of sub-cloud structures and their relation to rainfall characteristics, and help us to understand long-term changes in the properties of MCS.

Determination of inorganic particulates: (cationic, anionic and heavy metals) in the atmosphere of some areas in Bahrain during the Gulf crisis in 1991

NASA Astrophysics Data System (ADS)

Ali-Mohamed, Ahmed Y.; Matter, Haifa A.

Inorganic particulate matter was sampled weekly during the period March-May, 1991 at different sites at height of ˜6-9 m above the ground level. Deposited aerosols were chemically analyzed and a comparison was made between these sites. The percentage of tarry matter deposited on the airborne particulate matter was found to be 40% during the Gulf crisis compared to 5% prior to Gulf war (1985/86). Heavy metal analysis are also reported. The results were influenced differently by some atmospheric parameters such as temperature, humidity, rainfall, pressure and wind speed/direction.

Multifuctional integrated sensors (MFISES).

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

Homeijer, Brian D.; Roozeboom, Clifton

2015-10-01

Many emerging IoT applications require sensing of multiple physical and environmental parameters for: completeness of information, measurement validation, unexpected demands, improved performance. For example, a typical outdoor weather station measures temperature, humidity, barometric pressure, light intensity, rainfall, wind speed and direction. Existing sensor technologies do not directly address the demand for cost, size, and power reduction in multi-paramater sensing applications. Industry sensor manufacturers have developed integrated sensor systems for inertial measurements that combine accelerometers, gyroscopes, and magnetometers, but do not address environmental sensing functionality. In existing research literature, a technology gap exists between the functionality of MEMS sensors and themore » real world applications of the sensors systems.« less

Temperature Crosstalk Sensitivity of the Kummerow Rainfall Algorithm

NASA Technical Reports Server (NTRS)

Spencer, Roy W.; Petrenko, Boris

1999-01-01

Even though the signal source for passive microwave retrievals is thermal emission, retrievals of non-temperature geophysical parameters typically do not explicitly take into account the effects of temperature change on the retrievals. For global change research, changes in geophysical parameters (e.g. water vapor, rainfall, etc.) are referenced to the accompanying changes in temperature. If the retrieval of a certain parameter has a cross-talk response from temperature change alone, the retrievals might not be very useful for climate research. We investigated the sensitivity of the Kummerow rainfall retrieval algorithm to changes in air temperature. It was found that there was little net change in total rainfall with air temperature change. However, there were non-negligible changes within individual rain rate categories.

Idealized Cloud-System Resolving Modeling for Tropical Convection Studies

NASA Astrophysics Data System (ADS)

Anber, Usama M.

A three-dimensional limited-domain Cloud-Resolving Model (CRM) is used in idealized settings to study the interaction between tropical convection and the large scale dynamics. The model domain is doubly periodic and the large-scale circulation is parameterized using the Weak Temperature Gradient (WTG) Approximation and Damped Gravity Wave (DGW) methods. The model simulations fall into two main categories: simulations with a prescribed radiative cooling profile, and others in which radiative cooling profile interacts with clouds and water vapor. For experiments with a prescribed radiative cooling profile, radiative heating is taken constant in the vertical in the troposphere. First, the effect of turbulent surface fluxes and radiative cooling on tropical deep convection is studied. In the precipitating equilibria, an increment in surface fluxes produces a greater increase in precipitation than an equal increment in column-integrated radiative heating. The gross moist stability remains close to constant over a wide range of forcings. With dry initial conditions, the system exhibits hysteresis, and maintains a dry state with for a wide range of net energy inputs to the atmospheric column under WTG. However, for the same forcings the system admits a rainy state when initialized with moist conditions, and thus multiple equilibria exist under WTG. When the net forcing is increased enough that simulations, which begin dry, eventually develop precipitation. DGW, on the other hand, does not have the tendency to develop multiple equilibria under the same conditions. The effect of vertical wind shear on tropical deep convection is also studied. The strength and depth of the shear layer are varied as control parameters. Surface fluxes are prescribed. For weak wind shear, time-averaged rainfall decreases with shear and convection remains disorganized. For larger wind shear, rainfall increases with shear, as convection becomes organized into linear mesoscale systems. This non-monotonic dependence of rainfall on shear is observed when the imposed surface fluxes are moderate. For larger surface fluxes, convection in the unsheared basic state is already strongly organized, but increasing wind shear still leads to increasing rainfall. In addition to surface rainfall, the impacts of shear on the parameterized large-scale vertical velocity, convective mass fluxes, cloud fraction, and momentum transport are also discussed. For experiments with interactive radiative cooling profile, the effect of cloud-radiation interaction on cumulus ensemble is examined in sheared and unsheared environments with both fixed and interactive sea surface temperature (SST). For fixed SST, interactive radiation, when compared to simulations in which radiative profile has the same magnitude and vertical shape but does not interact with clouds or water vapor, is found to suppress mean precipitation by inducing strong descent in the lower troposphere, increasing the gross moist stability. For interactive SST, using a slab ocean mixed layer, there exists a shear strength above which the system becomes unstable and develops oscillatory behavior. Oscillations have periods of wet precipitating states followed by periods of dry non-precipitating states. The frequencies of oscillations are intraseasonal to subseasonal, depending on the mixed layer depth. Finally, the model is coupled to a land surface model with fully interactive radiation and surface fluxes to study the diurnal and seasonal radiation and water cycles in the Amazon basin. The model successfully captures the afternoon precipitation and cloud cover peak and the greater latent heat flux in the dry season for the first time; two major biases in GCMs with implications for correct estimates of evaporation and gross primary production in the Amazon. One of the key findings is that the fog layer near the surface in the west season is crucial for determining the surface energy budget and precipitation. This suggests that features on the diurnal time scale can significantly impact climate on the seasonal time scale.

Impacts of climate and synoptic fluctuations on dust storm activity over the Middle East

NASA Astrophysics Data System (ADS)

Namdari, Soodabeh; Karimi, Neamat; Sorooshian, Armin; Mohammadi, GholamHasan; Sehatkashani, Saviz

2018-01-01

Dust events in the Middle East are becoming more frequent and intense in recent years with impacts on air quality, climate, and public health. In this study, the relationship between dust, as determined from Aerosol Optical Depth (AOD) and meteorological parameters (precipitation, temperature, pressure and wind field) are examined using monthly data from 2000 to 2015 for desert areas in two areas, Iraq-Syria and Saudi Arabia. Bivariate regression analysis between monthly temperature data and AOD reveals a high correlation for Saudi Arabia (R = 0.72) and Iraq-Syria (R = 0.64). Although AOD and precipitation are correlated in February, March and April, the relationship is more pronounced on annual timescales. The opposite is true for the relationship between temperature and AOD, which is evident more clearly on monthly time scales, with the highest temperatures and AOD typically between August and September. Precipitation data suggest that long-term reductions in rainfall promoted lower soil moisture and vegetative cover, leading to more intense dust emissions. Superimposed on the latter effect are more short term variations in temperature exacerbating the influence on the dust storm genesis in hot periods such as the late warm season of the year. Case study analysis of March 2012 and March 2014 shows the impact of synoptic systems on dust emissions and transport in the study region. Dust storm activity was more intense in March 2012 as compared to March 2014 due to enhanced atmospheric turbulence intensifying surface winds.

Investigating the Climate System: WINDS. Winds at work. Problem-Based Classroom Modules

ERIC Educational Resources Information Center

Astwood, Phil

2003-01-01

With support from National Aeronautics and Space Administration's (NASA's) Goddard Space Flight Center, Institute for Global Environmental Strategies (IGES) has developed educational materials that incorporate information and data from the Tropical Rainfall Measuring Mission (TRMM), a joint satellite mission between the United States and Japan.…

Variability and trends of wet season temperature in the Sudano-Sahelian zone and relationships with precipitation

NASA Astrophysics Data System (ADS)

Oueslati, Boutheina; Camberlin, Pierre; Zoungrana, Joël; Roucou, Pascal; Diallo, Saliou

2018-02-01

The relationships between precipitation and temperature in the central Sudano-Sahelian belt are investigated by analyzing 50 years (1959-2008) of observed temperature (Tx and Tn) and rainfall variations. At daily time-scale, both Tx and Tn show a marked decrease as a response to rainfall occurrence, with a strongest departure from normal 1 day after the rainfall event (-0.5 to -2.5 °C depending on the month). The cooling is slightly larger when heavy rainfall events (>5 mm) are considered. The temperature anomalies weaken after the rainfall event, but are still significant several days later. The physical mechanisms accounting for the temperature response to precipitation are analysed. The Tx drop is accounted for by reduced incoming solar radiation associated with increased cloud cover and increased surface evaporation following surface moistening. The effect of evaporation becomes dominant a few days after the rainfall event. The reduced daytime heat storage and the subsequent sensible heat flux result in a later negative Tn anomaly. The effect of rainfall variations on temperature is significant for long-term warming trends. The rainfall decrease experienced between 1959 and 2008 accounts for a rainy season Tx increase of 0.15 to 0.3 °C, out of a total Tx increase of 1.3 to 1.5 °C. These results have strong implications on the assessment of future temperature changes. The dampening or amplifying effects of precipitation are determined by the sign of future precipitation trends. Confidence on temperature changes under global warming partly depend on the robustness of precipitation projections.

Effects of seasonal climatic variability on several toxic contaminants in urban lakes: Implications for the impacts of climate change.

PubMed

Wu, Qiong; Xia, Xinghui; Mou, Xinli; Zhu, Baotong; Zhao, Pujun; Dong, Haiyang

2014-12-01

Climate change is supposed to have influences on water quality and ecosystem. However, only few studies have assessed the effect of climate change on environmental toxic contaminants in urban lakes. In this research, response of several toxic contaminants in twelve urban lakes in Beijing, China, to the seasonal variations in climatic factors was studied. Fluorides, volatile phenols, arsenic, selenium, and other water quality parameters were analyzed monthly from 2009 to 2012. Multivariate statistical methods including principle component analysis, cluster analysis, and multiple regression analysis were performed to study the relationship between contaminants and climatic factors including temperature, precipitation, wind speed, and sunshine duration. Fluoride and arsenic concentrations in most urban lakes exhibited a significant positive correlation with temperature/precipitation, which is mainly caused by rainfall induced diffuse pollution. A negative correlation was observed between volatile phenols and temperature/precipitation, and this could be explained by their enhanced volatilization and biodegradation rates caused by higher temperature. Selenium did not show a significant response to climatic factor variations, which was attributed to low selenium contents in the lakes and soils. Moreover, the response degrees of contaminants to climatic variations differ among lakes with different contamination levels. On average, temperature/precipitation contributed to 8%, 15%, and 12% of the variations in volatile phenols, arsenic, and fluorides, respectively. Beijing is undergoing increased temperature and heavy rainfall frequency during the past five decades. This study suggests that water quality related to fluoride and arsenic concentrations of most urban lakes in Beijing is becoming worse under this climate change trend. Copyright © 2014. Published by Elsevier B.V.

Incident rainfall in Rome and its relation to biodeterioration of buildings

NASA Astrophysics Data System (ADS)

Caneva, G.; Gori, E.; Danin, A.

Intensity and distribution of incident rainfall in Rome, and degree of lithobiont cover of building walls, were estimated, and their correlation was discussed. Rainfall and wind data over 10 years for the Rome Meteorological Observatory of Torre Calandrelli (UCEA) were used to calculate the actual hydrocontribution received over walls at various exposures. The biological colonization by lithobionts was evaluated on a sample of 14 buildings in various places of the city, using a phytosociological scale for quantifying their total cover. During all seasons the rainfall shows a significant peak in the south and the southeast exposures, where the highest cover of lithobionts is found. These results show the role of incident rainfall in the climatic conditions of Rome as the main driving factor for the growth of lithobionts on walls where rainfall is their principal source of water.

Impacts of Climate Change on Water Requirements of Dry Season Boro Rice: Recent Trends and Future Scenarios

NASA Astrophysics Data System (ADS)

Acharjee, T. K.; Ludwig, F.; Halsema, G. V.; Hellegers, P.; Supit, I.

2017-12-01

The North-West part of Bangladesh is vulnerable to the impacts of climate change, because of dry season water shortage and high water demand for rice cultivation. A study was carried out to understand the impacts of recent climate change (1980-2013) and future consequences (for 2050s and 2080s) on water requirements of Boro rice. The reference crop evapotranspiration (ETo), potential crop water requirement (∑ETC), effective rainfall (ER), potential irrigation requirement for crop evapotranspiration (∑ETC-ER) and net irrigation requirement of Boro rice were estimated in CropWat using observed daily climate data for recent trends and statistically downscaled and bias corrected GCM outputs (five models and two RCPs) for future scenarios. ETo showed a significant decreasing recent trends due to increasing relative humidity and decreasing wind speed and sun shine hours instead of an increase in temperature. However, the strong future increase in temperature will lead to an insignificant increase in ETo. ∑ETC showed a decreasing recent trend and will further decrease in the future because of shortened duration of Boro growth stages as crop's phenological response to increased temperature. The variations in trends of ∑ETC-ER found among different districts, are mainly linked to the variations in trends of changes in effective rainfall. During last three decades, the net irrigation requirement has decreased by 11% at an average rate of -4.4 mm/year, instead of a decreasing effective rainfall, mainly because of high rate of decrease of crop evapotranspiration (-5.9 mm/year). In future, although daily water requirement will increase, the total net irrigation requirement of Boro rice will decrease by 1.6% in 2050s and 7.4% in 2080s for RCP 8.5 scenario on an average for five models and four districts compared to the base period (1980-2013). High variations in projected changes in rainfall bring high uncertainty for future water requirements estimation. Therefore, a warming climate will not directly increase the water demand for crop agriculture in North-West Bangladesh but will make the future agricultural water management more complex by bringing more variations and uncertainty in the system.

Four-Dimensional Oceanic and Atmosperic Data Assimilation with Tropical Rainfall Measuring Mission Data

NASA Technical Reports Server (NTRS)

Takano, Kenji

1996-01-01

An oceanic data assimilation system which allows to utilize the forthcoming Tropical Rainfall Measuring Mission (TRMM) data has been developed and applied to the Pacific Ocean to produce the velocity field. The assimilated data will be indispensable to examine the effects of rainfall and its variability on the structure and circulation of the tropical oceans and to assess the impact of global warming due to the increase of carbon dioxide on the ocean circulation system and the marine pollution caused by oil spill and ocean damping of radionuclide. The data will also provide the verification for the oceanic and ocean-atmosphere coupled General Circulation Models (GCM's). The system consists of oceanic GCM, analysis scheme and data. In the system the flow field has been determined to be physically consistent with the observed density field and the sea surface winds derived from the Special Sensor Microwave Imagery (SSM/I) data which drive the ocean current. The time integration has been performed for five years until the flow field near the surface attained the steady state starting from the rest ocean with observed temperature and salinity fields, and the SSM/I surface wind velocity. The resultant flow field showed high producibility of the system. Especially the flow near the ocean surface agreed well with available observed data. The system, for the first time, succeeded to produce the eastward subtropical current which has been discovered in the joint investigation on Kuroshio current (CSK) in the 1960s. To verify the quality of the flow field a trajectory analysis has been carried out and compared with the Algos buoy data. BRIEF DESCRIPTION OF THE DATA ASSIMILATION SYSTEM ## Oceanic GCM and analysis scheme--The basic equations are much the same as used for the GCM's, except for the Newtonian damping terms introduced into the prediction equations for the potential temperature and salinity to maintain these fields as observed. The C grid of 2'lat. by 2'long. in horizontal and the 11 vertical levels are applied to the entire Pacific Ocean. At the east and west ocean boundaries the periodic boundary conditions are applied creating fictitious ocean there. The SMAC Method is used to increase the accuracy of mass conservation. * Data--The JODC temperature and salinity data obtained from 1906 to 1988 are used in the system between Long.100'E. and 60'W. The surface wind data are derived from the SSM/I data by Dr-R. Atlas of NASA/GSFC. The data set contains every 6 hours data from July 1987 to June 1989 on the grid of 2'lat. by 2.5'long. The averaged for the whole period and then interpolated into the 2'lat. by 2'long. grid data are used to force the system. The sea bottom topography data was based on the General Bathymetric Chart of the Ocean (GEBCO) supplied by the Canadian Hydrographic Service under contract with the International Hydrographic Organization and International Oceanographic Commission of UNESCO.

Rainfall model investigation and scenario analyses of the effect of government reforestation policy on seasonal rainfalls: A case study from Northern Thailand

NASA Astrophysics Data System (ADS)

Duangdai, Eakkapong; Likasiri, Chulin

2017-03-01

In this work, 4 models for predicting rainfall amounts are investigated and compared using Northern Thailand's seasonal rainfall data for 1973-2008. Two models, global temperature, forest area and seasonal rainfall (TFR) and modified TFR based on a system of differential equations, give the relationships between global temperature, Northern Thailand's forest cover and seasonal rainfalls in the region. The other two models studied are time series and Autoregressive Moving Average (ARMA) models. All models are validated using the k-fold cross validation method with the resulting errors being 0.971233, 0.740891, 2.376415 and 2.430891 for time series, ARMA, TFR and modified TFR models, respectively. Under Business as Usual (BaU) scenario, seasonal rainfalls in Northern Thailand are projected through the year 2020 using all 4 models. TFR and modified TFR models are also used to further analyze how global temperature rise and government reforestation policy affect seasonal rainfalls in the region. Rainfall projections obtained via the two models are also compared with those from the International Panel on Climate Change (IPCC) under IS92a scenario. Results obtained through a mathematical model for global temperature, forest area and seasonal rainfall show that the higher the forest cover, the less fluctuation there is between rainy-season and summer rainfalls. Moreover, growth in forest cover also correlates with an increase in summer rainfalls. An investigation into the relationship between main crop productions and rainfalls in dry and rainy seasons indicates that if the rainy-season rainfall is high, that year's main-crop rice production will decrease but the second-crop rice, maize, sugarcane and soybean productions will increase in the following year.

Large-scale atmospheric conditions associated with heavy rainfall episodes in Southeast Brazil

NASA Astrophysics Data System (ADS)

Lima, Kellen Carla; Satyamurty, Prakki; Fernández, Júlio Pablo Reyes

2010-07-01

Heavy rainfall events in austral summer are responsible for almost all the natural disasters in Southeast Brazil. They are mostly associated with two types of atmospheric perturbations: Cold Front (53%) and the South Atlantic Convergence Zone (47%). The important question of what synoptic characteristics distinguish a heavy rainfall event (HRE) from a normal rainfall event (NRE) is addressed in this study. Here, the evolutions of such characteristics are identified through the anomalies with respect to climatology of the composite fields of atmospheric variables. The anomalies associated with HRE are significantly more intense than those associated with NRE in all fundamental atmospheric variables such as outgoing long-wave radiation, sea-level pressure, 500-hPa geopotential, lower and upper tropospheric winds. The moisture flux convergence over Southeast Brazil in the HRE composites is 60% larger than in the NRE composites. The energetics calculations for the HRE that occurred in the beginning of February 1988 strongly suggest that the barotropic instability played an important role in the intensification of the perturbation. These results, especially the intensities of the wind, pressure anomalies, and the moisture convergence are useful for the meteorologists of the Southeast Brazil for forecasting heavy precipitation.

Rainfall Predictions From Global Salinity Anomalies

NASA Astrophysics Data System (ADS)

Schmitt, R. W.; Li, L.; Liu, T.

2016-12-01

We have discovered that sea surface salinity (SSS) is a better seasonal predictor of terrestrial rainfall than sea surface temperature (SST) or the usual pressure modes of atmospheric variability. In many regions, a 3-6 month lead of SSS over rainfall on land can be seen. While some lead is guaranteed due to the simple conservation of water and salt, the robust seasonal lead for SSS in some places is truly remarkable, often besting traditional SST and pressure predictors by a very significant margin. One mechanism for the lead has been identified in the recycling of water on land through soil moisture in regional ocean to land moisture transfers. However, a global search has yielded surprising long-range SSS-rainfall teleconnections. It is suggested that these teleconnections indicate a marked sensitivity of the atmosphere to where rain falls on the ocean. That is, the latent heat of evaporation is by far the largest energy transfer from ocean to atmosphere and where the atmosphere cashes in this energy in the form of precipitation is well recorded in SSS. SSS also responds to wind driven advection and mixing. Thus, SSS appears to be a robust indicator of atmospheric energetics and moisture transport and the timing and location of rainfall events is suggested to influence the subsequent evolution of the atmospheric circulation. In a sense, if the fall of a rain drop is at least equivalent to the flap of a butterfly's wings, the influence of a billion butterfly rainstorm allows for systematic predictions beyond the chaotic nature of the turbulent atmosphere. SSS is found to be particularly effective in predicting extreme precipitation or droughts, which makes its continued monitoring very important for building societal resilience against natural disasters.

Breeding decisions and output are correlated with both temperature and rainfall in an arid-region passerine, the sociable weaver

PubMed Central

Paquet, Matthieu; Spottiswoode, Claire N.; Covas, Rita

2017-01-01

Animal reproductive cycles are commonly triggered by environmental cues of favourable breeding conditions. In arid environments, rainfall may be the most conspicuous cue, but the effects on reproduction of the high inter- and intra-annual variation in temperature remain poorly understood, despite being relevant to the current context of global warming. Here, we conducted a multiyear examination of the relationships between a suite of measures of temperature and rainfall, and the onset and length of the breeding season, the probability of breeding and reproductive output in an arid-region passerine, the sociable weaver (Philetairus socius). As expected, reproductive output increased with rainfall, yet specific relationships were conditional on the timing of rainfall: clutch production was correlated with rainfall throughout the season, whereas fledgling production was correlated with early summer rainfall. Moreover, we reveal novel correlations between aspects of breeding and temperature, indicative of earlier laying dates after warmer springs, and longer breeding seasons during cooler summers. These results have implications for understanding population trends under current climate change scenarios and call for more studies on the role of temperature in reproduction beyond those conducted on temperate-region species. PMID:28989782

Typhoon Maysak

NASA Image and Video Library

2015-03-31

ISS043E078169 (03/31/2015) --- This close up of the huge Typhoon Maysak "eye" of the category 5 (hurricane status on the Saffir-Simpson Wind Scale) was captured by astronauts on board the International Space Station Mar. 31, 2015. The massive Typhoon is headed toward the Philippines and expected to land on the upcoming Easter weekend. The Tropical Rainfall Measuring Mission (TRMM) and Global Precipitation Measurement (GPM) satellites, both co-managed by NASA and the Japan Aerospace Exploration Agency, captured rainfall and cloud data that revealed very heavy rainfall and high thunderstorms in the still strengthening storm.

Time evolution of atmospheric parameters and their influence on sea level pressure over the head Bay of Bengal

NASA Astrophysics Data System (ADS)

Patra, Anindita; Bhaskaran, Prasad K.; Jose, Felix

2018-06-01

A zonal dipole in the observed trends of wind speed and significant wave height over the Head Bay of Bengal region was recently reported in the literature attributed due to the variations in sea level pressure (SLP). The SLP in turn is governed by prevailing atmospheric conditions such as local temperature, humidity, rainfall, atmospheric pressure, wind field distribution, formation of tropical cyclones, etc. The present study attempts to investigate the inter-annual variability of atmospheric parameters and its role on the observed zonal dipole trend in sea level pressure, surface wind speed and significant wave height. It reports on the aspects related to linear trend as well as its spatial variability for several atmospheric parameters: air temperature, geopotential height, omega (vertical velocity), and zonal wind, over the head Bay of Bengal, by analyzing National Centers for Environmental Prediction (NCEP) Reanalysis 2 dataset covering a period of 38 years (1979-2016). Significant warming from sea level to 200 mb pressure level and thereafter cooling above has been noticed during all the seasons. Warming within the troposphere exhibits spatial difference between eastern and western side of the domain. This led to fall in lower tropospheric geopotential height and its east-west variability, exhibiting a zonal dipole pattern across the Head Bay. In the upper troposphere, uplift in geopotential height was found as a result of cooling in higher levels (10-100 mb). Variability in omega also substantiated the observed variations in geopotential height. The study also finds weakening in the upper level westerlies and easterlies. Interestingly, a linear trend in lower tropospheric u-wind component also reveals an east-west dipole pattern over the study region. Further, the study corroborates the reported dipole in trends of sea level pressure, wind speed and significant wave height by evaluating the influence of atmospheric variability on these parameters.

Two Perspectives on Keith

NASA Technical Reports Server (NTRS)

2002-01-01

Tropical storm Keith was born on Sept. 29 in the Caribbean, off the east coast of Honduras, and reached hurricane Category 3 intensity (winds in excess of 111 miles per hour) on Oct. 1. Hurricane Keith made landfall on Mexico's Yucatan Peninsula and northeastern Belize on Oct. 2, packing winds as high as 135 miles per hour and a storm surge of up to 6 feet above normal tide levels. Although the storm quickly weakened in intensity to a tropical storm (65 miles per hour), it moved slowly inland and dumped large amounts of rain on the region--exceeding 15 inches in some areas within a 24-hour period. Authorities in the area are warning residents of the potential for flooding and mudslides. NASA and NOAA satellites captured images of Hurricane Keith on Oct. 2 shortly after it made landfall. The image on the left is a combination of NOAA GOES and NASA QuikScat data superimposed. The white cloud structure was produced using GOES data, while the colored arrows showing wind speed and direction were created using QuikScat data. Red and purple arrows show winds as high as 25 meters per second (56 miles per hour). (Note that QuikScat only measures winds over the ocean; units are given in meters per second.) The image on the right was created using data from the Microwave Imager (TMI) aboard NASA's Tropical Rainfall Measuring Mission (TRMM). That sensor has the ability to peer within a storm and detect rainfall, seen here as red and green blobs. The red blobs show higher rainfall rates (up to 2 inches per hour), and greens show lower rainfall rates (1 inch per hour). Scientists are using data from these sensors to study how hurricane form, and grow and diminish in intensity during their lifetimes. For more information, see Hurricanes: The Greatest Storms on Earth. QuikScat image by William Daffer, courtesy of NASA's Jet Propulsion Laboratory TRMM image by Tom Bridgman, Goddard SVS; data courtesy TRMM Science Team at NASA's Goddard Space Flight Center

Classification of rainfall events for weather forecasting purposes in andean region of Colombia

NASA Astrophysics Data System (ADS)

Suárez Hincapié, Joan Nathalie; Romo Melo, Liliana; Vélez Upegui, Jorge Julian; Chang, Philippe

2016-04-01

This work presents a comparative analysis of the results of applying different methodologies for the identification and classification of rainfall events of different duration in meteorological records of the Colombian Andean region. In this study the work area is the urban and rural area of Manizales that counts with a monitoring hydro-meteorological network. This network is composed of forty-five (45) strategically located stations, this network is composed of forty-five (45) strategically located stations where automatic weather stations record seven climate variables: air temperature, relative humidity, wind speed and direction, rainfall, solar radiation and barometric pressure. All this information is sent wirelessly every five (5) minutes to a data warehouse located at the Institute of Environmental Studies-IDEA. With obtaining the series of rainfall recorded by the hydrometeorological station Palogrande operated by the National University of Colombia in Manizales (http://froac.manizales.unal.edu.co/bodegaIdea/); it is with this information that we proceed to perform behavior analysis of other meteorological variables, monitored at surface level and that influence the occurrence of such rainfall events. To classify rainfall events different methodologies were used: The first according to Monjo (2009) where the index n of the heavy rainfall was calculated through which various types of precipitation are defined according to the intensity variability. A second methodology that permitted to produce a classification in terms of a parameter β introduced by Rice and Holmberg (1973) and adapted by Llasat and Puigcerver, (1985, 1997) and the last one where a rainfall classification is performed according to the value of its intensity following the issues raised by Linsley (1977) where the rains can be considered light, moderate and strong fall rates to 2.5 mm / h; from 2.5 to 7.6 mm / h and above this value respectively for the previous classifications. The main contribution which is done with this research is the obtainment elements to optimize and to improve the spatial resolution of the results obtained with mesoscale models such as the Weather Research & Forecasting Model- WRF, used in Colombia for the purposes of weather forecasting and that in addition produces other tools used in current issues such as risk management.

Climate Effects on Corn Yield in Missouri(.

NASA Astrophysics Data System (ADS)

Hu, Qi; Buyanovsky, Gregory

2003-11-01

Understanding climate effects on crop yield has been a continuous endeavor aiming at improving farming technology and management strategy, minimizing negative climate effects, and maximizing positive climate effects on yield. Many studies have examined climate effects on corn yield in different regions of the United States. However, most of those studies used yield and climate records that were shorter than 10 years and were for different years and localities. Although results of those studies showed various influences of climate on corn yield, they could be time specific and have been difficult to use for deriving a comprehensive understanding of climate effects on corn yield. In this study, climate effects on corn yield in central Missouri are examined using unique long-term (1895 1998) datasets of both corn yield and climate. Major results show that the climate effects on corn yield can only be explained by within-season variations in rainfall and temperature and cannot be distinguished by average growing-season conditions. Moreover, the growing-season distributions of rainfall and temperature for high-yield years are characterized by less rainfall and warmer temperature in the planting period, a rapid increase in rainfall, and more rainfall and warmer temperatures during germination and emergence. More rainfall and cooler-than-average temperatures are key features in the anthesis and kernel-filling periods from June through August, followed by less rainfall and warmer temperatures during the September and early October ripening time. Opposite variations in rainfall and temperature in the growing season correspond to low yield. Potential applications of these results in understanding how climate change may affect corn yield in the region also are discussed.

Rainfall and temperature changes and variability in the Upper East Region of Ghana

NASA Astrophysics Data System (ADS)

Issahaku, Abdul-Rahaman; Campion, Benjamin Betey; Edziyie, Regina

2016-08-01

The aim of the research was to assess the current trend and variation in rainfall and temperature in the Upper East Region, Ghana, using time series moving average analysis and decomposition methods. Meteorological data obtained from the Ghana Meteorological Agency in Accra, Ghana, from 1954 to 2014 were used in the models. The additive decomposition model was used to analyze the rainfall because the seasonal variation was relatively constant over time, while the multiplicative model was used for both the daytime and nighttime temperatures because their seasonal variations increase over time. The monthly maximum and the minimum values for the entire period were as follows: rainfall 455.50 and 0.00 mm, nighttime temperature 29.10°C and 13.25°C and daytime temperature 41.10°C and 26.10°C, respectively. Also, while rainfall was decreasing, nighttime and daytime temperatures were increasing in decadal times. Since both the daytime and nighttime temperatures were increasing and rainfall was decreasing, climate extreme events such as droughts could result and affect agriculture in the region, which is predominantly rain fed. Also, rivers, dams, and dugouts are likely to dry up in the region. It was also observed that there was much variation in rainfall making prediction difficult. Day temperatures were generally high with the months of March and April have been the highest. The months of December recorded the lowest night temperature. Inhabitants are therefore advised to sleep in well-ventilated rooms during the warmest months and wear protective clothing during the cold months to avoid contracting climate-related diseases.

A reexamination of the emergy input to a system from the wind

EPA Science Inventory

With the establishment of a new, rigorously-determined, solar equivalence baseline for the geobiosphere, 12.0E+24 seJ y-1, it is now appropriate to reexamine the calculation of the emergy delivered by the major secondary products of the geobiosphere, e.g., wind and rainfall, whi...

Climate change in Bangladesh: a spatio-temporal analysis and simulation of recent temperature and rainfall data using GIS and time series analysis model

NASA Astrophysics Data System (ADS)

Rahman, Md. Rejaur; Lateh, Habibah

2017-04-01

In this paper, temperature and rainfall data series were analysed from 34 meteorological stations distributed throughout Bangladesh over a 40-year period (1971 to 2010) in order to evaluate the magnitude of these changes statistically and spatially. Linear regression, coefficient of variation, inverse distance weighted interpolation techniques and geographical information systems were performed to analyse the trends, variability and spatial patterns of temperature and rainfall. Autoregressive integrated moving average time series model was used to simulate the temperature and rainfall data. The results confirm a particularly strong and recent climate change in Bangladesh with a 0.20 °C per decade upward trend of mean temperature. The highest upward trend in minimum temperature (range of 0.80-2.4 °C) was observed in the northern, northwestern, northeastern, central and central southern parts while greatest warming in the maximum temperature (range of 1.20-2.48 °C) was found in the southern, southeastern and northeastern parts during 1971-2010. An upward trend of annual rainfall (+7.13 mm per year) and downward pre-monsoon (-0.75 mm per year) and post-monsoon rainfall (-0.55 mm per year) trends were observed during this period. Rainfall was erratic in pre-monsoon season and even more so during the post-monsoon season (variability of 44.84 and 85.25 % per year, respectively). The mean forecasted temperature exhibited an increase of 0.018 °C per year in 2011-2020, and if this trend continues, this would lead to approximately 1.0 °C warmer temperatures in Bangladesh by 2020, compared to that of 1971. A greater rise is projected for the mean minimum (0.20 °C) than the mean maximum (0.16 °C) temperature. Annual rainfall is projected to decline 153 mm from 2011 to 2020, and a drying condition will persist in the northwestern, western and southwestern parts of the country during the pre- and post-monsoonal seasons.

A Mediterranean nocturnal heavy rainfall and tornadic event. Part I: Overview, damage survey and radar analysis

NASA Astrophysics Data System (ADS)

Bech, Joan; Pineda, Nicolau; Rigo, Tomeu; Aran, Montserrat; Amaro, Jéssica; Gayà, Miquel; Arús, Joan; Montanyà, Joan; der Velde, Oscar van

2011-06-01

This study presents an analysis of a severe weather case that took place during the early morning of the 2nd of November 2008, when intense convective activity associated with a rapidly evolving low pressure system affected the southern coast of Catalonia (NE Spain). The synoptic framework was dominated by an upper level trough and an associated cold front extending from Gibraltar along the Mediterranean coast of the Iberian Peninsula to SE France, which moved north-eastward. South easterly winds in the north of the Balearic Islands and the coast of Catalonia favoured high values of 0-3 km storm relative helicity which combined with moderate MLCAPE values and high shear favoured the conditions for organized convection. A number of multicell storms and others exhibiting supercell features, as indicated by Doppler radar observations, clustered later in a mesoscale convective system, and moved north-eastwards across Catalonia. They produced ground-level strong damaging wind gusts, an F2 tornado, hail and heavy rainfall. Total lightning activity (intra-cloud and cloud to ground flashes) was also relevant, exhibiting several classical features such as a sudden increased rate before ground level severe damage, as discussed in a companion study. Remarkable surface observations of this event include 24 h precipitation accumulations exceeding 100 mm in four different observatories and 30 minute rainfall amounts up to 40 mm which caused local flash floods. As the convective system evolved northward later that day it also affected SE France causing large hail, ground level damaging wind gusts and heavy rainfall.

The impact of meteorology on the occurrence of waterborne outbreaks of vero cytotoxin-producing Escherichia coli (VTEC): a logistic regression approach.

PubMed

O'Dwyer, Jean; Morris Downes, Margaret; Adley, Catherine C

2016-02-01

This study analyses the relationship between meteorological phenomena and outbreaks of waterborne-transmitted vero cytotoxin-producing Escherichia coli (VTEC) in the Republic of Ireland over an 8-year period (2005-2012). Data pertaining to the notification of waterborne VTEC outbreaks were extracted from the Computerised Infectious Disease Reporting system, which is administered through the national Health Protection Surveillance Centre as part of the Health Service Executive. Rainfall and temperature data were obtained from the national meteorological office and categorised as cumulative rainfall, heavy rainfall events in the previous 7 days, and mean temperature. Regression analysis was performed using logistic regression (LR) analysis. The LR model was significant (p < 0.001), with all independent variables: cumulative rainfall, heavy rainfall and mean temperature making a statistically significant contribution to the model. The study has found that rainfall, particularly heavy rainfall in the preceding 7 days of an outbreak, is a strong statistical indicator of a waterborne outbreak and that temperature also impacts waterborne VTEC outbreak occurrence.

Impacts of rainfall and air temperature variations due to climate change upon hydrological characteristics: A case study

Treesearch

Ying Ouyang; Jia-En Zhang; Yide Li; Prem Parajuli; Gary Feng

2015-01-01

Rainfall and air temperature variations resulting from climate change are important driving forces to change hydrologic processes in watershed ecosystems. This study investigated the impacts of past and future rainfall and air temperature variations upon water discharge, water outflow (from the watershed outlet), and evaporative loss in the Lower Yazoo River Watershed...

Coastal circulation and water-column properties in the War in the Pacific National Historical Park, Guam: measurements and modeling of waves, currents, temperature, salinity, and turbidity, April-August 2012

USGS Publications Warehouse

Storlazzi, Curt D.; Cheriton, Olivia M.; Lescinski, Jamie M.R.; Logan, Joshua B.

2014-01-01

The U.S. Geological Survey (USGS) Pacific Coastal and Marine Science Center (PCMSC) initiated an investigation in the National Park Service’s (NPS) War in the Pacific National Historical Park (WAPA) to provide baseline scientific information on coastal circulation and water-column properties along west-central Guam, focusing on WAPA’s Agat Unit, as it relates to the transport and settlement of coral larvae, fish, and other marine organisms. The oceanographic data and numerical circulation modeling results from this study demonstrate that circulation in Agat Bay was strongly driven by winds and waves at longer (>1 day) timescales and by the tides at shorter (<1 day) timescales; near-surface currents in deep water were primarily controlled by the winds, whereas currents on the shallow reef flats were dominated by wave-driven motions. Water-column properties exhibited strong seasonality coupled to the shift from the trade wind to the non-trade wind season. During the dry trade-wind season, waters were cooler and more saline. When the winds shifted to a more variable pattern, waters warmed and became less saline because of a combination of increased thermal insolation from lack of wind forcing and higher rainfall. Turbidity was relatively low in Agat Bay and was similar to levels measured elsewhere along west-central Guam. The numerical circulation modeling results provide insight into the potential paths of buoyant material released from a series of locations along west-central Guam under summer non-trade wind forcing conditions that characterize coral spawning events. This information may be useful in evaluating the potential zones of influence/impact resulting from transport by surface currents of material released from these select locations.

A simplified diagnostic model of orographic rainfall for enhancing satellite-based rainfall estimates in data-poor regions

USGS Publications Warehouse

Funk, Christopher C.; Michaelsen, Joel C.

2004-01-01

An extension of Sinclair's diagnostic model of orographic precipitation (“VDEL”) is developed for use in data-poor regions to enhance rainfall estimates. This extension (VDELB) combines a 2D linearized internal gravity wave calculation with the dot product of the terrain gradient and surface wind to approximate terrain-induced vertical velocity profiles. Slope, wind speed, and stability determine the velocity profile, with either sinusoidal or vertically decaying (evanescent) solutions possible. These velocity profiles replace the parameterized functions in the original VDEL, creating VDELB, a diagnostic accounting for buoyancy effects. A further extension (VDELB*) uses an on/off constraint derived from reanalysis precipitation fields. A validation study over 365 days in the Pacific Northwest suggests that VDELB* can best capture seasonal and geographic variations. A new statistical data-fusion technique is presented and is used to combine VDELB*, reanalysis, and satellite rainfall estimates in southern Africa. The technique, matched filter regression (MFR), sets the variance of the predictors equal to their squared correlation with observed gauge data and predicts rainfall based on the first principal component of the combined data. In the test presented here, mean absolute errors from the MFR technique were 35% lower than the satellite estimates alone. VDELB assumes a linear solution to the wave equations and a Boussinesq atmosphere, and it may give unrealistic responses under extreme conditions. Nonetheless, the results presented here suggest that diagnostic models, driven by reanalysis data, can be used to improve satellite rainfall estimates in data-sparse regions.

Climatological characteristics of raindrop size distributions within a topographically complex area

NASA Astrophysics Data System (ADS)

Suh, S.-H.; You, C.-H.; Lee, D.-I.

2015-04-01

Raindrop size distribution (DSD) characteristics within the complex area of Busan, Korea (35.12° N, 129.10° E) were studied using a Precipitation Occurrence Sensor System (POSS) disdrometer over a four-year period from 24 February 2001 to 24 December 2004. Average DSD parameters in Busan, a mid-latitude site, were compared with corresponding parameters recorded in the high-latitude site of Järvenpää, Finland. Mean values of median drop diameter (D0) and the shape parameter (μ) in Busan are smaller than those in Järvenpää, whereas the mean normalized intercept parameter (Nw) and rainfall rate (R) are higher in Busan. To analyze the climatological DSD characteristics in more detail, the entire period of recorded rainfall was divided into 10 categories with different temporal and spatial scales. When only convective rainfall was considered, mean Dm and Nw values for all these categories converged around a maritime cluster, except for rainfall associated with typhoons. The convective rainfall of a typhoon showed much smaller Dm and larger Nw compared with the other rainfall categories. In terms of diurnal DSD variability, we observe maritime (continental) precipitation during the daytime (DT) (nighttime, NT), which likely results from sea (land) breeze identified through wind direction analysis. These features also appeared in the seasonal diurnal distribution. The DT and NT Probability Density Function (PDF) during the summer was similar to the PDF of the entire study period. However, the DT and NT PDF during the winter season displayed an inverse distribution due to seasonal differences in wind direction.

[Paleoclimate of La Guajira, Colombia; by the growth rings of Capparis odoratissima (Capparidaceae)].

PubMed

Ramírez, Jorge Andrés; Ignacio del Valle, Jorge

2011-09-01

There is great concern about the effect of climate change in arid and subarid areas of the tropics. Climate change combined with other anthropogenic activities such as deforestation, fires and over-grazing can accelerate their degradation and, consequently, the increases in losses of biological and economic productivity. Climate models, both local and global, predict that rainfall in the arid Peninsula of La Guajira in the Colombian Caribbean would be reduced and temperature would be increased as a result of climate change. However, as there are only suitable climate records since 1972, it is not possible to verify if, indeed, this is happening. To try to verify the hypothesis of reducing rainfall and rising temperatures we developed a growth ring chronology of Capparis odoratissima in the Middle Peninsula of La Guajira with 17 trees and 45 series which attain 48 years back. We use standard dendrochronological methods that showed statistically significant linear relationship with local climatic variables such as air temperature, sea surface temperature (SST), annual precipitation and wind speed; we also reach to successful relationship of the chronology with global climatic variables as the indices SOI and MEI of the ENSO phenomenon. The transfer functions estimated with the time series (1955 and 2003) do not showed statistically significant trends, indicating that during this period of time the annual precipitation or temperatures have not changed. The annual nature of C. odoratissima growth rings, the possibility of cross-dated among the samples of this species, and the high correlation with local and global climatic variables indicate a high potential of this species for dendrochronological studies in this part of the American continent.

Climate change impacts on rainfall and temperature in sugarcane growing Upper Gangetic Plains of India

NASA Astrophysics Data System (ADS)

Verma, Ram Ratan; Srivastava, Tapendra Kumar; Singh, Pushpa

2018-01-01

Assessment of variability in climate extremes is crucial for managing their aftermath on crops. Sugarcane (Saccharum officinarum L.), a major C4 crop, dominates the Upper Gangetic Plain (UGP) in India and is vulnerable to both direct and indirect effects of changes in temperature and rainfall. The present study was taken up to assess the weekly, monthly, seasonal, and annual trends of rainfall and temperature variability during the period 1956-2015 (60 years) for envisaging the probabilities of different levels of rainfall suitable for sugarcane in UGP in the present climate scenario. The analysis revealed that 87% of total annual rainfall was received during southwest monsoon months (June-September) while post-monsoon (October to February) and pre-monsoon months (March-May) accounted for only 9.4 and 3.6%, respectively. There was a decline in both monthly and annual normal rainfall during the period 1986-2015 as compared to 1956-1985, and an annual rainfall deficiency of 205.3 mm was recorded. Maximum monthly normal rainfall deficiencies of 52.8, 84.2, and 54.0 mm were recorded during the months of July, August, and September, respectively, while a minimum rainfall deficiency of 2.2 mm was observed in November. There was a decline by 196.3 mm in seasonal normal rainfall during June-September (kharif). The initial probability of a week going dry was higher (> 70%) from the 1st to the 25th week; however, standard meteorological weeks (SMW) 26 to 37 had more than 50% probability of going wet. The normal annual maximum temperature (Tmax) decreased by 0.4 °C while normal annual minimum temperatures (Tmin) increased by 0.21 °C. Analysis showed that there was an increase in frequency of drought from 1986 onwards in the zone and a monsoon rainfall deficit by about 21.25% during June-September which coincided with tillering and grand growth stage of sugarcane. The imposed drought during the growth and elongation phase is emerging as a major constraint in realizing high cane productivity in the zone. Strategies for mitigating the negative impacts of rainfall and temperature variability on sugarcane productivity through improvement in existing adaptation strategies are proposed.

Climate-change driven increase in high intensity rainfall events: Analysis of development in the last decades and towards an extrapolation of future progression

NASA Astrophysics Data System (ADS)

Müller, Eva; Pfister, Angela; Gerd, Büger; Maik, Heistermann; Bronstert, Axel

2015-04-01

Hydrological extreme events can be triggered by rainfall on different spatiotemporal scales: river floods are typically caused by event durations of between hours and days, while urban flash floods as well as soil erosion or contaminant transport rather result from storms events of very short duration (minutes). Still, the analysis of climate change impacts on rainfall-induced extreme events is usually carried out using daily precipitation data at best. Trend analyses of extreme rainfall at sub-daily or even sub-hourly time scales are rare. In this contribution two lines of research are combined: first, we analyse sub-hourly rainfall data for several decades in three European regions.Second, we investigate the scaling behaviour of heavy short-term precipitation with temperature, i.e. the dependence of high intensity rainfall on the atmospheric temperature at that particular time and location. The trend analysis of high-resolution rainfall data shows for the first time that the frequency of short and intensive storm events in the temperate lowland regions in Germany has increased by up to 0.5 events per year over the last decades. I.e. this trend suggests that the occurrence of these types of storms have multiplied over only a few decades. Parallel to the changes in the rainfall regime, increases in the annual and seasonal average temperature and changes in the occurrence of circulation patterns responsible for the generation of high-intensity storms have been found. The analysis of temporally highly resolved rainfall records from three European regions further indicates that extreme precipitation events are more intense with warmer temperatures during the rainfall event. These observations follow partly the Clausius-Clapeyron relation. Based on this relation one may derive a general rule of maximum rainfall intensity associated to the event temperature, roughly following the Clausius-Clapeyron (CC) relation. This rule might be used for scenarios of future maximum rainfall intensities under a warming climate.

Wavelet Scale Analysis of Mesoscale Convective Systems for Detecting Deep Convection From Infrared Imagery

NASA Astrophysics Data System (ADS)

Klein, Cornelia; Belušić, Danijel; Taylor, Christopher M.

2018-03-01

Mesoscale convective systems (MCSs) are frequently associated with rainfall extremes and are expected to further intensify under global warming. However, despite the significant impact of such extreme events, the dominant processes favoring their occurrence are still under debate. Meteosat geostationary satellites provide unique long-term subhourly records of cloud top temperatures, allowing to track changes in MCS structures that could be linked to rainfall intensification. Focusing on West Africa, we show that Meteosat cloud top temperatures are a useful proxy for rainfall intensities, as derived from snapshots from the Tropical Rainfall Measuring Mission 2A25 product: MCSs larger than 15,000 km2 at a temperature threshold of -40°C are found to produce 91% of all extreme rainfall occurrences in the study region, with 80% of the storms producing extreme rain when their minimum temperature drops below -80°C. Furthermore, we present a new method based on 2-D continuous wavelet transform to explore the relationship between cloud top temperature and rainfall intensity for subcloud features at different length scales. The method shows great potential for separating convective and stratiform cloud parts when combining information on temperature and scale, improving the common approach of using a temperature threshold only. We find that below -80°C, every fifth pixel is associated with deep convection. This frequency is doubled when looking at subcloud features smaller than 35 km. Scale analysis of subcloud features can thus help to better exploit cloud top temperature data sets, which provide much more spatiotemporal detail of MCS characteristics than available rainfall data sets alone.

Use of a scenario-neutral approach to identify the key hydro-meteorological attributes that impact runoff from a natural catchment

NASA Astrophysics Data System (ADS)

Guo, Danlu; Westra, Seth; Maier, Holger R.

2017-11-01

Scenario-neutral approaches are being used increasingly for assessing the potential impact of climate change on water resource systems, as these approaches allow the performance of these systems to be evaluated independently of climate change projections. However, practical implementations of these approaches are still scarce, with a key limitation being the difficulty of generating a range of plausible future time series of hydro-meteorological data. In this study we apply a recently developed inverse stochastic generation approach to support the scenario-neutral analysis, and thus identify the key hydro-meteorological variables to which the system is most sensitive. The stochastic generator simulates synthetic hydro-meteorological time series that represent plausible future changes in (1) the average, extremes and seasonal patterns of rainfall; and (2) the average values of temperature (Ta), relative humidity (RH) and wind speed (uz) as variables that drive PET. These hydro-meteorological time series are then fed through a conceptual rainfall-runoff model to simulate the potential changes in runoff as a function of changes in the hydro-meteorological variables, and runoff sensitivity is assessed with both correlation and Sobol' sensitivity analyses. The method was applied to a case study catchment in South Australia, and the results showed that the most important hydro-meteorological attributes for runoff were winter rainfall followed by the annual average rainfall, while the PET-related meteorological variables had comparatively little impact. The high importance of winter rainfall can be related to the winter-dominated nature of both the rainfall and runoff regimes in this catchment. The approach illustrated in this study can greatly enhance our understanding of the key hydro-meteorological attributes and processes that are likely to drive catchment runoff under a changing climate, thus enabling the design of tailored climate impact assessments to specific water resource systems.

Interannual rainfall variability and SOM-based circulation classification

NASA Astrophysics Data System (ADS)

Wolski, Piotr; Jack, Christopher; Tadross, Mark; van Aardenne, Lisa; Lennard, Christopher

2018-01-01

Self-Organizing Maps (SOM) based classifications of synoptic circulation patterns are increasingly being used to interpret large-scale drivers of local climate variability, and as part of statistical downscaling methodologies. These applications rely on a basic premise of synoptic climatology, i.e. that local weather is conditioned by the large-scale circulation. While it is clear that this relationship holds in principle, the implications of its implementation through SOM-based classification, particularly at interannual and longer time scales, are not well recognized. Here we use a SOM to understand the interannual synoptic drivers of climate variability at two locations in the winter and summer rainfall regimes of South Africa. We quantify the portion of variance in seasonal rainfall totals that is explained by year to year differences in the synoptic circulation, as schematized by a SOM. We furthermore test how different spatial domain sizes and synoptic variables affect the ability of the SOM to capture the dominant synoptic drivers of interannual rainfall variability. Additionally, we identify systematic synoptic forcing that is not captured by the SOM classification. The results indicate that the frequency of synoptic states, as schematized by a relatively disaggregated SOM (7 × 9) of prognostic atmospheric variables, including specific humidity, air temperature and geostrophic winds, captures only 20-45% of interannual local rainfall variability, and that the residual variance contains a strong systematic component. Utilising a multivariate linear regression framework demonstrates that this residual variance can largely be explained using synoptic variables over a particular location; even though they are used in the development of the SOM their influence, however, diminishes with the size of the SOM spatial domain. The influence of the SOM domain size, the choice of SOM atmospheric variables and grid-point explanatory variables on the levels of explained variance, is consistent with the general understanding of the dominant processes and atmospheric variables that affect rainfall variability at a particular location.

Decrease of tropical cyclone genesis frequency in the western North Pacific since 1960s

NASA Astrophysics Data System (ADS)

Hu, Feng; Li, Tim; Liu, Jia; Bi, Mingyu; Peng, Melinda

2018-03-01

Tropical cyclone (TC) genesis frequency in the western North Pacific (WNP) during 1960-2014 shows a step-by-step decrease on interdecadal timescale, in accordance to the phase of the Interdecadal Pacific Oscillation (IPO). The environmental parameters responsible for the interdecadal change of TC genesis frequency were investigated. It was found that vertical wind shear especially the zonal wind shear plays a critical role, while other parameters such as sea surface temperature (SST), vertical velocity, divergence, humidity and maximum potential intensity cannot explain the step-by-step decrease of TC genesis frequency. A further diagnosis shows that the interdecadal change of vertical wind shear is caused by SST and associated rainfall pattern changes across the Indo-Pacific Ocean. A stronger warming in the Indian Ocean/western Pacific from 1960-1976 to 1977-1998 led to enhanced convection over the Maritime Continent and thus strengthened vertical shear over the key TC genesis region in the WNP. A La Nina-like SST pattern change from 1977-1998 to 1999-2014 led to a strengthened Walker circulation in the tropical Pacific, which further enhanced the vertical shear and decreased TC genesis frequency in the WNP.

Spatiotemporal trends in extreme rainfall and temperature indices over Upper Tapi Basin, India

NASA Astrophysics Data System (ADS)

Sharma, Priyank J.; Loliyana, V. D.; S. R., Resmi; Timbadiya, P. V.; Patel, P. L.

2017-12-01

The flood risk across the globe is intensified due to global warming and subsequent increase in extreme temperature and precipitation. The long-term trends in extreme rainfall (1944-2013) and temperature (1969-2012) indices have been investigated at annual, seasonal, and monthly time scales using nonparametric Mann-Kendall (MK), modified Mann-Kendall (MMK), and Sen's slope estimator tests. The extreme rainfall and temperature indices, recommended by the Expert Team on Climate Change Detection Monitoring Indices (ETCCDMI), have been analyzed at finer spatial scales for trend detection. The results of trend analyses indicate decreasing trend in annual total rainfall, significant decreasing trend in rainy days, and increasing trend in rainfall intensity over the basin. The seasonal rainfall has been found to decrease for all the seasons except postmonsoon, which could affect the rain-fed agriculture in the basin. The 1- and 5-day annual maximum rainfalls exhibit mixed trends, wherein part of the basin experiences increasing trend, while other parts experience a decreasing trend. The increase in dry spells and concurrent decrease in wet spells are also observed over the basin. The extreme temperature indices revealed increasing trends in hottest and coldest days, while decreasing trends in coldest night are found over most parts of the basin. Further, the diurnal temperature range is also found to increase due to warming tendency in maximum temperature (T max) at a faster rate compared to the minimum temperature (T min). The increase in frequency and magnitude of extreme rainfall in the basin has been attributed to the increasing trend in maximum and minimum temperatures, reducing forest cover, rapid pace of urbanization, increase in human population, and thereby increase in the aerosol content in the atmosphere. The findings of the present study would significantly help in sustainable water resource planning, better decision-making for policy framework, and setting up infrastructure against flood disasters in Upper Tapi Basin, India.

Sensitivity of peak flow to the change of rainfall temporal pattern due to warmer climate

NASA Astrophysics Data System (ADS)

Fadhel, Sherien; Rico-Ramirez, Miguel Angel; Han, Dawei

2018-05-01

The widely used design storms in urban drainage networks has different drawbacks. One of them is that the shape of the rainfall temporal pattern is fixed regardless of climate change. However, previous studies have shown that the temporal pattern may scale with temperature due to climate change, which consequently affects peak flow. Thus, in addition to the scaling of the rainfall volume, the scaling relationship for the rainfall temporal pattern with temperature needs to be investigated by deriving the scaling values for each fraction within storm events, which is lacking in many parts of the world including the UK. Therefore, this study analysed rainfall data from 28 gauges close to the study area with a 15-min resolution as well as the daily temperature data. It was found that, at warmer temperatures, the rainfall temporal pattern becomes less uniform, with more intensive peak rainfall during higher intensive times and weaker rainfall during less intensive times. This is the case for storms with and without seasonal separations. In addition, the scaling values for both the rainfall volume and the rainfall fractions (i.e. each segment of rainfall temporal pattern) for the summer season were found to be higher than the corresponding results for the winter season. Applying the derived scaling values for the temporal pattern of the summer season in a hydrodynamic sewer network model produced high percentage change of peak flow between the current and future climate. This study on the scaling of rainfall fractions is the first in the UK, and its findings are of importance to modellers and designers of sewer systems because it can provide more robust scenarios for flooding mitigation in urban areas.

Seasonality of Fire Weather Strongly Influences Fire Regimes in South Florida Savanna-Grassland Landscapes

PubMed Central

Platt, William J.; Orzell, Steve L.; Slocum, Matthew G.

2015-01-01

Fire seasonality, an important characteristic of fire regimes, commonly is delineated using seasons based on single weather variables (rainfall or temperature). We used nonparametric cluster analyses of a 17-year (1993–2009) data set of weather variables that influence likelihoods and spread of fires (relative humidity, air temperature, solar radiation, wind speed, soil moisture) to explore seasonality of fire in pine savanna-grassland landscapes at the Avon Park Air Force Range in southern Florida. A four-variable, three-season model explained more variation within fire weather variables than models with more seasons. The three-season model also delineated intra-annual timing of fire more accurately than a conventional rainfall-based two-season model. Two seasons coincided roughly with dry and wet seasons based on rainfall. The third season, which we labeled the fire season, occurred between dry and wet seasons and was characterized by fire-promoting conditions present annually: drought, intense solar radiation, low humidity, and warm air temperatures. Fine fuels consisting of variable combinations of pyrogenic pine needles, abundant C4 grasses, and flammable shrubs, coupled with low soil moisture, and lightning ignitions early in the fire season facilitate natural landscape-scale wildfires that burn uplands and across wetlands. We related our three season model to fires with different ignition sources (lightning, military missions, and prescribed fires) over a 13-year period with fire records (1997–2009). Largest wildfires originate from lightning and military ignitions that occur within the early fire season substantially prior to the peak of lightning strikes in the wet season. Prescribed ignitions, in contrast, largely occur outside the fire season. Our delineation of a pronounced fire season provides insight into the extent to which different human-derived fire regimes mimic lightning fire regimes. Delineation of a fire season associated with timing of natural lightning ignitions should be useful as a basis for ecological fire management of humid savanna-grassland landscapes worldwide. PMID:25574667

Seasonality of fire weather strongly influences fire regimes in South Florida savanna-grassland landscapes.

PubMed

Platt, William J; Orzell, Steve L; Slocum, Matthew G

2015-01-01

Fire seasonality, an important characteristic of fire regimes, commonly is delineated using seasons based on single weather variables (rainfall or temperature). We used nonparametric cluster analyses of a 17-year (1993-2009) data set of weather variables that influence likelihoods and spread of fires (relative humidity, air temperature, solar radiation, wind speed, soil moisture) to explore seasonality of fire in pine savanna-grassland landscapes at the Avon Park Air Force Range in southern Florida. A four-variable, three-season model explained more variation within fire weather variables than models with more seasons. The three-season model also delineated intra-annual timing of fire more accurately than a conventional rainfall-based two-season model. Two seasons coincided roughly with dry and wet seasons based on rainfall. The third season, which we labeled the fire season, occurred between dry and wet seasons and was characterized by fire-promoting conditions present annually: drought, intense solar radiation, low humidity, and warm air temperatures. Fine fuels consisting of variable combinations of pyrogenic pine needles, abundant C4 grasses, and flammable shrubs, coupled with low soil moisture, and lightning ignitions early in the fire season facilitate natural landscape-scale wildfires that burn uplands and across wetlands. We related our three season model to fires with different ignition sources (lightning, military missions, and prescribed fires) over a 13-year period with fire records (1997-2009). Largest wildfires originate from lightning and military ignitions that occur within the early fire season substantially prior to the peak of lightning strikes in the wet season. Prescribed ignitions, in contrast, largely occur outside the fire season. Our delineation of a pronounced fire season provides insight into the extent to which different human-derived fire regimes mimic lightning fire regimes. Delineation of a fire season associated with timing of natural lightning ignitions should be useful as a basis for ecological fire management of humid savanna-grassland landscapes worldwide.

The canopy interception-landslide initiation conundrum: insight from a tropical secondary forest in northern Thailand

NASA Astrophysics Data System (ADS)

Sidle, Roy C.; Ziegler, Alan D.

2017-01-01

The interception and smoothing effect of forest canopies on pulses of incident rainfall and its delivery to the soil has been suggested as a factor in moderating peak pore water pressure in soil mantles, thus reducing the risk of shallow landslides. Here we provide 3 years of rainfall and throughfall data in a tropical secondary dipterocarp forest characterized by few large trees in northern Thailand, along with selected soil moisture dynamics, to address this issue. Throughfall was an estimated 88 % of rainfall, varying from 86 to 90 % in individual years. Data from 167 events demonstrate that canopy interception was only weakly associated (via a nonlinear relationship) with total event rainfall, but not significantly correlated with duration, mean intensity, or antecedent 2-day precipitation (API2). Mean interception during small events (≤ 35 mm) was 17 % (n = 135 events) compared with only 7 % for large events (> 35 mm; n = 32). Examining small temporal intervals within the largest and highest intensity events that would potentially trigger landslides revealed complex patterns of interception. The tropical forest canopy had little smoothing effect on incident rainfall during the largest events. During events with high peak intensities, high wind speeds, and/or moderate-to-high pre-event wetting, measured throughfall was occasionally higher than rainfall during large event peaks, demonstrating limited buffering. However, in events with little wetting and low-to-moderate wind speed, early event rainfall peaks were buffered by the canopy. As rainfall continued during most large events, there was little difference between rainfall and throughfall depths. A comparison of both rainfall and throughfall depths to conservative mean intensity-duration thresholds for landslide initiation revealed that throughfall exceeded the threshold in 75 % of the events in which rainfall exceeded the threshold for both wet and dry conditions. Throughfall intensity for the 11 largest events (rainfall = 65-116 mm) plotted near or above the intensity-duration threshold for landslide initiation during wet conditions; 5 of the events were near or above the threshold for dry conditions. Soil moisture responses during large events were heavily and progressively buffered at depths of 1 to 2 m, indicating that the timescale of any short-term smoothing of peak rainfall inputs (i.e., ≤ 1 h) has little influence on peak pore water pressure at depths where landslides would initiate in this area. Given these findings, we conclude that canopy interception would have little effect on mitigating shallow landslide initiation during the types of monsoon rainfall conditions in this and similar tropical secondary forest sites.

Comparison of wind tunnel and field experiments to measure potential deposition of fenpropimorph following volatilisation from treated crops.

PubMed

Hassink, Jan; Platz, Klaus; Stadler, Reinhold; Zangmeister, Werner; Fent, Gunnar; Möndel, Martin; Kubiak, Roland

2007-02-01

The potential for short-range transport via air, i.e. volatilisation from the area of application and subsequent deposition on adjacent non-target areas, was investigated for the fungicide fenpropimorph in a wind tunnel system and under outdoor conditions in a higher-tier field study. Fenpropimorph 750 g L(-1) EC was applied post-emergence to cereal along with a reference standard lindane EC. Stainless steel containers of water were placed at different distances downwind of the application area to trap volatile residues during a study period of 24 h following application. Meteorological conditions in the wind tunnel as well as on the field were constantly monitored during the study period. The wind tunnel system was a partly standardised system on a semi-field scale, i.e. wind direction and wind speed (2 m s(-1)) were constant, but temperature and humidity varied according to the conditions outside. In the field experiment, the average wind speed over the 24 h study period was 3 m s(-1) and no rainfall occurred. Three different measuring lines were installed on the non-target area beside the treated field to cover potential variations in the wind direction. However, no significant differences were observed since the wind direction was generally constant. Fenpropimorph was detected in minor amounts of 0.01-0.05% of the applied material in the wind tunnel experiment. Even at a distance of 1 m beside the treated field, no significant deposition occurred (0.04% of applied material after 24 h). In the field, less than 0.1% of the applied fenpropimorph was detected at 0 m directly beside the treated field. At 5 m distance the deposition values were below 0.04%, and at 20 m distance about 0.01%. In general, the amounts of deposited fenpropimorph detected in the partly standardised wind tunnel system and the higher-tier field study were in good agreement.

Cause Resolving of Typhoon Precipitation Using Principle Component Analysis under Complex Interactive Effect of Terrain, Monsoon and Typhoon Vortex

NASA Astrophysics Data System (ADS)

Huang, C. L.; Hsu, N. S.

2015-12-01

This study develops a novel methodology to resolve the cause of typhoon-induced precipitation using principle component analysis (PCA) and to develop a long lead-time precipitation prediction model. The discovered spatial and temporal features of rainfall are utilized to develop a state-of-the-art descriptive statistical model which can be used to predict long lead-time precipitation during typhoons. The time series of 12-hour precipitation from different types of invasive moving track of typhoons are respectively precede the signal analytical process to qualify the causes of rainfall and to quantify affected degree of each induced cause. The causes include: (1) interaction between typhoon rain band and terrain; (2) co-movement effect induced by typhoon wind field with monsoon; (3) pressure gradient; (4) wind velocity; (5) temperature environment; (6) characteristic distance between typhoon center and surface target station; (7) distance between grade 7 storm radius and surface target station; and (8) relative humidity. The results obtained from PCA can detect the hidden pattern of the eight causes in space and time and can understand the future trends and changes of precipitation. This study applies the developed methodology in Taiwan Island which is constituted by complex diverse terrain formation and height. Results show that: (1) for the typhoon moving toward the direction of 245° to 330°, Causes (1), (2) and (6) are the primary ones to generate rainfall; and (2) for the direction of 330° to 380°, Causes (1), (4) and (6) are the primary ones. Besides, the developed precipitation prediction model by using PCA with the distributed moving track approach (PCA-DMT) is 32% more accurate by that of PCA without distributed moving track approach, and the former model can effectively achieve long lead-time precipitation prediction with an average predicted error of 13% within average 48 hours of forecasted lead-time.

Ecological covariates based predictive model of malaria risk in the state of Chhattisgarh, India.

PubMed

Kumar, Rajesh; Dash, Chinmaya; Rani, Khushbu

2017-09-01

Malaria being an endemic disease in the state of Chhattisgarh and ecologically dependent mosquito-borne disease, the study is intended to identify the ecological covariates of malaria risk in districts of the state and to build a suitable predictive model based on those predictors which could assist developing a weather based early warning system. This secondary data based analysis used one month lagged district level malaria positive cases as response variable and ecological covariates as independent variables which were tested with fixed effect panelled negative binomial regression models. Interactions among the covariates were explored using two way factorial interaction in the model. Although malaria risk in the state possesses perennial characteristics, higher parasitic incidence was observed during the rainy and winter seasons. The univariate analysis indicated that the malaria incidence risk was statistically significant associated with rainfall, maximum humidity, minimum temperature, wind speed, and forest cover ( p  < 0.05). The efficient predictive model include the forest cover [IRR-1.033 (1.024-1.042)], maximum humidity [IRR-1.016 (1.013-1.018)], and two-way factorial interactions between district specific averaged monthly minimum temperature and monthly minimum temperature, monthly minimum temperature was statistically significant [IRR-1.44 (1.231-1.695)] whereas the interaction term has a protective effect [IRR-0.982 (0.974-0.990)] against malaria infections. Forest cover, maximum humidity, minimum temperature and wind speed emerged as potential covariates to be used in predictive models for modelling the malaria risk in the state which could be efficiently used for early warning systems in the state.

Abiotic factors and trap design modulate the performance of traps used to monitor the plum curculio.

PubMed

Lamothe, Steve; Chouinard, Gérald; Vincent, Charles

2008-12-01

All published studies on effects of abiotic factors on plum curculio, Conotrachelus nenuphar (Hersbt), adults have taken a retrospective approach. Here, we present the results of experiments where factors and their levels were determined and controlled a priori. We compared the effectiveness of miniature pyramidal traps (45 by 20 by 20 cm) constructed of four kind of materials--wood, geotextile, nylon screening, and corrugated plastic--to monitor overwintered and summer adults of univoltine plum curculio. We also studied the effects of photoperiod, temperature, wind, and rain on pyramidal trap effectiveness. The experiments, which were replicated over time, were done in two controlled chambers that were divided into four sections, corresponding to simulated combinations (wind or no wind/rain or no rain). The temperatures tested (15, 20, and 25 degrees C) were randomly assigned in the chambers. During scotophase, geotextile traps captured significantly more overwintered and summer adults than traps made of other materials. The maximum proportion of captures (for overwintered and summer adults) during photophase was obtained at 25 degrees C, and it was significantly different than captures at 15 and 20 degrees C. During scotophase, significantly more overwintered and summer plum curculios were caught at 20 and 25 degrees C than at 15 degrees C. Our experiments demonstrated that geotextile is a good alternative to wooden pyramidal trap. Our results suggest that captures were higher 1) at night, 2) during warmer periods (20 and 25 degrees C), 3) when wind velocity was low and 4) during or shortly after rainfall, and 5) that photoperiod is a factor having an important predictive value for plum curculio captures.

Oceanic influence on seasonal malaria outbreaks over Senegal and Sahel

NASA Astrophysics Data System (ADS)

Diouf, Ibrahima; Rodríguez de Fonseca, Belen; Deme, Abdoulaye; Cisse Cisse, Moustapha; Ndione Ndione, Jaques-Andre; Gaye, Amadou T.; Suarez, Roberto

2015-04-01

Beyond assessment and analysis of observed and simulated malaria parameters, this study is furthermore undertaken in the framework of predictability of malaria outbreaks in Senegal and remote regions in Sahel, which are found to take place two months after the rainy season. The predictors are the sea surface temperature anomalous patterns at different ocean basins mainly over the Pacific and Atlantic as they are related to changes in air temperature, humidity, rainfall and wind. A relationship between El Niño and anomalous malaria parameters is found. The malaria parameters are calculated with the Liverpool Malaria Model (LMM) using meteorological datasets from different reanalysis products. A hindcast of these parameters is performed using the Sea Surface temperature based Statistical Seasonal ForeCAST (S4CAST) model developed at UCM in order to predict malaria parameters some months in advance. The results of this work will be useful for decision makers to better access to climate forecasts and application on malaria transmission risk.

Geographic patterns of networks derived from extreme precipitation over the Indian subcontinent

NASA Astrophysics Data System (ADS)

Stolbova, Veronika; Bookhagen, Bodo; Marwan, Norbert; Kurths, Juergen

2014-05-01

Complex networks (CN) and event synchronization (ES) methods have been applied to study a number of climate phenomena such as Indian Summer Monsoon (ISM), South-American Monsoon, and African Monsoon. These methods proved to be powerful tools to infer interdependencies in climate dynamics between geographical sites, spatial structures, and key regions of the considered climate phenomenon. Here, we use these methods to study the spatial temporal variability of the extreme rainfall over the Indian subcontinent, in order to filter the data by coarse-graining the network, and to identify geographic patterns that are signature features (spatial signatures) of the ISM. We find four main geographic patterns of networks derived from extreme precipitation over the Indian subcontinent using up-to-date satellite-derived, and high temporal and spatial resolution rain-gauge interpolated daily rainfall datasets. In order to prove that our results are also relevant for other climatic variables like pressure and temperature, we use re-analysis data provided by the National Center for Environmental Prediction and National Center for Atmospheric Research (NCEP/NCAR). We find that two of the patterns revealed from the CN extreme rainfall analysis coincide with those obtained for the pressure and temperature fields, and all four above mentioned patterns can be explained by topography, winds, and monsoon circulation. CN and ES enable to select the most informative regions for the ISM, providing realistic description of the ISM dynamics with fewer data, and also help to infer geographic pattern that are spatial signatures of the ISM. These patterns deserve a special attention for the meteorologists and can be used as markers of the ISM variability.

The influence of meteorology on the spread of influenza: survival analysis of an equine influenza (A/H3N8) outbreak.

PubMed

Firestone, Simon M; Cogger, Naomi; Ward, Michael P; Toribio, Jenny-Ann L M L; Moloney, Barbara J; Dhand, Navneet K

2012-01-01

The influences of relative humidity and ambient temperature on the transmission of influenza A viruses have recently been established under controlled laboratory conditions. The interplay of meteorological factors during an actual influenza epidemic is less clear, and research into the contribution of wind to epidemic spread is scarce. By applying geostatistics and survival analysis to data from a large outbreak of equine influenza (A/H3N8), we quantified the association between hazard of infection and air temperature, relative humidity, rainfall, and wind velocity, whilst controlling for premises-level covariates. The pattern of disease spread in space and time was described using extraction mapping and instantaneous hazard curves. Meteorological conditions at each premises location were estimated by kriging daily meteorological data and analysed as time-lagged time-varying predictors using generalised Cox regression. Meteorological covariates time-lagged by three days were strongly associated with hazard of influenza infection, corresponding closely with the incubation period of equine influenza. Hazard of equine influenza infection was higher when relative humidity was <60% and lowest on days when daily maximum air temperature was 20-25°C. Wind speeds >30 km hour(-1) from the direction of nearby infected premises were associated with increased hazard of infection. Through combining detailed influenza outbreak and meteorological data, we provide empirical evidence for the underlying environmental mechanisms that influenced the local spread of an outbreak of influenza A. Our analysis supports, and extends, the findings of studies into influenza A transmission conducted under laboratory conditions. The relationships described are of direct importance for managing disease risk during influenza outbreaks in horses, and more generally, advance our understanding of the transmission of influenza A viruses under field conditions.

The Influence of Meteorology on the Spread of Influenza: Survival Analysis of an Equine Influenza (A/H3N8) Outbreak

PubMed Central

Firestone, Simon M.; Cogger, Naomi; Ward, Michael P.; Toribio, Jenny-Ann L. M. L.; Moloney, Barbara J.; Dhand, Navneet K.

2012-01-01

The influences of relative humidity and ambient temperature on the transmission of influenza A viruses have recently been established under controlled laboratory conditions. The interplay of meteorological factors during an actual influenza epidemic is less clear, and research into the contribution of wind to epidemic spread is scarce. By applying geostatistics and survival analysis to data from a large outbreak of equine influenza (A/H3N8), we quantified the association between hazard of infection and air temperature, relative humidity, rainfall, and wind velocity, whilst controlling for premises-level covariates. The pattern of disease spread in space and time was described using extraction mapping and instantaneous hazard curves. Meteorological conditions at each premises location were estimated by kriging daily meteorological data and analysed as time-lagged time-varying predictors using generalised Cox regression. Meteorological covariates time-lagged by three days were strongly associated with hazard of influenza infection, corresponding closely with the incubation period of equine influenza. Hazard of equine influenza infection was higher when relative humidity was <60% and lowest on days when daily maximum air temperature was 20–25°C. Wind speeds >30 km hour−1 from the direction of nearby infected premises were associated with increased hazard of infection. Through combining detailed influenza outbreak and meteorological data, we provide empirical evidence for the underlying environmental mechanisms that influenced the local spread of an outbreak of influenza A. Our analysis supports, and extends, the findings of studies into influenza A transmission conducted under laboratory conditions. The relationships described are of direct importance for managing disease risk during influenza outbreaks in horses, and more generally, advance our understanding of the transmission of influenza A viruses under field conditions. PMID:22536366

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns?

PubMed

Ma, Xiaohui; Chang, Ping; Saravanan, R; Montuoro, Raffaele; Hsieh, Jen-Shan; Wu, Dexing; Lin, Xiaopei; Wu, Lixin; Jing, Zhao

2015-12-04

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy-atmosphere interaction in forecast and climate models.

Relative role of pre-monsoon conditions and intraseasonal oscillations in determining early-vs-late indian monsoon intensity in a GCM

NASA Astrophysics Data System (ADS)

Ghosh, Rohit; Chakraborty, Arindam; Nanjundiah, Ravi S.

2018-01-01

The aim of this paper is to identify relative roles of different land-atmospheric conditions, apart from sea surface temperature (SST), in determining early vs. late summer monsoon intensity over India in a high resolution general circulation model (GCM). We find that in its early phase (June-July; JJ), pre-monsoon land-atmospheric processes play major role to modulate the precipitation over Indian region. These effects of pre-monsoon conditions decrease substantially during its later phase (August-September; AS) for which the interannual variation is mainly governed by the low frequency northward propagating intraseasonal oscillations. This intraseasonal variability which is related to mean vertical wind shear has a significant role during the early phase of monsoon as well. Further, using multiple linear regression, we show that interannual variation of early and late monsoon rainfall over India is best explained when all these land-atmospheric parameters are taken together. Our study delineates the relative role of different processes affecting early versus later summer monsoon rainfall over India that can be used for determining its subseasonal predictability.

The impact of mesoscale convective systems on global precipitation: A modeling study

NASA Astrophysics Data System (ADS)

Tao, Wei-Kuo

2017-04-01

The importance of precipitating mesoscale convective systems (MCSs) has been quantified from TRMM precipitation radar and microwave imager retrievals. MCSs generate more than 50% of the rainfall in most tropical regions. Typical MCSs have horizontal scales of a few hundred kilometers (km); therefore, a large domain and high resolution are required for realistic simulations of MCSs in cloud-resolving models (CRMs). Almost all traditional global and climate models do not have adequate parameterizations to represent MCSs. Typical multi-scale modeling frameworks (MMFs) with 32 CRM grid points and 4 km grid spacing also might not have sufficient resolution and domain size for realistically simulating MCSs. In this study, the impact of MCSs on precipitation processes is examined by conducting numerical model simulations using the Goddard Cumulus Ensemble model (GCE) and Goddard MMF (GMMF). The results indicate that both models can realistically simulate MCSs with more grid points (i.e., 128 and 256) and higher resolutions (1 or 2 km) compared to those simulations with less grid points (i.e., 32 and 64) and low resolution (4 km). The modeling results also show that the strengths of the Hadley circulations, mean zonal and regional vertical velocities, surface evaporation, and amount of surface rainfall are either weaker or reduced in the GMMF when using more CRM grid points and higher CRM resolution. In addition, the results indicate that large-scale surface evaporation and wind feed back are key processes for determining the surface rainfall amount in the GMMF. A sensitivity test with reduced sea surface temperatures (SSTs) is conducted and results in both reduced surface rainfall and evaporation.

The Impact of Simulated Mesoscale Convective Systems on Global Precipitation: A Multiscale Modeling Study

NASA Technical Reports Server (NTRS)

Tao, Wei-Kuo; Chern, Jiun-Dar

2017-01-01

The importance of precipitating mesoscale convective systems (MCSs) has been quantified from TRMM precipitation radar and microwave imager retrievals. MCSs generate more than 50% of the rainfall in most tropical regions. MCSs usually have horizontal scales of a few hundred kilometers (km); therefore, a large domain with several hundred km is required for realistic simulations of MCSs in cloud-resolving models (CRMs). Almost all traditional global and climate models do not have adequate parameterizations to represent MCSs. Typical multi-scale modeling frameworks (MMFs) may also lack the resolution (4 km grid spacing) and domain size (128 km) to realistically simulate MCSs. In this study, the impact of MCSs on precipitation is examined by conducting model simulations using the Goddard Cumulus Ensemble (GCE) model and Goddard MMF (GMMF). The results indicate that both models can realistically simulate MCSs with more grid points (i.e., 128 and 256) and higher resolutions (1 or 2 km) compared to those simulations with fewer grid points (i.e., 32 and 64) and low resolution (4 km). The modeling results also show the strengths of the Hadley circulations, mean zonal and regional vertical velocities, surface evaporation, and amount of surface rainfall are weaker or reduced in the GMMF when using more CRM grid points and higher CRM resolution. In addition, the results indicate that large-scale surface evaporation and wind feed back are key processes for determining the surface rainfall amount in the GMMF. A sensitivity test with reduced sea surface temperatures shows both reduced surface rainfall and evaporation.

The impact of simulated mesoscale convective systems on global precipitation: A multiscale modeling study

NASA Astrophysics Data System (ADS)

Tao, Wei-Kuo; Chern, Jiun-Dar

2017-06-01

The importance of precipitating mesoscale convective systems (MCSs) has been quantified from TRMM precipitation radar and microwave imager retrievals. MCSs generate more than 50% of the rainfall in most tropical regions. MCSs usually have horizontal scales of a few hundred kilometers (km); therefore, a large domain with several hundred km is required for realistic simulations of MCSs in cloud-resolving models (CRMs). Almost all traditional global and climate models do not have adequate parameterizations to represent MCSs. Typical multiscale modeling frameworks (MMFs) may also lack the resolution (4 km grid spacing) and domain size (128 km) to realistically simulate MCSs. The impact of MCSs on precipitation is examined by conducting model simulations using the Goddard Cumulus Ensemble (GCE, a CRM) model and Goddard MMF that uses the GCEs as its embedded CRMs. Both models can realistically simulate MCSs with more grid points (i.e., 128 and 256) and higher resolutions (1 or 2 km) compared to those simulations with fewer grid points (i.e., 32 and 64) and low resolution (4 km). The modeling results also show the strengths of the Hadley circulations, mean zonal and regional vertical velocities, surface evaporation, and amount of surface rainfall are weaker or reduced in the Goddard MMF when using more CRM grid points and higher CRM resolution. In addition, the results indicate that large-scale surface evaporation and wind feedback are key processes for determining the surface rainfall amount in the GMMF. A sensitivity test with reduced sea surface temperatures shows both reduced surface rainfall and evaporation.

Comparison of Ground- and Space-based Radar Observations with Disdrometer Measurements During the PECAN Field Campaign

NASA Astrophysics Data System (ADS)

Torres, A. D.; Rasmussen, K. L.; Bodine, D. J.; Dougherty, E.

2015-12-01

Plains Elevated Convection At Night (PECAN) was a large field campaign that studied nocturnal mesoscale convective systems (MCSs), convective initiation, bores, and low-level jets across the central plains in the United States. MCSs are responsible for over half of the warm-season precipitation across the central U.S. plains. The rainfall from deep convection of these systems over land have been observed to be underestimated by satellite radar rainfall-retrieval algorithms by as much as 40 percent. These algorithms have a strong dependence on the generally unmeasured rain drop-size distribution (DSD). During the campaign, our group measured rainfall DSDs, precipitation fall velocities, and total precipitation in the convective and stratiform regions of MCSs using Ott Parsivel optical laser disdrometers. The disdrometers were co-located with mobile pod units that measured temperature, wind, and relative humidity for quality control purposes. Data from the operational NEXRAD radar in LaCrosse, Wisconsin and space-based radar measurements from a Global Precipitation Measurement satellite overpass on July 13, 2015 were used for the analysis. The focus of this study is to compare DSD measurements from the disdrometers to radars in an effort to reduce errors in existing rainfall-retrieval algorithms. The error analysis consists of substituting measured DSDs into existing quantitative precipitation estimation techniques (e.g. Z-R relationships and dual-polarization rain estimates) and comparing these estimates to ground measurements of total precipitation. The results from this study will improve climatological estimates of total precipitation in continental convection that are used in hydrological studies, climate models, and other applications.

Simulation of climate characteristics and extremes of the Volta Basin using CCLM and RCA regional climate models

NASA Astrophysics Data System (ADS)

Darko, Deborah; Adjei, Kwaku A.; Appiah-Adjei, Emmanuel K.; Odai, Samuel N.; Obuobie, Emmanuel; Asmah, Ruby

2018-06-01

The extent to which statistical bias-adjusted outputs of two regional climate models alter the projected change signals for the mean (and extreme) rainfall and temperature over the Volta Basin is evaluated. The outputs from two regional climate models in the Coordinated Regional Climate Downscaling Experiment for Africa (CORDEX-Africa) are bias adjusted using the quantile mapping technique. Annual maxima rainfall and temperature with their 10- and 20-year return values for the present (1981-2010) and future (2051-2080) climates are estimated using extreme value analyses. Moderate extremes are evaluated using extreme indices (viz. percentile-based, duration-based, and intensity-based). Bias adjustment of the original (bias-unadjusted) models improves the reproduction of mean rainfall and temperature for the present climate. However, the bias-adjusted models poorly reproduce the 10- and 20-year return values for rainfall and maximum temperature whereas the extreme indices are reproduced satisfactorily for the present climate. Consequently, projected changes in rainfall and temperature extremes were weak. The bias adjustment results in the reduction of the change signals for the mean rainfall while the mean temperature signals are rather magnified. The projected changes for the original mean climate and extremes are not conserved after bias adjustment with the exception of duration-based extreme indices.

Assessing operative natural and anthropogenic forcing factors from long-term climate time series of Uttarakhand (India) in the backdrop of recurring extreme rainfall events over northwest Himalaya

NASA Astrophysics Data System (ADS)

Agnihotri, Rajesh; Dimri, A. P.; Joshi, H. M.; Verma, N. K.; Sharma, C.; Singh, J.; Sundriyal, Y. P.

2017-05-01

The entire Indo-Himalayan region from northwest (Kashmir) to northeast (Assam) is facing prevalence of floods and landslides in recent years causing massive loss of property, human and animal lives, infrastructure, and eventually threatening tourist activities substantially. Extremely intense rainfall event of 2013 C.E. (between 15 and 17 June) kicked off mammoth flash floods in the Kedarnath area of Uttarakhand state, resulting in huge socioeconomic losses to the state and country. Uttarakhand is an important hilly region attracting thousands of tourists every year owing to numerous shrines and forested mountainous tourist spots. Though recent studies indicate a plausible weakening of Indian summer monsoon rainfall overall, recurrent anomalous high rainfall events over northwest Himalaya (e.g. -2010, 2013, and 2016) point out the need for a thorough reassessment of long-term time series data of regional rainfall and ambient temperatures in order to trace signatures of a shifting pattern in regional meteorology, if any. Accordingly, here we investigate 100-year-long monthly rainfall and air temperature time series data for a selected grid (28.5°N, 31.25°N; 78.75°E, 81.25°E) covering most parts of Uttarakhand state. We also examined temporal variance in interrelationships among regional meteorological data (temperature and precipitation) and key global climate variability indices using advance statistical methods. Major findings are (i) significant increase in pre-monsoon air temperature over Uttarakhand after 1997, (ii) increasing upward trend in June-July rainfall and its relationship with regional May temperatures (iii) monsoonal rainfall (June, July, August, and September; JJAS) showing covariance with interannual variability in Eurasian snow cover (ESC) extent during the month of March, and (iv) enhancing tendency of anomalous high rainfall events during negative phases of Arctic Oscillation. Obtained results indicate that under warming scenario, JJ rainfall (over AS) may further increase with occasional extreme rainfall spells when AO index (March) is negative.

Precipitation Discrimination from Satellite Infrared Temperatures over the CCOPE Mesonet Region.

NASA Astrophysics Data System (ADS)

Weiss, Mitchell; Smith, Eric A.

1987-06-01

A quantitative investigation of the relationship between satellite-derived cloud-top temperature parameters and the detection of intense convective rainfall is described. The area of study is that of the Cooperative Convective Precipitation Experiment (CCOPE), which was held near Miles City, Montana during the summer of 1981. Cloud-top temperatures, derived from the GOES-West operational satellite, were used to calculate a variety of parameters for objectively quantifying the convective intensity of a storm. A dense network of rainfall provided verification of surface rainfall. The cloud-top temperature field and surface rainfall data were processed into equally sized grid domains in order to best depict the individual samples of instantaneous precipitation.The technique of statistical discriminant analysis was used to determine which combinations of cloud-top temperature parameters best classify rain versus no-rain occurrence using three different rain-rate cutoffs: 1, 4, and 10 mm h1. Time lags within the 30 min rainfall verification were tested to determine the optimum time delay associated with rainfall reaching the ground.A total of six storm cases were used to develop and test the statistical models. Discrimination of rain events was found to be most accurate when using a 10 mm h1 rain-rate cutoff. Use parameters designated as coldest cloud-top temperature, the spatial mean of coldest cloud-top temperature, and change over time of mean coldest cloud-top temperature were found to be the best classifiers of rainfall in this study. Combining both a 10-min time lag (in terms of surface verification) with a 10 mm h1 rain-rate threshold resulted in classifying over 60% of all rain and no-rain cases correctly.

Detection of the spectroscopic signatures of explosives and their degradation products

NASA Astrophysics Data System (ADS)

Florian, Vivian; Cabanzo, Andrea; Baez, Bibiana; Correa, Sandra; Irrazabal, Maik; Briano, Julio G.; Castro, Miguel E.; Hernandez-Rivera, Samuel P.

2005-06-01

Detection and removal of antipersonnel and antitank landmines is a great challenge and a worldwide enviromental and humanitarian problem. Sensors tuned on the spectroscopic signature of the chemicals released from mines are a potential solution. Enviromental factors (temperature, relative humidity, rainfall precipitation, wind, sun irradiation, pressure, etc.) as well as soil characteristics (water content, compaction, porosity, chemical composition, particle size distribution, topography, vegetation, etc), have a direct impact on the fate and transport of the chemicals released from landmines. Chemicals such as TNT, DNT and their degradation products, are semi-volatile, and somewhat soluble in water. Also, they may adsorb strongly to soil particles, and are susceptible to degradation by microorganisms, light, or chemical agents. Here we show an experimental procedure to quantify the effect of the above variables on the spectroscopic signature. A number of soil tanks under controlled conditions are used to study the effect of temperature, water content, relative humidity and light radiation.

Dynamical and Thermodynamic Elements of Modeled Climate Change at the East African Margin of Convection

NASA Astrophysics Data System (ADS)

Giannini, Alessandra; Lyon, Bradfield; Seager, Richard; Vigaud, Nicolas

2018-01-01

We propose a dynamical interpretation of model projections for an end-of-century wetting in equatorial East Africa. In the current generation of global climate models, increased atmospheric moisture content associated with warming is not the dominant process explaining the increase in rainfall, as the regional circulation is only weakly convergent even during the rainy seasons. Instead, projected wetter future conditions are generally consistent with the El Niño-like trend in tropical Pacific sea surface temperatures in climate models. In addition, a weakening in moisture convergence over the adjacent Congo Basin and Maritime Continent cores of convection results in the weakening of near-surface winds, which increases moisture advection from the Congo Basin core toward the East African margin. Overall confidence in the projections is limited by the significant biases in simulation of the regional climatology and disagreement between observed and modeled tropical Pacific sea surface temperature trends to date.

Low elevation angle KU-band satellite measurements at Austin, Texas

NASA Technical Reports Server (NTRS)

Vogel, Wolfhard J.; Torrence, Geoffrey W.; Ranganathan, Murali

1989-01-01

At low elevation angles, the propagation of satellite signals is affected by precipitation as well as by inhomogeneties of the refractive index. Whereas precipitation causes fades for relatively small percentages of time, the refractive index variability causes scintillations which can be observed for most of the time. An experiment is now under way in Austin, Texas, in which the right hand circularly polarized 12 GHz beacon of INTELSAT-V/F10 is observed at a 5.8 deg elevation angle, along with the radiometric sky temperature, rainfall rate, humidity, pressure, temperature, and wind speed and direction. The objective of these measurements is to accumulate a database over a period of 2 years and to analyze the probabilities and dynamical behavior of the signal variations in relation to the meteorological parameters. The hardware and software used for the data acquisition and analysis is described and the results from the first year of measurements are presented.

Coral mass spawning predicted by rapid seasonal rise in ocean temperature

PubMed Central

Maynard, Jeffrey A.; Edwards, Alasdair J.; Guest, James R.; Rahbek, Carsten

2016-01-01

Coral spawning times have been linked to multiple environmental factors; however, to what extent these factors act as generalized cues across multiple species and large spatial scales is unknown. We used a unique dataset of coral spawning from 34 reefs in the Indian and Pacific Oceans to test if month of spawning and peak spawning month in assemblages of Acropora spp. can be predicted by sea surface temperature (SST), photosynthetically available radiation, wind speed, current speed, rainfall or sunset time. Contrary to the classic view that high mean SST initiates coral spawning, we found rapid increases in SST to be the best predictor in both cases (month of spawning: R2 = 0.73, peak: R2 = 0.62). Our findings suggest that a rapid increase in SST provides the dominant proximate cue for coral mass spawning over large geographical scales. We hypothesize that coral spawning is ultimately timed to ensure optimal fertilization success. PMID:27170709

Measuring precipitation with a geolysimeter

NASA Astrophysics Data System (ADS)

Smith, Craig D.; van der Kamp, Garth; Arnold, Lauren; Schmidt, Randy

2017-10-01

Using the relationship between measured groundwater pressures in deep observation wells and total surface loading, a geological weighing lysimeter (geolysimeter) has the capability of measuring precipitation event totals independently of conventional precipitation gauge observations. Correlations between groundwater pressure change and event precipitation were observed at a co-located site near Duck Lake, SK, over a multi-year and multi-season period. Correlation coefficients (r2) varied from 0.99 for rainfall to 0.94 for snowfall. The geolysimeter was shown to underestimate rainfall by 7 % while overestimating snowfall by 9 % as compared to the unadjusted gauge precipitation. It is speculated that the underestimation of rainfall is due to unmeasured run-off and evapotranspiration within the response area of the geolysimeter during larger rainfall events, while the overestimation of snow is at least partially due to the systematic undercatch common to most precipitation gauges due to wind. Using recently developed transfer functions from the World Meteorological Organization's (WMO) Solid Precipitation Intercomparison Experiment (SPICE), bias adjustments were applied to the Alter-shielded, Geonor T-200B precipitation gauge measurements of snowfall to mitigate wind-induced errors. The bias between the gauge and geolysimeter measurements was reduced to 3 %. This suggests that the geolysimeter is capable of accurately measuring solid precipitation and can be used as an independent and representative reference of true precipitation.

Rainfall extremes, weather and climatic characterization over complex terrain: A data-driven approach based on signal enhancement methods and extreme value modeling

NASA Astrophysics Data System (ADS)

Pineda, Luis E.; Willems, Patrick

2017-04-01

Weather and climatic characterization of rainfall extremes is both of scientific and societal value for hydrometeorogical risk management, yet discrimination of local and large-scale forcing remains challenging in data-scarce and complex terrain environments. Here, we present an analysis framework that separate weather (seasonal) regimes and climate (inter-annual) influences using data-driven process identification. The approach is based on signal-to-noise separation methods and extreme value (EV) modeling of multisite rainfall extremes. The EV models use a semi-automatic parameter learning [1] for model identification across temporal scales. At weather scale, the EV models are combined with a state-based hidden Markov model [2] to represent the spatio-temporal structure of rainfall as persistent weather states. At climatic scale, the EV models are used to decode the drivers leading to the shift of weather patterns. The decoding is performed into a climate-to-weather signal subspace, built via dimension reduction of climate model proxies (e.g. sea surface temperature and atmospheric circulation) We apply the framework to the Western Andean Ridge (WAR) in Ecuador and Peru (0-6°S) using ground data from the second half of the 20th century. We find that the meridional component of winds is what matters for the in-year and inter-annual variability of high rainfall intensities alongside the northern WAR (0-2.5°S). There, low-level southerly winds are found as advection drivers for oceanic moist of the normal-rainy season and weak/moderate the El Niño (EN) type; but, the strong EN type and its unique moisture surplus is locally advected at lowlands in the central WAR. Moreover, the coastal ridges, south of 3°S dampen meridional airflows, leaving local hygrothermal gradients to control the in-year distribution of rainfall extremes and their anomalies. Overall, we show that the framework, which does not make any prior assumption on the explanatory power of the weather and climate drivers, allows identification of well-known features of the regional climate in a purely data-driven fashion. Thus, this approach shows potential for characterization of precipitation extremes in data-scarce and orographically complex regions in which model reconstructions are the only climate proxies References [1] Mínguez, R., F.J. Méndez, C. Izaguirre, M. Menéndez, and I.J. Losada (2010), Pseudooptimal parameter selection of non-stationary generalized extreme value models for environmental variables, Environ. Modell. Softw. 25, 1592-1607. [2] Pineda, L., P. Willems (2016), Multisite Downscaling of Seasonal Predictions to Daily Rainfall Characteristics over Pacific-Andean River Basins in Ecuador and Peru using a non-homogenous hidden Markov model, J. Hydrometeor, 17(2), 481-498, doi:10.1175/JHM-D-15-0040.1, http://journals.ametsoc.org/doi/full/10.1175/JHM-D-15-0040.1

Climate Change In Indonesia (Case Study : Medan, Palembang, Semarang)

NASA Astrophysics Data System (ADS)

Suryadi, Yadi; Sugianto, Denny Nugroho; Hadiyanto

2018-02-01

Indonesia's maritime continent is one of the most vulnerable regions regarding to climate change impacts. One of the vulnerable areas affected are the urban areas, because they are home to almost half of Indonesia's population where they live and earn a living, so that environmental management efforts need to be done. To support such efforts, climate change analysis is required. The analysis was carried out in several big cities in Indonesia. The method used in the research was trend analysis of temperature, rainfall, shifts in rainfall patterns, and extreme climatic trend. The data of rainfall and temperature were obtained from Meteorology and Geophysics Agency (BMKG). The result shows that the air temperature and rainfall have a positive trend, except in Semarang City which having a negative rainfall trend. The result also shows heavy rainfall trends. These indicate that climate is changing in these three cities.

A wood-strand material for wind erosion control: effects on total sediment loss, PM10 vertical flux, and PM10 loss.

PubMed

Copeland, N S; Sharratt, B S; Wu, J Q; Foltz, R B; Dooley, J H

2009-01-01

Fugitive dust from eroding land poses risks to environmental quality and human health, and thus, is regulated nationally based on ambient air quality standards for particulate matter with mean aerodynamic diameter < or = 10 microm (PM10) established in the Clean Air Act. Agricultural straw has been widely used for rainfall-induced erosion control; however, its performance for wind erosion mitigation has been less studied, in part because straw is mobile at moderate wind velocities. A wood-based long-strand material has been developed for rainfall-induced erosion control and has shown operational promise for control of wind-induced erosion and dust emissions from disturbed sites. The purpose of this study was to evaluate the efficacy of both agricultural straw and wood-strand materials in controlling wind erosion and fugitive dust emissions under laboratory conditions. Wind tunnel tests were conducted to compare wood strands of several geometries to agricultural wheat straw and bare soil in terms of total sediment loss, PM10 vertical flux, and PM10 loss. Results indicate that the types of wood strands tested are stable at wind speeds of up to 18 m s(-1), while wheat straw is only stable at speeds of up to 6.5 m s(-1). Wood strands reduced total sediment loss and PM10 emissions by 90% as compared to bare soil across the range of wind speeds tested. Wheat straw did not reduce total sediment loss for the range of speeds tested, but did reduce PM10 emissions by 75% compared to a bare soil at wind speeds of up to 11 m s(-1).

Hydrodynamic modelling of recreational water quality using Escherichia coli as an indicator of microbial contamination

NASA Astrophysics Data System (ADS)

Eregno, Fasil Ejigu; Tryland, Ingun; Tjomsland, Torulv; Kempa, Magdalena; Heistad, Arve

2018-06-01

Microbial contamination of recreational beaches is often at its worst after heavy rainfall events due to storm floods that carry fecal matter and other pollutants from the watershed. Similarly, overflows of untreated sewage from combined sewerage systems may discharge directly into coastal water or via rivers and streams. In order to understand the effect of rainfall events, wind-directions and tides on the recreational water quality, GEMSS, an integrated 3D hydrodynamic model was applied to assess the spreading of Escherichia coli (E. coli) at the Sandvika beaches, located in the Oslo fjord. The model was also used to theoretically investigate the effect of discharges from septic tanks from boats on the water quality at local beaches. The model make use of microbial decay rate as the main input representing the survival of microbial pathogens in the ocean, which vary widely depending on the type of pathogen and environmental stress. The predicted beach water quality was validated against observed data after a heavy rainfall event using Nash-Sutcliffe coefficient (E) and the overall result indicated that the model performed quite well and the simulation was in - good agreement with the observed E. coli concentrations for all beaches. The result of this study indicated that: 1) the bathing water quality was poor according to the EU bathing water directive up to two days after the heavy rainfall event depending on the location of the beach site. 2) The discharge from a boat at 300-meter distance to the beaches slightly increased the E. coli levels at the beaches. 3) The spreading of microbial pathogens from its source to the different beaches depended on the wind speed and the wind direction.

A comparison between the effects of artificial land cover and anthropogenic heat on a localized heavy rain event in 2008 in Zoshigaya, Tokyo, Japan

NASA Astrophysics Data System (ADS)

Souma, Kazuyoshi; Tanaka, Kenji; Suetsugi, Tadashi; Sunada, Kengo; Tsuboki, Kazuhisa; Shinoda, Taro; Wang, Yuqing; Sakakibara, Atsushi; Hasegawa, Koichi; Moteki, Qoosaku; Nakakita, Eiichi

2013-10-01

5 August 2008, a localized heavy rainfall event caused a rapid increase in drainpipe discharge, which killed five people working in a drainpipe near Zoshigaya, Tokyo. This study compared the effects of artificial land cover and anthropogenic heat on this localized heavy rainfall event based on three ensemble experiments using a cloud-resolving model that includes realistic urban features. The first experiment CTRL (control) considered realistic land cover and urban features, including artificial land cover, anthropogenic heat, and urban geometry. In the second experiment NOAH (no anthropogenic heat), anthropogenic heat was ignored. In the third experiment NOLC (no land cover), urban heating from artificial land cover was reduced by keeping the urban geometry but with roofs, walls, and roads of artificial land cover replaced by shallow water. The results indicated that both anthropogenic heat and artificial land cover increased the amount of precipitation and that the effect of artificial land cover was larger than that of anthropogenic heat. However, in the middle stage of the precipitation event, the difference between the two effects became small. Weak surface heating in NOAH and NOLC reduced the near-surface air temperature and weakened the convergence of horizontal wind and updraft over the urban areas, resulting in a reduced rainfall amount compared with that in CTRL.

Mechanism of ENSO influence on the South Asian monsoon rainfall in global model simulations

NASA Astrophysics Data System (ADS)

Joshi, Sneh; Kar, Sarat C.

2018-02-01

Coupled ocean atmosphere global climate models are increasingly being used for seasonal scale simulation of the South Asian monsoon. In these models, sea surface temperatures (SSTs) evolve as coupled air-sea interaction process. However, sensitivity experiments with various SST forcing can only be done in an atmosphere-only model. In this study, the Global Forecast System (GFS) model at T126 horizontal resolution has been used to examine the mechanism of El Niño-Southern Oscillation (ENSO) forcing on the monsoon circulation and rainfall. The model has been integrated (ensemble) with observed, climatological and ENSO SST forcing to document the mechanism on how the South Asian monsoon responds to basin-wide SST variations in the Indian and Pacific Oceans. The model simulations indicate that the internal variability gets modulated by the SSTs with warming in the Pacific enhancing the ensemble spread over the monsoon region as compared to cooling conditions. Anomalous easterly wind anomalies cover the Indian region both at 850 and 200 hPa levels during El Niño years. The locations and intensity of Walker and Hadley circulations are altered due to ENSO SST forcing. These lead to reduction of monsoon rainfall over most parts of India during El Niño events compared to La Niña conditions. However, internally generated variability is a major source of uncertainty in the model-simulated climate.

Proxy system modeling of tree-ring isotope chronologies over the Common Era

NASA Astrophysics Data System (ADS)

Anchukaitis, K. J.; LeGrande, A. N.

2017-12-01

The Asian monsoon can be characterized in terms of both precipitation variability and atmospheric circulation across a range of spatial and temporal scales. While multicentury time series of tree-ring widths at hundreds of sites across Asia provide estimates of past rainfall, the oxygen isotope ratios of annual rings may reveal broader regional hydroclimate and atmosphere-ocean dynamics. Tree-ring oxygen isotope chronologies from Monsoon Asia have been interpreted to reflect a local 'amount effect', relative humidity, source water and seasonality, and winter snowfall. Here, we use an isotope-enabled general circulation model simulation from the NASA Goddard Institute for Space Science (GISS) Model E and a proxy system model of the oxygen isotope composition of tree-ring cellulose to interpret the large-scale and local climate controls on δ 18O chronologies. Broad-scale dominant signals are associated with a suite of covarying hydroclimate variables including growing season rainfall amounts, relative humidity, and vapor pressure deficit. Temperature and source water influences are region-dependent, as are the simulated tree-ring isotope signals associated with the El Nino Southern Oscillation (ENSO) and large-scale indices of the Asian monsoon circulation. At some locations, including southern coastal Viet Nam, local precipitation isotope ratios and the resulting simulated δ 18O tree-ring chronologies reflect upstream rainfall amounts and atmospheric circulation associated with monsoon strength and wind anomalies.

Climate Assessment for 2000.

NASA Astrophysics Data System (ADS)

Lawrimore, Jay H.; Halpert, Michael S.; Bell, Gerald D.; Menne, Matthew J.; Lyon, Bradfield; Schnell, Russell C.; Gleason, Karin L.; Easterling, David R.; Thiaw, Wasila; Wright, William J.; Heim, Richard R., Jr.; Robinson, David A.; Alexander, Lisa

2001-06-01

The global climate in 2000 was again influenced by the long-running Pacific cold episode (La Niña) that began in mid-1998. Consistent with past cold episodes, enhanced convection occurred across the climatologically convective regions of Indonesia and the western equatorial Pacific, while convection was suppressed in the central Pacific. The La Niña was also associated with a well-defined African easterly jet located north of its climatological mean position and low vertical wind shear in the tropical Atlantic and Caribbean, both of which contributed to an active North Atlantic hurricane season. Precipitation patterns influenced by typical La Niña conditions included 1) above-average rainfall in southeastern Africa, 2) unusually heavy rainfall in northern and central regions of Australia, 3) enhanced precipitation in the tropical Indian Ocean and western tropical Pacific, 4) little rainfall in the central tropical Pacific, 5) below-normal precipitation over equatorial east Africa, and 6) drier-than-normal conditions along the Gulf coast of the United States.Although no hurricanes made landfall in the United States in 2000, another active North Atlantic hurricane season featured 14 named storms, 8 of which became hurricanes, with 3 growing to major hurricane strength. All of the named storms over the North Atlantic formed during the August-October period with the first hurricane of the season, Hurricane Alberto, notable as the third-longest-lived tropical system since reliable records began in 1945. The primary human loss during the 2000 season occurred in Central America, where Hurricane Gordon killed 19 in Guatemala, and Hurricane Keith killed 19 in Belize and caused $200 million dollars of damage.Other regional events included 1) record warm January-October temperatures followed by record cold November-December temperatures in the United States, 2) extreme drought and widespread wildfires in the southern and western Unites States, 3) continued long-term drought in the Hawaiian Islands throughout the year with record 24-h rainfall totals in November, 4) deadly storms and flooding in western Europe in October, 5) a summer heat wave and drought in southern Europe, 6) monsoon flooding in parts of Southeast Asia and India, 7) extreme winter conditions in Mongolia, 8) extreme long-term drought in the Middle East and Southwest Asia, and 9) severe flooding in southern Africa.Global mean temperatures remained much above average in 2000. The average land and ocean temperature was 0.39°C above the 1880-1999 long-term mean, continuing a trend to warmer-than-average temperatures that made the 1990s the warmest decade on record. While the persistence of La Niña conditions in 2000 was associated with somewhat cooler temperatures in the Tropics, temperatures in the extratropics remained near record levels. Land surface temperatures in the high latitudes of the Northern Hemisphere were notably warmer than normal, with annually averaged anomalies greater than 2°C in parts of Alaska, Canada, Asia, and northern Europe.

Satellite observations of rainfall effect on sea surface salinity in the waters adjacent to Taiwan

NASA Astrophysics Data System (ADS)

Ho, Chung-Ru; Hsu, Po-Chun; Lin, Chen-Chih; Huang, Shih-Jen

2017-10-01

Changes of oceanic salinity are highly related to the variations of evaporation and precipitation. To understand the influence of rainfall on the sea surface salinity (SSS) in the waters adjacent to Taiwan, satellite remote sensing data from the year of 2012 to 2014 are employed in this study. The daily rain rate data obtained from Special Sensor Microwave Imager (SSM/I), Tropical Rainfall Measuring Mission's Microwave Imager (TRMM/TMI), Advanced Microwave Scanning Radiometer (AMSR), and WindSat Polarimetric Radiometer. The SSS data was derived from the measurements of radiometer instruments onboard the Aquarius satellite. The results show the average values of SSS in east of Taiwan, east of Luzon and South China Sea are 33.83 psu, 34.05 psu, and 32.84 psu, respectively, in the condition of daily rain rate higher than 1 mm/hr. In contrast to the rainfall condition, the average values of SSS are 34.07 psu, 34.26 psu, and 33.09 psu in the three areas, respectively at no rain condition (rain rate less than 1 mm/hr). During the cases of heavy rainfall caused by spiral rain bands of typhoon, the SSS is diluted with an average value of -0.78 psu when the average rain rate is higher than 4 mm/hr. However, the SSS was increased after temporarily decreased during the typhoon cases. A possible reason to explain this phenomenon is that the heavy rainfall caused by the spiral rain bands of typhoon may dilute the sea surface water, but the strong winds can uplift the higher salinity of subsurface water to the sea surface.

Mesoscale observational analysis of lifting mechanism of a warm-sector convective system producing the maximal daily precipitation in China mainland during pre-summer rainy season of 2015

NASA Astrophysics Data System (ADS)

Wu, Mengwen; Luo, Yali

2016-08-01

A long-lived, quasi-stationary mesoscale convective system (MCS) producing extreme rainfall (maximum of 542 mm) over the eastern coastal area of Guangdong Province on 20 May 2015 is analyzed by using high-resolution surface observations, sounding data, and radar measurements. New convective cells are continuously initiated along a mesoscale boundary at the surface, leading to formation and maintenance of the quasi-linear-shaped MCS from about 2000 BT 19 to 1200 BT 20 May. The boundary is originally formed between a cold dome generated by previous convection and southwesterly flow from the ocean carrying higher equivalent potential temperature ( θ e) air. The boundary is subsequently maintained and reinforced by the contrast between the MCS-generated cold outflow and the oceanic higher- θ e air. The cold outflow is weak (wind speed ≤ 5 m s -1), which is attributable to the characteristic environmental conditions, i.e., high humidity in the lower troposphere and weak horizontal winds in the middle and lower troposphere. The low speed of the cold outflow is comparable to that of the near surface southerly flow from the ocean, resulting in very slow southward movement of the boundary. The boundary features temperature contrasts of 2-3°C and is roughly 500-m deep. Despite its shallowness, the boundary appears to exert a profound influence on continuous convection initiation because of the very low level of free convection and small convection inhibition of the near surface oceanic air, building several parallel rainbands (of about 50-km length) that move slowly eastward along the MCS and produce about 80% of the total rainfall. Another MCS moves into the area from the northwest and merges with the local MCS at about 1200 BT. The cold outflow subsequently strengthens and the boundary moves more rapidly toward the southeast, leading to end of the event in 3 h.

The impact of a prominent rain shadow on flooding in California's Santa Cruz Mountains: A CALJET case study and sensitivity to the ENSO cycle

USGS Publications Warehouse

Ralph, F.M.; Neiman, P.J.; Kingsmill, D.E.; Persson, P.O.G.; White, A.B.; Strem, E.T.; Andrews, E.D.; Antweiler, Ronald C.

2003-01-01

Data from the California Land-Falling Jets Experiment (CALJET) are used to explore the causes of variations in flood severity in adjacent coastal watersheds within the Santa Cruz Mountains on 2-3 February 1998. While Pescadero Creek (rural) experienced its flood of record, the adjacent San Lorenzo Creek (heavily populated), attained only its fourth-highest flow. This difference resulted from conditions present while the warm sector of the storm, with its associated low-level jet, high moisture content, and weak static stability, was overhead. Rainfall in the warm sector was dominated by orographic forcing. While the wind speed strongly modulated rain rates on windward slopes, the wind direction positioned the edge of a rain shadow cast by the Santa Lucia Mountains partially over the San Lorenzo basin, thus protecting the city of Santa Cruz from a more severe flood. Roughly 26% ?? 9% of the streamflow at flood peak on Pescadero Creek resulted from the warm-sector rainfall. Without this rainfall, the peak flow on Pescadero Creek would likely not have attained record status. These results are complemented by a climatological analysis based on ???50-yr-duration streamflow records for these and two other nearby windward watersheds situated ???20 to 40 km farther to the east, and a comparison of this climatological analysis with composites of NCEP-NCAR reanalysis fields. The westernmost watersheds were found to have their greatest floods during El Nin??o winters, while the easternmost watersheds peaked during non-El Nin??o episodes. These results are consistent with the case study, that showed that the composite 925-mb, meridionally oriented wind direction during El Nin??os favors a rain shadow over the eastern watersheds. During non-El Nin??o periods, the composite, zonally oriented wind direction indicates that the sheltering effect of the rain shadow on the eastern watersheds is reduced, while weaker winds, less water vapor, and stronger stratification reduce the peak runoff in the western watersheds relative to El Nin??o periods. These case study and climatological results illustrate the importance of conditions in the moisture-rich warm sector of landfalling Pacific winter storms. Although many other variables can influence flooding, this study shows that variations of ??10?? in wind direction can modulate the location of orographically enhanced floods. While terrain can increase predictability (e.g., rainfall typically increases with altitude), the predictability is reduced when conditions are near a threshold separating different regimes (e.g., in or out of a rain shadow ).

Spatial Dependence of the Relationship between Rainfall and Outgoing Longwave Radiation in the Tropical Atlantic.

NASA Astrophysics Data System (ADS)

Yoo, Jung-Moon; Carton, James A.

1988-10-01

We develop a Spatially dependent formula to estimate rainfall from satellite-derived outgoing longwave radiation (OLR) data and the height of the base of the trade-wind inversion. This formula has been constructed by comparing rainfall records from twelve islands in the tropical Atlantic with 11 years of OLR data. Zonal asymmetries due to the differing cloud types in the eastern and western Atlantic and the presence of Saharan sand in the cast are included.The climatological winter and summer rainfall derived from the above formula concurs with ship observations described by Dorman and Bourke. However, during the spring and fall, OLR-derived rainfall is higher than observations by 2-4 mm day1 in the intertropical convergence zone. The largest discrepancy occurs during the fall in the region west of 28°W. Interannual anomalies of rainfall computed using this technique are large enough to cause potentially important changes in ocean surface salinity.

Description and preliminary results of a 100 square meter rain gauge

NASA Astrophysics Data System (ADS)

Grimaldi, Salvatore; Petroselli, Andrea; Baldini, Luca; Gorgucci, Eugenio

2018-01-01

Rainfall is one of the most crucial processes in hydrology, and the direct and indirect rainfall measurement methods are constantly being updated and improved. The standard instrument used to measure rainfall rate and accumulation is the rain gauge, which provides direct observations. Though the small dimension of the orifice allows rain gauges to be installed anywhere, it also causes errors due to the splash and wind effects. To investigate the role of the orifice dimension, this study, for the first time, introduces and demonstrates an apparatus for observing rainfall called a giant-rain gauge that is characterised by a collecting surface of 100 m2. To discuss the new instrument and its technical details, a preliminary analysis of 26 rainfall events is provided. The results suggest that there are significant differences between the standard and proposed rain gauges. Specifically, major discrepancies are evident for low time aggregation scale (5, 10, and 15 min) and for high rainfall intensity values.

Spatial averaging of oceanic rainfall variability using underwater sound: Ionian Sea rainfall experiment 2004.

PubMed

Nystuen, Jeffrey A; Amitai, Eyal; Anagnostou, Emmanuel N; Anagnostou, Marios N

2008-04-01

An experiment to evaluate the inherent spatial averaging of the underwater acoustic signal from rainfall was conducted in the winter of 2004 in the Ionian Sea southwest of Greece. A mooring with four passive aquatic listeners (PALs) at 60, 200, 1000, and 2000 m was deployed at 36.85 degrees N, 21.52 degrees E, 17 km west of a dual-polarization X-band coastal radar at Methoni, Greece. The acoustic signal is classified into wind, rain, shipping, and whale categories. It is similar at all depths and rainfall is detected at all depths. A signal that is consistent with the clicking of deep-diving beaked whales is present 2% of the time, although there was no visual confirmation of whale presence. Co-detection of rainfall with the radar verifies that the acoustic detection of rainfall is excellent. Once detection is made, the correlation between acoustic and radar rainfall rates is high. Spatial averaging of the radar rainfall rates in concentric circles over the mooring verifies the larger inherent spatial averaging of the rainfall signal with recording depth. For the PAL at 2000 m, the maximum correlation was at 3-4 km, suggesting a listening area for the acoustic rainfall measurement of roughly 30-50 km(2).

Perceptible changes in Indian summer monsoon rainfall in relation to Indian Monsoon Index

NASA Astrophysics Data System (ADS)

Naidu, C. V.; Dharma Raju, A.; Vinay Kumar, P.; Satyanarayana, G. Ch.

2017-10-01

The changes in the summer monsoon rainfall over 30 meteorological subdivisions of India with respect to changes in circulation and the Indian Monsoon Index (IMI) have been studied for the period 1953-2012. The relationship between the IMIs in different months and whole season and the corresponding summer monsoon rainfall is studied and tested. The positive and negative extremes are evaluated basing on the normalized values of the deviations from the mean of the IMI. Composite rainfall distributions over India and the zonal wind distributions in the lower and upper troposphere of IMI's both positive and negative extremes are evaluated separately and discussed. In the recent three decades of global warming, the negative values of IMI in July and August lead to weakening of the monsoon system over India. It is observed that the rainfall variations in the Northeast India are different from the rest of India except Tamil Nadu in general.

[Influence of weather in the incidence of acute myocardial infarction in Galicia (Spain)].

PubMed

Fernández-García, José Manuel; Dosil Díaz, Olga; Taboada Hidalgo, Juan José; Fernández, José Ramón; Sánchez-Santos, Luis

2015-08-07

To assess the interactions between weather and the impact of each individual meteorological parameters in the incidence of acute myocardial infarctions (AMI) in Galicia. Retrospective study analyzing the number of AMI diagnosed and transferred to the hospital by the Emergencies Sanitary System of Galicia between 2002 and 2009. We included patients with clinical and ECG findings of AMI. The correlation between 10-minute meteorological variables (temperature, humidity, pressure, accumulated rainfall and wind speed) recorded by MeteoGalicia and the incidence of AMI was assessed. A total of 4,717 AMI were registered (72.8% men, 27.2% women). No seasonal variations were found. No significant correlations were detected with regard to average daily temperature (P=.683) or wind speed (P=.895). Correlation between atmospheric pressure and incidence of AMI was significant (P<.005), as well as with the daily relative humidity average (P=.005). Our study showed a statistical significant association with atmospheric pressure and with the daily relative humidity average. Since the local conditions of weather are widely variable, future studies should establish the relationship between weather patterns (including combinations of meteorological parameters), rather than seasonal variations, and the incidence of AMI. Copyright © 2013 Elsevier España, S.L.U. All rights reserved.

Changes to Sub-daily Rainfall Patterns in a Future Climate

NASA Astrophysics Data System (ADS)

Westra, S.; Evans, J. P.; Mehrotra, R.; Sharma, A.

2012-12-01

An algorithm is developed for disaggregating daily rainfall into sub-daily rainfall 'fragments' (continuous high temporal-resolution rainfall sequences whose total depth sums to the daily rainfall amount) under a future, warmer climate. The basis of the algorithm is to re-sample sub-daily fragments from the historical record conditional on the total daily rainfall amount and a range of temperature-based atmospheric predictors. The logic is that as the atmosphere warms, future rainfall patterns will be more reflective of historical rainfall patterns which occurred on warmer days at the same location, or at locations which have an atmospheric temperature profile more representative of expected future atmospheric conditions. It was found that the daily to sub-daily scaling relationship varied significantly by season and by location, with rainfall patterns on warmer seasons or at warmer locations typically exhibiting higher rainfall intensity occurring over shorter periods within a day, compared with cooler seasons and locations. Importantly, by regressing against temperature-based atmospheric covariates, this effect was substantially reduced, suggesting that the approach also may be valid when extrapolating to a future climate. An adjusted method of fragments algorithm was then applied to nine stations around Australia, with the results showing that when holding total daily rainfall constant, the maximum intensity of short duration rainfall increased by a median of about 5% per degree for the maximum 6 minute burst, and 3.5% for the maximum one hour burst, whereas the fraction of the day with no rainfall increased by a median of 1.5%. This highlights that a large proportion of the change to the distribution of rainfall is likely to occur at sub-daily timescales, with significant implications for many hydrological systems.

Empirical downscaling of atmospheric key variables above a tropical glacier surface (Cordillera Blanca, Peru)

NASA Astrophysics Data System (ADS)

Hofer, M.; Kaser, G.; Mölg, T.; Juen, I.; Wagnon, P.

2009-04-01

Glaciers in the outer tropical Cordillera Blanca (Peru, South America) are of major socio-economic importance, since glacier runoff represents the primary water source during the dry season, when little or no rainfall occurs. Due to their location at high elevations, the glaciers moreover provide important information about climate change in the tropical troposphere, where measurements are sparse. This study targets the local reconstruction of air temperature, specific humidity and wind speed above the surface of an outer tropical glacier from NCEP/NCAR reanalysis data as large scale predictors. Since a farther scope is to provide input data for process based glacier mass balance modelling, the reconstruction pursues a high temporal resolution. Hence an empirical downscaling scheme is developed, based on a few years' time series of hourly observations from automatic weather stations, located at the glacier Artesonraju and nearby moraines (Northern Cordillera Blanca). Principal component and multiple regression analyses are applied to define the appropriate spatial downscaling domain, suitable predictor variables, and the statistical transfer functions. The model performance is verified using an independent data set. The best predictors are lower tropospheric air temperature and specific humidity, at reanalysis model grid points that represent the Bolivian Altiplano, located in the South of the Cordillera Blanca. The developed downscaling model explaines a considerable portion (more than 60%) of the diurnal variance of air temperature and specific humidity at the moraine stations, and air temperature above the glacier surface. Specific humidity above the glacier surface, however, can be reconstructed well in the seasonal, but not in the required diurnal time resolution. Wind speed can only be poorly determined by the large scale predictors (r² lower than 0.3) at both sites. We assume a complex local interaction between valley and glacier wind system to be the main cause for the differences between model and observations.

Radiative forcing and climate response due to the presence of black carbon in cloud droplets

NASA Astrophysics Data System (ADS)

Wang, Zhili; Zhang, Hua; Li, Jiangnan; Jing, Xianwen; Lu, Peng

2013-05-01

Optical properties of clouds containing black carbon (BC) particles in their water droplets are calculated by using the Maxwell Garnett mixing rule and Mie theory. The obtained cloud optical properties were then applied to an interactive system by coupling an aerosol model with a General Circulation Model. This system is used to investigate the radiative forcing and the equilibrium climate response due to BC in cloud droplets. The simulated global annual mean radiative forcing at the top of the atmosphere due to the BC in cloud droplets is found to be 0.086 W m-2. Positive radiative forcing can be seen in Africa, South America, East and South Asia, and West Europe, with a maximum value of 1.5 W m-2 being observed in these regions. The enhanced cloud absorption is shown to increase the global annual mean values of solar heating rate, water vapor, and temperature, but to decrease the global annual mean cloud fraction. Finally, the global annual mean surface temperature is shown to increase by +0.08 K. The local maximum changes are found to be as low as -1.5 K and as high as +0.6 K. We show there has been a significant difference in surface temperature change in the Southern and Northern Hemisphere (+0.19 K and -0.04 K, respectively). Our results show that this interhemispheric asymmetry in surface temperature change could cause a corresponding change in atmospheric dynamics and precipitation. It is also found that the northern trade winds are enhanced in the Intertropical Convergence Zone (ITCZ). This results in northerly surface wind anomalies which cross the equator to converge with the enhanced southern trade winds in the tropics of Southern Hemisphere. This is shown to lead to an increase (a decrease) of vertical ascending motion and precipitation on the south (north) side of the equator, which could induce a southward shift in the tropical rainfall maximum related to the ITCZ.

Radiative forcing and climate response due to the presence of black carbon in cloud droplets

NASA Astrophysics Data System (ADS)

Wang, Z.; Zhang, H.; Li, J.; Jing, X.; Lu, P.

2013-05-01

Optical properties of clouds containing black carbon (BC) particles in their water droplets are calculated by using the Maxwell Garnett mixing rule and Mie theory. The obtained cloud optical properties were then applied to an interactive system by coupling an aerosol model with a General Circulation Model. This system is used to investigate the radiative forcing and the equilibrium climate response due to BC in cloud droplets. The simulated global annual mean radiative forcing at the top of the atmosphere due to the BC in cloud droplets is found to be 0.086 W m-2. Positive radiative forcing can be seen in Africa, South America, East and South Asia and West Europe, with a maximum value of 1.5 W m-2 being observed in these regions. The enhanced cloud absorption is shown to increase the global annual mean values of solar heating rate, water vapor and temperature, but to decrease the global annual mean cloud fraction. Finally, the global annual mean surface temperature is shown to increase by +0.08 K. The local maximum changes are found to be as low as -1.5 K and as high as +0.6 K. We show there has been a significant difference in surface temperature change in the Southern and Northern Hemisphere (+0.19 K and -0.04 K, respectively). Our results show that this interhemispheric asymmetry in surface temperature change could cause a corresponding change in atmospheric dynamics and precipitation. It is also found that the northern trade winds are enhanced in the Intertropical Convergence Zone (ITCZ). This results in northerly surface wind anomalies which cross the equator to converge with the enhanced southern trade winds in the tropics of Southern Hemisphere. This is shown to lead to an increase (a decrease) of vertical ascending motion and precipitation on the south (north) side of the equator, which could induce a southward shift in the tropical rainfall maximum related to the ITCZ.

Synoptical situations and meteorological conditions associated to floods in the mouth of rivers in the European part of Russia

NASA Astrophysics Data System (ADS)

Matveeva, Tatiana; Gushchina, Daria

2013-04-01

The synoptical situations associated to the various type of floods in the mouth of rivers in European part of Russia are described. The storm surges, water flows and ice-jams are considered for Baltic, Barents sea, White sea, Azov sea, Black sea and Caspian sea regions. It is shown that the specific types of flood may be associated to various synoptical situations. Therefore it is unlikely to introduce the classification of synoptical regimes resulting in specific type of floods. However for each zone under consideration and for each specific flood type it is possible to determine the potential predictors of inundation: i.e. meteorological parameters which are characteristics of all cases of specific flood. There are: • for storm surges - long term wind forcing resulting in seiches in the sea, strong wind speed (the threshold varies in dependence on region), the wind direction orthogonal to the flow of river and strong baric gradient; • for water flows - the abundant precipitation, usually associate with the intensive frontal zone, the sudden change of air temperature resulting in snow melting in spring time; • for ice-jams - the strong temperature gradient extended in north-south direction resulting in negative temperature in the river mouth and positive temperature in the other basin. The probability of occurrence of predictors mentioned above was estimated for modern climate and global warming conditions using the outputs of ECHAM5/MPI-OM model. It is shown that the occurrence of intensive frontal zone and rainfall in the South of Russia will increase (decrease) in summer (winter) under warmer climate conditions which may contribute to the increase of water flows in this region. Maximum of floods occurs during the warm period, we can conclude that global warming increases the risk of floods in Black Sea coast.

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

Improving Global Analysis and Short-Range Forecast Using Rainfall and Moisture Observations Derived from TRMM and SSM/I Passive Microwave Instruments

NASA Technical Reports Server (NTRS)

Hou, Arthur Y.; Zhang, Sara Q.; daSilva, Arlindo M.; Olson, William S.; Kummerow, Christian D.; Simpson, Joanne

2000-01-01

The Global Precipitation Mission, a satellite project under consideration as a follow-on to the Tropical Rainfall Measuring Mission (TRMM) by the National Aeronautics and Space Agency (NASA) in the United States, the National Space Development Agency (NASDA) in Japan, and other international partners, comprises an improved TRMM-like satellite and a constellation of 8 satellites carrying passive microwave radiometers to provide global rainfall measurements at 3-hour intervals. The success of this concept relies on the merits of rainfall estimates derived from passive microwave radiometers. This article offers a proof-of-concept demonstration of the benefits of using, rainfall and total precipitable water (TPW) information derived from such instruments in global data assimilation with observations from the TRMM Microwave Imager (TMI) and 2 Special Sensor Microwave/Imager (SSM/I) instruments. Global analyses that optimally combine observations from diverse sources with physical models of atmospheric and land processes can provide a comprehensive description of the climate systems. Currently, such data analyses contain significant errors in primary hydrological fields such as precipitation and evaporation, especially in the tropics. We show that assimilating the 6-h averaged TMI and SSM/I surface rainrate and TPW retrievals improves not only the hydrological cycle but also key climate parameters such as clouds, radiation, and the upper tropospheric moisture in the analysis produced by the Goddard Earth Observing System (GEOS) Data Assimilation System, as verified against radiation measurements by the Clouds and the Earth's Radiant Energy System (CERES) instrument and brightness temperature observations by the TIROS Operational Vertical Sounder (TOVS) instruments. Typically, rainfall assimilation improves clouds and radiation in areas of active convection, as well as the latent heating and large-scale motions in the tropics, while TPW assimilation leads to reduced moisture biases and improved radiative fluxes in clear-sky regions. Ensemble forecasts initialized with analyses that incorporate TMI and SSM/I rainfall and TPW data also yield better short-range predictions of geopotential heights, winds, and precipitation in the tropics. This study offers a compelling illustration of the potential of using rainfall and TPW information derived from passive microwave instruments to significantly improve the quality of 4-dimensional global datasets for climate analysis and weather forecasting applications.

Observations of near-surface fresh layers during SPURS-2

NASA Astrophysics Data System (ADS)

Drushka, Kyla; E Asher, William; Thompson, Elizabeth; Jessup, Andrew T.; Clark, Dan

2017-04-01

One of the primary objectives of the ongoing SPURS-2 program is to understand the fate of rainfall deposited on the sea surface. Rain produces stable near-surface fresh layers that persist for O(1-10) hours. The depth, strength, and lifetime of surface fresh layers are known to be related to the local rain and wind conditions, but available observational data are too sparse to allow definitive quantification of cause-and-effect relationships. In this paper, the formation and evolution of rain-formed fresh layers are examined using observations of near-surface salinity made during the 2016 SPURS-2 field experiment, which took place in the Intertropical Convergence Zone of the eastern tropical Pacific Ocean in August-September 2016. During 2016 SPURS-2, over 30 rain events were captured with the Surface Salinity Profiler (SSP), a towed platform that measures salinity and temperature at five discrete depths in the upper meter of the ocean. Differences in salinity measured by the SSP at depths of 0.02 m and at 1 m are correlated with local meteorological conditions. The field results show that the salinity difference increases linearly with rain rate, a result that is consistent with calculations done with a one-dimensional ocean turbulence model. The field data also demonstrate that there is an inverse correlation between wind speed and the vertical salinity difference, which is also consistent with numerical models. The implications of these results are discussed in the context of satellite salinity observations and the representation of rainfall events in climate models.

Anopheles darlingi (Diptera: Culicidae) Dynamics in Relation to Meteorological Data in a Cattle Farm Located in the Coastal Region of French Guiana: Advantage of Mosquito Magnet Trap.

PubMed

Vezenegho, Samuel B; Carinci, Romuald; Gaborit, Pascal; Issaly, Jean; Dusfour, Isabelle; Briolant, Sebastien; Girod, Romain

2015-06-01

Information on dynamics of anopheline mosquitoes is limited in the coastal zone of French Guiana compared with inland endemic areas. Importantly, improvement of surveillance techniques for assessing malaria transmission indicators and comprehension of impact of meteorological factors on Anopheles darlingi Root, the main malaria vector, are necessary. Anopheline mosquitoes were collected continuously during 2012 and 2013 using Mosquito Magnet traps baited with octenol and human landing catches. The two methods were compared based on trends in abundance and parity rate of An. darlingi. Impact of meteorological factors on An. darlingi density estimates was investigated using Spearman's correlation and by binomial negative regression analysis. In all, 11,928 anopheline mosquitoes were collected, and 90.7% (n = 10,815) were identified consisting of four species, with An. darlingi making up 94.9% (n = 10,264). An. darlingi specimens collected by the two methods were significantly correlated, and no difference in parity rate was observed. The abundance of this species peaked in September (dry season) and variations along the years were influenced by relative humidity, temperature, rainfall, and wind speed. Number of mosquitoes collected during peak aggression period was influenced by wind speed and rainfall. Data gathered in this study provide fundamental information about An. darlingi, which can facilitate the design of vector control strategies and construction of models for predicting malaria risk. © The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Tropical Montane Cloud Forests: Hydrometeorological variability in three neighbouring catchments with different forest cover

NASA Astrophysics Data System (ADS)

Ramírez, Beatriz H.; Teuling, Adriaan J.; Ganzeveld, Laurens; Hegger, Zita; Leemans, Rik

2017-09-01

Mountain areas are characterized by a large heterogeneity in hydrological and meteorological conditions. This heterogeneity is currently poorly represented by gauging networks and by the coarse scale of global and regional climate and hydrological models. Tropical Montane Cloud Forests (TMCFs) are found in a narrow elevation range and are characterized by persistent fog. Their water balance depends on local and upwind temperatures and moisture, therefore, changes in these parameters will alter TMCF hydrology. Until recently the hydrological functioning of TMCFs was mainly studied in coastal regions, while continental TMCFs were largely ignored. This study contributes to fill this gap by focusing on a TMCF which is located on the northern eastern Andes at an elevation of 1550-2300 m asl, in the Orinoco river basin highlands. In this study, we describe the spatial and seasonal meteorological variability, analyse the corresponding catchment hydrological response to different land cover, and perform a sensitivity analysis on uncertainties related to rainfall interpolation, catchment area estimation and streamflow measurements. Hydro-meteorological measurements, including hourly solar radiation, temperature, relative humidity, wind speed, precipitation, soil moisture and streamflow, were collected from June 2013 to May 2014 at three gauged neighbouring catchments with contrasting TMCF/grassland cover and less than 250 m elevation difference. We found wetter and less seasonally contrasting conditions at higher elevations, indicating a positive relation between elevation and fog or rainfall persistence. This pattern is similar to that of other eastern Andean TMCFs, however, the study site had higher wet season rainfall and lower dry season rainfall suggesting that upwind contrasts in land cover and moisture can influence the meteorological conditions at eastern Andean TMCFs. Contrasting streamflow dynamics between the studied catchments reflect the overall system response as a function of the catchments' elevation and land cover. The forested catchment, located at the higher elevations, had the highest seasonal streamflows. During the wet season, different land covers at the lower elevations were important in defining the streamflow responses between the deforested catchment and the catchment with intermediate forest cover. Streamflows were higher and the rainfall-runoff responses were faster in the deforested catchment than in the intermediate forest cover catchment. During the dry season, the catchments' elevation defined streamflows due to higher water inputs and lower evaporative demand at the higher elevations.

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.

Vegetative and reproductive phenology of a floodplain tree species Barringtonia acutangula from North East India.

PubMed

Nath, Shikhasmita; Nath, Arun Jyoti; Das, Ashesh Kumar

2016-03-01

Vegetative and reproductive phenology of Barringtonia acutangula, a floodplain tree species was studied at Chatla floodplain, Assam North East India with the aim to investigate vegetative and reproductive phenology under stressful environment of seasonal submergence and to assess the impact of environmental variables (temperature and precipitation) on tree phenophases. Quantitative assessment was made at 15 day interval for all the phenophases (leaf initiation, leaf-fall, flowering and fruiting) by tagging 40 (forty) trees over aperiod of two years (2012-14).To test seasonal influence on the phenology of Barringtonia acutangula different phenophases were correlated with environmental variables and statistical spearman's rank correlation coefficient was employed. Aridity index was computed that delineate influence of rainfall and temperature together on any phenophases. Leaf initiation showed positively significant correlation with temperature (r(s) = 0.601, p = < .05) during the year 2012-2013 whereas it was significantly correlated with rainfall (r(s) = 0.583, p = < .05) and aridity index (r(s) = 0.583, p = < .05) during the year 2013-2014. Leaf-fall was significant negatively correlated with temperature (r(s) = -0.623, p = < .05), rainfall (r(s) = -0.730, p = < .01) and aridity index (r(s) = -0.730, p = < .01) for both the studied years. Flowering was significantly influenced by temperature (r(s) = 0.639, p = < .05), rainfall (r(s) = 0.890, p = < .01) and aridity index (r(s) = 0.890, p = < .01) while in one month lag flowering was significantly correlated with rainfall (r(s) = 0.678, p = < .01) in 2012-13. Fruiting was also positively significant with temperature (r(s) = 0.795, P < .05), rainfall (r(s) = 0.835, P < .01) and aridity index (r(s) = 0.835, P < .01) for both the years. During one month lag period fruiting was positively correlated with temperature, rainfall and aridity index in both the years. Temperature, rainfall and aridity index were major determinants of the various vegetative and reproductive phenology of B. acutangula and any changes in these variables in future due to climate change, might have profound effect on phenophases of this tree species.

Intra-seasonal rainfall characteristics and their importance to the seasonal prediction problem

NASA Astrophysics Data System (ADS)

Tennant, Warren J.; Hewitson, Bruce C.

2002-07-01

Daily station rainfall data in South Africa from 1936 to 1999 are combined into homogeneous rainfall regions using Ward's clustering method. Various rainfall characteristics are calculated for the summer season, defined as December to February. These include seasonal rainfall total, region-average number of station rain days exceeding 1 and 20 mm, region-average of periods between rain days at stations >1 and >20 mm, region-average of wet spell length (sequential days of station rainfall >1 and >20 mm), correlation of daily station rainfall within a region and correlation of seasonal station rainfall anomalies within a region.Rank-ordered rainfall characteristic data generally form an s-shaped curve, and significance testing of discontinuities in these curves suggests that normal rainfall conditions in South Africa consist of a combined middle three quintiles separated from the outer quintiles, rather than the traditional middle tercile.The relationships between the various rainfall characteristics show that seasons with a high total rainfall generally have a higher number of heavy rain days (>20 mm) and not necessarily an increase in light rain days. The length of the period between rain days has a low correlation to season totals, demonstrating that seasons with a high total rainfall may still contain prolonged dry periods. These additional rainfall characteristics are important to end-users, and the analysis undertaken here offers a valuable starting point for seeking physical relationships between rainfall characteristics and the general circulation. Preliminary studies show that the vertical mean wind is related to rainfall characteristics in South Africa. Given that general circulation models capture this part of the circulation adequately, seasonal forecasts of rainfall characteristics become plausible.

Complexity confers stability: Climate variability, vegetation response and sand transport on longitudinal sand dunes in Australia's deserts

NASA Astrophysics Data System (ADS)

Hesse, Paul P.; Telfer, Matt W.; Farebrother, Will

2017-04-01

The relationship between antecedent precipitation, vegetation cover and sand movement on sand dunes in the Simpson and Strzelecki Deserts was investigated by repeated (up to four) surveys of dune crest plots (≈25 × 25 m) over a drought cycle (2002-2012) in both winter (low wind) and spring (high wind). Vegetation varied dramatically between surveys on vegetated and active dune crests. Indices of sand movement had significant correlations with vegetation cover: the depth of loose sand has a strong inverse relationship with crust (cyanobacterial and/or physical) while the area covered by ripples has a strong inverse relationship with the areal cover of vascular plants. However, the relationship between antecedent rainfall and vegetation cover was found to be complex. We tentatively identify two thresholds; (1) >10 mm of rainfall in the preceding 90 days leads to rapid and near total cover of crust and/or small plants <50 cm tall, and (2) >400 mm of rainfall in the preceding three years leads to higher cover of persistent and longer-lived plants >50 cm tall. These thresholds were used to predict days of low vegetation cover on dune crests. The combination of seasonality of predicted bare-crest days, potential sand drift and resultant sand drift direction explains observed patterns of sand drift on these dunes. The complex vegetation and highly variable rainfall regime confer meta-stability on the dunes through the range of responses to different intervals of antecedent rainfall and non-linear growth responses. This suggests that the geomorphic response of dunes to climate variation is complex and non-linear.

Evaluating the catching performance of aerodynamic rain gauges through field comparisons and CFD modelling

NASA Astrophysics Data System (ADS)

Pollock, Michael; Colli, Matteo; Stagnaro, Mattia; Lanza, Luca; Quinn, Paul; Dutton, Mark; O'Donnell, Greg; Wilkinson, Mark; Black, Andrew; O'Connell, Enda

2016-04-01

Accurate rainfall measurement is a fundamental requirement in a broad range of applications including flood risk and water resource management. The most widely used method of measuring rainfall is the rain gauge, which is often also considered to be the most accurate. In the context of hydrological modelling, measurements from rain gauges are interpolated to produce an areal representation, which forms an important input to drive hydrological models and calibrate rainfall radars. In each stage of this process another layer of uncertainty is introduced. The initial measurement errors are propagated through the chain, compounding the overall uncertainty. This study looks at the fundamental source of error, in the rainfall measurement itself; and specifically addresses the largest of these, the systematic 'wind-induced' error. Snowfall is outside the scope. The shape of a precipitation gauge significantly affects its collection efficiency (CE), with respect to a reference measurement. This is due to the airflow around the gauge, which causes a deflection in the trajectories of the raindrops near the gauge orifice. Computational Fluid-Dynamic (CFD) simulations are used to evaluate the time-averaged airflows realized around the EML ARG100, EML SBS500 and EML Kalyx-RG rain gauges, when impacted by wind. These gauges have a similar aerodynamic profile - a shape comparable to that of a champagne flute - and they are used globally. The funnel diameter of each gauge, respectively, is 252mm, 254mm and 127mm. The SBS500 is used by the UK Met Office and the Scottish Environmental Protection Agency. Terms of comparison are provided by the results obtained for standard rain gauge shapes manufactured by Casella and OTT which, respectively, have a uniform and a tapered cylindrical shape. The simulations were executed for five different wind speeds; 2, 5, 7, 10 and 18 ms-1. Results indicate that aerodynamic gauges have a different impact on the time-averaged airflow patterns observed in the vicinity of the collector, compared to the standard gauge shapes. Both the air velocity and the turbulent kinetic energy fields present structures that may improve the interception of particles by the aerodynamic gauge collector. To provide empirical validation, a field-based experimental campaign was undertaken at four UK research stations to compare the results of aerodynamic and conventional gauges, mounted in juxtaposition. The reference measurement is recorded using a rain gauge pit, as specified by the WMO. The results appear to demonstrate how the effect of the wind on rainfall measurements is influenced by the gauge shape and the mounting height. Significant undercatch is observed compared to the reference measurement. Aerodynamic gauges mounted on the ground catch more rainfall than juxtaposed straight-sided gauges, in most instances. This appears to provide some preliminary validation of the CFD model. The indication that an aerodynamic profile improves the gauge catching capability could be confirmed by tracking the hydrometeor trajectories with a Lagrangian method, based on the available set of airflows; and investigating time-dependent aerodynamic features by means of dedicated CFD simulations. Furthermore, wind-tunnel tests could be carried out to provide more robust physical validation of the CFD model.

Hurricane Hector in the Eastern Pacific

NASA Image and Video Library

2006-08-17

Infrared, microwave, and visible/near-infrared images of Hurricane Hector in the eastern Pacific were created with data from the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite on August 17, 2006. The infrared AIRS image shows the temperature of the cloud tops or the surface of the Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the hurricane. The infrared signal does not penetrate through clouds. Where there are no clouds the AIRS instrument reads the infrared signal from the surface of the Earth, revealing warmer temperatures (red). At the time the data were taken from which these images were made, Hector is a well organized storm, with the strongest convection in the SE quadrant. The increasing vertical wind shear in the NW quadrant is appearing to have an effect. Maximum sustained winds are at 85 kt, gusts to 105 kt. Estimated minimum central pressure is 975 mbar. The microwave image is created from microwave radiation emitted by Earth's atmosphere and received by the instrument. It shows where the heaviest rainfall is taking place (in blue) in the storm. Blue areas outside of the storm where there are either some clouds or no clouds, indicate where the sea surface shines through. The "visible" image is created from data acquired by the visible light/near-infrared sensor on the AIRS instrument. http://photojournal.jpl.nasa.gov/catalog/PIA00507

Diurnal variations of summer precipitation over the regions east to Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wu, Yang; Huang, Anning; Huang, Danqing; Chen, Fei; Yang, Ben; Zhou, Yang; Fang, Dexian; Zhang, Lujun; Wen, Lijuan

2017-12-01

Based on the hourly gauge-satellite merged precipitation product with the horizontal resolution of 0.1° latitude/longitude during 2008-2014, diurnal variations of the summer precipitation amount (PA), frequency (PF), and intensity (PI) with different duration time over the regions east to Tibetan Plateau have been systematically revealed in this study. Results indicate that the eight typical precipitation diurnal patterns identified by the cluster analysis display pronounced regional features among the plateaus, basins, plains, hilly and coastal areas. The precipitation diurnal cycles are significantly affected by the sub-grid terrain fluctuations. The PA, PF and PI of the total rainfall show much more pronounced double diurnal peaks with the sub-grid topography standard deviation (SD) decreased. Meanwhile, the diurnal peaks of PA and PF (PI) strengthen (weaken) with the sub-grid topography SD enhanced. Over the elevated mountain ranges, southeastern hilly and coastal regions, the PA and PF diurnal patterns of the total rainfall generally show predominant late-afternoon peaks, which are closely associated with the short-duration (≤slant 3 h) rainfall. Along the Tibetan Plateau to its downstream, the diurnal peaks of PA, PF and PI for the total rainfall all exhibit obvious eastward phase time delay mainly due to the diurnal evolutions of long-duration (> 6 h) rainfall. However, the 4-6 h rainfall leads to the eastward phase time delay of the total rainfall along the Taihang Mountains to its downstream. Further mechanism analysis suggests that the midnight to morning diurnal evolution of the long-duration rainfall is closely associated with the diurnal variations of the upward branches of thermally driven mountain-plain solenoids and the water vapor transport associated with the accelerated nocturnal southwesterly winds. The late-afternoon peak of the short-duration PA over the southeastern hilly and coastal regions is ascribed to the strong local thermal convections due to the solar heating in afternoon, while the early-evening peak of the short-duration PA over the elevated mountain ranges is significantly contributed by the upward warm-moist wind from the surrounding low-lying basins or plains.

Role of cold surge and MJO on rainfall enhancement over indonesia during east asian winter monsoon

NASA Astrophysics Data System (ADS)

Fauzi, R. R.; Hidayat, R.

2018-05-01

Intensity of precipitation in Indonesia is influenced by convection and propagation of southwest wind. Objective of this study is to analyze the relationship between cold surge and the phenomenon of intra-seasonal climate variability Madden-julian Oscillation (MJO) for affecting precipitation in Indonesia. The data used for identifying the occurrence of cold surge are meridional wind speed data from the ERA-Interim. In addition, this study also used RMM1 and RMM2 index data from Bureau of Meteorology (BOM) for identifying MJO events. The results showed that during East Asian Winter Monsoon (EAWM) in 15 years (2000-2015), there are 362 cold surge events, 186 MJO events, and 113 cold surge events were associated with MJO events. The spread of cold surge can penetrate to equator and brought mass of water vapor that causes dominant precipitation in the Indonesian Sea up to 50-75% from climatological precipitation during EAWM. The MJO convection activity that moves from west to east also increases precipitation, but the distribution of rainfall is wider than cold surge, especially in Eastern Indonesia. MJO and cold surge simultaneously can increase rainfall over 100-150% in any Indonesian region that affected by MJO and cold surge events. The mechanism of heavy rainfall is illustrated by high activity of moisture transport in areas such as Java Sea and coastal areas of Indonesia.

A Multiseason Comparison of the Forecast Skills among Three Numerical Models over Southcentral United States

NASA Astrophysics Data System (ADS)

Lu, D.; Reddy, S.

2005-05-01

During the summer 2003 and winter 2003-2004, three mesoscale numerical models, the fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5), Navy's Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPS) and the Weather Research and Forecasting model (WRF), were operationally run at a horizontal resolution of 27 km twice daily in Jackson State University (JSU). Three models were run by the initial and lateral boundary conditions from AVN data. The purpose of this paper is to evaluate the performances of three models during these two seasons. It was found that the temporal variation of distribution and strength of mean error (ME) biases at 12, 24 and 36h was rather weak for surface temperature, sea level pressure and surface wind speed. During two seasons, the MM5 underpredicted the seasonal precipitation while the COAMPS and WRF overpredicted. This is consistent with the statistical score analyses of rainfall. The Bias scores revealed that the MM5 yielded an underprediction of precipitation, especially for heavier rainfall events. Due to the under estimate of rainfall areas and strength, the MM5 presented the lower TS, POD and KSS scores at lighter rainfall events compared to the COAMPS and WRF. At moderate to heavier thresholds, three models produced rather low KSS and POD scores that are consistent with the high FAR values. The WRF skills in predicting precipitation heavily depend on the performance of cumulus parameterization scheme. Instead of Kain-Fritsch scheme, using other two schemes, Grell-Devenyi and Bette-Miller-Janjic, in the WRF for warm season 2003 demonstrated that the precipitation overprediction had been efficiently suppressed. Overall, the performances of three models revealed that the best skill is at 12h and the worst at 36h.

The association of weather and mortality in Bangladesh from 1983–2009

PubMed Central

Alam, Nurul; Begum, Dilruba; Streatfield, Peter Kim

2012-01-01

Introduction The association of weather and mortality have not been widely studied in subtropical monsoon regions, particularly in Bangladesh. This study aims to assess the association of weather and mortality (measured with temperature and rainfall), adjusting for time trend and seasonal patterns in Abhoynagar, Bangladesh. Material and methods A sample vital registration system (SVRS) was set up in 1982 to facilitate operational research in family planning and maternal and child health. SVRS provided data on death counts and population from 1983–2009. The Bangladesh Meteorological Department provided data on daily temperature and rainfall for the same period. Time series Poisson regression with cubic spline functions was used, allowing for over-dispersion, including lagged weather parameters, and adjusting for time trends and seasonal patterns. Analysis was carried out using R statistical software. Results Both weekly mean temperature and rainfall showed strong seasonal patterns. After adjusting for seasonal pattern and time trend, weekly mean temperatures (lag 0) below the 25th percentile and between the 25th and 75th percentiles were associated with increased mortality risk, particularly in females and adults aged 20–59 years by 2.3–2.4% for every 1°C decrease. Temperature above the 75th percentile did not increase the risk. Every 1 mm increase in rainfall up to 14 mm of weekly average rainfall over lag 0–4 weeks was associated with decreased mortality risks. Rainfall above 14 mm was associated with increased mortality risk. Conclusion The relationships between temperature, rainfall and mortality reveal the importance of understanding the current factors contributing to adaptation and acclimatization, and how these can be enhanced to reduce negative impacts from weather. PMID:23195512

Spatio-temporal heterogeneity of malaria morbidity in Ghana: Analysis of routine health facility data

PubMed Central

Malm, Keziah; Peprah, Nana Yaw; Silal, Sheetal P.

2018-01-01

Background Malaria incidence is largely influenced by vector abundance. Among the many interconnected factors relating to malaria transmission, weather conditions such as rainfall and temperature are known to create suitable environmental conditions that sustain reproduction and propagation of anopheles mosquitoes and malaria parasites. In Ghana, climatic conditions vary across the country. Understanding the heterogeneity of malaria morbidity using data sourced from a recently setup data repository for routine health facility data could support planning. Methods Monthly aggregated confirmed uncomplicated malaria cases from the District Health Information Management System and average monthly rainfall and temperature records obtained from the Ghana Meteorological Agency from 2008 to 2016 were analysed. Univariate time series models were fitted to the malaria, rainfall and temperature data series. After pre-whitening the morbidity data, cross correlation analyses were performed. Subsequently, transfer function models were developed for the relationship between malaria morbidity and rainfall and temperature. Results Malaria morbidity patterns vary across zones. In the Guinea savannah, morbidity peaks once in the year and twice in both the Transitional forest and Coastal savannah, following similar patterns of rainfall at the zonal level. While the effects of rainfall on malaria morbidity are delayed by a month in the Guinea savannah and Transitional Forest zones those of temperature are delayed by two months in the Transitional forest zone. In the Coastal savannah however, incidence of malaria is significantly associated with two months lead in rainfall and temperature. Conclusion Data captured on the District Health Information Management System has been used to demonstrate heterogeneity in the dynamics of malaria morbidity across the country. Timing of these variations could guide the deployment of interventions such as indoor residual spraying, Seasonal Malaria Chemoprevention or vaccines to optimise effectiveness on zonal basis. PMID:29377908

Spatio-temporal heterogeneity of malaria morbidity in Ghana: Analysis of routine health facility data.

PubMed

Awine, Timothy; Malm, Keziah; Peprah, Nana Yaw; Silal, Sheetal P

2018-01-01

Malaria incidence is largely influenced by vector abundance. Among the many interconnected factors relating to malaria transmission, weather conditions such as rainfall and temperature are known to create suitable environmental conditions that sustain reproduction and propagation of anopheles mosquitoes and malaria parasites. In Ghana, climatic conditions vary across the country. Understanding the heterogeneity of malaria morbidity using data sourced from a recently setup data repository for routine health facility data could support planning. Monthly aggregated confirmed uncomplicated malaria cases from the District Health Information Management System and average monthly rainfall and temperature records obtained from the Ghana Meteorological Agency from 2008 to 2016 were analysed. Univariate time series models were fitted to the malaria, rainfall and temperature data series. After pre-whitening the morbidity data, cross correlation analyses were performed. Subsequently, transfer function models were developed for the relationship between malaria morbidity and rainfall and temperature. Malaria morbidity patterns vary across zones. In the Guinea savannah, morbidity peaks once in the year and twice in both the Transitional forest and Coastal savannah, following similar patterns of rainfall at the zonal level. While the effects of rainfall on malaria morbidity are delayed by a month in the Guinea savannah and Transitional Forest zones those of temperature are delayed by two months in the Transitional forest zone. In the Coastal savannah however, incidence of malaria is significantly associated with two months lead in rainfall and temperature. Data captured on the District Health Information Management System has been used to demonstrate heterogeneity in the dynamics of malaria morbidity across the country. Timing of these variations could guide the deployment of interventions such as indoor residual spraying, Seasonal Malaria Chemoprevention or vaccines to optimise effectiveness on zonal basis.

Indo-Pacific climate during the decaying phase of the 2015/16 El Niño: role of southeast tropical Indian Ocean warming

NASA Astrophysics Data System (ADS)

Chen, Zesheng; Du, Yan; Wen, Zhiping; Wu, Renguang; Wang, Chunzai

2018-06-01

This study investigates the influence of southeast tropical Indian Ocean (SETIO) sea surface temperature (SST) warming on Indo-Pacific climate during the decaying phase of the 2015/16 El Niño by using observations and model experiments. The results show that the SETIO SST warming in spring 2016 enhanced local convection and forced a "C-shape" wind anomaly pattern in the lower troposphere. The "C-shape" wind anomaly pattern over the eastern tropical Indian Ocean consists of anomalous westerly flow south of the equator and anomalous easterly flow north of the equator. The anomalous easterly flow then extended eastward into the western North Pacific (WNP) and facilitates the development or the maintenance of an anomalous anticyclone over the South China Sea (SCS). Correspondingly, the eastern part of the Bay of Bengal, the SCS and the WNP suffered less rainfall. Such precipitation features and the associated "C-shape" wind anomaly pattern shifted northward about five latitudes in summer 2016. Additionally, the SETIO warming can induce local meridional circulation anomalies, which directly affect Indo-Pacific climate. Numerical model experiments further confirm that the SETIO SST warming plays an important role in modulating Indo-Pacific climate.

Droplet Size Distributions as a function of rainy system type and Cloud Condensation Nuclei concentrations

NASA Astrophysics Data System (ADS)

Cecchini, Micael A.; Machado, Luiz A. T.; Artaxo, Paulo

2014-06-01

This work aims to study typical Droplet Size Distributions (DSDs) for different types of precipitation systems and Cloud Condensation Nuclei concentrations over the Vale do Paraíba region in southeastern Brazil. Numerous instruments were deployed during the CHUVA (Cloud processes of tHe main precipitation systems in Brazil: a contribUtion to cloud resolVing modeling and to the GPM) Project in Vale do Paraíba campaign, from November 22, 2011 through January 10, 2012. Measurements of CCN (Cloud Condensation Nuclei) and total particle concentrations, along with measurements of rain DSDs and standard atmospheric properties, including temperature, pressure and wind intensity and direction, were specifically made in this study. The measured DSDs were parameterized with a gamma function using the moment method. The three gamma parameters were disposed in a 3-dimensional space, and subclasses were classified using cluster analysis. Seven DSD categories were chosen to represent the different types of DSDs. The DSD classes were useful in characterizing precipitation events both individually and as a group of systems with similar properties. The rainfall regime classification system was employed to categorize rainy events as local convective rainfall, organized convection rainfall and stratiform rainfall. Furthermore, the frequencies of the seven DSD classes were associated to each type of rainy event. The rainfall categories were also employed to evaluate the impact of the CCN concentration on the DSDs. In the stratiform rain events, the polluted cases had a statistically significant increase in the total rain droplet concentrations (TDCs) compared to cleaner events. An average concentration increase from 668 cm- 3 to 2012 cm- 3 for CCN at 1% supersaturation was found to be associated with an increase of approximately 87 m- 3 in TDC for those events. For the local convection cases, polluted events presented a 10% higher mass weighted mean diameter (Dm) on average. For the organized convection events, no significant results were found.

A global slowdown of tropical-cyclone translation speed.

PubMed

Kossin, James P

2018-06-01

As the Earth's atmosphere warms, the atmospheric circulation changes. These changes vary by region and time of year, but there is evidence that anthropogenic warming causes a general weakening of summertime tropical circulation 1-8 . Because tropical cyclones are carried along within their ambient environmental wind, there is a plausible a priori expectation that the translation speed of tropical cyclones has slowed with warming. In addition to circulation changes, anthropogenic warming causes increases in atmospheric water-vapour capacity, which are generally expected to increase precipitation rates 9 . Rain rates near the centres of tropical cyclones are also expected to increase with increasing global temperatures 10-12 . The amount of tropical-cyclone-related rainfall that any given local area will experience is proportional to the rain rates and inversely proportional to the translation speeds of tropical cyclones. Here I show that tropical-cyclone translation speed has decreased globally by 10 per cent over the period 1949-2016, which is very likely to have compounded, and possibly dominated, any increases in local rainfall totals that may have occurred as a result of increased tropical-cyclone rain rates. The magnitude of the slowdown varies substantially by region and by latitude, but is generally consistent with expected changes in atmospheric circulation forced by anthropogenic emissions. Of particular importance is the slowdown of 30 per cent and 20 per cent over land areas affected by western North Pacific and North Atlantic tropical cyclones, respectively, and the slowdown of 19 per cent over land areas in the Australian region. The unprecedented rainfall totals associated with the 'stall' of Hurricane Harvey 13-15 over Texas in 2017 provide a notable example of the relationship between regional rainfall amounts and tropical-cyclone translation speed. Any systematic past or future change in the translation speed of tropical cyclones, particularly over land, is therefore highly relevant when considering potential changes in local rainfall totals.

Could Malaria Control Programmes be Timed to Coincide with Onset of Rainfall?

PubMed

Komen, Kibii

2017-06-01

Malaria cases in South Africa's Northern Province of Limpopo have surpassed known endemic KwaZulu Natal and Mpumalanga Provinces. This paper applies statistical methods: regression analysis and impulse response function to understand the timing of impact and the length that such impacts last. Climate data (rainfall and temperature) are obtained from South African Weather Services (SAWs); global data from the European Centre for Medium-Range Weather Forecasts (ECMWF), while clinical malaria data came from Malaria Control Centre in Tzaneen (Limpopo Province). Data collected span from January 1998 to July 2007. Signs of the coefficients are positive for rainfall and temperature and negative for their exponents. Three out of five independent variables consistently maintain a very high statistical level of significance. The coefficients for climate variables describe an inverted u-shape: parameters for the exponents of rainfall (-0.02, -0.01, -0.02, -0.00) and temperature (-46.61, -47.46, -48.14, -36.04) are both negative. A one standard deviation rise in rainfall (rainfall onset) increases malaria cases, and the effects become sustained for at least 3 months and conclude that onset of rainfall therefore triggers a 'malaria season'. Malaria control programme and early warning system should be intensified in the first 3 months following the onset of rainfall.

Long-run relative importance of temperature as the main driver to malaria transmission in Limpopo Province, South Africa: a simple econometric approach.

PubMed

Komen, Kibii; Olwoch, Jane; Rautenbach, Hannes; Botai, Joel; Adebayo, Adetunji

2015-03-01

Malaria in Limpopo Province of South Africa is shifting and now observed in originally non-malaria districts, and it is unclear whether climate change drives this shift. This study examines the distribution of malaria at district level in the province, determines direction and strength of the linear relationship and causality between malaria with the meteorological variables (rainfall and temperature) and ascertains their short- and long-run variations. Spatio-temporal method, Correlation analysis and econometric methods are applied. Time series monthly meteorological data (1998-2007) were obtained from South Africa Weather Services, while clinical malaria data came from Malaria Control Centre in Tzaneen (Limpopo Province) and South African Department of Health. We find that malaria changes and pressures vary in different districts with a strong positive correlation between temperature with malaria, r = 0.5212, and a weak positive relationship for rainfall, r = 0.2810. Strong unidirectional causality runs from rainfall and temperature to malaria cases (and not vice versa): F (1, 117) = 3.89, ρ = 0.0232 and F (1, 117) = 20.08, P < 0.001 and between rainfall and temperature, a bi-directional causality exists: F (1, 117) = 19.80; F (1,117) = 17.14, P < 0.001, respectively, meaning that rainfall affects temperature and vice versa. Results show evidence of strong existence of a long-run relationship between climate variables and malaria, with temperature maintaining very high level of significance than rainfall. Temperature, therefore, is more important in influencing malaria transmission in Limpopo Province.

Continental Tele-connections of ET and Precipitation: Tractable Models, Viable Management, and Potential Monitoring.

NASA Astrophysics Data System (ADS)

Selker, J. S.; Higgins, C. W.; Tai, L. C. M.

2014-12-01

The linkage between large-scale manipulation of land cover and resulting patterns of precipitation has been a long-standing problem. For example, what is the impact of the Columbia River project's 2,700 km^2 irrigated area (applying approximately 300 m^3/s) on the down-wind continental rainfall in North America? Similarly, can we identify places on earth where planting large-scale runoff-reducing forests might increase down-wind precipitation, thus leading to magnified carbon capture? In this talk we present an analytical Lagrangian framework for the prediction of incremental increases in down-wind precipitation due to land surface evaporation and transpiration. We compare these predictions to recently published rainfall recycling values from the literature. Focus is on the Columbia basin (Pacific Northwest of hte USA), with extensions to East Africa. We further explore the monitoring requirements for verification of any such impact, and see if the planned TAHMO African Observatory (TAHMO.org) has the potential to document any such processes over the 25-year and 1,000 km scales.

A vectorial capacity product to monitor changing malaria transmission potential in epidemic regions of Africa

USGS Publications Warehouse

Ceccato, Pietro; Vancutsem, Christelle; Klaver, Robert; Rowland, James; Connor, Stephen J.

2012-01-01

Rainfall and temperature are two of the major factors triggering malaria epidemics in warm semi-arid (desert-fringe) and high altitude (highland-fringe) epidemic risk areas. The ability of the mosquitoes to transmit Plasmodium spp. is dependent upon a series of biological features generally referred to as vectorial capacity. In this study, the vectorial capacity model (VCAP) was expanded to include the influence of rainfall and temperature variables on malaria transmission potential. Data from two remote sensing products were used to monitor rainfall and temperature and were integrated into the VCAP model. The expanded model was tested in Eritrea and Madagascar to check the viability of the approach. The analysis of VCAP in relation to rainfall, temperature and malaria incidence data in these regions shows that the expanded VCAP correctly tracks the risk of malaria both in regions where rainfall is the limiting factor and in regions where temperature is the limiting factor. The VCAP maps are currently offered as an experimental resource for testing within Malaria Early Warning applications in epidemic prone regions of sub-Saharan Africa. User feedback is currently being collected in preparation for further evaluation and refinement of the VCAP model.

Decision Support Tool Evaluation Report for Coral Reef Early Warning System (CREWS) Version 7.0

NASA Technical Reports Server (NTRS)

D'Sa, Eurico; Hall, Callie; Zanoni, Vicki; Holland, Donald; Blonski, Slawomir; Pagnutti, Mary; Spruce, Joseph P.

2004-01-01

The Coral Reef Early Warning System (CREWS) is operated by NOAA's Office of Oceanic and Atmospheric Research as part of its Coral Reef Watch program in response to the deteriorating global state of coral reef and related benthic ecosystems. In addition to sea surface temperatures (SSTs), the two most important parameters used by the CREWS network in generating coral reef bleaching alerts are 1) wind speed and direction and 2) photosynthetically available radiation (PAR). NASA remote sensing products that can enhance CREWS in these areas include SST and PAR products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and wind data from the Quick Scatterometer (QuikSCAT). CREWS researchers are also interested in chlorophyll, chromophoric dissolved organic matter (CDOM), and salinity. Chlorophyll and CDOM are directly available as NASA products, while rainfall (an available NASA product) can be used as a proxy for salinity. Other potential NASA inputs include surface reflectance products from MODIS, the Advanced Spaceborne Thermal Emission and Reflection Radiometer, and Landsat. This report also identifies NASA-supported ocean circulation models and products from future satellite missions that might enchance the CREWS DST.

Daily weather variables and affective disorder admissions to psychiatric hospitals

NASA Astrophysics Data System (ADS)

McWilliams, Stephen; Kinsella, Anthony; O'Callaghan, Eadbhard

2014-12-01

Numerous studies have reported that admission rates in patients with affective disorders are subject to seasonal variation. Notwithstanding, there has been limited evaluation of the degree to which changeable daily meteorological patterns influence affective disorder admission rates. A handful of small studies have alluded to a potential link between psychiatric admission rates and meteorological variables such as environmental temperature (heat waves in particular), wind direction and sunshine. We used the Kruskal-Wallis test, ARIMA and time-series regression analyses to examine whether daily meteorological variables—namely wind speed and direction, barometric pressure, rainfall, hours of sunshine, sunlight radiation and temperature—influence admission rates for mania and depression across 12 regions in Ireland over a 31-year period. Although we found some very weak but interesting trends for barometric pressure in relation to mania admissions, daily meteorological patterns did not appear to affect hospital admissions overall for mania or depression. Our results do not support the small number of papers to date that suggest a link between daily meteorological variables and affective disorder admissions. Further study is needed.

Aircraft Observations of Soil Hydrological Influence on the Atmosphere in Northern India

NASA Astrophysics Data System (ADS)

Taylor, Christopher M.; Barton, Emma J.; Belusic, Danijel; Böing, Steven J.; Hunt, Kieran M. R.; Mitra, Ashis K.; Parker, Douglas J.; Turner, Andrew G.

2017-04-01

India is considered to be a region of the world where the influence of land surface fluxes of sensible and latent heat play an important role in regional weather and climate. Indian rainfall simulations in GCMs are known to be particularly sensitive to soil moisture. However, in a monsoon region where seasonal convective rainfall dominates, it is a big challenge for GCMs to capture, on the one hand, a realistic depiction of surface fluxes during wetting up and drying down at seasonal and sub-seasonal scales, and on the other, the sensitivity of convective rainfall and regional circulations to space-time fluctuations in land surface fluxes. On top of this, most GCMs and operational atmospheric forecast models don't explicitly consider irrigation. In the Indo-Gangetic plains of the Indian sub-continent, irrigated agriculture has become the dominant land use. Irrigation suppresses temporal flux variability for much of the year, and at the same time enhances spatial heterogeneity. One of the key objectives of the Anglo-Indian Interaction of Convective Organization and Monsoon Precipitation, Atmosphere, Surface and Sea (INCOMPASS) collaborative project is to better understand the coupling between the land surface and the Indian summer monsoon, and build this understanding into improved prediction of rainfall on multiple time and space scales. During June and July 2016, a series of research flights was performed across the sub-continent using the NERC/Met Office BAe146 aircraft. Here we will present results for a case study from a flight on 30th June which sampled the Planetary Boundary Layer (PBL) on a 700 km low level transect, from the semi-arid region of Rajasthan eastwards into the extensively irrigated state of Uttar Pradesh. As well as crossing different land uses, the flight also sampled mesoscale regions with contrasting recent rainfall conditions. Here we will show how variations in surface hydrology, driven by both irrigation and rainfall, influence the temperature, humidity and winds in the PBL. These unique observations will provide a powerful tool for understanding the dominant land-atmosphere coupling mechanisms operating on a range of multiple length scales, and which help to shape the Indian monsoon.

South Asian Summer Monsoon Rainfall Variability and Trend: Its Links to Indo-Pacific SST Anomalies and Moist Processes

NASA Astrophysics Data System (ADS)

Prasanna, V.

2016-06-01

The warm (cold) phase of El Niño (La Niña) and its impact on all Indian Summer Monsoon rainfall (AISMR) relationship is explored for the past 100 years. The 103-year (1901-2003) data from the twentieth century reanalysis datasets (20CR) and other major reanalysis datasets for southwest monsoon season (JJAS) is utilized to find out the simultaneous influence of the El Niño Southern Oscillation (ENSO)-AISMR relationship. Two cases such as wet, dry monsoon years associated with ENSO(+) (El Niño), ENSO(-) (La Niña) and Non-ENSO (neutral) events have been discussed in detail using observed rainfall and three-dimensional 20CR dataset. The dry and wet years associated with ENSO and Non-ENSO periods show significant differences in the spatial pattern of rainfall associated with three-dimensional atmospheric composite, the 20CR dataset has captured the anomalies quite well. During wet (dry) years, the rainfall is high (low), i.e. 10 % above (below) average from the long-term mean and this wet or dry condition occur both during ENSO and Non-ENSO phases. The Non-ENSO year dry or wet composites are also focused in detail to understand, where do the anomalous winds come from unlike in the ENSO case. The moisture transport is coherent with the changes in the spatial pattern of AISMR and large-scale feature in the 20CR dataset. Recent 50-year trend (1951-2000) is also analyzed from various available observational and reanalysis datasets to see the influence of Indo-Pacific SST and moist processes on the South Asian summer monsoon rainfall trend. Apart from the Indo-Pacific sea surface temperatures (SST), the moisture convergence and moisture transport among India (IND), Equatorial Indian Ocean (IOC) and tropical western pacific (WNP) is also important in modifying the wet or dry cycles over India. The mutual interaction among IOC, WNP and IND in seasonal timescales is significant in modifying wet and dry cycles over the Indian region and the seasonal anomalies.

People, El Niño southern oscillation and fire in Australia: fire regimes and climate controls in hummock grasslands

PubMed Central

Bird, Douglas W.; Codding, Brian F.

2016-01-01

While evidence mounts that indigenous burning has a significant role in shaping pyrodiversity, the processes explaining its variation across local and external biophysical systems remain limited. This is especially the case with studies of climate–fire interactions, which only recognize an effect of humans on the fire regime when they act independently of climate. In this paper, we test the hypothesis that an anthropogenic fire regime (fire incidence, size and extent) does not covary with climate. In the lightning regime, positive El Niño southern oscillation (ENSO) values increase lightning fire incidence, whereas La Niña (and associated increases in prior rainfall) increase fire size. ENSO has the opposite effect in the Martu regime, decreasing ignitions in El Niño conditions without affecting fire size. Anthropogenic ignition rates covary positively with high antecedent rainfall, whereas fire size varies only with high temperatures and unpredictable winds, which may reduce control over fire spread. However, total area burned is similarly predicted by antecedent rainfall in both regimes, but is driven by increases in fire size in the lightning regime, and fire number in the anthropogenic regime. We conclude that anthropogenic regimes covary with climatic variation, but detecting the human–climate–fire interaction requires multiple measures of both fire regime and climate. This article is part of the themed issue ‘The interaction of fire and mankind’. PMID:27216513

Distant Influence of Kuroshio Eddies on North Pacific Weather Patterns?

PubMed Central

Ma, Xiaohui; Chang, Ping; Saravanan, R.; Montuoro, Raffaele; Hsieh, Jen-Shan; Wu, Dexing; Lin, Xiaopei; Wu, Lixin; Jing, Zhao

2015-01-01

High-resolution satellite measurements of surface winds and sea-surface temperature (SST) reveal strong coupling between meso-scale ocean eddies and near-surface atmospheric flow over eddy-rich oceanic regions, such as the Kuroshio and Gulf Stream, highlighting the importance of meso-scale oceanic features in forcing the atmospheric planetary boundary layer (PBL). Here, we present high-resolution regional climate modeling results, supported by observational analyses, demonstrating that meso-scale SST variability, largely confined in the Kuroshio-Oyashio confluence region (KOCR), can further exert a significant distant influence on winter rainfall variability along the U.S. Northern Pacific coast. The presence of meso-scale SST anomalies enhances the diabatic conversion of latent heat energy to transient eddy energy, intensifying winter cyclogenesis via moist baroclinic instability, which in turn leads to an equivalent barotropic downstream anticyclone anomaly with reduced rainfall. The finding points to the potential of improving forecasts of extratropical winter cyclones and storm systems and projections of their response to future climate change, which are known to have major social and economic impacts, by improving the representation of ocean eddy–atmosphere interaction in forecast and climate models. PMID:26635077

Effect of water availability in opening containers of breeding site on Aedes aegypti life cycle

NASA Astrophysics Data System (ADS)

Tokachil, Najir; Yusoff, Nuraini; Saaid, Alif; Appandi, Najwa; Harun, Farhana

2017-11-01

The distribution of rainfall is one of the factors which contribute to the development of Aedes aegypti life cycle. The fluctuation of rainfall might influence the acceleration of Aedes aegypti growth by providing sufficient breeding sites. In this research, the availability of water in an opening container of the breeding site is considered as a significant variable which affects the distinct stages structure in mosquito life cycle which egg, larva, pupa, and adult. A stage-structured Lefkovitch matrix model was used by considering the quantity of water contains in an opening container and life cycle of Aedes aegypti. The maximum depth of water in the container was also taken into account in order to find the time duration of mosquito life cycle to complete. We found that the maximum depth of water availability in mosquito breeding site influenced the abundance of the mosquito population. Hence, the containers are filled with sufficient water be able to stand from hot temperature for several days before drying out might continue to provide mosquito breeding site. In the future, it is recommended to consider other factors which affect the quantity of water in mosquito breeding sites such as heavy rain and wind blows.

Evolution of Mesoscale Convective System over the South Western Peninsular India: Observations from Microwave Radiometer and Simulations using WRF

NASA Astrophysics Data System (ADS)

Uma, K. N.; Krishna Moorthy, K.; Sijikumar, S.; Renju, R.; Tinu, K. A.; Raju, Suresh C.

2012-07-01

Meso-scale Convective Systems (MCS) are important in view of their large cumulous build-up, vertical extent, short horizontal extent and associated thundershowers. The Microwave Radiometer Profiler (MRP) over the equatorial coastal station Thiruvanathapuram (Trivandrum, 8.55oN, 76.9oE), has been utilized to understand the genesis of Mesoscale convective system (MCS), that occur frequently during the pre-monsoon season. Examination of the measurement of relative humidity, temperature and cloud liquid water measurements, over the zenith and two scanning elevation angles (15o) viewing both over the land and the sea respectively revealed that the MCS generally originate over the land during early afternoon hours, propagate seawards over the observational site and finally dissipate over the sea, with accompanying rainfall and latent heat release. The simulations obtained using Advanced Research-Weather Research and Forecast (WRF-ARW) model effectively reproduces the thermodynamical and microphysical properties of the MCS. The time duration and quantity of rainfall obtained by the simulations also well compared with the observations. Analysis also suggests that wind shear in the upper troposphere is responsible for the growth and the shape of the convective cloud.

Coupled ocean-atmosphere models feature systematic delay in Indian monsoon onset compared to their atmosphere-only component

NASA Astrophysics Data System (ADS)

Turner, Andrew

2014-05-01

In this study we examine monsoon onset characteristics in 20th century historical and AMIP integrations of the CMIP5 multi-model database. We use a period of 1979-2005, common to both the AMIP and historical integrations. While all available observed boundary conditions, including sea-surface temperature (SST), are prescribed in the AMIP integrations, the historical integrations feature ocean-atmosphere models that generate SSTs via air-sea coupled processes. The onset of Indian monsoon rainfall is shown to be systematically earlier in the AMIP integrations when comparing groups of models that provide both experiments, and in the multi-model ensemble means for each experiment in turn. We also test some common circulation indices of the monsoon onset including the horizontal shear in the lower troposphere and wind kinetic energy. Since AMIP integrations are forced by observed SSTs and CMIP5 models are known to have large cold SST biases in the northern Arabian Sea during winter and spring that limits their monsoon rainfall, we relate the delayed onset in the coupled historical integrations to cold Arabian Sea SST biases. This study provides further motivation for solving cold SST biases in the Arabian Sea in coupled models.

Local sea surface temperatures add to extreme precipitation in northeast Australia during La Niña

NASA Astrophysics Data System (ADS)

Evans, Jason P.; Boyer-Souchet, Irène

2012-05-01

This study examines the role played by high sea surface temperatures around northern Australia, in producing the extreme precipitation which occurred during the strong La Niña in December 2010. These extreme rains produced floods that impacted almost 1,300,000 km2, caused billions of dollars in damage, led to the evacuation of thousands of people and resulted in 35 deaths. Through the use of regional climate model simulations the contribution of the observed high sea surface temperatures to the rainfall is quantified. Results indicate that the large-scale atmospheric circulation changes associated with the La Niña event, while associated with above average rainfall in northeast Australia, were insufficient to produce the extreme rainfall and subsequent flooding observed. The presence of high sea surface temperatures around northern Australia added ˜25% of the rainfall total.

Evaporation suppression from reservoirs using floating covers: Lab scale wind-tunnel observations and mechanistic model predictions

NASA Astrophysics Data System (ADS)

Or, Dani; Lehmann, Peter; Aminzadeh, Milad; Sommer, Martina; Wey, Hannah; Krentscher, Christiane; Wunderli, Hans; Breitenstein, Daniel

2017-04-01

The competition over dwindling fresh water resources is expected to intensify with projected increase in human population in arid regions, expansion of irrigated land and changes in climate and drought patterns. The volume of water stored in reservoirs would also increase to mitigate seasonal shortages due to rainfall variability and to meet irrigation water needs. By some estimates up to half of the stored water is lost to evaporation, thereby exacerbating the water scarcity problem. Recently, there is an upsurge in the use of self-assembling floating covers to suppress evaporation, yet the design and implementation remain largely empirical. We report a systematic experimental evaluation of different cover types and external drivers (radiation, wind, wind plus radiation) on evaporation suppression and energy balance of a 1.4 m2 basin placed in a wind-tunnel. Surprisingly, evaporation suppression by black and white floating covers (balls and plates) were similar despite significantly different energy balance regimes over the cover surfaces. Moreover, the evaporation suppression efficiency was a simple function of the uncovered area (square root of the uncovered fraction) with linear relations with the covered area in some cases. The thermally decoupled floating covers offer an efficient solution to the evaporation suppression with limited influence of the surface energy balance (water temperature for black and white covers was similar and remained nearly constant). The results will be linked with a predictive evaporation-energy balance model and issues of spatial scales and long exposure times will be studied.

A 100 000-year record of annual and seasonal rainfall and temperature for northwestern Australia based on a pollen record obtained offshore

NASA Astrophysics Data System (ADS)

van der Kaars, Sander; de Deckker, Patrick; Gingele, Franz X.

2006-12-01

Pollen recovered from core tops of deep-sea cores from offshore northwestern Western Australia were used to build climatic transfer functions applied to sediment samples from major rivers bordering the ocean in the same region and a deep-sea core offshore Northwest Cape. Results show for the last 100 000 years, with a gap in the record spanning the 64 000 to 46 000 years interval, that from about 100 000 to 82 000 yr BP, climatic conditions represented by rainfall, temperature and number of humid months, were significantly higher than today's values. For the entire record, the coldest period occurred about 43 000 to 39 000 yr BP but it was wetter than today, whereas the Last Glacial Maximum saw a significant reduction in summer rainfall, interpreted as a result of the absence of monsoonal activity in the region. The Holocene can be divided into two distinct phases: one peaking around 6000 cal. yr BP with highest rainfall and summer temperatures; the second one commencing at 5000 cal. yr BP and showing a progressive decrease in summer rainfall in contrast to an increase in winter rainfall, paralleled by a progressive decrease in temperatures. Copyright

Utilising monitoring and modelling of estuarine environments to investigate catchment conditions responsible for stratification events in a typically well-mixed urbanised estuary

NASA Astrophysics Data System (ADS)

Lee, Serena B.; Birch, Gavin F.

2012-10-01

Estuarine health is affected by contamination from stormwater, particularly in highly-urbanised environments. For systems where catchment monitoring is insufficient, novel techniques must be employed to determine the impact of urban runoff on receiving water bodies. In the present work, estuarine monitoring and modelling were successfully employed to determine stormwater runoff volumes and establish an appropriate rainfall/runoff relationship capable of replicating fresh-water discharge due to the full range of precipitation conditions in the Sydney Estuary, Australia. Using estuary response to determine relationships between catchment rainfall and runoff is a widely applicable method and may be of assistance in the study of waterways where monitoring fluvial discharges is not practical or is beyond the capacity of management authorities. For the Sydney Estuary, the SCS-CN method replicated rainfall/runoff and was applied in numerical modelling experiments investigating the hydrodynamic characteristics affecting stratification and estuary recovery following high precipitation. Numerical modelling showed stratification in the Sydney Estuary was dominated by fresh-water discharge. Spring tides and up-estuary winds contributed to mixing and neap tides and down-estuary winds enhanced stratification.

Various Numerical Applications on Tropical Convective Systems Using a Cloud Resolving Model

NASA Technical Reports Server (NTRS)

Shie, C.-L.; Tao, W.-K.; Simpson, J.

2003-01-01

In recent years, increasing attention has been given to cloud resolving models (CRMs or cloud ensemble models-CEMs) for their ability to simulate the radiative-convective system, which plays a significant role in determining the regional heat and moisture budgets in the Tropics. The growing popularity of CRM usage can be credited to its inclusion of crucial and physically relatively realistic features such as explicit cloud-scale dynamics, sophisticated microphysical processes, and explicit cloud-radiation interaction. On the other hand, impacts of the environmental conditions (for example, the large-scale wind fields, heat and moisture advections as well as sea surface temperature) on the convective system can also be plausibly investigated using the CRMs with imposed explicit forcing. In this paper, by basically using a Goddard Cumulus Ensemble (GCE) model, three different studies on tropical convective systems are briefly presented. Each of these studies serves a different goal as well as uses a different approach. In the first study, which uses more of an idealized approach, the respective impacts of the large-scale horizontal wind shear and surface fluxes on the modeled tropical quasi-equilibrium states of temperature and water vapor are examined. In this 2-D study, the imposed large-scale horizontal wind shear is ideally either nudged (wind shear maintained strong) or mixed (wind shear weakened), while the minimum surface wind speed used for computing surface fluxes varies among various numerical experiments. For the second study, a handful of real tropical episodes (TRMM Kwajalein Experiment - KWAJEX, 1999; TRMM South China Sea Monsoon Experiment - SCSMEX, 1998) have been simulated such that several major atmospheric characteristics such as the rainfall amount and its associated stratiform contribution, the Qlheat and Q2/moisture budgets are investigated. In this study, the observed large-scale heat and moisture advections are continuously applied to the 2-D model. The modeled cloud generated from such an approach is termed continuously forced convection or continuous large-scale forced convection. A third study, which focuses on the respective impact of atmospheric components on upper Ocean heat and salt budgets, will be presented in the end. Unlike the two previous 2-D studies, this study employs the 3-D GCE-simulated diabatic source terms (using TOGA COARE observations) - radiation (longwave and shortwave), surface fluxes (sensible and latent heat, and wind stress), and precipitation as input for the Ocean mixed-layer (OML) model.

Biogeographical variation of plumage coloration in the sexually dichromatic Hawai‘i ‘Amakihi (Chlorodrepanis virens)

USGS Publications Warehouse

Gaudioso-Levita, Jacqueline M.; Hart, Patrick J.; Lapointe, Dennis; Veillet, Anne; Sebastian-Gonzalez, Esther

2017-01-01

Plumage coloration in birds can be of major importance to mate selection, social signaling, or predator avoidance. Variations in plumage coloration related to sex, age class, or seasons have been widely studied, but the effect of other factors such as climate is less known. In this study, we examine how carotenoid-based plumage coloration and sexual dichromatism of the Hawai‘i ‘Amakihi (Chlorodrepanis virens) varies with rainfall and temperature on Hawai‘i Island. We also examined whether Hawai‘i ‘Amakihi plumage coloration patterns follow Gloger’s rule, which states that animals in wetter climates have darker coloration. Hawai‘i ‘Amakihi were mist-netted and banded at 12 sites representing six major climatic zones on Hawai‘i Island. Feather samples were collected from two body regions: the breast and rump. Using spectrophotometry, we recorded coloration using measures of hue, saturation, and brightness. We conducted sex determination by polymerase chain reaction to confirm the sex of birds sampled. We found that the plumage coloration of Hawai‘i ‘Amakihi varied with both temperature and rainfall. ‘Amakihi plumage’s brightness showed a quadratic relationship with rainfall, contrary to Gloger’s rule, and decreased with temperature. Saturation depended on the interaction between temperature and rainfall. Increases in rainfall also increased saturation in warm areas, while they reduced saturation when the temperature was low. Finally, we found chromatic differences among sexes, but sexual dichromatism was not affected by the climatic conditions. This study provides evidence that rainfall and temperature play an important role in determining the plumage traits of Hawai‘i ‘Amakihi.

Eddy covariance and lysimeter measurements of moisture fluxes over supraglacial debris

NASA Astrophysics Data System (ADS)

Brock, Benjamin

2015-04-01

Supraglacial debris covers have the potential to evaporate large quantities of water derived from either sub-debris ice melt or precipitation. Currently, knowledge of evaporation and condensation rates in supraglacial debris is limited due to the difficulty of making direct measurements. This paper presents eddy covariance and lysimeter measurements of moisture fluxes made over a 0.2 m debris layer at Miage debris covered glacier, Italian Alps, during the 2013 ablation season. The meteorological data are complimented by reflectometer measurements of volumetric water fraction in the saturated and vadose zones of the debris layer. The lysimeters were designed specifically to mimic the debris cover and were embedded within the debris matrix, level with the surface. Over the ablation season, the latent heat flux is dominated by evaporation, and the flux magnitude closely follows the daily cycle of daytime solar heating and night time radiative cooling of debris. Mean flux values are of the order of 1 kg m-2 day-1, but often higher for short periods following rainfall. Condensation rates are relatively small and restricted to night time and humid conditions when the debris-atmosphere vapour pressure gradient reverses due to relatively warm air overlying cold debris. The reflectometer measurements provide evidence of vertical water movement through capillary rise in the upper part of the fine-grained debris layer, just above the saturated horizon, and demonstrate how debris bulk water content increases after rainfall. The latent heat flux responds directly to changes in wind speed, indicating that atmospheric turbulence can penetrate porous upper debris layers to the saturated horizon. Hence, vertical sorting of debris sediments and antecedent rainfall are important in determining evaporation rates, in addition to current meteorological conditions. Comparison of lysimeter measurements with rainfall data provides an estimate that between 45% and 89% of rainfall is evaporated directly back to the atmosphere. Rainfall evaporation rates increase with debris impermeability and temperature, with highest rates occurring when a shower falls on hot debris. If these point measurements are representative of larger scales, evaporation rates of the order of 1000 tonnes km-2 day-1 are implied, with higher rates following rainfall. This has important implications for downstream runoff, sub-debris ice melt rates (due to consumption of evaporative latent heat energy) and, possibly, convective atmospheric processes.

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.

Hurricane Isaac: A Longitudinal Analysis of Storm Characteristics and Power Outage Risk.

PubMed

Tonn, Gina L; Guikema, Seth D; Ferreira, Celso M; Quiring, Steven M

2016-10-01

In August 2012, Hurricane Isaac, a Category 1 hurricane at landfall, caused extensive power outages in Louisiana. The storm brought high winds, storm surge, and flooding to Louisiana, and power outages were widespread and prolonged. Hourly power outage data for the state of Louisiana were collected during the storm and analyzed. This analysis included correlation of hourly power outage figures by zip code with storm conditions including wind, rainfall, and storm surge using a nonparametric ensemble data mining approach. Results were analyzed to understand how correlation of power outages with storm conditions differed geographically within the state. This analysis provided insight on how rainfall and storm surge, along with wind, contribute to power outages in hurricanes. By conducting a longitudinal study of outages at the zip code level, we were able to gain insight into the causal drivers of power outages during hurricanes. Our analysis showed that the statistical importance of storm characteristic covariates to power outages varies geographically. For Hurricane Isaac, wind speed, precipitation, and previous outages generally had high importance, whereas storm surge had lower importance, even in zip codes that experienced significant surge. The results of this analysis can inform the development of power outage forecasting models, which often focus strictly on wind-related covariates. Our study of Hurricane Isaac indicates that inclusion of other covariates, particularly precipitation, may improve model accuracy and robustness across a range of storm conditions and geography. © 2016 Society for Risk Analysis.

Two simple models for accounting mussel contamination with diarrhoetic shellfish poisoning toxins at Aveiro lagoon: Control by rainfall and atmospheric forcing

NASA Astrophysics Data System (ADS)

Vale, Paulo

2012-02-01

At Aveiro lagoon (Portuguese northwest coast) bivalve contamination with diarrhoetic shellfish poisoning toxins (DSTs), okadaic acid (OA) and dinophysistoxin-2 (DTX2), is a recurrent annual phenomenon seriously affecting seafood safety. The influence of meteorological parameters was studied to understand accumulation of DSTs in mussels, related to the blooming of the causative toxic microalgae, belonging to genus Dinophysis. Two simplified models were useful in predicting the accumulation of DSTs in blue mussels from this lagoon. Either the May river drainage or the rainfall accumulated from January through May could adequately predict the severity of OA accumulated from predation upon Dinophysis acuminata during June/July. In both cases a linear relationship was obtained, with correlation coefficients of 0.85 or greater. Winds with a west direction favour coastal concentration of Dinophysis acuta in Aveiro region. Both OA and DTX2 contamination increased exponentially in September/October with the cumulative number of days with W-wind orientation in the preceding August (correlation coefficients greater than 0.92). This relationship was attributed to the quadratic effect of wind stress on surface currents. August is a transitional month, when the continental runoff effect upon Dinophysis acuminata can still be observed and Dinophysis acuta advection may be promoted by westerly winds occurring in July. The frequency of periods with northerly winds in July can halt accumulation of toxins derived from Dinophysis acuta.

The impact of different background errors in the assimilation of satellite radiances and in-situ observational data using WRFDA for three rainfall events over Iran

NASA Astrophysics Data System (ADS)

Zakeri, Zeinab; Azadi, Majid; Ghader, Sarmad

2018-01-01

Satellite radiances and in-situ observations are assimilated through Weather Research and Forecasting Data Assimilation (WRFDA) system into Advanced Research WRF (ARW) model over Iran and its neighboring area. Domain specific background error based on x and y components of wind speed (UV) control variables is calculated for WRFDA system and some sensitivity experiments are carried out to compare the impact of global background error and the domain specific background errors, both on the precipitation and 2-m temperature forecasts over Iran. Three precipitation events that occurred over the country during January, September and October 2014 are simulated in three different experiments and the results for precipitation and 2-m temperature are verified against the verifying surface observations. Results show that using domain specific background error improves 2-m temperature and 24-h accumulated precipitation forecasts consistently, while global background error may even degrade the forecasts compared to the experiments without data assimilation. The improvement in 2-m temperature is more evident during the first forecast hours and decreases significantly as the forecast length increases.

Composite Analysis of Cold Season Atmospheric River Events: Extreme Precipitation and Flooding over the Western United States

NASA Astrophysics Data System (ADS)

Eldardiry, H.; Hossain, F.

2017-12-01

Atmospheric Rivers (ARs) are narrow elongated corridors with horizontal water vapor transport located within the warm sector of extratropical cyclones. While it is widely known that most of heavy rainfall events across the western United States (US) are driven by ARs, the connection between atmospheric conditions and precipitation during an AR event has not been fully documented. In this study, we present a statistical analysis of the connection between precipitation, temperature, wind, and snowpack during the cold season AR events hitting the coastal regions of the western US. For each AR event, the precipitation and other atmospheric variables are retrieved through the dynamic downscaling of NCEP/NCAR Reanalysis product using the Advanced Research Weather Research and Forecasting Model (ARW-WRF). The results show a low frequency of precipitation (below 0.3) during AR events that reflects the connection of AR with extreme precipitation. Examining the horizontal wind speed during AR events indicates a high correlation (above 0.7) with precipitation. In addition, high levels of snow water equivalence (SWE) are also noticed along the mountainous regions, e.g., Cascade Range and Sierra-Nevada mountain range, during most of AR events. Addressing the impact of duration on the frequency of precipitation, we develop Intensity-Duration-Frequency (IDF) curves during AR events that can potentially describe the future predictability of precipitation along the north and south coast. To complement our analysis, we further investigate the flooding events recorded in the National Centers for Environmental Information (NCEI) storm events database. While some flooding events are attributed to heavy rainfall associated with an AR event, other flooding events are significantly connected to the increase in the snowmelt before the flooding date. Thus, we introduce an index that describes the contribution of rainfall vs snowmelt and categorizes the flooding events during an AR event into rain-driven and snow-driven events. Such categorization can provide insight into whether or not an AR will produce extreme precipitation or flooding. The results from such investigations are important to understand historical AR events and assess how precipitation and flooding might evolve in future climate.

Regulations of irrigation on regional climate in the Heihe watershed, China, and its implications to water budget

NASA Astrophysics Data System (ADS)

Zhang, X.

2015-12-01

In the arid area, such as the Heihe watershed in Northwest China, agriculture is heavily dependent on the irrigation. Irrigation suggests human-induced hydro process, which modifies the local climate and water budget. In this study, we simulated the irrigation-induced changes in surface energy/moisture budgets and modifications on regional climate, using the WRF-NoahMP modle with an irrigation scheme. The irrigation scheme was implemented following the roles that soil moisture is assigned a saturated value once the mean soil moisture of all root layers is lower than 70% of fileld capacity. Across the growth season refering from May to September, the simulated mean irrigation amount of the 1181 cropland gridcells is ~900 mm, wihch is close to the field measurments of around 1000 mm. Such an irrigation largely modified the surface energy budget. Due to irrigation, the surface net solar radiation increased by ~76.7 MJ (~11 Wm-2) accouting for ~2.3%, surface latent and senbile heat flux increased by 97.7 Wm-2 and decreased by ~79.7 Wm-2 respectively; and local daily mean surface air temperature was thereby cooling by ~1.1°C. Corresponding to the surface energy changes, wind and circulation were also modified and regional water budget is therefore regulated. The total rainfall in the irrigation area increased due to more moisture from surface. However, the increased rainfall is only ~6.5mm (accounting for ~5% of background rainfall) which is much less than the increased evaporation of ~521.5mm from surface. The ~515mm of water accounting for 57% of total irrigation was transported outward by wind. The other ~385 mm accounting for 43% of total irrigation was transformed to be runoff and soil water. These results suggest that in the Heihe watershed irrigation largely modify local energy budget and cooling surface. This study also implicate that the existing irrigation may waste a large number of water. It is thereby valuable to develope effective irrigation scheme to save water resources.

Climatic controls on the global distribution, abundance, and species richness of mangrove forests

USGS Publications Warehouse

Osland, Michael J.; Feher, Laura C.; Griffith, Kereen; Cavanaugh, Kyle C.; Enwright, Nicholas M.; Day, Richard H.; Stagg, Camille L.; Krauss, Ken W.; Howard, Rebecca J.; Grace, James B.; Rogers, Kerrylee

2017-01-01

Mangrove forests are highly productive tidal saline wetland ecosystems found along sheltered tropical and subtropical coasts. Ecologists have long assumed that climatic drivers (i.e., temperature and rainfall regimes) govern the global distribution, structure, and function of mangrove forests. However, data constraints have hindered the quantification of direct climate-mangrove linkages in many parts of the world. Recently, the quality and availability of global-scale climate and mangrove data have been improving. Here, we used these data to better understand the influence of air temperature and rainfall regimes upon the distribution, abundance, and species richness of mangrove forests. Although our analyses identify global-scale relationships and thresholds, we show that the influence of climatic drivers is best characterized via regional range limit-specific analyses. We quantified climatic controls across targeted gradients in temperature and/or rainfall within 14 mangrove distributional range limits. Climatic thresholds for mangrove presence, abundance, and species richness differed among the 14 studied range limits. We identified minimum temperature-based thresholds for range limits in eastern North America, eastern Australia, New Zealand, eastern Asia, eastern South America, and southeast Africa. We identified rainfall-based thresholds for range limits in western North America, western Gulf of Mexico, western South America, western Australia, Middle East, northwest Africa, east central Africa, and west central Africa. Our results show that in certain range limits (e.g., eastern North America, western Gulf of Mexico, eastern Asia), winter air temperature extremes play an especially important role. We conclude that rainfall and temperature regimes are both important in western North America, western Gulf of Mexico, and western Australia. With climate change, alterations in temperature and rainfall regimes will affect the global distribution, abundance, and diversity of mangrove forests. In general, warmer winter temperatures are expected to allow mangroves to expand poleward at the expense of salt marshes. However, dispersal and habitat availability constraints may hinder expansion near certain range limits. Along arid and semi-arid coasts, decreases or increases in rainfall are expected to lead to mangrove contraction or expansion, respectively. Collectively, our analyses quantify climate-mangrove linkages and improve our understanding of the expected global- and regional-scale effects of climate change upon mangrove forests.

Climatic change on the Gulf of Fonseca (Central America) using two-step statistical downscaling of CMIP5 model outputs

NASA Astrophysics Data System (ADS)

Ribalaygua, Jaime; Gaitán, Emma; Pórtoles, Javier; Monjo, Robert

2018-05-01

A two-step statistical downscaling method has been reviewed and adapted to simulate twenty-first-century climate projections for the Gulf of Fonseca (Central America, Pacific Coast) using Coupled Model Intercomparison Project (CMIP5) climate models. The downscaling methodology is adjusted after looking for good predictor fields for this area (where the geostrophic approximation fails and the real wind fields are the most applicable). The method's performance for daily precipitation and maximum and minimum temperature is analysed and revealed suitable results for all variables. For instance, the method is able to simulate the characteristic cycle of the wet season for this area, which includes a mid-summer drought between two peaks. Future projections show a gradual temperature increase throughout the twenty-first century and a change in the features of the wet season (the first peak and mid-summer rainfall being reduced relative to the second peak, earlier onset of the wet season and a broader second peak).

Global warming-induced upper-ocean freshening and the intensification of super typhoons

PubMed Central

Balaguru, Karthik; Foltz, Gregory R.; Leung, L. Ruby; Emanuel, Kerry A.

2016-01-01

Super typhoons (STYs), intense tropical cyclones of the western North Pacific, rank among the most destructive natural hazards globally. The violent winds of these storms induce deep mixing of the upper ocean, resulting in strong sea surface cooling and making STYs highly sensitive to ocean density stratification. Although a few studies examined the potential impacts of changes in ocean thermal structure on future tropical cyclones, they did not take into account changes in near-surface salinity. Here, using a combination of observations and coupled climate model simulations, we show that freshening of the upper ocean, caused by greater rainfall in places where typhoons form, tends to intensify STYs by reducing their ability to cool the upper ocean. We further demonstrate that the strengthening effect of this freshening over the period 1961–2008 is ∼53% stronger than the suppressive effect of temperature, whereas under twenty-first century projections, the positive effect of salinity is about half of the negative effect of ocean temperature changes. PMID:27886199

Global warming-induced upper-ocean freshening and the intensification of super typhoons

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

Balaguru, Karthik; Foltz, Gregory R.; Leung, L. Ruby

Here, super typhoons (STYs), intense tropical cyclones of the western North Pacific, rank among the most destructive natural hazards globally. The violent winds of these storms induce deep mixing of the upper ocean, resulting in strong sea surface cooling and making STYs highly sensitive to ocean density stratification. Although a few studies examined the potential impacts of changes in ocean thermal structure on future tropical cyclones, they did not take into account changes in near-surface salinity. Here, using a combination of observations and coupled climate model simulations, we show that freshening of the upper ocean, caused by greater rainfall inmore » places where typhoons form, tends to intensify STYs by reducing their ability to cool the upper ocean. We further demonstrate that the strengthening effect of this freshening over the period 1961–2008 is ~53% stronger than the suppressive effect of temperature, whereas under twenty-first century projections, the positive effect of salinity is about half of the negative effect of ocean temperature changes.« less

Surface and atmosphere parameter maps from earth-orbiting radiometers

NASA Technical Reports Server (NTRS)

Gloersen, P.

1976-01-01

Earlier studies have shown that an earth-orbiting electrically scanned microwave radiometer (ESMR) is capable of inferring the extent, concentration, and age of sea ice; the extent, concentration, and thickness of lake ice; rainfall rates over oceans; surface wind speeds over open water; particle size distribution in the deep snow cover of continental ice sheets; and soil moisture content in unvegetated fields. Most other features of the surface of the earth and its atmosphere require multispectral imaging techniques to unscramble the combined contributions of the atmosphere and the surface. Multispectral extraction of surface parameters is analyzed on the basis of a pertinent equation in terms of the observed brightness temperature, the emissivity of the surface which depends on wavelength and various parameters, the sensible temperature of the surface, and the total atmospheric opacity which is also wavelength dependent. Implementation of the multispectral technique is examined. Properties of the surface of the earth and its atmosphere to be determined from a scanning multichannel microwave radiometer are tabulated.

Global warming-induced upper-ocean freshening and the intensification of super typhoons.

PubMed

Balaguru, Karthik; Foltz, Gregory R; Leung, L Ruby; Emanuel, Kerry A

2016-11-25

Super typhoons (STYs), intense tropical cyclones of the western North Pacific, rank among the most destructive natural hazards globally. The violent winds of these storms induce deep mixing of the upper ocean, resulting in strong sea surface cooling and making STYs highly sensitive to ocean density stratification. Although a few studies examined the potential impacts of changes in ocean thermal structure on future tropical cyclones, they did not take into account changes in near-surface salinity. Here, using a combination of observations and coupled climate model simulations, we show that freshening of the upper ocean, caused by greater rainfall in places where typhoons form, tends to intensify STYs by reducing their ability to cool the upper ocean. We further demonstrate that the strengthening effect of this freshening over the period 1961-2008 is ∼53% stronger than the suppressive effect of temperature, whereas under twenty-first century projections, the positive effect of salinity is about half of the negative effect of ocean temperature changes.

Global warming-induced upper-ocean freshening and the intensification of super typhoons

DOE PAGES

Balaguru, Karthik; Foltz, Gregory R.; Leung, L. Ruby; ...

2016-11-25

Here, super typhoons (STYs), intense tropical cyclones of the western North Pacific, rank among the most destructive natural hazards globally. The violent winds of these storms induce deep mixing of the upper ocean, resulting in strong sea surface cooling and making STYs highly sensitive to ocean density stratification. Although a few studies examined the potential impacts of changes in ocean thermal structure on future tropical cyclones, they did not take into account changes in near-surface salinity. Here, using a combination of observations and coupled climate model simulations, we show that freshening of the upper ocean, caused by greater rainfall inmore » places where typhoons form, tends to intensify STYs by reducing their ability to cool the upper ocean. We further demonstrate that the strengthening effect of this freshening over the period 1961–2008 is ~53% stronger than the suppressive effect of temperature, whereas under twenty-first century projections, the positive effect of salinity is about half of the negative effect of ocean temperature changes.« less

The asymmetric response of Yangtze river basin summer rainfall to El Niño/La Niña

NASA Astrophysics Data System (ADS)

Hardiman, Steven C.; Dunstone, Nick J.; Scaife, Adam A.; Bett, Philip E.; Li, Chaofan; Lu, Bo; Ren, Hong-Li; Smith, Doug M.; Stephan, Claudia C.

2018-02-01

The Yangtze river basin, in South East China, experiences anomalously high precipitation in summers following El Niño. This can lead to extensive flooding and loss of life. However, the response following La Niña has not been well documented. In this study, the response of Yangtze summer rainfall to El Niño/La Niña is found to be asymmetric, with no significant response following La Niña. The nature of this asymmetric response is found to be in good agreement with that simulated by the Met Office seasonal forecast system. Yangtze summer rainfall correlates positively with spring sea surface temperatures in the Indian Ocean and northwest Pacific. Indian Ocean sea surface temperatures are found to respond linearly to El Niño/La Niña, and to have a linear impact on Yangtze summer rainfall. However, northwest Pacific sea surface temperatures respond much more strongly following El Niño and, further, correlate more strongly with positive rainfall years. It is concluded that, whilst delayed Indian Ocean signals may influence summer Yangtze rainfall, it is likely that they do not lead to the asymmetric nature of the rainfall response to El Niño/La Niña.

Recent trends in rainfall and temperature over North West India during 1871-2016

NASA Astrophysics Data System (ADS)

Saxena, Rani; Mathur, Prasoon

2018-03-01

Rainfall and temperature are the most important environmental factors influencing crop growth, development, and yield. The northwestern (NW) part of India is one of the main regions of food grain production of the country. It comprises of six meteorological subdivisions (Haryana, Punjab, West Rajasthan, East Rajasthan, Gujarat and Saurashtra, Kutch and Diu). In this study, attempts were made to study variability and trends in rainfall and temperature during 30-year climate normal periods (CN) and 10-year decadal excess or deficit rainfall frequency during the historical period from 1871 to 2016. The Mann-Kendall and Spearman's rank correlation (Spearman's rho) tests were used to determine significance of trends. Least square linear fitting method was adopted to find out the slopes of the trend lines. The long-term mean annual rainfall over North West India is 587.7 mm (standard deviation of 153.0 mm and coefficient of variation 26.0). There was increasing trend in minimum and maximum temperatures during post monsoon season in entire study period and current climate normal period (1991-2016) due to which the sowing of rabi season crops may be delayed and there may be germination problem too. There was a non-significant decreasing trend in rainfall during monsoon season and an increasing trend in rainfall during post monsoon over North West India during entire study period. During current CN5 (1991-2016), all the subdivision (except the Saurashtra region) showed a decreasing trend in rainfall during monsoon season which is a matter of concern for kharif crops and those rabi crops which are grown as rainfed on conserved soil moisture. The decadal annual and seasonal frequencies of excess and deficit years results revealed that the annual total deficit rainfall years (24) exceeded total excess rainfall years (22) in North West India during the entire study period. While during the current decadal period (2011 to 2016), single year was the excess year and 2 years were deficit rainfall years in all subdivisions (except East Rajasthan) on annual basis.

Trends in rainfall and temperature extremes in Morocco

NASA Astrophysics Data System (ADS)

Khomsi, K.; Mahe, G.; Tramblay, Y.; Sinan, M.; Snoussi, M.

2015-02-01

In Morocco, socioeconomic fields are vulnerable to weather extreme events. This work aims to analyze the frequency and the trends of temperature and rainfall extreme events in two contrasted Moroccan regions (the Tensift in the semi-arid South, and the Bouregreg in the sub-humid North), during the second half of the 20th century. This study considers long time series of daily extreme temperatures and rainfall, recorded in the stations of Marrakech and Safi for the Tensift region, and Kasba-Tadla and Rabat-Sale for the Bouregreg region, data from four other stations (Tanger, Fes, Agadir and Ouarzazate) from outside the regions were added. Extremes are defined by using as thresholds the 1st, 5th, 90th, 95th, and 99th percentiles. Results show upward trends in maximum and minimum temperatures of both regions and no generalized trends in rainfall amounts. Changes in cold events are larger than those for warm events, and the number of very cold events decrease significantly in the whole studied area. The southern region is the most affected with the changes of the temperature regime. Most of the trends found in rainfall heavy events are positive with weak magnitudes even though no statistically significant generalized trends could be identified during both seasons.

Universal inverse power-law distribution for temperature and rainfall in the UK region

NASA Astrophysics Data System (ADS)

Selvam, A. M.

2014-06-01

Meteorological parameters, such as temperature, rainfall, pressure, etc., exhibit selfsimilar space-time fractal fluctuations generic to dynamical systems in nature such as fluid flows, spread of forest fires, earthquakes, etc. The power spectra of fractal fluctuations display inverse power-law form signifying long-range correlations. A general systems theory model predicts universal inverse power-law form incorporating the golden mean for the fractal fluctuations. The model predicted distribution was compared with observed distribution of fractal fluctuations of all size scales (small, large and extreme values) in the historic month-wise temperature (maximum and minimum) and total rainfall for the four stations Oxford, Armagh, Durham and Stornoway in the UK region, for data periods ranging from 92 years to 160 years. For each parameter, the two cumulative probability distributions, namely cmax and cmin starting from respectively maximum and minimum data value were used. The results of the study show that (i) temperature distributions (maximum and minimum) follow model predicted distribution except for Stornowy, minimum temperature cmin. (ii) Rainfall distribution for cmin follow model predicted distribution for all the four stations. (iii) Rainfall distribution for cmax follows model predicted distribution for the two stations Armagh and Stornoway. The present study suggests that fractal fluctuations result from the superimposition of eddy continuum fluctuations.

Leishmaniases in Greece

PubMed Central

Ntais, Pantelis; Sifaki-Pistola, Dimitra; Christodoulou, Vasiliki; Messaritakis, Ippokratis; Pratlong, Francine; Poupalos, George; Antoniou, Maria

2013-01-01

During the last 35 years, visceral leishmaniasis has spread in Greece with autochthonous human cases appearing in 41 of the 54 prefectures. The occurrence of the disease was mapped and related to dog seropositivity, environmental and geospatial risk factors. Average dog seropositivity was 22.1% and positive animals were found in 43 of 54 prefectures. Factors like: altitude, presence of water bodies, land use, wind speed, mean land surface temperature, mean relative humidity, and mean annual rainfall were found to affect dog seropositivity. Cases of cutaneous leishmaniasis, caused by Leishmania tropica are also increasing. Phlebotomus similis believed to be the potential vector of L. tropica in Greece, was found in areas where the disease is widespread but also where cases have never been reported implying a danger of introduction of this anthroponotic parasite to new regions. PMID:24062479

Coherent variability between seasonal temperatures and rainfalls in the Iberian Peninsula, 1951-2016

NASA Astrophysics Data System (ADS)

Rodrigo, F. S.

2018-02-01

In this work trends of seasonal mean of daily minimum (TN), maximum (TX), mean (TM) temperatures, daily range of temperature (DTR), and total seasonal rainfall (R) in 35 Iberian stations since mid-twentieth century are studied. The interest is focused on the relationships between temperature variables and rainfall, taking into account the correlation coefficients between R and the temperature variables. The negative link between rainfall and temperatures is detected in the four seasons of the year, except in western stations in winter for TN and TM, and in autumn for TN (for this variable a certain annual cycle is detected, with predominance of positive correlation in winter, negative in spring and summer, and the autumn as transition season). The role of cloud cover is confirmed in those stations with total cloud cover data. Using an average peninsular series, the relationship between nighttime temperature and rainfall related to long wave radiation is confirmed for the four seasons of the year, although in spring and summer has minor importance than in the cold half year. The relationships between R, TN, and TX are in general terms stable after a moving correlation analysis, although the negative correlation between TX and R seems be weakened in spring and autumn and reinforced in summer. The role of convective precipitation in autumn is discussed. The analysis of combined extreme indices in four representative stations shows an increase of warm and dry days, and a decrease of cold and wet days.

Assessment on spatiotemporal relationship between rainfall and cloud top temperature from new generation weather satellite imagery

NASA Astrophysics Data System (ADS)

Wei, Chiang; Yeh, Hui-Chung; Chen, Yen-Chang

2017-04-01

This study addressed the relationship between rainfall and cloud top temperature (CCT) from new generation satellite Himawari-8 imagery at different spatiotemporal scale. This satellite provides higher band, more bits for data format, spatial and temporal resolution compared with previous GMS series. The multi-infrared channels with 10-minute and 1-2 km resolution make it possible for rainfall estimating/forecasting in small/medium watershed. The preliminary result investigated at Chenyulan watershed (443.6 square kilometer) of Central Taiwan in 2016 Typhoon Megi shows the regression coefficient fitted by negative exponential equation of largest rainfall vs. CCT (B8 band) at pixel scale increases as time scales enlarges and reach 0.462 for 120-minute accumulative rainfall; the value (CTT of B15 band) decreases from 0.635 for 10-minute to 0.423 for 120-minute accumulative rainfall at basin-wide scale. More rainfall events for different regime are yet to evaluate to get solid results.

Public health risks of prolonged fine particle events associated with stagnation and air quality index based on fine particle matter with a diameter <2.5 μm in the Kaoping region of Taiwan

NASA Astrophysics Data System (ADS)

Lai, Li-Wei

2016-12-01

The increasing frequency of droughts in tropical and sub-tropical areas since 1970 due to climate change requires a better understanding of the relationship between public health and long-duration fine particle events (FPE; defined as a day with an average PM2.5 ≥ 35.5 μg/m3) associated with rainfall and wind speed. In the Kaoping region of Taiwan, 94.46 % of the daily average PM2.5 in winter exceeds the limit established by 2005 World Health Organization (WHO) guidelines. This study investigated the differences in winter weather characteristics and health effects between non-FPE and FPE days, and the performance of air quality indexes on FPE days. Z-statistics for one-tailed tests, multiplicative decomposition models, logarithmic regression, and product-moment correlations were used for the analysis. The results indicate that mean wind speeds, rainfall hours, and air temperature were significantly decreased on FPE days. Daily mean PM2.5 concentrations were positively correlated to the duration of FPE days. The duration of FPE days was positively related to the length of drought ( r = 0.97, P < 0.05). The number of respiratory admissions was positively correlated with the FPE duration ( r 2 = 0.60). The age groups >15 years experienced the largest average reduction in asthma admissions on lag-days. Compared to the pollutant standard index (PSI) and revised air quality index (RAQI), the PM2.5 index is more representative and sensitive to changes in PM2.5 concentrations.

CO2 leakage monitoring and analysis to understand the variation of CO2 concentration in vadose zone by natural effects

NASA Astrophysics Data System (ADS)

Joun, Won-Tak; Ha, Seung-Wook; Kim, Hyun Jung; Ju, YeoJin; Lee, Sung-Sun; Lee, Kang-Kun

2017-04-01

Controlled ex-situ experiments and continuous CO2 monitoring in the field are significant implications for detecting and monitoring potential leakage from CO2 sequestration reservoir. However, it is difficult to understand the observed parameters because the natural disturbance will fluctuate the signal of detections in given local system. To identify the original source leaking from sequestration reservoir and to distinguish the camouflaged signal of CO2 concentration, the artificial leakage test was conducted in shallow groundwater environment and long-term monitoring have been performed. The monitoring system included several parameters such as pH, temperature, groundwater level, CO2 gas concentration, wind speed and direction, atmospheric pressure, borehole pressure, and rainfall event etc. Especially in this study, focused on understanding a relationship among the CO2 concentration, wind speed, rainfall and pressure difference. The results represent that changes of CO2 concentration in vadose zone could be influenced by physical parameters and this reason is helpful in identifying the camouflaged signal of CO2 concentrations. The 1-D column laboratory experiment also was conducted to understand the sparking-peak as shown in observed data plot. The results showed a similar peak plot and could consider two assumptions why the sparking-peak was shown. First, the trapped CO2 gas was escaped when the water table was changed. Second, the pressure equivalence between CO2 gas and water was broken when the water table was changed. These field data analysis and laboratory experiment need to advance due to comprehensively quantify local long-term dynamics of the artificial CO2 leaking aquifer. Acknowledgement Financial support was provided by the "R&D Project on Environmental Management of Geologic CO2 Storage" from the KEITI (Project Number: 2014001810003)

Weather effects on the patterns of people's everyday activities: a study using GPS traces of mobile phone users.

PubMed

Horanont, Teerayut; Phithakkitnukoon, Santi; Leong, Tuck W; Sekimoto, Yoshihide; Shibasaki, Ryosuke

2013-01-01

This study explores the effects that the weather has on people's everyday activity patterns. Temperature, rainfall, and wind speed were used as weather parameters. People's daily activity patterns were inferred, such as place visited, the time this took place, the duration of the visit, based on the GPS location traces of their mobile phones overlaid upon Yellow Pages information. Our analysis of 31,855 mobile phone users allowed us to infer that people were more likely to stay longer at eateries or food outlets, and (to a lesser degree) at retail or shopping areas when the weather is very cold or when conditions are calm (non-windy). When compared to people's regular activity patterns, certain weather conditions affected people's movements and activities noticeably at different times of the day. On cold days, people's activities were found to be more diverse especially after 10AM, showing greatest variations between 2PM and 6PM. A similar trend is observed between 10AM and midnight on rainy days, with people's activities found to be most diverse on days with heaviest rainfalls or on days when the wind speed was stronger than 4 km/h, especially between 10AM-1AM. Finally, we observed that different geographical areas of a large metropolis were impacted differently by the weather. Using data of urban infrastructure to characterize areas, we found strong correlations between weather conditions upon people's accessibility to trains. This study sheds new light on the influence of weather conditions on human behavior, in particular the choice of daily activities and how mobile phone data can be used to investigate the influence of environmental factors on urban dynamics.

Weather Effects on the Patterns of People's Everyday Activities: A Study Using GPS Traces of Mobile Phone Users

PubMed Central

Leong, Tuck W.; Sekimoto, Yoshihide; Shibasaki, Ryosuke

2013-01-01

This study explores the effects that the weather has on people's everyday activity patterns. Temperature, rainfall, and wind speed were used as weather parameters. People's daily activity patterns were inferred, such as place visited, the time this took place, the duration of the visit, based on the GPS location traces of their mobile phones overlaid upon Yellow Pages information. Our analysis of 31,855 mobile phone users allowed us to infer that people were more likely to stay longer at eateries or food outlets, and (to a lesser degree) at retail or shopping areas when the weather is very cold or when conditions are calm (non-windy). When compared to people's regular activity patterns, certain weather conditions affected people's movements and activities noticeably at different times of the day. On cold days, people's activities were found to be more diverse especially after 10AM, showing greatest variations between 2PM and 6PM. A similar trend is observed between 10AM and midnight on rainy days, with people's activities found to be most diverse on days with heaviest rainfalls or on days when the wind speed was stronger than 4 km/h, especially between 10AM–1AM. Finally, we observed that different geographical areas of a large metropolis were impacted differently by the weather. Using data of urban infrastructure to characterize areas, we found strong correlations between weather conditions upon people's accessibility to trains. This study sheds new light on the influence of weather conditions on human behavior, in particular the choice of daily activities and how mobile phone data can be used to investigate the influence of environmental factors on urban dynamics. PMID:24367481

Meteorology drives ambient air quality in a valley: a case of Sukinda chromite mine, one among the ten most polluted areas in the world.

PubMed

Mishra, Soumya Ranjan; Pradhan, Rudra Pratap; Prusty, B Anjan Kumar; Sahu, Sanjat Kumar

2016-07-01

The ambient air quality (AAQ) assessment was undertaken in Sukinda Valley, the chromite hub of India. The possible correlations of meteorological variables with different air quality parameters (PM10, PM2.5, SO2, NO2 and CO) were examined. Being the fourth most polluted area in the globe, Sukinda Valley has always been under attention of researchers, for hexavalent chromium contamination of water. The monitoring was carried out from December 2013 through May 2014 at six strategic locations in the residential and commercial areas around the mining cluster of Sukinda Valley considering the guidelines of Central Pollution Control Board (CPCB). In addition, meteorological parameters viz., temperature, relative humidity, wind speed, wind direction and rainfall, were also monitored. The air quality data were subjected to a general linear model (GLM) coupled with one-way analysis of variance (ANOVA) test for testing the significant difference in the concentration of various parameters among seasons and stations. Further, a two-tailed Pearson's correlation test helped in understanding the influence of meteorological parameters on dispersion of pollutants in the area. All the monitored air quality parameters varied significantly among the monitoring stations suggesting (i) the distance of sampling location to the mine site and other allied activities, (ii) landscape features and topography and (iii) meteorological parameters to be the forcing functions. The area was highly polluted with particulate matters, and in most of the cases, the PM level exceeded the National Ambient Air Quality Standards (NAAQS). The meteorological parameters seemed to play a major role in the dispersion of pollutants around the mine clusters. The role of wind direction, wind speed and temperature was apparent in dispersion of the particulate matters from their source of generation to the surrounding residential and commercial areas of the mine.

Controlling factors of evaporation and CO2 flux over an open water lake in southeastern margin of Tibetan Plateau

NASA Astrophysics Data System (ADS)

Du, Q.; Liu, H.; Liu, Y.; Wang, L.; Xu, L.

2017-12-01

Erhai lake is located in the southeastern margin of Tibetan Plateau. Based on the 4 years measurement over Erhai lake with eddy covariance technique (EC) from 2012 to 2015, the diurnal and seasonal variations of latent and sensible heat and CO2 fluxes, and their controlling factors over different time scales were analyzed. The diurnal average LE ranged from 31 to 171 Wm-2, while Hs ranged from -31 to 21 Wm-2. Bowen ratio was larger during January and May and smaller during June and October. The lake continued storing heat during January and June, and releasing heat since July. The diurnal average CO2 fluxes during nighttime were higher than the daytime, and carbon uptake was almost observed during the midday time of the day for the whole study period. The annual carbon budget fluctuated from 117.5 to 161.7 g C m-2 a-1, while annual total evaporation (ET) from 1120.8 to 1228.5 mm for the four-years period. The Erhai Lake behaved as a net carbon source over the whole period but carbon uptake was observed during the middle time of each year. The difference between water surface and air temperature (DeltaT) and the product of DeltaT and wind speed were the main controlling factors for Hs from halfhourly to monthly scale. There was significant relationship between wind speed, the product of wind speed and vapor pressure deficit (VPD) and LE on halfhourly and daily scales. The total cloud amount and net radiation (Rn) had a large effect on monthly variation of LE. Photosynthetic active radiation (PAR) and wind speed was mainly responsible for the variation of halfhourly and daily CO2 fluxes, respectively. The total cloud amount was the most important factors controlling for annual total ET. The annual rainfall, water surface temperature was observed to be negatively related with annual CO2 fluxes.

The short-term association of temperature and rainfall with mortality in Vadu Health and Demographic Surveillance System: a population level time series analysis

PubMed Central

Ingole, Vijendra; Juvekar, Sanjay; Muralidharan, Veena; Sambhudas, Somnath; Rocklöv, Joacim

2012-01-01

Background Research in mainly developed countries has shown that some changes in weather are associated with increased mortality. However, due to the lack of accessible data, few studies have examined such effects of weather on mortality, particularly in rural regions in developing countries. Objective In this study, we aimed to investigate the relationship between temperature and rainfall with daily mortality in rural India. Design Daily mortality data were obtained from the Health and Demographic Surveillance System (HDSS) in Vadu, India. Daily mean temperature and rainfall data were obtained from a regional meteorological center, India Meteorological Department (IMD), Pune. A Poisson regression model was established over the study period (January 2003–May 2010) to assess the short-term relationship between weather variables and total mortality, adjusting for time trends and stratifying by both age and sex. Result Mortality was found to be significantly associated with daily ambient temperatures and rainfall, after controlling for seasonality and long-term time trends. Children aged 5 years or below appear particularly susceptible to the effects of warm and cold temperatures and heavy rainfall. The population aged 20–59 years appeared to face increased mortality on hot days. Most age groups were found to have increased mortality rates 7–13 days after rainfall events. This association was particularly evident in women. Conclusion We found the level of mortality in Vadu HDSS in rural India to be highly affected by both high and low temperatures and rainfall events, with time lags of up to 2 weeks. These results suggest that weather-related mortality may be a public health problem in rural India today. Furthermore, as changes in local climate occur, adaptation measures should be considered to mitigate the potentially negative impacts on public health in these rural communities. PMID:23195513

Assessment of Land Surface Models in a High-Resolution Atmospheric Model during Indian Summer Monsoon

NASA Astrophysics Data System (ADS)

Attada, Raju; Kumar, Prashant; Dasari, Hari Prasad

2018-04-01

Assessment of the land surface models (LSMs) on monsoon studies over the Indian summer monsoon (ISM) region is essential. In this study, we evaluate the skill of LSMs at 10 km spatial resolution in simulating the 2010 monsoon season. The thermal diffusion scheme (TDS), rapid update cycle (RUC), and Noah and Noah with multi-parameterization (Noah-MP) LSMs are chosen based on nature of complexity, that is, from simple slab model to multi-parameterization options coupled with the Weather Research and Forecasting (WRF) model. Model results are compared with the available in situ observations and reanalysis fields. The sensitivity of monsoon elements, surface characteristics, and vertical structures to different LSMs is discussed. Our results reveal that the monsoon features are reproduced by WRF model with all LSMs, but with some regional discrepancies. The model simulations with selected LSMs are able to reproduce the broad rainfall patterns, orography-induced rainfall over the Himalayan region, and dry zone over the southern tip of India. The unrealistic precipitation pattern over the equatorial western Indian Ocean is simulated by WRF-LSM-based experiments. The spatial and temporal distributions of top 2-m soil characteristics (soil temperature and soil moisture) are well represented in RUC and Noah-MP LSM-based experiments during the ISM. Results show that the WRF simulations with RUC, Noah, and Noah-MP LSM-based experiments significantly improved the skill of 2-m temperature and moisture compared to TDS (chosen as a base) LSM-based experiments. Furthermore, the simulations with Noah, RUC, and Noah-MP LSMs exhibit minimum error in thermodynamics fields. In case of surface wind speed, TDS LSM performed better compared to other LSM experiments. A significant improvement is noticeable in simulating rainfall by WRF model with Noah, RUC, and Noah-MP LSMs over TDS LSM. Thus, this study emphasis the importance of choosing/improving LSMs for simulating the ISM phenomena in a regional model.

Improving precipitation forecast with hybrid 3DVar and time-lagged ensembles in a heavy rainfall event

NASA Astrophysics Data System (ADS)

Wang, Yuanbing; Min, Jinzhong; Chen, Yaodeng; Huang, Xiang-Yu; Zeng, Mingjian; Li, Xin

2017-01-01

This study evaluates the performance of three-dimensional variational (3DVar) and a hybrid data assimilation system using time-lagged ensembles in a heavy rainfall event. The time-lagged ensembles are constructed by sampling from a moving time window of 3 h along a model trajectory, which is economical and easy to implement. The proposed hybrid data assimilation system introduces flow-dependent error covariance derived from time-lagged ensemble into variational cost function without significantly increasing computational cost. Single observation tests are performed to document characteristic of the hybrid system. The sensitivity of precipitation forecasts to ensemble covariance weight and localization scale is investigated. Additionally, the TLEn-Var is evaluated and compared to the ETKF(ensemble transformed Kalman filter)-based hybrid assimilation within a continuously cycling framework, through which new hybrid analyses are produced every 3 h over 10 days. The 24 h accumulated precipitation, moisture, wind are analyzed between 3DVar and the hybrid assimilation using time-lagged ensembles. Results show that model states and precipitation forecast skill are improved by the hybrid assimilation using time-lagged ensembles compared with 3DVar. Simulation of the precipitable water and structure of the wind are also improved. Cyclonic wind increments are generated near the rainfall center, leading to an improved precipitation forecast. This study indicates that the hybrid data assimilation using time-lagged ensembles seems like a viable alternative or supplement in the complex models for some weather service agencies that have limited computing resources to conduct large size of ensembles.

The contribution of tropical cyclones to rainfall in Mexico

NASA Astrophysics Data System (ADS)

Agustín Breña-Naranjo, J.; Pedrozo-Acuña, Adrián; Pozos-Estrada, Oscar; Jiménez-López, Salma A.; López-López, Marco R.

Investigating the contribution of tropical cyclones to the terrestrial water cycle can help quantify the benefits and hazards caused by the rainfall generated from this type of hydro-meteorological event. Rainfall induced by tropical cyclones can enhance both flood risk and groundwater recharge, and it is therefore important to characterise its minimum, mean and maximum contributions to a region or country's water balance. This work evaluates the rainfall contribution of tropical depressions, storms and hurricanes across Mexico from 1998 to 2013 using the satellite-derived precipitation dataset TMPA 3B42. Additionally, the sensitivity of rainfall to other datasets was assessed: the national rain gauge observation network, real-time satellite rainfall and a merged product that combines rain gauges with non-calibrated space-borne rainfall measurements. The lower Baja California peninsula had the highest contribution from cyclonic rainfall in relative terms (∼40% of its total annual rainfall), whereas the contributions in the rest of the country showed a low-to-medium dependence on tropical cyclones, with mean values ranging from 0% to 20%. In quantitative terms, southern regions of Mexico can receive more than 2400 mm of cyclonic rainfall during years with significant TC activity. Moreover, (a) the number of tropical cyclones impacting Mexico has been significantly increasing since 1998, but cyclonic contributions in relative and quantitative terms have not been increasing, and (b) wind speed and rainfall intensity during cyclones are not highly correlated. Future work should evaluate the impacts of such contributions on surface and groundwater hydrological processes and connect the knowledge gaps between the magnitude of tropical cyclones, flood hazards, and economic losses.

The influence of El Niño-Southern Oscillation on boreal winter rainfall over Peninsular Malaysia

NASA Astrophysics Data System (ADS)

Richard, Sandra; Walsh, Kevin J. E.

2017-09-01

Multi-scale interactions between El Niño-Southern Oscillation and the Boreal Winter Monsoon contribute to rainfall variations over Malaysia. Understanding the physical mechanisms that control these spatial variations in local rainfall is crucial for improving weather and climate prediction and related risk management. Analysis using station observations and European Centre for Medium-Range Weather Forecasts Interim Reanalysis (ERA-Interim) reanalysis reveals a significant decrease in rainfall during El Niño (EL) and corresponding increase during La Niña particularly north of 2°N over Peninsular Malaysia (PM). It is noted that the southern tip of PM shows a small increase in rainfall during El Niño although not significant. Analysis of the diurnal cycle of rainfall and winds indicates that there are no significant changes in morning and evening rainfall over PM that could explain the north-south disparity. Thus, we suggest that the key factor which might explain the north-south rainfall disparity is the moisture flux convergence (MFC). During the December to January (DJF) period of EL years, except for the southern tip of PM, significant negative MFC causes drying as well as suppression of uplift over most areas. In addition, lower specific humidity combined with moisture flux divergence results in less moisture over PM. Thus, over the areas north of 2°N, less rainfall (less heavy rain days) with smaller diurnal rainfall amplitude explains the negative rainfall anomaly observed during DJF of EL. The same MFC argument might explain the dipolar pattern over other areas such as Borneo if further analysis is performed.

Wind, rain and soil erosion rates on bare and plant covered agriculture plots at the experimental station of El Teularet -Sierra de Enguera, Eastern Spain

NASA Astrophysics Data System (ADS)

Cerdà, A.; Azorin-Molina, C.; Iserloh, Th.

2012-04-01

Soil erosion is being scientifically researched for more tan one century, but there is some knowledge lacks that should be researched. Within the factors of the soil erosion wind and rain were studied, but little is know about the impact of the combination of both. Soil erosion by wind was mainly studied on drylands and agriculture land (Sterk and Spaan, 1997; Bielders et al., 2002; Rajot et al., 2003; Zobeck et al., 2003). Soil erosion by water was studied in many ecosystems but it is especially active on agriculture land (Cerdà et al., 2009) and under Mediterranean climatic conditions (Cerdà et al., 2010). The importance of wind on soil erosion is base in the fact that rainstorms occurs with wind, adding a driving component to the falling raindrops. The influence of wind on raindrops is clear, but there is not measurements and there is no information of this influence under field conditions with natural rainfall events.This paper aims to determine the interaction between wind and rain as factors of the soil losses under Mediterranean climatic conditions and different agriculture managements and land uses. Since 2003, the El Teularet-Serra de Enguera Soil Erosion Experimental Station located in Eastern Spain is measuring the soil losses in plots under different land uses and land managements. The station is devoted to study the soil water erosion processes under rain-fed agriculture fields and the rangelands by means of simulated rainfall experiments and plots of different sizes. The soil erosion measure ments are done by means of 13 plots, each of them composed of 5 subplots of 1, 2, 4, 16 and 48 m2 under different land uses and managements. Two plots are covered by two different types of shrubs: Quercus coccifera and Ulex parviflorus, respectively. Three plots reproduce the use of herbicides, one is ploughed, and three plots follow conservation practices (oats and beans with no-tillage, with tillage, and with a vege- tation cover of weeds). Other plots are covered with straw, chipped branches of olive and with a geotextil developed specifically to control erosion on agricultural fields. The Soil Erosion Experimental Station of the El Teularet-Serra de Enguera is located in Eastern Spain. The station is devoted to study the soil water erosion processes under rain-fed agriculture fields and the rangelands. Agriculture is the main source of sedi ments on the mountainous areas of Spain due to the current management. The exper imental station of the El Teularet-Sierra de Enguera is composed also of a meteorological station with tipping-bucket raingauges (0.2 mm), and sensors that measure soil and air moisture and temperature, wind direction and speed and the sun radiation connected to a data-logger that record these data every five minutes. This paper will review the data collected during the period 2004 to 2011 in order to determine if the wind direction and wind speed determined the soil erosion rates. In this way it will be clarified the infliuence of wind on the soil erosion processes.The results will be compared to the measurement collected at the Montesa experimental station devoted to the study of soil erosion on citrus orchards. The experimental setup within the citrus plantation is being supported by the research project CGL2008- 02879/BTE.

Secular spring rainfall variability at local scale over Ethiopia: trend and associated dynamics

NASA Astrophysics Data System (ADS)

Tsidu, Gizaw Mengistu

2017-10-01

Spring rainfall secular variability is studied using observations, reanalysis, and model simulations. The joint coherent spatio-temporal secular variability of gridded monthly gauge rainfall over Ethiopia, ERA-Interim atmospheric variables and sea surface temperature (SST) from Hadley Centre Sea Ice and SST (HadISST) data set is extracted using multi-taper method singular value decomposition (MTM-SVD). The contemporaneous associations are further examined using partial Granger causality to determine presence of causal linkage between any of the climate variables. This analysis reveals that only the northwestern Indian Ocean secular SST anomaly has direct causal links with spring rainfall over Ethiopia and mean sea level pressure (MSLP) over Africa inspite of the strong secular covariance of spring rainfall, SST in parts of subtropical Pacific, Atlantic, Indian Ocean and MSLP. High secular rainfall variance and statistically significant linear trend show consistently that there is a massive decline in spring rain over southern Ethiopia. This happened concurrently with significant buildup of MSLP over East Africa, northeastern Africa including parts of the Arabian Peninsula, some parts of central Africa and SST warming over all ocean basins with the exception of the ENSO regions. The east-west pressure gradient in response to the Indian Ocean warming led to secular southeasterly winds over the Arabian Sea, easterly over central Africa and equatorial Atlantic. These flows weakened climatological northeasterly flow over the Arabian Sea and southwesterly flow over equatorial Atlantic and Congo basins which supply moisture into the eastern Africa regions in spring. The secular divergent flow at low level is concurrent with upper level convergence due to the easterly secular anomalous flow. The mechanisms through which the northwestern Indian Ocean secular SST anomaly modulates rainfall are further explored in the context of East Africa using a simplified atmospheric general circulation model (AGCM) coupled to mixed-layer oceanic model. The rainfall anomaly (with respect to control simulation), forced by the northwestern Indian Ocean secular SST anomaly and averaged over the 30-year period, exhibits prevalence of dry conditions over East and equatorial Africa in agreement with observation. The atmospheric response to secular SST warming anomaly led to divergent flow at low levels and subsidence at the upper troposphere over regions north of 5° S on the continent and vice versa over the Indian Ocean. This surface difluence over East Africa, in addition to its role in suppressing convective activity, deprives the region of moisture supply from the Indian Ocean as well as the Atlantic and Congo basins.

Linking the Response of Annual Grasslands to Warming and Altered Rainfall Across Scales of Gene Expression, Species, and Ecosystem

NASA Astrophysics Data System (ADS)

Torn, M. S.; Bernard, S. M.; Castanha, C.; Fischer, M. L.; Hopkins, F. M.; Placella, S. A.; St. Clair, S. B.; Salve, R.; Sudderth, E.; Herman, D.; Ackerly, D.; Firestone, M. K.

2007-12-01

Climate change can influence terrestrial ecosystems at multiple biological levels: gene expression, species, and ecosystem. We are studying California grassland mesocosms with seven annual species (five grasses, two forbs) that were started in 2005. In the 2006-2007 growing season, they were exposed to three rainfall treatments (297, 552, and 867 mm y-1) and soil and air temperature (ambient and elevated +4oC) in replicated greenhouses. This presentation will combine plant and ecosystem level results with transcript level analyses associated with key enzymes, such as rubisco and glutamine synthetase (GS). Because rainfall is the dominant climate variable for most processes in this Mediterranean ecosystem, the effect of warming was strongly mediated by rainfall. In fact, we saw significant interactions between temperature and rainfall treatments at all three biological levels. For example, at the ecosystem level, warming led to a decrease in aboveground and total NPP under low rainfall, and an increase under high rainfall. For the dominant species, Avena barbata, warming had no effect under high rainfall, but suppressed Avena NPP in low rainfall. At the same time, warmer, wetter conditions accelerated Avena flowering by almost 15 days. This shift in phenology was presaged by observations at the transcript level. Specifically, in the high temperature, high rainfall treatment, the levels of mRNAs for RbcS and GS2 (encoding the small subunit of rubisco and the chloroplastic isoform of GS, respectively) declined while GS1 (encoding the cytosolic isoform of GS) was upregulated several weeks before heading. The transcript level response (along with soil and plant nitrogen data) indicated the leaf had switched from a carbon and nitrogen sink to a source - consistent with more mature plant function and earlier flowering. Soil CO2 respiration also showed strong rain-by-temperature interactions that were due mainly to changes in root response (respiration and/or exudates) rather than in microbial respiration. Overall, the pervasive rain-by-temperature interactions mean that it may be very difficult to predict the effect of warming alone, without accounting for changes in precipitation (in our Mediterranean system). While predictions of warming of 3-6°C in the next 100 years are fairly certain, changes in precipitation are much more uncertain, with some forecasts drier and others wetter for a given location. We suggest that uncertainty about future precipitation and the interacting influences of temperature and moisture on ecosystems are currently key limitations in predicting ecosystem response to climate change, particularly in Mediterranean ecosystems such as the one studied here.

Climate influence on dengue epidemics in Puerto Rico.

PubMed

Jury, Mark R

2008-10-01

The variability of the insect-borne disease dengue in Puerto Rico was studied in relation to climatic variables in the period 1979-2005. Annual and monthly reported dengue cases were compared with precipitation and temperature data. Results show that the incidence of dengue in Puerto Rico was relatively constant over time despite global warming, possibly due to the offsetting effects of declining rainfall, improving health care and little change in population. Seasonal fluctuations of dengue were driven by rainfall increases from May to November. Year-to-year variability in dengue cases was positively related to temperature, but only weakly associated with local rainfall and an index of El Nino Southern Oscillation (ENSO). Climatic conditions were mapped with respect to dengue cases and patterns in high and low years were compared. During epidemics, a low pressure system east of Florida draws warm humid air over the northwestern Caribbean. Long-term trends in past observed and future projected rainfall and temperatures were studied. Rainfall has declined slowly, but temperatures in the Caribbean are rising with the influence of global warming. Thus, dengue may increase in the future, and it will be necessary to anticipate dengue epidemics using climate forecasts, to reduce adverse health impacts.

Investigation on the Bay of Bengal branch of summer monsoon during normal and delayed onset over Gangetic West Bengal

NASA Astrophysics Data System (ADS)

Das, Debanjana; Mondal, Paramita; Saha, Poulomi; Chaudhuri, Sutapa

2018-06-01

The regional features of Bay of Bengal (BOB) branch of summer monsoon (SM) are examined to identify the causes of delayed onset over Gangetic West Bengal (GWB) in the years having normal onset over Kerala coast. The normal onset over both GWB and Kerala is designated as Normal-Normal (NN) years, while delayed onset over GWB and normal onset over Kerala is termed Normal-Delayed (ND) years. The temperature gradient (TTg), winds at 850 and 150 hPa pressure levels, sea-surface temperature (SST), outgoing long wave radiation (OLR), low-level moisture convergence, instability, and rainfall rate (RR) are analyzed in this study using National Centers for Environmental Prediction and National Oceanic and Atmospheric Administration reanalysis dataset during the period from 1981 to 2015. The result shows that TTg over BOB plays a significant role in controlling the movement of BOB branch of SM. Warm SST is observed to prevail over north BOB during NN years. The divergence at 150 hPa and convergence at 850 hPa pressure levels are found to influence the propagation of BOB branch of SM during both NN and ND years. The winds at 850 hPa level converge over BOB and GWB during NN years, whereas winds converge more over eastern BOB and Indo-Chinese peninsula during ND years. Result depicts abundance of low-level (850-1000 hPa) moisture over eastern BOB and Indo-Chinese peninsula during ND years, whereas moisture is observed to converge over north and north-eastern BOB during NN years. The RR is observed to be slightly higher during NN than ND years. However, it may not be concluded from the analysis that delayed onset over GWB will be responsible for less RR over the study region.

Rain Impact Model Assessment of Near-Surface Salinity Stratification Following Rainfall

NASA Astrophysics Data System (ADS)

Drushka, K.; Jones, L.; Jacob, M. M.; Asher, W.; Santos-Garcia, A.

2016-12-01

Rainfall over oceans produces a layer of fresher surface water, which can have a significant effect on the exchanges between the surface and the bulk mixed layer and also on satellite/in-situ comparisons. For satellite sea surface salinity (SSS) measurements, the standard is the Hybrid Coordinate Ocean Model (HYCOM), but there is a significant difference between the remote sensing sampling depth of 0.01 m and the typical range of 5-10 m of in-situ instruments. Under normal conditions the upper layer of the ocean is well mixed and there is uniform salinity; however, under rainy conditions, there is a dilution of the near-surface salinity that mixes downward by diffusion and by mechanical mixing (gravity waves/wind speed). This significantly modifies the salinity gradient in the upper 1-2 m of the ocean, but these transient salinity stratifications dissipate in a few hours, and the upper layer becomes well mixed at a slightly fresher salinity. Based upon research conducted within the NASA/CONAE Aquarius/SAC-D mission, a rain impact model (RIM) was developed to estimate the change in SSS due to rainfall near the time of the satellite observation, with the objective to identify the probability of salinity stratification. RIM uses HYCOM (which does not include the short-term rain effects) and a NOAA global rainfall product CMORPH to model changes in the near-surface salinity profile in 0.5 h increments. Based upon SPURS-2 experimental near-surface salinity measurements with rain, this paper introduces a term in the RIM model that accounts for the effect of wind speed in the mechanical mixing, which translates into a dynamic vertical diffusivity; whereby a Generalized Ocean Turbulence Model (GOTM) is used to investigate the response to rain events of the upper few meters of the ocean. The objective is to determine how rain and wind forcing control the thickness, stratification strength, and lifetime of fresh lenses and to quantify the impacts of rain-formed fresh lenses on the fresh bias in satellite retrievals of salinity. Results will be presented of comparisons of RIM measurements at depth of a few meters with measurements from in-situ salinity instruments. Also, analytical results will be shown, which assess the accuracy of RIM salinity profiles under a variety of rain rate, wind/wave conditions.

Significant influences of global mean temperature and ENSO on extreme rainfall over Southeast Asia

NASA Astrophysics Data System (ADS)

Villafuerte, Marcelino, II; Matsumoto, Jun

2014-05-01

Along with the increasing concerns on the consequences of global warming, and the accumulating records of disaster related to heavy rainfall events in Southeast Asia, this study investigates whether a direct link can be detected between the rising global mean temperature, as well as the El Niño-Southern Oscillation (ENSO), and extreme rainfall over the region. The maximum likelihood modeling that allows incorporating covariates on the location parameter of the generalized extreme value (GEV) distribution is employed. The GEV model is fitted to annual and seasonal rainfall extremes, which were taken from a high-resolution gauge-based gridded daily precipitation data covering a span of 57 years (1951-2007). Nonstationarities in extreme rainfall are detected over the central parts of Indochina Peninsula, eastern coasts of central Vietnam, northwest of the Sumatra Island, inland portions of Borneo Island, and on the northeastern and southwestern coasts of the Philippines. These nonstationarities in extreme rainfall are directly linked to near-surface global mean temperature and ENSO. In particular, the study reveals that a kelvin increase in global mean temperature anomaly can lead to an increase of 30% to even greater than 45% in annual maximum 1-day rainfall, which were observed pronouncedly over central Vietnam, southern coast of Myanmar, northwestern sections of Thailand, northwestern tip of Sumatra, central portions of Malaysia, and the Visayas island in central Philippines. Furthermore, a pronounced ENSO influence manifested on the seasonal maximum 1-day rainfall; a northward progression of 10%-15% drier condition over Southeast Asia as the El Niño develops from summer to winter is revealed. It is important therefore, to consider the results obtained here for water resources management as well as for adaptation planning to minimize the potential adverse impact of global warming, particularly on extreme rainfall and its associated flood risk over the region. Acknowledgment: This study is supported by the Tokyo Metropolitan Government through its AHRF program.

How rainfall, relative humidity and temperature influence volatile emissions from apple trees in situ.

PubMed

Vallat, Armelle; Gu, Hainan; Dorn, Silvia

2005-07-01

Headspace volatiles from apple-bearing twigs were collected in the field with a Radiello sampler during three different diurnal periods over the complete fruit growing season. Analyses by thermal desorption-GC-MS identified a total of 62 compounds in changing quantities, including the terpenoids alpha-pinene, camphene, beta-pinene, limonene, beta-caryophyllene and (E,E)-alpha-farnesene, the aldehydes (E)-2-hexenal, benzaldehyde and nonanal, and the alcohol (Z)-3-hexen-1-ol. The variations in emission of these plant odours were statistically related to temperature, humidity and rainfall in the field. Remarkably, rainfall had a significant positive influence on changes in volatile release during all three diurnal periods, and further factors of significance were temperature and relative humidity around noon, relative humidity in the late afternoon, and temperature and relative humidity during the night. Rainfall was associated consistently with an increase in the late afternoon in terpene and aldehyde volatiles with a known repellent effect on the codling moth, one of the key pests of apple fruit. During the summer of 2003, a season characterized by below-average rainfall, some postulated effects of drought on trees were tested by establishing correlations with rainfall. Emissions of the wood terpenes alpha-pinene, beta-pinene and limonene were negatively correlated with rainfall. Another monoterpene, camphene, was only detected in this summer but not in the previous years, and its emissions were negatively correlated with rainfall, further supporting the theory that drought can result in higher formation of secondary metabolites. Finally, the two green leaf volatiles (E)-2-hexenal and (Z)-3-hexen-1-ol were negatively correlated with rainfall, coinciding well with the expectation that water deficit stress increases activity of lipoxygenase. To our knowledge, this work represents the first empirical study concerning the influence of abiotic factors on volatile emissions from apple trees in situ.

A monitor for continuous measurement of temperature, pH, and conductance of wet precipitation: Preliminary results from the Adirondack Mountains, New York

USGS Publications Warehouse

Johnsson, P.A.; Reddy, M.M.

1990-01-01

This report describes a continuous wet-only precipitation monitor designed by the U.S. Geological Survey to record variations in rainfall temperature, pH, and specific conductance at 1-min intervals over the course of storms. Initial sampling in the Adirondack Mountains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.This report describes a continuous wet-only precipitation monitor designed by the U.S. Geological Survey to record variations in rainfall temperature, pH, and specific conductance at 1-min intervals over the course of storms. Initial sampling in the Adirondack Mountains showed that rainfall acidity varied over the course of summer storms, with low initial pH values increasing as storm intensity increased.

Pre-Monsoon Drought and Heat Waves in India

NASA Image and Video Library

2015-09-12

In June 2015, news organizations around the world reported on a deadly heat wave in India that killed more than 2,300 people. Prior to the arrival of the summer monsoon in India, weather conditions had been extremely hot and dry. Such conditions can lead to economic and agricultural disaster, human suffering and loss of life. NASA satellite sensors are allowing scientists to characterize pre-monsoon droughts and heat waves and postulate their scientific cause. This figure shows the longitude-time variations, averaged between 21 and 22 degrees North, across the middle of the India subcontinent from mid-April to mid-June. Longitude from the Arabian Sea to the Bay of Bengal is represented on the horizontal axis; while the vertical axis shows the timeframe. Rainfall is shown on the left, soil moisture is in the center, and surface air temperature is on the right. For both years (2012 and 2015), the summer monsoon begins in June, with sharp rises in rainfall and soil moisture, and a sharp drop in air temperature. The hottest and driest weeks occurred just before the summer monsoon onsets. Similar dry and hot periods, varying from one to a few weeks, were observed in 2013 and 2014. Soil moisture as an indication of drought as measured by NASA's Aquarius mission was first available in 2012. Rainfall data are from NASA's Tropical Rainfall Measuring Mission (TRMM), and surface air temperature is from NASA's Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite. The TRMM and Aquarius missions ended in April 2015, before the drought and heat waves. Their data were replaced by those presently available from NASA's Soil Moisture Active Passive Mission (SMAP) and Global Precipitation Mission (GPM) to show the drought and heatwave in 2015. Scientists from NASA's Jet Propulsion Laboratory, Pasadena, California, have shown that during the summer monsoon season, moisture is transported into the India Subcontinent from the Arabian Sea and out to the Bay of Bengal. The difference between moisture input from the west and output to the east is deposited as rain over land. The pre-monsoon drought and heat waves coincide with the short period when moisture is advected out to the Bay of Bengal ahead of input from the Arabian Sea. The onset of southwest monsoon winds begins in the Bay of Bengal and sucks moisture out from the subcontinent earlier than the onset in the Arabian Sea. http://photojournal.jpl.nasa.gov/catalog/PIA19939

Sensitivity of Rainfall Extremes Under Warming Climate in Urban India

NASA Astrophysics Data System (ADS)

Ali, H.; Mishra, V.

2017-12-01

Extreme rainfall events in urban India halted transportation, damaged infrastructure, and affected human lives. Rainfall extremes are projected to increase under the future climate. We evaluated the relationship (scaling) between rainfall extremes at different temporal resolutions (daily, 3-hourly, and 30 minutes), daily dewpoint temperature (DPT) and daily air temperature at 850 hPa (T850) for 23 urban areas in India. Daily rainfall extremes obtained from Global Surface Summary of Day Data (GSOD) showed positive regression slopes for most of the cities with median of 14%/K for the period of 1979-2013 for DPT and T850, which is higher than Clausius-Clapeyron (C-C) rate ( 7%). Moreover, sub-daily rainfall extremes are more sensitive to both DPT and T850. For instance, 3-hourly rainfall extremes obtained from Tropical Rainfall Measurement Mission (TRMM 3B42 V7) showed regression slopes more than 16%/K aginst DPT and T850 for the period of 1998-2015. Half-hourly rainfall extremes from the Integrated Multi-satellitE Retrievals (IMERGE) of Global precipitation mission (GPM) also showed higher sensitivity against changes in DPT and T850. The super scaling of rainfall extremes against changes in DPT and T850 can be attributed to convective nature of precipitation in India. Our results show that urban India may witness non-stationary rainfall extremes, which, in turn will affect stromwater designs and frequency and magniture of urban flooding.

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.

Role of mixed precipitating cloud systems on the typhoon rainfall

NASA Astrophysics Data System (ADS)

Pan, C. J.; Krishna Reddy, K.; Lai, H. C.; Yang, S. S.

2010-01-01

L-band wind profiler data are utilized to diagnose the vertical structure of the typhoon precipitating cloud systems in Taiwan. For several typhoons, a pronounced bright band (BB) around 5 km is commonly observed from the observation. Since strong convection within typhoon circulation may disturb and/or disrupt the melting layer, the BB shall not appear persistently. Hence, an understanding of the vertical structure of the BB region is important because it holds extensive hydrometeors information on the type of precipitation and its variability. Wind profiler observational results suggest that the mixture of convective and stratiform (embedded type) clouds are mostly associated with typhoons. In the case of one typhoon, BB is appeared around 5.5 km with embedded precipitation and also BB height of 1 km higher than ordinary showery precipitation. This is evident from the long-term observations of wind profiler and Tropical Rainfall Measuring Mission. The Doppler velocity profiles show hydrometers (ice/snow) at 6 km but liquid below 5 km for typhoons and 4 km for showery precipitation. In the BB region the melting particles accelerations of 5.8 ms-1 km-1 and 3.2 ms-1 km-1 are observed for typhoon and showery precipitation, respectively.

Tropical Rainfall Measuring Mission (TRMM) and the Future of Rainfall Estimation from Space

NASA Technical Reports Server (NTRS)

Kakar, Ramesh; Adler, Robert; Smith, Eric; Starr, David OC. (Technical Monitor)

2001-01-01

Tropical rainfall is important in the hydrological cycle and to the lives and welfare of humans. Three-fourths of the energy that drives the atmospheric wind circulation comes from the latent heat released by tropical precipitation. Recognizing the importance of rain in the tropics, NASA for the U.S.A. and NASDA for Japan have partnered in the design, construction and flight of a satellite mission to measure tropical rainfall and calculate the associated latent heat release. The Tropical Rainfall Measuring Mission (TRMM) satellite was launched on November 27, 1997, and data from all the instruments first became available approximately 30 days after launch. Since then, much progress has been made in the calibration of the sensors, the improvement of the rainfall algorithms and applications of these results to areas such as Data Assimilation and model initialization. TRMM has reduced the uncertainty of climatological rainfall in tropics by over a factor of two, therefore establishing a standard for comparison with previous data sets and climatologies. It has documented the diurnal variation of precipitation over the oceans, showing a distinct early morning peak and this satellite mission has shown the utility of precipitation information for the improvement of numerical weather forecasts and climate modeling. This paper discusses some promising applications using TRMM data and introduces a measurement concept being discussed by NASA/NASDA and ESA for the future of rainfall estimation from space.

The "Weekend Effect" in Summertime U.S. Rainfall: Evidence for Midweek Intensification of Storms by Pollution

NASA Astrophysics Data System (ADS)

Bell, T. L.; Rosenfeld, D.; Kim, K.; Hahnenberger, M.

2006-05-01

Persistent and strong dependence of rain rate on the day of the week has been found in Tropical Rainfall Measuring Mission (TRMM) satellite estimates of summer afternoon rainfall over the southeast U.S. and the nearby Atlantic from 1998 to 2005. Midweek (Tue--Thu) rain rates and rain area appear to increase over land, and this increase is accompanied by a corresponding diminution of rainfall over nearby waters. Reanalysis data from atmospheric models suggest that there is a corresponding weekly variation in atmospheric winds consistent with the changes in rainfall. These variations are almost certainly caused by weekly variations in human activity. The most likely cause of the observed changes in rainfall is the well documented weekly variation in atmospheric pollution. Particulate pollution is highest in the middle of the week. Considerable observational and modeling evidence has accumulated concerning the effects of aerosols on precipitation. Most of this evidence relates to the suppression of precipitation by aerosols, but it has been argued that storms in highly unstable moist environments can be invigorated by aerosols, and some modeling studies seem to confirm this. The strong weekly cycle in rainfall observed over the southeast U.S. along with what appears to be dynamical suppression of rainfall over the nearby Atlantic, and the lack of an observable cycle over the southwest U.S., are consistent with this theory.

Weekend Effect" in Summertime U.S. Rainfall: Evidence for Midweek Intensification of Storms by Pollution

NASA Technical Reports Server (NTRS)

Bell, Thomas L.; Rosenfeld, Daniel; Kim, Kyu-Myong; Hahnenberger, Maura

2006-01-01

Persistent and strong dependence of rain rate on the day of the week has been found in Tropical Rainfall Measuring Mission (TRMM) satellite estimates of summer afternoon rainfall over the southeast U.S. and the nearby Atlantic from 1998 to 2005. Midweek (Tue-Thu) rain rates and rain area appear to increase over land, and this increase is accompanied by a corresponding diminution of rainfall over nearby waters. Reanalysis data from atmospheric models, suggest that there is a corresponding weekly variation in atmospheric winds consistent with the changes in rainfall. These variations are almost certainly caused by weekly variations in human activity. The most likely cause of the observed changes in rainfall is the well documented weekly variation in atmospheric pollution. Particulate pollution is highest in the middle of the week. Considerable observational and modeling evidence has accumulated concerning the effects of aerosols on precipitation. Most of this evidence relates to the suppression of precipitation by aerosols, but it has been argued that storms in highly unstable moist environments can be invigorated by aerosols, and some modeling studies seem to confirm this. The strong weekly cycle in rainfall observed over the southeast U.S. along with what appears to be dynamical suppression of rainfall over the nearby Atlantic, and the lack of an observable cycle over the southwest U.S., are consistent with this theory.

Coupled ocean-atmosphere surface variability and its climate impacts in the tropical Atlantic region

NASA Astrophysics Data System (ADS)

Fontaine, B.; Janicot, Serge; Roucou, P.

This study examines time evolution and statistical relationships involving the two leading ocean-atmosphere coupled modes of variability in the tropical Atlantic and some climate anomalies over the tropical 120°W-60°W region using selected historical files (75-y near global SSTs and precipitation over land), more recent observed data (30-y SST and pseudo wind stress in the tropical Atlantic) and reanalyses from the US National Centers for Environmental Prediction (NCEP/NCAR) reanalysis System on the period 1968-1997: surface air temperature, sea level pressure, moist static energy content at 850 hPa, precipitable water and precipitation. The first coupled mode detected through singular value decomposition of the SST and pseudo wind-stress data over the tropical Atlantic (30°N-20°S) expresses a modulation in the thermal transequatorial gradient of SST anomalies conducted by one month leading wind-stress anomalies mainly in the tropical north Atlantic during northern winter and fall. It features a slight dipole structure in the meridional plane. Its time variability is dominated by a quasi-decadal signal well observed in the last 20-30 ys and, when projected over longer-term SST data, in the 1920s and 1930s but with shorter periods. The second coupled mode is more confined to the south-equatorial tropical Atlantic in the northern summer and explains considerably less wind-stress/SST cross-covariance. Its time series features an interannual variability dominated by shorter frequencies with increased variance in the 1960s and 1970s before 1977. Correlations between these modes and the ENSO-like Nino3 index lead to decreasing amplitude of thermal anomalies in the tropical Atlantic during warm episodes in the Pacific. This could explain the nonstationarity of meridional anomaly gradients on seasonal and interannual time scales. Overall the relationships between the oceanic component of the coupled modes and the climate anomaly patterns denote thermodynamical processes at the ocean/atmosphere interface that create anomaly gradients in the meridional plane in a way which tends to alter the north-south movement of the seasonal cycle. This appears to be consistent with the intrinsic non-dipole character of the tropical Atlantic surface variability at the interannual time step and over the recent period, but produces abnormal amplitude and/or delayed excursions of the intertropical convergence zone (ITCZ). Connections with continental rainfall are approached through three (NCEP/NCAR and observed) rainfall indexes over the Nordeste region in Brazil, and the Guinea and Sahel zones in West Africa. These indices appear to be significantly linked to the SST component of the coupled modes only when the two Atlantic modes+the ENSO-like Nino3 index are taken into account in the regressions. This suggests that thermal forcing of continental rainfall is particularly sensitive to the linear combinations of some basic SST patterns, in particular to those that create meridional thermal gradients. The first mode in the Atlantic is associated with transequatorial pressure, moist static energy and precipitable water anomaly patterns which can explain abnormal location of the ITCZ particularly in northern winter, and hence rainfall variations in Nordeste. The second mode is more associated with in-phase variations of the same variables near the southern edge of the ITCZ, particularly in the Gulf of Guinea during the northern spring and winter. It is primarily linked to the amplitude and annual phase of the ITCZ excursions and thus to rainfall variations in Guinea. Connections with Sahel rainfall are less clear due to the difficulty for the model to correctly capture interannual variability over that region but the second Atlantic mode and the ENSO-like Pacific variability are clearly involved in the Sahel climate interannual fluctuations: anomalous dry (wet) situations tend to occur when warmer (cooler) waters are present in the eastern Pacific and the gulf of Guinea in northern summer which contribute to create a northward (southward) transequatorial anomaly gradient in sea level pressure over West Africa.

PROBABILISTIC HAZARD ASSESSMENT FOR TORNADOES, STRAIGHT-LINE WIND, AND EXTREME PRECIPITATION AT THE SAVANNAH RIVER SITE

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

Werth, D.; NOEMAIL), A.; Shine, G.

Recent data sets for three meteorological phenomena with the potential to inflict damage on SRS facilities - tornadoes, straight winds, and heavy precipitation - are analyzed using appropriate statistical techniques to estimate occurrence probabilities for these events in the future. Summaries of the results for DOE-mandated return periods and comparisons to similar calculations performed in 1998 by Weber, et al., are given. Using tornado statistics for the states of Georgia and South Carolina, we calculated the probability per year of any location within a 2⁰ square area surrounding SRS being struck by a tornado (the ‘strike’ probability) and the probabilitymore » that any point will experience winds above set thresholds. The strike probability was calculated to be 1.15E-3 (1 chance in 870) per year and wind speeds for DOE mandated return periods of 50,000 years, 125,000 years, and 1E+7 years (USDOE, 2012) were estimated to be 136 mph, 151 mph and 221 mph, respectively. In 1998 the strike probability for SRS was estimated to be 3.53 E-4 and the return period wind speeds were 148 mph every 50,000 years and 180 mph every 125,000 years. A 1E+7 year tornado wind speed was not calculated in 1998; however a 3E+6 year wind speed was 260 mph. The lower wind speeds resulting from this most recent analysis are largely due to new data since 1998, and to a lesser degree differences in the models used. By contrast, default tornado wind speeds taken from ANSI/ANS-2.3-2011 are somewhat higher: 161 mph for return periods of 50,000 years, 173 mph every 125,000 years, and 230 mph every 1E+7 years (ANS, 2011). Although the ANS model and the SRS models are very similar, the region defined in ANS 2.3 that encompasses the SRS also includes areas of the Great Plains and lower Midwest, regions with much higher occurrence frequencies of strong tornadoes. The SRS straight wind values associated with various return periods were calculated by fitting existing wind data to a Gumbel distribution, and extrapolating the values for any return period from the tail of that function. For the DOE mandated return periods, we expect straight winds of 123 mph every 2500 years, and 132mph every 6250 years at any point within the SRS. These values are similar to those from the W98 report (which also used the Gumbel distribution for wind speeds) which gave wind speeds of 115mph and 122 mph for return periods of 2500 years and 6250 years, respectively. For extreme precipitation accumulation periods, we compared the fits of three different theoretical extreme-value distributions, and in the end decided to maintain the use of the Gumbel distribution for each period. The DOE mandated 6-hr accumulated rainfall for return periods of 2500 years and 6250 years was estimated as 7.8 inches and 8.4 inches, respectively. For the 24- hr rainfall return periods of 10,000 years and 25,000 years, total rainfall estimates were 10.4 inches and 11.1 inches, respectively. These values are substantially lower than comparable values provided in the W98 report. This is largely a consequence of the W98 use of a different extreme value distribution with its corresponding higher extreme probabilities.« less

Biological soil crust succession impact on soil moisture and temperature in the sub-surface along a rainfall gradient

NASA Astrophysics Data System (ADS)

Zaady, E.; Yizhaq, H.; Ashkenazy, Y.

2012-04-01

Biological soil crusts produce mucilage sheets of polysaccharides that cover the soil surface. This hydrophobic coating can seal the soil micro-pores and thus cause reduction of water permeability and may influence soil temperature. This study evaluates the impact of crust composition on sub-surface water and temperature over time. We hypothesized that the successional stages of biological soil crusts, affect soil moisture and temperature differently along a rainfall gradient throughout the year. Four experimental sites were established along a rainfall gradient in the western Negev Desert. At each site three treatments; crust removal, pure sand (moving dune) and natural crusted were monitored. Crust successional stage was measured by biophysiological and physical measurements, soil water permeability by field mini-Infiltrometer, soil moisture by neutron scattering probe and temperature by sensors, at different depths. Our main interim conclusions from the ongoing study along the rainfall gradient are: 1. the biogenic crust controls water infiltration into the soil in sand dunes, 2. infiltration was dependent on the composition of the biogenic crust. It was low for higher successional stage crusts composed of lichens and mosses and high with cyanobacterial crust. Thus, infiltration rate controlled by the crust is inverse to the rainfall gradient. Continuous disturbances to the crust increase infiltration rates, 3. despite the different rainfall amounts at the sites, soil moisture content below 50 cm is almost the same. We therefore predict that climate change in areas that are becoming dryer (desertification) will have a positive effect on soil water content and vice versa.

Application of SDSM and LARS-WG for simulating and downscaling of rainfall and temperature

NASA Astrophysics Data System (ADS)

Hassan, Zulkarnain; Shamsudin, Supiah; Harun, Sobri

2014-04-01

Climate change is believed to have significant impacts on the water basin and region, such as in a runoff and hydrological system. However, impact studies on the water basin and region are difficult, since general circulation models (GCMs), which are widely used to simulate future climate scenarios, do not provide reliable hours of daily series rainfall and temperature for hydrological modeling. There is a technique named as "downscaling techniques", which can derive reliable hour of daily series rainfall and temperature due to climate scenarios from the GCMs output. In this study, statistical downscaling models are used to generate the possible future values of local meteorological variables such as rainfall and temperature in the selected stations in Peninsular of Malaysia. The models are: (1) statistical downscaling model (SDSM) that utilized the regression models and stochastic weather generators and (2) Long Ashton research station weather generator (LARS-WG) that only utilized the stochastic weather generators. The LARS-WG and SDSM models obviously are feasible methods to be used as tools in quantifying effects of climate change condition in a local scale. SDSM yields a better performance compared to LARS-WG, except SDSM is slightly underestimated for the wet and dry spell lengths. Although both models do not provide identical results, the time series generated by both methods indicate a general increasing trend in the mean daily temperature values. Meanwhile, the trend of the daily rainfall is not similar to each other, with SDSM giving a relatively higher change of annual rainfall compared to LARS-WG.

Temperature and rainfall are related to fertility rate after spring artificial insemination in small ruminants

NASA Astrophysics Data System (ADS)

Abecia, J. A.; Arrébola, F.; Macías, A.; Laviña, A.; González-Casquet, O.; Benítez, F.; Palacios, C.

2016-10-01

A total number of 1092 artificial inseminations (AIs) performed from March to May were documented over four consecutive years on 10 Payoya goat farms (36° N) and 19,392 AIs on 102 Rasa Aragonesa sheep farms (41° N) over 10 years. Mean, maximum, and minimum ambient temperatures, mean relative humidity, mean solar radiation, and total rainfall on each insemination day were recorded. Overall, fertility rates were 58 % in goats and 45 % in sheep. The fertility rates of the highest and lowest deciles of each of the meteorological variables indicated that temperature and rainfall had a significant effect on fertility in goats. Specifically, inseminations that were performed when mean (68 %), maximum (68 %), and minimum (66 %) temperatures were in the highest decile, and rainfall was in the lowest decile (59 %), had a significantly ( P < 0.0001) higher proportion of does that became pregnant than did the ewes in the lowest decile (56, 54, 58, and 49 %, respectively). In sheep, the fertility rates of the highest decile of mean (62 %), maximum (62 %), and minimum (52 %) temperature, RH (52 %), THI (53 %), and rainfall (45 %) were significantly higher ( P < 0.0001) than were the fertility rates among ewes in the lowest decile (46, 45, 45, 45, 46, and 43 %, respectively). In conclusion, weather was related to fertility in small ruminants after AI in spring. It remains to be determined whether scheduling the dates of insemination based on forecasted temperatures can improve the success of AI in goats and sheep.

Long-range Prediction of climatic Change in the Eastern Seaboard of Thailand over the 21st Century using various Downscaling Approaches

NASA Astrophysics Data System (ADS)

Bejranonda, Werapol; Koch, Manfred; Koontanakulvong, Sucharit

2010-05-01

Triggered by a long drought, a huge water supply crisis took place at the Eastern Seaboard of Thailand (east of the Gulf of Thailand) in 2005. In that year no rainfall occurred for four months after the beginning of the rainy season which led to the situation that the industrial estates of the Eastern Seaboard were not able to fully operate. Normally, most of the urban and industrial water used in this coastal region along east of the Gulf of Thailand, which is part of the Pacific Ocean, is surface water stored in a large-scale reservoir-network across the main watershed in the region. Thus the three major reservoirs usually gather water from monsoon storms that blow from the South and provide accumulative 80% of the annual rainfall during the 6 months of the rainy season which normally lasts from May-October. During the dry season (November - April) the winds are blowing from northern Indo-China land mass and rain drops only a few days in a month. Because of this typical tropical climate system, surface water resources across most of the southeastern Asia-Pacific region and the Eastern Seaboard of Thailand, in particular, rely on the annual occurrence of the monsoon season. There is now sufficient evidence that the named extreme weather conditions of 2005 occurring in that part of Thailand are not a singularity, but might be another signal of recent ongoing climate change in that country as a whole. Because of this imminent threat to the water resources of the region, and for the set-up of appropriate water management schemes for the near future, a climate impact study is proposed here. More specifically, the water budget of the Khlong Yai basin, which is the main watershed of the Eastern Seaboard, is modeled using the distributed hydrological model SWAT. To that avail the watershed model is coupled sequentially to a global climate model (GCM), whereby the latter provides the input forcing parameters (e.g. precipitation and temperature) to the former. Because of the different scales of the hydrological (local to regional) and of the GCM (global), one is faced with the problem of 'downscaling' the coarse grid resolution output of the GCM to the fine grid of the hydrological model. Although there have been numerous downscaling approaches proposed to that regard over the last decade, the jury is still out about the best method to use in a particular application. The focus here is on the downscaling part of the investigation, i.e. the proper preparation of the GCM's output to serve as input, i.e. the driving force, to the hydrological model (which is not further discussed here). Daily ensembles of climate variables computed by means of the CGCM3 model of the Canadian Climate Center which has a horizontal grid resolution of approximately the size of the whole study basin are used here, indicating clearly the need for downscaling. Daily observations of local climate variables available since 1971 are used as additional input to the various downscaling tools proposed which are, namely, the stochastic weather generator (LARS-WG), the statistical downscaling model (SDSM), and a multiple linear regression model between the observed variables and the CGCM3 predictors. Both the 2D and the 3D versions of the CGCM3 model are employed to predict, 100 years ahead up to year 2100, the monthly rainfall and temperatures, based on the past calibration period (training period) 1971-2000. To investigate the prediction performance, multiple linear regression, autoregressive (AR) and autoregressive integrated moving average (ARIMA) models are applied to the time series of the observation data which are aggregated into monthly time steps to be able compare them with the downscaling results above. Likewise, multiple linear regression and ARIMA models also executed on the CGCM3 predictors and the Pacific / Indian oceans indices as external regressors to predict short-term local climate variations. The results of the various downscaling method are validated for years 2001-2006 at selected meteorological stations in the Khlong Yai basin, assuming the IPCC's A1B and A2 emission scenarios. The performance of the monthly climate prediction has been evaluated by comparison with observed data using the Nash-Sutcliffe model efficiency measure. Among the statistical/stochastical downscaling and the forecasting methods used, the climate prediction by the ARIMA model with ocean indices and CGCM predictor included as external regressors are the most reliable. Thus for the verification period 2001-2006 Nash-Sutcliffe coefficient of 0.84, 0.47 and 0.50 are obtained for the minimum and maximum temperatures and the rainfall, respectively, whereas the corresponding 1-year ahead predictions are 0.77, 0.43 and 0.48, respectively. The best external regressor for the prediction of the minimum temperatures in the basin is, surprisingly, the El Niño 1.2 SST anomaly time series; for the prediction of the maximum temperatures, the minimum surface air temperature predictor in CGCM3 (tasmin); and for the prediction of the rainfall, the 850hPa eastward-wind predictor in CGCM3 (p8_uas). Based on year 2000, the downscaling results show that the average minimum temperature will be higher by 0.4 to 5.9 ° C by year 2100, while the average maximum temperature will be rather stable, with only little change between -0.2 to +0.3° C. As for the rainfall at year 2100, a possible change from +0.2 to 12.0 mm/month is obtained. These climate prediction results mean that, although there will be more rainfall in the future, the much higher temperature will lead to more evapotranspiration, i.e. more agricultural water demand. Besides, the increasing rainfall will most likely lead to unexpected flood events in the future that will require precautionary planning at the watershed-scale. This will be further analyzed during the course of the ongoing study using the SWAT hydrological model mentioned above.

Extreme climatic events drive mammal irruptions: regression analysis of 100-year trends in desert rainfall and temperature

PubMed Central

Greenville, Aaron C; Wardle, Glenda M; Dickman, Chris R

2012-01-01

Extreme climatic events, such as flooding rains, extended decadal droughts and heat waves have been identified increasingly as important regulators of natural populations. Climate models predict that global warming will drive changes in rainfall and increase the frequency and severity of extreme events. Consequently, to anticipate how organisms will respond we need to document how changes in extremes of temperature and rainfall compare to trends in the mean values of these variables and over what spatial scales the patterns are consistent. Using the longest historical weather records available for central Australia – 100 years – and quantile regression methods, we investigate if extreme climate events have changed at similar rates to median events, if annual rainfall has increased in variability, and if the frequency of large rainfall events has increased over this period. Specifically, we compared local (individual weather stations) and regional (Simpson Desert) spatial scales, and quantified trends in median (50th quantile) and extreme weather values (5th, 10th, 90th, and 95th quantiles). We found that median and extreme annual minimum and maximum temperatures have increased at both spatial scales over the past century. Rainfall changes have been inconsistent across the Simpson Desert; individual weather stations showed increases in annual rainfall, increased frequency of large rainfall events or more prolonged droughts, depending on the location. In contrast to our prediction, we found no evidence that intra-annual rainfall had become more variable over time. Using long-term live-trapping records (22 years) of desert small mammals as a case study, we demonstrate that irruptive events are driven by extreme rainfalls (>95th quantile) and that increases in the magnitude and frequency of extreme rainfall events are likely to drive changes in the populations of these species through direct and indirect changes in predation pressure and wildfires. PMID:23170202

Lower Boundary Forcing related to the Occurrence of Rain in the Tropical Western Pacific

NASA Astrophysics Data System (ADS)

Li, Y.; Carbone, R. E.

2013-12-01

Global weather and climate models have a long and somewhat tortured history with respect to simulation and prediction of tropical rainfall in the relative absence of balanced flow in the geostrophic sense. An important correlate with tropical rainfall is sea surface temperature (SST). The introduction of SST information to convective rainfall parameterization in global models has improved model climatologies of tropical oceanic rainfall. Nevertheless, large systematic errors have persisted, several of which are common to most atmospheric models. Models have evolved to the point where increased spatial resolution demands representation of the SST field at compatible temporal and spatial scales, leading to common usage of monthly SST fields at scales of 10-100 km. While large systematic errors persist, significant skill has been realized from various atmospheric and coupled ocean models, including assimilation of weekly or even daily SST fields, as tested by the European Center for Medium Range Weather Forecasting. A few investigators have explored the role of SST gradients in relation to the occurrence of precipitation. Some of this research has focused on large scale gradients, mainly associated with surface ocean-atmosphere climatology. These studies conclude that lower boundary atmospheric convergence, under some conditions, could be substantially enhanced over SST gradients, destabilizing the atmosphere, and thereby enabling moist convection. While the concept has a firm theoretical foundation, it has not gained a sizeable following far beyond the realm of western boundary currents. Li and Carbone 2012 examined the role of transient mesoscale (~ 100 km) SST gradients in the western Pacific warm pool by means of GHRSST and CMORPH rainfall data. They found that excitation of deep moist convection was strongly associated with the Laplacian of SST (LSST). Specifically, -LSST is associated with rainfall onset in 75% of 10,000 events over 4 years, whereas the background ocean is symmetric about zero Laplacian. This finding is fully consistent with theory for gradients of order ~1degC in low mean wind conditions, capable of inducing atmospheric convergence of N x 10-5s-1. We will present new findings resulting from the application of a Madden-Julian oscillation (MJO) passband filter to GHRSST/CMORPH data. It shows that the -LSST field organizes at scales of 1000-2000 km and can persist for periods of two weeks to 3 months. Such -LSST anomalies are in quadrature with MJO rainfall, tracking and leading the wet phase of the MJO by 10-14 days, from the Indian Ocean to the dateline. More generally, an evaluation of SST structure in rainfall production will be presented, which represents a decidedly alternative view to conventional wisdom. Li, Yanping, and R.E. Carbone, 2012: Excitation of Rainfall over the Tropical Western Pacific, J. Atmos. Sci., 69, 2983-2994.

Analysis of the variation of the 0°C isothermal altitude during rainfall events

NASA Astrophysics Data System (ADS)

Zeimetz, Fränz; Garcìa, Javier; Schaefli, Bettina; Schleiss, Anton J.

2016-04-01

In numerous countries of the world (USA, Canada, Sweden, Switzerland,…), the dam safety verifications for extreme floods are realized by referring to the so called Probable Maximum Flood (PMF). According to the World Meteorological Organization (WMO), this PMF is determined based on the PMP (Probable Maximum Precipitation). The PMF estimation is performed with a hydrological simulation model by routing the PMP. The PMP-PMF simulation is normally event based; therefore, if no further information is known, the simulation needs assumptions concerning the initial soil conditions such as saturation or snow cover. In addition, temperature series are also of interest for the PMP-PMF simulations. Temperature values can not only be deduced from temperature measurement but also using the temperature gradient method, the 0°C isothermal altitude can lead to temperature estimations on the ground. For practitioners, the usage of the isothermal altitude for referring to temperature is convenient and simpler because one value can give information over a large region under the assumption of a certain temperature gradient. The analysis of the evolution of the 0°C isothermal altitude during rainfall events is aimed here and based on meteorological soundings from the two sounding stations Payerne (CH) and Milan (I). Furthermore, hourly rainfall and temperature data are available from 110 pluviometers spread over the Swiss territory. The analysis of the evolution of the 0°C isothermal altitude is undertaken for different precipitation durations based on the meteorological measurements mentioned above. The results show that on average, the isothermal altitude tends to decrease during the rainfall events and that a correlation between the duration of the altitude loss and the duration of the rainfall exists. A significant difference in altitude loss is appearing when the soundings from Payerne and Milan are compared.

Constraining the Sensitivity of Amazonian Rainfall with Observations of Surface Temperature

NASA Astrophysics Data System (ADS)

Dolman, A. J.; von Randow, C.; de Oliveira, G. S.; Martins, G.; Nobre, C. A.

2016-12-01

Earth System models generally do a poor job in predicting Amazonian rainfall, necessitating the need to look for observational constraints on their predictability. We use observed surface temperature and precipitation of the Amazon and a set of 21 CMIP5 models to derive an observational constraint of the sensitivity of rainfall to surface temperature (dP/dT). From first principles such a relation between the surface temperature of the earth and the amount of precipitation through the surface energy balance should exist, particularly in the tropics. When de-trended anomalies in surface temperature and precipitation from a set of datasets are plotted, a clear linear relation between surface temperature and precipitation appears. CMIP5 models show a similar relation with relatively cool models having a larger sensitivity, producing more rainfall. Using the ensemble of models and the observed surface temperature we were able to derive an emerging constraint, reducing the dPdt sensitivity of the CMIP5 model from -0.75 mm day-1 0C-1 (+/- 0.54 SD) to -0.77 mm day-1 0C-1 with a reduced uncertainty of about a factor 5. dPdT from the observation is -0.89 mm day-1 0C-1 . We applied the method to wet and dry season separately noticing that in the wet season we shifted the mean and reduced uncertainty, while in the dry season we very much reduced uncertainty only. The method can be applied to other model simulations such as specific deforestation scenarios to constrain the sensitivity of rainfall to surface temperature. We discuss the implications of the constrained sensitivity for future Amazonian predictions.

Death from respiratory diseases and temperature in Shiraz, Iran (2006-2011).

PubMed

Dadbakhsh, Manizhe; Khanjani, Narges; Bahrampour, Abbas; Haghighi, Pegah Shoae

2017-02-01

Some studies have suggested that the number of deaths increases as temperatures drops or rises above human thermal comfort zone. The present study was conducted to evaluate the relation between respiratory-related mortality and temperature in Shiraz, Iran. In this ecological study, data about the number of respiratory-related deaths sorted according to age and gender as well as average, minimum, and maximum ambient air temperatures during 2007-2011 were examined. The relationship between air temperature and respiratory-related deaths was calculated by crude and adjusted negative binomial regression analysis. It was adjusted for humidity, rainfall, wind speed and direction, and air pollutants including CO, NO x , PM 10 , SO 2 , O 3 , and THC. Spearman and Pearson correlations were also calculated between air temperature and respiratory-related deaths. The analysis was done using MINITAB16 and STATA 11. During this period, 2598 respiratory-related deaths occurred in Shiraz. The minimum number of respiratory-related deaths among all subjects happened in an average temperature of 25 °C. There was a significant inverse relationship between average temperature- and respiratory-related deaths among all subjects and women. There was also a significant inverse relationship between average temperature and respiratory-related deaths among all subjects, men and women in the next month. The results suggest that cold temperatures can increase the number of respiratory-related deaths and therefore policies to reduce mortality in cold weather, especially in patients with respiratory diseases should be implemented.

Death from respiratory diseases and temperature in Shiraz, Iran (2006-2011)

NASA Astrophysics Data System (ADS)

Dadbakhsh, Manizhe; Khanjani, Narges; Bahrampour, Abbas; Haghighi, Pegah Shoae

2017-02-01

Some studies have suggested that the number of deaths increases as temperatures drops or rises above human thermal comfort zone. The present study was conducted to evaluate the relation between respiratory-related mortality and temperature in Shiraz, Iran. In this ecological study, data about the number of respiratory-related deaths sorted according to age and gender as well as average, minimum, and maximum ambient air temperatures during 2007-2011 were examined. The relationship between air temperature and respiratory-related deaths was calculated by crude and adjusted negative binomial regression analysis. It was adjusted for humidity, rainfall, wind speed and direction, and air pollutants including CO, NOx, PM10, SO2, O3, and THC. Spearman and Pearson correlations were also calculated between air temperature and respiratory-related deaths. The analysis was done using MINITAB16 and STATA 11. During this period, 2598 respiratory-related deaths occurred in Shiraz. The minimum number of respiratory-related deaths among all subjects happened in an average temperature of 25 °C. There was a significant inverse relationship between average temperature- and respiratory-related deaths among all subjects and women. There was also a significant inverse relationship between average temperature and respiratory-related deaths among all subjects, men and women in the next month. The results suggest that cold temperatures can increase the number of respiratory-related deaths and therefore policies to reduce mortality in cold weather, especially in patients with respiratory diseases should be implemented.

Exploration of discrepancy between radar and gauge rainfall estimates driven by wind fields

NASA Astrophysics Data System (ADS)

Dai, Qiang; Han, Dawei

2014-11-01

Due to the fact that weather radar is prone to several sources of errors, it is acknowledged that adjustment against ground observations such as rain gauges is crucial for radar measurement. Spatial matching of precipitation patterns between radar and rain gauge is a significant premise in radar bias corrections. It is a conventional way to construct radar-gauge pairs based on their vertical locations. However, due to the wind effects, the raindrops observed by the radar do not always fall vertically to the ground, and the raindrops arriving at the ground may not all be caught by the rain gauge. This study proposes a fully formulated scheme to numerically simulate the movement of raindrops in a three-dimensional wind field in order to adjust the wind-induced errors. The Brue catchment (135 km2) in Southwest England covering 28 radar pixels and 49 rain gauges is an experimental catchment, where the radar central beam height varies between 500 and 700 m. The 20 typical events (with durations of 6-36 h) are chosen to assess the correlation between hourly radar and gauge rainfall surfaces. It is found that for most events, the improved rates of correlation coefficients are greater than 10%, and nearly half of the events increase by 20%. With the proposed method, except four events, all the event-averaged correlation values are greater than 0.5. This work is the first study to tackle both wind effects on radar and rain gauges, which could be considered as one of the essential components in processing radar observational data in its hydrometeorological applications.

Impact of Tropical Cyclones on Soil Moisture over East Asia

NASA Astrophysics Data System (ADS)

Liess, S.

2016-12-01

A simulation of a series of three strong typhoons (Frankie, Gloria, and Herb) during the 1996 typhoon season shows that the Weather Research and Forecasting (WRF) model is representing the general characteristics of each typhoon, including sharp right turns by Gloria and Herb over the Philippine Sea. These sharp right turns can be attributed to tropical easterly waves and they are responsible for landfall over Taiwan, instead of following the general direction toward the Philippines. A second simulation where the typhoon signal is removed before landfall over East Asia shows that both rainfall and soil moisture is increased by up to 30% in coastal regions after landfall, mostly to the north of the landfall region. However, despite the noisier signal in rainfall, significant increases in soil moisture related to the paths of the simulated typhoons occur as far west as western China and Myanmar. Strong winds associated with the typhoons can also increase local evaporation and thus locally reduce soil moisture, especially south of the landfall region. Detailed observations of hydrologic variables such as soil moisture are needed to evaluate these model studies not only over coastal regions but also further inland where typhoon signals are weaker but local moisture availability is still influenced by increased rainfall and stronger winds.

Mineralogical evidence of reduced East Asian summer monsoon rainfall on the Chinese loess plateau during the early Pleistocene interglacials

NASA Astrophysics Data System (ADS)

Meng, Xianqiang; Liu, Lianwen; Wang, Xingchen T.; Balsam, William; Chen, Jun; Ji, Junfeng

2018-03-01

The East Asian summer monsoon (EASM) is an important component of the global climate system. A better understanding of EASM rainfall variability in the past can help constrain climate models and better predict the response of EASM to ongoing global warming. The warm early Pleistocene, a potential analog of future climate, is an important period to study EASM dynamics. However, existing monsoon proxies for reconstruction of EASM rainfall during the early Pleistocene fail to disentangle monsoon rainfall changes from temperature variations, complicating the comparison of these monsoon records with climate models. Here, we present three 2.6 million-year-long EASM rainfall records from the Chinese Loess Plateau (CLP) based on carbonate dissolution, a novel proxy for rainfall intensity. These records show that the interglacial rainfall on the CLP was lower during the early Pleistocene and then gradually increased with global cooling during the middle and late Pleistocene. These results are contrary to previous suggestions that a warmer climate leads to higher monsoon rainfall on tectonic timescales. We propose that the lower interglacial EASM rainfall during the early Pleistocene was caused by reduced sea surface temperature gradients across the equatorial Pacific, providing a testable hypothesis for climate models.

Nonlinear Meridional Moisture Advection and the ENSO-Southern China Rainfall Teleconnection

NASA Astrophysics Data System (ADS)

Wang, Qiang; Cai, Wenju; Zeng, Lili; Wang, Dongxiao

2018-05-01

In the boreal cooler months of 2015, southern China (SC) experienced the largest rainfall since 1950, exceeding 4 times the standard deviation of SC rainfall. Although an El Niño typically induces a positive SC rainfall anomaly during these months, the unprecedented rainfall increase cannot be explained by the strong El Niño of 2015/2016, and the dynamics is unclear. Here we show that a nonlinear meridional moisture advection contributes substantially to the unprecedented rainfall increase. During cooler months of 2015, the meridional flow anomaly over the South China Sea region, which acts on an El Niño-induced anomalous meridional moisture gradient, is particularly large and is supported by an anomalous zonal sea surface temperature gradient over the northwestern Pacific, which recorded its largest value in 2015 since 1950. Our study highlights, for the first time, the importance of the nonlinear process associated with the combined impact of a regional sea surface temperature gradient and large-scale El Niño anomalies in forcing El Niño rainfall teleconnection.

Climate variability, vulnerability, and coping mechanism in Alaknanda catchment, Central Himalaya, India.

PubMed

Kumar, Kireet; Joshi, Sneh; Joshi, Varun

2008-06-01

A study was carried out to discover trends in the rainfall and temperature pattern of the Alaknanda catchment in the Central Himalaya. Data on the annual rainfall, monsoon rainfall for the last decade, and average annual temperatures over the last few decades were analyzed. Nonparametric methods (Mann-Kendall and Sen's method) were employed to identify trends. The Mann-Kendall test shows a decline in rainfall and rise in temperature, and these trends were found to be statistically significant at the 95% confidence level for both transects. Sen's method also confirms this trend. This aspect has to be considered seriously for the simple reason that if the same trend continues in the future, more chances of drought are expected. The impact of climate change has been well perceived by the people of the catchment, and a coping mechanism has been developed at the local level.

On the Characterization of Rainfall Associated with U.S. Landfalling North Atlantic Tropical Cyclones Based on Satellite Data and Numerical Weather Prediction Outputs

NASA Astrophysics Data System (ADS)

Luitel, B. N.; Villarini, G.; Vecchi, G. A.

2014-12-01

When we talk about tropical cyclones (TCs), the first things that come to mind are strong winds and storm surge affecting the coastal areas. However, according to the Federal Emergency Management Agency (FEMA) 59% of the deaths caused by TCs since 1970 is due to fresh water flooding. Heavy rainfall associated with TCs accounts for 13% of heavy rainfall events nationwide for the June-October months, with this percentage being much higher if the focus is on the eastern and southern United States. This study focuses on the evaluation of precipitation associated with the North Atlantic TCs that affected the continental United States over the period 2007 - 2012. We evaluate the rainfall associated with these TCs using four satellite based rainfall products: Tropical Rainfall Measuring Mission - Multi-satellite Precipitation Analysis (TMPA; both real-time and research version); Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN); Climate Prediction Center (CPC) MORPHing technique (CMORPH). As a reference data we use gridded rainfall provided by CPC (Daily US Unified Gauge-Based Analysis of Precipitation). Rainfall fields from each of these satellite products are compared to the reference data, providing valuable information about the realism of these products in reproducing the rainfall associated with TCs affecting the continental United States. In addition to the satellite products, we evaluate the forecasted rainfall produced by five state-of-the-art numerical weather prediction (NWP) models: European Centre for Medium-Range Weather Forecasts (ECMWF), UK Met Office (UKMO), National Centers for Environmental Prediction (NCEP), China Meteorological Administration (CMA), and Canadian Meteorological Center (CMC). The skill of these models in reproducing TC rainfall is quantified for different lead times, and discussed in light of the performance of the satellite products.

Effects of trade-wind strength and direction on the leeside circulations and rainfall of the island of Hawaii

Treesearch

Yang Yang; Yi-Leng Chen; Francis M. Fujioka

2009-01-01

The leeside circulations and weather of the island of Hawaii were studied from the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) land surface model simulations for eight strong (∼7.9 m s−1) and eight weak (∼5.2 m s−1) trade-wind days and for five days with southeasterly trades (∼7.1 m s

Mesoscale convective systems and nocturnal rainfall over the West African Sahel: role of the Inter-tropical front

NASA Astrophysics Data System (ADS)

Vizy, Edward K.; Cook, Kerry H.

2018-01-01

A convection-permitting regional model simulation for August 2006 and observations are evaluated to better understand the diurnal cycle of precipitation over the Sahel. In particular, reasons for a nocturnal rainfall maximum over parts of the Sahel during the height of the West African monsoon are investigated. A relationship between mesoscale convective system (MCS) activity and inter-tropical front (ITF)/dryline dynamics is revealed. Over 90% of the Sahel nocturnal rainfall derives from propagating MCSs that have been associated with topography in earlier studies. In contrast, in this case study, 70-90% of the nocturnal rainfall over the southern Sahel (11°N-14°N) west of 15°E is associated with MCSs that originate less than 1000 km upstream (to the north and east) in the afternoon, in a region largely devoid of significant orography. This MCS development occurs in association with the Sahel ITF, combined with atmospheric pre-conditioning. Daytime surface heating generates turbulent mixing that promotes planetary boundary layer (PBL) growth accompanied by a low-level reversal in the meridional flow. This enhances wind convergence in the low-level moist layer within 2°-3° of latitude of the equatorward side of the ITF. MCSs tend to form when this vertical mixing extends to the level of free convection and is accompanied by a mid-tropospheric African easterly wave disturbance to the east. This synoptic disturbance enhances the vertical wind shear and atmospheric instability over the genesis location. These results are found to be robust across the region.

Hydrodynamic Modeling of Diego Garcia Lagoon

DTIC Science & Technology

2014-08-01

relative humidity, rainfall rate (m/s), evapotranspiration rate (m/s), net solar shortwave radiation (J/m2/s), cloud cover, wind speed (m/s), and... Evapotranspiration estimates were made using a version of the Modified Penman Equation (CIMIS, 2014). Solar radiation measurements were obtained from

Modulation of SSM/I microwave soil radiances by rainfall

NASA Technical Reports Server (NTRS)

Heymsfield, Gerald M.; Fulton, Richard

1992-01-01

The feasibility of using SSM/I satellite data for estimating the soil moisture content was investigated by correlating the rainfall and soil moisture data with values of the SSM/I microwave brightness temperature obtained for the lower Great Plains in the United States during 1987. It was found that the areas of lowest brightness temperatures coincided with regions of bare soil which had received significant rainfall. The time-history plots of the brightness temperature and the antecedent precipitation index during an extremely large rain event indicated a slow recovery period (about 15 days) back to the dry soil state. However, regions covered with vegetation showed smaller temperature drops and much weaker correlation with rain events, questioning the feasibility of using SSM/I measurements for estimations of soil moisture in regions containing vegetation-covered soil.

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.

Environmental and internal controls of tropical cyclone intensity change

NASA Astrophysics Data System (ADS)

Desflots, Melicie

Tropical cyclone (TC) intensity change is governed by internal dynamics and environmental conditions. This study aims to gain a better understanding of the physical mechanisms responsible for TC intensity changes with a particular focus to those related to the vertical wind shear and the impact of sea spray on the hurricane boundary layer, by using high resolution, full physics numerical simulations. The coupled model consists of three components: the non-hydrostatic, 5th generation Pennsylvania State University-NCAR mesoscale model (MM5), the NOAA/NCEP WAVEWATCH III (WW3) ocean surface wave model, and the WHOI three-dimensional upper ocean circulation model (3DPWP). Sea spray parameterizations (SSP) were developed at NOAA/ESRL, modified by the author and introduced in uncoupled and coupled simulations. The 0.5 km grid resolution MM5 simulation of Hurricane Lili showed a rapid intensification associated with a contracting eyewall. Hurricane Lili weakened in a 5-10 m s-1 vertical wind shear environment. The simulated storm experienced wind shear direction normal to the storm motion, which produced a strong wavenumber one rainfall asymmetry in the downshear-left quadrant of the storm. The increasing vertical wind shear induced a vertical tilt of the vortex with a time lag of 5-6 hours after the wavenumber one rainfall asymmetry was first observed in the model simulation. Other factors controlling intensity and intensity change in tropical cyclones are the air-sea fluxes. Recent studies have shown that the momentum exchange coefficient levels off at high wind speed. However, the behavior of the exchange coefficient for enthalpy flux in high wind and the potential impact of sea spray on it is still uncertain. The current SSP are closely tied to wind speed and overestimate the mediated heat fluxes by sea spray in the hurricane boundary layer. As the sea spray generation depends on wind speed and the variable wave state, a new SSP based on the surface wave energy dissipation (WED) is introduced in the coupled model. In the coupled simulations, the WED is used to quantify the amount of wave breaking related to the generation of spray. The SSP coupled to the waves offers an improvement compared to the wind dependent SSP.

Temperature and rainfall interact to control carbon cycling in tropical forests.

PubMed

Taylor, Philip G; Cleveland, Cory C; Wieder, William R; Sullivan, Benjamin W; Doughty, Christopher E; Dobrowski, Solomon Z; Townsend, Alan R

2017-06-01

Tropical forests dominate global terrestrial carbon (C) exchange, and recent droughts in the Amazon Basin have contributed to short-term declines in terrestrial carbon dioxide uptake and storage. However, the effects of longer-term climate variability on tropical forest carbon dynamics are still not well understood. We synthesised field data from more than 150 tropical forest sites to explore how climate regulates tropical forest aboveground net primary productivity (ANPP) and organic matter decomposition, and combined those data with two existing databases to explore climate - C relationships globally. While previous analyses have focused on the effects of either temperature or rainfall on ANPP, our results highlight the importance of interactions between temperature and rainfall on the C cycle. In cool forests (< 20 °C), high rainfall slowed rates of C cycling, but in warm tropical forests (> 20 °C) it consistently enhanced both ANPP and decomposition. At the global scale, our analysis showed an increase in ANPP with rainfall in relatively warm sites, inconsistent with declines in ANPP with rainfall reported previously. Overall, our results alter our understanding of climate - C cycle relationships, with high precipitation accelerating rates of C exchange with the atmosphere in the most productive biome on earth. © 2017 John Wiley & Sons Ltd/CNRS.

Hydrological and nutrient fluxes in the soil-atmosphere interface in Brazilian semiarid

NASA Astrophysics Data System (ADS)

Leal, Karinne; Borma, Laura; Forti, Cristina

2014-05-01

Semiarids are water stress regions caused by the association of high potential evapotranspiration, high temperatures (in summer) and generally low rainfall. Although unfavorable climatic conditions, semiarid regions represent about 14% global population and has been suffering land transformation, such as replacement by pastures and croplands. Crescent demand for agricultural and forests products in Brazilian semiarid has taken Caatinga deforestations, typical vegetation of that area that covers about 10% of Brazilian territory, with consequences in hydrology and biogeochemistry. The effect of these disruptions are poorly understood. The aim of this research is to characterize the differences in transfers of water and nutrients, in soil-atmosphere interface, between a typical Caatinga vegetation and pasture. Two field campaigns were made to sample and measure the water from rainfall, throughfall, stemflow, runoff and soil water. The collections were conducted during the rainy season, extended from April to August in 2012 and 2013, in São João, a county in the semiarid region of Pernambuco State, in the northeast of Brazil. The samples are being analyzed in order to determine their major cations and anions concentrations, total dissolved carbon (TDC), total organic carbon (TOC), total nitrogen (TN), alkalinity and pH. The observed precipitation represented about 40% and 50% of the historical average precipitation, in 2012 and 2013, respectively. This observations highlight the severe drought experienced in the region, mainly in the first year of sampling. The throughfall represented about 35% of the rainfall in 2012, and about 25% in 2013. In semiarid vegetations the average throughfall is about 49%, with variation coefficient of ±32%, so the observed data are consistent with those reported in the literature. These observations suggests that in drier years the vegetation holds more moisture than in wetter years. However, these data must be correlated with others parameters that influence the relationship between rainfall and troughfall, such as intensity and duration of the rain, wind speed and air humidity before the rainfall. The runoff was an order of magnitude lower in 2012 than in 2013. The chemical analyzes are still being processed. Key-words: Caatinga, carbon, nitrogen, land transformation.

Understanding the Sensitivity of a GCM Simulation of Amazonian Deforestation to the Specification of Vegetation and Soil Characteristics.

NASA Astrophysics Data System (ADS)

Lean, J.; Rowntree, P. R.

1997-06-01

The experiment reported on here presents a realistic portrayal of Amazonian deforestation that uses measurements of vegetation characteristics, taken as part of the Anglo-Brazilian Amazonian Climate Observation Study field campaigns, to define the forest and replacement pasture vegetation in the Hadley Centre GCM. The duration of the main experiment (10 yr) leads to greater confidence in assessing regional changes than in previous shorter experiments.Complete removal of the Amazonian forest produced area-mean changes that resemble earlier experiments with decreases in evaporation of 0.76 mm day1 (18%) and rainfall of 0.27 mm day1 (4%) and a rise in surface temperature of 2.3°C. However, the relative changes in magnitude indicate that increased moisture convergence partly compensates for the reduced evaporation, in contrast to many previous deforestation experiments. Results also showed large regional variations in the change in annual mean rainfall over South America, with widespread decreases over most of the deforested area and increases near the Andes.A better understanding of the mechanisms responsible for the final deforested climate has been gained by carrying out additional experiments that examine the response to separate changes in roughness and albedo. Increased albedo resulted in widespread significant decreases in rainfall due to less moisture convergence and ascent. The response to reduced roughness is more complex but of comparable importance; in this experiment it was dominated by an increase in low-level wind speeds resulting in decreased moisture convergence and rainfall near the upwind edge of the area and the opposite near the downwind boundary where the increased flow meets the Andes.In the standard deforestation scenario all vegetation parameters were modified together with one soil parameter-the maximum infiltration rate, which is reduced to represent the observed compaction of soil following deforestation. Results from a further experiment, in which the maximum infiltration rate was left unchanged, showed much smaller reductions in evaporation of 0.3 mm day1 (7%) and indicated that the predicted regional changes in rainfall and evaporation were very sensitive to this parameter.

Effects of some air pollutants and meteorological conditions on airborne algae and protozoa

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

Smith, P.E.

1973-10-01

The effects of meteorological conditions and specific air pollutants on the viability of airborne algae and protozoa were investigated. Such investigations will be of interest to medical researchers because these organisms are the source of many allergies. The three air pollutants that were continuously measured and recorded were sulfur, hydrocarbons, and particulate matter. During the experiment, 25 different species of algae and 19 species of protozoa were collected from the atmosphere and cultured at the Westinghouse environmental Station Laboratory in Raleigh, North Carolina. The algae and protozoa were collected over a one-year period (Jan-Dec 1971) by using a sequential samplermore » that moved air through a membrane filter at the rate of 15 ft/sup 3//hr. Every two hours a new filter was sequentially moved in to replace the old one. The results indicated a relationship between wind speed, wind direction, temperature, dewpoint, particulate matter, barometric pressure, and rainfall to the percent frequency of positive culture tubes and number of cell/ft/sup 3/ of air. Further studies are necessary to determine the interrelationships between the physical and chemical character of various air masses and their effect on the survival of algae and protozoa.« less

Oceanic link between abrupt changes in the North Atlantic Ocean and the African monsoon

NASA Astrophysics Data System (ADS)

Chang, Ping; Zhang, Rong; Hazeleger, Wilco; Wen, Caihong; Wan, Xiuquan; Ji, Link; Haarsma, Reindert J.; Breugem, Wim-Paul; Seidel, Howard

2008-07-01

Abrupt changes in the African monsoon can have pronounced socioeconomic impacts on many West African countries. Evidence for both prolonged humid periods and monsoon failures have been identified throughout the late Pleistocene and early Holocene epochs. In particular, drought conditions in West Africa have occurred during periods of reduced North Atlantic thermohaline circulation, such as the Younger Dryas cold event. Here, we use an ocean-atmosphere general circulation model to examine the link between oceanographic changes in the North Atlantic Ocean and changes in the strength of the African monsoon. Our simulations show that when North Atlantic thermohaline circulation is substantially weakened, the flow of the subsurface North Brazil Current reverses. This leads to decreased upper tropical ocean stratification and warmer sea surface temperatures in the equatorial South Atlantic Ocean, and consequently reduces African summer monsoonal winds and rainfall over West Africa. This mechanism is in agreement with reconstructions of past climate. We therefore suggest that the interaction between thermohaline circulation in the North Atlantic Ocean and wind-driven currents in the tropical Atlantic Ocean contributes to the rapidity of African monsoon transitions during abrupt climate change events.

Year-round breeding equatorial Larks from three climatically-distinct populations do not use rainfall, temperature or invertebrate biomass to time reproduction

PubMed Central

Ndithia, Henry K.; Matson, Kevin D.; Versteegh, Maaike A.; Muchai, Muchane; Tieleman, B. Irene

2017-01-01

Timing of reproduction in birds is important for reproductive success and is known to depend on environmental cues such as day length and food availability. However, in equatorial regions, where day length is nearly constant, other factors such as rainfall and temperature are thought to determine timing of reproduction. Rainfall can vary at small spatial and temporal scales, providing a highly fluctuating and unpredictable environmental cue. In this study we investigated the extent to which spatio-temporal variation in environmental conditions can explain the timing of breeding of Red-capped Lark, Calandrella cinerea, a species that is capable of reproducing during every month of the year in our equatorial east African study locations. For 39 months in three climatically-distinct locations, we monitored nesting activities, sampled ground and flying invertebrates, and quantified rainfall, maximum (Tmax) and minimum (Tmin) temperatures. Among locations we found that lower rainfall and higher temperatures did not coincide with lower invertebrate biomasses and decreased nesting activities, as predicted. Within locations, we found that rainfall, Tmax, and Tmin varied unpredictably among months and years. The only consistent annually recurring observations in all locations were that January and February had low rainfall, high Tmax, and low Tmin. Ground and flying invertebrate biomasses varied unpredictably among months and years, but invertebrates were captured in all months in all locations. Red-capped Larks bred in all calendar months overall but not in every month in every year in every location. Using model selection, we found no clear support for any relationship between the environmental variables and breeding in any of the three locations. Contrary to popular understanding, this study suggests that rainfall and invertebrate biomass as proxy for food do not influence breeding in equatorial Larks. Instead, we propose that factors such as nest predation, female protein reserves, and competition are more important in environments where weather and food meet minimum requirements for breeding during most of the year. PMID:28419105

Occurrence of Landslides during the Approach of Tropical Cyclone Juliette (2001) to Baja California Sur, Mexico

NASA Astrophysics Data System (ADS)

Antinao, J.; Farfan, L.

2012-12-01

The approach of Tropical Cyclone Juliette to the Baja California Peninsula in September 2001 triggered at least 419 landslides. Most of the landslides were shallow slips and debris slides, of limited areal extent, which were converted rapidly into debris flows to be exported quickly out of the mountain areas towards the lowlands. Main factors affecting landslide occurrence were total storm rainfall and intensity, aspect, geology and vegetation association. Two processes can be distinguished as initiating slope failure. The first process is linked to failures in concave topography, where accumulation of rainfall from exposed bedrock slopes generated excess overland flow that aggregated to generate a 'fire hose' effect on the base of slopes, mobilizing regolith. A second process involved a combination of wind and excess overland flow developed in the more convex or planar upper slopes, where heterogeneous regolith has formed in time following successional changes in vegetation associations along the oak-dry tropical forest ecotone. In this area, wind uprooted trees that dislodged large regolith and bedrock blocks, priming hillslopes for further runoff concentration. From the analysis of historical information, an estimative threshold curve for triggering landslides in this region is sketched. It was also determined that storms like Juliette approach the southern peninsula on average once every 100 years. Denudation estimates are in the higher end of the spectrum for a tectonically passive margin. These estimates should be considered when taking decisions regarding management of water resources in this area through damming of streams. The results emphasize the need for a more detailed representation of the spatial distribution of the rainfall and winds for this mountainous region frequently affected by the passage of tropical cyclones.

The role of potential vorticity anomalies in the Somali Jet on Indian Summer Monsoon Intraseasonal Variability

NASA Astrophysics Data System (ADS)

Rai, P.; Joshi, M.; Dimri, A. P.; Turner, A. G.

2017-08-01

The climate of the Indian subcontinent is dominated by rainfall arising from the Indian summer monsoon (ISM) during June to September. Intraseasonal variability during the monsoon is characterized by periods of heavy rainfall interspersed by drier periods, known as active and break events respectively. Understanding and predicting such events is of vital importance for forecasting human impacts such as water resources. The Somali Jet is a key regional feature of the monsoon circulation. In the present study, we find that the spatial structure of Somali Jet potential vorticity (PV) anomalies varies considerably during active and break periods. Analysis of these anomalies shows a mechanism whereby sea surface temperature (SST) anomalies propagate north/northwestwards through the Arabian Sea, caused by a positive feedback loop joining anomalies in SST, convection, modification of PV by diabatic heating and mixing in the atmospheric boundary layer, wind-stress curl, and ocean upwelling processes. The feedback mechanism is consistent with observed variability in the coupled ocean-atmosphere system on timescales of approximately 20 days. This research suggests that better understanding and prediction of monsoon intraseasonal variability in the South Asian monsoon may be gained by analysis of the day-to-day dynamical evolution of PV in the Somali Jet.

The role of potential vorticity anomalies in the Somali Jet on Indian Summer Monsoon Intraseasonal Variability

NASA Astrophysics Data System (ADS)

Rai, P.; Joshi, M.; Dimri, A. P.; Turner, A. G.

2018-06-01

The climate of the Indian subcontinent is dominated by rainfall arising from the Indian summer monsoon (ISM) during June to September. Intraseasonal variability during the monsoon is characterized by periods of heavy rainfall interspersed by drier periods, known as active and break events respectively. Understanding and predicting such events is of vital importance for forecasting human impacts such as water resources. The Somali Jet is a key regional feature of the monsoon circulation. In the present study, we find that the spatial structure of Somali Jet potential vorticity (PV) anomalies varies considerably during active and break periods. Analysis of these anomalies shows a mechanism whereby sea surface temperature (SST) anomalies propagate north/northwestwards through the Arabian Sea, caused by a positive feedback loop joining anomalies in SST, convection, modification of PV by diabatic heating and mixing in the atmospheric boundary layer, wind-stress curl, and ocean upwelling processes. The feedback mechanism is consistent with observed variability in the coupled ocean-atmosphere system on timescales of approximately 20 days. This research suggests that better understanding and prediction of monsoon intraseasonal variability in the South Asian monsoon may be gained by analysis of the day-to-day dynamical evolution of PV in the Somali Jet.

Temperature and rainfall are related to fertility rate after spring artificial insemination in small ruminants.

PubMed

Abecia, J A; Arrébola, F; Macías, A; Laviña, A; González-Casquet, O; Benítez, F; Palacios, C

2016-10-01

A total number of 1092 artificial inseminations (AIs) performed from March to May were documented over four consecutive years on 10 Payoya goat farms (36° N) and 19,392 AIs on 102 Rasa Aragonesa sheep farms (41° N) over 10 years. Mean, maximum, and minimum ambient temperatures, mean relative humidity, mean solar radiation, and total rainfall on each insemination day were recorded. Overall, fertility rates were 58 % in goats and 45 % in sheep. The fertility rates of the highest and lowest deciles of each of the meteorological variables indicated that temperature and rainfall had a significant effect on fertility in goats. Specifically, inseminations that were performed when mean (68 %), maximum (68 %), and minimum (66 %) temperatures were in the highest decile, and rainfall was in the lowest decile (59 %), had a significantly (P < 0.0001) higher proportion of does that became pregnant than did the ewes in the lowest decile (56, 54, 58, and 49 %, respectively). In sheep, the fertility rates of the highest decile of mean (62 %), maximum (62 %), and minimum (52 %) temperature, RH (52 %), THI (53 %), and rainfall (45 %) were significantly higher (P < 0.0001) than were the fertility rates among ewes in the lowest decile (46, 45, 45, 45, 46, and 43 %, respectively). In conclusion, weather was related to fertility in small ruminants after AI in spring. It remains to be determined whether scheduling the dates of insemination based on forecasted temperatures can improve the success of AI in goats and sheep.

Investigating the impact of land-use land-cover change on Indian summer monsoon daily rainfall and temperature during 1951–2005 using a regional climate model

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

Halder, Subhadeep; Saha, Subodh K.; Dirmeyer, Paul A.

Daily moderate rainfall events, which constitute a major portion of seasonal summer monsoon rainfall over central India, have decreased significantly during the period 1951 through 2005. On the other hand, mean and extreme near-surface daily temperature during the monsoon season have increased by a maximum of 1–1.5 °C. Using simulations made with a high-resolution regional climate model (RegCM4) and prescribed land cover of years 1950 and 2005, it is demonstrated that part of the changes in moderate rainfall events and temperature have been caused by land-use/land-cover change (LULCC), which is mostly anthropogenic. Model simulations show that the increase in seasonal mean and extreme temperature over centralmore » India coincides with the region of decrease in forest and increase in crop cover. Our results also show that LULCC alone causes warming in the extremes of daily mean and maximum temperatures by a maximum of 1–1.2 °C, which is comparable with the observed increasing trend in the extremes. Decrease in forest cover and simultaneous increase in crops not only reduces the evapotranspiration over land and large-scale convective instability, but also contributes toward decrease in moisture convergence through reduced surface roughness. These factors act together in reducing significantly the moderate rainfall events and the amount of rainfall in that category over central India. Additionally, the model simulations are repeated by removing the warming trend in sea surface temperatures over the Indian Ocean. As a result, enhanced warming at the surface and greater decrease in moderate rainfall events over central India compared to the earlier set of simulations are noticed. Results from these additional experiments corroborate our initial findings and confirm the contribution of LULCC in the decrease in moderate rainfall events and increase in daily mean and extreme temperature over India. Therefore, this study demonstrates the important implications of LULCC over India during the monsoon season. Although, the regional climate model helps in better resolving land–atmosphere feedbacks over the Indian region, the inferences do depend on the fidelity of the model in capturing the features of Indian monsoon realistically. Lastly, it is proposed that similar studies using a suite of climate models will further enrich our understanding about the role of LULCC in the Indian monsoon climate.« less

Investigating the impact of land-use land-cover change on Indian summer monsoon daily rainfall and temperature during 1951–2005 using a regional climate model

DOE PAGES

Halder, Subhadeep; Saha, Subodh K.; Dirmeyer, Paul A.; ...

2016-05-10

Daily moderate rainfall events, which constitute a major portion of seasonal summer monsoon rainfall over central India, have decreased significantly during the period 1951 through 2005. On the other hand, mean and extreme near-surface daily temperature during the monsoon season have increased by a maximum of 1–1.5 °C. Using simulations made with a high-resolution regional climate model (RegCM4) and prescribed land cover of years 1950 and 2005, it is demonstrated that part of the changes in moderate rainfall events and temperature have been caused by land-use/land-cover change (LULCC), which is mostly anthropogenic. Model simulations show that the increase in seasonal mean and extreme temperature over centralmore » India coincides with the region of decrease in forest and increase in crop cover. Our results also show that LULCC alone causes warming in the extremes of daily mean and maximum temperatures by a maximum of 1–1.2 °C, which is comparable with the observed increasing trend in the extremes. Decrease in forest cover and simultaneous increase in crops not only reduces the evapotranspiration over land and large-scale convective instability, but also contributes toward decrease in moisture convergence through reduced surface roughness. These factors act together in reducing significantly the moderate rainfall events and the amount of rainfall in that category over central India. Additionally, the model simulations are repeated by removing the warming trend in sea surface temperatures over the Indian Ocean. As a result, enhanced warming at the surface and greater decrease in moderate rainfall events over central India compared to the earlier set of simulations are noticed. Results from these additional experiments corroborate our initial findings and confirm the contribution of LULCC in the decrease in moderate rainfall events and increase in daily mean and extreme temperature over India. Therefore, this study demonstrates the important implications of LULCC over India during the monsoon season. Although, the regional climate model helps in better resolving land–atmosphere feedbacks over the Indian region, the inferences do depend on the fidelity of the model in capturing the features of Indian monsoon realistically. Lastly, it is proposed that similar studies using a suite of climate models will further enrich our understanding about the role of LULCC in the Indian monsoon climate.« less

An Investigation of the Influence of Urban Areas on Rainfall Using a Cloud-Mesoscale Model and the TRMM Satellite

NASA Technical Reports Server (NTRS)

Shepherd, J. Marshall; Starr, David O'C (Technical Monitor)

2001-01-01

A recent paper by Shepherd and Pierce (conditionally accepted to Journal of Applied Meteorology) used rainfall data from the Precipitation Radar on NASA's Tropical Rainfall Measuring Mission's (TRMM) satellite to identify warm season rainfall anomalies downwind of major urban areas. A convective-mesoscale model with extensive land-surface processes is employed to (a) determine if an urban heat island (UHI) thermal perturbation can induce a dynamic response to affect rainfall processes and (b) quantify the impact of the following three factors on the evolution of rainfall: (1) urban surface roughness, (2) magnitude of the UHI temperature anomaly, and (3) physical size of the UHI temperature anomaly. The sensitivity experiments are achieved by inserting a slab of land with urban properties (e.g. roughness length, albedo, thermal character) within a rural surface environment and varying the appropriate lower boundary condition parameters. Early analysis suggests that urban surface roughness (through turbulence and low-level convergence) may control timing and initial location of UHI-induced convection. The magnitude of the heat island appears to be closely linked to the total rainfall amount with minor impact on timing and location. The physical size of the city may predominantly impact on the location of UHI-induced rainfall anomaly. The UHI factor parameter space will be thoroughly investigated with respect to their effects on rainfall amount, location, and timing. This study extends prior numerical investigations of the impact of urban surfaces on meteorological processes, particularly rainfall development. The work also contains several novel aspects, including the application of a high-resolution (less than I km) cloud-mesoscale model to investigate urban-induce rainfall process; investigation of thermal magnitude of the UHI on rainfall process; and investigation of UHI physical size on rainfall processes.

Hydrological and Dynamical Characteristics of Summertime Droughts over U.S. Great Plains.

NASA Astrophysics Data System (ADS)

Chang, Fong-Chiau; Smith, Eric A.

2001-05-01

A drought pattern and its time evolution over the U.S. Great Plains are investigated from time series of climate divisional monthly mean surface air temperature and total precipitation anomalies. The spatial pattern consists of correlated occurrences of high (low) surface air temperature and deficit (excess) rainfall. The center of maximum amplitude in rain fluctuation is around Kansas City; that of temperature is over South Dakota. Internal consistency between temperature and precipitation variability is the salient feature of the drought pattern. A drought index is used to quantify drought severity for the period 1895-1996. The 12 severest drought months (in order) during this period are June 1933, June 1988, July 1936, August 1983, July 1934, July 1901, June 1931, August 1947, July 1930, June 1936, July 1954, and August 1936. Hydrological conditions are examined using National Centers for Environmental Prediction (NCEP) reanalysis precipitable water (PW) and monthly surface observations from Kansas City, Missouri, and Bismarck, North Dakota, near the drought centers. This analysis explains why droughts exhibit negative surface relative humidity anomalies accompanied by larger than normal monthly mean daily temperature ranges and why maximum PWs are confined to a strip of about 10° longitude from New Mexico and Arizona into the Dakotas and Minnesota.Dynamical conditions are examined using NCEP reanalysis sea level pressures and 500- and 200-mb geopotential heights. The analysis indicates a midtroposphere wave train with positive centers situated over the North Pacific, North America, and the North Atlantic, with negative centers in the southeastern Gulf of Alaska and Davis Strait. Above-normal sea level pressures over New Mexico, the North Atlantic, and the subtropical Pacific along with below-normal sea level pressures over the Gulf of Alaska eastward to Canada, Davis Strait, and Greenland are present during drought periods. The most prominent feature is the strong anticyclone over central North America.On a regional scale, midtropospheric westerly winds are weakened (or become easterly) south of a thermal heat low centered in South Dakota during drought episodes because of the north-south temperature reversal perturbation. The associated westward displaced Bermuda high leads to enhanced low-level warm flow into the Dakotas, thus helping to maintain the reversal in the meridional temperature gradient and the concomitant thermal wind reversal. Enhanced moisture transport from the Gulf of California into the western plains (part of the Great Basin monsoon process) results from the large-scale perturbation pressure pattern. Middle-upper level convergence maintains the water vapor strip east of the Rocky Mountains, while the Mississippi valley undergoes moisture cutoff from both this process and the westward shift in the Bermuda high. The strip of maximum PW then undergoes enhanced solar and infrared absorption that feeds back on the thermal heat low. Surface air temperatures warm while sinking motion balances middle-upper level radiative cooling around the Kansas City area. This is the dynamical coupling that leads to reduced surface relative humidities. The centers of high surface air temperature and deficit rainfall are dynamically consistent with patterns in geopotential heights, vertical velocities, and water vapor amounts.

Simulation of a Severe Autumn/Winter Drought in Eastern China by Regional Atmospheric Modeling System(RAMS)

NASA Astrophysics Data System (ADS)

Meng, Chunchun; Ma, Yaoming

2016-04-01

Compared with European Centre for Medium-Range Weather Forecasts (ERA-interim) Reanalysis data and Global Summary Of Day (GSOD) observation data, the outcomes from RAMS of the 2008/2009 severe autumn/winter drought in eastern china are analyzed in this study. The reanalysis data showed that most parts of north China are controlled by northwest wind which was accompanied by cold air, the warm and moist air from South Sea is so weak to meet with cold air, therefore forming a circulation which is unfavorable for the formation of precipitation over Eastern China. RAMS performs very well over the simulation of this atmospheric circulation, so do the rainfall and air temperature over China and where the drought occurred. Meanwhile, the simulation of the time series of precipitation and temperature behaves excellent, the square of correlation coefficient between simulations and observations reached above 0.8. Although the performance of RAMS on this drought simulation is fairly accurate, there is amount of research work to be continued to complete a more realistic simulation. KEY WORDS RAMS; severe drought; numerical simulation; atmospheric circulation; precipitation and air temperature

Rainfall-enhanced blooming in typhoon wakes

PubMed Central

Lin, Y.-C.; Oey, L.-Y.

2016-01-01

Strong phytoplankton blooming in tropical-cyclone (TC) wakes over the oligotrophic oceans potentially contributes to long-term changes in global biogeochemical cycles. Yet blooming has traditionally been discussed using anecdotal events and its biophysical mechanics remain poorly understood. Here we identify dominant blooming patterns using 16 years of ocean-color data in the wakes of 141 typhoons in western North Pacific. We observe right-side asymmetric blooming shortly after the storms, attributed previously to sub-mesoscale re-stratification, but thereafter a left-side asymmetry which coincides with the left-side preference in rainfall due to the large-scale wind shear. Biophysical model experiments and observations demonstrate that heavier rainfall freshens the near-surface water, leading to stronger stratification, decreased turbulence and enhanced blooming. Our results suggest that rainfall plays a previously unrecognized, critical role in TC-induced blooming, with potentially important implications for global biogeochemical cycles especially in view of the recent and projected increases in TC-intensity that harbingers stronger mixing and heavier rain under the storm. PMID:27545899

Rainfall-enhanced blooming in typhoon wakes.

PubMed

Lin, Y-C; Oey, L-Y

2016-08-22

Strong phytoplankton blooming in tropical-cyclone (TC) wakes over the oligotrophic oceans potentially contributes to long-term changes in global biogeochemical cycles. Yet blooming has traditionally been discussed using anecdotal events and its biophysical mechanics remain poorly understood. Here we identify dominant blooming patterns using 16 years of ocean-color data in the wakes of 141 typhoons in western North Pacific. We observe right-side asymmetric blooming shortly after the storms, attributed previously to sub-mesoscale re-stratification, but thereafter a left-side asymmetry which coincides with the left-side preference in rainfall due to the large-scale wind shear. Biophysical model experiments and observations demonstrate that heavier rainfall freshens the near-surface water, leading to stronger stratification, decreased turbulence and enhanced blooming. Our results suggest that rainfall plays a previously unrecognized, critical role in TC-induced blooming, with potentially important implications for global biogeochemical cycles especially in view of the recent and projected increases in TC-intensity that harbingers stronger mixing and heavier rain under the storm.

Rainfall-enhanced blooming in typhoon wakes

NASA Astrophysics Data System (ADS)

Lin, Y.-C.; Oey, L.-Y.

2016-08-01

Strong phytoplankton blooming in tropical-cyclone (TC) wakes over the oligotrophic oceans potentially contributes to long-term changes in global biogeochemical cycles. Yet blooming has traditionally been discussed using anecdotal events and its biophysical mechanics remain poorly understood. Here we identify dominant blooming patterns using 16 years of ocean-color data in the wakes of 141 typhoons in western North Pacific. We observe right-side asymmetric blooming shortly after the storms, attributed previously to sub-mesoscale re-stratification, but thereafter a left-side asymmetry which coincides with the left-side preference in rainfall due to the large-scale wind shear. Biophysical model experiments and observations demonstrate that heavier rainfall freshens the near-surface water, leading to stronger stratification, decreased turbulence and enhanced blooming. Our results suggest that rainfall plays a previously unrecognized, critical role in TC-induced blooming, with potentially important implications for global biogeochemical cycles especially in view of the recent and projected increases in TC-intensity that harbingers stronger mixing and heavier rain under the storm.

Rainfall-enhanced blooming in typhoon wakes

NASA Astrophysics Data System (ADS)

Lin, Y.; Oey, L. Y.

2016-12-01

Strong phytoplankton blooming in tropical-cyclone (TC) wakes over the oligotrophic oceans potentially contributes to long-term changes in global biogeochemical cycles. Yet blooming has traditionally been discussed using anecdotal events and its biophysical mechanics remain poorly understood. Here we identify dominant blooming patterns using 16 years of ocean-color data in the wakes of 141 typhoons in western North Pacific. We observe right-side asymmetric blooming shortly after the storms, attributed previously to sub-mesoscale re-stratification, but thereafter a left-side asymmetry which coincides with the left-side preference in rainfall due to the large-scale wind shear. Biophysical model experiments and observations demonstrate that heavier rainfall freshens the near-surface water, leading to stronger stratification, decreased turbulence and enhanced blooming. Our results suggest that rainfall plays a previously unrecognized, critical role in TC-induced blooming, with potentially important implications for global biogeochemical cycles especially in view of the recent and projected increases in TC-intensity that harbingers stronger mixing and heavier rain under the storm.

Northern Hemisphere Influence on the Position of the SPCZ During MIS3: a High Resolution Glacial Rainfall Record from a Niuean Speleothem

NASA Astrophysics Data System (ADS)

Sinclair, D.; Sherrell, R. M.; Tremaine, D. M.; Sweeney, J. R.; Rowe, H.; Wright, J. D.; Mortlock, R. A.; Hellstrom, J. C.; Cheng, H.; Min, A.; Edwards, R. L.

2017-12-01

Here we present a high-resolution glacial paleorainfall record from the heart of the South Pacific Convergence Zone (SPCZ) extracted from a stalagmite from the remote island of Niue (19°03'S 169°52'W). The record spans much of MIS3 (25-45 ka) and captures rapid rainfall changes associated with shifts in the SPCZ. It is clear that rapid climate shifts in the Northern Hemisphere have a strong influence on the SPCZ. All of the warm Dansgaard-Oeschger (`D-O') interstadials across this period are represented by rainfall increases, with D-O Events 9-11 particularly strongly represented. Since Niue lies south of the core of the SPCZ, this implies that rather than shifting northwards (as the ITCZ does), the SPCZ instead rotates clockwise in response to northern Hemisphere warming (analogous to a shift between modern El Nino and La Nina states). We propose that changes to surface ocean temperature gradients in the Eastern Pacific modulate the strength of the Wind Evaporation SST feedback, changing the size and westward penetration of the eastern Pacific dry zone, resulting in changes to the diagonality of the SPCZ. Our record also captures a response to strong northern Hemisphere cooling. The 25-45 ka record is bounded by large hiatuses (inferred dry conditions) coincident with cold Heinrich Stadials (HS) 2 and 5, while HS3 and HS4 are captured as distinct reductions in speleothem growth rate and proxy evidence for declining rainfall. This is consistent with a counter-clockwise rotation of the SPCZ during Northern cooling, supporting our proposed mechanism. Interestingly, our record also captures several other (non-Heinrich) cooling events, including a strong 500-year dry interval at 26ka that is seen in Chinese and Brazilian speleothems and coincides with a strong cooling over Asia (inferred from Greenland dust records). We note the (possibly coincidental) timing between this event and the Oruanui super-eruption at 25.6 ka.

Global Precipitation during the 1997-98 El Nino and Initiation of the 1998-99 La Nina

NASA Technical Reports Server (NTRS)

Curtis, Scott; Adler, Robert; Huffman, George; Nelkin, Eric; Bolvin, David

1999-01-01

The 1997-99 ENSO (El nino Southern Oscillation) cycle was very powerful, but also well observed. The best satellite rainfall estimates combined with gauge observations allow for a global analysis of precipitation anomalies accompanying the 1997-98 El Nino and initiation of the 1998-99 La Nina. For the period April 1997 to March 1998 the central to eastern Pacific, southeastern and western U.S., Argentina, eastern Africa, South China, eastern Russia, and North Atlantic were all more than two standard deviations wetter than normal. During the same year the Maritime Continent, eastern Indian Ocean, subtropical North Pacific, northeastern South America, and much of the mid- latitude southern oceans were more than two standard deviations drier than normal. An analysis of the evolution of the El Nino and accompanying precipitation anomalies revealed that a dry Maritime Continent led the formation of the El Nino SST (Sea Surface Temperature), while in the central Pacific, precipitation anomalies lagged the El Nino SST by a season. A rapid transition from El Nino to La Nina occurred in May 1998, but as early as October-November 1997 precipitation indices captured precursor changes in Pacific rainfall anomalies. Differences were found between observed and modeled [NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis] precipitation anomalies for 1997 and 98. In particular, the model had a bias towards positive precipitation anomalies and the magnitudes of the anomalies in the equatorial Pacific were small compared to the observations. Also, the evolution of the precipitation field, including the drying of the Maritime Continent and eastward progression of rainfall in the equatorial Pacific, was less pronounced for the model compared to the observations. One degree daily estimates of rainfall show clearly the MaddenJulian Oscillation and related westerly wind burst events over the Maritime Continent, which are key indicators for the onset of El Nino.

Analysis of rainfall and temperature time series to detect long-term climatic trends and variability over semi-arid Botswana

NASA Astrophysics Data System (ADS)

Byakatonda, Jimmy; Parida, B. P.; Kenabatho, Piet K.; Moalafhi, D. B.

2018-03-01

Arid and semi-arid environments have been identified with locations prone to impacts of climate variability and change. Investigating long-term trends is one way of tracing climate change impacts. This study investigates variability through annual and seasonal meteorological time series. Possible inhomogeneities and years of intervention are analysed using four absolute homogeneity tests. Trends in the climatic variables were determined using Mann-Kendall and Sen's Slope estimator statistics. Association of El Niño Southern Oscillation (ENSO) with local climate is also investigated through multivariate analysis. Results from the study show that rainfall time series are fully homogeneous with 78.6 and 50% of the stations for maximum and minimum temperature, respectively, showing homogeneity. Trends also indicate a general decrease of 5.8, 7.4 and 18.1% in annual, summer and winter rainfall, respectively. Warming trends are observed in annual and winter temperature at 0.3 and 1.5% for maximum temperature and 1.7 and 6.5% for minimum temperature, respectively. Rainfall reported a positive correlation with Southern Oscillation Index (SOI) and at the same time negative association with Sea Surface Temperatures (SSTs). Strong relationships between SSTs and maximum temperature are observed during the El Niño and La Niña years. These study findings could facilitate planning and management of agricultural and water resources in Botswana.

Rainfall simulation experiments: Influence of water temperature, water quality and plot design on soil erosion and runoff

NASA Astrophysics Data System (ADS)

Iserloh, Thomas; Pegoraro, Dominique; Schlösser, Angelika; Thesing, Hannah; Seeger, Manuel; Ries, Johannes B.

2015-04-01

Field rainfall simulators are designed to study soil erosion processes and provide urgently needed data for various geomorphological, hydrological and pedological issues. Due to the different conditions and technologies applied, there are several methodological aspects under review of the scientific community, particularly concerning design, procedures and conditions of measurement for infiltration, runoff and soil erosion. This study aims at contributing fundamental data for understanding rainfall simulations in depth by studying the effect of the following parameters on the measurement results: 1. Plot design - round or rectangular plot: Can we identify differences in amount of runoff and erosion? 2. Water quality: What is the influence of the water's salt load on interrill erosion and infiltration as measured by rainfall experiments? 3. Water temperature: How much are the results conditioned by the temperature of water, which is subject to changes due to environmental conditions during the experiments? Preliminary results show a moderate increase of soil erosion with the water's salt load while runoff stays almost on the same level. With increasing water temperature, runoff increases continuously. At very high temperatures, soil erosion is clearly increased. A first comparison between round and rectangular plot indicates the rectangular plot to be the most suitable plot shape, but ambiguous results make further research necessary. The analysis of these three factors concerning their influence on runoff and erosion shows that clear methodological standards are necessary in order to make rainfall simulation experiments comparable.

Real-time Monitoring of 2017 Hurricanes and Typhoons with Lightning

NASA Astrophysics Data System (ADS)

Solorzano, N. N.; Thomas, J. N.; Bracy, C.; Holzworth, R. H., II

2017-12-01

The 2017 Atlantic season had the highest number of major hurricanes since 2005. To tackle the demand of real-time tropical cyclone (TC) monitoring, our group has developed a unique "storm-following" satellite and ground-based lightning product known as WWLLN-TC (World Wide Lightning Location Network - Tropical Cyclones; http://wwlln.net/storms/). In the present study, we explore this tool and other datasets, combining lightning and microwave data to quantify areas of intense convection in 2017 TCs Harvey, Hato, Irma, Maria, Nate, Ophelia and others. For each storm, the temporal distribution of discharges outside and within the inner core is compared to the changes in TC intensity. The intensification processes, monitored in near real-time by WWLLN-TC, are quantified in terms of pressure and/or wind speed changes. A peak in lightning activity is often observed in the inner core of TCs before and during rapid weakening, such as in Hurricanes Irma and Maria and Typhoon Hato. The microwave frequencies investigated include the 37 to 183 GHz channels of the satellite sensors DMSP/SSMIS and GPM/GMI. We reconstruct brightness temperatures from lightning data, providing more detailed pictures of the evolution of TCs at moments when satellite passes are missing or incomplete. This study also compares lightning activity in the inner core with convective and environmental parameters. Examples of environmental parameters discussed are sea surface temperature, wind shear, and sea surface height anomalies. We conclude by considering possible implications of WWLLN-TC on forecasts of rapid intensity change and rainfall.

Direct measurement of the combined effects of lichen, rainfall, and temperature onsilicate weathering

USGS Publications Warehouse

Brady, P.V.; Dorn, R.I.; Brazel, A.J.; Clark, J.; Moore, R.B.; Glidewell, T.

1999-01-01

A key uncertainty in models of the global carbonate-silicate cycle and long-term climate is the way that silicates weather under different climatologic conditions, and in the presence or absence of organic activity. Digital imaging of basalts in Hawaii resolves the coupling between temperature, rainfall, and weathering in the presence and absence of lichens. Activation energies for abiotic dissolution of plagioclase (23.1 ?? 2.5 kcal/mol) and olivine (21.3 ?? 2.7 kcal/mol) are similar to those measured in the laboratory, and are roughly double those measured from samples taken underneath lichen. Abiotic weathering rates appear to be proportional to rainfall. Dissolution of plagioclase and olivine underneath lichen is far more sensitive to rainfall.

Assessing the Regional Frequency, Intensity, and Spatial Extent of Tropical Cyclone Rainfall

NASA Astrophysics Data System (ADS)

Bosma, C.; Wright, D.; Nguyen, P.

2017-12-01

While the strength of a hurricane is generally classified based on its wind speed, the unprecedented rainfall-driven flooding experienced in southeastern Texas during Hurricane Harvey clearly highlights the need for better understanding of the hazards associated with extreme rainfall from hurricanes and other tropical systems. In this study, we seek to develop a framework for describing the joint probabilistic and spatio-temporal properties of extreme rainfall from hurricanes and other tropical systems. Furthermore, we argue that commonly-used terminology - such as the "500-year storm" - fail to convey the true properties of tropical cyclone rainfall occurrences in the United States. To quantify the magnitude and spatial extent of these storms, a database consisting of hundreds of unique rainfall volumetric shapes (or "voxels") was created. Each voxel is a four-dimensional object, created by connecting, in both space and time, gridded rainfall observations from the daily, gauge-based NOAA CPC-Unified precipitation dataset. Individual voxels were then associated with concurrent tropical cyclone tracks from NOAA's HURDAT-2 archive, to create distinct representations of the rainfall associated with every Atlantic tropical system making landfall over (or passing near) the United States since 1948. Using these voxels, a series of threshold-excess extreme value models were created to estimate the recurrence intervals of extreme tropical cyclone rainfall, both nationally and locally, for single and multi-day timescales. This voxel database also allows for the "indexing" of past events, placing recent extremes - such as the 50+ inches of rain observed during Hurricane Harvey - into a national context and emphasizing how rainfall totals that are rare at the point scale may be more frequent from a regional perspective.

An Investigation of the Influence of Urban Areas on Rainfall Using the TRMM Satellite and a Cloud-Mesoscale Model

NASA Astrophysics Data System (ADS)

Shepherd, J.

2002-05-01

A recent paper by Shepherd et al. (in press at Journal of Applied Meteorology) used rainfall data from the Precipitation Radar on NASA's Tropical Rainfall Measuring Mission's (TRMM) satellite to identify warm season rainfall anomalies downwind of major urban areas. Data (PR) were employed to identify warm season rainfall (1998-2000) patterns around Atlanta, Montgomery, Nashville, San Antonio, Waco, and Dallas. Results are consistent with METROMEX studies of St. Louis almost two decades ago and with more recent studies near Atlanta. A convective-mesoscale model with extensive land-surface processes is currently being employed to (a) determine if an urban heat island (UHI) thermal perturbation can induce a dynamic response to affect rainfall processes and (b) quantify the impact of the following three factors on the evolution of rainfall: (1) urban surface roughness, (2) magnitude of the UHI temperature anomaly, and (3) physical size of the UHI temperature anomaly. The sensitivity experiments are achieved by inserting a slab of land with urban properties (e.g. roughness length, albedo, thermal character) within a rural surface environment and varying the appropriate lower boundary condition parameters. The study will discuss the feasibility of utilizing satellite-based rainfall estimates for examining rainfall modification by urban areas on global scales and over longer time periods. The talk also introduces very preliminary results from the modeling component of the study.

Bioengineering Technology to Control River Soil Erosion using Vetiver (Vetiveria Zizaniodes)

NASA Astrophysics Data System (ADS)

Sriwati, M.; Pallu, S.; Selintung, M.; Lopa, R.

2018-04-01

Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock or dissolved material from one location on the earth’s crust, and then transport it away to another location. Bioengineering is an attempt to maximise the use of vegetation components along riverbanks to cope with landslides and erosion of river cliffs and another riverbank damage. This study aims to analyze the bioengineering of Vetiver as a surface layer for soil erosion control using slope of 100, 200, and 300. This study is conducted with 3 variations of rain intensity (I), at 103 mm/hour, 107 mm/hour, and 130 mm/hour by using rainfall simulator tool. In addition, the USLE (Universal Soil Loss Equation) method is used in order to measure the rate of soil erosion. In this study, there are few USLE model parameters were used such as rainfall erosivity factor, soil erodibility factor, length-loss slope and stepness factor, cover management factor, and support practise factor. The results demonstrated that average of reduction of erosion rate using Vetiver, under 3 various rainfalls, namely rainfall intensity 103 mm/hr had reduced 84.971%, rainfall intensity 107 mm/hr had reduced 86.583 %, rainfall intensity 130 mm/hr had reduced 65.851%.

Analysis of climate change impact on rainfall pattern of Sambas district, West Kalimantan

NASA Astrophysics Data System (ADS)

Berliana Sipayung, Sinta; Nurlatifah, Amalia; Siswanto, Bambang; Slamet S, Lilik

2018-05-01

Climate change is one of the most important issues being discussed globally. It caused by global warming and indirectly affecting the world climate cycle. This research discussed the effect of climate change on rainfall pattern of Sambas District and predicted the future rainfall pattern due to climate change. CRU and TRMM were used and has been validated using in situ data. This research was used Climate Modelling and Prediction using CCAM (Conformal Cubic Atmospheric Model) which also validated by in situ data (correlation= 0.81). The results show that temperature trends in Sambas regency increased to 0.082°C/yr from 1991-2014 according to CRU data. High temperature trigger changes in rainfall patterns. Rainfall pattern in Sambas District has an equatorial type where the peak occurs when the sun is right on the equator. Rainfall in Sambas reaches the maximum in March and September when the equinox occurs. The CCAM model is used to project rainfall in Sambas District in the future. The model results show that rainfall in Sambas District is projected to increase to 0.018 mm/month until 2055 so the flow rate increase 0.006 m3/month and the water balance increase 0.009 mm/month.

Revisiting the latent heat nudging scheme for the rainfall assimilation of a simulated convective storm

NASA Astrophysics Data System (ADS)

Leuenberger, D.; Rossa, A.

2007-12-01

Next-generation, operational, high-resolution numerical weather prediction models require economical assimilation schemes for radar data. In the present study we evaluate and characterise the latent heat nudging (LHN) rainfall assimilation scheme within a meso-γ scale NWP model in the framework of identical twin simulations of an idealised supercell storm. Consideration is given to the model’s dynamical response to the forcing as well as to the sensitivity of the LHN scheme to uncertainty in the observations and the environment. The results indicate that the LHN scheme is well able to capture the dynamical structure and the right rainfall amount of the storm in a perfect environment. This holds true even in degraded environments but a number of important issues arise. In particular, changes in the low-level humidity field are found to affect mainly the precipitation amplitude during the assimilation with a fast adaptation of the storm to the system dynamics determined by the environment during the free forecast. A constant bias in the environmental wind field, on the other hand, has the potential to render a successful assimilation with the LHN scheme difficult, as the velocity of the forcing is not consistent with the system propagation speed determined by the wind. If the rainfall forcing moves too fast, the system propagation is supported and the assimilated storm and forecasts initialised therefrom develop properly. A too slow forcing, on the other hand, can decelerate the system and eventually disturb the system dynamics by decoupling the low-level moisture inflow from the main updrafts during the assimilation. This distortion is sustained in the free forecast. It has further been found that a sufficient temporal resolution of the rainfall input is crucial for the successful assimilation of a fast moving, coherent convective storm and that the LHN scheme, when applied to a convective storm, appears to necessitate a careful tuning.

Geophysical Factor Resolving of Rainfall Mechanism for Super Typhoons by Using Multiple Spatiotemporal Components Analysis

NASA Astrophysics Data System (ADS)

Huang, Chien-Lin; Hsu, Nien-Sheng

2016-04-01

This study develops a novel methodology to resolve the geophysical cause of typhoon-induced rainfall considering diverse dynamic co-evolution at multiple spatiotemporal components. The multi-order hidden patterns of complex hydrological process in chaos are detected to understand the fundamental laws of rainfall mechanism. The discovered spatiotemporal features are utilized to develop a state-of-the-art descriptive statistical model for mechanism validation, modeling and further prediction during typhoons. The time series of hourly typhoon precipitation from different types of moving track, atmospheric field and landforms are respectively precede the signal analytical process to qualify each type of rainfall cause and to quantify the corresponding affected degree based on the measured geophysical atmospheric-hydrological variables. This study applies the developed methodology in Taiwan Island which is constituted by complex diverse landform formation. The identified driving-causes include: (1) cloud height to ground surface; (2) co-movement effect induced by typhoon wind field with monsoon; (3) stem capacity; (4) interaction between typhoon rain band and terrain; (5) structural intensity variance of typhoon; and (6) integrated cloudy density of rain band. Results show that: (1) for the central maximum wind speed exceeding 51 m/sec, Causes (1) and (3) are the primary ones to generate rainfall; (2) for the typhoon moving toward the direction of 155° to 175°, Cause (2) is the primary one; (3) for the direction of 90° to 155°, Cause (4) is the primary one; (4) for the typhoon passing through mountain chain which above 3500 m, Cause (5) is the primary one; and (5) for the moving speed lower than 18 km/hr, Cause (6) is the primary one. Besides, the multiple geophysical component-based precipitation modeling can achieve 81% of average accuracy and 0.732 of average correlation coefficient (CC) within average 46 hours of duration, that improve their predictability.

Recent climate variability and its impacts on soybean yields in Southern Brazil

NASA Astrophysics Data System (ADS)

Ferreira, Danielle Barros; Rao, V. Brahmananda

2011-08-01

Recent climate variability in rainfall, temperatures (maximum and minimum), and the diurnal temperature range is studied with emphasis on its influence over soybean yields in southern Brazil, during 1969 to 2002. The results showed that the soybean ( Glycine max L. Merril) yields are more affected by changes in temperature during summer, while changes in rainfall are more important during the beginning of plantation and at its peak of development. Furthermore, soybean yields in Paraná are more sensitive to rainfall variations, while soybean yields in the Rio Grande do Sul are more sensitive to variations in temperature. Effects of interannual climatic variability on soybean yields are evaluated through three agro-meteorological models: additive Stewart, multiplicative Rao, and multiplicative Jensen. The Jensen model is able to reproduce the interannual behavior of soybean yield reasonably well.

An evaluation of the wind chill factor: its development and applicability.

PubMed

Bluestein, M

1998-04-01

The wind chill factor has become a standard meteorologic term in cold climates. Meteorologic charts provide wind chill temperatures meant to represent the hypothetical air temperature that would, under conditions of no wind, effect the same heat loss from unclothed human skin as does the actual combination of air temperature and wind velocity. As this wind chill factor has social and economic significance, an investigation was conducted on the development of this factor and its applicability based on modern heat transfer principles. The currently used wind chill factor was found to be based on a primitive study conducted by the U.S. Antarctic Service over 50 years ago. The resultant equation for the wind chill temperature assumes an unrealistic constant skin temperature and utilizes heat transfer coefficients that differ markedly from those obtained from equations of modern convective heat transfer methods. The combined effect of these two factors is to overestimate the effect of a given wind velocity and to predict a wind chill temperature that is too low.

Characteristics of Wind Velocity and Temperature Change Near an Escarpment-Shaped Road Embankment

PubMed Central

Kim, Young-Moon; You, Ki-Pyo; You, Jang-Youl

2014-01-01

Artificial structures such as embankments built during the construction of highways influence the surrounding airflow. Various types of damage can occur due to changes in the wind velocity and temperature around highway embankments. However, no study has accurately measured micrometeorological changes (wind velocity and temperature) due to embankments. This study conducted a wind tunnel test and field measurement to identify changes in wind velocity and temperature before and after the construction of embankments around roads. Changes in wind velocity around an embankment after its construction were found to be influenced by the surrounding wind velocity, wind angle, and the level difference and distance from the embankment. When the level difference from the embankment was large and the distance was up to 3H, the degree of wind velocity declines was found to be large. In changes in reference wind velocities around the embankment, wind velocity increases were not proportional to the rate at which wind velocities declined. The construction of the embankment influenced surrounding temperatures. The degree of temperature change was large in locations with large level differences from the embankment at daybreak and during evening hours when wind velocity changes were small. PMID:25136681

Characteristics of wind velocity and temperature change near an escarpment-shaped road embankment.

PubMed

Kim, Young-Moon; You, Ki-Pyo; You, Jang-Youl

2014-01-01

Artificial structures such as embankments built during the construction of highways influence the surrounding airflow. Various types of damage can occur due to changes in the wind velocity and temperature around highway embankments. However, no study has accurately measured micrometeorological changes (wind velocity and temperature) due to embankments. This study conducted a wind tunnel test and field measurement to identify changes in wind velocity and temperature before and after the construction of embankments around roads. Changes in wind velocity around an embankment after its construction were found to be influenced by the surrounding wind velocity, wind angle, and the level difference and distance from the embankment. When the level difference from the embankment was large and the distance was up to 3H, the degree of wind velocity declines was found to be large. In changes in reference wind velocities around the embankment, wind velocity increases were not proportional to the rate at which wind velocities declined. The construction of the embankment influenced surrounding temperatures. The degree of temperature change was large in locations with large level differences from the embankment at daybreak and during evening hours when wind velocity changes were small.

Natural variability of the Keetch-Byram Drought Index in the Hawaiian Islands

Treesearch

Klaus Dolling; Pao-Shin Chu; Francis Fujioka

2009-01-01

The Hawaiian Islands experience damaging wildfires on a yearly basis. Soil moisture or lack thereof influences the amount and flammability of vegetation. Incorporating daily maximum temperatures and daily rainfall amounts, the Keetch–Byram Drought Index (KBDI) estimates the amount of soil moisture by tracking daily maximum temperatures and rainfall. A previous study...

Interannual and Decadal Variability of Summer Rainfall over South America

NASA Technical Reports Server (NTRS)

Zhou, Jiayu; Lau, K.-M.

1999-01-01

Using the CPC (Climate Prediction Center) Merged Analysis of Precipitation product along with the Goddard Earth Observing System reanalysis and the Climate Analysis Center sea surface temperature (SST) data, we conduct a diagnostic study of the interannual and decadal scale variability of summer rainfall over South America. Results show three leading modes of rainfall variation identified with interannual, decadal, and long-term trend variability. Together, these modes explain more than half the total variance. The first mode is highly correlated with El Nino/southern oscillation (ENSO), showing severe drought over Northeast Brazil and copious rainfall over the Ecuador coast and the area of Uruguay-Southern Brazil in El Nino years. This pattern is attributed to the large scale zonal shift of the Walker circulation and local Hadley cell anomaly induced by positive (negative) SST anomaly over the eastern (western) equatorial Pacific. In El Nino years, two convective belts indicated by upper tropospheric velocity potential trough and mid-tropospheric rising motion, which are somewhat symmetric about the equator, extend toward the northeast and the southeast into the tropical North and South Atlantic respectively. Sandwiched between the ascent is a region of descending motion over Northeast Brazil. The southern branch of the anomalous Hadley cell is dynamically linked to the increase of rainfall over Uruguay-Southern Brazil. The regional response of anomalous circulation shows a stronger South American summer monsoon and an enhanced (weakened) subtropical high over the South Atlantic (South Pacific) Ocean. The decadal variation displays a meridional shift of the Intertropical Convergence Zone (ITCZ), which is tie to the anomalous cross-equatorial SST gradient over the Atlantic and the eastern Pacific. In conjunction with this mode is a large scale mass swing between the polar regions and midlatitudes in both hemispheres. Over the South Atlantic and the South Pacific, the changes of the strength of the subtropical high and the associated surface wind are dynamically consistent with the distribution of local SST anomalies, suggesting the importance of the atmospheric forcing in the decadal time scale. The decadal mode also presents a weak summer monsoon in its positive phase, which reduces the moisture supply from the equatorial Atlantic and the Amazon Basin and results in negative rainfall anomalies over the central Andes and Gran Chaco. The long-term trend shows decrease of rainfall from the northwest coast to the southeast subtropical region and a southward shift of Atlantic ITCZ that leads to increased rainfall over northern and eastern Brazil. Our result shows a close link of this mode to the observed SST warming trend over the subtropical South Atlantic and a remote connection to the interdecadal SST variation over the extratropical North Atlantic found in previous studies.

DIY versus Professional

ERIC Educational Resources Information Center

Rainboth, Donna; Munck, Miriam

2010-01-01

Weather, with its built-in atmospheric laboratory, is a natural source of inquiry. The ever-changing nature of weather provides a constant source of questions to investigate and connects to a multitude of physical science concepts. The question, "How accurate are homemade weather instruments in measuring air pressure, rainfall, wind speed and…

Effect of water potential and void ratio on erodibility for agricultural soils

USDA-ARS?s Scientific Manuscript database

Soil erodibility has confounded researchers for decades. Difficulties arise with initiation of motion, pore-water status, physical, and perhaps biological, material properties and type of applied energy (i.e. rainfall, runoff, freeze/thaw, wind). Though specific tests have been developed to determin...

A statistical technique for determining rainfall over land employing Nimbus-6 ESMR measurements

NASA Technical Reports Server (NTRS)

Rodgers, E.; Siddalingaiah, H.; Chang, A. T. C.; Wilheit, T. T.

1978-01-01

At 37 GHz, the frequency at which the Nimbus 6 Electrically Scanning Microwave Radiometer (ESMR 6) measures upwelling radiance, it was shown theoretically that the atmospheric scattering and the relative independence on electromagnetic polarization of the radiances emerging from hydrometers make it possible to monitor remotely active rainfall over land. In order to verify experimentally these theoretical findings and to develop an algorithm to monitor rainfall over land, the digitized ESMR 6 measurements were examined statistically. Horizontally and vertically polarized brightness temperature pairs (TH, TV) from ESMR 6 were sampled for areas of rainfall over land as determined from the rain recording stations and the WSR 57 radar, and areas of wet and dry ground (whose thermodynamic temperatures were greater than 5 C) over the Southeastern United States. These three categories of brightness temperatures were found to be significantly different in the sense that the chances that the mean vectors of any two populations coincided were less than 1 in 100.

Coupled modes of rainfall over China and the pacific sea surface temperature in boreal summertime

NASA Astrophysics Data System (ADS)

Li, Chun; Ma, Hao

2011-09-01

In addition, the possible atmospheric teleconnections of the coupled rainfall and SST modes were discussed. For the ENSO-NC mode, anomalous low-pressure and high-pressure over the Asian continent induces moisture divergence over North China and reduces summer rainfall there. For the WTP-YRV mode, East Asia-Pacific teleconnection induces moisture convergence over the Yangtze River valley and enhances the summer rainfall there. The TPMM SST and the summer rainfall anomalies over the YRVL are linked by a circumglobal, wave-train-like, atmospheric teleconnection.

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

Yoon, Jin -Ho

Amazon rainfall is subject to year-to-year fluctuation resulting in drought and flood in various intensities. A major climatic driver of the interannual variation of the Amazon rainfall is El Niño/Southern Oscillation. Also, the Sea Surface Temperature over the Atlantic Ocean is identified as an important climatic driver on the Amazon water cycle. Previously, observational datasets were used to support the Atlantic influence on Amazon rainfall. Furthermore, it is found that multiple global climate models do reproduce the Atlantic-Amazon link robustly. However, there exist differences in rainfall response, which primarily depends on the climatological rainfall amount.

The effect of airflow on thermographically determined temperature of the distal forelimb of the horse.

PubMed

Westermann, S; Stanek, C; Schramel, J P; Ion, A; Buchner, H H F

2013-09-01

Current literature suggests that thermographic imaging of horses should be performed in a draught-free room. However, studies on the effect of airflow on determined temperature have not been published. To investigate effects of airflow on thermographically determined temperature of horses' forelimbs; to assess the relationship of wind velocity, rectal temperature, ambient temperature and humidity. Thermographic images were obtained for the forelimbs of 6 horses in a draught-free room. Three replicates (R) with defined wind velocities (R1, 0.5-1.0 m/s; R2, 1.3-2.6 m/s; and R3, 3.0-4.0 m/s) were conducted. Each replicate consisted of a baseline image, a 15 min phase with the wind on and a 15 min phase with the wind off. We exposed only the right leg to airflow and determined the temperature by thermography with the wind on and wind off. Temperature differences between baseline and wind on, between wind on and wind off and between different wind velocities were analysed by a general linear model, Student's paired t test and ANOVA. After the onset of wind, the temperature on the right forelimb decreased within 1-3 min (by approximately 0.6°C at R1, 1.5°C at R2 and 2.1°C at R3). With the wind off, the temperature increased within 3 min (by approximately 1.2°C at R1, 1.7°C at R2 and 2.1°C at R3). With increasing wind velocity, the temperature differences between baseline and wind on and between wind on and wind off increased significantly. Barely noticeable wind velocities caused a decrease in thermographically determined temperatures of the forelimbs of the horse. Further research is required to assess the influence of airflow on other parts of the body and at different ambient temperatures, as well as the effect on horses with inflammatory lesions, especially of the distal limbs. It is essential for practitioners to perform thermography on horses in a draught-free environment in order to avoid false-positive or -negative diagnoses. © 2012 EVJ Ltd.

Surrogate modeling of joint flood risk across coastal watersheds

NASA Astrophysics Data System (ADS)

Bass, Benjamin; Bedient, Philip

2018-03-01

This study discusses the development and performance of a rapid prediction system capable of representing the joint rainfall-runoff and storm surge flood response of tropical cyclones (TCs) for probabilistic risk analysis. Due to the computational demand required for accurately representing storm surge with the high-fidelity ADvanced CIRCulation (ADCIRC) hydrodynamic model and its coupling with additional numerical models to represent rainfall-runoff, a surrogate or statistical model was trained to represent the relationship between hurricane wind- and pressure-field characteristics and their peak joint flood response typically determined from physics based numerical models. This builds upon past studies that have only evaluated surrogate models for predicting peak surge, and provides the first system capable of probabilistically representing joint flood levels from TCs. The utility of this joint flood prediction system is then demonstrated by improving upon probabilistic TC flood risk products, which currently account for storm surge but do not take into account TC associated rainfall-runoff. Results demonstrate the source apportionment of rainfall-runoff versus storm surge and highlight that slight increases in flood risk levels may occur due to the interaction between rainfall-runoff and storm surge as compared to the Federal Emergency Management Association's (FEMAs) current practices.

Short-term modulation of Indian summer monsoon rainfall by West Asian dust

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

Vinoj, V.; Rasch, Philip J.; Wang, Hailong

The Indian summer monsoon is the result of a complex interplay between radiative heating, dynamics and cloud and aerosol interactions. Despite increased scientific attention, the effect of aerosols on monsoons still remains uncertain. Here we present both observational evidence and numerical modeling results demonstrating a remote aerosol link to Indian summer monsoon rainfall. Rainfall over central India is positively correlated to natural aerosols over the Arabian Sea and West Asia. Simulations using a state-of-the-art global climate model support this remote aerosol link and indicate that dust aerosols induce additional moisture transport and convergence over Central India, producing increased monsoon rainfall.more » The convergence is driven through solar heating and latent heating within clouds over West Asia that increases surface winds over the Arabian Sea. On the other hand, sea-salt aerosol tends to counteract the effect of dust and reduces rainfall. Our findings highlight the importance of natural aerosols in modulating the strength of the Indian summer monsoon, and motivate additional research in how changes in background aerosols of natural origin may be influencing long-term trends in monsoon precipitation.« less

DOI/GTN-P climate and active-layer data acquired in the National Petroleum Reserve-Alaska and the Arctic National Wildlife Refuge

USGS Publications Warehouse

Urban, Frank E.; Clow, Gary D.

2014-01-01

This report provides data collected by the climate monitoring array of the U.S. Department of the Interior on Federal lands in Arctic Alaska over the period August 1998 to July 2013; this array is part of the Global Terrestrial Network for Permafrost, (DOI/GTN-P). In addition to presenting data, this report also describes monitoring, data collection, and quality-control methods. This array of 16 monitoring stations spans lat 68.5°N. to 70.5°N. and long 142.5°W. to 161°W., an area of approximately 150,000 square kilometers. Climate summaries are presented along with quality-controlled data. Data collection is ongoing and includes the following climate- and permafrost-related variables: air temperature, wind speed and direction, ground temperature, soil moisture, snow depth, rainfall totals, up- and downwelling shortwave radiation, and atmospheric pressure. These data were collected by the U.S. Geological Survey in close collaboration with the Bureau of Land Management and the U.S. Fish and Wildlife Service.

DOI/GTN-P Climate and active-layer data acquired in the National Petroleum Reserve–Alaska and the Arctic National Wildlife Refuge, 1998–2014

USGS Publications Warehouse

Urban, Frank E.; Clow, Gary D.

2016-03-04

This report provides data collected by the climate monitoring array of the U.S. Department of the Interior on Federal lands in Arctic Alaska over the period August 1998 to July 2014; this array is part of the Global Terrestrial Network for Permafrost (DOI/GTN-P). In addition to presenting data, this report also describes monitoring, data collection, and quality-control methods. The array of 16 monitoring stations spans lat 68.5°N. to 70.5°N. and long 142.5°W. to 161°W., an area of approximately 150,000 square kilometers. Climate summaries are presented along with quality-controlled data. Data collection is ongoing and includes the following climate- and permafrost-related variables: air temperature, wind speed and direction, ground temperature, soil moisture, snow depth, rainfall totals, up- and downwelling shortwave radiation, and atmospheric pressure. These data were collected by the U.S. Geological Survey in close collaboration with the Bureau of Land Management and the U.S. Fish and Wildlife Service.

DOI/GTN-P Climate and active-layer data acquired in the National Petroleum Reserve–Alaska and the Arctic National Wildlife Refuge, 1998–2015

USGS Publications Warehouse

Urban, Frank E.; Clow, Gary D.

2017-02-06

This report provides data collected by the climate monitoring array of the U.S. Department of the Interior on Federal lands in Arctic Alaska over the period August 1998 to July 2015; this array is part of the Global Terrestrial Network for Permafrost (DOI/GTN-P). In addition to presenting data, this report also describes monitoring, data collection, and quality-control methods. The array of 16 monitoring stations spans lat 68.5°N. to 70.5°N. and long 142.5°W. to 161°W., an area of approximately 150,000 square kilometers. Climate summaries are presented along with quality-controlled data. Data collection is ongoing and includes the following climate- and permafrost-related variables: air temperature, wind speed and direction, ground temperature, soil moisture, snow depth, rainfall totals, up- and downwelling shortwave radiation, and atmospheric pressure. These data were collected by the U.S. Geological Survey in close collaboration with the Bureau of Land Management and the U.S. Fish and Wildlife Service.

Data on the effect of geological and meteorological parameters on indoor radon and thoron level- case study: Kermanshah, Iran.

PubMed

Pirsaheb, Meghdad; Najafi, Farid; Hemati, Lida; Khosravi, Touba; Sharafi, Hooshmand

2018-06-01

The present study was aimed to evaluate the relationship between indoor radon and thoron concentrations, geological and meteorological parameters. The radon and thoron concentrations were determined in three hospitals in Kermanshah, the west part of Iran, using the RTM-1688-2 radon meter. Also, the type and porosity of the underlying soil and the meteorological parameters such as temperature, humidity, atmospheric pressure, rainfall and wind speed were studied and the obtained results analyzed using STATA-Ver.8. In this study the obtained radon concentration was furthered in buildings which constructed on the soil with clayey gravel and sand feature than the soil with clay characteristic and little pasty with a significant difference ( P < 0.05). While the lower coefficient about 1.3 was obtained in measured the thoron concentration and a significant difference was not observed. So the soil porosity can extremely effect on the indoor radon amount. Among all studied meteorological parameters, temperature has been determined as the most important meteorological parameter, influence the indoor radon and thoron concentrations.

Hydrologic impacts of past shifts of Earth's thermal equator offer insight into those to be produced by fossil fuel CO2.

PubMed

Broecker, Wallace S; Putnam, Aaron E

2013-10-15

Major changes in global rainfall patterns accompanied a northward shift of Earth's thermal equator at the onset of an abrupt climate change 14.6 kya. This northward pull of Earth's wind and rain belts stemmed from disintegration of North Atlantic winter sea ice cover, which steepened the interhemispheric meridional temperature gradient. A southward migration of Earth's thermal equator may have accompanied the more recent Medieval Warm to Little Ice Age climate transition in the Northern Hemisphere. As fossil fuel CO2 warms the planet, the continents of the Northern Hemisphere are expected to warm faster than the Southern Hemisphere oceans. Therefore, we predict that a northward shift of Earth's thermal equator, initiated by an increased interhemispheric temperature contrast, may well produce hydrologic changes similar to those that occurred during past Northern Hemisphere warm periods. If so, the American West, the Middle East, and southern Amazonia will become drier, and monsoonal Asia, Venezuela, and equatorial Africa will become wetter. Additional paleoclimate data should be acquired and model simulations should be conducted to evaluate the reliability of this analog.

DOI/GTN-P climate and active-layer data acquired in the National Petroleum Reserve: Alaska and the Arctic National Wildlife Refuge, 1998-2011

USGS Publications Warehouse

Urban, Frank E.; Clow, Gary D.

2014-01-01

This report provides data collected by the climate monitoring array of the U.S. Department of the Interior on Federal lands in Arctic Alaska over the period August 1998 to July 2011; this array is part of the Global Terrestrial Network for Permafrost, (DOI/GTN-P). In addition to presenting data, this report also describes monitoring, data collection, and quality-control methodology. This array of 16 monitoring stations spans lat 68.5°N. to 70.5°N. and long 142.5°W. to 161°W., an area of approximately 150,000 square kilometers. Climate summaries are presented along with quality-controlled data. Data collection is ongoing and includes the following climate- and permafrost-related variables: air temperature, wind speed and direction, ground temperature and soil moisture, snow depth, rainfall, up- and downwelling shortwave radiation, and atmospheric pressure. These data were collected by the U.S. Geological Survey in close collaboration with the Bureau of Land Management and the U.S. Fish and Wildlife Service.

Impervious surfaces and sewer pipe effects on stormwater runoff temperature

NASA Astrophysics Data System (ADS)

Sabouri, F.; Gharabaghi, B.; Mahboubi, A. A.; McBean, E. A.

2013-10-01

The warming effect of the impervious surfaces in urban catchment areas and the cooling effect of underground storm sewer pipes on stormwater runoff temperature are assessed. Four urban residential catchment areas in the Cities of Guelph and Kitchener, Ontario, Canada were evaluated using a combination of runoff monitoring and modelling. The stormwater level and water temperature were monitored at 10 min interval at the inlet of the stormwater management ponds for three summers 2009, 2010 and 2011. The warming effect of the ponds is also studied, however discussed in detail in a separate paper. An artificial neural network (ANN) model for stormwater temperature was trained and validated using monitoring data. Stormwater runoff temperature was most sensitive to event mean temperature of the rainfall (EMTR) with a normalized sensitivity coefficient (Sn) of 1.257. Subsequent levels of sensitivity corresponded to the longest sewer pipe length (LPL), maximum rainfall intensity (MI), percent impervious cover (IMP), rainfall depth (R), initial asphalt temperature (AspT), pipe network density (PND), and rainfall duration (D), respectively. Percent impervious cover of the catchment area (IMP) was the key parameter that represented the warming effect of the paved surfaces; sensitivity analysis showed IMP increase from 20% to 50% resulted in runoff temperature increase by 3 °C. The longest storm sewer pipe length (LPL) and the storm sewer pipe network density (PND) are the two key parameters that control the cooling effect of the underground sewer system; sensitivity analysis showed LPL increase from 345 to 966 m, resulted in runoff temperature drop by 2.5 °C.

On the Relationship of Rainfall and Temperature across Amazonia

NASA Astrophysics Data System (ADS)

Ribeiro Lima, C. H.; AghaKouchak, A.

2017-12-01

Extreme droughts in Amazonia seem to become more frequent and have been associated with local and global impacts on society and the ecosystem. The understanding of the dynamics and causes of Amazonia droughts have attracted some attention in the last years and pose several challenges for the scientific community. For instance, in previous work we have identified, based on empirical data, a compounding effect during Amazonia droughts: periods of low rainfall are always associated with positive anomalies of near surface air temperature. This inverse relationship of temperature and rainfall appears at multiple time scales and its intensity varies across Amazonia. To our knowledge, these findings have not been properly addressed in the literature, being not clear whether there is a causal relationship between these two variables, and in this case, which one leads the other one, or they are just responding to the same causal factor. Here we investigate the hypothesis that high temperatures during drought periods are a major response to an increase in the shortwave radiation (due to the lack of clouds) not compensating by an expected increase in the evapotranspiration from the rainforest. Our empirical analysis is based on observed series of daily temperature and rainfall over the Brazilian Amazonia and reanalysis data of cloud cover, outgoing longwave radiation (OLR) and moisture fluxes. The ability of Global Circulation Models (GCMs) to reproduce such compounding effect is also investigated for the historical period and for future RCP scenarios of global climate change. Preliminary results show that this is a plausible hypothesis, despite the complexity of land-atmosphere processes of mass and energy fluxes in Amazonia. This work is a step forward in better understanding the compounding effects of rainfall and temperature on Amazonia droughts, and what changes one might expect in a future warming climate.

The atmospheric boundary layer in the CSIRO global climate model: simulations versus observations

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Rotstayn, L. D.; Krummel, P. B.

2002-07-01

A 5-year simulation of the atmospheric boundary layer in the CSIRO global climate model (GCM) is compared with detailed boundary-layer observations at six locations, two over the ocean and four over land. Field observations, in the form of surface fluxes and vertical profiles of wind, temperature and humidity, are generally available for each hour over periods of one month or more in a single year. GCM simulations are for specific months corresponding to the field observations, for each of five years. At three of the four land sites (two in Australia, one in south-eastern France), modelled rainfall was close to the observed climatological values, but was significantly in deficit at the fourth (Kansas, USA). Observed rainfall during the field expeditions was close to climatology at all four sites. At the Kansas site, modelled screen temperatures (Tsc), diurnal temperature amplitude and sensible heat flux (H) were significantly higher than observed, with modelled evaporation (E) much lower. At the other three land sites, there is excellent correspondence between the diurnal amplitude and phase and absolute values of each variable (Tsc, H, E). Mean monthly vertical profiles for specific times of the day show strong similarities: over land and ocean in vertical shape and absolute values of variables, and in the mixed-layer and nocturnal-inversion depths (over land) and the height of the elevated inversion or height of the cloud layer (over the sea). Of special interest is the presence climatologically of early morning humidity inversions related to dewfall and of nocturnal low-level jets; such features are found in the GCM simulations. The observed day-to-day variability in vertical structure is captured well in the model for most sites, including, over a whole month, the temperature range at all levels in the boundary layer, and the mix of shallow and deep mixed layers. Weaknesses or unrealistic structure include the following, (a) unrealistic model mixed-layer temperature profiles over land in clear skies, related to use of a simple local first-order turbulence closure, (b) a tendency to overpredict cloud liquid water near the surface.

Female Agassiz’s desert tortoise activity at a wind energy facility in southern California: The influence of an El Niño event

USGS Publications Warehouse

Ennen, Josh R.; Meyer-Wilkins, Kathie; Lovich, Jeffrey

2012-01-01

We compared spring-summer activity of adult female Agassiz’s Desert Tortoises (Gopherus agassizii) among three consecutive years (1997, 1998, and 1999) that differed dramatically in winter rainfall and annual plant production at a wind energy facility in the Sonoran Desert of southern California. Winter rainfall was approximately 71%, 190%, and 17% of the long-term average (October-March = 114 mm) for this area in water years (WY) 1997, 1998, and 1999, respectively. The substantial precipitation caused by an El Niño Southern Oscillation (ENSO) event in WY 1998 produced a generous annual food plant supply (138.2 g dry biomass/ m2) in the spring. Primary production of winter annuals during below average rainfall years (WY 1997 and WY 1999) was reduced to 98.3 and 0.2 g/m2, respectively. Mean rates of movement and mean body condition indices (mass/length) did not differ significantly among the years. The drought year following ENSO (WY 1999) was statistically similar to ENSO in every other measured value, while WY 1997 (end of a two year drought) was statistically different from ENSO using activity area, minimum number of burrows used, and percentage of non-movements. Our data suggest that female G. agassizii activity can be influenced by environmental conditions in previous years.

Multi-model analysis of the Atlantic influence on Southern Amazon rainfall

DOE PAGES

Yoon, Jin -Ho

2015-12-07

Amazon rainfall is subject to year-to-year fluctuation resulting in drought and flood in various intensities. A major climatic driver of the interannual variation of the Amazon rainfall is El Niño/Southern Oscillation. Also, the Sea Surface Temperature over the Atlantic Ocean is identified as an important climatic driver on the Amazon water cycle. Previously, observational datasets were used to support the Atlantic influence on Amazon rainfall. Furthermore, it is found that multiple global climate models do reproduce the Atlantic-Amazon link robustly. However, there exist differences in rainfall response, which primarily depends on the climatological rainfall amount.

Direct measurement of the combined effects of lichen, rainfall, and temperature on silicate weathering

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

Brady, P.V.; Dorn, R.I.; Brazel, A.J.

1999-10-01

A key uncertainty in models of the global carbonate-silicate cycle and long-term climate is the way that silicates weather under different climatologic conditions, and in the presence or absence of organic activity. Digital imaging of basalts in Hawaii resolves the coupling between temperature, rainfall, and weathering in the presence and absence of lichens. Activation energies for abiotic dissolution of plagioclase (23.1 {+-} 2.5 kcal/mol) and olivine (21.3 {+-} 2.7 kcal/mol) are similar to those measured in the laboratory, and are roughly double those measured from samples taken underneath lichen. Abiotic weathering rates appear to be proportional to rainfall. Dissolution ofmore » plagioclase and olivine underneath lichen is far more sensitive to rainfall.« less

An observational and modeling study of the August 2017 Florida climate extreme event.

NASA Astrophysics Data System (ADS)

Konduru, R.; Singh, V.; Routray, A.

2017-12-01

A special report on the climate extremes by the Intergovernmental Panel on Climate Change (IPCC) elucidates that the sole cause of disasters is due to the exposure and vulnerability of the human and natural system to the climate extremes. The cause of such a climate extreme could be anthropogenic or non-anthropogenic. Therefore, it is challenging to discern the critical factor of influence for a particular climate extreme. Such kind of perceptive study with reasonable confidence on climate extreme events is possible only if there exist any past case studies. A similar rarest climate extreme problem encountered in the case of Houston floods and extreme rainfall over Florida in August 2017. A continuum of hurricanes like Harvey and Irma targeted the Florida region and caused catastrophe. Due to the rarity of August 2017 Florida climate extreme event, it requires the in-depth study on this case. To understand the multi-faceted nature of the event, a study on the development of the Harvey hurricane and its progression and dynamics is significant. Current article focus on the observational and modeling study on the Harvey hurricane. A global model named as NCUM (The global UK Met office Unified Model (UM) operational at National Center for Medium Range Weather Forecasting, India, was utilized to simulate the Harvey hurricane. The simulated rainfall and wind fields were compared with the observational datasets like Tropical Rainfall Measuring Mission rainfall datasets and Era-Interim wind fields. The National Centre for Environmental Prediction (NCEP) automated tracking system was utilized to track the Harvey hurricane, and the tracks were analyzed statistically for different forecasts concerning the Harvey hurricane track of Joint Typhon Warning Centre. Further, the current study will be continued to investigate the atmospheric processes involved in the August 2017 Florida climate extreme event.

Analysis of trends in streamflow and its linkages with rainfall and anthropogenic factors in Gomti River basin of North India

NASA Astrophysics Data System (ADS)

Abeysingha, N. S.; Singh, Man; Sehgal, V. K.; Khanna, Manoj; Pathak, Himanshu

2016-02-01

Trend analysis of hydro-climatic variables such as streamflow, rainfall, and temperature provides useful information for effective water resources planning, designing, and management. Trends in observed streamflow at four gauging stations in the Gomti River basin of North India were assessed using the Mann-Kendall and Sen's slope for the 1982 to 2012 period. The relationships between trends in streamflow and rainfall were studied by correlation analyses. There was a gradual decreasing trend of annual, monsoonal, and winter seasonal streamflow ( p < 0.05) from the midstream to the downstream of the river and also a decreasing trend of annual streamflow for the 5-year moving averaged standardized anomalies of streamflow for the entire basin. The declining trend in the streamflow was attributed partly to the increased water withdrawal, to increased air temperature, to higher population, and partly to significant reducing trend of post monsoon rainfall especially at downstream. Upstream gauging station showed a significant increasing trend of streamflow (1.6 m3/s/year) at annual scale, and this trend was attributed to the significant increasing trend of catchment rainfall (9.54 mm/year). It was further evident in the significant coefficient of positive correlation ( ρ = 0.8) between streamflow and catchment rainfall. The decreasing trend in streamflow and post-monsoon rainfall especially towards downstream area with concurrent increasing trend of temperature indicates a drying tendency of the Gomti River basin over the study period. The results of this study may help stakeholders to design streamflow restoration strategies for sustainable water management planning of the Gomti River basin.

Track-pattern-based seasonal prediction model for intense tropical cyclone activities over the North Atlantic and the western North Pacific basins

NASA Astrophysics Data System (ADS)

Choi, W.; Ho, C. H.

2015-12-01

Intense tropical cyclones (TCs) accompanying heavy rainfall and destructive wind gusts sometimes cause incredible socio-economic damages in the regions near their landfall. This study aims to analyze intense TC activities in the North Atlantic (NA) and the western North Pacific (WNP) basins and develop their track propensity seasonal prediction model. Considering that the number of TCs in the NA basin is much smaller than that in the WNP basin, different intensity criteria are used; category 1 and above for NA and category 3 and above for WNP based on Saffir-Simpson hurricane wind scale. By using a fuzzy clustering method, intense TC tracks in the NA and the WNP basins are classified into two and three representative patterns, respectively. Each pattern shows empirical relationships with climate variabilities such as sea surface temperature distribution associated with El Niño/La Niña or Atlantic Meridional Mode, Pacific decadal oscillation, upper and low level zonal wind, and strength of subtropical high. The hybrid statistical-dynamical method has been used to develop the seasonal prediction model for each pattern based on statistical relationships between the intense TC activity and seasonal averaged key predictors. The model performance is statistically assessed by cross validation for the training period (1982-2013) and has been applied for the 2014 and 2015 prediction. This study suggests applicability of this model to real prediction work and provide bridgehead of attempt for intense TC prediction.

Oceanic and atmospheric conditions associated with the pentad rainfall over the southeastern peninsular India during the North-East Indian Monsoon season

NASA Astrophysics Data System (ADS)

Shanmugasundaram, Jothiganesh; Lee, Eungul

2018-03-01

The association of North-East Indian Monsoon rainfall (NEIMR) over the southeastern peninsular India with the oceanic and atmospheric conditions over the adjacent ocean regions at pentad time step (five days period) was investigated during the months of October to December for the period 1985-2014. The non-parametric correlation and composite analyses were carried out for the simultaneous and lagged time steps (up to four lags) of oceanic and atmospheric variables with pentad NEIMR. The results indicated that NEIMR was significantly correlated: 1) positively with both sea surface temperature (SST) led by 1-4 pentads (lag 1-4 time steps) and latent heat flux (LHF) during the simultaneous, lag 1 and 2 time steps over the equatorial western Indian Ocean, 2) positively with SST but negatively with LHF (less heat flux from ocean to atmosphere) during the same and all the lagged time steps over the Bay of Bengal. Consistently, during the wet NEIMR pentads over the southeastern peninsular India, SST significantly increased over the Bay of Bengal during all the time steps and the equatorial western Indian Ocean during the lag 2-4 time steps, while the LHF decreased over the Bay of Bengal (all time steps) and increased over the Indian Ocean (same, lag 1 and 2). The investigation on ocean-atmospheric interaction revealed that the enhanced LHF over the equatorial western Indian Ocean was related to increased atmospheric moisture demand and increased wind speed, whereas the reduced LHF over the Bay of Bengal was associated with decreased atmospheric moisture demand and decreased wind speed. The vertically integrated moisture flux and moisture transport vectors from 1000 to 850 hPa exhibited that the moisture was carried away from the equatorial western Indian Ocean to the strong moisture convergence regions of the Bay of Bengal during the same and lag 1 time steps of wet NEIMR pentads. Further, the moisture over the Bay of Bengal was transported to the southeastern peninsular India through stronger cyclonic circulations, which were confirmed by the moisture transport vectors and positive vorticity. The identified ocean and atmosphere processes, associated with the wet NEIMR conditions, could be a valuable scientific input for enhancing the rainfall predictability, which has a huge socioeconomic value to agriculture and water resource management sectors in the southeastern peninsular India.

Water quality prediction of marine recreational beaches receiving watershed baseflow and stormwater runoff in southern California, USA.

PubMed

He, Li-Ming Lee; He, Zhen-Li

2008-05-01

Beach advisories are issued to the public in California when the concentration of fecal indicator bacteria (FIB), including total coliform, fecal coliform (or Escherichia coli), and Enterococcus, exceed their recreational water health standards, or when the amount of a rainfall event is above the pre-determined threshold. However, it is not fully understood about how and to what degree stormwater runoff or baseflow exerts impacts on beach water quality. Furthermore, current laboratory methods used to determine the FIB levels take 18-96 h, which is too slow to keep pace with changes in FIB levels in water. Thus, a beach may not be posted when it is contaminated, and may be posted under advisory when bacterial levels have already decreased to within water quality standards. The study was designed to address the above critical issues. There were large temporal and spatial variations in FIB concentrations along two popular State Beaches in San Diego, CA, USA. The rainstorm-induced runoff from the watersheds exerts significant impacts on the marine recreational water quality of the beaches adjacent to lagoons during the first 24-48 h after a rain event. The large volume of stormwater runoff discharging to beaches caused high FIB concentrations in beach water not only at the lagoon outlet channel and the mixing zone, but also at the locations 90 m away from the channel northward or southward along the shoreline. The geomorphology of beach shoreline, distance from the outlet channel, wind strength, wind direction, tide height, wave height, rainfall, time lapse after a rainstorm, or channel flow rate played a role in affecting the distribution of FIB concentrations in beach water. Despite the great temporal and spatial variability of FIB concentrations along a shoreline, the artificial neural network-based models developed in this study are capable of successfully predicting FIB concentrations at different beaches, different locations, and different times under baseflow or rainstorm conditions. The models are based on readily measurable variables including temperature, conductivity, pH, turbidity, channel water flow, rainfall, and/or time lapse after a rainstorm. The established models will help fill the current gap between beach posting and actual water quality and make more meaningful and effective decisions on beach closures and advisories.

Climate change in Lagos state, Nigeria: what really changed?

PubMed

Sojobi, Adebayo Olatunbosun; Balogun, Isaac Idowu; Salami, Adebayo Wahab

2015-10-01

Our study revealed periodicities of 2.3 and 2.25 years in wet and dry seasons and periodicities of 2 to 5 years on seasonal and annual timescales. Minimum temperature (Tmin), maximum temperature (Tmax) and evaporation recorded increases of 2.47, 1.37 and 28.37 %, respectively, but a reduction of 19.58 % in rainfall on decadal timescale. Periodicity of 8 to 12 years was also observed in annual Tmax. Cramer's test indicated a warming trend with significant Tmax increase in February, April, July, August, October and November during 2000-2009 on decadal monthly timescale, a significant decline in Summer rainfall but significant Tmax increase in Spring, Autumn and Winter on decadal seasonal timescale. The low correlation of rainfall with temperature parameters and evaporation indicates that advection of moisture into Lagos State seems to be the dominant mechanism controlling rainfall within the State alongside other tropical and extra-tropical factors. In addition, our study revealed that the persistent state of minimum temperature often precedes the arrival and reversal of the phase of maximum temperature. Furthermore, our study also revealed that extreme and high variable rainfalls, which are associated with the increased warming trend, had periodicities of 1 to 3 years with a probability of 86.45 % of occurring every 3 years between April and September. It is recommended that government and private sector should give financial and technical supports to climate researches in order to appropriately inform policy making to improve the adaptive capacity and resilience of Lagos State against climate change impacts and guard against maladaptation.

A high space-time resolution dataset linking meteorological forcing and hydro-sedimentary response in a mesoscale Mediterranean catchment (Auzon) of the Ardèche region, France

NASA Astrophysics Data System (ADS)

Nord, Guillaume; Boudevillain, Brice; Berne, Alexis; Branger, Flora; Braud, Isabelle; Dramais, Guillaume; Gérard, Simon; Le Coz, Jérôme; Legoût, Cédric; Molinié, Gilles; Van Baelen, Joel; Vandervaere, Jean-Pierre; Andrieu, Julien; Aubert, Coralie; Calianno, Martin; Delrieu, Guy; Grazioli, Jacopo; Hachani, Sahar; Horner, Ivan; Huza, Jessica; Le Boursicaud, Raphaël; Raupach, Timothy H.; Teuling, Adriaan J.; Uber, Magdalena; Vincendon, Béatrice; Wijbrans, Annette

2017-03-01

A comprehensive hydrometeorological dataset is presented spanning the period 1 January 2011-31 December 2014 to improve the understanding of the hydrological processes leading to flash floods and the relation between rainfall, runoff, erosion and sediment transport in a mesoscale catchment (Auzon, 116 km2) of the Mediterranean region. Badlands are present in the Auzon catchment and well connected to high-gradient channels of bedrock rivers which promotes the transfer of suspended solids downstream. The number of observed variables, the various sensors involved (both in situ and remote) and the space-time resolution ( ˜ km2, ˜ min) of this comprehensive dataset make it a unique contribution to research communities focused on hydrometeorology, surface hydrology and erosion. Given that rainfall is highly variable in space and time in this region, the observation system enables assessment of the hydrological response to rainfall fields. Indeed, (i) rainfall data are provided by rain gauges (both a research network of 21 rain gauges with a 5 min time step and an operational network of 10 rain gauges with a 5 min or 1 h time step), S-band Doppler dual-polarization radars (1 km2, 5 min resolution), disdrometers (16 sensors working at 30 s or 1 min time step) and Micro Rain Radars (5 sensors, 100 m height resolution). Additionally, during the special observation period (SOP-1) of the HyMeX (Hydrological Cycle in the Mediterranean Experiment) project, two X-band radars provided precipitation measurements at very fine spatial and temporal scales (1 ha, 5 min). (ii) Other meteorological data are taken from the operational surface weather observation stations of Météo-France (including 2 m air temperature, atmospheric pressure, 2 m relative humidity, 10 m wind speed and direction, global radiation) at the hourly time resolution (six stations in the region of interest). (iii) The monitoring of surface hydrology and suspended sediment is multi-scale and based on nested catchments. Three hydrometric stations estimate water discharge at a 2-10 min time resolution. Two of these stations also measure additional physico-chemical variables (turbidity, temperature, conductivity) and water samples are collected automatically during floods, allowing further geochemical characterization of water and suspended solids. Two experimental plots monitor overland flow and erosion at 1 min time resolution on a hillslope with vineyard. A network of 11 sensors installed in the intermittent hydrographic network continuously measures water level and water temperature in headwater subcatchments (from 0.17 to 116 km2) at a time resolution of 2-5 min. A network of soil moisture sensors enables the continuous measurement of soil volumetric water content at 20 min time resolution at 9 sites. Additionally, concomitant observations (soil moisture measurements and stream gauging) were performed during floods between 2012 and 2014. Finally, this dataset is considered appropriate for understanding the rainfall variability in time and space at fine scales, improving areal rainfall estimations and progressing in distributed hydrological and erosion modelling. DOI of the referenced dataset: doi:10.6096/MISTRALS-HyMeX.1438.

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Interactions Between Raindrop Impact and Shallow Interrill Flow Under Wind-Driven Rain

USDA-ARS?s Scientific Manuscript database

Raindrops impacting shallow interrill flow create hydraulic friction in overland flow, and the roughness caused by raindrops against the shallow flow is generally explained by the Darcy-Weisbach friction coefficient, which is calculated as a function of rainfall intensity along with bed roughness. H...

Interactions between raindrop impact and shallow interrill flow under wind-driven rain (WDR)

USDA-ARS?s Scientific Manuscript database

Raindrops impacting shallow interrill flow create hydraulic friction in overland flow, and the roughness caused by raindrops against the shallow flow is generally explained by the Darcy-Weisbach friction coefficient, which is calculated as a function of rainfall intensity along with bed roughness. H...

Observations of white drupelets on three blackberry cultivars in south Mississippi

USDA-ARS?s Scientific Manuscript database

White drupelet disorder has long been known as a problem in blackberry production. Several possible causes have been discussed, such as low humidity, wind, rainfall, high light intensities, UV light, stinkbugs, red berry mites, and some interaction of some or all of these. In 2016, we observed three...

Why was the strengthening of rainfall in summer over the Yangtze River valley in 2016 less pronounced than that in 1998 under similar preceding El Niño events?—Role of midlatitude circulation in August

NASA Astrophysics Data System (ADS)

Li, Chaofan; Chen, Wei; Hong, Xiaowei; Lu, Riyu

2017-11-01

It is widely recognized that rainfall over the Yangtze River valley (YRV) strengthens considerably during the decaying summer of El Niño, as demonstrated by the catastrophic flooding suffered in the summer of 1998. Nevertheless, the rainfall over the YRV in the summer of 2016 was much weaker than that in 1998, despite the intensity of the 2016 El Niño having been as strong as that in 1998. A thorough comparison of the YRV summer rainfall anomaly between 2016 and 1998 suggests that the difference was caused by the sub-seasonal variation in the YRV rainfall anomaly between these two years, principally in August. The precipitation anomaly was negative in August 2016—different to the positive anomaly of 1998. Further analysis suggests that the weaker YRV rainfall in August 2016 could be attributable to the distinct circulation anomalies over the midlatitudes. The intensified "Silk Road Pattern" and upper-tropospheric geopotential height over the Urals region, both at their strongest since 1980, resulted in an anticyclonic circulation anomaly over midlatitude East Asia with anomalous easterly flow over the middle-to-lower reaches of the YRV in the lower troposphere. This easterly flow reduced the climatological wind, weakened the water vapor transport, and induced the weaker YRV rainfall in August 2016, as compared to that in 1998. Given the unique sub-seasonal variation of the YRV rainfall in summer 2016, more attention should be paid to midlatitude circulation—besides the signal in the tropics—to further our understanding of the predictability and variation of YRV summer rainfall.

The collaborative historical African rainfall model: description and evaluation

USGS Publications Warehouse

Funk, Christopher C.; Michaelsen, Joel C.; Verdin, James P.; Artan, Guleid A.; Husak, Gregory; Senay, Gabriel B.; Gadain, Hussein; Magadazire, Tamuka

2003-01-01

In Africa the variability of rainfall in space and time is high, and the general availability of historical gauge data is low. This makes many food security and hydrologic preparedness activities difficult. In order to help overcome this limitation, we have created the Collaborative Historical African Rainfall Model (CHARM). CHARM combines three sources of information: climatologically aided interpolated (CAI) rainfall grids (monthly/0.5° ), National Centers for Environmental Prediction reanalysis precipitation fields (daily/1.875° ) and orographic enhancement estimates (daily/0.1° ). The first set of weights scales the daily reanalysis precipitation fields to match the gridded CAI monthly rainfall time series. This produces data with a daily/0.5° resolution. A diagnostic model of orographic precipitation, VDELB—based on the dot-product of the surface wind V and terrain gradient (DEL) and atmospheric buoyancy B—is then used to estimate the precipitation enhancement produced by complex terrain. Although the data are produced on 0.1° grids to facilitate integration with satellite-based rainfall estimates, the ‘true’ resolution of the data will be less than this value, and varies with station density, topography, and precipitation dynamics. The CHARM is best suited, therefore, to applications that integrate rainfall or rainfall-driven model results over large regions. The CHARM time series is compared with three independent datasets: dekadal satellite-based rainfall estimates across the continent, dekadal interpolated gauge data in Mali, and daily interpolated gauge data in western Kenya. These comparisons suggest reasonable accuracies (standard errors of about half a standard deviation) when data are aggregated to regional scales, even at daily time steps. Thus constrained, numerical weather prediction precipitation fields do a reasonable job of representing large-scale diurnal variations.

Disentangling the role of Natural Variability and Climate Change in the aggravation of Droughts in central Chile

NASA Astrophysics Data System (ADS)

Garreaud, R. D.; Boisier, J. P.; Rondanelli, R. F.

2016-12-01

Among other climate extreme events, droughts (annual rainfall deficit larger than 25%) have punctuated the hydro-climate history of central Chile (30-40°S) with profoundly negative effects on physical (e.g., water storage depletion), ecological (e.g., increase in forest fires) and human systems (e.g., major distress in rural communities). In this presentation we show that intense but short-lived (1 or 2 years long) droughts are associated with anticyclonic (cyclonic) anomalies over the subtropical south Pacific (Amudsen sea), reduced synoptic-scale variability in that area and weakening of the westerly winds impinging the west coast of South America. These large-scale anomalies often occurs in connection with the cold phase of ENSO (La Niña events). Of particular interest is an uninterrupted rainfall deficit since 2010 to date, referred to as the central Chile mega-drought (MD) in virtue of its unprecedented character in term of duration, spatial extent and coincidence with warm air temperatures. The protracted MD shares some of the climate features of the historical events but for the prevalence of near-neutral ENSO years with the exception of 2010 (La Niña) and 2015 (intense El Niño). Thus, we use a suite of fully-coupled and SST-forced climate simulations to disentangle natural and anthropogenic contributions to current mega drought as well as to shed light in the physical link between global climate change and rainfall deficit in central Chile drought. It turns out that anthropogenic climate change accounts for about a third of the drought as it forces SAM towards its positive polarity. The later enhances a dipole of geopotential height over the South Pacific that is conducive to dry conditions in central Chile.

Roles of tropical SST patterns during two types of ENSO in modulating wintertime rainfall over southern China

NASA Astrophysics Data System (ADS)

Xu, Kang; Huang, Qing-Lan; Tam, Chi-Yung; Wang, Weiqiang; Chen, Sheng; Zhu, Congwen

2018-03-01

The impacts of the eastern-Pacific (EP) and central-Pacific (CP) El Niño-Southern Oscillation (ENSO) on the southern China wintertime rainfall (SCWR) have been investigated. Results show that wintertime rainfall over most stations in southern China is enhanced (suppressed) during the EP (CP) El Niño, which are attributed to different atmospheric responses in the western North Pacific (WNP) and South China Sea (SCS) during two types of ENSO. When EP El Niño occurs, an anomalous low-level anticyclone is present over WNP/the Philippines region, resulting in stronger-than-normal southwesterlies over SCS. Such a wind branch acts to suppress East Asian winter monsoon (EAWM) and enhance moisture supply, implying surplus SCWR. During CP El Niño, however, anomalous sinking and low-level anticyclonic flow are found to cover a broad region in SCS. These circulation features are associated with moisture divergence over the northern part of SCS and suppressed SCWR. General circulation model experiments have also been conducted to study influence of various tropical sea surface temperature (SST) patterns on the EAWM atmospheric circulation. For EP El Niño, formation of anomalous low-level WNP anticyclone is jointly attributed to positive/negative SST anomalies (SSTA) over the central-to-eastern/ western equatorial Pacific. However, both positive and negative CP Niño-related-SSTA, located respectively over the central Pacific and WNP/SCS, offset each other and contribute a weak but broad-scale anticyclone centered at SCS. These results suggest that, besides the vital role of SST warming, SST cooling over SCS/WNP during two types of El Niño should be considered carefully for understanding the El Niño-EAWM relationship.

A simple model for farmland nitrogen loss to surface runoff with raindrop driven process

NASA Astrophysics Data System (ADS)

Tong, J.; Li, J.

2016-12-01

It has been widely recognized that surface runoff from the agricultural fields is an important source of non-point source pollution (NPSP). Moreover, as the agricultural country with the largest nitrogen fertilizer production, import and consumption in the world, our nation should pay greater attention to the over-application and inefficient use of nitrogen (N) fertilizer, which may cause severe pollution both in surface water and groundwater. To figure out the transfer mechanism between the soil solution and surface runoff, lots of laboratory test were conducted and related models were established in this study. But little of them was carried out in field scale since a part of variables are hard to control and some uncontrollable natural factors including rainfall intensity, temperature, wind speeds, soil spatial heterogeneity etc., may affect the field experimental results. Despite that, field tests can better reflect the mechanism of soil chemical loss to surface runoff than laboratory experiments, and the latter tend to oversimplify the environmental conditions. Therefore, a physically based, nitrogen transport model was developed and tested with so called semi-field experiments (i.e., artificial rainfall instead of natural rainfall was applied in the test). Our model integrated both raindrop driven process and diffusion effect along with the simplified nitrogen chain reactions. The established model was solved numerically through the modified Hydrus-1d source code, and the model simulations closely agree with the experimental data. Furthermore, our model indicates that the depth of the exchange layer and raindrop induced water transfer rate are two important parameters, and they have different impacts on the simulation results. The study results can provide references for preventing and controlling agricultural NPSP.

Long-range forecast of all India summer monsoon rainfall using adaptive neuro-fuzzy inference system: skill comparison with CFSv2 model simulation and real-time forecast for the year 2015

NASA Astrophysics Data System (ADS)

Chaudhuri, S.; Das, D.; Goswami, S.; Das, S. K.

2016-11-01

All India summer monsoon rainfall (AISMR) characteristics play a vital role for the policy planning and national economy of the country. In view of the significant impact of monsoon system on regional as well as global climate systems, accurate prediction of summer monsoon rainfall has become a challenge. The objective of this study is to develop an adaptive neuro-fuzzy inference system (ANFIS) for long range forecast of AISMR. The NCEP/NCAR reanalysis data of temperature, zonal and meridional wind at different pressure levels have been taken to construct the input matrix of ANFIS. The membership of the input parameters for AISMR as high, medium or low is estimated with trapezoidal membership function. The fuzzified standardized input parameters and the de-fuzzified target output are trained with artificial neural network models. The forecast of AISMR with ANFIS is compared with non-hybrid multi-layer perceptron model (MLP), radial basis functions network (RBFN) and multiple linear regression (MLR) models. The forecast error analyses of the models reveal that ANFIS provides the best forecast of AISMR with minimum prediction error of 0.076, whereas the errors with MLP, RBFN and MLR models are 0.22, 0.18 and 0.73 respectively. During validation with observations, ANFIS shows its potency over the said comparative models. Performance of the ANFIS model is verified through different statistical skill scores, which also confirms the aptitude of ANFIS in forecasting AISMR. The forecast skill of ANFIS is also observed to be better than Climate Forecast System version 2. The real-time forecast with ANFIS shows possibility of deficit (65-75 cm) AISMR in the year 2015.

Global warming and South Indian monsoon rainfall-lessons from the Mid-Miocene.

PubMed

Reuter, Markus; Kern, Andrea K; Harzhauser, Mathias; Kroh, Andreas; Piller, Werner E

2013-04-01

Precipitation over India is driven by the Indian monsoon. Although changes in this atmospheric circulation are caused by the differential seasonal diabatic heating of Asia and the Indo-Pacific Ocean, it is so far unknown how global warming influences the monsoon rainfalls regionally. Herein, we present a Miocene pollen flora as the first direct proxy for monsoon over southern India during the Middle Miocene Climate Optimum. To identify climatic key parameters, such as mean annual temperature, warmest month temperature, coldest month temperature, mean annual precipitation, mean precipitation during the driest month, mean precipitation during the wettest month and mean precipitation during the warmest month the Coexistence Approach is applied. Irrespective of a ~ 3-4 °C higher global temperature during the Middle Miocene Climate Optimum, the results indicate a modern-like monsoonal precipitation pattern contrasting marine proxies which point to a strong decline of Indian monsoon in the Himalaya at this time. Therefore, the strength of monsoon rainfall in tropical India appears neither to be related to global warming nor to be linked with the atmospheric conditions over the Tibetan Plateau. For the future it implies that increased global warming does not necessarily entail changes in the South Indian monsoon rainfall.

Regional patterns of the change in annual-mean tropical rainfall under global warming

NASA Astrophysics Data System (ADS)

Huang, P.

2013-12-01

Projection of the change in tropical rainfall under global warming is a major challenge with great societal implications. The current study analyzes the 18 models from the Coupled Models Intercomparison Project, and investigates the regional pattern of annual-mean rainfall change under global warming. With surface warming, the climatological ascending pumps up increased surface moisture and leads rainfall increase over the tropical convergence zone (wet-get-wetter effect), while the pattern of sea surface temperature (SST) increase induces ascending flow and then increasing rainfall over the equatorial Pacific and the northern Indian Ocean where the local oceanic warming exceeds the tropical mean temperature increase (warmer-get-wetter effect). The background surface moisture and SST also can modify warmer-get-wetter effect: the former can influence the moisture change and contribute to the distribution of moist instability change, while the latter can suppress the role of instability change over the equatorial eastern Pacific due to the threshold effect of convection-SST relationship. The wet-get-wetter and modified warmer-get-wetter effects form a hook-like pattern of rainfall change over the tropical Pacific and an elliptic pattern over the northern Indian Ocean. The annual-mean rainfall pattern can be partly projected based on current rainfall climatology, while it also has great uncertainties due to the uncertain change in SST pattern.

Models are likely to underestimate increase in heavy rainfall in regions with high rainfall intensity

NASA Astrophysics Data System (ADS)

Borodina, Aleksandra; Fischer, Erich M.; Knutti, Reto

2017-04-01

Model projections of heavy rainfall are uncertain. On timescales of few decades, internal variability plays an important role and therefore poses a challenge to detect robust model responses. We show that spatial aggregation across regions with intense heavy rainfall events, - defined as grid cells with high annual precipitation maxima (Rx1day), - allows to reduce the role of internal variability and thus to detect a robust signal during the historical period. This enables us to evaluate models with observational datasets and to constrain long-term projections of the intensification of heavy rainfall, i.e., to recalibrate full model ensemble consistent with observations resulting in narrower range of projections. In the regions of intense heavy rainfall, we found two present-day metrics that are related to a model's projection. The first metric is the observed relationship between the area-weighted mean of the annual precipitation maxima (Rx1day) and the global land temperatures. The second is the fraction of land exhibiting statistically significant relationships between local annual precipitation maxima (Rx1day) and global land temperatures over the historical period. The models that simulate high values in both metrics are those that are in better agreement with observations and show strong future intensification of heavy rainfall. This implies that changes in heavy rainfall are likely to be more intense than anticipated from the multi-model mean.

Observational evidence for the relationship between spring soil moisture and June rainfall over the Indian region

NASA Astrophysics Data System (ADS)

KanthaRao, B.; Rakesh, V.

2018-05-01

Understanding the relationship between gradually varying soil moisture (SM) conditions and monsoon rainfall anomalies is crucial for seasonal prediction. Though it is an important issue, very few studies in the past attempted to diagnose the linkages between the antecedent SM and Indian summer monsoon rainfall. This study examined the relationship between spring (April-May) SM and June rainfall using observed data during the period 1979-2010. The Empirical Orthogonal Function (EOF) analyses showed that the spring SM plays a significant role in June rainfall over the Central India (CI), South India (SI), and North East India (NEI) regions. The composite anomaly of the spring SM and June rainfall showed that excess (deficit) June rainfall over the CI was preceded by wet (dry) spring SM. The anomalies in surface-specific humidity, air temperature, and surface radiation fluxes also supported the existence of a positive SM-precipitation feedback over the CI. On the contrary, excess (deficit) June rainfall over the SI and NEI region were preceded by dry (wet) spring SM. The abnormal wet (dry) SM over the SI and NEI decreased (increased) the 2-m air temperature and increased (decreased) the surface pressure compared to the surrounding oceans which resulted in less (more) moisture transport from oceans to land (negative SM-precipitation feedback over the Indian monsoon region).

Influence of Decadal Variability of Global Oceans on South Asian Monsoon and ENSO-Monsoon Relation

NASA Astrophysics Data System (ADS)

Krishnamurthy, Lakshmi

This study has investigated the influence of the decadal variability associated with global oceans on South Asian monsoon and El Nino-Southern Oscillation (ENSO)-monsoon relation. The results are based on observational analysis using long records of monsoon rainfall and circulation and coupled general circulation model experiments using the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM) version 4 model. The multi-channel singular spectrum analysis (MSSA) of the observed rainfall over India yields three decadal modes. The first mode (52 year period) is associated with the Atlantic Multidecadal Oscillation (AMO), the second one (21 year) with the Pacific Decadal Oscillation (PDO) and the third mode (13 year) with the Atlantic tripole. The existence of these decadal modes in the monsoon was also found in the control simulation of NCAR CCSM4. The regionally de-coupled model experiments performed to isolate the influence of North Pacific and North Atlantic also substantiate the above results. The relation between the decadal modes in the monsoon rainfall with the known decadal modes in global SST is examined. The PDO has significant negative correlation with the Indian Monsoon Rainfall (IMR). The mechanism for PDO-monsoon relation is hypothesized through the seasonal footprinting mechanism and further through Walker and Hadley circulations. The model results also confirm the negative correlation between PDO and IMR and the mechanism through which PDO influences monsoon. Both observational and model analysis show that droughts (floods) are more likely over India than floods (droughts) when ENSO and PDO are in their warm (cold) phase. This study emphasizes the importance of carefully distinguishing the different decadal modes in the SST in the North Atlantic Ocean as they have different impacts on the monsoon. The AMO exhibits significant positive correlation with the IMR while the Atlantic tripole has significant negative correlation with the IMR. The AMO influences the Indian monsoon through atmospheric winds related to high summer North Atlantic Oscillation (NAO) mode leading to enhanced moisture flow over the Indian subcontinent. The Atlantic tripole mode affects the rainfall over India by enhancing the moisture flow through the equatorial westerly winds associated with the NAO. The model also simulates the positive and negative relation of AMO and tripole, respectively, with the monsoon rainfall. The model also indicates the enhanced moisture flow over India related to the positive phase of AMO through the equatorial westerly flow. But, for the tripole mode, the model indicates flow of moisture through the Bay of Bengal in contrast to observations where it is through the Arabian Sea. The reason for the absence of decadal mode in IMR inherent to the Indian Ocean is also explored. The SSA on dipole mode index (DMI) index reveals three modes. The first two modes are related to the biennial and canonical ENSO at interannual timescale while the third mode varies on decadal timescale and is related to PDO. The wind regression pattern associated with the PDO-IOD mode shows northeasterly winds enhancing the southeasterly flow from the southeastern Indian Ocean related to the Indian Ocean dipole (IOD) mode. The model also shows the influence of canonical ENSO and PDO influence on IOD, although the variance explained by PDO mode is lower in the model relative to observations.

A review of Tertiary climate changes in southern South America and the Antarctic Peninsula. Part 2: continental conditions

NASA Astrophysics Data System (ADS)

Le Roux, J. P.

2012-03-01

Climate changes in southern South America and the Antarctic Peninsula during the Tertiary show a strong correlation with ocean warming and cooling events, which are in turn related to tectonic processes. During periods of accelerated sea-floor spreading and mid-ocean ridge activity, sea-levels rose so that parts of the continents were flooded and forests were destroyed. However, this was balanced by the large-scale release of CO2 during volcanic outgassing and carbonate precipitation on the continental shelves, which caused rising air temperatures and the poleward expansion of (sub)tropical and temperate forests. Cooling episodes generally caused an increase in the north-south thermal gradient because of an equatorward shift in climate belts, so that the Westerly Winds intensified and brought higher rainfall to the lower latitudes. An increase in wind-blown dust caused temperatures to drop further by reflecting sunlight back into space. The rising Andes Range had a marked influence on climate patterns. Up to the middle Miocene it was still low enough to allow summer rainfall to reach central and north-central Chile, but after about 14 Ma it rose rapidly and effectively blocked the spill-over of moisture from the Atlantic Ocean and Amazon Basin. At this time, the cold Humboldt Current was also established, which together with the Andes helped to create the "Arid Diagonal" of southern South America stretching from the Atacama Desert to the dry steppes of Patagonia. This caused the withdrawal of subtropical forests to south-central Chile and the expansion of sclerophytic vegetation to central Chile. However, at the same time it intercepted more rain from the northeast, causing the effect of the South American monsoon to intensify in northwestern Argentina and southern Bolivia, where forest communities presently occur. In Patagonia, glaciation started as early as 10.5 Ma, but by 7 Ma had become a prominent feature of the landscape and continued apparently uninterruptedly into the Pleistocene. The Antarctic Peninsula saw its first mountain glaciation between 45 and 41 Ma, with major ice sheet expansion commencing at about 34 Ma. Isolated stands of Nothofagus forests were still present in low-lying areas, suggesting that the glaciers were initially wet-based, but dry-based glaciers were established at around 8 Ma. Although temperatures rose briefly during the Messinian-Pliocene transition, causing sub-Antarctic flora to retreat to higher elevations of the Transantarctic Mountains, the present cold polar conditions were finally established by about 3 Ma.

Precontact vegetation and soil nutrient status in the shadow of Kohala Volcano, Hawaii

NASA Astrophysics Data System (ADS)

Chadwick, Oliver A.; Kelly, Eugene F.; Hotchkiss, Sara C.; Vitousek, Peter M.

2007-09-01

Humans colonized Hawaii about 1200 years ago and have progressively modified vegetation, particularly in mesic to dry tropical forests. We use δ 13C to evaluate the contribution of C 3 and C 4 plants to deep soil organic matter to reconstruct pre-human contact vegetation patterns along a wet to dry climate transect on Kohala Mountain, Hawaii Island. Precontact vegetation assemblages fall into three distinct zones: a wet C 3 dominated closed canopy forest where annual rainfall is > 2000 mm, a dry C 4 dominated grassland with annual rainfall < 500 mm, and a broad transition zone between these communities characterized by either C 3 trees with higher water-use efficiency than the rainforest trees or C 3 trees with a small amount of C 4 grasses intermixed. The likelihood of C 4 grass understory decreases with increasing rainfall. We show that the total concentration of rock-derived nutrients in the < 2-mm soil fraction differs in each of these vegetation zones. Nutrient losses are driven by leaching at high rainfall and by plant cycling and wind erosion at low rainfall. By contrast, nutrients are best preserved in surface soils of the intermediate rainfall zone, where rainfall supports abundant plant growth but does not contribute large amounts of water in excess of evapotranspiration. Polynesian farmers exploited these naturally enriched soils as they intensified their upland agricultural systems during the last three centuries before European contact.

Seasonal influence of ENSO on the Atlantic ITCZ and equatorial South America

NASA Astrophysics Data System (ADS)

Münnich, M.; Neelin, J. D.

2005-11-01

In late boreal spring, especially May, a strong relationship exists in observations among precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ), and eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA). A chain of correlations of equatorial Pacific SSTA, western equatorial Atlantic wind stress (WEA), equatorial Atlantic SSTA, sea surface height, and precipitation supports a causal chain in which El Niño/Southern Oscillation (ENSO) induces WEA stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain. This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic. The equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.

Assessment of ozone variations and meteorological effects in an urban area in the Mediterranean Coast.

PubMed

Dueñas, C; Fernández, M C; Cañete, S; Carretero, J; Liger, E

2002-11-01

Ozone concentrations are valuable indicators of possible health and environmental impacts. However, they are also used to monitor changes and trends in the sources of both ozone and its precursors. For this purpose, the influence of meteorological variables is a confusing factor. This study presents an analysis of a year of ozone concentrations measured in a coastal Spanish city. Firstly, the aim of this study was to perceive the daily, monthly and seasonal variation patterns of ozone concentrations. Diurnal cycles are presented by season and the fit of the data to a normal distribution is tested. In order to assess ozone behaviour under temperate weather conditions, local meteorological variables (wind direction and speed, temperature, relative humidity, pressure and rainfall) were monitored together with ozone concentrations. The main relationships we could observe in these analyses were then used to obtain a regression equation linking diurnal ozone concentrations in summer with meteorological parameters.

Comparison of WRF local and nonlocal boundary layer Physics in Greater Kuala Lumpur, Malaysia

NASA Astrophysics Data System (ADS)

Ooi, M. C. G.; Chan, A.; Kumarenthiran, S.; Morris, K. I.; Oozeer, M. Y.; Islam, M. A.; Salleh, S. A.

2018-02-01

The urban boundary layer (UBL) is the internal advection layer of atmosphere above urban region which determines the exchanges of momentum, water and other atmospheric constituents between the urban land surface and the free troposphere. This paper tested the performance of three planetary boundary layer (PBL) physics schemes of Weather Research and Forecast (WRF) software to ensure the appropriate representation of vertical structure of UBL in Greater Kuala Lumpur (GKL). Comparison was conducted on the performance of respective PBL schemes to generate vertical and near-surface weather profile and rainfall. Mellor-Yamada- Janjíc (MYJ) local PBL scheme coupled with Eta MM5 surface layer scheme was found to predict the near-surface temperature and wind profile and mixing height better than the nonlocal schemes during the intermonsoonal period with least influences of the synoptic background weather.

Heinrich Events as an integral part of glacial-interglacial climate dynamics

NASA Astrophysics Data System (ADS)

Barker, S.; Knorr, G.; Zhang, X.; Gong, X.; Lohmann, G.; Bazin, L.

2017-12-01

Since their discovery in the 1980s Heinrich Events have provided a playground for climate scientists trying to understand the interactions between ice sheets and the ocean. Subsequently it has become clear that these interactions extend to almost all parts of the global climate system, from temperature, winds and rainfall to deep ocean currents and atmospheric CO2. Furthermore it remains unclear as to whether these dramatic events are a cause or consequence (or both) of regional to global perturbations in a range of parameters, including meridional overturning circulation within the Atlantic. Here we will discuss some of these aspects to highlight ongoing and future research related to Heinrich events and abrupt change more generally. We will discuss some of the possible triggers for H-events, including abrupt versus more gradual forcing mechanisms and conversely the potential influence of such events on the wider climate system, including deglacial climate change.

Pollen Concentration in the Atmosphere of Abha City, Saudi Arabia and its Relationship with Meteorological Parameters

NASA Astrophysics Data System (ADS)

Alwadie, Hussein M.

A qualitative and quantitative evaluation of pollen concentration in the atmosphere of Abha city, Saudi Arabia with the relation to meteorological parameters is presented. Investigations were undertaken from January to December 2006 using a Burkard 7 day volumetric spore trap. A total of 6,492 pollen grains m-3 belonging to 50 pollen taxa was detected. Poaceae represented 55.1% of total pollen, Leguminosae (11.7%), Compositae (6.1%), Solanaceae (4.6%) and Cupressaceae (4.2%). Pollen grains were found throughout the year. July represented the highest peak of pollen number and also the highest pollen taxa. The monthly variation of pollen taxa and their relationship to meteorological parameters were investigated. It was found that the pollen concentration is positively correlated with temperature and negatively correlated with rainfall, relative humidity and wind velocity. May-September represented the months of highest pollen number (95% of total pollen).