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Sample records for precipitation isotope spatial

  1. Fine-Scale Spatial Variability of Precipitation, Soil, and Plant Water Isotopes

    NASA Astrophysics Data System (ADS)

    Goldsmith, G. R.; Braun, S.; Romero, C.; Engbersen, N.; Gessler, A.; Siegwolf, R. T.; Schmid, L.

    2015-12-01

    Introduction: The measurement of stable isotope ratios of water has become fundamental in advancing our understanding of environmental patterns and processes, particularly with respect to understanding the movement of water within the soil-plant-atmosphere continuum. While considerable research has explored the temporal variation in stable isotope ratios of water in the environment, our understanding of the spatial variability of these isotopes remains poorly understood. Methods: We collected spatially explicit samples of throughfall and soil water (n=150 locations) from a 1 ha plot delineated in a mixed deciduous forest in the northern Alps of Switzerland. We complemented this with fully sunlit branch and leaf samples (n = 60 individuals) collected from Picea abies and Fagus sylvatica between 14:00 and 16:00 on the same day by means of a helicopter. Soil and plant waters were extracted using cryogenic vacuum distillation and all samples were analyzed for δ18O using an isotope ratio mass spectrometer. Results: The mean δ18O of throughfall (-3.3 ± 0.8‰) indicated some evaporative enrichment associated with passage through the canopy, but this did not significantly differ from the precipitation collected in nearby open sites (-4.05‰). However, soil was depleted (-7.0 ± 1.8‰) compared to throughfall and there was no significant relationship between the two, suggesting that the sampling for precipitation inputs did not capture all the sources (e.g. stream water, which was -11.5‰) contributing to soil water δ18O ratios. Evaporative enrichment of δ18O was higher in leaves of Fagus (14.8 ± 1.8‰) than in leaves of Picea (11.8 ± 1.7‰). Sampling within crowns of each species (n = 5 branches each from 5 individuals) indicated that variability in a single individual is similar to that among individuals. Discussion: Stable isotopes of water are frequently engaged for studies of ecohydrology, plant ecophysiology, and paleoclimatology. Our results help

  2. Controls over spatial and seasonal variations on isotopic composition of the precipitation along the central and eastern portion of Brazil.

    PubMed

    Gastmans, Didier; Santos, Vinícius; Galhardi, Juliana Aparecida; Gromboni, João Felipe; Batista, Ludmila Vianna; Miotlinski, Konrad; Chang, Hung Kiang; Govone, José Silvio

    2017-10-01

    Based on Global Network Isotopes in Precipitation (GNIP) isotopic data set, a review of the spatial and temporal variability of δ(18)O and δ(2)H in precipitation was conducted throughout central and eastern Brazil, indicating that dynamic interactions between Intertropical and South Atlantic Convergence Zones, Amazon rainforest, and Atlantic Ocean determine the variations on the isotopic composition of precipitation over this area. Despite the seasonality and latitude effects observed, a fair correlation with precipitation amount was found. In addition, Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) air mass back trajectories were used to quantify the factors controlling daily variability in stable isotopes in precipitation. Through a linear multiple regression analysis, it was observed that temporal variations were consistent with the meteorological parameters derived from HYSPLIT, particularly precipitation amount along the trajectory and mix depth, but are not dependent on vapour residence time in the atmosphere. These findings also indicate the importance of convective systems to control the isotopic composition of precipitation in tropical and subtropical regions.

  3. Spatial and temporal long-term variation of environmental isotopes composition of precipitation and climate change in Azores Archipelago (Portugal)

    NASA Astrophysics Data System (ADS)

    Antunes, P.; Boutt, D. F.; Rodrigues, F.

    2014-12-01

    Azores is located in the middle North Atlantic Ocean, between the latitudes 37º-40ºN and longitudes 25º-31º W and are divided into three geographical groups (Western, Central and Eastern Group). Since February 2012 until January 2014, it was install rain water collectors in Terceira and São Miguel Islands to collect monthly meteoric water. GNIP data was incorporated for the long term study. The main goal of the study was to determine spatial and temporal isotopic variations of meteoric water and long-term changes of isotopic composition related with climate change. Determination of environmental isotopes can be a valuable tool to understand the interconnections among climate, hydrology and water resources at local scale for further studies. Azores Local Meteoric Water line can be defined as δ2H = 6.84δ18O + 7.51 (R2 = 0.85). The δ18O annually average value in Azores is in accordance with the world-wide distribution based on the GNIP data set. Current monthly distribution patterns of δ18O and δH concentrations in meteoric water shows a close relation among surface air temperature and amount precipitation. The slope of the linear fit between δ18O concentration in precipitation and temperature is 0.27‰/ºC for South station (Terceira Island). Data show a depletion of isotopic composition of precipitation that coincides with the seasonal occurrence of the frequent crossing of low pressure systems associated with the polar front. The highest values of d-excess are related with storms and are possible to identify different values between North and South stations related with the amount of precipitation, orography and the relative humidity. Short sampling interval during the wet season shows a large variation in isotopic composition of precipitation. Long term sampling reveals an increase of δ18O concentration values in precipitation that coincides with the temperature increase at the same period. The decreases of d-excess values suggest a drop in the amount

  4. Spatial analysis of annual mean stable isotopes in precipitation across Japan based on an intensive observation period throughout 2013.

    PubMed

    Ichiyanagi, Kimpei; Tanoue, Masahiro

    2016-01-01

    Spatial distribution of annual mean stable isotopes in precipitation (δ(18)O, δ(2)H) was observed at 56 sites across Japan throughout 2013. Annual mean δ(18)O values showed a strong latitude effect, from -12.4 ‰ in the north to -5.1 ‰ in the south. Annual mean d-excess values ranged from 8 to 21 ‰, and values on the Sea of Japan side in Northern and Eastern Japan were relatively higher than those on the Pacific Ocean side. The local meteoric water line (LMWL) and isotope effects were based on the annual mean values from all sites across Japan as divided into distinct regions: the Sea of Japan side to the Pacific Ocean side and Northeastern to Southwestern Japan. Slopes and intercepts of LMWL ranged from 7.4 to 7.8 and 9.8 to 13.0, respectively. Slopes for latitude, altitude, and temperature effects ranged from -0.27 to -0.48 ‰/°N, -0.0034 to -0.0053 ‰/m, and 0.36 to 0.46 ‰/°C, respectively, with statistically significance at the 99 % level. However, there was no precipitation amount effect. From the result of a multiple regression analysis, the empirical formula of annual mean δ(18)O in precipitation from latitude and altitude for all sites across Japan was determined to be δ(18) O = -0.348 (LAT) - 0.00307 (ALT) + 4.29 (R(2) = 0.59). Slopes for latitude and altitude ranged from - 0.28 to - 0.51, and - 0.0019 to - 0.0045, respectively. Even though site distribution was uneven, these equations are the first trial estimation for annual mean stable isotopes in precipitation across Japan. Further research performed on the monthly basis is required to elucidate factors controlling the spatiotemporal variability of stable isotopes in precipitation across Japan.

  5. Seasonal and spatial variations of 17Oexcess and dexcess in Antarctic precipitation: Insights from an intermediate complexity isotope model

    NASA Astrophysics Data System (ADS)

    Schoenemann, Spruce W.; Steig, Eric J.

    2016-10-01

    An intermediate complexity model (ICM) is used to investigate the sensitivity of water isotope ratios in precipitation, including 17Oexcess, to climate variations in the Southern Hemisphere. The ICM is forced with boundary conditions from seasonal National Centers for Environmental Prediction/Department of Energy II reanalysis data. Perturbations to the surface temperature and humidity fields are used to investigate the isotopic sensitivity. The response of 17Oexcess to a uniform temperature change is insignificant over the ocean, while there is a large magnitude response over the ice sheet, particularly in East Antarctica. A decrease of ocean surface relative humidity produces increased 17Oexcess and dexcess, with a coherent response over both the ocean and Antarctica. For interior East Antarctica, the model simulates a seasonal cycle in 17Oexcess that is positively correlated with δ18O and of large magnitude ( 50 per meg), consistent with the observations from Vostok. The seasonal cycle in 17Oexcess for interior West Antarctica is predicted to be considerably smaller in magnitude (12 per meg), and is negatively correlated with δ18O, consistent with new data from a firn core near the West Antarctic Ice Sheet Divide site. Over the ocean, the ICM predicts much smaller seasonal cycles in 17Oexcess. Oceanic source changes (i.e., humidity) are insufficient to explain the amplitude of the simulated seasonal cycle over the Antarctic continent. Spatial differences in the seasonal response of 17Oexcess to local temperature reflect the balance of equilibrium and kinetic fractionation during snow formation.

  6. Spatial variability of environmental isotope and chemical content of precipitation in Jordan and evidence of slight change in climate

    NASA Astrophysics Data System (ADS)

    Bajjali, William

    2012-12-01

    The spatial variability of the δ18O and δD compositions of rain is attributed to variations in amount of precipitation (PPT), altitude effect, and air masses originating from different sources. Air masses that enter the area passing the Mediterranean Sea result in higher d-excess. The cold and dry continental air masses originating from the European continent come in contact with the warm Mediterranean Sea water, resulting in rapid evaporation and large scale convergence. The low d-excess value is less than 16 ‰ and associated with air masses that cross over the North African continent and controlled by a local orographic effect. The change in isotopic composition of δ18O in PPT with altitude is -0.15 ‰ per 100 m. A statistical model confirms that a slight decrease in annual average precipitation has occurred since 1988 and attributed to a minor change in climate. The current level of tritium in rain corresponds to the average level of tritium in the atmosphere. Rabba station recorded a twofold higher tritium concentration in 1995 than the other stations, which may be from leakage from a nuclear station in Israel. The chemistry of rainwater demonstrates a wide range of salinity (100-600 mg/l). The lowest solute concentrations are found at high elevations, and the highest solute concentrations are found in the eastern desert and the Jordan Rift valley. The salinity of rain is affected by desert dust, aerosols, amounts of PPT, and the direction of rain fronts. The aerosols and windblown soil are the most prevailing as the country is confined between three seas and the outcrop surficial geology is mainly sedimentary rocks.

  7. Stable isotopic compositions in Australian precipitation

    NASA Astrophysics Data System (ADS)

    Liu, Jianrong; Fu, Guobin; Song, Xianfang; Charles, Stephen P.; Zhang, Yinghua; Han, Dongmei; Wang, Shiqin

    2010-12-01

    Stable deuterium (δD) and oxygen-18 (δ18O) isotopes in 1962 to 2002 precipitation from the seven Australian stations of the Global Network of Isotopes in Precipitation (GNIP) were used to investigate isotope characteristics including temporal and spatial distributions across different regions of Australia. On the basis of 1534 samples, the local meteoric water line (LMWL) was established as δD = 7.10δ18O + 8.21. δ18O showed a depletion trend from north and south to central Australia (a continental effect) and from west to east. Precipitation amount effects were generally greater than temperature effects, with quadratic or logarithmic correlations describing δ/T and δ/P better than linear relationships. Nonlinear stepwise regression was used to determine the significant meteorological control factors for each station, explaining about 50% or more of the δ18O variations. Geographical control factors for δ18O were given by the relationship δ18O (‰) = -0.005 longitude (°) - 0.034 latitude (°)-0.003 altitude (m) - 4.753. Four different types of d-excess patterns demonstrated particular precipitation formation conditions for four major seasonal rainfall zones. Finally, wavelet coherence (WTC) between δ18O and SOI confirmed that the influence of ENSO decreased from east and north to west Australia.

  8. Precipitation Stable Isotopes Indicate Hydroclimatic Change Since 1965

    NASA Astrophysics Data System (ADS)

    Putman, A.; Bowen, G. J.

    2016-12-01

    Changes to the global hydrologic cycle resulting from thermodynamic and dynamic climate change include increased specific humidity in the atmosphere and expansion of the Hadley circulation cell. The spatial and seasonal distribution of precipitation change in response to these global-scale phenomena is heterogeneous due to topography, land mass distribution, and evapotranspiration contributions to precipitation. Because stable isotopes of oxygen and hydrogen (δ18O and δ2H) in precipitation reflect the thermodynamic conditions during evaporation and condensation, as well as the dynamics of water vapor transport, they provide a promising tool for investigating mechanistic links between changes in precipitation patterns and the dynamics of climate change. To investigate the temporal and spatial change in precipitation, we leveraged a database containing measurements of δ18O and δ2H in precipitation, compiled from the Global Network of Isotopes in Precipitation, regional networks, and individual sites. The dataset includes 80,915 monthly average isotope data from 1073 sites globally, spanning the years 1961 to 2015. From the site-specific raw timeseries, summer (Jun, Jul, Aug) and winter (Dec, Jan, Feb) precipitation-weighted, ENSO-neutral average values were calculated for two 15-year time periods: 1965-1980 and 2000-2015. The site averages were converted to a global gridded surface using the geostatistical interpolation technique employed by IsoMAP. Multi-decadal precipitation isotope ratio trends estimated from the two surfaces are up to +/- 0.32 ‰ yr-1 in summer and +/- 0.24 ‰ yr-1 in winter for δ18O. Although significant spatial complexity exists in the responses, overall we observe enrichment of the heavy isotopes in tropical precipitation and depletion in the mid-latitudes in both seasons, and heavy-isotope enrichment (depletion) in the winter (summer) within the Arctic. The observed isotopic change does not consistently match that expected from modern

  9. Intrastorm Isotopic Variation in Precipitation in Midlatitude Cyclones

    NASA Astrophysics Data System (ADS)

    Faiia, A. M.; Vishnevskiy, M.; Feng, X.; Posmentier, E. S.

    2010-12-01

    Variation of stable isotopes in precipitation has been used to understand the earth’s climate for many decades. Typically, these measurements are made on monthly or even annual accumulations of precipitation. Large intrastorm variation in isotopic ratio was observed during the very early days of isotopic research (Epstein, 1954), and the focus of a limited number of studies (e.g. Gedzelman and Lawrence, 1982; Lawrence et al, 1998; Coplen et al, 2008; Rao et al, 2008; Barras and Simmonds, 2009), but the mechanisms controlling this variation are not well characterized. Measuring isotopic variation on intrastorm timescales will allow for a better understanding of atmospheric and hydrologic processes occurring on the comparable scale both spatially and temporally. As an annual record of precipitation is made up of individual storms, it is important to understand what controls the variation. Although there is a correlation between temperature and isotopic ratios over yearly timescales at mid- to high-latitudes, that relationship is weak or breaks down on smaller timescales. Several studies have observed links between synoptic frontal systems and changes in the isotopic ratio of precipitation on daily or whole event timescales (Lawrence et al 1982; Gedzelman et al, 1997; Trebel et al 2005; Pang et al, 2006; Zhang et al, 2007; Price et al, 2008). This work intended to build on earlier understanding of within storm isotopic variations by extending both sampling and conceptual analysis to a larger number of storms collected over a nearly two-year period. Precipitation samples were collected in Hanover, NH every 0.16 inch of rain. Extremely large changes in the isotopic ratio are seen within the span of several hours. Variation within storms is as large as the seasonal variation observed. We have examined the frontal systems present during the storms to understand the causes of these isotopic shifts. Our analysis has shown that storms with the largest isotopic changes are

  10. Relation between isotopic composition of precipitation and atmospheric circulation patterns

    NASA Astrophysics Data System (ADS)

    Brenčič, Mihael; Kononova, Nina K.; Vreča, Polona

    2015-10-01

    Precipitation generating processes depend on atmospheric circulation patterns and consequently it is expected that its water stable isotopic composition of hydrogen and oxygen is related to them. Precipitation generated at similar atmospheric circulation patterns should have similar empirical distribution of δ2H and δ18O values. Mathematical model based on the linear combination of δ2H and δ18O values and on precipitation amount weighted average related to elementary air circulation mechanisms - ECM is proposed. The model enables estimation of average δ2H and δ18O values and their standard deviation for the precipitation generated at distinctive atmospheric circulation patterns. Approach in which atmospheric circulation patterns were classified as ECM based on the Dzerdzeevskii classification was applied. Application of the model is illustrated on the long term precipitation record from Ljubljana GNIP station Slovenia. Estimated values of the parameters for empirical distributions of δ2H and δ18O of each ECM subtype have shown that calculated estimates are reasonable. Further applications of the proposed model enable new insight into the understanding of isotopes spatial and temporal distribution in precipitation important also for better understanding of climate proxies.

  11. A high-resolution study of isotopic compositions of precipitation

    NASA Astrophysics Data System (ADS)

    Lee, Jeonghoon; Kim, Songyi; Han, Yeongcheol; Oh, Yoon Seok; Kim, Young-Hee; Kim, Hyerin; Ham, Ji-Young; Choi, Hye-Bin; Na, Un-Sung; Koh, Dong-Chan

    2015-04-01

    Isotopic compositions of precipitation have been used to understand moisture transport in the atmosphere and interactions between precipitation and groundwater. Isotopic compositions of speleothems and ice cores, so called, "paleoarchives", can be utilized to interpret climate of the past and global circulation models (GCMs), which are able to explain the paleoarchives, can be validated by the precipitation isotopes. The developments of stable isotope analyzers make high-resolution isotopic studies feasible and a high-resolution study of precipitation isotopes is needed. For this study, precipitation samples were collected for every 5 to 15 minutes, depending on precipitation rates, using an auto-sampler for precipitation isotopes near coastal area. The isotopic compositions of precipitation range from -5.7‰ (-40.1‰)) to -10.8‰ (-74.3‰)) for oxygen (hydrogen). The slope of δ18O-δD diagram for the whole period is 6.8, but that of each storm is 5.1, 4.2, 7.9 and 7.7, respectively. It indicates that evaporation occurred during the first two storms, while the latter two storms did not experience any evaporation. The isotopic fractionations of precipitation has significant implications for the water cycle and high-resolution data of precipitation isotopes will be needed for the future studies related to the precipitation isotopes.

  12. Long-term monitoring of stable isotopic compositions of precipitation over volcanic island, Jeju, Korea

    NASA Astrophysics Data System (ADS)

    Kim, Young-Hee; Koh, Dong-Chan; Park, Won-Bae; Bong, Yeon-Sik; Lee, Kwang-Sik; Lee, Jeonghoon

    2015-04-01

    Stable isotopic compositions of precipitation can be widely used to understand moisture transport in the atmosphere, proxies for paleoclimate and interactions between groundwater and precipitation. Over Jeju volcanic island, located southwest of the Korean Peninsula, precipitation penetrated directly into the highly permeable aquifer is the main source of groundwater. In this study, long-term stable isotopic compositions of precipitation over Jeju Island are characterized to describe spatial and temporal patterns for hydrology and paleoclimate. At fifteen sites from September 2000 to December 2003, precipitation samples were collected and analyzed by Isotope Ratio Mass Spectrometer at the Korea Basic Science Institute. Compared to Lee et al. (2003), the two seasonal local meteoric water lines widen, which may change the relative contributions of winter and summer season precipitation to the groundwater recharge. The precipitation isotopes are inversely correlated with precipitation amount in summer, whereas they do not show a strong correlation with surface air temperature. The precipitation isotopes monthly averaged relatively show a periodic function (R2=0.63 and 0.40 for hydrogen and oxygen, respectively), and deuterium excess (d-excess=δD-8×δ18O) shows a strong pattern of quadratic function (R2=0.97), which is related to a seasonal change of air masses. Altitude effect of precipitation isotopes, which can be a clue to reveal sources of groundwater, can be observed in every aspect of the volcanic island (for the oxygen isotope, -0.14‰ for east and west, -0.18‰ for north and -0.085‰ for south per 100 m). Our analysis of precipitation isotopes will be helpful to provide limitations and opportunities for paleoclimate reconstruction using isotopic proxies and water movement from atmosphere to subsurface.

  13. Atmospheric circulation is reflected in precipitation isotope gradients over the conterminous United States

    NASA Astrophysics Data System (ADS)

    Liu, Zhongfang; Bowen, Gabriel J.; Welker, Jeffrey M.

    2010-11-01

    The stable isotopic (δ18O and δ2H) composition of meteoric precipitation integrates information on the history of water fluxes to, from, and between air masses as they traverse the continents. The development of new methods relating isotopic data to water cycle processes will increase our ability to understand this system and its response to natural and anthropogenic forcing. Here we present an analysis of 2 years (1992-1993) of precipitation isotope data from 73 sites across the conterminous United States. We focus on patterns in the spatial precipitation isotope gradients (rate and direction of isotopic change in space), a metric which we suggest reflects two factors: (1) variation in the balance of rainout and land-surface recycling for air masses moving across the continent and (2) the spatial juxtaposition of air masses carrying moisture of differing origin and rainout history (e.g., Pacific versus Gulf of Mexico moisture). We demonstrate that the position of zones of particularly high precipitation isotope slopes correspond to the time-averaged position of air mass boundaries and to regions where prevailing moisture transport trajectories interact with orographic barriers. Differences in the location of high-slope zones between winter and summer seasons and between the same seasons in 1992 and 1993 can be related to differences in circulation and weather patterns. These results suggest new opportunities for the interpretation of precipitation, vapor, and paleoclimate water isotope data in the context of regional climate dynamics through spatial analysis.

  14. Spatial distribution of precipitation extremes in Norway

    NASA Astrophysics Data System (ADS)

    Verpe Dyrrdal, Anita; Skaugen, Thomas; Lenkoski, Alex; Thorarinsdottir, Thordis; Stordal, Frode; Førland, Eirik J.

    2015-04-01

    Estimates of extreme precipitation, in terms of return levels, are crucial in planning and design of important infrastructure. Through two separate studies, we have examined the levels and spatial distribution of daily extreme precipitation over catchments in Norway, and hourly extreme precipitation in a point. The analyses were carried out through the development of two new methods for estimating extreme precipitation in Norway. For daily precipitation we fit the Generalized Extreme Value (GEV) distribution to areal time series from a gridded dataset, consisting of daily precipitation during the period 1957-today with a resolution of 1x1 km². This grid-based method is more objective and less manual and time-consuming compared to the existing method at MET Norway. In addition, estimates in ungauged catchments are easier to obtain, and the GEV approach includes a measure of uncertainty, which is a requirement in climate studies today. Further, we go into depth on the debated GEV shape parameter, which plays an important role for longer return periods. We show that it varies according to dominating precipitation types, having positive values in the southeast and negative values in the southwest. We also find indications that the degree of orographic enhancement might affect the shape parameter. For hourly precipitation, we estimate return levels on a 1x1 km² grid, by linking GEV distributions with latent Gaussian fields in a Bayesian hierarchical model (BHM). Generalized linear models on the GEV parameters, estimated from observations, are able to incorporate location-specific geographic and meteorological information and thereby accommodate these effects on extreme precipitation. Gaussian fields capture additional unexplained spatial heterogeneity and overcome the sparse grid on which observations are collected, while a Bayesian model averaging component directly assesses model uncertainty. We find that mean summer precipitation, mean summer temperature, latitude

  15. Water Isotopes in Precipitation: Data/Model Comparison for Present-Day and Past Climates

    NASA Technical Reports Server (NTRS)

    Jouzel, J.; Hoffmann, G.; Masson, V.

    1998-01-01

    Variations of HDO and H2O-18 concentrations are observed in precipitation both on a geographical and on a temporal basis. These variations, resulting from successive isotopic fractionation processes at each phase change of water during its atmospheric cycle, are well documented through the IAEA/WMO network and other sources. Isotope concentrations are, in middle and high latitudes, linearly related to the annual mean temperature at the precipitation site. Paleoclimatologists have used this relationship to infer paleotemperatures from isotope paleodata extractable from ice cores, deep groundwater and other such sources. For this application to be valid, however, the spatial relationship must also hold in time at a given location as the location undergoes a series of climatic changes. Progress in water isotope modeling aimed at examining and evaluating this assumption has been recently reviewed with a focus on polar regions and, more specifically, on Greenland. This article was largely based on the results obtained using the isotopic version of the NASA/GISS Atmospheric General Circulation Model (AGCM) fitted with isotope tracer diagnostics. We extend this review in comparing the results of two different isotopic AGCMs (NASA/GISS and ECHAM) and in examining, with a more global perspective, the validity of the above assumption, i.e. the equivalence of the spatial and temporal isotope-temperature relationship. We also examine recent progress made in modeling the relationship between the conditions prevailing in moisture source regions for precipitation and the deuterium-excess of that precipitation.

  16. Verification of the isotopic composition of precipitation simulated by a regional isotope circulation model over Japan.

    PubMed

    Tanoue, Masahiro; Ichiyanagi, Kimpei; Yoshimura, Kei

    2016-01-01

    The isotopic composition (δ(18)O and δ(2)H) of precipitation simulated by a regional isotope circulation model with a horizontal resolution of 10, 30 and 50 km was compared with observations at 56 sites over Japan in 2013. All simulations produced reasonable spatio-temporal variations in δ(18)O in precipitation over Japan, except in January. In January, simulated δ(18)O values in precipitation were higher than observed values on the Pacific side of Japan, especially during an explosively developing extratropical cyclone event. This caused a parameterisation of precipitation formulation about the large fraction of precipitated water to liquid detrained water in the lower troposphere. As a result, most water vapour that transported from the Sea of Japan precipitated on the Sea of Japan side. The isotopic composition of precipitation was a useful verification tool for the parameterisation of precipitation formulation as well as large-scale moisture transport processes in the regional isotope circulation model.

  17. Tritium and Stable Isotopes of Precipitation and Surface Water in California

    NASA Astrophysics Data System (ADS)

    Harms, P.; Moran, J. E.; Visser, A.; Esser, B. K.

    2014-12-01

    Tritium (3H) and stable isotopes (2H and 18O) are effective natural tracers of water molecules through the hydrologic system. The strong topographic gradient in California results in distinct isotopic signatures that are particularly effective in watershed studies. Past studies of meteoric tritium distribution within the United States have focused on large-scale trends, at low spatial resolution. Globally, tritium in precipitation is monitored by the International Atomic Energy Agency contributing to the Global Network of Isotopes in Precipitation (GNIP) database. The two tritium monitoring stations in California contributing to the GNIP database were discontinued in 1976 (Santa Maria) and 1993 (Menlo Park). Surface water studies have focused on time series in major rivers nationwide or localized studies. Our study focuses on high spatial resolution water isotope data collection in California. Over 140 tritium and stable water isotope samples were collected from surface water and direct precipitation during the 2013 Summer/Fall and 2014 Winter/Spring flow regimes and analyzed by helium accumulation and noble gas mass spectrometry. Surface water samples are collected as a proxy for precipitation and to investigate trends related to water residence times. Tritium concentrations in precipitation show strong spatial trends, with higher concentrations at inland high elevation locations. Surface water tritium trends with spatial location (latitude and longitude) and elevation (reflecting the precipitation signal) and distance downstream (reflecting water residence times). A local meteoric water line (MWL) for California is developed from stable isotope data and analyzed in comparison to the global MWL. Results have implications for tritium tracer and water provenance studies.

  18. Spatial patterns of throughfall isotopic composition at the event and seasonal timescales

    Treesearch

    Scott T. Allen; Richard F. Keim; Jeffrey J. McDonnell

    2015-01-01

    Spatial variability of throughfall isotopic composition in forests is indicative of complex processes occurring in the canopy and remains insufficiently understood to properly characterize precipitation inputs to the catchment water balance. Here we investigate variability of throughfall isotopic composition with the objectives: (1) to quantify the spatial variability...

  19. Stable isotopic characteristic of Taiwan's precipitation: A case study of western Pacific monsoon region

    NASA Astrophysics Data System (ADS)

    Peng, Tsung-Ren; Wang, Chung-Ho; Huang, Chi-Chao; Fei, Li-Yuan; Chen, Chen-Tung Arthur; Hwong, Jeen-Lian

    2010-01-01

    relative to winter. The observed spatial and seasonal stable isotopic characteristics in Taiwan's precipitation not only contribute valuable information for regional monsoon research crossing the continent-ocean interface of East Asia, but also can serve as very useful database for local water resources management.

  20. Numerical experiments on the impacts of surface evaporation and fractionation factors on stable isotopes in precipitation

    NASA Astrophysics Data System (ADS)

    Zhang, Xinping; Guan, Huade; Zhang, Xinzhu; Zhang, Wanjun; Yao, Tianci

    2016-06-01

    The isotope enabled atmospheric water balance model is applied to examine the spatial and temporal variations of δ18O in precipitation, amount effect and meteoric water lines (MWL) under four scenarios with different fractionation nature and surface evaporation inputs. The experiments are conducted under the same weather forcing in the framework of the water balance and stable water isotope balance. Globally, the spatial patterns of mean δ18O and global MWLs simulated by four simulation tests are in reasonably good agreement with the Global Network of Isotopes in Precipitation observations. The results indicate that the assumptions of equilibrium fractionation for simulating spatial distribution in mean annual δ18O and the global MWL, and kinetic fractionation in simulating δ18O seasonality are acceptable. In Changsha, four simulation tests all reproduce the observed seasonal variations of δ18O in precipitation. Compared with equilibrium fractionation, the depleted degree of stable isotopes in precipitation is enhanced under kinetic fractionation, in company with a decrease of isotopic seasonality and inter-event variability. The alteration of stable isotopes in precipitation caused by the seasonal variation of stable isotopes in vapour evaporated from the surface is opposite between cold and warm seasons. Four simulations all produce the amount effect commonly observed in monsoon areas. Under kinetic fractionation, the slope of simulated amount effect is closer to the observed one than other scenarios. The MWL for warm and humid climate in monsoon areas are well simulated too. The slopes and intercepts of the simulated MWLs decrease under kinetic fractionation.

  1. Environmental controls on stable isotopes of precipitation in Lanzhou, China: An enhanced network at city scale.

    PubMed

    Chen, Fenli; Zhang, Mingjun; Wang, Shengjie; Qiu, Xue; Du, Mingxia

    2017-12-31

    Stable hydrogen and oxygen isotopes in precipitation are very sensitive to environmental changes, and can record evolution of water cycle. The Lanzhou city in northwestern China is jointly influenced by the monsoon and westerlies, which is considered as a vital platform to investigate the moisture regime for this region. Since 2011, an observation network of stable isotopes in precipitation was established across the city, and four stations were included in the network. In 2013, six more sampling stations were added, and the enhanced network might provide more meaningful information on spatial incoherence and synoptic process. This study focused on the variations of stable isotopes (δ(18)O and δD) in precipitation and the environmental controls based on the 1432 samples in this enhanced network from April 2011 to October 2014. The results showed that the precipitation isotopes had great spatial diversity, and the neighboring stations may present large difference in δD and δ(18)O. Based on the observation at ten sampling sites, an isoscape in precipitation was calculated, and the method is useful to produce isoscape for small domains. The temperature effect and amount effect was reconsidered based on the dataset. Taking meteorological parameters (temperature, precipitation amount, relative humidity, water vapor pressure and dew point temperature) as variables in a multi-linear regression, the result of coefficients for these meteorological parameters were calculated. Some cases were also involved in this study, and the isotopic characteristics during one event or continuous days were used to understand the environmental controls on precipitation isotopes. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Precipitation regime and stable isotopes at Dome Fuji, East Antarctica

    NASA Astrophysics Data System (ADS)

    Dittmann, Anna; Schlosser, Elisabeth; Masson-Delmotte, Valérie; Powers, Jordan G.; Manning, Kevin W.; Werner, Martin; Fujita, Koji

    2016-06-01

    A unique set of 1-year precipitation and stable water isotope measurements from the Japanese Antarctic station, Dome Fuji, has been used to study the impact of the synoptic situation and the precipitation origin on the isotopic composition of precipitation on the Antarctic Plateau. The Antarctic Mesoscale Prediction System (AMPS) archive data are used to analyse the synoptic situations that cause precipitation. These situations are investigated and divided into five categories. The most common weather situation during a precipitation event is an upper-level ridge that extends onto the Antarctic Plateau and causes strong northerly advection from the ocean. Most precipitation events are associated with an increase in temperature and wind speed, and a local maximum of δ18O. During the measurement period, 21 synoptically caused precipitation events caused 60 % of the total annual precipitation, whereas the remaining 40 % were predominantly attributed to diamond dust. By combining the synoptic analyses with 5-day back-trajectories, the moisture source regions for precipitation events were estimated. An average source region around a latitude of 55° S was found. The atmospheric conditions in the source region were used as initial conditions for running a Rayleigh-type isotopic model in order to reproduce the measured isotopic composition of fresh snow and to investigate the influence of the precipitation source region on the isotope ratios. The model represents the measured annual cycle of δ18O and the second-order isotopic parameter deuterium excess reasonably well, but yields on average too little fractionation along the transport/cooling path. While simulations with an isotopic general circulation model (GCM) (ECHAM5-wiso) for Dome Fuji are on average closer to the observations, this model cannot reproduce the annual cycle of deuterium excess. In the event-based analysis, no evidence of a correlation of the measured deuterium excess with the latitude of the

  3. Kinetic and equilibrium Ba isotope fractionation during carbonate precipitation

    NASA Astrophysics Data System (ADS)

    van Zuilen, Kirsten; Mavromatis, Vasileios; Purgstaller, Bettina; Baldermann, Andre; Nägler, Thomas F.; Dietzel, Martin

    2017-04-01

    Variations in stable isotope ratios recorded in carbonates are widely used to reconstruct the physicochemical conditions, e.g., pH, temperature and redox conditions, prevailing at the time of carbonate mineral formation. Knowledge of isotope fractionation factors during mineral precipitation under varying environmental conditions is irremissible for the interpretation of isotope variations in natural sedimentary archives. However, experimentally derived fractionation factors, of for instance Ca isotopes, are often ambiguous and incommensurable due to differences in experimental parameters. Here, Ba isotope fractionation during carbonate mineral formation was investigated [1]. Time-resolved experiments of witherite (BaCO3) precipitation revealed an initial kinetic isotope effect with increasing Δ137/134Ba values of the ambient solution, following Rayleigh fractionation (αwitherite-fluid = 0.99993 ± 0.00004). After precipitation, the witherite crystals remained in contact with the ambient solution for about nine days. During this time, chemical steady state was achieved between solution and witherite; however, the Δ137/134Ba values of the solution decreased. At isotopic equilibrium, the ambient solution and the witherite crystals exhibited identical δ137/134Ba values, within the analytical uncertainty of ±0.04 ‰Ṫhis observation is interpreted as the result of continuous exchange of Ba2+ ions between witherite and solution after initial preferential uptake of the lighter Ba isotopes in the precipitating carbonates. Mass balance calculations indicate that the ion exchange affects several subsurface layers of the crystals. In summary, Ba isotope exchange between carbonate and ambient solution occurs at chemical equilibrium, and pristine isotopic signatures in carbonates may thus be reset at low temperatures. [1] Mavromatis et al. (2016) Geochim. Cosmochim. Acta 190, 72-84.

  4. Assessing Precipitation Isotope Variations during Atmospheric River Events to Reveal Dominant Atmospheric/Hydrologic Processes

    NASA Astrophysics Data System (ADS)

    McCabe-Glynn, S. E.; Johnson, K. R.; Yoshimura, K.; Buenning, N. H.; Welker, J. M.

    2015-12-01

    Extreme precipitation events across the Western US commonly associated with atmospheric rivers (ARs), whereby extensive fluxes of moisture are transported from the subtropics, can result in major damage and are projected by most climate models to increase in frequency and severity. However, they are difficult to project beyond ~ten days and the location of landfall and topographically induced precipitation is even more uncertain. Water isotopes, often used to reconstruct past rainfall variability, are useful natural tracers of atmospheric hydrologic processes. Because of the typical tropical and sub-tropical origins, ARs can carry unique water isotope (δ18O and δ2H, d-excess) signatures that can be utilized to provide source and process information that can lead to improving AR predictions. Recent analysis of the top 10 weekly precipitation total samples from Sequoia National Park, CA, of which 9 contained AR events, shows a high variability in the isotopic values. NOAA Hysplit back trajectory analyses reveals a variety of trajectories and varying latitudinal source regions contributed to moisture delivered to this site, which may explain part of the high variability (δ2H = -150.03 to -49.52 ‰, δ18O = -19.27 to -7.20 ‰, d-excess = 4.1 to 25.8). Here we examine the top precipitation totals occurring during AR events and the associated isotopic composition of precipitation samples from several sites across the Western US. We utilize IsoGSM, an isotope-enabled atmospheric general circulation model, to characterize the hydrologic processes and physical dynamics contributing to the observed isotopic variations. We investigate isotopic influences from moisture source location, AR speed, condensation height, and associated temperature. We explore the dominant controls on spatial and temporal variations of the isotopic composition of AR precipitation which highlights different physical processes for different AR events.

  5. Isotopic variations in precipitation at Bangkok and their climatological significance

    NASA Astrophysics Data System (ADS)

    He, Yuanqing; Pang, Hongxi; Theakstone, W. H.; Zhang, Zhonglin; Lu, Aigang; Gu, Juan

    2006-08-01

    The stable isotopic composition of precipitation from low to mid latitudes contains information about changes of some climatic factors, such as temperature, precipitation and atmospheric circulation patterns. However, the isotopic variations in the area are very complicated because of the combined influences of these factors. Proper interpretation of the patterns of isotopic variations for palaeoclimate reconstructions in this area requires a detailed understanding of these complex stable isotope controls. The isotopic data (18O and 2D) in precipitation at the International Atomic Energy Agency-World Meteorological Organization Bangkok station were collected and analysed because of the relatively long and unbroken isotopic records and the particular geographical location. The isotopic variations at Bangkok have strong seasonal patterns owing to distinct source regions in different seasons. In summer, the remote sources of water there can influence the 18O values significantly, which is verified by the simple Rayleigh model. In winter, the mixing of isotopically distinct air masses with different origins, i.e. the continental and oceanic air masses, accounts for the isotopic variations. In the transition periods of the Asia-Australia monsoon, namely in May and October, the local vapour contribution may play a role in the isotopic ratios. On the interannual time-scale, the influences of El Niño-southern oscillation (ENSO) and the Indian Ocean dipole (IOD) on isotopic composition are examined. The indications are that both the ENSO and IOD indices have a significant correlation with the 18O ratios, and that the 18O ratio in summer rains is significantly more enriched (depleted) during the warm (cold) phase of ENSO/IOD events. All the results suggest that it is useful for us in understanding the water cycling process and may be helpful in palaeoclimate reconstruction in this monsoon region.

  6. Isoscapes: Spatial Pattern in Isotopic Biogeochemistry

    NASA Astrophysics Data System (ADS)

    Bowen, Gabriel J.

    2010-05-01

    Isotope ratios of actively cycled elements vary as a function of the biogeochemical processes in which they participate and the conditions under which those processes occur. The resultant spatiotemporal distribution of isotopes in environmental materials can be predicted using models of isotope-fractionating processes and data describing environmental conditions across space and time, and it has been termed an isoscape, or isotopic landscape. Analysis of isoscapes and comparison of isoscape predictions with observational data have been used to test biogeochemical models, calculate aerially integrated biogeochemical fluxes based on isotope mass balance, and determine spatial connectivity in biogeochemical, ecological, and anthropological systems. Isoscape models of varying quality are available for stable H, C, N, and O isotopes in a range of Earth surface systems, but significant opportunities exist to refine our understanding of biogeochemical cycles and our ability to predict isoscapes through the development of more mechanistic and more comprehensive isoscape models.

  7. Original isotopic composition of water in precipitation by different methods

    NASA Astrophysics Data System (ADS)

    Singh, B. P.

    2016-11-01

    Stable isotopes of 2H and 18O in precipitation are different globally and carry all information about water molecules movement in hydrosphere cycles. Isotopic composition is a function of temperature, relative humidity, and speed of evaporation at different latitudes, longitudes, and altitudes. On the basis of this, we observe local meteoric water line measurements in the plot of δ2H versus δ18O. It will be interesting to know the original isotopic composition (without any modification) in a transition from cloud down to earth in different environmental conditions. This had been done by plotting of slope versus intercept of Local Meteoric Water Line (LMWL) at different altitudes in different years of observations. Intercept of LMWL with Global Meteoric Water Line (GMWL) data taken from the hydrology frame work of Corsica was plotted and it was found that the isotopic composition of water in precipitation by all these methods is same.

  8. Stable isotopic variations in precipitation in Southwest China

    NASA Astrophysics Data System (ADS)

    Zhang, Xinping; Jin, Huijun; Sun, Weizhen

    2006-12-01

    This study analyzes the relationships of stable isotopes in precipitation with temperature, air pressure and humidity at different altitudes, and the potential influencing mechanisms of control factors on the stable isotopes in precipitation in Southwest China. There appear marked negative correlations of the δ 18O in precipitation with precipitation amount, vapor pressure and atmospheric precipitable water (PW) at the Mengzi, Simao and Tengchong stations on the synoptic timescale; the marked negative correlations between the δ 18O in precipitation and the diurnal mean temperature at 400 hPa, 500 hPa, 700 hPa and 850 hPa are different from the temperature effect in middle-high-latitude inland areas. In addition, the notable positive correlation between the δ 18O in precipitation and the dew-point deficit Δ T d at different altitudes is found at the three stations. Precipitation is not the only factor generating an amount effect. Probably, the amount effect is related to the variations of atmospheric circulation and vapor origins. On the annual timescale, the annual precipitation amount weighted-mean δ 18O displays negative correlations not only with annual precipitation but also with annual mean temperature at 500 hPa. It can be deduced that, in the years with an abnormally strong summer monsoon, more warm and wet air from low-latitude oceans is transported northward along the vapor channel located in Southwest China and generates abnormally strong rainfall on the way. Meanwhile, the abnormally strong condensation process will release more condensed latent heat in the atmosphere, and this will lead to a rise of atmospheric temperature during rainfall but a decline of δ 18O in the precipitation. On the other hand, in the years with an abnormally weak summer monsoon, the precipitation and the atmospheric temperature during rainfalls decrease abnormally but the δ 18O in precipitation increases.

  9. What governs the oxygen and hydrogen isotopic composition of precipitation? - A case for varying proportions of isotopically-distinct, convective and stratiform rain fractions

    NASA Astrophysics Data System (ADS)

    Aggarwal, P. K.; araguas Araguas, L.; Belachew, D.; Schumacher, C.; Funk, A. B.; Longstaffe, F. J.; Terzer, S.

    2016-12-01

    Beginning with the pioneering work of Dansgaard in 1953, stable water isotope ratios have been observed to be different in precipitation from different clouds, such as convective showers and continuous frontal rain, hydrologically more or less organized systems, or those with or without `bright bands' in radar reflectivity. The variability in isotope ratios of precipitation has always been interpreted, however, using a Rayleigh distillation framework, with lower isotope ratios resulting from condensation at lower temperatures and/or greater air mass distillation, a lack of below-cloud evaporation or in-cloud re-cycling, etc. Rayleigh distillation based approaches do not account for the fact that tropical and midlatitude precipitation consists of varying proportions of two fundamental rain types - widespread but lower intensity, stratiform and spatially-limited but higher intensity, convective - which form under very different cloud dynamical and microphysical environments. Using rain type fraction and isotope data from a large set of monitoring stations, we will show that differences in cloud processes impart characteristic isotope signatures to the two rain types and that their changing proportions during storm events are primarily responsible for precipitation isotope variability. As a result, isotope ratios can be used to partition precipitation into convective or stratiform rain fractions, which is important for understanding cloud feedbacks and atmospheric circulation response to precipitation, as well as climate impacts on the water cycle. We will also discuss the changing character of tropical and midlatitude precipitation over the past several decades and its implications.

  10. Isotopic composition of precipitation during different atmospheric circulation patterns

    NASA Astrophysics Data System (ADS)

    Brenčič, Mihael; Kononova, Nina; Vreča, Polona

    2016-04-01

    Precipitation generating processes depend on atmospheric circulation patterns and consequently it is expected that its water stable isotopic composition of hydrogen and oxygen is related to them. Precipitation generated at similar atmospheric circulation patterns should have similar empirical distribution of δ2H and δ18O values. There are several approaches in which atmospheric circulation patterns are classified as elementary air circulation mechanisms - ECM; in our approach we have applied Dzerdzeevskii classification. Two types of models of relation between ECM and isotopic composition of precipitation are proposed; first is based on the linear combination of δ2H and δ18O values with precipitation amount weighted average (Brenčič et al., 2015) and the second new one is based on the multiple regression approach. Both approaches make possible also to estimate empirical distributions' dispersion parameters. Application of the models is illustrated on the precipitation records from Ljubljana and Portorož GNIP stations, Slovenia. Estimated values of the parameters for empirical distributions of δ2H and δ18O of each ECM subtype have shown that calculated estimates are reasonable. Brenčič, M., Kononova, N.K., Vreča, P., 2015: Relation between isotopic composition of precipitation and atmospheric circulation patterns. Journal of Hydrology 529, 1422-1432: doi: 10.1016/j.jhydrol.2015.08.040

  11. The Global Network of Isotopes in Precipitation after 55 years: assessing past, present and future developments

    NASA Astrophysics Data System (ADS)

    Terzer, Stefan; Araguas-Araguas, Luis; Wassenaar, Leonard I.; Aggarwal, Pradeep K.

    2015-04-01

    The Global Network of Isotopes in Precipitation (GNIP) is a global observation programme operated by the International Atomic Energy Agency (IAEA), in cooperation with the World Meteorological Organization (WMO) and more than 100 contributing institutions worldwide. GNIP has been the primary repository for baseline stable (δ18O, δ2H) and radioactive (3H) isotope data since its foundation in 1960. The impetus for GNIP was the monitoring of radioactive fallout from atmospheric thermonuclear testing and resulting tritium levels of precipitation, but tritium together with stable isotopes was recognized as a key to understanding hydrological processes. Later, new applications were developed focusing on hydrometeorology and paleoclimatic research. Increasingly, GNIP data are being used more widely in ecological and forensic investigations, e.g. for tracking of migratory animals. The GNIP database comprises more than 135,000 isotopic records (δ18O: 63,000; δ2H: 55,000; 3H: 63,000) of monthly composite precipitation samples from more than 1,000 stations worldwide. About 300 stations are currently active for stable isotopes and ca. 100 for tritium. Data for most of the active stations is available up to 2013. Several national isotopic observation networks (e.g. in Austria, Australia, China or the United States of America) exist besides GNIP, complementing precipitation isotope data at national levels. The spatially and temporally discrete nature of the GNIP dataset induces coverage gaps. Recently, highly-resolved gridded datasets were established to help overcome this deficiency through geostatistical prediction models. These 'isoscape' (isotopic landscapes) are based on combinations of multiple regression and interpolation methods, with a range of parameterization available at regional and global levels. Attempts to bridge the gap between 'one-size-fits-all' global parameterization and improved predictions at regional and local levels led to the establishment of a

  12. Isotopic fractionation of alkali earth metals during carbonate precipitation

    NASA Astrophysics Data System (ADS)

    Yotsuya, T.; Ohno, T.; Muramatsu, Y.; Shimoda, G.; Goto, K. T.

    2014-12-01

    The alkaline earth metals such as magnesium, calcium and strontium play an important role in a variety of geochemical and biological processes. The element ratios (Mg/Ca and Sr/Ca) in marine carbonates have been used as proxies for reconstruction of the past environment. Recently several studies suggested that the study for the isotopic fractionation of the alkaline earth metals in marine carbonates has a potentially significant influence in geochemical research fields (e.g. Eisenhauer et al., 2009). The aim of this study is to explore the influence of carbonate polymorphs (Calcite and Aragonite) and environmental factors (e.g., temperature, precipitation rate) on the level of isotopic fractionation of the alkaline earth metals. We also examined possible correlations between the level of isotopic fractionation of Ca and that of other alkaline earth metals during carbonate precipitation. In order to determine the isotope fractionation factor of Mg, Ca and Sr during carbonate precipitation, calcite and aragonite were synthesized from calcium bicarbonate solution in which the amount of magnesium was controlled based on Kitano method. Calcium carbonates were also prepared from the mixture of calcium chlorite and sodium hydrogen carbonate solutions. The isotope fractionation factors were measured by MC-ICPMS. Results suggested that the level of isotopic fractionation of Mg during carbonate precipitation was correlated with that of Sr and that the change of the carbonate crystal structure could make differences of isotopic fractionations of Mg and Ca, however no difference was found in the case of Sr. In this presentation, the possible mechanism will be discussed.

  13. Controls on the stable isotopes in precipitation and surface waters across the southeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Ren, Wei; Yao, Tandong; Xie, Shiyou; He, You

    2017-02-01

    Constraining temporal and spatial variability in water stable isotopes (δ18O and δD) is requested for interpreting proxy records of paleoclimate/paleoaltimetry. The southeastern Tibetan Plateau (TP) receives large amounts of precipitation in both summer (JJAS) and spring (MAM) and this makes it different from most other parts of the TP where annual precipitation concentrates only in summer. However, our knowledge of controls on precipitation and surface runoff generation in this region is still far from sufficient. In this study, the δ18O and δD of precipitation and stream waters across the southeastern TP were analyzed to investigate moisture sources and empirical isotope-elevation relationships. Herein, seasonal precipitation patterns, moisture trajectories and precipitation isotopes suggest this region is seasonally dominated by the monsoon in summer and the southerlies (from the Bay of Bengal) or a mix of southerlies and westerlies in spring. Spatially, vertical variations in precipitation seasonality exert profound influences on isotopic variability for stream waters. Larger contributions of spring precipitation (with higher δ18O and d-excess (d-excess = δD-8δ18O) compared to summer precipitation) vs. summer precipitation in the surface runoff generation at lower elevations account for the uncommon altitudinal decrease in streamwater d-excess. Such a cause also contributes to the slightly greater vertical lapse rates of streamwater δ18O (-0.28 to -0.48‰/100 m) relative to the Himalayan front. In addition, although a robust δ18O-elevation relationship is demonstrated based upon our measured and other published data on a broad spatial scale (over a 5200 m elevation range), this relationship is found to deviate from the empirical/theoretical pattern in the Himalayan front, which is also caused by the substantial spring precipitation in the southeastern TP. It is suggested that long-term changes in δ18O or δD of paleowater in this region actually

  14. Calcium isotopic fractionation in microbially mediated gypsum precipitates

    NASA Astrophysics Data System (ADS)

    Harouaka, Khadouja; Mansor, Muammar; Macalady, Jennifer L.; Fantle, Matthew S.

    2016-07-01

    Gypsum (CaSO4·2H2O) precipitation experiments were carried out at low pH in the presence of the sulfur oxidizing bacterium Acidithiobacillus thiooxidans. The observed Ca isotopic fractionation (expressed as Δ44/40Cas-f = δ44/40Casolid-δ44/40Cafluid) at the end of each experimental time period (∼50 to 60 days) was -1.41‰ to -1.09‰ in the biotic experiments, -1.09‰ in the killed control, and -1.01‰ to -0.88‰ in the abiotic controls. As there were no strong differences in the solution chemistry and the rate at which gypsum precipitated in the biotic and abiotic controls, we deduce a biological Ca isotope effect on the order of -0.3‰. The isotope effect correlates with a difference in crystal aspect ratios between the biotic experiments (8.05 ± 3.99) and abiotic controls (31.9 ± 8.40). We hypothesize that soluble and/or insoluble organic compounds selectively inhibit crystal growth at specific crystal faces, and that the growth inhibition affects the fractionation factor associated with gypsum precipitation. The experimental results help explain Ca isotopic variability in gypsum sampled from a sulfidic cave system, in which gypsum crystals exhibiting a diversity of morphologies (microcrystalline to cm-scale needles) have a broad range of δ44/40Ca values (∼1.2-0.4‰) relative to the limestone wall (δ44/40Ca = 1.3‰). In light of the laboratory experiments, the variation in Ca isotope values in the caves can be interpreted as a consequence of gypsum precipitation in the presence of microbial organic matter and subsequent isotopic re-equilibration with the Ca source.

  15. Isotopic composition of winter precipitation in Altai foothills

    NASA Astrophysics Data System (ADS)

    Malygina, N. S.; Eirich, A. N.; Papina, T. S.

    2016-11-01

    In recent years, some general circulation models have been improved by using stable water isotopologues, such as HDO (δD) and H2 18O (δ18O). In this paper, the results of a study of the isotopic composition of precipitation sampled in the winter seasons of 2014-2015 and 2015-2016 in Altai foothills are presented. The isotopic composition varied greatly: from -17.4 ‰ to -30.63 ‰ for δ18O and from -132.1 ‰ to -235.0 ‰ for δD in 2014-2015; from -15.9 %„ to -26.8 ‰ for δ18D and from -118.5 ‰ to -207.7 ‰ for δD in 2015-2016. The weighted average values of δ18O and δD for both seasons were close to each other (-21.2 ‰ and -160.1 ‰ for the first season and -20.4 ‰ and -157.5 ‰ for the second season), while the values of dexc differed significantly. A trajectory analysis (by the Hybrid Single Particle Lagrangian Integrated Trajectory - (HYSPLIT) model) has shown that the difference in the isotopic composition of the precipitation is largely associated with the change of the main source regions of atmospheric moisture, namely, the change of the North Atlantic waters (the 2014-2015 winter season) for the inland waters (the 2015-2016 winter season). A comparison of the results of an isotopic analysis has shown good agreement with data of the Global Network of Isotopes in Precipitation (GNIP) interpolated for 1960-2010. Thus, with a proper interpretation the data of the isotopic composition of the winter precipitation in Altai foothills can be used for this territory as an alternative source of the GNIP network data.

  16. Stable isotope characteristics of precipitation of Pamba River basin, Kerala, India

    NASA Astrophysics Data System (ADS)

    Resmi, T. R.; Sudharma, K. V.; Hameed, A. Shahul

    2016-10-01

    Stable isotope composition of precipitation from Pamba River basin, Kerala, India, is evaluated to understand the role of spatial and temporal variations on rainwater isotope characteristics. Physiographically different locations in the basin showed strong spatial and temporal variations. δ 18O varied from -7.63 to -1.75 ‰ in the lowlands; from -9.32 to -1.94 ‰ in the midlands and from -11.6 to -4.00 ‰ in the highlands. Local Meteoric Water Lines (LMWL) for the three regions were determined separately and an overall LMWL for the whole of the basin was found to be δ 2H = 6.6 (±0.4) δ 18 O+10.4 (±2.0). Altitude effect was evident for the basin (0.1 ‰ for δ 18O and 0.8 ‰ for δ 2H per 100 m elevation), while the amount effect was weak. The precipitation formed from the marine moisture supplied at a steady rate, without much isotopic evolution in this period may have masked the possible depletion of heavier isotopes with increasing rainfall. Consistently high d-excess values showed the influence of recycled vapour, despite the prevailing high relative humidity. The oceanic and continental vapour source origins for the south-west and north-east monsoons were clearly noted in the precipitation in the basin. Rayleigh distillation model showed about 30% rainout of the monsoon vapour mass in the basin.

  17. Stable isotope composition of the meteoric precipitation in Croatia.

    PubMed

    Hunjak, Tamara; Lutz, Hans O; Roller-Lutz, Zvjezdana

    2013-01-01

    The precipitation is the input into the water system. Its stable isotope composition has to be known for the proper use and management of water resources. Croatia is not well represented in the Global Network of Isotopes in Precipitation (GNIP) database, and the geomorphology of the country causes specific local conditions. Therefore, at the Stable Isotope Laboratory (SILab), Rijeka, we monitor the stable isotope composition (δ(18)O, δ(2)H) of precipitation. Since δ(18)O and δ(2)H are well correlated, we concentrate the discussion on the δ(18)O distribution. Together with GNIP, our database contains 40 stations in Croatia and in the neighbouring countries. Their different latitudes, longitudes and altitudes give information of great detail, including the influence of the topographic structure on the precipitation in the south-eastern part of Europe, as well as the complex interplay of the different climate conditions in the area. Within a few hundred kilometres, the stable isotope values display a significant change from the maritime character in the south (mean δ(18)O around-6 to-8‰) to the continental behaviour in the north (mean δ(18)O around-8 to-11‰). Depending on the location, the mean δ(18)O values vary with altitude at a rate of approximately-0.2‰/100 m and-0.4‰/100 m, respectively. Also the deuterium excess has been found to depend on location and altitude. The data are being used to construct a δ(18)O map for the entire area.

  18. Modelling the Isotopic Evolution of Precipitation Across Western Canada

    NASA Astrophysics Data System (ADS)

    Sinclair, K.; Marshall, S.; Adams, A.

    2008-12-01

    The variability of synoptic circulation and associated shifts in vapour transport pathways that bring moisture from Pacific Ocean source regions to the Canadian Rocky Mountains govern both the amount and isotopic character of water storage in winter snowpacks. For this reason, it is important to understand the linkages between stable isotopes in precipitation and vapour trajectories in this region. Snowpit isotope data and snow accumulation records were obtained over the 2006-2007 winter season at two alpine field sites in the Canadian Rocky Mountains; the Haig Glacier (Kananaskis Country, AB) and the Opabin Glacier (Yoho National Park, B.C.). Individual accumulation events were identified in snowpit isotope stratigraphies, and additional water isotope samples from each event were collected along a transect in southern British Columbia. Seven secondary schools participated in this project, which allowed the near simultaneous collection of precipitation from each major storm system that crossed this region. Each major storm event over the sampling period was modelled using a coupled orographic-Rayleigh distillation model constrained with water isotope data from Vancouver. The orographic model enables us to explicitly represent the effects of topography on the distribution and intensity of precipitation along each storm trajectory. The output of this model are compared with Rayleigh curves generated using specific humidity data from the University of Wisconsin Nonhydrostatic Modeling System, and with a model that prescribes a linear decrease in temperature and pressure and neglects the effect of topography. The orographic-Rayleigh model is 64% better at predicting δ18O and 10% better at predicting deuterium excess in winter snowpacks in this region than the linear Rayleigh model.

  19. Experimental investigation of Ca isotopic fractionation during abiotic gypsum precipitation

    NASA Astrophysics Data System (ADS)

    Harouaka, Khadouja; Eisenhauer, Anton; Fantle, Matthew S.

    2014-03-01

    Experiments investigating Ca isotopic fractionation during gypsum precipitation were undertaken in order to elucidate the mechanisms and conditions that govern isotopic fractionation during mineral precipitation. Both stirred and unstirred free drift gypsum precipitation experiments were conducted at constant initial ionic strength (0.6 M) and variable initial saturation states (4.8-1.5) and Ca2+:SO42- ratios (3 and 0.33). Experimental durations varied between 0.5 and 190 h, while temperature (25.9-24.0 °C), pH (5.8-5.4) and ionic strength (0.6-0.5) were relatively constant. In all experiments, 20-80% of the initial dissolved Ca reservoir was precipitated. Isotopically light Ca preferentially partitioned into the precipitated gypsum; the effective isotopic fractionation factor (Δ44/40Cas-f = δ44/40Casolid - δ44/40Cafluid) of the experimental gypsum ranged from -2.25‰ to -0.82‰. The log weight-averaged, surface area normalized precipitation rates correlated with saturation state and varied between 4.6 and 2.0 μmol/m2/h. The crystal size and aspect ratios, determined by SEM images, BET surface area, and particle size measurements, co-varied with precipitation rate, such that fast growth produced small (10-20 μm), tabular crystals and slow growth produced larger (>1000 μm), needle shaped crystals. Mass balance derived δ44Cas and Δ44Cas-f, calculated using the initial fluid δ44Ca and the mass fraction of Ca removed during precipitation (fCa) as constraints, suggest that the precipitate was not always sampled homogeneously due to the need to preserve the sample for SEM, surface area, and particle size analyses. The fractionation factor (αs-f), derived from Rayleigh model fits to the fluid and calculated bulk solid, ranged from 0.9985 to 0.9988 in stirred experiments and 0.9987 to 0.9992 in unstirred experiments. The αs-f demonstrated no clear dependence on either precipitation rate or initial saturation state in stirred reactors, but exhibited a positive

  20. Water Isotope Variability Across Individual Precipitation Events in Borneo

    NASA Astrophysics Data System (ADS)

    Bosma, C.; Moerman, J. W.; Cobb, K. M.

    2015-12-01

    The composition of hydrogen and oxygen isotopes in rainwater (measured as δ18O and δD) provides vital information about current hydrological dynamics, and forms the basis for many paleoclimate reconstructions of hydroclimate variability. However, many factors - both local and remote - govern water isotope fractionation, complicating the interpretation of water isotope records. While Raleigh distillation serves as a key first-order driver of the well-noted "amount effect", post-condensation evaporative processes are an important influence on intra-event isotope variations (e.g. Moerman, et al. 2013). To further resolve the processes driving this variability, rainwater isotopes from Gunung Mulu National Park in northern Borneo (4°N, 115 °E) were analyzed at one-minute intervals across nine rain events in 2012. To assess the influence of large-scale, remote fractionation processes versus those that act locally, our intra-event time series was compared to daily-resolved isotope records over the same time interval. We quantify a large range of water isotopic compositions over the sampling period (-13.1‰ to 0.2‰ in δ18O and -88.3‰ to -1.2‰ in δD). There is appreciable evidence for evaporative enrichment at our site, with δ18O vs. δD slopes significantly less than eight - the slope of the Global Meteoric Water Line. Large differences in the shape of the intra-event profile, ranging from monotonically increasing to "V-shaped" (e.g. Celle-Jeanton, et al. 2004) to monotonically decreasing isotopic values indicate that different precipitation regimes have a profound impact on water isotope evolution through a precipitation event. As such, we use a suite of meteorological data including in-situ observations, satellite imagery, model reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF), and NOAA HYSPLIT water vapor back-trajectories to provide an interpretive framework for the observed intra-event isotopic variability. Our study

  1. A synthesis of isotope ratios in precipitation from an assimilation of GNIP observations in a climate model

    NASA Astrophysics Data System (ADS)

    Noone, D.; Horlick, K. A.; Nusbaumer, J. M.; Anderson, D. M.; Emile-Geay, J.; Hakim, G. J.; Perkins, W. A.; Steig, E. J.; Tardif, R.

    2016-12-01

    The vast paucity of information on the hydrogen and oxygen isotope ratios in precipitation continues to hinder progress on using isotopic methods in several related research areas. Despite continuous operation of the Global Network for Isotope Ratios in Precipitation (GNIP) for over half a century, substantial gaps in space and time that restrict hydrological, climatological and ecological research opportunities require more complete datasets. Previous efforts to spatially interpolate existing isotope ratio data has focused on geospatial methods that include some account of pertinent correlative features (including dependence on temperature, altitude and precipitation amount). These approaches have been successful to some degree, however simple interpolation methods (e.g., Kriging) broadly omit account of atmospheric circulation which is known to strongly influence isotope ratios at some locations. Further these mapping methods have focused on generating climatological maps rather than resolving temporal variability. Alternatively, climate models fitted with isotopic tracers produce a map of isotope ratios in precipitation that is consistent with the models' internal dynamics, but at the cost of being a simulation rather than observationally based. Here we use a data assimilation approach that was designed for paleoclimate reconstruction to produce a gridded and temporally complete analysis of the stable isotope ratios in precipitation spanning the 20th Century. The assimilation blends observed meteorology and isotope ratio data with output from the isotopic version of the NCAR Community Atmosphere Model. The success of the method is measured by comparison with existing GNIP station data. We discuss the quantitative advantages of the result in contrast to geospatial methods and the need for resumed and expanded effort in collecting isotope ratio data from precipitation samples to better constrain assimilated datasets.

  2. The Alaska Water Isotope Network (AKWIN): Precipitation, lake, river and stream dynamics

    NASA Astrophysics Data System (ADS)

    Rogers, M.; Welker, J. M.; Toohey, R.

    2011-12-01

    The hydrologic cycle is central to the structure and function of northern landscapes. The movement of water creates interactions between terrestrial, aquatic, marine and atmospheric processes. Understanding the processes and the spatial patterns that govern the isotopic (δ18O & δD) characteristics of the hydrologic cycle is especially important today as: a) modern climate/weather-isotope relations allow for more accurate interpretation of climate proxies and the calibration of atmospheric models, b) water isotopes facilitate understanding the role of storm tracks in regulating precipitation isotopic variability, c) water isotopes allow for estimates of glacial melt water inputs into aquatic systems, d) water isotopes allow for quantification of surface and groundwater interactions, e) water isotopes allow for quantification of permafrost meltwater use by plant communities, f) water isotopes aid in migratory bird forensics, g) water isotopes are critical to estimating field metabolic rates, h) water isotopes allow for crop and diet forensics and i) water isotopes can provide insight into evaporation and transpiration processes. As part of a new NSF MRI project at the Environment and Natural Resources Institute (ENRI) at the University of Alaska Anchorage and as an extension of the US Network for Isotopes in Precipitation (USNIP); we are forming AKWIN. The network will utilize long-term weekly sampling at Denali National Park and Caribou Poker Creek Watershed (USNIP sites-1989 to present), regular sampling across Alaska involving land management agencies (USGS, NPS, USFWS, EPA), educators, volunteers and citizen scientists, UA extended campuses, individual research projects, opportunistic sampling and published data to construct isoscapes and time series databases and information packages. We will be using a suite of spatial and temporal analysis methods to characterize water isotopes across Alaska and will provide web portals for data products. Our network is

  3. Isotopic Fractionation of Mercury in Great Lakes Precipitation

    NASA Astrophysics Data System (ADS)

    Gratz, L. E.; Keeler, G. J.; Blum, J. D.; Sherman, L. S.

    2009-12-01

    Mercury (Hg) is a hazardous bioaccumulative neurotoxin, and atmospheric deposition is a primary way in which mercury enters terrestrial and aquatic ecosystems. However, the chemical processes and transport regimes that mercury undergoes from emission to deposition are not well understood. Thus the use of mercury isotopes to characterize the biogeochemical cycling of mercury is a rapidly growing area of study. Precipitation samples were collected in Chicago, IL, Holland, MI, and Dexter, MI from April 2007 - October 2007 to begin examining the isotopic fractionation of atmospheric mercury in the Great Lakes region. Results show that mass-dependent fractionation relative to NIST-3133 (MDF - δ202Hg) ranged from -0.8‰ to 0.2‰ (±0.2‰) in precipitation samples, while mass-independent fractionation (MIF - Δ199Hg) varied from 0.1‰ to 0.6‰ (±0.1‰). Although clear urban-rural differences were not observed, this may be due to the weekly collection of precipitation samples rather than collection of individual events, making it difficult to truly characterize the meteorology and source influences associated with each sample and suggesting that event-based collection is necessary during future sampling campaigns. Additionally, total vapor phase mercury samples were collected in Dexter, MI in 2009 to examine isotopic fractionation of mercury in ambient air. In ambient samples δ202Hg ranged from 0.3‰ to 0.5‰ (±0.1‰), however Δ199Hg was not significant. Because mercury in precipitation is predominantly Hg2+, while ambient vapor phase mercury is primarily Hg0, these results may suggest the occurrence of MIF during the oxidation of Hg0 to Hg2+ prior to deposition. Furthermore, although it has not been previously reported or predicted, MIF of 200Hg was also detected. Δ200Hg ranged from 0.0‰ to 0.2‰ in precipitation and from -0.1‰ to 0.0‰ in ambient samples. This work resulted in methodological developments in the collection and processing of

  4. Stable isotopes in alpine precipitation as tracers of atmospheric deposition

    NASA Astrophysics Data System (ADS)

    Wasiuta, V. L.; Lafreniere, M. J.; Kyser, T. K.; Norman, A. L.; Mayer, B.; Wieser, M.

    2010-12-01

    Alpine ecosystems, which are generally nutrient poor and exist under extreme climatic conditions, are particularly sensitive to environmental and climatic stressors. Studies in the USA Rocky Mountains and European Alps have shown that alpine terrestrial and aquatic ecosystems are particularly sensitive to enhanced deposition of reactive nitrogen and can show ecologically destructive responses at relatively low levels of nitrogen deposition. However, there is no base line for atmospheric deposition of natural and anthropogenic contaminants in the Canadian alpine. Preliminary results of isotopic and chemical analyses of precipitation from an elevational transect on a glaciated alpine site in the Canadian Rockies are presented. Precipitation accumulating from early autumn through to spring (2008/2009 and 2009/2010) was sampled by means of seasonal snow cover on alpine glaciers. Summer precipitation was sampled through July and August 2010 using bulk collectors installed at the sites of winter sampling. The isotope ratios of dissolved sulphate (δ34S, δ18O), nitrogen (δ15N, δ18O), as well as precipitation (δ2H, δ18O) are utilized in addition to major ion concentrations and trace metal concentrations. Results from 2008/2009 snowpack samples indicate a strong seasonal trend in sulphate (SO42-) and nitrogen (NO3-) deposition which is consistent across the altitudinal transect. Snow horizons representing early autumn and spring precipitation show higher SO42- and NO3- concentrations in contrast to lower concentrations in winter horizons. The aforementioned suite of isotopic and chemical analyses are used to investigate the variability in dominant geographic source regions for atmospheric SO42- and NO3- (local, regional, or long range transported contaminants), as well as to identify contributions from the major biogeochemical source types (e.g. hydrocarbon combustion, lithogenic dust, agricultural emissions).

  5. Entropy analysis of stable isotopes in precipitation: tracing the monsoon systems in China

    PubMed Central

    Wang, Tao; Chen, Jiansheng; Li, Ling

    2016-01-01

    Due to the complexity of monsoon systems and random behaviors of isotope tracers, conventional methods are not adequate for uncovering detailed information about monsoon activities from typically limited precipitation isotope data. We developed a new approach based on the entropy theory to analyze such data with a focus on the monsoon systems in China, dealing with the complexity of these systems and data deficiency. Using precipitation isotope data from 42 selected stations in and around China within the GNIP network, we computed entropies associated with D and 18O. These entropies were found to relate linearly to each other with a proportionality factor close to unity. The spatial variations of the D and 18O entropy in the study area revealed the origins, extents and pathways of the Chinese monsoon systems, as well as their interactions. While further investigation is needed at a greater (global) scale, this study has demonstrated how the entropy theory enables an in-depth analysis of precipitation isotope data to trace the pathway and determine the range of a monsoon system. PMID:27507656

  6. Entropy analysis of stable isotopes in precipitation: tracing the monsoon systems in China.

    PubMed

    Wang, Tao; Chen, Jiansheng; Li, Ling

    2016-08-10

    Due to the complexity of monsoon systems and random behaviors of isotope tracers, conventional methods are not adequate for uncovering detailed information about monsoon activities from typically limited precipitation isotope data. We developed a new approach based on the entropy theory to analyze such data with a focus on the monsoon systems in China, dealing with the complexity of these systems and data deficiency. Using precipitation isotope data from 42 selected stations in and around China within the GNIP network, we computed entropies associated with D and (18)O. These entropies were found to relate linearly to each other with a proportionality factor close to unity. The spatial variations of the D and (18)O entropy in the study area revealed the origins, extents and pathways of the Chinese monsoon systems, as well as their interactions. While further investigation is needed at a greater (global) scale, this study has demonstrated how the entropy theory enables an in-depth analysis of precipitation isotope data to trace the pathway and determine the range of a monsoon system.

  7. Temporal and spatial distributions of δ18O and δ2H in precipitation in Romania

    NASA Astrophysics Data System (ADS)

    Nagavciuc, Viorica; Bădăluță, Carmen-Andreea; Perșoiu, Aurel

    2015-04-01

    Stable isotope ratios of meteoric water have an important role in climatic, paleoclimatic, hydrological and meteorological studies. While such data are available from most of Europe, so far, in Romania (East Central Europe), no systematic study of the stable isotopic composition of precipitation exists. In this context, the aim of this study is to analyze the isotopic composition of rainwater, its temporal and spatial distribution, the identification of the main factors influencing these variations and the creation of the first map of spatial distribution of stable isotopes in precipitation in Romania. Between March 2012 and March 2014 we have collected monthly samples from 22 stations in Romania, which were subsequently analyzed for their δ18O and δ2H at the Stable Isotopes Laboratory, Stefan cel Mare University, Suceava, Romania. Precipitation in W and NW Romania plot along the GMWL, while those in the East are slightly below it, on an evaporative trend. The LMWL for Romania is defined as δ2H=7,27*δ18O + 6,92. The W-E gradient in the distribution of δ18O and δ2H are less marked than the N-S ones, with local influences dominating in areas of strong evaporation (intramountain basins, rain-shadow areas etc). In SW, and especially in autumn and winter, Meditteranean cyclones carry moisture from the Eastern Mediterranean, the δ18O and δ2H values in precipitation in the area plotting between the GMWL and the Eastern Mediterranean Meteoric Water Line. The isotopic composition of rainwater in Romania correlates well with air temperature, and is influenced to a lesser extent by other factors such as the amount of precipitation, topography configuration, the effect of continentalism and season of the year.

  8. Magnesium isotope fractionation in bacterial mediated carbonate precipitation experiments

    NASA Astrophysics Data System (ADS)

    Parkinson, I. J.; Pearce, C. R.; Polacskek, T.; Cockell, C.; Hammond, S. J.

    2012-12-01

    Magnesium is an essential component of life, with pivotal roles in the generation of cellular energy as well as in plant chlorophyll [1]. The bio-geochemical cycling of Mg is associated with mass dependant fractionation (MDF) of the three stable Mg isotopes [1]. The largest MDF of Mg isotopes has been recorded in carbonates, with foraminiferal tests having δ26Mg compositions up to 5 ‰ lighter than modern seawater [2]. Magnesium isotopes may also be fractionated during bacterially mediated carbonate precipitation and such carbonates are known to have formed in both modern and ancient Earth surface environments [3, 4], with cyanobacteria having a dominant role in carbonate formation during the Archean. In this study, we aim to better constrain the extent to which Mg isotope fractionation occurs during cellular processes, and to identify when, and how, this signal is transferred to carbonates. To this end we have undertaken biologically-mediated carbonate precipitation experiments that were performed in artificial seawater, but with the molar Mg/Ca ratio set to 0.6 and with the solution spiked with 0.4% yeast extract. The bacterial strain used was marine isolate Halomonas sp. (gram-negative). Experiments were run in the dark at 21 degree C for two to three months and produced carbonate spheres of various sizes up to 300 μm in diameter, but with the majority have diameters of ~100 μm. Control experiments run in sterile controls (`empty` medium without bacteria) yielded no precipitates, indicating a bacterial control on the precipitation. The carbonate spheres are produced are amenable to SEM, EMP and Mg isotopic analysis by MC-ICP-MS. Our new data will shed light on tracing bacterial signals in carbonates from the geological record. [1] Young & Galy (2004). Rev. Min. Geochem. 55, p197-230. [2] Pogge von Strandmann (2008). Geochem. Geophys. Geosys. 9 DOI:10.1029/2008GC002209. [3] Castanier, et al. (1999). Sed. Geol. 126, 9-23. [4] Cacchio, et al. (2003

  9. Ca Isotope Fractionation During Gypsum Precipitation in a Sulfidic Cave

    NASA Astrophysics Data System (ADS)

    Fantle, M. S.; Macalady, J. L.; Eisenhauer, A.

    2009-12-01

    In sulfidic caves, limestone dissolution above the water table is assocated with sulfuric acid corrosion and attendant precipitation of CaSO4 crusts. Since sulfuric acid is produced by microbially-mediated sulfide oxidation, such systems present unique opportunities to study the effects of microbial processes on Ca isotope systematics. The current study presents preliminary measurements of the Ca isotopic composition of gypsum, calcite, and water samples collected in and around Grotta Bella cave in the Frasassi cave system (central Italy). The environment sampled in this limestone-hosted cave is situated close to flowing sulfidic groundwater (air [H2S]meas ~3 ppm) and is actively forming gypsum in close association with microbial communities ("snottites") dominated by Acidithiobacillus sp [1]. The pH ranges from >2.3 in gypsum crust accumulating on the cave walls to 0-2 at the surface of snottites, while pH in waters sampled outside the cave is between 7 and 8. The current rate of limestone dissolution is ~0.15 mmol CaCO3/cm2/a [2]. This study reports the Ca isotopic composition (δ44Ca, rel. to bulk Earth) of stream and seep water, limestone, and gypsum samples in and around Grotta Bella. Calcium isotopes were measured on a Finnigan Triton TI thermal ionization mass spectrometer at GEOMAR using a 43Ca-48Ca double spike. Field-acidified stream waters and dissolved gypsum were chromatographically purified using MCI Gel (Biorad) while bulk limestone samples were dissolved in nitric acid and loaded onto single Re filaments without additional purification. The δ44Ca values of stream waters and springs are relatively restricted (~0.2‰) and generally the same as bulk limestone. Actively-precipitating CaSO4 minerals, however, show a range of δ44Ca values from limestone-like to values almost 1‰ lighter than corresponding wallrock. Decreasing δ44Ca values in these gypsum minerals correspond to gradients in pH and mineral grain size. The smallest gypsum grains

  10. C isotope fractionation during heterotrophic activity driven carbonate precipitation

    NASA Astrophysics Data System (ADS)

    Balci, Nurgul; Demirel, Cansu

    2016-04-01

    Stable carbon isotopic fractionation during carbonate precipitation induced by environmentally enriched heterotrophic halophilic microorganims was experimentally investigated under various salinity (% 4.5, %8, %15) conditions at 30 °C. Halophilic heterotrophic microorganims were enriched from a hypersaline Lake Acigöl located in SW Turkey (Balci et al.,2015) and later used for the precipitation experiments (solid and liquid medium). The carbonate precipitates had relatively high δ13C values (-4.3 to -16.9 ‰) compared to the δ13C values of the organic compounds that ranged from -27.5 to -25.4 ‰. At salinity of 4.5 % δ13C values of carbonate ranged from -4.9 ‰ to -10.9 ‰ with a 13C-enrichment factor of +20 to +16 ‰ higher than the δ13C values of the associated DOC (-27.5) . At salinity 8 % δ13C values of carbonate ranged from -16.3 ‰ to -11.7 ‰ with a 13C-enrichment factor of+11.3 to+15.9 ‰ higher than the δ13C values of the associated DOC. The respected values for 15 % salinity ranged from -12.3 ‰ to -9.7 ‰ with a 13C-enrichment factor of +15.2 to+16.8 ‰ higher than the δ13C values of the associated DOC. The carbonate precipitates produced in the solid medium are more enriched in 13C relative to liquid culture experiments. These results suggest that the carbon in the solid was derived from both the bacterial oxidation of organic compounds in the medium and from the atmospheric CO2. A solid medium used in the experiments may have suppressed convective and advective mass transport favouring diffusion-controlled system. This determination suggests that the rate and equilibration of CO2 exchange with the atmosphere is the major control on C isotope composition of carbonate minerals precipitated in the experiments. Key words: Lake Acıgöl, halophilic bacteria, carbonate biomineralization, C isotopes References Nurgul Balci, Meryem Menekşe, Nevin Gül Karagüler, M. Şeref Sönmez,Patrick Meister 2015.Reproducing authigenic carbonate

  11. The effect of small scale variablity in isotopic composition of precipitation on hydrograph separation results

    NASA Astrophysics Data System (ADS)

    Fischer, Benjamin; van Meerveld, Ilja; Seibert, Jan

    2016-04-01

    Understanding runoff processes is important for predictions of streamflow quantity and quality. The two-component isotope hydrograph separation (IHS) method is a valuable tool to study how catchments transform rainfall into runoff. IHS allows the stormflow hydrograph to be separated into rainfall (event water) and water that was stored in the catchment before the event (pre-event water). To be able to perform an IHS, water samples of baseflow (pre-event water) and stormflow are collected at the stream outlet. Rainfall is usually collected at one location by hand as an event total or sampled sequentially during the event. It is usually assumed that the spatial variability in rainfall and the isotopic composition of rainfall are negligible for small (<10km2) catchments. However, different studies have shown that precipitation can vary within short distances. Subsequently it remains unclear how the spatio-temproal variability of rainfall and the stable isotope composition of rainfall affect the results of an IHS. In this study, we investigated the effects of the spatio-temporal variability in the isotopic composition of rainfall across a small headwater catchment in Switzerland. Rainfall was measured at eight locations and three streams (catchment area of 0.15, 0.23, and 0.7 km2). The isotopic composition of rainfall and streamflow were sampled for 10 different rain events (P: 5 mm intervals, Q: 12 to 51 samples per events). This dataset was used to perform a two-component isotope hydrograph separation. The results show that for some events the spatial variability in total rainfall, mean and maximum rainfall intensity and stable isotope composition of rainfall was high. There was no relation between the stable isotope composition of rainfall and the rainfall sum, rainfall intensity or altitude. The spatial variability of the isotopic composition of rainfall was for 4 out of the 10 events as large as the temporal variability in the isotopic composition. Different

  12. Climate Phase and Long-Term Site Specific Patterns of Isotopes (d18O) in Precipitation across the U. S.

    NASA Astrophysics Data System (ADS)

    Welker, J. M.; White, J. W.; Vachon, R.; Zauscher, M.; Castro, C.; Pielke, R.

    2003-12-01

    Our understanding of the spatial and temporal patterns of the isotopic characteristics of precipitation across the U. S. has been limited because no systematic analysis have been conducted across the U. S. during divergent climate phases or over extended recent time periods. Using weekly precipitation samples from a spatially complete set of sampling stations across the U. S. we have evaluate the following questions: a) what are the seasonal patterns of the isotopic (d18O) patterns across the U. S. during Neutral and El Nino phases, b) to what degree do differences in temperature, precipitation and climatology explain El Nino affects on the seasonal patterns of isotopes in precipitation and c) what are the long-term patterns and magnitudes of d18O-values in precipitation over a recent 10-year period for sites in the western, central and eastern U. S.? We have found that depleted precipitation dominates the Northern Rocky Mountain region, while relatively enriched precipitation occurs in the western U. S. and in the southern Great Lakes region, however, these patterns are season specific, being magnified in spring and fall. These seasonal differences appear to reflect climatological changes with intensification of the sub-tropical flow and a delay in the monsoon formation during El Nino phases. Time-series data for sites in the western U. S. exhibit the strongest annual and monthly temperature correlations with slopes ranging between 0.3 to 0.6oC per mil of d18O.

  13. Quantifying the climatic and topographic controls of precipitation isotopes in continental interiors: applications to unraveling isotopic records of climate in Cenozoic Central Asia

    NASA Astrophysics Data System (ADS)

    Winnick, M. J.; Chamberlain, C. P.; Caves, J. K.; Welker, J. M.

    2014-12-01

    Since the establishment of the IAEA-WMO precipitation-monitoring network in 1961, it has been observed that isotope ratios in precipitation (δ2H and δ18O) generally decrease from coastal to inland locations, an observation described as the continental effect. While discussed frequently in the literature, there have been few attempts to quantify the variables controlling this effect despite the fact that isotopic gradients over continents vary by orders of magnitude. In a number of studies, traditional Rayleigh fractionation has proven inadequate in describing the global variability of isotopic gradients due to its simplified treatment of moisture transport and its lack of moisture recycling through evapotranspiration (ET). We use a one-dimensional idealized model of water vapor transport along a storm track to investigate the dominant variables controlling isotopic gradients in precipitation across terrestrial environments. We find that the sensitivity of these gradients to progressive rainout is controlled primarily by ET with secondary controls exerted by eddy transport. A comparison of modern isotopic gradients within high elevation continental interior regions shows that the effects of seasonal changes in ET are of the same order of magnitude as the effects of rainout due to orographic precipitation. This implies that changing climate and associated changes in ET rates may amplify or completely negate isotopic signals of uplift. We further apply the model to a spatial compilation of Cenozoic isotopic records throughout Central Asia. Over the past 50 Ma, extensive recycling of water via ET has likely masked isotopic signals of the uplift of the northern Tibetan Plateau, Tian Shan, Altai, and Hangay ranges as revealed by complimentary methods of measuring uplift timing and rates. Our results highlight the importance of the coupling between topography, atmospheric circulation, and biological processes in controlling isotopic records of past climate.

  14. Hydrochemical and isotopic investigation of atmospheric precipitation in Beijing, China.

    PubMed

    Zhai, Yuanzheng; Wang, Jinsheng; Zhang, Yang; Teng, Yanguo; Zuo, Rui; Huan, Huan

    2013-07-01

    Precipitation water samples were collected at an urban site in Beijing in a hydrological cycle (July 2008-July 2009), and analyzed for TDS, total alkalinity, total hardness, free CO₂, soluble SiO₂, bromide, sulfide, phosphate, major ions (K(+), Na(+), Ca(2+), Mg(2+), NH₄(+), HCO₃(-), Cl(-), SO₄(2-), NO₃(-)), trace elements (CO₃(2-), Mn, Sr(2+), Fe(2+), Fe(3+), Al, F(-), NO₂(-)), stable isotopes ((2)H and (18)O), and radioactive isotope ((3)H). In addition, available published hydrochemical and isotopic data of precipitation of Beijing in the past were also collected and conjointly analyzed. Most of the parameters of samples tested varied considerably in the hydrological cycle. In general, HCO₃(-) and SO₄(2-), and Ca(2+) and NH₄(+) are the dominant anions and cations, respectively. Using Na(+) as an indicator of marine origin, and Al for the terrestrial inputs, the proportions of major elements from sea salt and terrestrial sources were estimated by using the combination of statistical analysis methods and analogy method. More than 70.1% of Cl(-), 98.1% of Ca(2+), and 93.6% of K(+) were non-sea-salt origin, while more than 98.4% of Na(+) was from marine sources. The LMWL (Local Meteoric Water Line) was obtained with an equation of δ(2)H=7.0181δ(18)O+3.5231 (‰, R(2)=0.86, n=36), which was similar to GMWL (Global Meteoric Water Line). δ(2)H, δ(18)O and Δ-excess changed radically with month and season, but had no apparent seasonal effect, precipitation amount effect, and temperature effect. The annual mean values of Δ-excess for 1979 (16.5‰) and 1980 (16.3‰) were much bigger than that for 2007 (7.2‰), 2008 (2.1‰) and 2009 (4.5‰). The composition of (2)H and (18)O was probably intrinsically determined by the sources of water vapor and the physical and chemical processes occurred along the migration paths of water vapor from sources to the aimed precipitation area. Temporal change of (3)H was only influenced by the nuclear testing

  15. Modern Freshwater Microbialites, Cuatro Ciénegas, Mexico. II. Detailed Spatial Analysis of Geochemical Signals Linked to Microbial Activity and Carbonate Precipitation/

    NASA Astrophysics Data System (ADS)

    Hollander, D.; Breitbart, M.; Nitti, A.; van Mooy, B.; Seifert, J.; Souza, V.

    2010-04-01

    This study applies a highly resolved spatial approach using genomic, stable isotopic, and molecular organic geochemical analyses to determine the microorganisms and chemical processes for carbonate precipitation in the freshwater microbialites in Cuatro Ciénegas, MX.

  16. Influence of vegetation canopies on precipitation partitioning and isotope fractionation in northern upland catchments

    NASA Astrophysics Data System (ADS)

    Braun, Hannah; Tetzlaff, Doerthe; Soulsby, Chris; Weiler, Markus

    2016-04-01

    Climate change is predicted to have far reaching implications for northern high latitude regions including changing precipitation regimes and increasing temperatures in the coming decades. In many areas this will promote increased forest cover as a result of vegetation succession or mitigation measures. For example, in the Scottish Highlands, forest cover is increasing as a result of adaptive management and increased biofuel production. In the wet, windy Scottish hydroclimate this has the potential to significantly increase interception losses, reduce net precipitation and affect the spatial and temporal distribution of soil moisture. Recent studies have also shown that such processes may also change the isotopic signature of net rainfall in throughfall and stemflow with implications for using isotopes as hydrological tracers. Such effects may be exacerbated by projected higher temperatures and reduced summer precipitation. The main focus of this study was to quantify the effects of forest and non-forest vegetation canopies on the spatio-temporal variability of throughfall and stemflow in the Bruntland Burn, a 3.2 km2 montane experimental catchment in the Scottish Highlands. We investigated differences in both the quantity and isotopic composition of throughfall and stemflow under Scots Pine (Pinus sylvestris) forest and heather (Calluna vulgaris) moorland growing on podzolic soils. Altogether, 75 throughfall and 10 stemflow collectors were placed in four plots with different topographic positions and vegetation characteristics (two different aged Scots pine plantations and two heather sites) and canopy coverage was determined using digital photography. Over a 5 month sampling period, weekly throughfall samples were taken. We also analysed more than 1100 samples for stable isotopes δ18O and δD. Interception losses were 38% under moorland and up to 47% for the plantation sides. Both throughfall and stemflow amounts were found to be highly variable and were mostly

  17. Chemical and sulfur isotopic composition of precipitation in Beijing, China.

    PubMed

    Zhu, Guangxu; Guo, Qingjun; Chen, Tongbin; Lang, Yunchao; Peters, Marc; Tian, Liyan; Zhang, Hanzhi; Wang, Chunyu

    2016-03-01

    China is experiencing serious acid rain contamination, with Beijing among the worst-hit areas. To understand the chemical feature and the origin of inorganic ions in precipitation of Beijing, 128 precipitation samples were collected and analyzed for major water-soluble ions and δ(34)S. The pH values ranged from 3.68 to 7.81 and showed a volume weighted average value (VWA) of 5.02, with a frequency of acid rain of 26.8 %. The VWA value of electrical conductivity (EC) was 68.6 μS/cm, which was nearly 4 times higher than the background value of northern China. Ca(2+) represented the main cation; SO4 (2-) and NO3 (-) were the dominant anion in precipitation. Our study showed that SO4 (2-) and NO3 (-) originated from coal and fossil fuel combustion; Ca(2+), Mg(2+), and K(+) were from the continental sources. The δ(34)S value of SO4 (2-) in precipitation ranged from +2.1 to +12.8‰ with an average value of +4.7‰. The δ(34)S value showed a winter maximum and a summer minimum tendency, which was mainly associated with temperature-dependent isotope equilibrium fractionation as well as combustion of coal with relatively positive δ(34)S values in winter. Moreover, the δ(34)S values revealed that atmospheric sulfur in Beijing are mainly correlated to coal burning and traffic emission; coal combustion constituted a significant fraction of the SO4 (2-) in winter precipitation.

  18. Spatial downscaling of precipitation using adaptable random forests

    NASA Astrophysics Data System (ADS)

    He, Xiaogang; Chaney, Nathaniel W.; Schleiss, Marc; Sheffield, Justin

    2016-10-01

    This paper introduces Prec-DWARF (Precipitation Downscaling With Adaptable Random Forests), a novel machine-learning based method for statistical downscaling of precipitation. Prec-DWARF sets up a nonlinear relationship between precipitation at fine resolution and covariates at coarse/fine resolution, based on the advanced binary tree method known as Random Forests (RF). In addition to a single RF, we also consider a more advanced implementation based on two independent RFs which yield better results for extreme precipitation. Hourly gauge-radar precipitation data at 0.125° from NLDAS-2 are used to conduct synthetic experiments with different spatial resolutions (0.25°, 0.5°, and 1°). Quantitative evaluation of these experiments demonstrates that Prec-DWARF consistently outperforms the baseline (i.e., bilinear interpolation in this case) and can reasonably reproduce the spatial and temporal patterns, occurrence and distribution of observed precipitation fields. However, Prec-DWARF with a single RF significantly underestimates precipitation extremes and often cannot correctly recover the fine-scale spatial structure, especially for the 1° experiments. Prec-DWARF with a double RF exhibits improvement in the simulation of extreme precipitation as well as its spatial and temporal structures, but variogram analyses show that the spatial and temporal variability of the downscaled fields are still strongly underestimated. Covariate importance analysis shows that the most important predictors for the downscaling are the coarse-scale precipitation values over adjacent grid cells as well as the distance to the closest dry grid cell (i.e., the dry drift). The encouraging results demonstrate the potential of Prec-DWARF and machine-learning based techniques in general for the statistical downscaling of precipitation.

  19. Do oxygen stable isotopes track precipitation moisture source in vascular plant dominated peatlands?

    NASA Astrophysics Data System (ADS)

    Charman, D.; Amesbury, M. J.; Newnham, R.; Loader, N.; Goodrich, J. P.; Gallego-Sala, A. V.; Royles, J.; Keller, E. D.; Baisden, W. T.

    2014-12-01

    Variations in the isotopic composition of precipitation are determined by fractionation processes which occur during temperature and humidity dependent phase changes associated with evaporation and condensation. Oxygen stable isotope ratios have therefore been frequently used as a source of palaeoclimate data from a variety of proxy archives. Exploitation of this record from ombrotrophic peatlands, where the source water used in cellulose synthesis is derived solely from precipitation, has been mostly limited to Northern Hemisphere Sphagnum-dominated bogs, with limited application in the Southern Hemisphere (SH) or in peatlands dominated by vascular plants. Throughout New Zealand (NZ), the preserved root matrix of the restionaceous wire rush (Empodisma spp.) forms deep peat deposits. NZ provides an ideal location to undertake empirical research into oxygen isotope fractionation in vascular peatlands because sites are ideally suited to single taxon analysis, preserve potentially high resolution full Holocene palaeoclimate records and are situated in the climatically sensitive SH mid-latitudes. Crucially, large gradients exist in the mean isotopic composition of precipitation across NZ, caused primarily by the relative influence of different climate modes. We test the capacity for δ18O analysis of Empodisma alpha cellulose from ombrotrophic restiad peatlands in NZ to provide a methodology for developing palaeoclimate records. We took surface plant, water and precipitation samples over spatial (six sites spanning >10° latitude) and temporal (monthly measurements over one year) gradients. We found a strong link between the isotopic compositions of surface root water, the most likely source water for plant growth, and precipitation in both datasets. Back-trajectory modelling of precipitation moisture source for rain days prior to sampling showed clear seasonality in the temporal data that was reflected in surface root water. The link between source water and plant

  20. The isotopic composition of precipitation from a winter storm - a case study with the limited-area model COSMOiso

    NASA Astrophysics Data System (ADS)

    Pfahl, S.; Wernli, H.; Yoshimura, K.

    2012-04-01

    Stable water isotopes are valuable tracers of the atmospheric water cycle, and potentially provide useful information also on weather-related processes. In order to further explore this potential, the water isotopes H218O and HDO are incorporated into the limited-area weather forecast and climate model COSMO. The new COSMOiso model includes an advanced microphysical scheme, a convection parameterisation and non-hydrostatic dynamics that facilitate simulations from sub-kilometre to synoptic spatial scales. In a first case study, the model is applied for simulating a winter storm event in January 1986 over the eastern United States associated with intense frontal precipitation. The modelled isotope ratios in precipitation and water vapour are compared to spatially distributed δ18O observations from a study by Gedzelman and Lawrence (1990). COSMOiso very accurately reproduces the statistical distribution of δ18O in precipitation, and also the synoptic-scale spatial pattern and temporal evolution agree well with the measurements. Deviations at single stations can partly be attributed to errors in the representation of mesoscale atmospheric structures in the model. Grounded on this overall meteorological evaluation, the model is then used for investigating the physical processes causing the synoptic-scale variability of δ18O during the selected event. Perpendicular to the front that triggers most of the rainfall, COSMOiso simulates a gradient in the isotopic composition of the precipitation, with high δ18O values in the warm air to the east and lower values in the cold sector behind the front. This spatial gradient is connected to a temporal evolution with high δ18O values in the beginning and a decrease later on at locations where the front passes by. Two major processes are identified that contribute to creating the spatial pattern. First, the advection of cold, depleted water vapour to the west of the front and warm, more enriched vapour further to the east, in

  1. Coupling Meteorology, Metal Concentrations, and Pb Isotopes for Source Attribution in Archived Precipitation Samples

    EPA Science Inventory

    A technique that couples lead (Pb) isotopes and multi-element concentrations with meteorological analysis was used to assess source contributions to precipitation samples at the Bondville, Illinois USA National Trends Network (NTN) site. Precipitation samples collected over a 16 ...

  2. Coupling Meteorology, Metal Concentrations, and Pb Isotopes for Source Attribution in Archived Precipitation Samples

    EPA Science Inventory

    A technique that couples lead (Pb) isotopes and multi-element concentrations with meteorological analysis was used to assess source contributions to precipitation samples at the Bondville, Illinois USA National Trends Network (NTN) site. Precipitation samples collected over a 16 ...

  3. Significance of the air moisture source on the stable isotope composition of the precipitation in Hungary

    NASA Astrophysics Data System (ADS)

    Czuppon, György; Bottyán, Emese; Krisztina, Krisztina; Weidinger, Tamás; Haszpra, László

    2017-04-01

    In the last few years, the analysis of backward trajectories has become a common use for identifying moisture uptake regions for the precipitation of various regions. Hungary is influenced by meteorological (climatological) conditions of Atlantic, Mediterranean and North/East regions therefore this area is sensitive to detect changes in the atmospheric circulation. In this study we present the result of the investigation about the determination of air moisture source regions for six localities in Hungary for more than four years. To reconstruct the path of the air moisture from the source region, we ran the NOAA HYSPLIT trajectory model using the GDAS database with 1° spatial and 6 hours temporal resolution for every precipitation event, for heights of 500, 1500 and 3000 m. We determined the location where water vapour entered into the atmosphere by calculating specific humidity along the trajectories. Five possible moisture source regions for precipitation were defined: Atlantic, North European, East European, Mediterranean and continental (local/convective). Additionally, this study evaluates the regional differences in stable isotope compositions of precipitation based on hydrogen and oxygen isotope analyses of daily rainwater samples. Stable isotope variations show systematic and significant differences between the regions. The variability of moisture source shows also systematic seasonal and spatial distribution. Interestingly, the most dominant among the identified source regions in all stations is the Mediterranean area; while the second is the Atlantic region. The ratio of the precipitations originated in Eastern and Northern Europe seem to correlate with the geographic position of the meteorological station. Furthermore, the ratios of the different moisture sources show intra annual variability. In each location, the amount weighted d-excess values were calculated for the identified moisture sources. The precipitation originated in the Mediterranean

  4. Three-year monitoring of stable isotopes of precipitation at Concordia Station, East Antarctica

    NASA Astrophysics Data System (ADS)

    Stenni, Barbara; Scarchilli, Claudio; Masson-Delmotte, Valerie; Schlosser, Elisabeth; Ciardini, Virginia; Dreossi, Giuliano; Grigioni, Paolo; Bonazza, Mattia; Cagnati, Anselmo; Karlicek, Daniele; Risi, Camille; Udisti, Roberto; Valt, Mauro

    2016-10-01

    Past temperature reconstructions from Antarctic ice cores require a good quantification and understanding of the relationship between snow isotopic composition and 2 m air or inversion (condensation) temperature. Here, we focus on the French-Italian Concordia Station, central East Antarctic plateau, where the European Project for Ice Coring in Antarctica (EPICA) Dome C ice cores were drilled. We provide a multi-year record of daily precipitation types identified from crystal morphologies, daily precipitation amounts and isotopic composition. Our sampling period (2008-2010) encompasses a warmer year (2009, +1.2 °C with respect to 2 m air temperature long-term average 1996-2010), with larger total precipitation and snowfall amounts (14 and 76 % above sampling period average, respectively), and a colder and drier year (2010, -1.8 °C, 4 % below long-term and sampling period averages, respectively) with larger diamond dust amounts (49 % above sampling period average). Relationships between local meteorological data and precipitation isotopic composition are investigated at daily, monthly and inter-annual scale, and for the different types of precipitation. Water stable isotopes are more closely related to 2 m air temperature than to inversion temperature at all timescales (e.g. R2 = 0.63 and 0.44, respectively for daily values). The slope of the temporal relationship between daily δ18O and 2 m air temperature is approximately 2 times smaller (0.49 ‰ °C-1) than the average Antarctic spatial (0.8 ‰ °C-1) relationship initially used for the interpretation of EPICA Dome C records. In accordance with results from precipitation monitoring at Vostok and Dome F, deuterium excess is anti-correlated with δ18O at daily and monthly scales, reaching maximum values in winter. Hoar frost precipitation samples have a specific fingerprint with more depleted δ18O (about 5 ‰ below average) and higher deuterium excess (about 8 ‰ above average) values than other precipitation

  5. A New Look at the Global Distribution of Isotopes in Precipitation

    NASA Astrophysics Data System (ADS)

    Posmentier, E. S.; Faiia, A. M.; Feng, X.

    2005-05-01

    The hydrogen and oxygen isotopic ratios of meteoric water, as preserved in geologic materials, are widely used to reconstruct past climatic conditions. Correlation between temperature and isotopic composition of precipitation for temperate regions has been well documented, and modern day correlations are used in interpreting paleo-isotopic records, although temperature is not the direct causative factor in isotopic distribution. Semi-tropical and tropical locations demonstrate correlation between amount of precipitation and isotopic value. In this report, we propose that the parameter (E-P)/P, where E is evaporation and P is precipitation, explains the annual mean isotopic distribution in both temperate and tropical environments. This parameter is also shown to correlate with the seasonal distribution of isotopic ratios in precipitation globally. Global data was downloaded from the GNIP (Global Network for Isotopes in Precipitation) database (http://isohis.iaea.org). This set is comprised of monthly hydrogen and oxygen isotopic compositions, amount of precipitation, and temperature for over 500 stations throughout the world. The monthly oxygen isotopic data were plotted against station latitude and a spline function fitted for each month. The resulting distributions show a local minimum in isotopic values in the tropics, which migrates seasonally following the ITCZ. On either side of the minimum, two asymmetric maxima occur which change in position and amplitude throughout the year. We use a simple one-dimensional model to predict the seasonal isotopic distribution. The model divides the world into 5-degree latitudinal zones. Seasonally varying evaporation and precipitation are specified for each zone from marine climatologic records, and the model uses the mass balance equations to calculate the import or export of water vapor and the isotopic value of precipitation falling in each zone. The results show that the major variations in isotopic value of precipitation

  6. Stable isotope composition of precipitation in the south and north slopes of Wushaoling Mountain, northwestern China

    NASA Astrophysics Data System (ADS)

    Zongxing, Li; Qi, Feng; Song, Yong; Wang, Q. J.; Yang, Jiao; Yongge, Li; Jianguo, Li; Xiaoyan, Guo

    2016-12-01

    A study of spatial and temporal variability of precipitation isotope composition on the southern and north slopes of Wushaoling Mountain was conducted in order to explore the processes influencing its evolution. The analysis indicated that the isotopic composition, the slopes and intercepts of Local Meteroic Water Lines, altitude gradients and temperature effect are higher on the north slope than those on the south slope. The d-excess showed an increase from lower to higher altitudes, and the altitude gradients changed with season. The correlation coefficients between δ18O and d-excess decreased with increasing altitude due to weakening sub-cloud evaporation. Westerly wind principally dominates Wushaoling Mountain, so the relatively negative stable isotope values observed are related to the long distance transportation of water vapor in spring and winter. In summer and autumn, the locally strong sub-cloud evaporation cause relatively higher δ18O and lower d-excess. The results suggested that the sub-cloud evaporation has enriched the δ18O composition by 23%, 23%, 32%, 42% and 29% in May, June, July, August and September, respectively. In some circumstances, δ18O and δD were depleted at the end of multi-days rainfall events due to the rainout process. In addition, monsoonal moisture caused some negative δ18O in summer when an enhanced cyclonic circulation had developed on Tibetan Plateau. The study enhances the knowledge of isotopic evolution of precipitation and provides a basis for further study of isotopic hydrology in arid regions.

  7. Spatial patterns of global precipitation in the frequency domain

    NASA Astrophysics Data System (ADS)

    Denaxa, Demetra; Markonis, Yannis

    2016-04-01

    This study examines global precipitation patterns during 1901-2014 by using the monthly CRU TS3.23 land precipitation gridded dataset, the European historical reconstruction (1500-2000 AD) of Pauling et al. (2006), and the CMIP5 model outputs. In particular, spatial features of long-term precipitation are explored for each continent, using a novel peak-detection methodology of spectral analysis. This approach estimates the statistical significance of the spectral peaks based on the structure of the spectral continuum, as determined by the autocorrelation structure. To this end, the spatial variability of the lag-one autocorrelation coefficient for the annual time scale, as well as the Hurst coefficient, have been also estimated and a global overview of them is presented. Pauling, Andreas, et al. "Five hundred years of gridded high-resolution precipitation reconstructions over Europe and the connection to large-scale circulation." Climate Dynamics 26.4 (2006): 387-405.

  8. Spatial patterns of throughfall isotopic composition at the event and seasonal timescales

    NASA Astrophysics Data System (ADS)

    Allen, Scott T.; Keim, Richard F.; McDonnell, Jeffrey J.

    2015-03-01

    Spatial variability of throughfall isotopic composition in forests is indicative of complex processes occurring in the canopy and remains insufficiently understood to properly characterize precipitation inputs to the catchment water balance. Here we investigate variability of throughfall isotopic composition with the objectives: (1) to quantify the spatial variability in event-scale samples, (2) to determine if there are persistent controls over the variability and how these affect variability of seasonally accumulated throughfall, and (3) to analyze the distribution of measured throughfall isotopic composition associated with varying sampling regimes. We measured throughfall over two, three-month periods in western Oregon, USA under a Douglas-fir canopy. The mean spatial range of δ18O for each event was 1.6‰ and 1.2‰ through Fall 2009 (11 events) and Spring 2010 (7 events), respectively. However, the spatial pattern of isotopic composition was not temporally stable causing season-total throughfall to be less variable than event throughfall (1.0‰; range of cumulative δ18O for Fall 2009). Isotopic composition was not spatially autocorrelated and not explained by location relative to tree stems. Sampling error analysis for both field measurements and Monte-Carlo simulated datasets representing different sampling schemes revealed the standard deviation of differences from the true mean as high as 0.45‰ (δ18O) and 1.29‰ (d-excess). The magnitude of this isotopic variation suggests that small sample sizes are a source of substantial experimental error.

  9. Spatial and temporal variability of precipitation and drought in Portugal

    NASA Astrophysics Data System (ADS)

    Martins, D. S.; Raziei, T.; Paulo, A. A.; Pereira, L. S.

    2012-05-01

    The spatial variability of precipitation and drought are investigated for Portugal using monthly precipitation from 74 stations and minimum and maximum temperature from 27 stations, covering the common period of 1941-2006. Seasonal precipitation and the corresponding percentages in the year, as well as the precipitation concentration index (PCI), was computed for all 74 stations and then used as an input matrix for an R-mode principal component analysis to identify the precipitation patterns. The standardized precipitation index at 3 and 12 month time scales were computed for all stations, whereas the Palmer Drought Severity Index (PDSI) and the modified PDSI for Mediterranean conditions (MedPDSI) were computed for the stations with temperature data. The spatial patterns of drought over Portugal were identified by applying the S-mode principal component analysis coupled with varimax rotation to the drought indices matrices. The result revealed two distinct sub-regions in the country relative to both precipitation regimes and drought variability. The analysis of time variability of the PC scores of all drought indices allowed verifying that there is no linear trend indicating drought aggravation or decrease. In addition, the analysis shows that results for SPI-3, SPI-12, PDSI and MedPDSI are coherent among them.

  10. Holocene precipitation seasonality captured by a dual hydrogen and oxygen isotope approach at Steel Lake, Minnesota

    NASA Astrophysics Data System (ADS)

    Henderson, Anna K.; Nelson, David M.; Hu, Feng Sheng; Huang, Yongsong; Shuman, Bryan N.; Williams, John W.

    2010-12-01

    Middle-Holocene (8 to 4 ka BP) warmth and aridity are well recorded in sediment archives from midcontinental North America. However, neither the climatic driver nor the seasonal character of precipitation during this period is well understood because of the limitations of available proxy indicators. For example, an important challenge is to distinguish among the interacting effects of evaporation, temperature, or precipitation seasonality in existing δ 18O records from the region. Here we combine hydrogen isotopes of palmitic acid and oxygen isotopes of carbonate to derive lake-water isotopic values during the Holocene at Steel Lake in north-central Minnesota. In combination, these data enable us to separate variations in evaporation from variations in the isotopic composition of input-waters to lake. Variations in evaporation are used as a proxy for aridity and lake-water input isotopic values are used as a proxy for the isotopic values of meteoric precipitation. Our results suggest that lake-water input isotopic values were more negative during the middle Holocene than at present. To test whether these more negative values are related to temperature or precipitation seasonality, we compare pollen-inferred temperatures and the expected isotopic value of precipitation resulting from these temperatures to the reconstructed precipitation isotopic values. Results suggest that middle Holocene warmth and aridity were associated with increased evaporation rates and decreased summer precipitation. These inferences are consistent with climate simulations that highlight the role of seasonal insolation and sea surface temperatures in driving variations in precipitation seasonality during the Holocene. Results also suggest that changes in Holocene precipitation seasonality may have influenced the expansion of the prairie-forest border in Minnesota as well as regional variations in grassland community composition. This study demonstrates the efficacy of the dual hydrogen and

  11. Climatic Signals in the Stable Isotope Composition of Precipitation in Northeast Asia

    NASA Astrophysics Data System (ADS)

    Lee, K.; Grundstein, A. J.; Lee, D.

    2002-12-01

    The IAEA/WHO stable isotopic data from various locations in Northeast Asia were evaluated to examine the climatic factors controlling the temporal and spatial variations in stable isotopic compositions of precipitation. To further understand these factors, stable isotopic data were obtained for individual rainfall events over a two-year period at Jeju Island, Korea. The temperature appears to be the main factor controlling the stable isotope composition of precipitation in the northwestern (inner continental) region of the study area, whereas the amount effect for summer rains is overshadowing the temperature effect in the southeastern (coastal) region. The deuterium excess values, which range from 3.0 to 40.6 per mil at Jeju Island, show a distinct seasonal variation with higher d-values in winter (>~15 per mil) and lower values in summer (~10 per mil). Such a seasonal variation appears to be closely related to two air masses with different moistures affecting the Jeju Island during different seasons. To assess the physical mechanism for this, air parcel trajectories were back calculated for precipitation events with the highest five d-values. In all five cases, the modeled trajectories show that air masses originate over northeast Asia and pass over the Yellow Sea before reaching Jeju Island. As the dry air passes over the relatively warmer water, large amounts of net evaporation occur from the sea-surface to the atmosphere that serves to increase the moisture content of the air mass. Thus, the isotopically enriched winter precipitation is a function of oceanic moisture close to Korea and Japan. In summer, the lower deuterium excess values reflect a very different climatic regime in which the air mass reflects the hot and humid characteristics of North Pacific. The trajectories of rainfall events with the lowest five d-values illustrate that the source regions for these air masses occur in the South China Sea or the tropical North Pacific Ocean. The trajectory

  12. Hierarchical Spatial Analysis of Extreme Precipitation in Urban Areas

    NASA Astrophysics Data System (ADS)

    Rajulapati, C. R.; Mujumdar, P.

    2015-12-01

    Quantification of extreme precipitation is important for hydrologic designs. Due to lack of availability of extreme precipitation data for sufficiently large number of years, estimating the probability of extreme events is difficult and extrapolating the distributions to locations where observations are not available is challenging. In an urban setting, the spatial variation of precipitation can be high; the precipitation amounts and patterns often vary within short distances of less than 10 km. Therefore it is crucial to study the uncertainties in the spatial variation of precipitation in urban areas. In this work, the extreme precipitation is modeled spatially using the Bayesian hierarchical spatial analysis and the spatial variation of return levels is studied. The analysis is carried out with both the Peak over Threshold (PoT) and the Block Maxima approaches for defining the extreme precipitation. The study area is Bangalore city, India. Daily data for seventeen stations in and around Bangalore city are considered in the study. The threshold exceedences are modeled using a Generalized Pareto (GP) distribution and the block maxima are modeled using Generalized Extreme Value (GEV) distribution. In the hierarchical analysis, the statistical model is specified in three layers. The data layer models the data (either block maxima or the threshold exceedences) at each station. In the process layer, the latent spatial process characterized by geographical and climatological covariates (lat-lon, elevation, mean temperature etc.) which drives the extreme precipitation is modeled and in the prior level, the prior distributions that govern the latent process are modeled. Markov Chain Monte Carlo (MCMC) algorithm is used to obtain the samples of parameters from the posterior distribution of parameters. The spatial maps of return levels for specified return periods, along with the associated uncertainties, are obtained. The results show that there is significant variation in

  13. Spatial interpolation schemes of daily precipitation for hydrologic modeling

    USGS Publications Warehouse

    Hwang, Y.; Clark, M.; Rajagopalan, B.; Leavesley, G.

    2012-01-01

    Distributed hydrologic models typically require spatial estimates of precipitation interpolated from sparsely located observational points to the specific grid points. We compare and contrast the performance of regression-based statistical methods for the spatial estimation of precipitation in two hydrologically different basins and confirmed that widely used regression-based estimation schemes fail to describe the realistic spatial variability of daily precipitation field. The methods assessed are: (1) inverse distance weighted average; (2) multiple linear regression (MLR); (3) climatological MLR; and (4) locally weighted polynomial regression (LWP). In order to improve the performance of the interpolations, the authors propose a two-step regression technique for effective daily precipitation estimation. In this simple two-step estimation process, precipitation occurrence is first generated via a logistic regression model before estimate the amount of precipitation separately on wet days. This process generated the precipitation occurrence, amount, and spatial correlation effectively. A distributed hydrologic model (PRMS) was used for the impact analysis in daily time step simulation. Multiple simulations suggested noticeable differences between the input alternatives generated by three different interpolation schemes. Differences are shown in overall simulation error against the observations, degree of explained variability, and seasonal volumes. Simulated streamflows also showed different characteristics in mean, maximum, minimum, and peak flows. Given the same parameter optimization technique, LWP input showed least streamflow error in Alapaha basin and CMLR input showed least error (still very close to LWP) in Animas basin. All of the two-step interpolation inputs resulted in lower streamflow error compared to the directly interpolated inputs. ?? 2011 Springer-Verlag.

  14. Impact of deep convection on the isotopic amount effect in tropical precipitation

    NASA Astrophysics Data System (ADS)

    Tharammal, Thejna; Bala, Govindasamy; Noone, David

    2017-02-01

    The empirical "amount effect" observed in the distribution of stable water isotope ratios in tropical precipitation is used in several studies to reconstruct past precipitation. Recent observations suggest the importance of large-scale organized convection systems on amount effect. With a series of experiments with Community Atmospheric Model version 3.0 with water isotope tracers, we quantify the sensitivity of amount effect to changes in modeled deep convection. The magnitude of the regression slope between long-term monthly precipitation amount and isotope ratios in precipitation over tropical ocean reduces by more than 20% with a reduction in mean deep convective precipitation by about 60%, indicating a decline in fractionation efficiency. Reduced condensation in deep convective updrafts results in enrichment of lower level vapor with heavier isotope that causes enrichment in total precipitation. However, consequent increases in stratiform and shallow convective precipitation partially offset the reduction in the slope of amount effect. The net result is a reduced slope of amount effect in tropical regions except the tropical western Pacific, where the effects of enhanced large-scale ascent and increased stratiform precipitation prevail over the influence of reduced deep convection. We also find that the isotope ratios in precipitation are improved over certain regions in the tropics with reduced deep convection, showing that analyses of isotope ratios in precipitation and water vapor are powerful tools to improve precipitation processes in convective parameterization schemes in climate models. Further, our study suggests that the precipitation types over a region can alter the fractionation efficiency of isotopes with implications for the reconstructions of past precipitation.

  15. Uncertainty Assessments of Spatially-Interpolated Missing Precipitation Data Estimates

    NASA Astrophysics Data System (ADS)

    Teegavarapu, R. S.

    2013-12-01

    Deterministic spatial interpolation models routinely used for infilling missing precipitation data do not provide any assessments of uncertainty in the estimates. Spatial interpolation is inevitable when temporal autocorrelation is low. Spatial and temporal partitioning of observation sites and data respectively will lead to several possible combinations of imputed data sets. Methodology using single-model multiple imputation-based optimal spatial interpolation is developed in this study. Different models are developed adopting re-sampling techniques for data and combinations of observation points in space are developed using the proposed methodology. Applicability of the methodology is tested for evaluating uncertainty associated with imputed precipitation data at several sites in a temperature climate region of the U.S. Uncertainty assessments of the imputed data and characteristics of filled data are evaluated using several indices and conclusions are drawn.

  16. East Asian Monsoon controls on the inter-annual variability in precipitation isotope ratio in Japan

    NASA Astrophysics Data System (ADS)

    Kurita, N.; Fujiyoshi, Y.; Nakayama, T.; Matsumi, Y.; Kitagawa, H.

    2015-02-01

    To elucidate the mechanism for how the East Asian Monsoon (EAM) variability have influenced the isotope proxy records in Japan, we explore the primary driver of variations of precipitation isotopes at multiple temporal scales (event, seasonal and inter-annual scales). Using a new 1-year record of the isotopic composition of event-based precipitation and continuous near-surface water vapor at Nagoya in central Japan, we identify the key atmospheric processes controlling the storm-to-storm isotopic variations through an analysis of air mass sources and rainout history during the transport of moisture to the site, and then apply the identified processes to explain the inter-annual isotopic variability related to the EAM variability in the historical 17-year long Tokyo station record in the Global Network of Isotopes in Precipitation (GNIP). In the summer, southerly flows transport moisture with higher isotopic values from subtropical marine regions and bring warm rainfall enriched with heavy isotopes. The weak monsoon summer corresponds to enriched isotopic values in precipitation, reflecting higher contribution of warm rainfall to the total summer precipitation. In the strong monsoon summer, the sustaining Baiu rainband along the southern coast of Japan prevents moisture transport across Japan, so that the contribution of warm rainfall is reduced. In the winter, storm tracks are the dominant driver of storm-to-storm isotopic variation and relatively low isotopic values occur when a cold frontal rainband associated with extratropical cyclones passes off to the south of the Japan coast. The weak monsoon winter is characterized by lower isotopes in precipitation, due to the distribution of the cyclone tracks away from the southern coast of Japan. In contrast, the northward shift of the cyclone tracks and stronger development of cyclones during the strong monsoon winters decrease the contribution of cold frontal precipitation, resulting in higher isotopic values in

  17. Variogram analysis of stable oxygen isotope composition of daily precipitation over the British Isles

    NASA Astrophysics Data System (ADS)

    Kohán, Balázs; Tyler, Jonathan; Jones, Matthew; Kern, Zoltán

    2017-04-01

    Water stable isotopes are important natural tracers in the hydrological cycle on global, regional and local scales. Daily precipitation water samples were collected from 70 sites over the British Isles on the 23rd, 24th, and 25th January, 2012 [1]. Samples were collected as part of a pilot study for the British Isotopes in Rainfall Project, a community engagement initiative, in collaboration with volunteer weather observers and the UK Met Office. Spatial correlation structure of daily precipitation stable oxygen isotope composition (δ18OP) has been explored by variogram analysis [2]. Since the variograms from the raw data suggested a pronounced trend, owing to the spatial trend discussed in the original study [1], a second order polynomial trend was removed from the raw δ18OP data and variograms were calculated on the residuals. Directional experimental semivariograms were calculated (steps: 10°, tolerance: 30°) and aggregated into variogram surface plots to explore the spatial dependence structure of daily δ18OP. Each daily data set produced distinct variogram plots. -A well expressed anisotropic structure can be seen for Jan 23. The lowest and highest variance was observed in the SW-NE and NNE-SSW direction, respectively. Meteorological observations showed that the majority of the atmospheric flow was SW on this day, so the direction of low variance seems to reflect this flow direction, while the maximum variance might reflect the moisture variance near the elongation of the frontal system. -A less characteristic but still expressed anisotropic structure was found for Jan 24 when a warm front passed the British Isles perpendicular to the east coast, leading to a characteristic east-west δ18OP gradient suggestive of progressive rainout. The low variance central zone has a 100 km radius which might correspond well to the width of the warm front zone. Although, the axis of minimum variance was similarly SW-NE, the zone of maximum variance was broader and

  18. Optimal Spatial Interpolation Method for precipitation data in China

    NASA Astrophysics Data System (ADS)

    Yating, Chen

    2017-04-01

    The spatial distribution of precipitation plays a key role for water resources management and flood & drought prediction. In this study, based on precipitation data (1981-2010) and DEM data from 2160 meteorological stations of China, we will produce a nice spatial distribution of precipitation of China by using eight interpolation methods, including Inverse Distance Weight method, Radial Basis Function method, Global Polynomial Interpolation method, Local Polynomial Interpolation method, Ordinary Kriging method, Simple Kriging method, Universal Kriging method and Empirical Bayesian Kriging method. By using cross-validation, we find that (a) The Empirical Bayesian Kriging method is optimal for the whole China. (b) For different land types, the Radial Basis Function method is optimal for plain areas, while the Empirical Bayesian Kriging method is optimal for mountainous areas. (c) The optimal methods for Yellow River basin, Yangtze river basin and Pearl River basin are Universal Kriging method, Ordinary Kriging method, Empirical Bayesian Kriging method, respectively.

  19. Linking Hydrogen (δ2H) Isotopes in Feathers and Precipitation: Sources of Variance and Consequences for Assignment to Isoscapes

    PubMed Central

    Hobson, Keith A.; Van Wilgenburg, Steven L.; Wassenaar, Leonard I.; Larson, Keith

    2012-01-01

    Background Tracking small migrant organisms worldwide has been hampered by technological and recovery limitations and sampling bias inherent in exogenous markers. Naturally occurring stable isotopes of H (δ2H) in feathers provide an alternative intrinsic marker of animal origin due to the predictable spatial linkage to underlying hydrologically driven flow of H isotopes into foodwebs. This approach can assess the likelihood that a migrant animal originated from a given location(s) within a continent but requires a robust algorithm linking H isotopes in tissues of interest to an appropriate hydrological isotopic spatio-temporal pattern, such as weighted-annual rainfall. However, a number of factors contribute to or alter expected isotopic patterns in animals. We present results of an extensive investigation into taxonomic and environmental factors influencing feather δ2H patterns across North America. Principal Findings Stable isotope data were measured from 544 feathers from 40 species and 140 known locations. For δ2H, the most parsimonious model explaining 83% of the isotopic variance was found with amount-weighted growing-season precipitation δ2H, foraging substrate and migratory strategy. Conclusions/Significance This extensive H isotopic analysis of known-origin feathers of songbirds in North America and elsewhere reconfirmed the strong coupling between tissue δ2H and global hydrologic δ2H patterns, and accounting for variance associated with foraging substrate and migratory strategy, can be used in conservation and research for the purpose of assigning birds and other species to their approximate origin. PMID:22509393

  20. Linking hydrogen (δ2H) isotopes in feathers and precipitation: sources of variance and consequences for assignment to isoscapes.

    PubMed

    Hobson, Keith A; Van Wilgenburg, Steven L; Wassenaar, Leonard I; Larson, Keith

    2012-01-01

    Tracking small migrant organisms worldwide has been hampered by technological and recovery limitations and sampling bias inherent in exogenous markers. Naturally occurring stable isotopes of H (δ(2)H) in feathers provide an alternative intrinsic marker of animal origin due to the predictable spatial linkage to underlying hydrologically driven flow of H isotopes into foodwebs. This approach can assess the likelihood that a migrant animal originated from a given location(s) within a continent but requires a robust algorithm linking H isotopes in tissues of interest to an appropriate hydrological isotopic spatio-temporal pattern, such as weighted-annual rainfall. However, a number of factors contribute to or alter expected isotopic patterns in animals. We present results of an extensive investigation into taxonomic and environmental factors influencing feather δ(2)H patterns across North America. Stable isotope data were measured from 544 feathers from 40 species and 140 known locations. For δ(2)H, the most parsimonious model explaining 83% of the isotopic variance was found with amount-weighted growing-season precipitation δ(2)H, foraging substrate and migratory strategy. This extensive H isotopic analysis of known-origin feathers of songbirds in North America and elsewhere reconfirmed the strong coupling between tissue δ(2)H and global hydrologic δ(2)H patterns, and accounting for variance associated with foraging substrate and migratory strategy, can be used in conservation and research for the purpose of assigning birds and other species to their approximate origin.

  1. Extreme changes in stable hydrogen isotopes and precipitation characteristics in a landfalling Pacific storm

    USGS Publications Warehouse

    Coplen, T.B.; Neiman, P.J.; White, A.B.; Landwehr, J.M.; Ralph, F.M.; Dettinger, M.D.

    2008-01-01

    With a new automated precipitation collector we measured a remarkable decrease of 51??? in the hydrogen isotope ratio (?? 2H) of precipitation over a 60-minute period during the landfall of an extratropical cyclone along the California coast on 21 March 2005. The rapid drop in ??2H occurred as precipitation generation transitioned from a shallow to a much deeper cloud layer, in accord with synoptic-scale ascent and deep "seeder-feeder" precipitation. Such unexpected ?? 2H variations can substantially impact widely used isotope-hydrograph methods. From extreme ??2H values of -26 and -78???, we calculate precipitation temperatures of 9.7 and -4.2??C using an adiabatic condensation isotope model, in good agreement with temperatures estimated from surface observations and radar data. This model indicates that 60 percent of the moisture was precipitated during ascent as temperature decreased from 15??C at the ocean surface to -4??C above the measurement site.

  2. The Spatial and Temporal Pattern of Heavy Precipitation in Seoul

    NASA Astrophysics Data System (ADS)

    Lee, K. S.; Yu, J.; Im, J.; Jin, R.

    2014-12-01

    1.Introduction Combined with summer heavy rainfall and urbanization today's urban area face higher frequency of heavy rainfall with higher intensity in summer than before. Heavy rainfall in short time makes it low elevation area to be susceptible to more flooding than before. According to KMA it is announced as heavy rainfall warning whose precipitation amount is equal to or greater than 150mm per 12 hours. And sometimes, these rainfall events bring out severe disasters such as the case of flooding in Gangnam Station, Daechi Station and landslides which resulted in 20 person death in downtown Seoul on July 27th, 2011. Thus, the purpose of this study is to investigate the spatial and temporal pattern of heavy precipitation in Seoul. Ultimately it aims to contribute these results to the proper urban planning and management. 2. Materials and Methods In this study, the digital topograhic data and weather data in Seoul Metropolitan Area were used to figure out the spatial distribution of summer heavy rainfall. The precipitation data in summer (June to Sep.) season were used to detect the recent changes of temporal and spatial features from 1995 to 2014 (20 years) using Automatic Weather tation (AWS) data in Seoul Metropolitan Area. The precipitation amount in summer during the past 20 years has been on the rise but rainy days have barely changed,which reveals the daily precipitation intensity has increased. After deriving the characteristic of heavy rainfall, the relationship among precipitation, topography and land uses were interpreted and discussed. This study is to investigate the characteristics of flood prone area by focusing topographic and land use characteristics. Ultimately it contributes to prepare the guideline for flood preventive urban plannig.

  3. Isotopic characterization of mountain precipitation along the eastern flank of the Andes between 32.5 - 35°S

    NASA Astrophysics Data System (ADS)

    Hoke, G. D.; Aranibar, J. N.; Viale, M.; Araneo, D. C.; LLano, C. L.

    2011-12-01

    Data describing the isotopic composition of precipitation in the Andes are sparse: on the South American continent one IAEA Global Network of Isotopes in Precipitation (GNIP) station above 1500 m elevation exists south of La Paz. Better spatial density is necessary to improve our understanding of isotopes in mountain precipitation, which has implications for how to interpret isotopic information from the geologic record and the validation of isotope tracking modules in climate models. We present finding from two-years of quasi-monthly precipitation collection on the eastern flank of the Andes between 32.5 and 35°S latitude. A total of 123 samples were collected from 10 stations from Setember 2008 until September 2010. North of 33°S, the 2500 m average elevation Precordillera forms a steep front orographic barrier and the 2000 m elevation Uspallata Valley separates the Precordillera from the high Andes to the East. South of 33°S the Precordillera ends and the Andes return to a simple linear morphology. The low-leeward (eastern) side of the Andes receives predominately summer precipitation from convective storms, usually triggered by daytime upslope flow or synoptic-scale easterly flow over the Precordillera. Moving westward from the low-leeward side to the range crest, the influence of the easterly summer precipitation wanes and winter spillover precipitation from mid-latitude westerly storms beings to dominate. Our results show the local meteoric water line is slightly steeper (~0.5) than the global meteoric water line and a y-intercept of 14. The most negative δ18O values vary as much as 15 per mil seasonally, while averages weighted by precipitation amount show a strong cross-barrier (elevation) dependence. At these latitudes, the weighted average precipitation δ18O values show a significant deviation from river water near the range crest. The influence of the different moisture sources, from synoptic-scale easterly or westerly flow, is distinguished by

  4. Precipitation and Seawater Isotopic Variability from Hawaii to the equator: the 2014-2015 ENSO cycle

    NASA Astrophysics Data System (ADS)

    Cobb, K. M.; Conroy, J. L.; Moerman, J. W.; Bosma, C.; Everitt, L.; Stevenson, S.; Noone, D. C.; Grothe, P. R.; Schneider, N.; Merrifield, M. A.; Farnsworth, M.

    2015-12-01

    An increasing number of paleoclimate reconstructions rely on the isotopic variability of precipitation or seawater as a proxy for past hydrological variability, even though modern-day water isotope variability is poorly constrained by observations. Nowhere is this more apparent than in the tropical Pacific, where paleo-water isotope reconstructions imply that anthropogenic climate change has driven dramatic shifts in the isotopic composition of surface waters (Nurhati et al., 2009), yet water isotope observations in this region are virtually non-existent. Here we present a new set of weekly seawater and daily precipitation isotope observations along a meridional gradient in the tropical Pacific, spanning from Hawaii (21N, 158W) to Palmyra Island (6N, 162W) to Christmas Island (2N, 157W), that spans the development and growth of the current ENSO cycle that began in 2014. We use a suite of high-quality in situ observations of ocean conditions (salinity, temperature) as well as surface meteorological measurements (relative humidity, precipitation amount, wind speed and direction) to provide an interpretive framework for the observed isotopic variations, with a focus on the expression of seasonal to interannual features in the dataset. A complementary dataset of precipitation and seawater isotopes from across the equator in the tropical Pacific basin provides additional diagnostic context. We also compare our observed isotopic variations to output from numerical simulations of precipitation and seawater isotopes in the tropical Pacific. We discuss the implications of our findings for the design of long-term monitoring programs in the tropical Pacific, as well as the interpretation of proxy-based reconstructions of seawater and precipitation water isotopes.

  5. Spatial and temporal variability of Antarctic precipitation from atmospheric methods

    SciTech Connect

    Cullather, R.L.; Bromwich, D.H.; Van Woert, M.L.

    1998-03-01

    The spatial and temporal variability of net precipitation (precipitation minus evaporation/sublimation) for Antarctica derived from the European Centre for Medium-Range Weather Forecasts operational analyses via the atmospheric moisture budget is assessed in comparison to a variety of glaciological and meteorological observations and datasets. For the 11-yr period 1985-95, the average continental value is 151 mm yr{sup {minus}1} water equivalent. Large regional differences with other datasets are identified, and the sources of error are considered. Interannual variability in the Southern Ocean storm tracks is found to be an important mechanism for enhanced precipitation minus evaporation (P-E) in both east and west Antarctica. In relation to the present findings, an evaluation of the rawinsonde method for estimating net precipitation in east Antarctica is conducted. Estimates of P-E using synthetic rawinsondes derived from the analyses are found to compare favorably to glaciological estimates. A significant upward trend of 2.4 mm yr{sup {minus}1} is found for the Antarctic continent that is consistent with findings from the National Centers for Environmental Prediction, formerly the National Meteorological Center, and the National Center for Atmospheric Research Reanalysis precipitation dataset. Despite large regional discrepancies, the general agreement on the main features of Antarctic precipitation between studies suggests that a threshold has been reached, where the assessment of the smaller terms including evaporation/sublimation and drift snow loss is required to explain the differences. 76 refs., 24 figs., 1 tab.

  6. Spatial and temporal analysis of stable isotopes in tap water across China

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Hu, H.; Tian, F.; Tie, Q.

    2015-12-01

    Stable isotopes in water (δ2H and δ18O) are important indicators of hydrological and ecological pattern and process. Water isotopes have been used to trace atmospheric moisture source, identify source of groundwater and surface water charge, reconstruct paleoclimate, and so on. Tap water appears to reflect pervasive features of regional integrated hydrological process. China is a large-size country with high variations in both environmental and geographical factors including temperature, precipitation amount, relative humidity, latitude, altitude et al. Here we present a first national-scale survey on stable isotope of tap water across China. More than 1000 tap water samples have been collected from 93 cities across China by monthly between December 2014 and November 2015. Stable isotope composition of tap water ranged from -132.1‰ to -25.6‰ (δ2H) and from -17.5‰ to -4.2‰ (δ18O). The Meteoric Water Line is δ2H = 7.77 δ18O + 5.79 (r2 = 0.95) and the LMWL of Chinese precipitation is δ2H =7.6δ18O+ 9.94 (r2= 0.97). Spatial distribution of stable isotopes present typical "continental effect", isotope values generally decrease from coastal regions to inland. Isotopes in different regions present different correlations with temperature, precipitation amount, latitude and altitude as a result of varied moisture source and local water supply. The results of the study could provide mapping information of tap water for fundamental isotope hydrological studies in different regions of China.

  7. Long-Term Precipitation Isotope Ratios (δ18O, δ2H, d-excess) in the Northeast US Reflect Atlantic Ocean Warming and Shifts in Moisture Sources

    NASA Astrophysics Data System (ADS)

    Puntsag, T.; Welker, J. M.; Mitchell, M. J.; Klein, E. S.; Campbell, J. L.; Likens, G.

    2014-12-01

    The global water cycle is exhibiting dramatic changes as global temperatures increase resulting in increases in: drought extremes, flooding, alterations in storm track patterns with protracted winter storms, and greater precipitation variability. The mechanisms driving these changes can be difficult to assess, but the spatial and temporal patterns of precipitation water isotopes (δ18O, δ2H, d-excess) provide a means to help understand these water cycle changes. However, extended temporal records of isotope ratios in precipitation are infrequent, especially in the US. In our study we analyzed precipitation isotope ratio data from the Hubbard Brook Experimental Forest in New Hampshire that has the longest US precipitation isotope record, to determine: 1) the monthly composited averages and trends from 1967 to 2012 (45 years); ; 2) the relationships between abiotic properties such as local temperatures, precipitation type, storm tracks and isotope ratio changes; and 3) the influence of regional shifts in moisture sources and/or changes in N Atlantic Ocean water conditions on isotope values. The seasonal variability of Hubbard Brook precipitation isotope ratios is consistent with other studies, as average δ18O values are ~ -15‰ in January and ~ -5 ‰ in July. However, over the 45 year record there is a depletion trend in the δ 18O values (becoming isotopically lighter with a greater proportion of 16O), which coupled with less change in δ 2H leads to increases in d-excess values from ~ -10‰ around 1970 to greater than 10‰ in 2009. These changes occurred during a period of warming as opposed to cooling local temperatures indicating other processes besides temperature are controlling long-term water isotope traits in this region. We have evidence that these changes in precipitation isotope traits are controlled in large part by an increases in moisture being sourced from a warming N Atlantic Ocean that is providing evaporated, isotopically

  8. Mercury isotope fractionation during precipitation of metacinnabar (β-HgS) and montroydite (HgO).

    PubMed

    Smith, Robin S; Wiederhold, Jan G; Kretzschmar, Ruben

    2015-04-07

    To utilize stable Hg isotopes as a tracer for Hg cycling and pollution sources in the environment, it is imperative that fractionation factors for important biogeochemical processes involving Hg are determined. Here, we report experimental results on Hg isotope fractionation during precipitation of metacinnabar (β-HgS) and montroydite (HgO). In both systems, we observed mass-dependent enrichments of light Hg isotopes in the precipitates relative to the dissolved Hg. Precipitation of β-HgS appeared to follow equilibrium isotope fractionation with an enrichment factor ε(202)Hg(precipitate-supernatant) of -0.63‰. Precipitation of HgO resulted in kinetic isotope fractionation, which was described by a Rayleigh model with an enrichment factor of -0.32‰. Small mass-independent fractionation was observed in the HgS system, presumably related to nuclear volume fractionation. We propose that Hg isotope fractionation in the HgS system occurred in solution during the transition of O- to S-coordination of Hg(II), consistent with theoretical predictions. In the HgO system, fractionation was presumably caused by the faster precipitation of light Hg isotopes, and no isotopic exchange between solid and solution was observed on the timescale investigated. The results of this work emphasize the importance of Hg solution speciation and suggest that bonding partners of Hg in solution complexes may control the overall isotope fractionation. The determined fractionation factor and mechanistic insights will have implications for the interpretation of Hg isotope signatures and their use as an environmental tracer.

  9. The isotopic composition of precipitation and surface layers of glaciers in Central Altai

    NASA Astrophysics Data System (ADS)

    Papina, Tatyana; Malygina, Natalia; Eyrikh, Alla

    2014-05-01

    Please fill in The isotopic composition of precipitation and ice of Altai glaciers can be successfully used to determine the sources of precipitation (water vapor) and trajectories of air masses coming to the Altai territory, to study the modern and paleoclimatic changes in this region and other applied climate and environmental challenges. This paper presents the results of the study of seasonal changes in the isotopic composition of precipitation and surface layers of warm and cold glaciers in Central Altai. The isotopic composition of warm glaciers (North Chui Ridge) significantly (by more than 6.5 ) facilitated relatively mean value of ice core layers from cold Belukha glacier. This difference primarily may be due to: 1) with multiple cryogenic isotope fractionation of warm glaciers surface, which leads to the formation of significantly lighter ice isotopic composition; 2) accumulation of the edge portion of the warm glaciers occurs mainly due to the winter solid precipitation. The isotopic composition of summer precipitation (July 2013) in the Central Altai ranged from -7.55 to -10.28 0/00for δ18O and from -135.20 to -136.04 0/00 for δD, which indicates that the formation of precipitation fallen on the earth surface of precipitated on the surface glacier great contribution moisture exchange processes arising from the passage of moist Atlantic air masses over the territory of the Aral- Caspian region. Integrated use of data on the trajectory of air masses (model HYSPLIT), synoptic situation and the isotopic composition of precipitation can detect features of the formation of precipitation . For example , it was shown to cause rainfall in the Central Altai July 16, 2013 was the formation of occlusions of Altai, and the moisture in the air mass moving over the continent to weak evaporative fractionation .

  10. Moisture sources of precipitation over Postojna (Slovenia) and implication of its oxygen isotope composition

    NASA Astrophysics Data System (ADS)

    Krklec, Kristina; Domínguez-Villar, David; Lojen, Sonja

    2016-04-01

    The source of moisture is an important part of the hydrological cycle that affects climate system. Potentially, moisture sources are important controls of the isotope composition of precipitation, but their studies in the continental mid- and low-latitudes are still scarce due to the complexity of general circulation models with integrated isotope modules. We identify moisture uptake locations of precipitation over Postojna (Slovenia) for period from 2009 to 2013. By using HYSPLIT trajectory model of NOAA we did 5-day reconstruction of air mass history for the days with precipitation and determination of moisture uptake locations along back trajectories. Moisture uptake locations were identified along each trajectory using HYSPLIT output data and standard equations for saturation humidity mixing ratio, saturation vapour pressure and specific humidity. Although NNE winds were prevailing during the period 2001-2014, our analysis showed that during this period around 45% of the precipitation over Postojna originated from Mediterranean and south Atlantic area, with majority of locations originated in the Adriatic Sea. On the other hand, 41% of precipitation originated from moisture recycled over continents, predominantly from Pannonian basin. The comparison of monthly oxygen isotope composition of precipitation with the percentage of precipitation originated in different source regions shows a significant correlation only for the north Atlantic region. However, less than 7% of the variability of oxygen isotope composition of precipitation is associated with this moisture source. Multivariable analyses of source regions do not explain any additional variability of the oxygen isotope composition of precipitation over Postojna. This research shows that at this location, although significant, moisture sources are not important controls of the oxygen isotope composition of precipitation.

  11. Winter Precipitation Isotope Gradients (δ18O) of the Contiguous USA and Their Relationship to the Pacific/North American (PNA) Pattern

    NASA Astrophysics Data System (ADS)

    Liu, Z.; Bowen, G. J.; Welker, J. M.

    2011-12-01

    This study investigates the synoptic-dynamic relationship between Pacific/North American (PNA) pattern and winter precipitation isotopes of the contiguous USA using 2-year (1990 and 1992) USNIP (the United States Network for Isotopes in Precipitation) dataset. We find that patterns in the spatial gradient of precipitation isotope values reflect the position of the polar jet stream and juxtaposition of air masses associated with variation in the PNA pattern. During the positive PNA winter, a southward shift of zones of steep δ18O gradients in the eastern USA coincides with southward displacement of the polar jet stream, which leads to a greater frequency of polar air masses and typically depleted δ18O values in the region. A coincident eastward shift in high-gradient zones in the western USA is related to more frequent penetration of tropical air masses, which in juxtaposition with polar air in the mid-continent leads to higher gradient values in the western region. Our findings highlight the importance of PNA pattern in determining spatial patterns of precipitation isotopes, with implications for interpretations of paleo-water isotope values and isotopic applications to study modern hydrological processes.

  12. North American precipitation isotope (δ18O) zones revealed in time series modeling across Canada and northern United States

    NASA Astrophysics Data System (ADS)

    Delavau, C.; Chun, K. P.; Stadnyk, T.; Birks, S. J.; Welker, J. M.

    2015-02-01

    Delineating spatial patterns of precipitation isotopes ("isoscapes") is becoming increasingly important to understand the processes governing the modern water isotope cycle and their application to migration forensics, climate proxy interpretation, and ecohydrology of terrestrial systems. However, the extent to which these patterns can be empirically predicted across Canada and the northern United States has not been fully articulated, in part due to a lack of time series precipitation isotope data for major regions of North America. In this study, we use multiple linear regressions of CNIP, GNIP, and USNIP observations alongside climatological variables, teleconnection indices, and geographic indicators to create empirical models that predict the δ18O of monthly precipitation (δ18Oppt) across Canada and the northern United States. Five regionalization approaches are used to separate the study domain into isotope zones to explore the effect of spatial grouping on model performance. Stepwise regression-derived parameterizations quantified by permutation testing indicate the significance of precipitable water content and latitude as predictor variables. Within the Canadian Arctic and eastern portion of the study domain, models from all regionalizations capture the interannual and intraannual variability of δ18Oppt. The Pacific coast and northwestern portions of the study domain show less agreement between models and poorer model performance, resulting in higher uncertainty in simulations throughout these regions. Long-term annual average δ18Oppt isoscapes are generated, highlighting the uncertainty in the regionalization approach as it compounds over time. Additionally, monthly time series simulations are presented at various locations, and model structure uncertainty and 90% bootstrapped prediction bounds are detailed for these predictions.

  13. Heterodynes dominate precipitation isotopes in the East Asian monsoon region, reflecting interaction of multiple climate factors

    NASA Astrophysics Data System (ADS)

    Thomas, Elizabeth K.; Clemens, Steven C.; Sun, Youbin; Prell, Warren L.; Huang, Yongsong; Gao, Li; Loomis, Shannon; Chen, Guangshan; Liu, Zhengyu

    2016-12-01

    For the past decade, East Asian monsoon history has been interpreted in the context of an exceptionally well-dated, high-resolution composite record of speleothem oxygen isotopes (δ18Ocave) from the Yangtze River Valley. This record is characterized by a unique spectral response, with variance concentrated predominantly within the precession band and an enigmatic lack of variance at the eccentricity and obliquity bands. Here we examine the spectral characteristics of all existing >250-kyr-long terrestrial water isotope records in Asia, including a new water isotope record using leaf wax hydrogen isotope ratios from the Chinese Loess Plateau. There exist profound differences in spectral characteristics among all orbital-scale Asian water isotope records. We demonstrate that these differences result from latitudinal gradients in the influence of the winter and summer monsoons, both of which impact climate and water isotopes throughout East Asia. Water isotope records therefore do not reflect precipitation during a single season or from a single circulation system. Rather, water isotope records in East Asia reflect the complex interplay of oceanic and continental moisture sources, operating at multiple Earth-orbital periods. These non-linear interactions are reflected in water isotope spectra by the presence of heterodynes. Although complex, we submit that water isotope records, when paired with rapidly developing isotope-enabled model simulations, will have the potential to elucidate mechanisms causing seasonal precipitation variability and moisture source variability in East Asia.

  14. Slovenian Network of Isotopes in Precipitation (SLONIP) - a review of activities in the period 1981-2015

    NASA Astrophysics Data System (ADS)

    Vreča, Polona; Kanduč, Tjaša; Kocman, David; Lojen, Sonja; Štrok, Marko; Robinson, Johanna Amalia

    2017-04-01

    The importance of collecting data on the water isotope composition of precipitation in the frame of the Global Network of Isotopes in Precipitation (GNIP) has been steadily increasing since it was initiated by the IAEA and the WMO in 1958, particularly in the last decade (Terzer et al., 2013). GNIP provides an important database for water resources management, verifying and improving atmospheric circulation models, studying climates and the interactions between water in the atmosphere and the biosphere, providing baseline information for the authentication of commodities, etc. Geographical diversity of Slovenia influences the climate and also the water cycle considerably, therefore monitoring of isotopes in precipitation is of particular interest. A review on monitoring of isotopes in precipitation was performed and information about sampling, analytical methods, available data and their evaluation was collected for the period 1981-2015. The first regular and systematic monitoring began in 1981 in Ljubljana (Pezdič, 1999). Later, a programme of collecting new data at a higher spatial density and temporal frequency in different parts of the country by different research groups has been initiated and was extended several times. Consequently, the number of sampling locations has grown within Slovenian Network of Isotopes in Precipitation (SLONIP) and altogether isotopes were monitored at more than 30 different locations countrywide (Vreča and Malenšek, 2016). However, the network is still not a part of a national monitoring programme, such as that operating in some European countries, for example, in Switzerland (Schürch et al., 2003). Only part of Slovenian data is available in GNIP database. Based on the collected data, we identified gaps in the research and made recommendations for future monitoring in the frame of the SLONIP. The list of main gaps includes limited information about sampling (e.g. missing coordinates, type of collector, period, frequency

  15. Temporal and Spatial Variation of Surface Water Stable Isotopes in the Marys River Basin, Oregon

    NASA Astrophysics Data System (ADS)

    Nickolas, L. B.; Segura, C.; Brooks, J. R.

    2015-12-01

    Understanding the temporal and spatial variability of water sources within a basin is vital to our ability to manage the impacts of climate variability and land cover change. Water stable isotopes can be used as a tool to determine geographic and seasonal sources of water at the basin scale. Previous studies in the Coastal Range of Oregon reported that the variation in the isotopic signatures of surface water does not conform to the commonly observed "rainout effect", which exhibits a trend of increasing isotopic depletion with rising elevation. The primary purpose of this research is to investigate the mechanisms governing seasonal and spatial variations in the isotopic signature of surface waters within the Marys River Basin, located in the Oregon Coastal Range. We hypothesize that catchment orientation, drainage area, geology, and topography act as controlling factors on groundwater flow, storage, and atmospheric moisture cycling, which explain variations in source water contribution. Surface water and precipitation samples were collected every 2-3 weeks for isotopic analysis of δ18O and δ2H for one year. Preliminary results indicate a significant difference (p<0.001) in isotopic signature between watersheds underlain by basalt and sandstone. The degree of separation is the most distinct during the summer when low flows likely reflect deeper groundwater sources, whereas isotopic signatures during the rainy season (fall & winter) show a greater degree of similarity between the two lithologies. These findings indicate that the more permeable sandstone formations may be hydrologically connected to enriched water sources on the windward side of the Coastal Range that sustain baseflow within catchments on the leeward side, while streams draining basalt catchments are fed by a more depleted source of water (e.g. precipitation originating within the Marys River Basin).

  16. Carbon isotope fractionation during calcium carbonate precipitation induced by ureolytic bacteria

    NASA Astrophysics Data System (ADS)

    Millo, Christian; Dupraz, S.; Ader, M.; Guyot, F.; Thaler, C.; Foy, E.; Ménez, B.

    2012-12-01

    Ureolytic bacteria have been proposed as model organisms to investigate the potential of subsurface microorganisms to enhance carbon capture and storage through solubility- and mineral-trapping of CO2 induced by bacterial ureolysis and carbonate formation. Ideally, CO2 incorporation into carbonates can be readily traced using carbon isotope measurements. However, the carbon isotope systematics of bacterial ureolysis and associated carbonate precipitation is still poorly known. We determined the carbon isotope fractionations expressed during ureolysis and carbonate precipitation induced by Sporosarcina pasteurii at 30 °C. Our results indicate that bacterial ureolysis proceeds as a Rayleigh distillation characterized by a 13C-enrichment factor equal to -12.5‰. As precipitation proceeds, the δ13C value of CaCO3, initially 1-2.1‰ lower than that of dissolved inorganic carbon (DIC), evolves progressively until it is 0.5‰ higher than that of the DIC, i.e. close to the value predicted for isotopic equilibrium. The minor isotope disequilibrium at the onset of precipitation and its rapid evolution towards isotopic equilibrium point to bacterial carbonates as reliable recorders of the carbon isotope composition of DIC. This corroborates the potential utility of 13C-tracing for the quantification of microbially-induced CO2 sequestration into solid carbonates and DIC.

  17. Effect of storage on the isotopic composition of nitrate in bulk precipitation.

    PubMed

    Spoelstra, John; Schiff, Sherry L; Jeffries, Dean S; Semkin, Ray G

    2004-09-15

    Stable isotopic analysis of atmospheric nitrate is increasingly employed to study nitrate sources and transformations in forested catchments. Large volumes have typically been required for delta18O and delta15N analysis of nitrate in precipitation due to relatively low nitrate concentrations. Having bulk collectors accumulate precipitation over an extended time period allows for collection of the required volume as well as reducing the total number of analyses needed to determine the isotopic composition of mean annual nitrate deposition. However, unfiltered precipitation left in collectors might be subject to microbial reactions that can alter the isotopic signature of nitrate in the sample. Precipitation obtained from the Turkey Lakes Watershed was incubated under conditions designed to mimic unfiltered storage in bulk precipitation collectors and monitored for changes in nitrate concentration, delta15N, and delta18O. Results of this experiment indicated that no detectable nitrate production or assimilation occurred in the samples during a two-week incubation period and that atmospheric nitrate isotopic ratios were preserved. The ability to collect unfiltered precipitation samples for an extended duration without alteration of nitrate isotope ratios is particularly useful at remote study sites where daily retrieval of samples may not be feasible.

  18. Understanding the Sahelian water budget through the isotopic composition of water vapor and precipitation

    NASA Astrophysics Data System (ADS)

    Risi, Camille; Bony, Sandrine; Vimeux, FrançOise; Frankenberg, Christian; Noone, David; Worden, John

    2010-12-01

    The goal of this paper is to investigate the added value of water isotopic measurements to estimate the relative influence of large-scale dynamics, convection, and land surface recycling on the Sahelian water budget. To this aim, we use isotope data in the lower tropospheric water vapor measured by the SCIAMACHY and TES satellite instruments and in situ precipitation data from the Global Network for Isotopes in Precipitation and collected during the African Monsoon Multidisciplinary Analysis field campaign, together with water-tagging experiments with the Laboratoire de Météorologie Dynamique general circulation model (LMDZ) fitted with isotopes. We show that some isotopic biases in LMDZ reveal the misrepresentation of dehydrating processes that would be undetected without isotopic measurements. In dry regions, the vapor isotopic composition is primarily controlled by the intensity of the air dehydration. In addition, it may also keep some memory of dehydration pathways that is erased in the humidity distribution, namely the relative contribution of dehydration in the tropical upper troposphere versus midlatitudes. In wet regions, vapor and rain isotope compositions are primarily controlled by changes in convection, through rain reevaporation and through the progressive depletion of the vapor by convective mixing along air mass trajectories. Gradients in vapor isotope composition along air mass trajectories may help estimate continental recycling intensity, provided that we could quantify the effect of convection on the isotopic composition of water vapor.

  19. Influence of sea ice cover on high latitude precipitation: Inferences from precipitation isotope measurements and a 2D model

    NASA Astrophysics Data System (ADS)

    Posmentier, E. S.; Faiia, A.; Feng, X.; Michel, F. A.

    2009-12-01

    The most widely cited climate feedback in the Arctic region is ice cover. Warming climate reduces the sea ice extent, which causes a lower surface albedo, resulting in more absorbed insolation and further warming - a positive feedback. Conversely, warming is also likely to result in increased Arctic evaporation and precipitation, leading to increased snow cover and a higher Arctic terrestrial albedo, which would cause cooling - a negative feedback. The balance between these feedbacks must be understood and quantified in order to predict climate response to influences such as increased greenhouse gases. Here, we use measurements of high latitude precipitation isotopes and a 2D model to investigate interannual variability in the contributions of subtropical and Arctic vapor sources to Arctic precipitation. In a previous study, we used isotopic ratios alone to investigate the sources of moisture to the Arctic. We found significant positive relationships between ice area and the d-excess of precipitation on both interannual and seasonal timescales, an expected result under the assumption that sea ice prevents evaporation from the sea surface and consequently reduces the contribution of Arctic moisture with low d-excess values to Arctic precipitation. In this work, we go a step further with an attempt to estimate the influence of sea ice cover on Arctic evaporation using a 2D model and constraining it with high latitude isotopic measurements. The 2D model is a vertical-meridional mass conservation model for H2O, HDO, and H218O with prescribed atmospheric circulation and temperatures. For each isotope, the rates of surface evaporation, sublimation, precipitation, and reevaporation of falling hydrometeors are calculated, and values of the humidity and isotopic concentrations of both vapor and hydrometeors are computed interdependently with the four process rates.. The model fractionation associated with the four processes is based primarily on the work of Jouzel and

  20. [Relationships between stable isotopes in precipitation in Wolong and monsoon activity].

    PubMed

    Xu, Zhen; Liu, Yu-hong; Wang, Zhong-sheng; Cui, Jun; Xu, Qing; An, Shu-qing; Liu, Shi-rong

    2008-04-01

    Stable isotopic analyses with precipitation, air temperature, wind direction and wind speed were performed in the Wolong Nature Reserve from July, 2003 to July, 2004. Results showed that d-excess values were (8.4 +/- 7.4) per thousand, (- 7.4 +/- 12.5) per thousand and (12.5 +/- 12.1) per thousand in precipitation events from April to August, September to October and November to March, respectively. Stable isotopic characteristics and d-excess values indicated that precipitation was mainly brought by the East Asia monsoon from ocean surface moisture from April to August, by the Indian summer monsoon from ocean moisture which extremely affected by rainout (strong depletion of heavy isotope) from September to October, and by Westerly from inland evaporation and local evaporation from November to March. Significant negative correlations between isotopic values and precipitation, which was amount effect, were found from April to October (r = - 0.389 for deltaD and r = - 0.380 for delta18O, p < 0.05, respectively) . Temperature effect also might affect isotopic values in precipitation (p < or = 0.10). During the active period of the East Asia monsoon and the Indian summer monsoon, stable isotopes in precipitation events had significant negative correlations with south wind index (r = - 0.354 for deltaD and r = - 0.390 for delta18O, p < 0.05, respectively), indicating that isotopic values closely associated with the origin and transport of moisture, and especially the Indian summer monsoon could bring vapors with very low isotopic values and d-excess values.

  1. Relating isotopic composition of precipitation to atmospheric patterns and local moisture recycling

    NASA Astrophysics Data System (ADS)

    Logan, K. E.; Brunsell, N. A.; Nippert, J. B.

    2016-12-01

    Local land management practices such as irrigation significantly alter surface evapotranspiration (ET), regional boundary layer development, and potentially modify precipitation likelihood and amount. How strong this local forcing is in comparison to synoptic-scale dynamics, and how much ET is recycled locally as precipitation are areas of great uncertainty and are especially important when trying to forecast the impact of local land management strategies on drought mitigation. Stable isotope analysis has long been a useful tool for tracing movement throughout the water cycle. In this study, reanalysis data and stable isotope samples of precipitation events are used to estimate the contribution of local moisture recycling to precipitation at the Konza Prairie LTER - located in the Great Plains, downwind of intensive agricultural areas. From 2001 to 2014 samples of all precipitation events over 5mm were collected and 18O and D isotopes measured. Comparison of observed precipitation totals and MERRA and ERA-interim reanalysis totals is used to diagnose periods of strong local moisture contribution (especially from irrigation) to precipitation. Large discrepancies in precipitation between observation and reanalysis, particularly MERRA, tend to follow dry periods during the growing season, presumably because while ERA-Interim adjusts soil moisture using observed surface temperature and humidity, MERRA includes no such local soil moisture adjustment and therefore lacks potential precipitation feedbacks induced by irrigation. The δ18O and δD signature of local irrigation recycling is evaluated using these incongruous observations. Self-organizing maps (SOM) are then used to identify a comprehensive range of synoptic conditions that result in precipitation at Konza LTER. Comparison of isotopic signature and SOM classification of rainfall events allows for identification of the primary moisture source and estimation of the contribution of locally recycled moisture. The

  2. Can oxygen stable isotopes be used to track precipitation moisture source in vascular plant-dominated peatlands?

    NASA Astrophysics Data System (ADS)

    Amesbury, Matthew J.; Charman, Dan J.; Newnham, Rewi M.; Loader, Neil J.; Goodrich, Jordan; Royles, Jessica; Campbell, David I.; Keller, Elizabeth D.; Baisden, W. Troy; Roland, Thomas P.; Gallego-Sala, Angela V.

    2015-11-01

    Variations in the isotopic composition of precipitation are determined by fractionation processes which occur during temperature- and humidity-dependent phase changes associated with evaporation and condensation. Oxygen stable isotope ratios have therefore been frequently used as a source of palaeoclimate data from a variety of proxy archives, which integrate this signal over time. Applications from ombrotrophic peatlands, where the source water used in cellulose synthesis is derived solely from precipitation, have been mostly limited to Northern Hemisphere Sphagnum-dominated bogs, with few in the Southern Hemisphere or in peatlands dominated by vascular plants. New Zealand (NZ) provides an ideal location to undertake empirical research into oxygen isotope fractionation in vascular peatlands because single taxon analysis can be easily carried out, in particular using the preserved root matrix of the restionaceous wire rush (Empodisma spp.) that forms deep Holocene peat deposits throughout the country. Furthermore, large gradients are observed in the mean isotopic composition of precipitation across NZ, caused primarily by the relative influence of different climate modes. Here, we test whether δ18O of Empodisma α-cellulose from ombrotrophic restiad peatlands in NZ can provide a methodology for developing palaeoclimate records of past precipitation δ18O. Surface plant, water and precipitation samples were taken over spatial (six sites spanning >10° latitude) and temporal (monthly measurements over one year) gradients. A link between the isotopic composition of root-associated water, the most likely source water for plant growth, and precipitation in both datasets was found. Back-trajectory modelling of precipitation moisture source for rain days prior to sampling showed clear seasonality in the temporal data that was reflected in root-associated water. The link between source water and plant cellulose was less clear, although mechanistic modelling predicted mean

  3. Oxygen isotope values of precipitation and the thermal climate in Europe during the middle to late Weichselian ice age

    NASA Astrophysics Data System (ADS)

    Arppe, L.; Karhu, J. A.

    2010-05-01

    The oxygen isotope compositions of 28 mammoth tooth enamel samples from Estonia, Latvia, Lithuania, Poland and Denmark provide new quantitative records of the middle to late Weichselian climate in northern Europe. The new δ18O data was combined with records of oxygen isotope values from earlier investigations on European mammoth tooth enamel and palaeogroundwaters to study the spatial patterns and temporal variations in the oxygen isotope composition of precipitation and the thermal climate over much of Europe. The reconstructed geographical distribution of δ18O in precipitation during 52-24 ka reflects the progressive isotopic depletion of air masses moving northeast, consistent with a westerly source of moisture for the entire region, and a circulation pattern similar to that of the present-day. Regional long-term average δ18O w values were 0.6-4.1‰ lower than at present, the largest changes recorded for the currently maritime influenced southern Sweden and the Baltic region. The application of regionally varied δ/ T-slopes, estimated from palaeogroundwater data and modern correlations, yield reasonable estimates of glacial surface temperatures in Europe and imply 2-9 °C lower long-term mean annual surface temperatures during the glacial period.

  4. Stable-isotope ratios of hydrogen and oxygen in precipitation at Norman, Oklahoma, 1996-2008

    USGS Publications Warehouse

    Jaeschke, Jeanne B.; Scholl, Martha A.; Cozzarelli, Isabelle M.; Masoner, Jason R.; Christenson, Scott; Qi, Haiping

    2011-01-01

    Precipitation samples for measurement of stable-isotope ratios of hydrogen (delta2H) and oxygen (delta18O) were collected at the Norman Landfill Research Site in Norman, Oklahoma, from May 1996 to October 2008. Rainfall amounts also were measured at the site (U.S. Geological Survey gaging station 07229053) during the collection period. The delta2H of precipitation samples ranged from -121.9 to +8.3 per mil, and the delta18O of precipitation ranged from -16.96 to +0.50 per mil. The volume-weighted average values for delta2H and delta18O of precipitation over the 12-year measurement period were -31.13 per mil for delta2H and -5.57 per mil for delta18O. Average summer-season delta2H and delta18O values of precipitation usually were more positive (enriched in the heavier isotopes) than winter values.

  5. Influence of isotopic re-equilibration on speleothem and fluid inclusion isotope ratios after primary calcite precipitation

    NASA Astrophysics Data System (ADS)

    Kluge, Tobias; Haderlein, Astrid; Weißbach, Therese

    2016-04-01

    Oxygen isotope ratios in speleothems (notably stalagmites) have been used since decades to successfully infer paleotemperatures and deduce paleo-environmental information. In addition, recent technical developments allow to increasingly use fluid inclusions as an archive for drip-water and together with the surrounding calcite as paleothermometer. A basic requirement for isotope data interpretation is the complete knowledge of the fractionation between calcite and fluid. Most laboratory and in-situ cave experiments focus on calcite growth and the isotope fractionation between calcite and feed solution. Potential isotope exchange and re-equilibration processes after the initial deposition have mostly been neglected. However, experiments of Oelkers et al. (2015) showed that the isotope exchange between minerals and fluid can proceed rapidly (within days), even at chemical equilibrium. In hydrous Mg carbonates a similar process of continuous isotope exchange between carbonate and fluid was observed after the carbonate precipitation was completed (Mavromatis et al., 2015). These observations suggest that the isotope ratios of speleothem calcite may be affected by this continuous exchange, likely driving the isotope composition continuously towards equilibrium at the respective cave conditions. In addition, fluid inclusions are suspected to be sensitive to an isotope exchange with the surrounding carbonate highlighting the need to precisely understand and quantify this effect. We assessed the oxygen isotope exchange between calcite and solution at chemical equilibrium conditions with theoretical estimates and laboratory experiments over an intermediate time scale (hours-weeks). A large isotope gradient (~20 ‰)) between solution and calcite was prepared in the experiment to investigate the dynamics of this re-equilibration process. We used a theoretical model based on a Rayleigh fractionation approach and the direct comparison with the experiment to determine

  6. Uranium Isotope Fractionation during Adsorption, (Co)precipitation, and Biotic Reduction.

    PubMed

    Dang, Duc Huy; Novotnik, Breda; Wang, Wei; Georg, R Bastian; Evans, R Douglas

    2016-12-06

    Uranium contamination of surface environments is a problem associated with both U-ore extraction/processing and situations in which groundwater comes into contact with geological formations high in uranium. Apart from the environmental concerns about U contamination, its accumulation and isotope composition have been used in marine sediments as a paleoproxy of the Earth's oxygenation history. Understanding U isotope geochemistry is then essential either to develop sustainable remediation procedures as well as for use in paleotracer applications. We report on parameters controlling U immobilization and U isotope fractionation by adsorption onto Mn/Fe oxides, precipitation with phosphate, and biotic reduction. The light U isotope ((235)U) is preferentially adsorbed on Mn/Fe oxides in an oxic system. When adsorbed onto Mn/Fe oxides, dissolved organic carbon and carbonate are the most efficient ligands limiting U binding resulting in slight differences in U isotope composition (δ(238)U = 0.22 ± 0.06‰) compared to the DOC/DIC-free configuration (δ(238)U = 0.39 ± 0.04‰). Uranium precipitation with phosphate does not induce isotope fractionation. In contrast, during U biotic reduction, the heavy U isotope ((238)U) is accumulated in reduced species (δ(238)U up to -1‰). The different trends of U isotope fractionation in oxic and anoxic environments makes its isotope composition a useful tracer for both environmental and paleogeochemical applications.

  7. Stable Isotope Analysis of Precipitation Samples Obtained via Crowdsourcing Reveals the Spatiotemporal Evolution of Superstorm Sandy

    PubMed Central

    Good, Stephen P.; Mallia, Derek V.; Lin, John C.; Bowen, Gabriel J.

    2014-01-01

    Extra-tropical cyclones, such as 2012 Superstorm Sandy, pose a significant climatic threat to the northeastern United Sates, yet prediction of hydrologic and thermodynamic processes within such systems is complicated by their interaction with mid-latitude water patterns as they move poleward. Fortunately, the evolution of these systems is also recorded in the stable isotope ratios of storm-associated precipitation and water vapor, and isotopic analysis provides constraints on difficult-to-observe cyclone dynamics. During Superstorm Sandy, a unique crowdsourced approach enabled 685 precipitation samples to be obtained for oxygen and hydrogen isotopic analysis, constituting the largest isotopic sampling of a synoptic-scale system to date. Isotopically, these waters span an enormous range of values (21‰ for O, 160‰ for H) and exhibit strong spatiotemporal structure. Low isotope ratios occurred predominantly in the west and south quadrants of the storm, indicating robust isotopic distillation that tracked the intensity of the storm's warm core. Elevated values of deuterium-excess (25‰) were found primarily in the New England region after Sandy made landfall. Isotope mass balance calculations and Lagrangian back-trajectory analysis suggest that these samples reflect the moistening of dry continental air entrained from a mid-latitude trough. These results demonstrate the power of rapid-response isotope monitoring to elucidate the structure and dynamics of water cycling within synoptic-scale systems and improve our understanding of storm evolution, hydroclimatological impacts, and paleo-storm proxies. PMID:24618882

  8. Stable isotope analysis of precipitation samples obtained via crowdsourcing reveals the spatiotemporal evolution of Superstorm Sandy.

    PubMed

    Good, Stephen P; Mallia, Derek V; Lin, John C; Bowen, Gabriel J

    2014-01-01

    Extra-tropical cyclones, such as 2012 Superstorm Sandy, pose a significant climatic threat to the northeastern United Sates, yet prediction of hydrologic and thermodynamic processes within such systems is complicated by their interaction with mid-latitude water patterns as they move poleward. Fortunately, the evolution of these systems is also recorded in the stable isotope ratios of storm-associated precipitation and water vapor, and isotopic analysis provides constraints on difficult-to-observe cyclone dynamics. During Superstorm Sandy, a unique crowdsourced approach enabled 685 precipitation samples to be obtained for oxygen and hydrogen isotopic analysis, constituting the largest isotopic sampling of a synoptic-scale system to date. Isotopically, these waters span an enormous range of values (> 21‰ for δ(18)O, > 160‰ for δ(2)H) and exhibit strong spatiotemporal structure. Low isotope ratios occurred predominantly in the west and south quadrants of the storm, indicating robust isotopic distillation that tracked the intensity of the storm's warm core. Elevated values of deuterium-excess (> 25‰) were found primarily in the New England region after Sandy made landfall. Isotope mass balance calculations and Lagrangian back-trajectory analysis suggest that these samples reflect the moistening of dry continental air entrained from a mid-latitude trough. These results demonstrate the power of rapid-response isotope monitoring to elucidate the structure and dynamics of water cycling within synoptic-scale systems and improve our understanding of storm evolution, hydroclimatological impacts, and paleo-storm proxies.

  9. Technical Note: A simple method for vaterite precipitation in isotopic equilibrium: implications for bulk and clumped isotope analysis

    NASA Astrophysics Data System (ADS)

    Kluge, T.; John, C. M.

    2014-12-01

    Calcium carbonate (CaCO3) plays an important role in the natural environment as a major constituent of the skeleton and supporting structure of marine life and has high economic importance as additive in food, chemicals and medical products. Pure CaCO3 occurs in the three different polymorphs calcite, aragonite and vaterite, whereof calcite is the most abundant and best characterized mineral. In contrast, little is known about the rare polymorph vaterite, in particular with regard to the oxygen isotope fractionation between H2O and the mineral. Synthetic precipitation of vaterite in the laboratory typically involves rapid processes and isotopic non-equilibrium, which excludes isotope studies focused on characterization of vaterite at equilibrium conditions. Here, we used a new experimental approach that enables vaterite mineral formation from an isotopically equilibrated solution. The solution consists of a ~ 0.007 mol L-1 CaCO3 solution that is saturated with NaCl at room temperature (up to 6.5 mol L-1). Vaterite precipitated as single phase or major phase (≥ 94%) in experiments performed between 23 and 91 °C. Only at 80 °C was vaterite a minor phase with a relative abundance of 27%. The high mineral yield of up to 235 mg relative to a total dissolved CaCO3 amount of 370 mg enables an investigation of the oxygen isotope fractionation between mineral and water, and the determination of clumped isotope values in vaterite.

  10. Plant leaf wax biomarkers capture gradients in hydrogen isotopes of precipitation from the Andes and Amazon

    NASA Astrophysics Data System (ADS)

    Feakins, Sarah J.; Bentley, Lisa Patrick; Salinas, Norma; Shenkin, Alexander; Blonder, Benjamin; Goldsmith, Gregory R.; Ponton, Camilo; Arvin, Lindsay J.; Wu, Mong Sin; Peters, Tom; West, A. Joshua; Martin, Roberta E.; Enquist, Brian J.; Asner, Gregory P.; Malhi, Yadvinder

    2016-06-01

    Plant leaf waxes have been found to record the hydrogen isotopic composition of precipitation and are thus used to reconstruct past climate. To assess how faithfully they record hydrological signals, we characterize leaf wax hydrogen isotopic compositions in forest canopy trees across a highly biodiverse, 3 km elevation range on the eastern flank of the Andes. We sampled the dominant tree species and assessed their relative abundance in the tree community. For each tree we collected xylem and leaf samples for analysis of plant water and plant leaf wax hydrogen isotopic compositions. In total, 176 individuals were sampled across 32 species and 5 forest plots that span the gradient. We find both xylem water and leaf wax δD values of individuals correlate (R2 = 0.8 and R2 = 0.3 respectively) with the isotopic composition of precipitation (with an elevation gradient of -21‰ km-1). Minimal leaf water enrichment means that leaf waxes are straightforward recorders of the isotopic composition of precipitation in wet climates. For these tropical forests we find the average fractionation between source water and leaf wax for C29n-alkanes, -129 ± 2‰ (s.e.m., n = 136), to be indistinguishable from that of temperate moist forests. For C28n-alkanoic acids the average fractionation is -121 ± 3‰ (s.e.m., n = 102). Sampling guided by community assembly within forest plots shows that integrated plant leaf wax hydrogen isotopic compositions faithfully record the gradient of isotopes in precipitation with elevation (R2 = 0.97 for n-alkanes and 0.60 for n-alkanoic acids). This calibration study supports the use of leaf waxes as recorders of the isotopic composition of precipitation in lowland tropical rainforest, tropical montane cloud forests and their sedimentary archives.

  11. Isotope fractionation during precipitation of methamphetamine HCl and discrimination of seized forensic samples.

    PubMed

    David, Gabrielle E; Coxon, Anne; Frew, Russell D; Hayman, Alan R

    2010-07-15

    Methamphetamine is a widely abused illicit drug. Increasingly, studies have focused on stable isotope analysis by isotope ratio mass spectrometry (IRMS) to link samples of methamphetamine synthesized together or from the same source of precursor. For this reason, it is important to understand potential sources of isotope fractionation that could cause variability in forensic data sets. In this study, methamphetamine free base samples were synthesized from (-)-ephedrine HCl using the HI/red phosphorus synthetic route and then precipitated as HCl salts by bubbling with HCl gas. The entire sample did not precipitate when first bubbled with gas, and multiple precipitation steps were required. Fractions of precipitate were individually analyzed for delta(13)C, delta(15)N and delta(2)H by IRMS. Both delta(15)N and delta(2)H were found to become more negative, with the heavy isotopes depleted, in successive fractions of precipitate. Homogenizing the precipitate fractions together could eliminate this fractionation. However, in a clandestine situation this fractionation could lead to greater than expected delta(15)N and delta(2)H variability between illicit samples of methamphetamine HCl that have been synthesized from the same sample of ephedrine. This needs to be taken into account when interpreting forensic IRMS data. We also present an analysis of four separate seized case lots of methamphetamine HCl, taking into account the possible sources of fractionation and available intelligence information.

  12. Analysis of long-term stable isotopic composition in German precipitation

    NASA Astrophysics Data System (ADS)

    Stumpp, C.; Klaus, J.; Stichler, W.

    2014-09-01

    Stable water isotopes in precipitation (18O and 2H) have been frequently used as environmental tracers to understand processes and timescales in hydrology and climate research. Capturing changes of isotopic composition over time and investigating long-term processes requires long-term data set analysis. In Germany, we have one of the world's densest national networks for long-term isotopic analysis of precipitation covering up to 36 years of time series at 28 locations. These data were used to identify the average as well as the temporal evolution of isotopic composition in German precipitation and how it is related to meteorological and geographical parameters. We found that individual Local Meteoric Water Lines (LMWL) and the long-term averages of δ18O and δ2H depend on latitude and elevation. More variable isotopic compositions and more enriched averages were found at the coast compared to more stable compositions and depleted averages in the South, South-East and at higher elevations. This continentality effect was strongly influenced by seasonal isotope-temperature dependencies. Removing the seasonality and looking at the changes over time compared to long-term averages indicate similar patterns for temperatures and 18O at some locations. We concluded that temperature and isotopes are in equilibrium in inland air masses only. The trend in temperature evolution was consistent on the national level, and temperature increases were observed in almost all stations. In contrast, temporal patterns of 18O revealed different patterns and increases were only observed in 20 out of 28 locations. Therefore, changes in isotopic composition in precipitation are not only influenced by large scale processes (i.e. temperature) but also by local factors which need to be further investigated.

  13. Variation in stable isotope ratios of monthly rainfall in the Douala and Yaounde cities, Cameroon: local meteoric lines and relationship to regional precipitation cycle

    NASA Astrophysics Data System (ADS)

    Wirmvem, Mengnjo Jude; Ohba, Takeshi; Kamtchueng, Brice Tchakam; Taylor, Eldred Tunde; Fantong, Wilson Yetoh; Ako, Ako Andrew

    2017-09-01

    Hydrogen (D) and oxygen (18O) stable isotopes in precipitation are useful tools in groundwater recharge and climatological investigations. This study investigated the isotopes in rainfall during the 2013 and 2014 hydrological years in the Douala and Yaounde urban cities. The objectives were to generate local meteoric water lines (LMWLs), define the spatial-temporal variations of the isotopes in rainwater and their relationship to the regional precipitation cycle, and determine the factors controlling the isotopic variation. The LWMLs in Douala and Yaounde were δD = 7.92δ18O + 12.99 and δD = 8.35δ18O + 15.29, respectively. The slopes indicate isotopic equilibrium conditions during rain formation and negligible evaporation effect during rainfall. Precipitation showed similar wide ranges in δ18O values from -5.26 to -0.75 ‰ in Douala and -5.8 to +1.81 ‰ in Yaounde suggesting a common moisture source from the Atlantic Ocean. Enriched weighted mean δ18O (wδ18O) values during the low pre- and post-monsoon showers coincided with low convective activity across the entire region. Enriched isotopic signatures also marked the West African monsoon transition phase during each hydrological year. Abrupt wδ18O depletion after the transition coincided with the monsoon onset in the region. Peak periods of monsoonal rainfall, associated with high convective activities, were characterised by the most depleted wδ18O values. Controls on isotopic variations are the amount effect and moisture recycling. The stable isotope data provide a tool for groundwater recharge studies while the isotopic correlation with regional rainfall cycle demonstrate their use as markers of moisture circulation and detecting climatic changes in precipitation.

  14. Variation in stable isotope ratios of monthly rainfall in the Douala and Yaounde cities, Cameroon: local meteoric lines and relationship to regional precipitation cycle

    NASA Astrophysics Data System (ADS)

    Wirmvem, Mengnjo Jude; Ohba, Takeshi; Kamtchueng, Brice Tchakam; Taylor, Eldred Tunde; Fantong, Wilson Yetoh; Ako, Ako Andrew

    2016-04-01

    Hydrogen (D) and oxygen (18O) stable isotopes in precipitation are useful tools in groundwater recharge and climatological investigations. This study investigated the isotopes in rainfall during the 2013 and 2014 hydrological years in the Douala and Yaounde urban cities. The objectives were to generate local meteoric water lines (LMWLs), define the spatial-temporal variations of the isotopes in rainwater and their relationship to the regional precipitation cycle, and determine the factors controlling the isotopic variation. The LWMLs in Douala and Yaounde were δD = 7.92δ18O + 12.99 and δD = 8.35δ18O + 15.29, respectively. The slopes indicate isotopic equilibrium conditions during rain formation and negligible evaporation effect during rainfall. Precipitation showed similar wide ranges in δ18O values from -5.26 to -0.75 ‰ in Douala and -5.8 to +1.81 ‰ in Yaounde suggesting a common moisture source from the Atlantic Ocean. Enriched weighted mean δ18O (wδ18O) values during the low pre- and post-monsoon showers coincided with low convective activity across the entire region. Enriched isotopic signatures also marked the West African monsoon transition phase during each hydrological year. Abrupt wδ18O depletion after the transition coincided with the monsoon onset in the region. Peak periods of monsoonal rainfall, associated with high convective activities, were characterised by the most depleted wδ18O values. Controls on isotopic variations are the amount effect and moisture recycling. The stable isotope data provide a tool for groundwater recharge studies while the isotopic correlation with regional rainfall cycle demonstrate their use as markers of moisture circulation and detecting climatic changes in precipitation.

  15. Tropical-Depression Precipitation In Southwestern North America: An Isotope Record From Arizona, And Isotope Signatures In Baja California Groundwater

    NASA Astrophysics Data System (ADS)

    Eastoe, C. J.; Hess, G.; Mahieux, S.

    2011-12-01

    A 30-year data set of O and H isotopes in individual precipitation events in Tucson, Arizona, includes entries identified with rainfall associated with tropical depressions, which occasionally pass through southern Arizona. Tropical-depression rain events yielding > 7 mm have a δ18O range -9 to -16 per mil, compared to volume-weighted average summer rainfall with δ18O = -6 per mil, a set of isotope effects similar to those observed in south Texas. The isotope signature of tropical-depression rain is present in groundwater of central and southern Baja California (BC), where summer and fall rain make up at least 50% of annual precipitation. Tritium-bearing groundwater at Todos los Santos (southern BC) has a δ18O range of -8 to -11 per mil and d-parameters near 10. Altitude effects related to adjacent, 1800 m mountains do not explain the isotope data. Groundwater of similar isotope character is present near the Tres Virgenes geothermal field (central BC), but not at Santo Tomas (northern BC). Large deuterium excess (d > 15) is not observed in any of the data.

  16. Latitudinal change in precipitation and water vapor isotopes over Southern ocean

    NASA Astrophysics Data System (ADS)

    Rahul, P.

    2015-12-01

    The evaporation process over ocean is primary source of water vapor in the hydrological cycle. The Global Network of Isotopes in Precipitation (GNIP) dataset of rainwater and water vapor isotopes are predominantly based on continental observations, with very limited observation available from the oceanic area. Stable isotope ratios in precipitation provide valuable means to understand the process of evaporation and transport of water vapor. This is further extended in the study of past changes in climate from the isotopic composition of ice core. In this study we present latitudinal variability of water vapor and rainwater isotopic composition and compared it with factors like physical condition of sea surface water from near equator (1°S) to the polar front (56°S) during the summer time expedition of the year 2013. The water vapor and rainwater isotopes showed a sharp depletion in isotopes while progressively move southward from the tropical regions (i.e. >30°S), which follows the pattern recorded in the surface ocean water isotopic composition. From the tropics to the southern latitudes, the water vapor d18O varied between -11.8‰ to -14.7‰ while dD variation ranges between -77.7‰ to -122.2‰. Using the data we estimated the expected water vapor isotopic composition under kinetic as well as equilibrium process. Our observation suggests that the water vapor isotopic compositions are in equilibrium with the sea water in majority of cases. At one point of observation, where trajectory of air parcel originated from the continental region, we observed a large deviation from the existing trend of latitudinal variability. The deduced rainwater composition adopting equilibrium model showed a consistent pattern with observed values at the tropical region, while role of kinetic process become dominant on progressive shift towards the southern latitudes. We will draw comparison of our observation with other data available in the literature together with isotope

  17. Atmospheric controls on the precipitation isotopes over the Andaman Islands, Bay of Bengal

    PubMed Central

    Chakraborty, S.; Sinha, N.; Chattopadhyay, R.; Sengupta, S.; Mohan, P. M.; Datye, A.

    2016-01-01

    Isotopic analysis of precipitation over the Andaman Island, Bay of Bengal was carried out for the year 2012 and 2013 in order to study the atmospheric controls on rainwater isotopic variations. The oxygen and hydrogen isotopic compositions are typical of the tropical marine sites but show significant variations depending on the ocean-atmosphere conditions; maximum depletion was observed during the tropical cyclones. The isotopic composition of rainwater seems to be controlled by the dynamical nature of the moisture rather than the individual rain events. Precipitation isotopes undergo systematic depletions in response to the organized convection occurring over a large area and are modulated by the integrated effect of convective activities. Precipitation isotopes appear to be linked with the monsoon intraseasonal variability in addition to synoptic scale fluctuations. During the early to mid monsoon the amount effect arose primarily due to rain re-evaporation but in the later phase it was driven by moisture convergence rather than evaporation. Amount effect had distinct characteristics in these two years, which appeared to be modulated by the intraseasonal variability of monsoon. It is shown that the variable nature of amount effect limits our ability to reconstruct the past-monsoon rainfall variability on annual to sub-annual time scale. PMID:26806683

  18. Atmospheric controls on the precipitation isotopes over the Andaman Islands, Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.; Sinha, N.; Chattopadhyay, R.; Sengupta, S.; Mohan, P. M.; Datye, A.

    2016-01-01

    Isotopic analysis of precipitation over the Andaman Island, Bay of Bengal was carried out for the year 2012 and 2013 in order to study the atmospheric controls on rainwater isotopic variations. The oxygen and hydrogen isotopic compositions are typical of the tropical marine sites but show significant variations depending on the ocean-atmosphere conditions; maximum depletion was observed during the tropical cyclones. The isotopic composition of rainwater seems to be controlled by the dynamical nature of the moisture rather than the individual rain events. Precipitation isotopes undergo systematic depletions in response to the organized convection occurring over a large area and are modulated by the integrated effect of convective activities. Precipitation isotopes appear to be linked with the monsoon intraseasonal variability in addition to synoptic scale fluctuations. During the early to mid monsoon the amount effect arose primarily due to rain re-evaporation but in the later phase it was driven by moisture convergence rather than evaporation. Amount effect had distinct characteristics in these two years, which appeared to be modulated by the intraseasonal variability of monsoon. It is shown that the variable nature of amount effect limits our ability to reconstruct the past-monsoon rainfall variability on annual to sub-annual time scale.

  19. [Hydrogen and Oxygen Isotopic Compositions of Precipitation and Its Water Vapor Sources in Eastern Qaidam Basin].

    PubMed

    Zhu, Jian-jia; Chen, Hui; Gong, Guo-li

    2015-08-01

    Stable hydrogen and oxygen isotopes can be used as a tracer to analyze water vapor sources of atmospheric precipitation. We choose Golmud and Delingha as our study areas, Golmud locates in the south of Qaidam basin, and Delingha locates in the northeast. Based on the analysis of monthly change of hydrogen and oxygen isotopic compositions of precipitation during June to September of 2010, and the relationship between deltaD and delta18O in precipitation, we investigated the water vapor sources of precipitation in eastern Qaidam basin. The results show that: (1) meteoric water line between June to September in Golmud is: deltaD = 7.840 delta18O - 4.566 (R2 = 0.918, P < 0.001), and in Delingha is: deltaD = 7.833 delta18O + 8.606 (R2 = 0.986, P < 0.001). The slopes and intercepts of meteoric water line between June to September in both Golmud and Delingha are lower than the global average, and the intercept in Golmud is only -4.566, which indicates the extremely arid climate condition. (2) the delta18O content of precipitation is much higher in Golmud in early July, it shows the enrichment of some heavier isotopes. However, the delta18O content of precipitation becomes lower from late July to early September, especially for the late September. The 8180 content of precipitation in Delingha is higher in June to August than that in late September. (3) the water vapor sources of precipitation in Golmud and Delingha are different, Golmud area is the northern border of Qinghai-Tibet Plateau where the southwest monsoon can reach, and the southwest monsoon brings water vapors of precipitation, but the water vapors of precipitation in Delingha are mainly from local evaporation.

  20. Scale dependencies of hydrologic models to spatial variability of precipitation

    NASA Astrophysics Data System (ADS)

    Koren, V. I.; Finnerty, B. D.; Schaake, J. C.; Smith, M. B.; Seo, D.-J.; Duan, Q.-Y.

    1999-04-01

    This study is focused on analyses of scale dependency of lumped hydrological models with different formulations of the infiltration processes. Three lumped hydrological models of differing complexity were used in the study: the SAC-SMA model, the Oregon State University (OSU) model, and the simple water balance (SWB) model. High-resolution (4×4 km) rainfall estimates from the next generation weather radar (NEXRAD) Stage III in the Arkansas-Red river basin were used in the study. These gridded precipitation estimates are a multi-sensor product which combines the spatial resolution of the radar data with the ground truth estimates of the gage data. Results were generated from each model using different resolutions of spatial averaging of hourly rainfall. Although all selected models were scale dependent, the level of dependency varied significantly with different formulations of the rainfall-runoff partitioning mechanism. Infiltration-excess type models were the most sensitive. Saturation-excess type models were less scale dependent. Probabilistic averaging of the point processes reduces scale dependency, however, its effectiveness varies depending on the scale and the spatial structure of rainfall.

  1. Reconciling Empirical Carbonate Clumped Isotope Calibrations: A Comparison of Calcite Precipitation and Acid Digestion Methods

    NASA Astrophysics Data System (ADS)

    Kelson, J.; Huntington, K. W.; Schauer, A. J.; Saenger, C.; Lechler, A. R.

    2015-12-01

    An accurate empirical calibration is necessary to confidently apply the carbonate clumped isotope (Δ47) thermometer. Previous synthetic carbonate calibrations disagree in temperature sensitivity, with one group of calibrations displaying a shallow Δ47-temperature slope (e.g., Dennis & Schrag, GCA, 2010), and the other a steep slope (e.g., Zaarur et al., EPSL, 2013). These calibrations differ in both the method of mineral precipitation and the temperature of the phosphoric acid used to digest carbonates for analysis, making it difficult to isolate the cause of the discrepancy. Here, we precipitate synthetic carbonates at temperatures of 6-80ºC using 4 different precipitation methods, and analyze the samples using both 90 and 25°C acid digestion. Precipitation experiments varied the use of salts (NaHCO3 and CaCl2) vs. dissolved CaCO3 as a starting solution, the use of carbonic anhydrase to promote isotopic equilibrium among dissolved inorganic carbon species in solution, and the method by which CO2 degasses to force carbonate precipitation. Carbonates precipitated by using salts and allowing CO2 to passively degas produce a shallow calibration slope that we hypothesize to approach isotopic equilibrium. Precipitation methods that bubble CO2 into solution then degas that CO2 (either passively or actively by bubbling N2) produce carbonates with consistently lower Δ47 and higher δ18O values for a given growth temperature. We infer that these carbonates grew in disequilibrium during rapid CO2 degassing. Varying acid digestion temperature does not change the results; acid fractionation factor is not correlated with grain size, Δ47, or d47 values. No precipitation method produces a steep calibration slope. Our large sample set of >60 carbonates lend confidence to a shallow slope calibration, and inform interpretations of Δ47 and δ18O values of natural carbonates that grow under conditions of isotopic disequilibrium.

  2. Optimising predictor domains for spatially coherent precipitation downscaling

    NASA Astrophysics Data System (ADS)

    Radanovics, S.; Vidal, J.-P.; Sauquet, E.; Ben Daoud, A.; Bontron, G.

    2012-04-01

    Relationships between local precipitation (predictands) and large-scale circulation (predictors) are used for statistical downscaling purposes in various contexts, from medium-term forecasting to climate change impact studies. For hydrological purposes like flood forecasting, the downscaled precipitation spatial fields have furthermore to be coherent over possibly large basins. This thus first requires to know what predictor domain can be associated to the precipitation over each part of the studied basin. This study addresses this issue by identifying the optimum predictor domains over the whole of France, for a specific downscaling method based on a analogue approach and developed by Ben Daoud et al. (2011). The downscaling method used here is based on analogies on different variables: temperature, relative humidity, vertical velocity and geopotentials. The optimum predictor domain has been found to consist of the nearest grid cell for all variables except geopotentials (Ben Daoud et al., 2011). Moreover, geopotential domains have been found to be sensitive to the target location by Obled et al. (2002), and the present study thus focuses on optimizing the domains of this specific predictor over France. The predictor domains for geopotential at 500 hPa and 1000 hPa are optimised for 608 climatologically homogeneous zones in France using the ERA-40 reanalysis data for the large-scale predictors and local precipitation from the Safran near-surface atmospheric reanalysis (Vidal et al., 2010). The similarity of geopotential fields is measured by the Teweles and Wobus shape criterion. The predictive skill of different predictor domains for the different regions is tested with the Continuous Ranked Probability Score (CRPS) for the 25 best analogue days found with the statistical downscaling method. Rectangular predictor domains of different sizes, shapes and locations are tested, and the one that leads to the smallest CRPS for the zone in question is retained. The

  3. Spatial and temporal variability of the precipitation seasonality

    NASA Astrophysics Data System (ADS)

    Baciu, Madalina; Cheval, Sorin; Dumitrescu, Alexandru; Breza, Traian

    2014-05-01

    Climate change scenarios assume significant modifications in the precipitation characteristics over the South-Eastern Europe (SEE), raising a huge interest from the general public and stakeholders. In the recent period, the scientific community has produced many reports showing that the overall precipitation amounts are likely to decrease until the end of the 21st century with variations related to geography, seasons, and parameters. The distribution of the precipitation along the year is key information for water management in hydrologic and agricultural applications, which are very sensitive issues for the SEE countries. This study investigates the observed variability of the seasonality over the SEE (1961-2020), and the expected changes according to IPCC scenarios for the next decades (2021-2050). The analysis exploits the outputs of the Regional Climate Models (RCMs) RegCM3 (ICTP), Aladin (CNRM), and Promes (UCLM), at 25-km spatial resolution and seasonal focus, while ECA&D, and E-OBS datasets were used for featuring the actual climate. Markham (a), and Walsh & Lawler (b) seasonality indices (SI) were computed and employed for the whole area, while the trend analysis was conducted using the nonparametric Mann-Kendall statistics (c), and the Pettitt test (d) and Rodionov Regime Shift Index (e) tests were employed to identify the shifting points. The results pointed out strong differentiations between the different climates in the studied region (e.g. Mediterranean and Carpathian regions), and significant changes in certain spots. Correlated with the variability of the water resources, consumption and availability, the results can be extremely useful for the water management activities. This study is the result of activities developed within the CC-WARE Project (Mitigating Vulnerability of Water Resources under Climate Change), contract no. SEE/D/0143/2.1/X.

  4. Coupling meteorology, metal concentrations, and Pb isotopes for source attribution in archived precipitation samples.

    PubMed

    Graney, Joseph R; Landis, Matthew S

    2013-03-15

    A technique that couples lead (Pb) isotopes and multi-element concentrations with meteorological analysis was used to assess source contributions to precipitation samples at the Bondville, Illinois USA National Trends Network (NTN) site. Precipitation samples collected over a 16month period (July 1994-October 1995) at Bondville were parsed into six unique meteorological flow regimes using a minimum variance clustering technique on back trajectory endpoints. Pb isotope ratios and multi-element concentrations were measured using high resolution inductively coupled plasma-sector field mass spectrometry (ICP-SFMS) on the archived precipitation samples. Bondville is located in central Illinois, ~250km downwind from smelters in southeast Missouri. The Mississippi Valley Type ore deposits in Missouri provided a unique multi-element and Pb isotope fingerprint for smelter emissions which could be contrasted to industrial emissions from the Chicago and Indianapolis urban areas (~125km north and east, of Bondville respectively) and regional emissions from electric utility facilities. Differences in Pb isotopes and element concentrations in precipitation corresponded to flow regime. Industrial sources from urban areas, and thorogenic Pb from coal use, could be differentiated from smelter emissions from Missouri by coupling Pb isotopes with variations in element ratios and relative mass factors. Using a three endmember mixing model based on Pb isotope ratio differences, industrial processes in urban airsheds contributed 56±19%, smelters in southeast Missouri 26±13%, and coal combustion 18±7%, of the Pb in precipitation collected in Bondville in the mid-1990s. Copyright © 2012 Elsevier B.V. All rights reserved.

  5. Feedbacks Among Arctic Sea Ice, Evaporation, and Precipitation - An Isotopic Approach

    NASA Astrophysics Data System (ADS)

    Posmentier, E. S.; Faiia, A.; Everhart, K. K.; Whiteman, D.; Feng, X.

    2011-12-01

    Interactions among Arctic sea ice, evaporation, terrestrial snowfall, and sea level have long been understood as a linchpin of Pleistocene ice age dynamics, but how does this feedback cycle influence decadal scale climate dynamics? The paucity of reliable Arctic hydrologic data has made it difficult to answer this question directly. However, new isotopic tools allow its quantitative examination. As a preliminary experiment, the iiSPACS (Isotopic Investigation of Sea-ice and Precipitation in the Arctic Climate System) program collected precipitation from 106 storm events in Barrow and Atqasuk, AK, and determined the precipitation isotopic ratios of D/H (deuterium to hydrogen) and 18O/16O. Theoretical values of these isotopic ratios were calculated by using HYSPLIT back trajectories based on NCEP/NCAR reanalysis wind data to find both the low-latitude and Arctic source regions of cloud vapor in each storm, and Rayleigh fractionation of the heavy isotopes in vapor advected moist adiabatically along a forward trajectory from the source to the precipitation-producing clouds. Statistical analysis of the theoretical and empirical data demonstrate that (1) isotopic ratios correlate significantly with sea ice in the Arctic source region; (2) the imputed amount of precipitation in Barrow and Atqasuk is significantly affected by sea ice in the Arctic source region; and (3) theoretical assumptions lead to a positive bias of about 57 per mil in deuterium; i.e., an underestimate of isotopic depletion of the vapor relative to observations. Several inferences may be made from the results. First, it appears that a diminution of sea ice area does, indeed, lead to an increase in terrestrial Arctic precipitation, at least at the two sites studies. This implies a possible negative climate feedback, because warming that initiates a sea ice retreat would lead to more terrestrial snow and a higher albedo, especially around the time of the summer solstice, when albedo is highly leveraged

  6. Isotopic composition of precipitation in Northern Italy: Reverse effect of anomalous climatic events

    NASA Astrophysics Data System (ADS)

    Longinelli, A.; Anglesio, E.; Flora, O.; Iacumin, P.; Selmo, E.

    2006-10-01

    SummaryA few years ago the first comprehensive map of the isotopic composition of precipitation in Italy was published, based on the results obtained over several years at 77 different locations in Italy. The lack of financial support made it impossible to continue this study extended to the whole country. However, the collection of composite monthly samples continued at 12 locations in Northern Italy. The main purpose was to check the variability through time of the yearly mean isotopic values calculated for some of these stations according to previous data and to add a couple of stations in the western section of Alps, along the Italy-France border for which we had no data. We report here the data obtained for the years 2002-2004. This period is particularly interesting since, during 2003, most of Europe, and particularly Italy, experienced the hottest summer of the last century. In principle, this climatic event should have determined a marked enrichment in heavy isotopes in the annual weighted means for that year. On the contrary, all but one of the collection sites yielded yearly mean isotopic values that were considerably more negative than the mean values calculated for the previous years. This is essentially due to the marked decrease in the yearly amount of precipitation and particularly in that of spring and summer so that the mean weighted yearly isotopic values are heavily affected by the amount of precipitation and the isotopic values of the winter and autumn months. This shift was particularly marked at the collection sites located along the northern slope of the Apennines where a marked "shadow" effect related to westerly air masses moving over the Apennines exists. An important aspect of these data concerns the interpretation of isotopic values of palaeoprecipitation: in the case of palaeo-isotopic changes determined by environmental conditions similar to those reported here, a "normal" interpretation of the data may be misleading.

  7. ENSO variability reflected in precipitation oxygen isotopes across the Asian Summer Monsoon region

    NASA Astrophysics Data System (ADS)

    Cai, Zhongyin; Tian, Lide; Bowen, Gabriel J.

    2017-10-01

    Oxygen isotope signals (δ18O) from paleo-archives are important proxies for past Asian Summer Monsoon (ASM) climate reconstruction. However, causes of interannual variation in the δ18O values of modern precipitation across the ASM region remain in argument. We report interannual δ18O variation in southern Tibetan Plateau precipitation based on long-term observations at Lhasa. These data, together with precipitation δ18O records from five Global Network of Isotopes in Precipitation (GNIP) stations and two ice core δ18O records, were used to define a regional metric of ASM precipitation δ18O (ASMOI). Back-trajectory analyses for rainy season precipitation events indicate that moisture sources vary little between years with relatively high and low δ18O values, a result that is consistent for the south (Lhasa), southeast (Bangkok), and east ASM regions (Hong Kong). In contrast, δ18O values at these three locations are significantly correlated with convection in the estimated source regions and along transport paths. These results suggest that upstream convection, rather than moisture source change, causes interannual variation in ASM precipitation δ18O values. Contrasting values of the ASMOI in El Niño and La Niña years reveal a positive isotope-El Niño Southern Oscillation (ENSO) response (e.g., high values corresponding to warm phases), which we interpret as a response to changes in regional convection. We show that the isotope-ENSO response is amplified at high elevation sites and during La Niña years. These findings should improve interpretations of paleo-δ18O data as a proxy for past ASM variation and provide new opportunities to use data from this region to study paleo-ENSO activity.

  8. Arctic Vortex changes alter the sources and isotopic values of precipitation in northeastern US

    Treesearch

    Tamir Puntsag; Myron J. Mitchell; John L. Campbell; Eric S. Klein; Gene E. Likens; Jeffrey M. Welker

    2016-01-01

    Altered atmospheric circulation, reductions in Arctic sea ice, ocean warming, and changes in evaporation and transpiration are driving changes in the global hydrologic cycle. Precipitation isotopic (δ18O and δ2H) measurements can help provide a mechanistic understanding of hydrologic change at global and regional scales. To...

  9. Chemical and isotopic variations of precipitation in the Los Alamos Region, New Mexico

    SciTech Connect

    Adams, A.I.; Goff, F.; Counce, D.

    1995-02-01

    Precipitation collectors were installed at 14 locations on the Pajarito Plateau and surrounding areas to study variations in chemistry, stable isotopes and tritium for the years 1990 to 1993. The volume of precipitation was measured and samples were collected and analyzed every three to four months. All precipitation samples contain <2.50 mg/kg Cl and have pH values ranging from 5.4 to 6.7. The stable isotope ({delta}D/{delta}{sup 18}O) results record seasonal variations in precipitation as the weather patterns shift from sources in the Pacific Ocean to sources in the Gulf of Mexico. The stable isotope results also show isotopic variations due to elevation differences among the collection points. The tritium contents ({sup 3}H) in rain samples vary from 6.54 T.U. to 141 T.U. Contouring of high tritium values (e.g. >20 T.U.) from each collection period clearly shows that Laboratory activities release some tritium to the atmosphere. The effect of these releases are well below the limits set by the Environmental Protection Agency for drinking water (about 6200 T.U.). The magnitude of the releases is apparently greatest during the summer months. However, anomalous tritium values are detected as far north as Espahola, New Mexico for many collection periods. Tritium releases by the Laboratory are not constant; thus, the actual amount of tritium in each release has been diluted in the composite samples of our three to four month collection periods.

  10. Unusual Atmospheric Processes: Implications for the Unusual Isotope Effect in Precipitation

    NASA Astrophysics Data System (ADS)

    Hurst, S.; Krishnamurthy, R. V.

    2016-12-01

    Several samples associated in particular with thunderstorms collected from Kalamazoo, Michigan reveal oxygen and hydrogen isotope ratios that are not compatible with known thermodynamic fractionation or the so-called Raleigh Distillation Effect. Data gathered from April 2014 to February 2016 can be separated into two categories: (1) samples with expected isotopic values based on previous work, (2) samples with unusually high δ18O and δ2H values. Values as high as 42‰ and 25‰ for δ2H and δ18O respectively are obtained. Recent studies suggest that precipitation produced by deep convection can produce moderately enriched oxygen isotopic values, although no hydrogen values for those precipitations are available. Moreover, no values have been recorded that are as high as some of those presented here. The unusual isotope values cannot be attributed to air mass contributions. It is argued that changes in atmospheric chemistry, most likely induced by lightning associated with thunderstorms are responsible. This is likely since temperatures associated with lightning can reach 40000°K. Several studies have indicated that lightning can significantly impact atmospheric chemistry producing, among other species, ozone and NOx. Atmospheric ozone has enriched isotopic values and likely contributes to enriched Oxygen-18 seen in precipitation. An explanation for enrichment in hydrogen is somewhat elusive, but a likely candidate is ion molecular reactions produced by extremely high temperatures in the corona of lightning.

  11. Unusual fractionation of both odd and even mercury isotopes in precipitation from Peterborough, ON, Canada

    NASA Astrophysics Data System (ADS)

    Chen, JiuBin; Hintelmann, Holger; Feng, XinBin; Dimock, Brian

    2012-08-01

    Once released into the atmosphere, mercury (Hg) is subject to long-range transport and a series of physico-chemical reactions before reentering terrestrial ecosystems. Though impressive progress has been made in understanding all aspects of Hg behavior in the atmosphere, many processes involved in the transformation and deposition of atmospheric Hg remain unidentified and source attribution is still an enormous challenge. Here, we examine the isotopic composition of Hg in precipitation collected during 2010 in Peterborough, ON, Canada and combine data on seasonal variations of mass-dependent (MDF) and mass-independent (MIF) fractionation with meteorological back-trajectory calculations to identify the Hg sources and to decipher Hg atmospheric transformation reactions. All precipitation samples displayed significant MDF (δ202Hg between -0.02‰ and -1.48‰) and MIF of odd isotopes (Δ199Hg varying from -0.29‰ to 1.13‰). We also report for the first time a seasonal variation of MIF of even Hg isotopes (Δ200Hg) in wet precipitation. Our results may suggest that photoreduction in droplets or on the surface layer of snow crystals induces odd Hg isotope anomalies, while mass independent fractionation of 200Hg is probably triggered by photo-initiated oxidation occurring on aerosol or solid surfaces in the tropopause. The observed seasonal variation of even Hg isotope MIF (Δ200Hg decrease with ambient temperature) is possibly a powerful tool for meteorological research and may aid in monitoring related climate changes.

  12. Technical Note: A simple method for vaterite precipitation for isotopic studies: implications for bulk and clumped isotope analysis

    NASA Astrophysics Data System (ADS)

    Kluge, T.; John, C. M.

    2015-06-01

    Calcium carbonate (CaCO3) plays an important role in the natural environment as a major constituent of the skeleton and supporting structure of marine life and has high economic importance as an additive in food, chemicals and medical products. Anhydrous CaCO3 occurs in the three different polymorphs calcite, aragonite and vaterite, whereof calcite is the most abundant and best characterized mineral. In contrast, little is known about the rare polymorph vaterite, in particular with regard to the oxygen isotope fractionation between H2O and the mineral. Synthetic precipitation of vaterite in the laboratory typically involves rapid processes and isotopic non-equilibrium, which excludes isotope studies focused on the characterization of vaterite under equilibrium conditions. Here, we used a new experimental approach that enables vaterite mineral formation from an isotopically equilibrated solution. The solution consists of a ~0.007 mol L-1 CaCO3 solution that is saturated with NaCl at room temperature (up to 6.4 mol L-1). Vaterite precipitated as single phase or major phase (≥94%) in experiments performed between 23 and 91 °C. Only at 80 °C was vaterite a minor phase with a relative abundance of 27%. The high mineral yield per experiment of up to 235 mg relative to the initially dissolved CaCO3 amount of on average 360 mg enables an investigation of the oxygen isotope fractionation between the mineral and water, and the determination of clumped isotope values in vaterite.

  13. Validating the regional hydrogeological models with stable isotope data in precipitation

    NASA Astrophysics Data System (ADS)

    Kalvāns, Andis; Babre, Alise; Popovs, Konārds; Timuhins, Andrejs; Spalviņš, Aivars

    2016-04-01

    Stable isotopes 18O and 2H are a conservative tracer in the subsurface flow. The precipitation is the primary input in the groundwater systems, hens' there should be a positive regional correlation of the stable isotope values in the groundwater and precipitation. The local recharge peculiarities should modulate the precipitation isotope signal and introduce some noise but not eliminate the correlation completely. Modelled isotope values in the precipitation (Terzer et al. 2013) were compared to the actually observed values in the groundwater (Babre et al, in print) in the Baltic Artesian Basin, located at the South-East cost of the Baltic Sea. But positive and significant correlation was not found. Two regional hydrogeological models LAMO (Spalvins et al. 2015) and MOSYS (Virbulis et al. 2013) were used to trace the likely recharge area of the considered groundwater samples. A simple particle tracing of the LAMO produced a statistically significant, positive correlation between observed δ18O values in the relatively young groundwater (modelled residence time <7500 years) and precipitation at the location of the recharge. More complicated modelling system MOSYS with coarser resolution allowed to simulate the large scale downward depletion of the δ18O values in the groundwater. It is concluded that observed stable isotope values in the groundwater can be compared to the precipitation values in the recharge areas to validate the modelled regional flow patterns. This research is supported by Latvian National Research Programme EVIDENnT project "Groundwater and climate scenarios". References Babre, A., Kalv¯a ns, K., Popovs, K., Retiķe, I., D¯e liņa, A., Vaikmäe, R., Martma, T. (in print) New isotope data in groundwater from Latvia, central part of the Baltic Basin. Isotopes in Environmental & Health Studies Spalvins, A., Slangens j., L¯a ce I., Aleks¯a ns, O., Krauklis, K., 2015. Improvement of Hydrogeological Models: A Case Study. In International Review on

  14. Laboratory evaluation of Li isotopic fractionation in carbonates: inorganic precipitation experiments

    NASA Astrophysics Data System (ADS)

    You, C.; Wang, W.; Lin, B.; Wang, B.; Huang, K.; Lin, P.

    2008-12-01

    Laboratory experiments were conducted to precipitate calcite and aragonite micro-crystals separately under controlled temperature and growth-rate conditions. High purity aragonite and calcite were precipitated and were examined by XRD, Raman and SEM. It is evident that high precipitation rate and low temperature in favor of mixed-carbonates formation. The obtained carbonate precipitates, along with paired fluids and the mother solutions, were acid dissolved and analyzed for various trace elements and stable isotopes using high resolution ICPMS and multi-collector ICP-MS, respectively. The Li partition coefficient (DLi) and the Li isotopic fractionation factors ("ÑLi) were calculated at temperature between 5 and 40°C, where other stable isotopes (i.e., Li, B, Ca, and Sr) were also determined. The derived DLi varies slightly (1.3- 1.6E-3) in aragonite, in strong contrast to that of large variation in calcite, DLi =2.1-9.2E-2. The calculated "ÑLi at various temperatures keep rather constant and show a small positive gradient (0.03 permil/°C) in aragonite. These results agree with previous calcite precipitation and were applied to study δ7Li in coralline skeleton.

  15. Metallic elements and isotope of Pb in wet precipitation in urban area, South America

    NASA Astrophysics Data System (ADS)

    Migliavacca, Daniela Montanari; Teixeira, Elba Calesso; Gervasoni, Fernanda; Conceição, Rommulo Vieira; Raya Rodriguez, Maria Teresa

    2012-04-01

    The atmosphere of urban areas has been the subject of many studies to show the atmospheric pollution in large urban centers. By quantifying wet precipitation through the analysis of metallic elements (ICP/AES) and Pb isotopes, the wet precipitation of the Metropolitan Area of the Porto Alegre (MAPA), Brazil, was characterized. The samples were collected between July 2005 and December 2007. Zn, Fe and Mn showed the highest concentration in studied sites. Sapucaia do Sul showed the highest average for Zn, due to influence by the steel plant located near the sampling site. The contribution of anthropogenic emissions from vehicular activity and steel plants in wet precipitation and suspended particulate matter in the MAPA was identified by the isotopic signatures of 208Pb/207Pb and 206Pb/207Pb. Moreover the analyses of the metallic elements allowed also to identify the contribution of other anthropic sources, such as steel plants and oil refinery.

  16. Spatially Controlled Fe Isotope Variations at Torres del Paine

    NASA Astrophysics Data System (ADS)

    Gajos, N.; Lundstrom, C.

    2013-12-01

    Recent advances in mass-spectrometry have identified systematic trends of non-traditional stable isotope variation in igneous rocks with differentiation index. We present new Fe isotope data for the Torres del Paine igneous complex in southern Chile. The multi-composition pluton consists of a 1 km vertical exposure of homogenous granite overlying a contemporaneous and possibly cogenetic 0.5 km mafic gabbro suite. Whereas previous isotopic investigations do little to address variations across important magmatic contacts, this study focuses on a first-of-its-kind spatially dependent non-traditional stable isotope investigation of an igneous pluton. Samples were collected at Torres del Paine in spatially significant transects, focusing on major contacts between country rock, granite and mafic units. Results collected by bracketed double spike MC-ICP-MS (2s precision of ×0.03) show an increase in δ56Fe towards the high silica margins of the pluton with values as high as δ56Fe 0.36. Additionally, the data show a decrease in δ56Fe toward the mafic center of the pluton with δ56Fe values ranging from δ56Fe -0.05 to 0.18. Samples collected on the contact between the granite and mafic complex show intermediate values of δ56Fe= 0.18(×) 0.03. Country rock samples in contact with granite show an isotopically light signature of δ56Fe=0.04 (×) 0.03. Analysis of 50 samples in total show a trend of increasing δ56Fe with SiO2 content. The process responsible for Fe isotope variations remains debated but is suggested to reflect four mechanisms: (1) crustal assimilation, (2) fractional crystallization, (3) late stage fluid exsolution [1] and (4) thermal migration [3]. Preliminary results show that mechanisms #1 and #2 would produce isotopic signatures opposite of those seen at Torres del Paine and other plutonic rocks. Isotopically light Torres country rock samples reveal that assimilation of rocks would not produce the isotopically heavy granites seen at Torres. Based on

  17. Effects of nitrate and water on the oxygen isotopic analysis of barium sulfate precipitated from solution

    USGS Publications Warehouse

    Hannon, Janet E.; Bohlke, Johnkarl F.; Mroczkowski, Stanley J.

    2008-01-01

    BaSO4 precipitated from mixed salt solutions by common techniques for SO isotopic analysis may contain quantities of H2O and NOthat introduce errors in O isotope measurements. Experiments with synthetic solutions indicate that δ18O values of CO produced by decomposition of precipitated BaSO4 in a carbon reactor may be either too low or too high, depending on the relative concentrations of SO and NO and the δ18O values of the H2O, NO, and SO. Typical δ18O errors are of the order of 0.5 to 1‰ in many sample types, and can be larger in samples containing atmospheric NO, which can cause similar errors in δ17O and Δ17O. These errors can be reduced by (1) ion chromatographic separation of SO from NO, (2) increasing the salinity of the solutions before precipitating BaSO4 to minimize incorporation of H2O, (3) heating BaSO4 under vacuum to remove H2O, (4) preparing isotopic reference materials as aqueous samples to mimic the conditions of the samples, and (5) adjusting measured δ18O values based on amounts and isotopic compositions of coexisting H2O and NO. These procedures are demonstrated for SO isotopic reference materials, synthetic solutions with isotopically known reagents, atmospheric deposition from Shenandoah National Park, Virginia, USA, and sulfate salt deposits from the Atacama Desert, Chile, and Mojave Desert, California, USA. These results have implications for the calibration and use of O isotope data in studies of SOsources and reaction mechanisms.

  18. Quantification of the impact of moisture source regions on the oxygen isotope composition of precipitation over Eagle Cave, central Spain

    NASA Astrophysics Data System (ADS)

    Krklec, Kristina; Domínguez-Villar, David

    2014-06-01

    The 5-day reconstruction of air mass history for the days with precipitation at Eagle Cave (central Spain), together with the determination of moisture uptake locations along back trajectories, is used to identify the moisture sources of precipitation for this site from 2009 to 2011. During this 3-year period, around 30% of precipitation at Eagle Cave originated from the moisture recycled within the Iberian Peninsula (IP), with the Proximal Atlantic being also a main source region of moisture, whereas the Mediterranean Sea and the Distal Atlantic have large variability during the studied period and other source regions are minor precipitation contributors. The comparison of monthly oxygen isotope composition of precipitation at Eagle Cave with the monthly percentage of precipitation originated in source regions shows a significant negative correlation for the IP region. Thus, the moisture recycling process in the IP region explains 12% of the variability of the monthly oxygen isotope composition of precipitation (p-value < 0.1). However, when temperature, amount of precipitation and all source regions are considered, 74% of the variability of the monthly oxygen isotope composition of precipitation is explained (p-value < 0.05). Therefore, although for Eagle Cave amount of precipitation and temperature are main contributors of the precipitation oxygen isotope variability (r2 = 0.54; p-value < 0.001), the moisture uptake distribution among source regions is a substantial control and should be considered when interpreting oxygen isotope speleothem records from this cave. This

  19. Bias Adjustment of high spatial/temporal resolution Satellite Precipitation Estimation relying on Gauge-Based precipitation over China

    NASA Astrophysics Data System (ADS)

    Yu, J.; Pan, Y.; Shen, Y.

    2010-12-01

    Satellite precipitation data has been widely used in the forecasting and research of weather and climate because of its high spatial/temporal resolution, especially in the area of limited access to ground-based measurements. The distribution of gauge stations in China is very uniform with most gauge stations located in Eastern China and few gauge stations located in Western China. So the using of satellite precipitation data in China is very important. Although the satellite precipitation data has a good spatial construction, its estimation value is less accurate and has distinct systematic bias comparing to gauge-based one. The bias of satellite precipitation data should be adjusted before using it. In this paper, the CMORPH (Climate Prediction Center Morphing Technique) 30-min precipitation products is chosen to represent the large-scale precipitation of China and be adjusted based on hourly rain gauge analysis over China by interpolating from more than 10000 stations collected and quality controlled by the National Meteorological Information Center of the China Meteorological by using a probability density function (PDF) matching method (Wang and Xie, 2005). After bias-adjustment by PDF matching, we get a less systematic bias and high-resolution satellite precipitation product, which is hourly precipitation on a 0.1°latitude/longitude grid over China. Adjusted values are more close to the gauge observations, and the probability density function of corrected precipitation products is the same as that of the gauge-based precipitation. In Western China, the quantity value of corrected precipitation estimates is obviously increased comparing to the original estimate value. On the other hand, the spatial construction is still maintenance of satellite products.

  20. Spatial Ensemble Postprocessing of Precipitation Forecasts Using High Resolution Analyses

    NASA Astrophysics Data System (ADS)

    Lang, Moritz N.; Schicker, Irene; Kann, Alexander; Wang, Yong

    2017-04-01

    Ensemble prediction systems are designed to account for errors or uncertainties in the initial and boundary conditions, imperfect parameterizations, etc. However, due to sampling errors and underestimation of the model errors, these ensemble forecasts tend to be underdispersive, and to lack both reliability and sharpness. To overcome such limitations, statistical postprocessing methods are commonly applied to these forecasts. In this study, a full-distributional spatial post-processing method is applied to short-range precipitation forecasts over Austria using Standardized Anomaly Model Output Statistics (SAMOS). Following Stauffer et al. (2016), observation and forecast fields are transformed into standardized anomalies by subtracting a site-specific climatological mean and dividing by the climatological standard deviation. Due to the need of fitting only a single regression model for the whole domain, the SAMOS framework provides a computationally inexpensive method to create operationally calibrated probabilistic forecasts for any arbitrary location or for all grid points in the domain simultaneously. Taking advantage of the INCA system (Integrated Nowcasting through Comprehensive Analysis), high resolution analyses are used for the computation of the observed climatology and for model training. The INCA system operationally combines station measurements and remote sensing data into real-time objective analysis fields at 1 km-horizontal resolution and 1 h-temporal resolution. The precipitation forecast used in this study is obtained from a limited area model ensemble prediction system also operated by ZAMG. The so called ALADIN-LAEF provides, by applying a multi-physics approach, a 17-member forecast at a horizontal resolution of 10.9 km and a temporal resolution of 1 hour. The performed SAMOS approach statistically combines the in-house developed high resolution analysis and ensemble prediction system. The station-based validation of 6 hour precipitation sums

  1. Stable isotopes composition of precipitation fallen over Cluj-Napoca, Romania, between 2009-2012

    SciTech Connect

    Puscas, R.; Feurdean, V.; Simon, V.

    2013-11-13

    The paper presents the deuterium and oxygen 18 content from All precipitations events, which have occured over Cluj-Napoca, Romania from 2009 until 2012. Time series for δ{sup 2}H and δ{sup 18}O values point out both the seasonal variation that has increased amplitude reflecting the continental character of the local climate as well as dramatic variations of isotopic content of successive precipitation events, emphasizing the anomalous values. These fluctuations are the footprint of the variations and trends in climate events. Local Meteoric Water Line (LMWL), reflecting the δ{sup 2}H - δ{sup 18}O correlation, has the slop and the intercept slightly deviated from the GMWL, indicating that the dominant process affecting local precipitations are close to the equilibrium condition. LMWL has a slope smaller then that of the GMWL in the warm season due to lower humidity and a slope closest to the slop of GMWL in cold season with high humidity. The δ{sup 2}H and δ{sup 18}O values both for the precipitation events and monthly mean values are positively correlated with the temperature values with a very good correlation factor. The values of δ{sup 2}H and δ{sup 18}O are not correlated with amount of precipitation, the 'amount effect' of isotopic composition of precipitation is not observed for this site.

  2. Temporal and Spatial Analysis of Precipitation in Guizhou Based on TRMM 3B42 Satellite Data

    NASA Astrophysics Data System (ADS)

    Wu, Jianfeng; Zhang, Fengtai; Cao, Guangjie; Li, Wei; Zhao, Xuemei

    2017-08-01

    Precipitation is an important part of the earth’s climate system. This article makes full use of the advantages of remote sensing images. In this paper, the TRMM 3B42 satellite precipitation from 1998 to 2013 is selected as the data source and Guizhou Province as the research area. The temporal and spatial distribution characteristics of precipitation in Guizhou Province are studied by linear trend estimation, linear regression analysis and ArcGIS spatial analysis. The conclusion as below: Precipitation shows a decreasing trend from southeast to northwest in Guizhou Province. From the seasonal scale, Precipitation is mainly concentrated in summer and the least precipitation in winter. Over the past 16 years, precipitation in Guizhou Province has shown a fluctuating change. Summer precipitation trend is more obvious. And winter precipitation is not obvious.

  3. [Characteristics of Stable Isotopes in Precipitation and Their Moisture Sources in Mengzi Region, Southern Yunnan].

    PubMed

    Li, Guang; Zhang, Xin-ping; Xu, You-peng; Song, Song; Wang, Yue-feng; Ji, Xiao-min; Xiang, Jie; Yang, Jie

    2016-04-15

    The δD and δ¹⁸O values in precpitation have disciplinary variations, and they have close connections with meteorological parameters and moisture sources. Based on the continuously collected precipitation samples in Mengzi from Jan. 2009 to Dec. 2011, the reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Centre for Environmental Prediction/National Centre for Atmospheric Research (NCEP/NCAR), and the Hybrid Single-Particle Lagrangian Integrated Trajectory for 4.8 (HYSPLIT_4.8) model, we analyzed the variations of δD and δ¹⁸O in precipitation at synoptic scale in Mengzi, and the relations between δ¹⁸O in precipitation and air temperature, δ¹⁸O in precipitation and amount, δ¹⁸O in precipitation and wind speed, δ¹⁸O in precipitation and moisture sources. The results showed that the variations of δD and δ¹⁸O values in precipitation exhibited remarkable seasonal variability. The stable isotopic values in precipitation were higher during dry season than those during wet season. The relations between δ¹⁸O in precipitation and air temperature, δ¹⁸O in precipitation and amount indicated significant negative correlations. However, it exhibited significant positive correlation between precipitation δ¹⁸O and wind speed at different pressure levels (300 hPa, 500 hPa, 700 hPa, and 800 hPa), and this result indicated that the wind speed was an important influencing factor for the variations of precipitation δ¹⁸O. With the increasing rainfall levels, the intercept and slope of meteoric water line also increased, and this phenomenon suggested that there was a secondary evaporation effect under sub-cloud in stable isotopes of precipitation. The backward trajectory model showed that the main moisture sources during dry season came from the westerly and the inland. However, during wet season, the remote ocean vapor was the main moisture source in Mengzi, and the δ¹⁸O values in

  4. Surface kinetic model for isotopic and trace element fractionation during precipitation of calcite from aqueous solution

    SciTech Connect

    DePaolo, Donald J.

    2011-01-01

    A surface reaction kinetic model is developed for predicting Ca isotope fractionation and metal/Ca ratios of calcite as a function of rate of precipitation from aqueous solution. The model is based on the requirements for dynamic equilibrium; i.e. proximity to equilibrium conditions is determined by the ratio of the net precipitation rate (Rp) to the gross forward precipitation rate (Rf), for conditions where ionic transport to the growing crystal surface is not rate-limiting. The value of Rp has been experimentally measured under varying conditions, but the magnitude of Rf is not generally known, and may depend on several factors. It is posited that, for systems with no trace constituents that alter the surface chemistry, Rf can be estimated from the bulk far-from-equilibrium dissolution rate of calcite (Rb or kb), since at equilibrium Rf = Rb, and Rp = 0. Hence it can be inferred that Rf ≈ Rp + Rb. The dissolution rate of pure calcite is measureable and is known to be a function of temperature and pH. At given temperature and pH, equilibrium precipitation is approached when Rp (=Rf - Rb) « Rb. For precipitation rates high enough that Rp » Rb, both isotopic and trace element partitioning are controlled by the kinetics of ion attachment to the mineral surface, which tend to favor more rapid incorporation of the light isotopes of Ca and discriminate weakly between trace metals and Ca. With varying precipitation rate, a transition region between equilibrium and kinetic control occurs near Rp ≈ Rb for Ca isotopic fractionation. According to this model, Ca isotopic data can be used to estimate Rf for calcite precipitation. Mechanistic models for calcite precipitation indicate that the molecular exchange rate is not constant

  5. Surface kinetic model for isotopic and trace element fractionation during precipitation of calcite from aqueous solution

    SciTech Connect

    DePaolo, D.

    2010-10-15

    A surface reaction kinetic model is developed for predicting Ca isotope fractionation and metal/Ca ratios of calcite as a function of rate of precipitation from aqueous solution. The model is based on the requirements for dynamic equilibrium; i.e. proximity to equilibrium conditions is determined by the ratio of the net precipitation rate (R{sub p}) to the gross forward precipitation rate (R{sub f}), for conditions where ionic transport to the growing crystal surface is not rate-limiting. The value of R{sub p} has been experimentally measured under varying conditions, but the magnitude of R{sub f} is not generally known, and may depend on several factors. It is posited that, for systems with no trace constituents that alter the surface chemistry, R{sub f} can be estimated from the bulk far-from-equilibrium dissolution rate of calcite (R{sub b} or k{sub b}), since at equilibrium R{sub f} = R{sub b}, and R{sub p} = 0. Hence it can be inferred that R{sub f} {approx} R{sub p} + R{sub b}. The dissolution rate of pure calcite is measureable and is known to be a function of temperature and pH. At given temperature and pH, equilibrium precipitation is approached when R{sub p} (= R{sub f} - R{sub b}) << R{sub b}. For precipitation rates high enough that R{sub p} >> R{sub b}, both isotopic and trace element partitioning are controlled by the kinetics of ion attachment to the mineral surface, which tend to favor more rapid incorporation of the light isotopes of Ca and discriminate weakly between trace metals and Ca. With varying precipitation rate, a transition region between equilibrium and kinetic control occurs near R{sub p} {approx} R{sub b} for Ca isotopic fractionation. According to this model, Ca isotopic data can be used to estimate R{sub f} for calcite precipitation. Mechanistic models for calcite precipitation indicate that the molecular exchange rate is not constant at constant T and pH, but rather is dependent also on solution saturation state and hence R{sub p

  6. Stable isotope signatures of seasonal precipitation on the Pacific coast of central Panama.

    PubMed

    Kern, Zoltán; Harmon, Russell S; Fórizs, István

    2016-01-01

    As calculated from data archived in the IAEA-WMO Global Network of Isotopes in Precipitation programme, the amount-weighted local meteoric water line for the Pacific coast of central Panama is: δ(2)H = 7.63(±0.08) × δ(18)O + 6.51(±0.49). Amount-weighted mean isotopic values were regressed against the sea surface temperature (SST) fields of the adjacent tropical oceans. A negative correlation of precipitation isotope composition with Caribbean SSTs is observed only for the early wet season (May-June), whilst the mid-summer dry period is characterized by positive correlation with eastern Pacific SSTs, similar to the late wet season (October-November). The negative response of May-June rainfall isotopic composition to Caribbean SSTs is explained by a SST-mediated change in stratiform rain fraction from organized convective systems proximal to the Inter Tropical Convergence Zone (ITCZ). The positive correlation for the rest of the wet season, when the organized convective zone of ITCZ and its attached stratiform belt are distant from the Pacific coast of Panama, is interpreted as simple evaporative temperature effect on isotopic fractionation.

  7. Barium isotope fractionation during witherite (BaCO3) dissolution, precipitation and at equilibrium

    NASA Astrophysics Data System (ADS)

    Mavromatis, Vasileios; van Zuilen, Kirsten; Purgstaller, Bettina; Baldermann, Andre; Nägler, Thomas F.; Dietzel, Martin

    2016-10-01

    This study examines the behavior of Ba isotope fractionation between witherite and fluid during mineral dissolution, precipitation and at chemical equilibrium. Experiments were performed in batch reactors at 25 °C in 10-2 M NaCl solution where the pH was adjusted by continuous bubbling of a water saturated gas phase of CO2 or atmospheric air. During witherite dissolution no Ba isotope fractionation was observed between solid and fluid. In contrast, during witherite precipitation, caused by a pH increase, a preferential uptake of the lighter 134Ba isotopomer in the solid phase was observed. In this case, the isotope fractionation factor αwitherite-fluid is calculated to be 0.99993 ± 0.00004 (or Δ137/134Bawitherite-fluid ≈ -0.07 ± 0.04‰, 2 sd). The most interesting feature of this study, however, is that after the attainment of chemical equilibrium, the Ba isotope composition of the aqueous phase is progressively becoming lighter, indicating a continuous exchange of Ba2+ ions between witherite and fluid. Mass balance calculations indicate that the detachment of Ba from the solid is not only restricted to the outer surface layer of the solid, but affects several (∼7 unit cells) subsurface layers of the crystal. This observation comes in excellent agreement with the concept of a dynamic system at chemical equilibrium in a mineral-fluid system, denoting that the time required for the achievement of isotopic equilibrium in the witherite-fluid system is longer compared to that observed for chemical equilibrium. Overall, these results indicate that the isotopic composition of Ba bearing carbonates in natural environments may be altered due to changes in fluid composition without a net dissolution/precipitation to be observed.

  8. Stable isotope distribution in precipitation in Romania and its relevance for palaeoclimatic studies

    NASA Astrophysics Data System (ADS)

    Perşoiu, Aurel; Nagavciuc, Viorica; Bădăluţă, Carmen

    2014-05-01

    A surge of recent studies in Romania have targeted various aspects of palaeoclimate (based on stable isotopes in ice, speleothems, tree rings), mineral water origin, wine and other juices provenance. However, while much needed, these studies lack a stable isotope in precipitation background, with only two LMWL's being published so far. In this paper we discuss the links between the stable isotopic composition of precipitation (δ18O and δ2H), climate (air temperature, precipitation amount and large scale circulation) and their relevance for the palaeocllimatic interpretation of stable isotope values in cave ice, cryogenic calcite and tree rings from different sites in Romania. Most of the precipitation in Romania is delivered by the Westerlies, bringing moisture from the North Atlantic; however, their influence is greatly reduced in the eastern half of the country where local evaporative sources play an important role in the precipitation balance. The SW is dominated by water masses from the Mediterranean Sea, while the SE corner clearly draws most of the moisture from the Black Sea and strongly depleted North Atlantic vapor masses. In 2012, Romania experienced the worst draught in 60 years, possibly due to a northward shift of the jest stream associated to blocking conditions in summer, which led to a more northern penetration of the Mediterranean-derived air masses, as well increased precipitation of re-evaporated waters. We have further analyzed cave drip water (δ18O and δ2H), cryogenic cave calcite (δ18O and δ13C) and tree rings (δ18O and δ13C) from selected sites across NW Romania, where the water isotopes in precipitation showed the best (and easiest to understand, given the climatic conditions in 2012) correlation with climatic parameters. Our results that 1) δ18O and δ2H in cave ice are a good proxy for late summer through early winter air temperature; 2) δ13C in cryogenic cave calcite are possible indicators of soil humidity and 3) δ18O in pine

  9. Iron Isotope Fractionation in Microbial and Non-Biological Precipitates, and the Human Body

    NASA Astrophysics Data System (ADS)

    von Blanckenburg, F.; Boettcher, M. E.; Hofmann, B.; Walczyk, T.

    2001-12-01

    We have investigated biotic and abiotic stable iron isotope fractionation pathways in experiments, the low-T natural environment, and the human body. Fe samples were analysed using a Nu Plasma Multicollector ICP-MS. All measured samples plot on the theoretically predicted exponential fractionation line in the Delta57Fe versus Delta56Fe space, demonstrating absence of ArN or ArO interferences. An experimental calibration of Fe isotope fractionation during abiotic formation of iron (III) oxyhydroxide and iron(II) minerals from aqueous solution resulted in significant differences: (a) During fast precipitation of FeOOH during alkalization of a Fe(III)Cl3 solution at room temperature the solid is only slightly enriched by about 0.1permil in 57Fe compared to the solution. (b) Slow precipitation of akaganeite (beta-FeOOH) from aqueous Fe(III)Cl3 solution leads to a depletion of 57Fe by about -2.2permil in the solid phase without a significant influence of temperature. (c) Precipitation of FeOOH during oxidation of aqueous Fe(II) solutions by oxygen yields an enrichment of up to 4.8permil in 57Fe in the solid phase. (d) Iron(II) carbonate precipitation between 20 and 60C leads to an almost negligible depletion in 57Fe compared to aqueous ferrous ions. Interpretation: Large enrichment of the heavy isotope is observed where Fe is oxidised, whereas small to interme-diate depletions of heavy Fe isotopes occur upon forma-tion of Fe-minerals without change in redox state. Addi-tionally, kinetic effects, the speciation of the aqueous solution, or the effect of crystal structures may have to be considered. Biotic isotope fractionation by microorganisms was investigated at two field sites. In a Fe mine (Gonzen, Switzerland), Fe-precipitating microbes (Gallionella ferrugina and Leptohrix ochtraceae) have formed Fe(III)-oxyhydroxides that are ca. 0.6permil heavier in Delta57Fe than the Fe-rich parent solutions. At Cady Mts, California, filamentous fabrics of goethite, thought to

  10. Examining the impacts of precipitation isotope input (δ18Oppt) on distributed, tracer-aided hydrological modelling

    NASA Astrophysics Data System (ADS)

    Delavau, Carly J.; Stadnyk, Tricia; Holmes, Tegan

    2017-05-01

    Tracer-aided hydrological models are becoming increasingly popular tools as they assist with process understanding and source separation, which facilitates model calibration and diagnosis of model uncertainty (Tetzlaff et al., 2015; Klaus and McDonnell, 2013). Data availability in high-latitude regions, however, proves to be a major challenge associated with this type of application (Tetzlaff et al., 2015). Models require a time series of isotopes in precipitation (δ18Oppt) to drive simulations, and throughout much of the world - particularly in sparsely populated high-latitude regions - these data are not widely available. Here we investigate the impact that choice of precipitation isotope product (δ18Oppt) has on simulations of streamflow, δ18O in streamflow (δ18OSF), resulting hydrograph separations, and model parameters. In a high-latitude, data-sparse, seasonal basin (Fort Simpson, NWT, Canada), we assess three precipitation isotope products of different spatial and temporal resolutions (i.e. semi-annual static, seasonal KPN43, and daily bias-corrected REMOiso), and apply them to force the isoWATFLOOD tracer-aided hydrologic model. Total simulated streamflow is not significantly impacted by choice of δ18Oppt product; however, simulated isotopes in streamflow (δ18OSF) and the internal apportionment of water (driven by model parameterization) are impacted. The highest-resolution product (REMOiso) was distinct from the two lower-resolution products (KPN43 and static), but could not be verified as correct due to a lack of daily δ18Oppt observations. The resolution of δ18Oppt impacts model parameterization and seasonal hydrograph separations, producing notable differences among simulations following large snowmelt and rainfall events when event compositions differ significantly from δ18OSF. Capturing and preserving the spatial variability in δ18Oppt using distributed tracer-aided models is important because this variability impacts model parameterization

  11. [Responses of spatial distribution pattern of Artemisia ordosica population to the precipitation gradient on Ordos Plateau].

    PubMed

    Li, Qiu-shuang; Zhang, Chao; Wang, Fei; Lai, Li-ming; Zhang, Li; Li, Wen-ting; Bai, Hua; Zheng, Yuan-run

    2009-09-01

    Five sites along the precipitation gradient (336-249 mm x a(-1)) from east to west in Ordos Plateau were selected to study the spatial distribution pattern of Artemisia ordosica population and its responses to the precipitation gradient by the methods of variance mean ratio, aggregative index, and point pattern analysis. The reduction of precipitation affected the spatial distribution pattern of A. ordosica population significantly. With decreasing precipitation gradient, the spatial pattern of A. ordosica population changed from uniform to random in small scale, and from random to clumpy in large scale, suggesting that in the ecological restoration of Ordos Plateau, a rational arrangement of A. ordosica should be made.

  12. A Survey of Spatial and Seasonal Water Isotope Variability on the Juneau Icefield, Alaksa

    NASA Astrophysics Data System (ADS)

    Dennis, D.; Carter, A.; Clinger, A. E.; Eads, O. L.; Gotwals, S.; Gunderson, J.; Hollyday, A. E.; Klein, E. S.; Markle, B. R.; Timms, J. R.

    2015-12-01

    The depletion of stable oxygen-hydrogen isotopes (δ18O and δH) is well correlated with temperature change, which is driven by variation in topography, climate, and atmospheric circulation. This study presents a survey of the spatial and seasonal variability of isotopic signatures on the Juneau Icefield (JI), Alaska, USA which spans over 3,000 square-kilometers. To examine small scale variability in the previous year's accumulation, samples were taken at regular intervals from snow pits and a one square-kilometer surficial grid. Surface snow samples were collected across the icefield to evaluate large scale variability, ranging approximately 1,000 meters in elevation and 100 kilometers in distance. Individual precipitation events were also sampled to track percolation throughout the snowpack and temperature correlations. A survey of this extent has never been undertaken on the JI. Samples were analyzed in the field using a Los Gatos laser isotope analyzer. This survey helps us better understand isotope fractionation on temperate glaciers in coastal environments and provides preliminary information on the suitability of the JI for a future ice core drilling project.

  13. Sources of precipitation over South-Eastern Spain and groundwater recharge. An isotopic study

    NASA Astrophysics Data System (ADS)

    Cruz-San Julian, J.; Araguas, L.; Rozanski, K.; Benavente, J.; Cardenal, J.; Hidalgo, M. C.; Garcia-Lopez, S.; Martinez-Garrido, J. C.; Moral, F.; Olias, M.

    1992-07-01

    The deuterium and oxygen-18 compositions were monitored in several single rain events in south-eastern Spain from November 1989 till April 1990. Large variations in both δ D and δ18O, as well as in the value of deuterium excess (d-value) of up to + 27‰, were recorded during this time period. The observed variations are clearly related to different source regions of the vapour (Atlantic Ocean or Mediterranean Sea) as well as to different trajectories of precipitating air masses. Whereas the rains of Atlantic origin were characterized by d-values close to + 10‰, the Mediterranean-derived precipitation showed much higher values, of up to + 27‰. The apparent correlation between altitude of the sampling site and the d-value of the corresponding rain can be attributed to two mechanisms: the evaporative isotopic enrichment of rain drops below the clouds, especially at initial stages of the given precipitation event, and/or precipitation from air masses with different isotopic signature (d-value) of the water vapour. The range of the d-values observed in samples from local springs and wells (between + 10 and + 13‰) suggests that groundwater in the studied areas is recharged predominantly by the Atlantic-derived precipitation.

  14. Reconstructing Hydrologic Variability in Southwestern North America Using Speleothem Proxies and Precipitation Isotopes from California

    NASA Astrophysics Data System (ADS)

    McCabe-Glynn, Staryl

    Precipitation in southwestern North America has exhibited significant natural variability over the past few thousand years. This variability has been attributed to sea surface temperature regimes in the Pacific and Atlantic oceans, and to the attendant shifts in atmospheric circulation patterns. In particular, decadal variability in the North Pacific has influenced precipitation in this region during the twentieth century, but links to earlier droughts and pluvials are unclear. Here I assess these links using delta18 O measurements from a speleothem from southern California that spans AD 854-- 2007. I show that variations in the oxygen isotopes of the speleothem correlate to sea surface temperatures in the Kuroshio Extension region of the North Pacific, which affect the atmospheric trajectory and isotopic composition of moisture reaching the study site. Interpreting our speleothem data as a record of sea surface temperatures in the Kuroshio Extension, I find a strong 22-year periodicity, suggesting a persistent solar influence on North Pacific decadal variability. A comparison with tree-ring records of precipitation during the past millennium shows that some droughts occurred during periods of warmth in the Kuroshio Extension, similar to the instrumental record. However, other droughts did not and instead were likely influenced by other factors. The carbon isotope record indicates drier conditions are associated with higher delta13C values and may be a suitable proxy for reconstructing past drought variability. More research is needed to determine the controls on trace element concentrations. Finally, I find a significant increase in sea surface temperature variability over the past 150 years, which may reflect an influence of greenhouse gas concentrations on variability in the North Pacific. While drought is a common feature of climate in this region, most climate models also project extreme precipitation events to increase in frequency and severity because the

  15. Silicon isotope fractionation during silica precipitation from hot-spring waters

    NASA Astrophysics Data System (ADS)

    Geilert, Sonja; Vroon, Pieter; Keller, Nicole; Gudbrnadsson, Snorri; Stefánsson, Andri; van Bergen, Manfred

    2014-05-01

    Hot-spring systems in the Geysir geothermal area, Iceland, have been studied to explore silicon isotope fractionation in a natural setting where sinter deposits are actively formed over a temperature interval between 20° and 100° C. The SiO2(aq)concentrations in spring and stream waters range between 290 and 560ppm and stay relatively constant along downstream trajectories, irrespective of significant cooling gradients. The waters are predominantly oversaturated in amorphous silica at the temperatures measured in the field. Correlations between the saturation indices, temperature and amounts of evaporative water loss suggest that cooling and evaporation are the main causes of subaqueous silica precipitation. The δ30Si values of dissolved silica in spring water and outflowing streams average around +1o probably due to the small quantities of instantaneously precipitating silica relative to the dissolved amount. Siliceous sinters, in contrast, range between -0.1o to -4.0o consistent with a preferred incorporation of the light silicon isotope and with values for precipitated silica becoming more negative with downstream decreasing temperatures. Larger fractionation magnitudes are inversely correlated with the precipitation rate, which itself is dependent on temperature, saturation state and the extent of a system. The resulting magnitudes of solid-fluid isotopic fractionation generally decline from -3.5o at 10° C to -2.0o at 90° C. These values confirm a similar relationship between fractionation magnitude and temperature that we found in laboratory-controlled silica-precipitation experiments. However, a relatively constant offset of ca. -2.9o between field and experimental fractionation values indicates that temperature alone cannot be responsible for the observed shifts. We infer that precipitation kinetics are a prominent control of silicon isotope fractionation in aqueous environments, whereby the influence of the extent of the system on the precipitation

  16. Meteoric precipitation at Yucca Mountain, Nevada: Chemical and stable isotope analyses, 2006-09

    USGS Publications Warehouse

    Moscati, Richard J.; Scofield, Kevin M.

    2011-01-01

    Cumulatively, &delta18O values range from 3.0 to -20.4 per mil (%o) and &deltaD values range from 10 to -14%o. Winter-season precipitation commonly has isotopically lighter compositions. The cumulative &delta18O plotted against &deltaD shows that precipitation samples define a line with slope of 6.4, less than the 8 of the Global Meteoric Water Line. This difference in slope, typical of arid environments, is chiefly the result of evaporation of falling raindrops due to warmer air temperatures. ;

  17. A new spatial snow distribution in hydrological models parameterized from observed spatial variability of precipitation.

    NASA Astrophysics Data System (ADS)

    Skaugen, Thomas; Weltzien, Ingunn

    2016-04-01

    The traditional catchment hydrological model with its many free calibration parameters is not a well suited tool for prediction under conditions for which is has not been calibrated. Important tasks for hydrological modelling such as prediction in ungauged basins and assessing hydrological effects of climate change are hence not solved satisfactory. In order to reduce the number of calibration parameters in hydrological models we have introduced a new model which uses a dynamic gamma distribution as the spatial frequency distribution of snow water equivalent (SWE). The parameters are estimated from observed spatial variability of precipitation and the magnitude of accumulation and melting events and are hence not subject to calibration. The relationship between spatial mean and variance of precipitation is found to follow a pattern where decreasing temporal correlation with increasing accumulation or duration of the event leads to a levelling off or even a decrease of the spatial variance. The new model for snow distribution is implemented in the, already parameter parsimonious, DDD (Distance Distribution Dynamics) hydrological model and was tested for 71 Norwegian catchments. We compared the new snow distribution model with the current operational snow distribution model where a fixed, calibrated coefficient of variation parameterizes a log-normal model for snow distribution. Results show that the precision of runoff simulations is equal, but that the new snow distribution model better simulates snow covered area (SCA) when compared with MODIS satellite derived snow cover. In addition, SWE is simulated more realistically in that seasonal snow is melted out and the building up of "snow towers" is prevented and hence spurious trends in SWE.

  18. Precipitation water stable isotope measurements and analyses in Middle and Polar Ural

    NASA Astrophysics Data System (ADS)

    Stukova, Olga; Gribanov, Konstantin; Zakharov, Vyacheslav; Cattani, Olivier; Jouzel, Jean

    2015-11-01

    In this paper, we present results of precipitation (rain, snow) water stable isotope measurements, which were collected on two places. Measuring was made on laser spectroscopy analyzer PICARRO L2130-i equipped with liquid auto sampler. We describe method of sample collecting, preparing, measuring and continuing analysis of experimental data. Stored data include results of 177 samples measuring from Kourovka collected from November 2012 to March 2014 and 73 samples from Labytnangi collected from March 2013 to December 2013.

  19. The influence of topography on the isotopic composition of orographically enhanced precipitation in an idealized baroclinic wave: Implications for isotope-based paleoaltimetry

    NASA Astrophysics Data System (ADS)

    Wheeler, L.; Galewsky, J.

    2016-12-01

    Isotope-based paleoaltimetry is based on the idea that as surface elevation increases, the isotopic composition of rainwater decreases and is recorded in geologic deposits. One of the main assumptions used in isotope-based paleoaltimetry is that pure orographic precipitation is the primary mechanism generating precipitation and the driver of isotopic fractionation. In pure orographic precipitation an air mass traveling perpendicular to the range front is lifted along the windward side and as the water vapor condenses the heavier isotopes are preferentially rained out. There is essentially no precipitation as an air mass travels down the leeside, which would leave no record of elevation on the leeside of mountain ranges. Pure orographic precipitation is rare though, and more commonly precipitation is derived from the orographic enhancement of a pre-existing storm system. Using an idealized baroclinic wave simulation in the Weather Research and Forecasting model (WRF), which is representative of a typical wintertime storm that affects the western United States, we test how changes in elevation and topographic configuration affect the distribution of orographically enhanced precipitation and the resulting isotopic composition. We modified the WRF model to include simple isotope physics in the microphysics scheme and the addition of a smooth topographic ridge. Tracers for the heavy isotopologues of water are incorporated into a Perfect Precipitation Model (PPM) and modified within the full microphysics scheme. In the PPM, precipitation is generated when a grid cell exceeds saturation. No condensate is retained in the atmosphere and all excess water vapor is condensed and falls out as precipitation. The isotopic fractionation takes place upon condensation based on the temperature dependent equilibrium factors for 18O and D. Our preliminary results show that for a low ridge, unlike in pure orographic precipitation, there is leeside precipitation. We also find that there

  20. Stable isotopes reveal sources of precipitation in the Qinghai Lake Basin of the northeastern Tibetan Plateau.

    PubMed

    Cui, Bu-Li; Li, Xiao-Yan

    2015-09-15

    The use of isotopic tracers is an effective approach for characterizing the moisture sources of precipitation in cold and arid regions, especially in the Tibetan Plateau (TP), an area of sparse human habitation with few weather and hydrological stations. This study investigated stable isotope characteristics of precipitation in the Qinghai Lake Basin, analyzed moisture sources using data sets from NCEP-NCAR, and calculated vapor contributions from lake evaporation to the precipitation in the basin using a two-component mixing model. Results showed that the Local Meteoric Water Line (LMWL) was defined as δ(2)H=7.86 δ(18)O+15.01, with a slope of less than 8, indicating that some non-equilibrium evaporation processes occurred when the drops fell below the cloud base. Temperature effects controlled δ(18)O and δ(2)H in precipitation in the basin, with high values in summer season and low values in winter season. Moisture in the basin was derived predominantly from the Southeast Asian Monsoon (SEAM) from June to August and the Westerly Circulation (WC) from September through May. Meanwhile, the transition in atmospheric circulation took place in June and September. The SEAM strengthened gradually, while the WC weakened gradually in June, and inversely in September. However, the Southwest Asian Monsoon (SWAM) did not reach the Qinghai Lake Basin due to the barrier posed by Tanggula Mountain. High d-excess (>10 ‰) and significant altitude and lake effects of δ(18)O in precipitation suggested that the vapor evaporated from Qinghai Lake, strongly influenced annual precipitation, and affected the regional water cycle in the basin distinctly. The monthly contribution of lake evaporation to basin precipitation ranged from 3.03% to 37.93%, with an annual contribution of 23.42% or 90.54 mm, the majority of which occurred in the summer season. The findings demonstrate that the contribution of evaporation from lakes to atmospheric vapor is fundamental to water cycling on the

  1. Precipitation stable isotope analysis for exploring temporal characteristics of tropical cyclones: A case study in Hong Kong

    NASA Astrophysics Data System (ADS)

    Chun, K. P.; Klaus, J.

    2016-12-01

    Hurricanes (or typhoons) play an important role in tropical and subtropical synoptic climates. Although increasing global temperatures in the 20th and 21st centuries are proposed to be linked to changing characteristics of hurricanes, results from previous studies are contradictory and changing environmental conditions affecting hurricanes are somewhat poorly conceptualised. In this investigation, stable precipitation isotope data are used to explore how hurricane properties change with variations of monsoon and regional climate patterns (e.g. the El Niño-Southern Oscillations). As a case study, a new approach using precipitation isotopes to analyse Hong Kong tropical cyclone time series is proposed. First, the variance of precipitation stable isotopes is decomposed to understand the influence of monsoons, southern oscillations and other regional climate conditions on Hong Kong precipitation isotopic signatures. Then, using decomposed precipitation isotope results, a frequency analysis of tropical hurricanes is performed to identify climatic controls and quantify their effects. Results from this study are expected to be valuable because they will provide an example which illustrates how local isotope data can be linked to the regional climate patterns. A framework to investigate Asian tropical cyclone change using stable precipitation isotopes is also proposed.

  2. Impact of Tibetan Plateau uplift on Asian climate and stable oxygen isotopes in precipitation

    NASA Astrophysics Data System (ADS)

    Botsyun, Svetlana; Sepulchre, Pierre; Risi, Camille; Donnadieu, Yannick

    2016-04-01

    Surface elevation provides crucial information for understanding both geodynamic mechanisms of Earth's interior and influence of mountains growth on climate. Stable oxygen isotopes paleoaltimetry is considered to be a very efficient technic for reconstruction of the elevation history of mountains belts, including Tibetan Plateau and the Himalayas. This method relies on the difference between δ18O of paleo-precipitation reconstructed using the natural archives, and modern measured values for the point of interest. However, stable-isotope paleoaltimetry is potentially hampered by the fact that the presumed constancy of altitude-δ18O relationships through time might not be valid and climate changes affects δ18O in precipitation. We use the isotope-equipped atmospheric general circulation model LMDZ-iso for modeling Asia climate variations and associated δ18O in precipitation linked with Himalayas and Tibetan Plateau uplift. Experiments with reduced height over the Tibetan Plateau and the Himalayas have been designed. For the purpose of understanding where and how simulated complex climatic changes linked with the growth of mountains affect δ18O in precipitation we develop a theoretical expression for the precipitation composition. Our results show that modifying Tibetan Plateau height alters large-scale atmospheric dynamics including monsoon circulation and subsidence and associated climate variables, namely temperature, precipitation, relative humidity and cloud cover. In turn, δ18O signal decomposition results show that the isotopic signature of rainfall is very sensitive to climate changes related with the growth of the Himalayas and Tibetan Plateau, notably changes in relative humidity and precipitation amount. Topography appears to be the main controlling factor for only 40{%} of the sites where previous paleoelevation studies have been performed. Change of moisture sources linked with Asian topography uplift is shown to be not sufficient to yield a strong

  3. Fractionation of stable Sr isotopes during carbonate precipitation and surface sorption process

    NASA Astrophysics Data System (ADS)

    Liu, H.; You, C.; Huang, K.; Tu, Y.; Chung, C.

    2010-12-01

    Stable strontium (Sr) isotope has been used as a new tool for constraining the Sr budget in seawater. To further understand the controlling factors of Sr marine mass balance, we study Sr isotope fractionation of new δ87/86Sr* (measured 87Sr/86Sr without normalization) and δ88/86Sr in carbonate precipitation and Sr sorption experiments. For such purpose, a high-precision analytical technique was developed using MC-ICP-MS (Neptune, Thermo Scientific). NIST SRM 3169 Zr standard was doped into samples for mass bias correction, with implementation of combined the standard-sample bracketing method and the Zr internal normalization. In this manner, the 92Zr/90Zr in SRM 3169 was certified by 88Sr/86Sr in SRM 987, calculated off-line via exponential law. The long term external reproducibility for δ87/86Sr* and δ88/86Sr analyses is better than ±0.040‰ and ±0.018‰ (2σ), respectively. Carbonates obtained from the inorganic precipitation experiments display a small, but significant temperature dependent isotopic fractionation trend at 5-40 degrees C in both calcites and aragonites. Sr sorption experiments were performed to evaluate the associated Sr isotope fractionation mechanism.

  4. Simultaneous measurements of stable water isotopes in near-surface vapor and precipitation to constrain below-cloud processes

    NASA Astrophysics Data System (ADS)

    Graf, Pascal; Sodemann, Harald; Pfahl, Stephan; Schneebeli, Marc; Ventura, Jordi Figueras i.; Leuenberger, Andreas; Grazioli, Jacopo; Raupach, Tim; Berne, Alexis; Wernli, Heini

    2016-04-01

    Present-day observations of stable water isotopes (SWI) in precipitation on monthly time scales are abundant and the processes governing the variation of SWI on these time scales have been investigated by many studies. However, also on much shorter time scales of hours mesoscale meteorological processes lead to significant variations of SWIs, which are important to understand. There are only few studies investigating the variations of SWI on this short time scale, for which, e.g., frontal dynamics, convection and cloud microphysics play an essential role. In particular, the isotopic composition of both near-surface vapor and precipitation is significantly influenced by below-cloud processes that include precipitation evaporation and isotopic exchange between falling precipitation and surrounding vapor. In this study, simultaneous measurements of SWI in near-surface vapor and precipitation with high (sub-hourly) temporal resolution in combination with observational data from radars, disdrometers, radiosondes and standard meteorological instruments are used for a detailed analysis of the relative importance of below-cloud and in-cloud (i.e., precipitation formation) processes during the course of three rain events in Switzerland in spring 2014. Periods are identified when the isotopic composition of near-surface vapor and equilibrium vapor above liquid rain drops agree and when they differ due to either evaporation of precipitation or incomplete equilibration of precipitation with surrounding vapor. These findings are verified by the supporting observational data. In addition, calculations with a simple rain-shaft model fed with observational data are compared to the actual isotopic composition of precipitation. This combination of isotope measurements and model calculations allows us to test the sensitivity of the precipitation isotope signal to rain intensity, drop-size distribution and temperature and humidity profiles.

  5. Iron isotope fractionation during microbially stimulated Fe(II) oxidation and Fe(III) precipitation

    USGS Publications Warehouse

    Balci, N.; Bullen, T.D.; Witte-Lien, K.; Shanks, Wayne C.; Motelica, M.; Mandernack, K.W.

    2006-01-01

    Interpretation of the origins of iron-bearing minerals preserved in modern and ancient rocks based on measured iron isotope ratios depends on our ability to distinguish between biological and non-biological iron isotope fractionation processes. In this study, we compared 56Fe/54Fe ratios of coexisting aqueous iron (Fe(II)aq, Fe(III)aq) and iron oxyhydroxide precipitates (Fe(III)ppt) resulting from the oxidation of ferrous iron under experimental conditions at low pH (<3). Experiments were carried out using both pure cultures of Acidothiobacillus ferrooxidans and sterile controls to assess possible biological overprinting of non-biological fractionation, and both SO42- and Cl- salts as Fe(II) sources to determine possible ionic/speciation effects that may be associated with oxidation/precipitation reactions. In addition, a series of ferric iron precipitation experiments were performed at pH ranging from 1.9 to 3.5 to determine if different precipitation rates cause differences in the isotopic composition of the iron oxyhydroxides. During microbially stimulated Fe(II) oxidation in both the sulfate and chloride systems, 56Fe/54Fe ratios of residual Fe(II)aq sampled in a time series evolved along an apparent Rayleigh trend characterized by a fractionation factor ??Fe(III)aq-Fe(II)aq???1.0022. This fractionation factor was significantly less than that measured in our sterile control experiments (???1.0034) and that predicted for isotopic equilibrium between Fe(II)aq and Fe(III)aq (???1.0029), and thus might be interpreted to reflect a biological isotope effect. However, in our biological experiments the measured difference in 56Fe/54Fe ratios between Fe(III)aq, isolated as a solid by the addition of NaOH to the final solution at each time point under N2-atmosphere, and Fe(II)aq was in most cases and on average close to 2.9??? (??Fe(III)aq-Fe(II)aq ???1.0029), consistent with isotopic equilibrium between Fe(II)aq and Fe(III)aq. The ferric iron precipitation experiments

  6. Elucidating the climate and topographic controls on stable isotope composition of meteoric waters in Morocco, using station-based and spatially-interpolated data

    NASA Astrophysics Data System (ADS)

    Ait Brahim, Yassine; Bouchaou, Lhoussaine; Sifeddine, Abdelfettah; Khodri, Myriam; Reichert, Barbara; Cruz, Francisco W.

    2016-12-01

    Understanding the main controls on stable isotope variations in precipitation is fundamental for the interpretation of the hydrological cycle. However, spatio-temporal variations in δ18Op are poorly known in Morocco. Herein, we explore the relative influence of meteorological variables, spatial and orographic (altitudinal) effects, atmospheric circulation and moisture sources on precipitation stable isotopes in Morocco. Precipitation events and two-years-long monthly records from 17 rain-gauge stations in Morocco are investigated and compared in this study to global gridded records of monthly and annual stable isotopes in precipitation. We highlight that the main spatial controls on precipitation stable isotopes are the topography and the distance from marine source. The most depleted mean annual isotopes are located in the High Atlas Mountains (δ18Op = -9.56‰ and δ2Hp = -59.3‰), while the most enriched isotope ratios exist in southwestern Morocco (δ18Op = -2.35‰ and δ2Hp = -7.47‰). The well-constrained relationship between δ18Op and altitude describes a gradient of 0.11-0.18‰ per 100 m. The seasonal variation is expressed by a general enrichment that reaches -4.8‰ during the dry season, related to the recycled vapor contained within the summer precipitation. Notwithstanding the scarcity of temperature and precipitation measurements, the amount effect is observed in multiple stations during several rain events and precipitation seems to have more influence on δ18Op than temperature. Backward moisture trajectories indicate a distinct depletion in δ18Op in extreme events originating from the Atlantic Ocean. The presence of a rain shadow effect is also revealed on the lee side of High Atlas Mountains, southeastern Morocco.

  7. Changing characteristics and spatial differentiation of spring precipitation in Southwest China during 1961-2012

    NASA Astrophysics Data System (ADS)

    Liu, Hong-Lan; Zhang, Qiang; Zhang, Jun-Guo; Hu, Wen-Chao; Guo, Jun-Qin; Wang, Sheng

    2015-02-01

    In this study, we analyze spring precipitation from 92 meteorological stations spanning between 1961 and 2012 to understand temporal-spatial variability and change of spring precipitation over Southwest China. Various analysis methods are used for different purposes, including empirical orthogonal function (EOF) analysis and rotated EOF (REOF) for analyzing spatial structure change of precipitation anomaly, and the Mann-Kendall testing method to determine whether there were abrupt changes during the analyzed time span. We find that the first spatial mode of the precipitation has a domain uniform structure; the second is dominated by a spatial dipole; and the third contains five variability centers. The 2000s is the decade with the largest amount of precipitation while the 1990s is the decade with the smallest amount of precipitation. The year-to-year difference of that region is large: the amount of the largest precipitation year doubles that of the smallest precipitation year. We also find that spring precipitation in Southwest China experienced a few abrupt changes: a sudden increase at 1966, a sudden decrease at 1979, and a sudden increase at 1995. We speculate that the spring precipitation will increase gradually in the next two decades. Project supported by the National Basic Research Program of China (Grant No. 2013CB430200 (2013CB430206)) and the Sixth Program Ten Talented People of the Meteorological Bureau of Gansu Province, China.

  8. Carbon isotope signature of dissolved inorganic carbon (DIC) in precipitation and atmospheric CO2.

    PubMed

    Górka, Maciej; Sauer, Peter E; Lewicka-Szczebak, Dominika; Jędrysek, Mariusz-Orion

    2011-01-01

    This paper describes results of chemical and isotopic analysis of inorganic carbon species in the atmosphere and precipitation for the calendar year 2008 in Wrocław (SW Poland). Atmospheric air samples (collected weekly) and rainwater samples (collected after rain episodes) were analysed for CO2 and dissolved inorganic carbon (DIC) concentrations and for δ13C composition. The values obtained varied in the ranges: atmospheric CO2: 337-448 ppm; δ13CCO2 from -14.4 to -8.4‰; DIC in precipitation: 0.6-5.5 mg dm(-3); δ13CDIC from -22.2 to +0.2‰. No statistical correlation was observed between the concentration and δ13C value of atmospheric CO2 and DIC in precipitation. These observations contradict the commonly held assumption that atmospheric CO2 controls the DIC in precipitation. We infer that DIC is generated in ambient air temperatures, but from other sources than the measured atmospheric CO2. The calculated isotopic composition of a hypothetical CO2 source for DIC forming ranges from -31.4 to -11.0‰, showing significant seasonal variations accordingly to changing anthropogenic impact and atmospheric mixing processes.

  9. Outside the pH box: Boron isotopes in synthetic calcite precipitated under varying solution chemistry

    NASA Astrophysics Data System (ADS)

    Farmer, J. R.; Uchikawa, J.; Penman, D. E.; Hoenisch, B.; Zeebe, R. E.

    2015-12-01

    Boron isotopic measurements (δ11B) in marine carbonates are a powerful tool for reconstructing past ocean carbon chemistry and the carbon cycle. Boron systematics in marine carbonates are rooted in the equilibrium dissociation of dissolved boron in seawater, but existing evidence from biogenic carbonates (corals, planktic and benthic foraminifers) suggests somewhat variable controls on boron concentration and δ11B. Synthetic precipitation experiments provide an opportunity to study boron systematics without biological interference, and recent studies (e.g., Uchikawa et al., 2015, GCA v150, 171-191) suggest that boron incorporation (measured as B/Ca ratios) into synthetic carbonates varies both with the elemental composition of experimental seawater and precipitation rate. Here we extend the geochemical characterization of synthetic calcite by investigating the influences of changing solution chemistry (pH, [Ca2+], [DIC] and [B]) and precipitation rate on their boron isotopic composition. Our results will be evaluated in the context of carbonate precipitation rates, modes of boron incorporation, and changing seawater chemistry through geologic time.

  10. Spatial estimation of daily precipitation in regions with complex relief and scarce data using terrain orientation

    NASA Astrophysics Data System (ADS)

    Castro, Lina Mabel; Gironás, Jorge; Fernández, Bonifacio

    2014-09-01

    Precipitation is the most relevant variable in the hydrological cycle which drives continental hydrologic processes. Its spatial occurrence and behavior are complex and its daily estimation is hard in poorly gauged regions where the topography is highly irregular. Several interpolation methods are available for this purpose, but their performance is quite uncertain. This study develops a spatial interpolation method for daily precipitation that considers both spatial discontinuities and the influence of topography. The method first identifies the precipitation occurrence in each grid-cell as a function of measurements in surrounding rain gauges, and then uses daily elevation vs. precipitation linear regressions throughout the grid-cells where precipitation occurrence is identified. These regressions are classified according to the terrain orientation with respect to the prevailing wind direction. The method was evaluated using categorical statistics that quantify the skill to identify the precipitation occurrence/non-occurrence, and goodness-of-fit statistics to evaluate the error and efficiency. The methodology was compared against inverse distance weighted and simple regression methods, which were implemented considering both continuous and discontinuous precipitation fields. The new method better simulates the occurrence of precipitation, whereas traditional methods applied without considering the spatial discontinuity of precipitation tend to overestimate the frequency of the rainfall events, and thus the magnitude of precipitation at the basin scale. When spatial discontinuity is considered, traditional methods improve their performance and are comparable to the proposed method. Overall, the new method increases the number of days in which elevation vs. precipitation linear regression can be used, thus improving the spatial representation of precipitation in areas with complex relief.

  11. The Massachusetts Water Isotope Mapping Project: An Integrated Precipitation, Surface Water, and Ground Water IsoScape for Improved Understanding of Hydrologic Processes

    NASA Astrophysics Data System (ADS)

    Boutt, D. F.; Cole, A.

    2016-12-01

    The development of CRDS has revolutionized our ability to collect large spatially and temporally distributed datasets of water isotopes allowing un-paralleled insight into the hydrologic functioning of catchments through the lens of isotopic tracing of the water molecule. We present the results of an ongoing study of high spatial and temporal dataset across the state of Massachusetts, Northeast United States. Our current database consists of 1500 precipitation measurements across 15 stations, 2500 surface water measurements across 150 sites, and 2000 groundwater from 200 wells screened in overburden and bedrock wells. Isotopic composition of the region varies significantly as a function of topography and season. Because of the coastal orientation of the region, there is a large variability in the mean 18O-H2O composition of precipitation due to locally dominant precipitation sources. Deuterium excess of precipitation in the range of 10 - 14 ‰ are typical. Five years of surface water samples across the region show a strong seasonal trend ranging from -10 to -3 ‰ δ18O-H2O. Surface waters depict seasonal evaporative enrichment in the heavy isotopes and demonstrate a similar magnitude of deuterium excess compared to the precipitation. During the winters of 2014 and 2015 typical seasonal trends are interrupted by distinctly depleted stream waters of the order of -12 to -11 ‰ δ18O-H2O. These excursions are consistent with a source of water vapor to the region from more northerly (colder) regions. Mean stream water δ18O- H2O isotopic compositions show a strong relationship to upgradient drainage area. Groundwater compositions range from -12 to -5 ‰ δ18O-H2O across all the sites. A correlation between groundwater well elevation and δ18O-H2O is observed with higher elevation sites depleted in heavy isotopes with variations of 2-3 ‰ δ18O-H2O at any given elevation. Groundwater isotopic composition is distinct between overburden aquifer types (till, glacial

  12. Temporal and spatial variability in precipitation trends in the Southeast Tibetan Plateau during 1961-2012

    NASA Astrophysics Data System (ADS)

    Zhang, X.-L.; Wang, S.-J.; Zhang, J.-M.; Wang, G.; Tang, X.-Y.

    2015-02-01

    Using the monthly precipitation data at 14 stations from 1961 to 2012, the precipitation trends at the seasonal and annual scales are analyzed using the Mann-Kendall test in the Southeast Tibetan Plateau (STP). The area-averaged precipitation shows an increasing trend in the STP with strong temporal and spatial variations. The seasonal and annual precipitation increased, except in the summer; the annual precipitation increased by about one millimeter pre year over the last 52 years. The spring precipitation significantly increased at the 99% confidence level, while the mean summer precipitation insignificantly decreased at the 95% confidence level. The extreme precipitation, including the maxima and minima, also experienced overall increases. More than 78% of the stations exhibited increases in the annual precipitation (93% in spring). The precipitation variation with elevation was not obvious, but the variation with complex topography was obvious in the STP. The largest precipitation increases and decreases occurred in high-precipitation areas, while the increasing precipitation was dominant in or near the main area of the Tibetan Plateau (TP). The results of this study reveal the spatio-temporal variability in the precipitation trends in the STP for the first time. The results are beneficial for understanding the local climate characteristics in the STP and in the entire TP.

  13. Spatial patterns in the oxygen isotope composition of daily rainfall in the British Isles

    NASA Astrophysics Data System (ADS)

    Tyler, Jonathan J.; Jones, Matthew; Arrowsmith, Carol; Allott, Tim; Leng, Melanie J.

    2016-09-01

    Understanding the modern day relationship between climate and the oxygen isotopic composition of precipitation (δ18OP) is crucial for obtaining rigorous palaeoclimate reconstructions from a variety of archives. To date, the majority of empirical studies into the meteorological controls over δ18OP rely upon daily, event scale, or monthly time series from individual locations, resulting in uncertainties concerning the representativeness of statistical models and the mechanisms behind those relationships. Here, we take an alternative approach by analysing daily patterns in δ18OP from multiple stations across the British Isles ( n = 10-70 stations). We use these data to examine the spatial and seasonal heterogeneity of regression statistics between δ18OP and common predictors (temperature, precipitation amount and the North Atlantic Oscillation index; NAO). Temperature and NAO are poor predictors of daily δ18OP in the British Isles, exhibiting weak and/or inconsistent effects both spatially and between seasons. By contrast δ18OP and rainfall amount consistently correlate at most locations, and for all months analysed, with spatial and temporal variability in the regression coefficients. The maps also allow comparison with daily synoptic weather types, and suggest characteristic δ18OP patterns, particularly associated with Cylonic Lamb Weather Types. Mapping daily δ18OP across the British Isles therefore provides a more coherent picture of the patterns in δ18OP, which will ultimately lead to a better understanding of the climatic controls. These observations are another step forward towards developing a more detailed, mechanistic framework for interpreting stable isotopes in rainfall as a palaeoclimate and hydrological tracer.

  14. Modelling stable water isotopes in monsoon precipitation during the previous interglacial

    NASA Astrophysics Data System (ADS)

    Sjolte, Jesper; Hoffmann, Georg

    2014-02-01

    Changes in the tropical hydrological cycle have been recorded world wide in speleothem records dating back more than 200,000 years for some areas. Numerous empirical and modelling studies have demonstrated a strong link between the intensity of the northern hemisphere monsoon and the precessional insolation cycle (˜23 ka (thousand years)). Here we present simulations of the climate conditions of the previous interglacial, the Eemian (115-130 ka BP), using a general circulation model. We focus on changes in the tropical hydrological cycle and in the monsoon in particular. The model is equipped with a module for computing the water isotopic composition of all water reservoirs represented by the model. Our analysis of the simulated water isotope signals indicates that this key palaeo-proxy, i.e. the 18O or Deuterium signal in precipitation, is controlled by varying factors in different tropical areas: The main control on 18O for the Indian summer monsoon is the local precipitation amount, in accordance with the traditional interpretation, while the main control of 18O for East Asia is downwind depletion of 18O in vapour along the transport path. Over Africa the model simulates a strong gradient in the 18O anomalies during the Eemian climatic optimum, with depleted values in the east and relatively enriched 18O content in the west. This pattern is the result of a combination of the local "amount effect" and an anomalous zonal moisture transport. The influence of the SSTs anomalies on the placement of the Intertropical Convergence Zone (ITCZ) is found to be of major importance for the precipitation amount in the coastal regions of tropical South America. For the western part of South America a decrease in precipitation is seen for the Eemian climatic optimum, while an increase is seen for the eastern part. Our results underline the importance of reviewing the mechanisms causing isotopic changes in proxy records and further investigating the causes for past shifts in

  15. A river based stable isotope record of orographic precipitation: Taurus Mountains, south central Turkey

    NASA Astrophysics Data System (ADS)

    Schemmel, Fabian; Mulch, Andreas; Mikes, Tamás.; Schildgen, Taylor

    2010-05-01

    Reconstructing continental precipitation and vegetation patterns has become one of the most rapidly growing fields in terrestrial paleoclimate research. Furthermore, stable isotopes in precipitation within continental plateau regions represent an increasingly important tool for reconstructing the various effects of uplift related climate change within the world's largest plateau regions. With peak elevations of more than 3,000 m the Taurus Mountains represent the southern margin of the central Anatolian plateau and must have played a pivotal role in controlling the drainage and sedimentation patterns within the plateau interior. However, their surface uplift history remains largely elusive. We sampled a series of tributaries and rivers along the Ermenek valley that crosscuts the Taurus Mountains in Southern Turkey. The aim of this study is to quantify the modern effect of orographic rainout of the Taurus Mountains on the d18O and dD values of river and spring waters and to compare these values to the d18O and dD of recent precipitation gathered by the Global Network of Isotopes in Precipitation (GNIP). Further we try to study the trends of the recent d18O and dD isotopic composition of local rivers and precipitation in the area to create a set of isotopic data that is comparable to isotopic studies on paleosoils and can therefore be used in future paleoaltimetry and paleoclimate studies. We sampled 6 individual rivers during the fall season 2008 to capture mostly groundwater runoff in the south central Taurus Mountains. All sampled rivers belong to the same local drainage system which drains into the Mediterranean Sea. The total elevation difference within the sampling area exceeds 2,000 m and we were able to collect samples over almost 1,800 m of elevation. Our measurements show that both d18O and dD values follow the same basic trend. d18O and dD values decrease systematically with increasing elevation. The lapse rate of d18O is about -2.2 per mil/km, whereas the

  16. Novel Stable Isotope Methods for Assessing Changes in Seasonality of Precipitation from Sediments of Ombrotrophic Peatlands

    NASA Astrophysics Data System (ADS)

    Nichols, J. E.; Booth, R. K.; Jackson, S. T.; Pendall, E. G.; Walcott, M.; Bradley, R.; Pilcher, J.; Huang, Y.

    2007-12-01

    The seasonality of precipitation is a key but often elusive climate parameter in paleoclimate reconstructions. Sediments from ombrotrophic peatlands are excellent archives of past changes in precipitation/evaporation balance. Here we show that these peatland sediments can also be used to assess changes in the seasonality of precipitation. We have recently determined that distributions of Sphagnum and vascular plant biomarkers sensitively record changes in hydrologic balance (Nichols et al., 2006, Org. Geochem. 37, 1505-1513), but biomarker distributions alone do not offer detailed information for the changes in seasonal precipitation. In this study, we combine biomarker and compound-specific H and C isotope ratios to create a more comprehensive picture of the changing climate affecting these sensitive ombrotrophic systems. We present here two sets of downcore data from sites in Arctic Europe as well as Eastern North America. Basic paleohydrology is established using a ratio of Sphagnum to vascular plant biomarkers (C23 and C29 n-alkanes, respectively. We further describe paleohydrology using novel stable isotope proxies based on δD and δ13C measurements of Sphagnum and vascular plant biomarkers. Because Sphagnum has no vascular system and loses water directly by evaporation, Sphagnum biomarkers enriched in deuterium indicate an evaporative growing season (summer). Vascular plants use their root systems to take up water stored within the peatland, so deuterium-depleted vascular plant biomarkers should indicate increased winter recharge of the peatland. A methanotrophic symbiont living inside the Sphagnum's hyaline (water-holding) cells is more active when the Sphagnum is wet and therefore provides more 13C depleted (methane- derived) carbon dioxide for biomass production when the growing season is less evaporative. Hence, 13C depleted Sphagnum biomarkers indicate increased methanotrophy and therefore a wetter summer. We corroborate our stable isotope proxies by

  17. Precipitation Isotopes Reveal Intensified Indonesian Monsoon Circulation During the Dry Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Konecky, B. L.; Russell, J. M.; Vogel, H.; Bijaksana, S.; Huang, Y.

    2014-12-01

    The Indo-Pacific Warm Pool (IPWP) invigorates the oceanic-atmospheric circulation in the tropics, with far-reaching climate impacts that extend into the high latitudes. A growing number of deglacial proxy reconstructions from the region have revealed the importance of both high- and low-latitude climate processes to IPWP rainfall during the late Pleistocene. Many of these proxies reconstruct the oxygen and hydrogen isotopic composition of rainfall (δ18Oprecip, δDprecip), a powerful tool for understanding changes in climate. However, an increasing number of studies from the region have highlighted the tendency for δ18Oprecip and δDprecip to reflect regional and/or remote circulation processes rather than local rainfall amounts, complicating the reconstruction of IPWP hydroclimate. To better understand high- and low-latitude drivers of late Pleistocene hydroclimate in the IPWP, precipitation isotopic reconstructions must be constrained with both modern observations and independent proxies for rainfall amount. We present a reconstruction of δDprecip using leaf wax compounds preserved in the sediments of Lake Towuti, Sulawesi, from 60,000 years before present to today. We interpret our proxy record with the aid of a new precipitation isotopic dataset from our study site, with daily rainfall isotope measurements to constrain the processes controlling δDprecip. Our Lake Towuti δDwax record is strikingly similar to a speleothem δ18O record from southern Indonesia (Ayliffe et al., 2013) and shares features with other nearby records spanning the Last Glacial Maximum to present. Together, these records indicate that monsoon circulation was intensified in central and southern Indonesia during the glacial period. However, other independent rainfall proxies from Lake Towuti indicate that dry conditions accompanied the intensified monsoon. Regional-scale isotopic depletion during the dry glacial period may have arisen from dynamical and other fractionating processes that

  18. SPATIAL Short Courses Build Expertise and Community in Isotope Geochemistry

    NASA Astrophysics Data System (ADS)

    Riggs, E. M.; Bowen, G. J.

    2015-12-01

    The SPATIAL short course at the University of Utah is designed for graduate students and professionals in the earth and environmental sciences from around the globe. An integral part of the broader, NSF-funded Inter-university Training for Continental-scale Ecology (ITCE) project, the course is an intensive two-week field, classroom and laboratory experience with internationally-known researchers as instructors. The course focuses on stable isotope geochemistry coupled with spatial analysis techniques. Participants do not typically know each other or this research community well upon entering. One of the stated goals of the overall project is to build a community of practice around these techniques. This design is common in many professional fields, but is not often applied at the graduate level nor formally assessed in the earth sciences. Paired pre- and post-tests were administered before the start and after the close of the short courses over 3 years. The survey is a set of instruments adapted from social-cognitive psychology measuring changes in identity and community with other items to measure content knowledge outcomes. We see a subtle, consistent convergence of identities between large-scale isotope geochemistry and participants' research areas. Results also show that the course generates an increase in understanding about stable isotopes' use and application. The data show the SPATIAL course is very effective at bringing students together socially with each other and with faculty to create an environment that fosters community and scientific cooperation. Semi-structured pre-and post- interviews were conducted to understand the program elements that generated gains in learning and community. Participants were selected based on initial responses on the pre-survey to capture the range of initial conditions for the group. Qualitative analysis shows that the major factors for participants were 1) ready access to researchers in an informal setting during the

  19. Quantifying seasonal precipitation using high-resolution carbon isotope analyses in evergreen wood

    NASA Astrophysics Data System (ADS)

    Schubert, Brian A.; Jahren, A. Hope

    2011-11-01

    High-resolution natural abundance stable carbon isotope analyses across annual growth rings in evergreen trees reveal a cyclic increase and decrease in the measured carbon isotopic composition (δ 13C), but the causes of this pattern are poorly understood. We compiled new and published high-resolution δ 13C data from across annual growth rings of 33 modern evergreen trees from 10 genera and 15 globally distributed sites to quantify the parameters that affect the observed δ 13C pattern. Across a broad range of latitude, temperature, and precipitation regimes, we found that the average, measured seasonal change in δ 13C (Δδ 13C meas, ‰) within tree rings of evergreen species reflects changes in the carbon isotopic composition of atmospheric carbon dioxide (Δδ 13C CO2) and changes in seasonal precipitation (Δ P) according to the following equation: Δδ 13C meas = Δδ 13C CO2 - 0.82(Δ P) + 0.73; R2 = 0.96. Seasonal changes in temperature, pCO 2, and light levels were not found to significantly affect Δδ 13C meas. We propose that this relationship can be used to quantify seasonal patterns in paleoprecipitation from intra-ring profiles of δ 13C measured from non-permineralized, fossil wood.

  20. Changes in precipitation isotope-climate relationships from temporal grouping and aggregation of weekly-resolved USNIP data: impacts on paleoclimate and environmental applications

    NASA Astrophysics Data System (ADS)

    Akers, P. D.; Welker, J. M.

    2015-12-01

    Spatial variations in precipitation isotopes have been the focus of much recent research, but relatively less work has explored changes at various temporal scales. This is partly because most spatially-diverse and long-term isotope databases are offered at a monthly resolution, while daily or event-level records are spatially and temporally limited by cost and logistics. A subset of 25 United States Network for Isotopes in Precipitation (USNIP) sites with weekly-resolution in the east-central United States was analyzed for site-specific relationships between δ18O and δD (the local meteoric water line/LMWL), δ18O and surface temperature, and δ18O and precipitation amount. Weekly data were then aggregated into monthly and seasonal data to examine the effect of aggregation on correlation and slope values for each of the relationships. Generally, increasing aggregation improved correlations (>25% for some sites) due to a reduced effect of extreme values, but estimates on regression variable error increased (>100%) because of reduced sample sizes. Aggregation resulted in small, but significant drops (5-25%) in relationship slope values for some sites. Weekly data were also grouped by month and season to explore changes in relationships throughout the year. Significant subannual variability exists in slope values and correlations even for sites with very strong overall correlations. LMWL slopes are highest in winter and lowest in summer, while the δ18O-surface temperature relationship is strongest in spring. Despite these overall trends, a high level of month-to-month and season-to-season variability is the norm for these sites. Researchers blindly applying overall relationships drawn from monthly-resolved databases to paleoclimate or environmental research risk assuming these relationships apply at all temporal resolutions. When possible, researchers should match the temporal resolution used to calculate an isotopic relationship with the temporal resolution of

  1. Temporal and spatial variability of water isotopes in Ethiopian rainfall and its implication for moisture sources

    NASA Astrophysics Data System (ADS)

    Bedaso, Z. K.; Levin, N.; Zaitchik, B. F.; Shanko, D.

    2013-12-01

    The stable isotopes deuterium (δ2H) and oxygen (δ18O) in precipitation are used as conservative tracers of the hydrologic cycle and provide key information about past and present climates. The spatial and temporal variation of the isotopic composition of precipitation worldwide is monitored by the Global Network for Isotopes in Precipitation (GNIP). However the distribution of their sites is uneven, some regions are under sampled, and more importantly the data are limited to monthly collections. Ethiopia, where there is only a single long-term GNIP station, is one such region. The δ18O and δ2H values from the Addis Ababa GNIP station are higher than what would be expected for an inland location (>500 km from the nearest coastline) at high elevation (2360 m), but the reasons for these anomalously high values are poorly understood. Here, we present δ18O and δ2H values of precipitation from the first stage of a year-long campaign at four meteorological stations in the Northwestern and Southeastern Plateau regions of Ethiopia. Precipitation collections were made at daily, weekly and monthly intervals between August and December of 2012 (n=258). Our results from these stations indicate that there is a large range in daily rainfall values from 8.6‰ to 6.3‰ for δ18O, from -55.2‰ to 57.6‰ for δ2H, and from 1.0 to 27.6‰ for d excess. The daily δ18O and δ2H values averaged over a month at each station exhibit some monthly variability but the range in and average value of δ18O at the different stations are indistinguishable from one another. In contrast, d excess values show a distinct spatial pattern: daily average d-excess values (15.0×4.4 19.4×4.3‰) from precipitation collected at stations in the Northwestern Plateau are higher than those from precipitation collected at the Southeastern Plateau station, Jijiga, where daily d-excess values average 6.4 × 5.4 ‰. These differences in d-excess might be indicative of the role of recycled continental

  2. Spatially-based quality control for daily precipitation datasets

    NASA Astrophysics Data System (ADS)

    Serrano-Notivoli, Roberto; de Luis, Martín; Beguería, Santiago; Ángel Saz, Miguel

    2016-04-01

    There are many reasons why wrong data can appear in original precipitation datasets but their common characteristic is that all of them do not correspond to the natural variability of the climate variable. For this reason, is necessary a comprehensive analysis of the data of each station in each day, to be certain that the final dataset will be consistent and reliable. Most of quality control techniques applied over daily precipitation are based on the comparison of each observed value with the rest of values in same series or in reference series built from its nearest stations. These methods are inherited from monthly precipitation studies, but in daily scale the variability is bigger and the methods have to be different. A common character shared by all of these approaches is that they made reconstructions based on the best-correlated reference series, which could be a biased decision because, for example, a extreme precipitation occurred in one day in more than one station could be flagged as erroneous. We propose a method based on the specific conditions of the day and location to determine the reliability of each observation. This method keeps the local variance of the variable and the time-structure independence. To do that, individually for each daily value, we first compute the probability of precipitation occurrence through a multivariate logistic regression using the 10 nearest observations in a binomial mode (0=dry; 1=wet), this produces a binomial prediction (PB) between 0 and 1. Then, we compute a prediction of precipitation magnitude (PM) with the raw data of the same 10 nearest observations. Through these predictions we explore the original data in each day and location by five criteria: 1) Suspect data; 2) Suspect zero; 3) Suspect outlier; 4) Suspect wet and 5) Suspect dry. Tests over different datasets addressed that flagged data depend mainly on the number of available data and the homogeneous distribution of them.

  3. An isotope dilution-precipitation process for removing radioactive cesium from wastewater.

    PubMed

    Rogers, Harold; Bowers, John; Gates-Anderson, Dianne

    2012-12-01

    A novel isotope dilution-precipitation method has been developed to remove cesium-137 from radioactive wastewater. The process involves adding stable cesium chloride to wastewater in order to raise the total cesium concentration, which then allows both the stable and radioactive cesium ions to be precipitated together using sodium tetraphenylborate. This process was investigated utilizing laboratory solutions to determine stable cesium dose rates, mixing times, effects of pH, and filtration requirements. Once optimized, the process was then tested on synthetic wastewater and aqueous low-level waste. Experiments showed the reaction to be very quick and stable in the pH range tested, 2.5-11.5. The wastewater may need to be filtered using a 0.45-μm filter, though ferric sulfate has been shown to promote coagulation and settling, thereby eliminating the necessity for filtration. This investigation showed that this isotope dilution-precipitation process can remove Cs-37 levels below the U.S. Department of Energy's (DOE) Derived Concentration Standard (DCS) of 3.0 × 10(-6) μCi/mL using a single dosage, potentially allowing the wastewater to be discharged directly to sanitary sewers.

  4. Contribution of recycled moisture to precipitation in oases of arid central Asia: A stable isotope approach

    NASA Astrophysics Data System (ADS)

    Wang, Shengjie; Zhang, Mingjun; Che, Yanjun; Chen, Fenli; Qiang, Fang

    2016-04-01

    Terrestrial moisture contributed by surface evaporation and transpiration, also known as recycled moisture, plays an important role in hydrological processes especially across arid central Asia. The stable hydrogen and oxygen isotopes can be used for water budget analysis to calculate the contribution of recycled moisture to precipitation between two locations along the moisture flow. Based on a three-component isotopic mixing model, the moisture recycling in oasis stations of arid central Asia during summer months is assessed. At large oases of Urumqi, the proportional contribution of recycled moisture to local precipitation is approximately 16.2%, and the mean proportions of surface evaporation and transpiration are 5.9% ± 1.5% and 10.3% ± 2.2%, respectively. At small oases like Shihezi and Caijiahu the contribution of recycled moisture is less than 5%, and the proportion of surface evaporation is much less than that of transpiration. The vegetative cover in arid central Asia is generally sparse, but the evapotranspiration contribution to precipitation cannot be ignored at the widely distributed oases. The oasis effect shows great variability depending on locations and water availability for evapotranspiration.

  5. Paired Vapor-Precipitation Isotope Data from Manus, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Conroy, J. L.; Noone, D. C.; Cobb, K. M.; Moerman, J. W.; Konecky, B. L.

    2014-12-01

    We measured the stable isotopic composition of water vapor, precipitation and seawater over a period of 10 days at the highly instrumented Atmospheric Radiation Measurement (ARM) site located on Manus Island, Papua New Guinea. The island site, at 4 meters above sea level, sits close to the open ocean and is minimally impacted by terrestrial processes. Over the period of measurement, the mean δD value of near-surface water vapor (δDv) was -109.7±39.7‰, overlapping average tropospheric emissions satellite (TES) δDv values for the lower troposphere. We observed a 155‰ range in δDv values, coinciding with a transition through a Madden-Julian Oscillation event into a quiescent period. Low δDv values appear to reflect post-condensation exchange and the highest δDv values measured were in equilibrium with seawater δD. Of all surface meteorological variables, δDv was most strongly correlated with specific humidity, reflecting the importance of rainout and distillation in driving δDv values. During precipitation events, δDv dropped abruptly following maximum precipitation rates, likely due to mesoscale subsidence or rain evaporation. Intra-event δD values of precipitation (δDp) were most strongly correlated with δDv, and only weakly correlated with surface meteorological variables, highlighting the important role of δDv in controlling δDp values. We did not observe an amount effect through all precipitation events, as the lowest δDp values often lagged maximum precipitation rates. Precipitation deuterium excess values were significantly correlated with surface relative humidity and temperature, as well as cloud base height measurements, with higher deuterium excess values corresponding to higher cloud altitudes.

  6. Evaluating spatial patterns of a distributed hydrological model forced by polarimetric radar based quantitative precipitation estimation

    NASA Astrophysics Data System (ADS)

    He, X.; Sonnenborg, T. O.; Koch, J.; Zheng, C.; Jensen, K. H.

    2016-12-01

    Precipitation is the main driver to all hydrological processes in the terrestrial water cycle. Estimation of precipitation at catchment scale usually involves two aspects: the areal mean, which is the averaged amount across the entire catchment, and the spatial pattern, which refers to the internal distribution of precipitation within the catchment. Areal mean precipitation can be derived from rain gauge observations, whereas spatial patterns can be estimated by interpolating of point data or range scanning. Weather radar is a range scanning instrument which has the advantage of high spatial and temporal resolution, full automation and large spatial coverage. While estimating the areal mean is still more reliable with rain gauge measurements, the spatial patterns, on the other hand, is clearly delineated better by radar estimated precipitation. In the present study, we investigate the impact of diverging spatial pattern information of different precipitation estimates on distributed hydrological modeling. Precipitation products are used as forcing data and are retrieved from 1) interpolation of rain gauge data, 2) conventional radar data, single-pol data, and 3) polarimetric radar data, dual-pol data. Four years of continuous hourly precipitation are prepared and incorporated in a coupled MIKE SHE - SWET model for a catchment in western Denmark. One of the innovative contributions of the study is the application of Empirical Orthogonal Function analysis to evaluate spatial pattern similarity, which enables a true pattern comparison of the simulated hydrological variables. The results suggest that all models are able to generate comparable hydrological simulations in terms of stream discharge and groundwater elevation. Similarity of precipitation patterns decrease with increasing rainfall intensity. Analyzing scale dependency of simulated hydrological components to rainfall patterns reveals that significant variations are observed below 100 km2. Based on the above

  7. Quantifying spatial groundwater dependence in peatlands through a distributed isotope mass balance approach

    NASA Astrophysics Data System (ADS)

    Isokangas, Elina; Rossi, Pekka M.; Ronkanen, Anna-Kaisa; Marttila, Hannu; Rozanski, Kazimierz; Kløve, Bjørn

    2017-03-01

    The unique biodiversity and plant composition of peatlands rely on a mix of different water sources: precipitation, runoff, and groundwater (GW). Methods used to delineate areas of ecosystem groundwater dependence, such as vegetation mapping and solute tracer studies, are indirect and lack the potential to assess temporal changes in hydrology, information needed in GW management. This paper outlines a new methodology for mapping groundwater-dependent areas (GDAs) in peatlands using a 2H and 18O isotope mass balance method. The approach reconstructs the initial isotopic composition of the peat pore water in the uppermost peat layer before its modification by evaporation. It was assumed that pore water in this layer subject to evaporation is a two-component mixture consisting of GW and precipitation input from the month preceding the sampling period. A Bayesian Monte Carlo isotope mixing model was applied to calculate the proportions of GW and rainwater in the sampled pore water and to assess uncertainties. The approach revealed large spatial variability in the contribution of GW to the pore water present in the top layer of peatland, covering the range from approximately 0 to 100%. Results show that the current GW protection zones determined by Finnish legislation do not cover the GDAs in peatlands and highlight a need for better classification of groundwater-dependent ecosystems and conceptualization of aquifer-ecosystem interactions. Our approach offers an efficient tool for mapping GDAs and quantifying the contribution of GW to peatland pore water. However, more studies are needed to test the method for different peatland types.

  8. Oxygen Isotopes in Tree Rings: A 345 Year Record of Precipitation in Amazonia

    NASA Astrophysics Data System (ADS)

    Jenkins, H. S.; Baker, P. A.; Evans, M. N.

    2008-12-01

    The Amazon basin is one of the world's key centers of atmospheric convection and acts as an engine for global hydrologic circulation. Despite its importance, a paucity of high resolution climate data exists for this region, in large part due to a poor instrumental record. The oxygen isotopic measurement of meteoric water has been used extensively to reconstruct past temperatures derived from ice cores, corals, and tree rings but is only recently recognized as a precipitation proxy in the tropics. Here we present a continuous, highly resolved (intra-annual), 345 year oxygen isotopic record from the Madre de Dios department in Southeastern Peru. Using tropical hardwood species Dipteryx micrantha, we present oxygen (and carbon) isotopic data from digested tree ring cellulose. We also present some of the first intra-annual (early wood versus late wood) isotopic data on this old growth tropical species. We demonstrate the utility of Amazon tropical tree rings to accurately record rainfall. We also identify that this meteoric water was delivered to the region via the South American Low-level Jet (SALLJ), which develops over the Atlantic and is the major water source during the South American Summer Monsoon.

  9. Correlation of the seasonal isotopic amplitude of precipitation with annual evaporation and altitude in alpine regions.

    PubMed

    Jódar, J; Custodio, E; Liotta, M; Lambán, L J; Herrera, C; Martos-Rosillo, S; Sapriza, G; Rigo, T

    2016-04-15

    The time series of stable water isotope composition relative to IAEA-GNIP meteorological stations located in alpine zones are analyzed in order to study how the amplitude of the seasonal isotopic composition of precipitation (Aδ) varies along a vertical transect. A clear relationship between Aδ and local evaporation is obtained, with slopes of -0.87 ‰/100mm/yr and -7.3 ‰/100mm/yr for Aδ(18)O and Aδ(2)H, respectively. When all sampling points of the vertical transect receive the same moisture sources, then a linear relationship between Aδ and elevation is obtained, with vertical gradients of 0.16 ‰/100mm/yr and 1.46 ‰/100mm/yr forAδ(18)O and Aδ(2)H, respectively. Copyright © 2015. Published by Elsevier B.V.

  10. Summer Precipitation Predicts Spatial Distributions of Semiaquatic Mammals.

    PubMed

    Ahlers, Adam A; Cotner, Lisa A; Wolff, Patrick J; Mitchell, Mark A; Heske, Edward J; Schooley, Robert L

    2015-01-01

    Climate change is predicted to increase the frequency of droughts and intensity of seasonal precipitation in many regions. Semiaquatic mammals should be vulnerable to this increased variability in precipitation, especially in human-modified landscapes where dispersal to suitable habitat or temporary refugia may be limited. Using six years of presence-absence data (2007-2012) spanning years of record-breaking drought and flood conditions, we evaluated regional occupancy dynamics of American mink (Neovison vison) and muskrats (Ondatra zibethicus) in a highly altered agroecosystem in Illinois, USA. We used noninvasive sign surveys and a multiseason occupancy modeling approach to estimate annual occupancy rates for both species and related these rates to summer precipitation. We also tracked radiomarked individuals to assess mortality risk for both species when moving in terrestrial areas. Annual model-averaged estimates of occupancy for mink and muskrat were correlated positively to summer precipitation. Mink and muskrats were widespread during a year (2008) with above-average precipitation. However, estimates of site occupancy declined substantially for mink (0.56) and especially muskrats (0.09) during the severe drought of 2012. Mink are generalist predators that probably use terrestrial habitat during droughts. However, mink had substantially greater risk of mortality away from streams. In comparison, muskrats are more restricted to aquatic habitats and likely suffered high mortality during the drought. Our patterns are striking, but a more mechanistic understanding is needed of how semiaquatic species in human-modified ecosystems will respond ecologically in situ to extreme weather events predicted by climate-change models.

  11. Summer Precipitation Predicts Spatial Distributions of Semiaquatic Mammals

    PubMed Central

    Ahlers, Adam A.; Cotner, Lisa A.; Wolff, Patrick J.; Mitchell, Mark A.; Heske, Edward J.; Schooley, Robert L.

    2015-01-01

    Climate change is predicted to increase the frequency of droughts and intensity of seasonal precipitation in many regions. Semiaquatic mammals should be vulnerable to this increased variability in precipitation, especially in human-modified landscapes where dispersal to suitable habitat or temporary refugia may be limited. Using six years of presence-absence data (2007–2012) spanning years of record-breaking drought and flood conditions, we evaluated regional occupancy dynamics of American mink (Neovison vison) and muskrats (Ondatra zibethicus) in a highly altered agroecosystem in Illinois, USA. We used noninvasive sign surveys and a multiseason occupancy modeling approach to estimate annual occupancy rates for both species and related these rates to summer precipitation. We also tracked radiomarked individuals to assess mortality risk for both species when moving in terrestrial areas. Annual model-averaged estimates of occupancy for mink and muskrat were correlated positively to summer precipitation. Mink and muskrats were widespread during a year (2008) with above-average precipitation. However, estimates of site occupancy declined substantially for mink (0.56) and especially muskrats (0.09) during the severe drought of 2012. Mink are generalist predators that probably use terrestrial habitat during droughts. However, mink had substantially greater risk of mortality away from streams. In comparison, muskrats are more restricted to aquatic habitats and likely suffered high mortality during the drought. Our patterns are striking, but a more mechanistic understanding is needed of how semiaquatic species in human-modified ecosystems will respond ecologically in situ to extreme weather events predicted by climate-change models. PMID:26284916

  12. Isotopic (18O) characteristics of weekly precipitation collected across the USA: an initial analysis with application to water source studies

    NASA Astrophysics Data System (ADS)

    Welker, J. M.

    2000-06-01

    A portion of the precipitation samples collected and stored by the National Atmospheric Deposition Program (NADP) are shown to be useful for analysis of isotopes in precipitation. The potential problems with evaporation are small based on deuterium excess analyses and comparisons with the Global Meteroic Water Line. Presented here are the 18O values of precipitation collected from nine NADP sites during 1989, 1990 and 1991. The trends in the isotopic (18O) characteristics of recent precipitation are in agreement with findings from previous International Atomic Energy Agency (IAEA) sites in the USA. The findings are also in agreement with several major isotope-environment relationships, further supporting the use of these samples for a modern global data base on the isotopes in precipitation being developed by IAEA, called GNIP (Global Network for Isotopes in Precipitation) and for use by research groups in the hydrological modelling, palaeoclimate and ecological communities.As expected, the average 18O values of precipitation that is derived from the Gulf of Mexico (-3) and from the Pacific North-west are isotopically distinct (-7). In addition, using the NADP network, isotopic depletion in the 18O values of precipitation in the range of 8 was observed from coastal to inland locations either in the Pacific North-west or along the east side of the Rocky Mountains, from Texas to Eastern Montana. In central USA, especially at high elevation, there is a strong seasonal variation in the 18O values of precipitation, differing by almost 25 between January and August, whereas at coastal locations the seasonal variation in the 18O values of precipitation was minimal. Comparisons between the average 18precipitation from several NADP sites and those of the IAEA collected in the 1960s and 1970s are exceptionally comparable, differing in some cases by only 01, further substantiating the quality and utility of precipitation from this network. The

  13. Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico

    NASA Astrophysics Data System (ADS)

    Brienen, Roel J. W.; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

    2013-12-01

    Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation in δ18Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ18Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18O-depleted rain in the region and seem to have affected the δ18Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ18Otr of M. acantholoba can be used as a proxy for source water δ18O and that interannual variation in δ18Oprec is caused by a regional amount effect. This contrasts with δ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes

  14. Oxygen isotopes in tree rings record variation in precipitation δ(18)O and amount effects in the south of Mexico.

    PubMed

    Brienen, Roel J W; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

    2013-12-01

    [1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ(18)Otr). Interannual variation in δ(18)Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ(13)C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ(18)Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly (18)O-depleted rain in the region and seem to have affected the δ(18)Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ(18)Otr of M. acantholoba can be used as a proxy for source water δ(18)O and that interannual variation in δ(18)Oprec is caused by a regional amount effect. This contrasts with δ(18)O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in

  15. Oxygen isotopes in tree rings record variation in precipitation δ18O and amount effects in the south of Mexico

    PubMed Central

    Brienen, Roel J W; Hietz, Peter; Wanek, Wolfgang; Gloor, Manuel

    2013-01-01

    [1] Natural archives of oxygen isotopes in precipitation may be used to study changes in the hydrological cycle in the tropics, but their interpretation is not straightforward. We studied to which degree tree rings of Mimosa acantholoba from southern Mexico record variation in isotopic composition of precipitation and which climatic processes influence oxygen isotopes in tree rings (δ18Otr). Interannual variation in δ18Otr was highly synchronized between trees and closely related to isotopic composition of rain measured at San Salvador, 710 km to the southwest. Correlations with δ13C, growth, or local climate variables (temperature, cloud cover, vapor pressure deficit (VPD)) were relatively low, indicating weak plant physiological influences. Interannual variation in δ18Otr correlated negatively with local rainfall amount and intensity. Correlations with the amount of precipitation extended along a 1000 km long stretch of the Pacific Central American coast, probably as a result of organized storm systems uniformly affecting rainfall in the region and its isotope signal; episodic heavy precipitation events, of which some are related to cyclones, deposit strongly 18O-depleted rain in the region and seem to have affected the δ18Otr signal. Large-scale controls on the isotope signature include variation in sea surface temperatures of tropical north Atlantic and Pacific Ocean. In conclusion, we show that δ18Otr of M. acantholoba can be used as a proxy for source water δ18O and that interannual variation in δ18Oprec is caused by a regional amount effect. This contrasts with δ18O signatures at continental sites where cumulative rainout processes dominate and thus provide a proxy for precipitation integrated over a much larger scale. Our results confirm that processes influencing climate-isotope relations differ between sites located, e.g., in the western Amazon versus coastal Mexico, and that tree ring isotope records can help in disentangling the processes

  16. Spatial analysis of precipitation time series over the Upper Indus Basin

    NASA Astrophysics Data System (ADS)

    Latif, Yasir; Yaoming, Ma; Yaseen, Muhammad

    2016-12-01

    The upper Indus basin (UIB) holds one of the most substantial river systems in the world, contributing roughly half of the available surface water in Pakistan. This water provides necessary support for agriculture, domestic consumption, and hydropower generation; all critical for a stable economy in Pakistan. This study has identified trends, analyzed variability, and assessed changes in both annual and seasonal precipitation during four time series, identified herein as: (first) 1961-2013, (second) 1971-2013, (third) 1981-2013, and (fourth) 1991-2013, over the UIB. This study investigated spatial characteristics of the precipitation time series over 15 weather stations and provides strong evidence of annual precipitation by determining significant trends at 6 stations (Astore, Chilas, Dir, Drosh, Gupis, and Kakul) out of the 15 studied stations, revealing a significant negative trend during the fourth time series. Our study also showed significantly increased precipitation at Bunji, Chitral, and Skardu, whereas such trends at the rest of the stations appear insignificant. Moreover, our study found that seasonal precipitation decreased at some locations (at a high level of significance), as well as periods of scarce precipitation during all four seasons. The observed decreases in precipitation appear stronger and more significant in autumn; having 10 stations exhibiting decreasing precipitation during the fourth time series, with respect to time and space. Furthermore, the observed decreases in precipitation appear robust and more significant for regions at high elevation (>1300 m). This analysis concludes that decreasing precipitation dominated the UIB, both temporally and spatially including in the higher areas.

  17. Spatial and temporal variability of precipitation in Serbia for the period 1961-2010

    NASA Astrophysics Data System (ADS)

    Milovanović, Boško; Schuster, Phillip; Radovanović, Milan; Vakanjac, Vesna Ristić; Schneider, Christoph

    2017-04-01

    Monthly, seasonal and annual sums of precipitation in Serbia were analysed in this paper for the period 1961-2010. Latitude, longitude and altitude of 421 precipitation stations and terrain features in their close environment (slope and aspect of terrain within a radius of 10 km around the station) were used to develop a regression model on which spatial distribution of precipitation was calculated. The spatial distribution of annual, June (maximum values for almost all of the stations) and February (minimum values for almost all of the stations) precipitation is presented. Annual precipitation amounts ranged from 500 to 600 mm to over 1100 mm. June precipitation ranged from 60 to 140 mm and February precipitation from 30 to 100 mm. The validation results expressed as root mean square error (RMSE) for monthly sums ranged from 3.9 mm in October (7.5% of the average precipitation for this month) to 6.2 mm in April (10.4%). For seasonal sums, RMSE ranged from 10.4 mm during autumn (6.1% of the average precipitation for this season) to 20.5 mm during winter (13.4%). On the annual scale, RMSE was 68 mm (9.5% of the average amount of precipitation). We further analysed precipitation trends using Sen's estimation, while the Mann-Kendall test was used for testing the statistical significance of the trends. For most parts of Serbia, the mean annual precipitation trends fell between -5 and +5 and +5 and +15 mm/decade. June precipitation trends were mainly between -8 and +8 mm/decade. February precipitation trends generally ranged from -3 to +3 mm/decade.

  18. Circulation weather types and spatial variability of daily precipitation in the Iberian Peninsula %K circulation weather types, daily gridded precipitation, Iberian Peninsula, spatial variability, seasonal variability

    NASA Astrophysics Data System (ADS)

    Ramos, Alexandre; Cortesi, Nicola; Trigo, Ricardo

    2014-10-01

    The relationships between atmospheric circulation patterns and daily Iberian rainfall are here explored at high spatial resolution (0.2°) using the Jenkinson and Collison automated classification scheme with 26 Weather Types (WTs). The WTs were computed by means of the daily EMULATE Mean Sea Level Pressure dataset (EMSLP) while the high resolution precipitation database corresponds to the recent Iberia02 daily gridded precipitation dataset over the 1950-2003 period. Six monthly indexes relating the WTs and precipitation were analyzed: their Frequency, the Mean Precipitation, the Percentage Contribution, the Area of Influence, the Precipitation Intensity and Efficiency. Except for the Frequency of the WTs, all other indexes were evaluated studying their spatial distribution over the Iberian Peninsula, focusing on a WT and a month at time. A small number of WTs (7) was found to capture a high percentage (~70%) of monthly Iberian precipitation. The Westerly WT is the most influent one, followed by the Cyclonic, the Northwesterly and the Southwesterly WTs. Westerly flows, however, do not affect the Mediterranean fringe or the Cantabrian coast, which are dominated by the Easterly and Northerly WTs, respectively. Rainfall along the Mediterranean coastline and the Ebro basin depends on a variety of WTs, but their effects are confined to narrow areas and short temporal intervals, suggesting that local factors such as convective processes, orography and the proximity to a warm water body could play a major role in precipitation processes. We show that the use of daily gridded precipitation dataset holds the advantage of measuring the daily rainfall amount due to each WT directly instead to relying on the predicted values of the regression model as done in previous works.

  19. Modeling Stable Water Isotopes in Monsoon Precipitation during the Previous Interglacial

    NASA Astrophysics Data System (ADS)

    Sjolte, J.; Hoffmann, G. P.

    2012-12-01

    Changes in the hydrological cycle have been recorded throughout the tropical regions in speleothem records dating back more than 200.000 years for some areas. The intensity of the northern hemisphere monsoon has been found to be correlated to the precessional cycle (~23.000). Here we present a model study of the changes in the monsoon during the previous interglacial, the Eemian using a general circulation model with stable water isotopes embedded in the hydrological cycle. Analysis of a number of tropical areas show that the main control on the depletion of 18-O in precipitation varies regionally. The main control on 18-O for the Indian summer monsoon is the precipitation amount, in accordance with the traditional interpretation, while the main control of 18-O for East Asia is the path of moisture transport. Over Africa a strong gradient in the 18-O anomalies exists for the Eemian climatic optimum, with depleted values in the east and high 18-O content in the west. This pattern is the result of a combination of the "amount effect" and an anomalous zonal moisture transport. The influence of the sea surface temperature anomalies on the placement of the Intertropical Convergence Zone (ITCZ) is found to be of major importance for the precipitation amount in the coastal regions of tropical South America. For the western part of South America a decrease in precipitation is seen for the Eemian climatic optimum, while an increase is seen for the eastern part. Our results underline the importance of reviewing the mechanisms causing isotopic changes in proxy records and further investigating the causes for past shifts in the ITCZ.

  20. Tropical Sumatra Squalls drive stable isotope ratios of precipitation in Singapore

    NASA Astrophysics Data System (ADS)

    He, S.; Niezgoda, K.; Kurita, N.; Wang, X.; Rubin, C. M.; Goodkin, N.

    2016-12-01

    Sumatra Squalls, organized bands of thunderstorms, are the dominant mesoscale convective systems in the study area during the inter-monsoon and southwest monsoon season. Accompanied by gusty winds and heavy rains, the squalls can be very destructive, affecting Sumatra, the Malay Peninsula and Singapore. To understand how they affect precipitation and its stable isotopes, we continuously analyzed real-time δ-values of precipitation during the squalls in 2015 and also obtained δ-values of daily precipitation. We expect the study will improve our knowledge on cloud dynamics, water cycle during the squalls, and the drive of δ-value of precipitation in the region. We found that δ18O values of precipitation during the squalls mainly exhibit a "V" shape pattern or less commonly a "W" shape pattern. Change in the δ18O value during a single event is approximately 1 to 6‰, with the lowest values mostly observed in the stratiform zone. These observations can be largely explained by the mesoscale subsidence and rain re-evaporation in combination with other processes, such as the entrainment of ambient air. In some events, however, the minimum δ-value occurs in the convection core and coincides with 90% of the total event rainfall, implying a control of rain amount and the dominance of condensation mechanism during these events. Daily precipitation is characterized by periodic negative shifts in its δ18O value. Moreover, the shifts are associated with Sumatra Squalls. Compared to 2014, the frequency of the squalls and corresponding negative shifts in δ-values in 2015 is lower probably due to a weak monsoon. During the ENSO event in 2015, the region was generally drier as a result of reduced moisture convergence with the shift of convection in the western Pacific to the central and eastern Pacific. Therefore, Pacific warm/cold events likely affect the formation of the Sumatra Squalls in the region.

  1. Stable isotope record of Holocene precipitation changes from Lake Nuudsaku in southern Estonia

    NASA Astrophysics Data System (ADS)

    Fortney, Carolyn; Stansell, Nathan; Klein, Eric; Terasmaa, Jaanus; Dodd, Justin

    2015-04-01

    Radiocarbon dated, finely laminated lake sediments record Holocene precipitation changes from southern Estonia. Modern water isotope data suggest that Lake Nuudsaku is a mostly open system that is primarily fed by winter precipitation and groundwater, and summer precipitation plays only a secondary role in the overall hydrologic balance. Initial results indicate that changes in insolation likely drove the overall Holocene pattern with relatively wet conditions during the early Holocene, followed by arid conditions during the middle Holocene and a return to wetter conditions during the late Holocene. However, there is pronounced millennial and centennial-scale variability that cannot be explained by insolation forcing alone. Notably, there is a trend toward wetter conditions from ~4.0 to 2.0 ka, followed by a trend toward drier conditions during the last 2 millennia. This late Holocene pattern diverges from the pattern observed in records from north-central Estonia that suggest an overall trend of wetter conditions for the last ~4 ka. These initial results thus indicate that the Lake Nuudsaku sediments have the potential to yield a unique near-annual to decade-scale record of past precipitation changes from the southern Baltic region.

  2. Arctic Vortex changes alter the sources and isotopic values of precipitation in northeastern US.

    PubMed

    Puntsag, Tamir; Mitchell, Myron J; Campbell, John L; Klein, Eric S; Likens, Gene E; Welker, Jeffrey M

    2016-03-14

    Altered atmospheric circulation, reductions in Arctic sea ice, ocean warming, and changes in evaporation and transpiration are driving changes in the global hydrologic cycle. Precipitation isotopic (δ(18)O and δ(2)H) measurements can help provide a mechanistic understanding of hydrologic change at global and regional scales. To study the changing water cycle in the northeastern US, we examined the longest (1968-2010) record of precipitation isotope values, collected at the Hubbard Brook Experimental Forest in New Hampshire, US (43(°)56'N, 71(°)45'W). We found a significant reduction in δ(18)O and δ(2)H values over the 43-year record, coupled with a significant increase in d-excess values. This gradual reduction in δ(18)O and δ(2)H values unexpectedly occurred during a period of regional warming. We provide evidence that these changes are governed by the interactions among the Atlantic Multidecadal Oscillation, loss of Arctic sea ice, the fluctuating jet stream, and regular incursions of polar air into the northeastern US.

  3. Arctic Vortex changes alter the sources and isotopic values of precipitation in northeastern US

    PubMed Central

    Puntsag, Tamir; Mitchell, Myron J.; Campbell, John L.; Klein, Eric S.; Likens, Gene E.; Welker, Jeffrey M.

    2016-01-01

    Altered atmospheric circulation, reductions in Arctic sea ice, ocean warming, and changes in evaporation and transpiration are driving changes in the global hydrologic cycle. Precipitation isotopic (δ18O and δ2H) measurements can help provide a mechanistic understanding of hydrologic change at global and regional scales. To study the changing water cycle in the northeastern US, we examined the longest (1968–2010) record of precipitation isotope values, collected at the Hubbard Brook Experimental Forest in New Hampshire, US (43o56′N, 71o45′W). We found a significant reduction in δ18O and δ2H values over the 43-year record, coupled with a significant increase in d-excess values. This gradual reduction in δ18O and δ2H values unexpectedly occurred during a period of regional warming. We provide evidence that these changes are governed by the interactions among the Atlantic Multidecadal Oscillation, loss of Arctic sea ice, the fluctuating jet stream, and regular incursions of polar air into the northeastern US. PMID:26971874

  4. Arctic Vortex changes alter the sources and isotopic values of precipitation in northeastern US

    NASA Astrophysics Data System (ADS)

    Puntsag, Tamir; Mitchell, Myron J.; Campbell, John L.; Klein, Eric S.; Likens, Gene E.; Welker, Jeffrey M.

    2016-03-01

    Altered atmospheric circulation, reductions in Arctic sea ice, ocean warming, and changes in evaporation and transpiration are driving changes in the global hydrologic cycle. Precipitation isotopic (δ18O and δ2H) measurements can help provide a mechanistic understanding of hydrologic change at global and regional scales. To study the changing water cycle in the northeastern US, we examined the longest (1968-2010) record of precipitation isotope values, collected at the Hubbard Brook Experimental Forest in New Hampshire, US (43o56‧N, 71o45‧W). We found a significant reduction in δ18O and δ2H values over the 43-year record, coupled with a significant increase in d-excess values. This gradual reduction in δ18O and δ2H values unexpectedly occurred during a period of regional warming. We provide evidence that these changes are governed by the interactions among the Atlantic Multidecadal Oscillation, loss of Arctic sea ice, the fluctuating jet stream, and regular incursions of polar air into the northeastern US.

  5. Spatial distribution and controlling factors of stable isotopes in meteoric waters on the Tibetan Plateau: Implications for paleoelevation reconstruction

    NASA Astrophysics Data System (ADS)

    Li, Lin; Garzione, Carmala N.

    2017-02-01

    Debates persist about the interpretations of stable isotope based proxies for the surface uplift of the central-northern Tibetan Plateau. These disputes arise from the uncertain relationship between elevation and the δ18 O values of meteoric waters, based on modern patterns of isotopes in precipitation and surface waters. We present a large river water data set (1,340 samples) covering most parts of the Tibetan Plateau to characterize the spatial variability and controlling factors of their isotopic compositions. Compared with the amount-weighted mean annual oxygen isotopic values of precipitation, we conclude that river water is a good substitute for isotopic studies of precipitation in the high flat (e.g., elevation >3,300 m) interior of the Tibetan Plateau in the mean annual timescale. We construct, for the first time based on field data, contour maps of isotopic variations of meteoric waters (δ18 O, δD and d-excess) on the Tibetan Plateau. In the marginal mountainous regions of the Plateau, especially the southern through eastern margins, the δ18 O and δD values of river waters decrease with increasing mean catchment elevation, which can be modeled as a Rayleigh distillation process. However, in the interior of the Plateau, northward increasing trends in δ18 O and δD values are pronounced and present robust linear relations; d-excess values are lower than the marginal regions and exhibit distinct contrasts between the eastern (8 ‰- 12 ‰) and western (<8‰) Plateau. We suggest that these isotopic features of river waters in the interior of the Tibetan Plateau result from the combined effects of: 1) mixing of different moisture sources transported by the South Asian monsoon and Westerly winds; 2) contribution of moisture from recycled surface water; and 3) sub-cloud evaporation. We further provide a sub-cloud evaporation modified Rayleigh distillation and mixing model to simulate the isotopic variations in the western Plateau. Results of this work

  6. Spatial evolution of Zn-Fe-Pb isotopes of sphalerite within a single ore body: A case study from the Dongshengmiao ore deposit, Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Gao, Zhaofu; Zhu, Xiangkun; Sun, Jian; Luo, Zhaohua; Bao, Chuang; Tang, Chao; Ma, Jianxiong

    2017-03-01

    Analyses of sphalerite minerals from the characteristic brecciated Zn-Pb ores of the main ore body in the giant Dongshengmiao deposit have revealed variations in δ66Zn from 0.17 to 0.40‰ and in δ56Fe from -1.78 to -0.35‰. Further, the investigated pyrrhotite samples have iron that is isotopically similar to that of associated sphalerite minerals. The most distinctive pattern revealed by the zinc and iron isotope data is the lateral trend of increasing δ66Zn and δ56Fe values from southwest to northeast within the main ore body. The lead isotopic homogeneity of ore sulfides from the main ore body suggests that there is only one significant source for metal, thus precluding the mixing of multiple metal sources as the key factor controlling spatial variations of zinc and iron isotopes. The most likely control on spatial variations is Rayleigh fractionation during hydrothermal fluid flow, with lighter Zn and Fe isotopes preferentially incorporated into the earliest sulfides to precipitate from fluids. Precipitations of sphalerite and pyrrhotite have played vital roles in the Zn and Fe isotopic variations, respectively, of the ore-forming system. Accordingly, the larger isotopic variability for Fe than Zn within the same hydrothermal system perhaps resulted from a larger proportion of precipitation for pyrrhotite than for sphalerite. The lateral trend pattern revealed by the zinc and iron isotope data is consistent with the occurrence of a cystic-shaped breccia zone, which is characterized by marked elevation in Cu. The results further confirm that Zn and Fe isotopes can be used as a vectoring tool for mineral prospecting.

  7. Li isotope fractionation in aragonite precipitated from seawater at different rates

    NASA Astrophysics Data System (ADS)

    Gabitov, R. I.; Schmitt, A. K.; Gaetani, G. A.; Cohen, A. L.; Watson, E. B.; Rosner, M.

    2009-12-01

    The marine carbonates retain 7Li/6Li signatures of seawater and may record fluctuations in global hydrothermal fluid circulation or weathering rate of continental rocks. The development of a 7Li/6Li paleoproxy requires evaluating the influence of environmental parameters such as seawater composition and growth kinetics on 7Li/6Li fractionation in carbonates. A number of studies suggest that 7Li/6Li of biogenic and abiogenic aragonite is not affected by temperature, salinity, pH, or pCO2 (Marriott et al. 2004 a,b; Rollion-Bar et al. 2009). However, the influence of aragonite precipitation rate on 7Li/6Li fractionation has not been evaluated. We have carried out aragonite precipitation experiments to investigate this, and found that 7Li/6Li increases by up to ~4‰ as precipitation rate increases from 0.3 to 20 µmol/min. Bulk Li isotope analyses of two aragonite samples and corresponding fluids were performed using a Thermo Scientific NEPTUNE MC-ICP-MS at WHOI. In situ measurements of the same samples were conducted with the CAMECA ims 1270 ion microprobe at UCLA; two glass standards NIST-612 and 614 were analyzed for assessing instrumental reproducibility. Ion probe analyses were performed a 2-5 nA 16O- primary beam with 25-30 µm lateral dimensions. 7Li/6Li ratios were measured by peak switching. Single spot analyses consisted of 60-72 cycles with counting times for 6Li and 7Li of 10 and 4 seconds, respectively. Each spot was pre-sputtered until 7Li/6Li reached a steady-state value. Average ion microprobe instrumental mass fractionations for 7Li/6Li are approximately -3 and +12 ‰ for aragonite and silicate glass respectively. Our results suggest a positive relationship between aragonite precipitation rate and 7Li/6Li fractionation. Bulk (ICP-MS) measurements indicate that 7Li/6Li increased by ~2 ‰ with increasing precipitation rate of aragonite from 0.3 to 20 µmol/min. The intra-sample standard deviation (SD) was <0.8‰. The mass of aragonite precipitated in

  8. Spatially resolved genomic, stable isotopic, and lipid analyses of a modern freshwater microbialite from Cuatro Ciénegas, Mexico.

    PubMed

    Nitti, Anthony; Daniels, Camille A; Siefert, Janet; Souza, Valeria; Hollander, David; Breitbart, Mya

    2012-07-01

    Microbialites are biologically mediated carbonate deposits found in diverse environments worldwide. To explore the organisms and processes involved in microbialite formation, this study integrated genomic, lipid, and both organic and inorganic stable isotopic analyses to examine five discrete depth horizons spanning the surface 25 mm of a modern freshwater microbialite from Cuatro Ciénegas, Mexico. Distinct bacterial communities and geochemical signatures were observed in each microbialite layer. Photoautotrophic organisms accounted for approximately 65% of the sequences in the surface community and produced biomass with distinctive lipid biomarker and isotopic (δ(13)C) signatures. This photoautotrophic biomass was efficiently degraded in the deeper layers by heterotrophic organisms, primarily sulfate-reducing proteobacteria. Two spatially distinct zones of carbonate precipitation were observed within the microbialite, with the first zone corresponding to the phototroph-dominated portion of the microbialite and the second zone associated with the presence of sulfate-reducing heterotrophs. The coupling of photoautotrophic production, heterotrophic decomposition, and remineralization of organic matter led to the incorporation of a characteristic biogenic signature into the inorganic CaCO(3) matrix. Overall, spatially resolved multidisciplinary analyses of the microbialite enabled correlations to be made between the distribution of specific organisms, precipitation of carbonate, and preservation of unique lipid and isotopic geochemical signatures. These findings are critical for understanding the formation of modern microbialites and have implications for the interpretation of ancient microbialite records.

  9. Identifying Controls on the Stable Water Isotope Composition of Precipitation in the Southwestern Yukon Using GCMs

    NASA Astrophysics Data System (ADS)

    Field, R.; Moore, K.

    2007-12-01

    The goal of our work is to better understand what controls the stable water isotope (SWI) composition of precipitation in the southwestern Yukon, and in particular, to better-interpret the SWI signal from the Mount Logan ice core. To this end, we are conducting experiments with the GISS ModelE general circulation model, which is equipped with SWI diagnostics. One feature of interest in the Mt. Logan ice core record is a significant drop in d18O in the 1850's towards more depleted values. The current explanation for this shift is a transition in the North Pacific circulation towards a deeper Aleutian Low, with the stronger meridional flow bringing moisture from more southerly sources. Because of their greater arrival times, these air masses would have undergone a greater isotopic depletion than moisture from closer, colder sources under a more zonal flow regime. Although physically plausible, it is possible that the d18O drop caused by this proposed shift in circulation might be offset by warmer source evaporation conditions and integrated air mass trajectories, both of which would be associated with less depleted precipitation. To test the physical plausibility of the meridional hypothesis, we conducted numerical experiments with the NASA GISS ModelE isotopically-equipped general circulation model. In the Yukon, SWI variability is influenced, via the regional temperature, by the Pacific North America pattern and ENSO. We found that positive d18O anomalies in the SW Yukon region were in fact associated with a deeper Aleutian Low; it would appear that the effect of a longer transit time is offset by a warmer moisture transport pathway, in disagreement with the current moisture shift explanation. Our results are in agreement, however, with recent tree-ring reconstructions of the North Pacific Index, which suggest an 1850's shift towards a weaker Aleutian Low. We also found that the degree of Pacific control on the SW Yukon isotope signal is highly dependant on

  10. Spatial, seasonal, and source variability in the stable oxygen and hydrogen isotopic composition of tap waters throughout the USA

    USGS Publications Warehouse

    Landwehr, Jurate M.; Coplen, Tyler B.; Stewart, David W.

    2013-01-01

    To assess spatial, seasonal, and source variability in stable isotopic composition of human drinking waters throughout the entire USA, we have constructed a database of δ18O and δ2H of US tap waters. An additional purpose was to create a publicly available dataset useful for evaluating the forensic applicability of these isotopes for human tissue source geolocation. Samples were obtained at 349 sites, from diverse population centres, grouped by surface hydrologic units for regional comparisons. Samples were taken concurrently during two contrasting seasons, summer and winter. Source supply (surface, groundwater, mixed, and cistern) and system (public and private) types were noted. The isotopic composition of tap waters exhibits large spatial and regional variation within each season as well as significant at-site differences between seasons at many locations, consistent with patterns found in environmental (river and precipitation) waters deriving from hydrologic processes influenced by geographic factors. However, anthropogenic factors, such as the population of a tap’s surrounding community and local availability from diverse sources, also influence the isotopic composition of tap waters. Even within a locale as small as a single metropolitan area, tap waters with greatly differing isotopic compositions can be found, so that tap water within a region may not exhibit the spatial or temporal coherence predicted for environmental water. Such heterogeneities can be confounding factors when attempting forensic inference of source water location, and they underscore the necessity of measurements, not just predictions, with which to characterize the isotopic composition of regional tap waters. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

  11. Data set: 31 years of spatially distributed air temperature, humidity, precipitation amount and precipitation phase from a mountain catchment in the rain-snow transition zone

    USDA-ARS?s Scientific Manuscript database

    Thirty one years of spatially distributed air temperature, relative humidity, dew point temperature, precipitation amount, and precipitation phase data are presented for the Reynolds Creek Experimental Watershed. The data are spatially distributed over a 10m Lidar-derived digital elevation model at ...

  12. Who controls the monthly variations of NH4+ nitrogen isotope composition in precipitation?

    NASA Astrophysics Data System (ADS)

    Xiao, Hong-Wei; Xiao, Hua-Yun; Long, Ai-min; Wang, Yan-Li

    2012-07-01

    Nitrogen isotopes of ammonium (δ15N-NH4+) in precipitation have been analyzed, to study their monthly variations, from Oct. 2008 to Sep. 2009 at Guiyang, Southwest China. δ15N-NH4+ values were higher in winter and lower in summer showing a strong sine curve. In summer (rainy season), raindrop may remove more light ammonia by washout process, because raindrop incorporated 15NH3 preferentially while left the 14N in the atmosphere. At the same time, longer sunshine times imply more hv for producing H2SO4 of SO2 to H2SO4, which accelerates gaseous to particle conversion of NH3 to (NH4)2SO4 by unidirectional reactions for isotopic enriched 14N. The above two aspects can somewhat cause the seasonal variation of nitrogen isotopic composition, but are not the main or direct reasons. The temperature has an opposite trend with seasonal variation of δ15N values. The temperature not only causes seasonal variation of δ15N values, but also increases the volatilization rate of NH3 and microbial activities. And there is a robust linear relationship between temperature and δ15N, showing that the temperature is the main factor to decide the monthly variation of δ15N-NH4+.

  13. Spatial and temporal variability of daily precipitation concentration in the Lancang River basin, China

    NASA Astrophysics Data System (ADS)

    Shi, Wanli; Yu, Xuezhong; Liao, Wengen; Wang, Ying; Jia, Baozhen

    2013-07-01

    The Lorenz Curve, a concept used in economic theory, is used to quantify spatial-temporal variability in the daily time series of precipitation concentrations. The Lorenz Curve provides a graphical view of the cumulative percentage of total yearly precipitation. In addition, further extraction of the data using the Gini coefficient and Lorenz asymmetry coefficient provides a two-parameter measure of precipitation concentration and an explanation of the basis for the underlying inequalities in precipitation distribution. Based on the calculation of the precipitation concentration index (CI) and the Lorenz asymmetry coefficient (S) values from 1960 to 2010, variations in the trends and periodic temporal-spatial patterns of precipitation at 31 stations across the Lancang River basin are discussed. The results are as follows: (1) highest precipitation CI values occurred in the southern Lancang River basin, whereas the lowest precipitation CI values were mainly observed in the upper reaches of the Lancang River basin, which features a more homogeneous temporal distribution of rainfall. S values throughout the entire basin were less than one, indicating that minor precipitation events have the highest contribution to overall precipitation inequality. (2) Application of the Mann-Kendall test revealed that a significant, decreasing trend in precipitation CI that exceeding the 95th percentile was detected in the upper and middle reaches of the Lancang River basin. However, there was only one significant (0.05) S value trend throughout the river. (3) Climate jumps in annual CI occurred during the early 1960s, 1970s and 1980s at Jinghong, Deqin and Zaduo stations, respectively. (4) Dominant periodic variations in precipitation CI, with periods of 4-17 years, were found. These results allow for an improved understanding of extreme climate events and improved river basin water resource management.

  14. An Analysis of Precipitation Isotope Distributions across Namibia Using Historical Data

    PubMed Central

    Kaseke, Kudzai Farai; Wang, Lixin; Wanke, Heike; Turewicz, Veronika; Koeniger, Paul

    2016-01-01

    Global precipitation isoscapes based on the Global Network for Isotopes in Precipitation (GNIP) network are an important toolset that aid our understanding of global hydrologic cycles. Although the GNIP database is instrumental in developing global isoscapes, data coverage in some regions of hydrological interest (e.g., drylands) is low or non-existent thus the accuracy and relevance of global isoscapes to these regions is debatable. Capitalizing on existing literature isotope data, we generated rainfall isoscapes for Namibia (dryland) using the cokriging method and compared it to a globally fitted isoscape (GFI) downscaled to country level. Results showed weak correlation between observed and predicted isotope values in the GFI model (r2 < 0.20) while the cokriging isoscape showed stronger correlation (r2 = 0.67). The general trend of the local cokriging isoscape is consistent with synoptic weather systems (i.e., influences from Atlantic Ocean maritime vapour, Indian Ocean maritime vapour, Zaire Air Boundary, the Intertropical Convergence Zone and Tropical Temperate Troughs) and topography affecting the region. However, because we used the unweighted approach in this method, due to data scarcity, the absolute values could be improved in future studies. A comparison of local meteoric water lines (LMWL) constructed from the cokriging and GFI suggested that the GFI model still reflects the global average even when downscaled. The cokriging LMWL was however more consistent with expectations for an arid environment. The results indicate that although not ideal, for data deficient regions such as many drylands, the unweighted cokriging approach using historical local data can be an alternative approach to modelling rainfall isoscapes that are more relevant to the local conditions compared to using downscaled global isoscapes. PMID:27144269

  15. An Analysis of Precipitation Isotope Distributions across Namibia Using Historical Data.

    PubMed

    Kaseke, Kudzai Farai; Wang, Lixin; Wanke, Heike; Turewicz, Veronika; Koeniger, Paul

    2016-01-01

    Global precipitation isoscapes based on the Global Network for Isotopes in Precipitation (GNIP) network are an important toolset that aid our understanding of global hydrologic cycles. Although the GNIP database is instrumental in developing global isoscapes, data coverage in some regions of hydrological interest (e.g., drylands) is low or non-existent thus the accuracy and relevance of global isoscapes to these regions is debatable. Capitalizing on existing literature isotope data, we generated rainfall isoscapes for Namibia (dryland) using the cokriging method and compared it to a globally fitted isoscape (GFI) downscaled to country level. Results showed weak correlation between observed and predicted isotope values in the GFI model (r2 < 0.20) while the cokriging isoscape showed stronger correlation (r2 = 0.67). The general trend of the local cokriging isoscape is consistent with synoptic weather systems (i.e., influences from Atlantic Ocean maritime vapour, Indian Ocean maritime vapour, Zaire Air Boundary, the Intertropical Convergence Zone and Tropical Temperate Troughs) and topography affecting the region. However, because we used the unweighted approach in this method, due to data scarcity, the absolute values could be improved in future studies. A comparison of local meteoric water lines (LMWL) constructed from the cokriging and GFI suggested that the GFI model still reflects the global average even when downscaled. The cokriging LMWL was however more consistent with expectations for an arid environment. The results indicate that although not ideal, for data deficient regions such as many drylands, the unweighted cokriging approach using historical local data can be an alternative approach to modelling rainfall isoscapes that are more relevant to the local conditions compared to using downscaled global isoscapes.

  16. Evaluation of eight high spatial resolution gridded precipitation products in Adige Basin (Italy) at multiple temporal and spatial scales.

    PubMed

    Duan, Zheng; Liu, Junzhi; Tuo, Ye; Chiogna, Gabriele; Disse, Markus

    2016-12-15

    This study provides a comprehensive evaluation of eight high spatial resolution gridded precipitation products in Adige Basin located in Italy within 45-47.1°N. The Adige Basin is characterized by a complex topography, and independent ground data are available from a network of 101 rain gauges during 2000-2010. The eight products include the Version 7 TRMM (Tropical Rainfall Measuring Mission) Multi-satellite Precipitation Analysis 3B42 product, three products from CMORPH (the Climate Prediction Center MORPHing technique), i.e., CMORPH_RAW, CMORPH_CRT and CMORPH_BLD, PCDR (Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Climate Data Record), PGF (Global Meteorological Forcing Dataset for land surface modelling developed by Princeton University), CHIRPS (Climate Hazards Group InfraRed Precipitation with Station data) and GSMaP_MVK (Global Satellite Mapping of Precipitation project Moving Vector with Kalman-filter product). All eight products are evaluated against interpolated rain gauge data at the common 0.25° spatial resolution, and additional evaluations at native finer spatial resolution are conducted for CHIRPS (0.05°) and GSMaP_MVK (0.10°). Evaluation is performed at multiple temporal (daily, monthly and annual) and spatial scales (grid and watershed). Evaluation results show that in terms of overall statistical metrics the CHIRPS, TRMM and CMORPH_BLD comparably rank as the top three best performing products, while the PGF performs worst. All eight products underestimate and overestimate the occurrence frequency of daily precipitation for some intensity ranges. All products tend to show higher error in the winter months (December-February) when precipitation is low. Very slight difference can be observed in the evaluation metrics and aspects between at the aggregated 0.25° spatial resolution and at the native finer resolutions (0.05°) for CHIRPS and (0.10°) for GSMaP_MVK products. This study has implications

  17. Holocene temperatures and isotopes of precipitation in Northwest Greenland recorded in lacustrine organic materials

    NASA Astrophysics Data System (ADS)

    Lasher, G. Everett; Axford, Yarrow; McFarlin, Jamie M.; Kelly, Meredith A.; Osterberg, Erich C.; Berkelhammer, Max B.

    2017-08-01

    Reconstructions of Holocene lake water isotopic composition based upon subfossil aquatic organic material offer new insights into Arctic climate. We present quantitative estimates of warmth during the Holocene Thermal Maximum in northwest Greenland, inferred from oxygen isotopes of chironomid head capsules and aquatic moss preserved in lake sediments. δ18O values of chironomids from surface sediments of multiple Greenland lakes indicate that these subfossil remains record the δ18O values of the lake water in which they grow. Our lake water δ18O reconstruction is supported by downcore agreement with δ18O values in aquatic moss and chironomid remains. δ18O of both organic materials from Secret Lake decrease after 4 ka (ka = thousands of years ago) by 3‰ into the Neoglacial. We argue that lake water at Secret Lake primarily reflects precipitation δ18O values, which is strongly correlated with air temperature in NW Greenland, and that this signal is biased towards summer and early autumn conditions. Other factors may have influenced Secret Lake δ18O values through the Holocene, including evaporation of lake water and changing seasonality and source of precipitation. The maximum early Holocene summer and early autumn-biased temperature anomaly at Secret Lake is 2.5-4 °C warmer than present from 7.7 (the beginning of our record) to ∼6 ka. The maximum late Holocene cold anomaly (which includes the Little Ice Age) is 1.5-3 °C colder than present. These ranges of possible temperature anomalies reflect uncertainty in the δ18O - temperature relationship for precipitation at the study site through the Holocene.

  18. Frequency of occurrence and spatial distribution of very high daily precipitation totals in Slovakia

    NASA Astrophysics Data System (ADS)

    Faško, Pavel; Švec, Marek; Šťastný, Pavel; Bochníček, Oliver; Kajaba, Peter

    2015-04-01

    Daily precipitation totals ≥ 50 mm are recorded in precipitation station network of SHMI only in certain years. Such daily precipitation totals can already cause some damage. From available data series with precipitation totals were processed so that the number of stations that recorded daily precipitation totals ≥ 50 mm, ≥ 70 mm, ≥ 100 mm, ≥ 150 mm a ≥ 200 mm was assigned for the individual dates. Dates with selected precipitation totals have been sorted chronologically, also by their occurrence in the individual months of the year and eventually classified by to the overall number of recorded daily precipitation totals ≥ 50 mm and higher, from the date with the highest number of such daily precipitation totals to date with the lowest number of such daily precipitation totals recorded in station network of Slovakia. Available data have been processed since 1951 respectively 1965 and for the spatial analysis since 1981. Dates with the occurrence of very high daily precipitation totals represent a good material for selection of extreme meteorological and hydrological situations. In this contex it is striking that there is frequent presence of dates with higher number of cases with daily precipitation totals ≥ 50 mm, in the 90s of the last century and the present course of the 21st century. The spatial distribution of very high daily precipitation totals and the frequency of their occurrence indicate that there are some regions where the occurrence of such high daily precipitation totals is clearly higher not only in absolute terms, but also in the annual regime. Important is the finding that in Slovakia such a high daily precipitation totals are not concentrated in all the mountainous areas equally, and in the lowlands of southwestern Slovakia there are isolated regions with even higher number of such precipitation totals than in some mountain areas, or even in eastern Slovakia, where it rains more regularly. It's caused by the summer storm downpours

  19. The remarkable wide range spatial scaling of TRMM precipitation

    NASA Astrophysics Data System (ADS)

    Pinel, J.; Lovejoy, S.; Schertzer, D.; Allaire, V.

    2007-12-01

    The advent of space borne precipitation radar has opened up the possibility of studying the variability of global precipitation over huge ranges of scale while avoiding many of the calibration and sparse network problems which plague ground based rain gage and radar networks. We studied 1176 consecutive orbits of attenuation- corrected near surface reflectivity measurements from the TRMM satellite PR instrument. We find that for well- measured statistical moments (orders 0 < q < 2) corresponding to dBZ < 57 and probabilities > 10**-6, that the residuals with respect to a pure scaling (power law) variability are remarkably low: to within 6.4 percent over the range 20,000 km down to 4.3 km. We argue that higher order moments are biased due to inadequately corrected attenuation effects. When a stochastic three - parameter universal multifractal cascade model is used to model both the reflectivity and the minimum detectable signal of the radar (which was about twice the mean), we find that we can explain all the same statistics to within 4.6 percent over the same range. The effective outer scale of the variability was found to be 32,000 +- 2000 km. The fact that this is somewhat larger than the planetary scale (20,000 km) is a consequence of the residual variability of precipitation at the planetary scales. With the help of numerical simulations we were able to estimate the three fundamental parameters as alpha = 1.5, C1 = 0.63 +- 0.02 and H = 0.00 +- 0.01 (the multifractal index, the codimension of the mean and the nonconservation parameter respectively). There was no error estimate on α since although alpha = 1.5 was roughly the optimum value, this conclusion depended on assumptions about the instrument at both low and high reflectivities. The value H = 0 means that the reflectivity can be modeled as a pure multiplicative process, i.e. that the reflectivity is conserved from scale to scale. We show that by extending the model down to the inner "relaxation scale

  20. The remarkable wide range spatial scaling of TRMM precipitation

    NASA Astrophysics Data System (ADS)

    Lovejoy, S.; Schertzer, D.; Allaire, V. C.

    2008-10-01

    The advent of space borne precipitation radar has opened up the possibility of studying the variability of global precipitation over huge ranges of scale while avoiding many of the calibration and sparse network problems which plague ground based rain gage and radar networks. We studied 1176 consecutive orbits of attenuation-corrected near surface reflectivity measurements from the TRMM satellite PR instrument. We find that for well-measured statistical moments (orders 0 < q < 2) corresponding to radar reflectivities with dBZ < 57 and probabilities > 10 - 6 , that the residuals with respect to a pure scaling (power law) variability are remarkably low: ± 6.4% over the range 20,000 km down to 4.3 km. We argue that higher order moments are biased due to inadequately corrected attenuation effects. When a stochastic three — parameter universal multifractal cascade model is used to model both the reflectivity and the minimum detectable signal of the radar (which was about twice the mean), we find that we can explain the same statistics to within ± 4.6% over the same range. The effective outer scale of the variability was found to be 32,000 ± 2000 km. The fact that this is somewhat larger than the planetary scale (20,000 km) is a consequence of the residual variability of precipitation at the planetary scales. With the help of numerical simulations we were able to estimate the three fundamental parameters as α ≈ 1.5, C1 = 0.63 ± 0.02 and H = 0.00 ± 0.01 (the multifractal index, the codimension of the mean and the nonconservation parameter respectively). There was no error estimate on α since although α = 1.5 was roughly the optimum value, this conclusion depended on assumptions about the instrument at both low and high reflectivities. The value H = 0 means that the reflectivity can be modeled as a pure multiplicative process, i.e. that the reflectivity is conserved from scale to scale. We show that by extending the model down to the inner "relaxation scale

  1. Isotopic equilibrium between precipitation and water vapor: evidence from continental rains in central Kenya

    NASA Astrophysics Data System (ADS)

    Soderberg, K.; Gerlein, C.; Kemeny, P. C.; Caylor, K. K.

    2013-12-01

    An accurate understanding of the relationships between the isotopic composition of liquid water and that of water vapor in the environment can help describe hydrologic processes across many scales. One such relationship is the isotopic equilibrium between falling raindrops and the surrounding vapor. The degree of equilibration is used to model the isotopic composition of precipitation in isotope-enable general circulation models and land-atmosphere exchange models. Although this equilibrium has been a topic of isotope hydrology research for more than four decades, few studies have included vapor measurements to validate modeling efforts. Recent advances in laser technology have allowed for in situ vapor measurements at high temporal resolution (e.g., >1 Hz). Here we present concomitant rain and vapor measurements for a series of 17 rain events during the 'Continental' rainy season (June through August) at Mpala Research Center in central Kenya. Rain samples (n=218) were collected at intervals of 2 to 35 minutes (median of 3 minutes) depending on the rain rate (0.4 to 10.5 mm/hr). The volume-weighted mean rain values for δ18O, δ2H and D-excess (δ2H - 8* δ18O) were 0.1 ‰, 10.7 ‰, and 10.1 ‰. These values are more enriched than the annual weighted means reported for the area (-2.2 ‰, -7.6 ‰, and 11.0 ‰, respectively). Vapor was measured continuously at ~2Hz (DLT-100, Los Gatos Research), with an inverted funnel intake 4m above the ground surface. The mean vapor isotopic composition during the rain events was -10.0 +/- 1.2 ‰ (1 σ) for δ18O and -73.9 +/- 7.0 ‰ for δ2H. The difference between the rain sample isotopic composition and that of liquid in isotopic equilibrium with the corresponding vapor at the ambient temperature was 0.8 +/- 2.2 ‰ for δ18O and 6.2 +/- 7.0 ‰ for δ2H. This disequilibrium was found to correlate with the natural log of rain rate (R2 of 0.26 for δ18O and 0.46 for δ2H), with lower rain rates having larger

  2. The use of Pb, Sr, and Hg isotopes in Great Lakes precipitation as a tool for pollution source attribution.

    PubMed

    Sherman, Laura S; Blum, Joel D; Dvonch, J Timothy; Gratz, Lynne E; Landis, Matthew S

    2015-01-01

    The anthropogenic emission and subsequent deposition of heavy metals including mercury (Hg) and lead (Pb) present human health and environmental concerns. Although it is known that local and regional sources of these metals contribute to deposition in the Great Lakes region, it is difficult to trace emissions from point sources to impacted sites. Recent studies suggest that metal isotope ratios may be useful for distinguishing between and tracing source emissions. We measured Pb, strontium (Sr), and Hg isotope ratios in daily precipitation samples that were collected at seven sites across the Great Lakes region between 2003 and 2007. Lead isotope ratios ((207)Pb/(206)Pb=0.8062 to 0.8554) suggest that Pb deposition was influenced by coal combustion and processing of Mississippi Valley-Type Pb ore deposits. Regional differences in Sr isotope ratios ((87)Sr/(86)Sr=0.70859 to 0.71155) are likely related to coal fly ash and soil dust. Mercury isotope ratios (δ(202)Hg=-1.13 to 0.13‰) also varied among the sites, likely due to regional differences in coal isotopic composition, and fractionation occurring within industrial facilities and in the atmosphere. These data represent the first combined characterization of Pb, Sr, and Hg isotope ratios in precipitation collected across the Great Lakes region. We demonstrate the utility of multiple metal isotope ratios in parallel with traditional trace element multivariate statistical modeling to enable more complete pollution source attribution.

  3. The spatial patterns of soil respiration regulated by biological and environmental variables along a precipitation gradient

    NASA Astrophysics Data System (ADS)

    Xu, W.; Li, X.; Liu, W.; Li, L.; Hou, L.; Shi, H.; Xia, J.; Liu, D.; Zhang, H.; Chen, Y.; Cai, W.; Fu, Y.; Yuan, W.

    2015-12-01

    Precipitation is a key environmental factor in determining ecosystem structure and function. Knowledge of how soil respiration responds to climate change (precipitation etc.) and human activities (grazing, clipping etc.) is crucial for assessing the impacts of climate change on terrestrial ecosystems and for improving model simulations and predictions of future global C cycling in response to human activities. In this study, we examined the spatial patterns of soil respiration along a precipitation gradient from 176.7 mm to 398.1 mm. Our results showed that soil respiration increased linearly with increasing mean annual precipitation. The increasing trend was similar to the trends of shoot biomass, litter biomass and soil total C content along the precipitation gradient. Root biomass was described by quadratic curves along the increasing precipitation gradient and may result from the tradeoff of environmental regulation and carbon allocation. Our results indicated that precipitation was the primary controlling factor in determining the spatial pattern of soil respiration. The linear/nonlinear relationships in this study describing the variations of the ecosystem carbon process with precipitation could be useful for model development, parameterization and validation at the regional scale to improve predictions of how the carbon process in grasslands responds to climate change, land use and grassland management.

  4. Comparative analysis of spatial and seasonal variability: Austrian precipitation during the 20th century

    NASA Astrophysics Data System (ADS)

    Matulla, Christoph; Penlap, Edouard K.; Haas, Patrick; Formayer, Herbert

    2003-11-01

    The purpose of this investigation is to demonstrate the usability of objective methods to study the variability of precipitation and hence to contribute to a better understanding of spatial and seasonal variability of Austria's precipitation climate during the 20th century.This will be achieved by regionalizing the intra-annual variability of seasonal precipitation distributions during three non-overlapping 33 year samples (1901-33, 1934-66, 1967-99). Monthly precipitation totals were extracted at 31 Austrian stations from a homogenized long-term climate dataset provided by the Austrian weather service. Three statistical techniques, namely cluster analysis (CLA), rotated empirical orthogonal functions (REOFs) and an unsupervised learning procedure of artificial neural networks (ANNs), were utilized to find homogeneous precipitation regions.The results of summer (June, July, August (JJA)) and winter (December, January, February (DJF)) seasons are presented. The resulting homogeneous precipitation regions depend on season, period and method in this order. Hence, differences introduced by using different methods are small compared with those inferred by investigating different episodes and especially with those related to the seasons.During winter, three homogeneous precipitation regions are found, independent from the period considered. These regions can be assigned to different airflows dominating Austria's climate and triggering precipitation events during the cold season. The situation during summer is more complicated. Thus, at least four clusters are necessary to record the circumstances, which are caused by spatially inhomogeneous convective events such as thunderstorms.

  5. Silicon Isotopes doping experiments to measure quartz dissolution and precipitation rates at equilibrium and test the principle of detailed balance

    NASA Astrophysics Data System (ADS)

    Zhu, C.; Rimstidt, J. D.; Liu, Z.; Yuan, H.

    2016-12-01

    The principle of detailed balance (PDB) has been a cornerstone for irreversible thermodynamics and chemical kinetics for a long time, and its wide application in geochemistry has mostly been implicit and without experimental testing of its applicability. Nevertheless, many extrapolations based on PDB without experimental validation have far reaching impacts on society's mega environmental enterprises. Here we report an isotope doping method that independently measures simultaneous dissolution and precipitation rates and can test this principle. The technique reacts a solution enriched in a rare isotope of an element with a solid having natural isotopic abundances (Beck et al., 1992; Gaillardet, 2008; Gruber et al., 2013). Dissolution and precipitation rates are found from the changing isotopic ratios. Our quartz experiment doped with 29Si showed that the equilibrium dissolution rate remains unchanged at all degrees of undersaturation. We recommend this approach to test the validity of using the detailed balance relationship in rate equations for other substances.

  6. Stable Isotopic Composition of Precipitation from 2015-2016 Central Texas Rainfall Events

    NASA Astrophysics Data System (ADS)

    Maupin, C. R.; McChesney, C. L.; Roark, B.; Gorman, M. K.; Housson, A. L.

    2016-12-01

    Central Texas lies within the Southern Great Plains, a region where rainfall is of tremendous agricultural and associated socioeconomic importance. Paleoclimate records from speleothems in central Texas caves may assist in placing historical and recent drought and pluvial events in the context of natural variability. Effective interpretation of such records requires the nature and origin of variations in the meteoric δ18O signal transmitted from cloud to speleothem to be understood. Here we present a record of meteoric δ18O and δD from each individual precipitation event (δ18Op and δDp), collected by rain gauge in Austin, Texas, USA, from April 2015 through 2016. Backwards hybrid single-particle Lagrangian integrated trajectories (HYSPLITs) indicate the broader moisture source for each precipitation event during this time was the Gulf of Mexico. The local meteoric water line is within error of the global meteoric water line, suggesting minimal sourcing of evaporated continental vapor for precipitation. Total monthly rainfall followed the climatological pattern of a dual boreal spring and fall maximum, with highly variable event δ18Op and δDp values. Surface temperature during precipitation often exerts control over continental and mid latitude δ18Op values, but is not significantly correlated to study site δ18Op (p>0.10). Amount of rain falling during each precipitation event ("amount effect") explains a significant 18% of variance in δ18Op. We hypothesize that this relationship can be attributed to the following: 1) minimal recycling of continental water vapor during the study period; 2) the presence of synoptic conditions favoring intense boreal spring and fall precipitation, driven by a developing, and subsequently in-place, strong ENSO event coupled with a southerly flow from the open Gulf of Mexico; and 3) the meteorological nature of the predominant precipitating events over Texas during this time, mesoscale convective systems, which are known to

  7. Stable isotope compositions of waters in the Great Basin, United States 3. Comparison of groundwaters with modern precipitation

    USGS Publications Warehouse

    Smith, G.I.; Friedman, I.; Veronda, G.; Johnson, C.A.

    2002-01-01

    Groundwater samples from wells and springs, scattered over most of the Great Basin province, were collected and analyzed for their isotopic makeup. They were augmented by previously published isotopic data on groundwaters from southeast California and by several hundred unpublished isotopic analyses. The ratio of 2H (deuterium, D) to 1H, in water samples from valleys in parts of California, Idaho, Nevada, Oregon, and Utah, are here compared with the winter, summer, and annual isotopic compositions of precipitation falling in or near the sampled areas. The main goal of this study was to identify basins where the groundwaters have isotopic compositions that are "lighter" (depleted in the heavier isotope, D) relative to modern winter precipitation. Where these basins do not adjoin substantially higher terrain, we consider those light groundwaters to be of Pleistocene age and thus more than 10,000 years old. Where the groundwater is 10 to 19??? lighter than local winter precipitation, we consider it to be possibly an indication of Pleistocene water; where the ??D makeup is >20??? lighter, we consider it to be probably Pleistocene water. More than 80 sites underlain by waters of possible or probable Pleistocene age were identified.

  8. Amount Effect, Altitude, and Moisture Source Influences on Precipitation Isotopic Variability in the Galápagos Islands

    NASA Astrophysics Data System (ADS)

    Martin, N. J.; Conroy, J. L.; Noone, D. C.; Cobb, K. M.; Konecky, B. L.; Rea, S.

    2015-12-01

    Understanding how climate processes facilitate water isotope variability in precipitation over time and space is critical to interpreting isotope-based paleoclimate proxies, particularly in the eastern tropical Pacific where stable water isotope observations from precipitation (δ18Op and δDp) are sparse. Here we present a new 28-month record of daily δ18Op and δDp from Santa Cruz, Galápagos. With a prior 13-year record of monthly averaged precipitation isotope data from the island, these new data reveal valuable information on how meteorology, altitude, and source region characteristics influence the stable isotopic composition of precipitation in the region. Two sampling locations on Santa Cruz Island exhibit distinct local meteoric water lines; the drier, low elevation site (7m a.s.l.) has a significantly lower slope than the humid highland site (180m a.s.l.), likely resulting from greater reevaporation of falling rain. An altitude effect is also apparent, based on daily precipitation and δ18Op measurements across a 35 km transect of the island, with δ18Op decreasing by 0.2‰/100m elevation. HYSPLIT backward trajectory modeling shows air parcels producing rain events with the lowest δ18Op values originated over warmer waters to the north of the Galápagos; rain events with the highest δ18Op originated to the east. This difference provides a mechanism for changes in seasonal mean isotope ratios and shifts in isotope ratios due to systematic circulation changes, such as in association with ENSO phases. Daily δ18Op near sea level was significantly correlated with precipitation amount, as was monthly, amount-weighted δ18Op and precipitation at sea level and 180 m. However, accounting for the non-normality of the data substantially reduces the strength of the correlation between δ18Op and precipitation on monthly timescales while the δ18Op-precipitation relationship on daily timescales remained strong. Overall, we observe a stronger daily, rather than

  9. Iron isotope fractionation by microbial iron reduction in modern chemically precipitated sediments

    NASA Astrophysics Data System (ADS)

    Roden, E. E.; Tangalos, G. E.; Beard, B. L.; Johnson, C. M.; Alpers, C. N.; Shelobolina, E. S.; Xu, H.; Konishi, H.

    2008-12-01

    Laboratory experiments have demonstrated that dissimilatory microbial iron oxide reduction (DIR) can produce Fe(II) phases that have low 56Fe/54Fe ratios similar to those found in Neoarchean and Paleoproterozoic banded iron formations (BIFs) and shales. Direct application of these experiments to BIF formation has been hindered by the lack of Fe isotope data from modern environments that are analogous to BIFs. Here we report Fe inventories and isotopic compositions for chemically precipitated sediments in the Spring Creek Arm of Keswick Reservoir (SCAKR) downstream of the Iron Mountain acid mine drainage site in northern California, USA. The high concentration of reactive Fe(III) (ca. 50-100 mmol of amorphous Fe(III) oxyhydroxides per liter of bulk sediment) allows dissimilatory iron-reducing bacteria (DIRB) to predominate over dissimilatory sulfate-reducing bacteria in sediment carbon metabolism, making the SCAKR a better analog for BIFs compared to modern marine environments. DIR has generated millimolar concentrations of aqueous Fe(II) (Fe(II)aq) in SCAKR sediments. The Fe(II)aq has lower 56Fe/54Fe values than bulk HCl-extractable Fe; δ56Fe values for bulk HCl-extractable Fe fall within the range previously defined for mafic- to intermediate-composition terrestrial igneous rocks, modern marine sediments, suspended river sediments, Proterozoic-Phanerozoic shales, loess, aerosols, and soils. After removal of pore fluid, sediment was reacted for 1 hr with 0.1M HCl to isolate solid-phase Fe(II) (Fe(II)s), which was likely a mixture of sorbed Fe(II) and amorphous surface-precipitated Fe(II) hydroxide. Subsequent 24-hr extraction with 0.5M HCl recovered amorphous Fe(III) oxide (Fe(III)am). Sediment incubation experiments with SCAKR sediment produced trends in in Fe isotopic fractionations between Fe(II)aq, Fe(II)s, and Fe(III)am analogous to those observed in situ. Collectively the data suggest an equilibrium 56Fe/54Fe isotope fractionation between Fe(II)aq and Fe

  10. Stable isotope compositions of speleothems from the last interglacial - Spatial patterns of climate fluctuations in Europe

    NASA Astrophysics Data System (ADS)

    Demény, Attila; Kern, Zoltán; Czuppon, György; Németh, Alexandra; Leél-Őssy, Szabolcs; Siklósy, Zoltán; Lin, Ke; Hu, Hsun-Ming; Shen, Chuan-Chou; Vennemann, Torsten W.; Haszpra, László

    2017-04-01

    Studies on the last interglacial (LIG) can provide information on how our environment behaved in a period of slightly higher global temperatures at about 125 ± 4 ka, even if it is not the best analogue for the Holocene. The available LIG climate proxy records are usually better preserved and can be studied at a higher resolution than those of the preceding interglacials, allowing detailed comparisons. This paper presents complex stable hydrogen, carbon and oxygen isotope records obtained for carbonate (δ13C and δ18Ocarb) and fluid inclusion hosted water (δD and δ18Ow) of a stalagmite from the Baradla Cave system in Central Europe that covers most of the LIG, as proven by U-Th dates. Comparing its C and O isotope data with records reported for other speleothem (cave-hosted carbonate) deposits from Europe revealed the complex behavior of these climate proxies, with a concerted relative increase in 18O of carbonates from 128 to 120 ka and synchronized shifts in the opposite direction after 119 ka. The hydrogen isotope analyses of inclusion-hosted water extracted from the BAR-II stalagmite also correspond to the regional climate proxy records, with meaningful deviations from global temperature trends. Beside following the general paleotemperature pattern from the climate optimum (high δD values up to -64‰ around 120 ka) to the subsequent cooling starting at about 119 ka (low δD values down to -90‰ at about 109 ka), a period between 126.5 and 123 ka with low δD values (down to -81‰) is detected in the BAR-II stalagmite. Although the isotope shifts are muted in the C-O isotope data of carbonate due to competitive fractionation processes, the δ13C data show a positive relationship with the δD pattern, indicating humidity - and possibly temperature - variations. The periods with low δD values fit well to temperature and humidity changes inferred from proxy records from western Europe to the eastern Mediterranean. Spatial distributions of these variables

  11. Compound-specific stable isotope records of precipitation isotopes and paleotopographic evolution: Patterns of Cenozoic change in the Western U.S.

    NASA Astrophysics Data System (ADS)

    Hren, M. T.

    2014-12-01

    The topography of an orogen reflects the complex interplay between processes that occur at depth in the crust and processes such as erosion and weathering that shape the surface landscape. Reconstructions of paleotopography are critical for evaluating geodynamic models and separating effects of climatic and tectonic change in terrestrial records. Stable isotope paleoaltimetry has proved to be an important tool for understanding changes in topography through time, however this approach is complicated by factors such as mixing of moisture sources, uncertainty over how uplift impacts air mass transport and resultant isotope hydrology, and debate over what some proxies actually record. Hydrogen isotopes of organic molecules provide a means of reconstructing isotopes of ambient water, but these data are also impacted by factors that affect biological processes and stomatal regulation. Despite the myriad factors that can impact isotope fractionation in plant waxes, a growing body of data show these molecules to be an important record of precipitation isotopes when coupled with data that relates to ecosystem type. This study will examine the distribution of hydrogen isotopes of higher plant waxes across the western U.S. at key intervals of the Cenozoic to provide a snapshot of long-wavelength changes to topography and moisture sources from the Eocene to recent. These data demonstrate the utility of biomarker isotopes as a paleohydrologic/paleotopographic proxy and point to long-standing high topography over much of western U.S. throughout the Cenozoic.

  12. A multivariate conditional model for streamflow prediction and spatial precipitation refinement

    NASA Astrophysics Data System (ADS)

    Liu, Zhiyong; Zhou, Ping; Chen, Xiuzhi; Guan, Yinghui

    2015-10-01

    The effective prediction and estimation of hydrometeorological variables are important for water resources planning and management. In this study, we propose a multivariate conditional model for streamflow prediction and the refinement of spatial precipitation estimates. This model consists of high dimensional vine copulas, conditional bivariate copula simulations, and a quantile-copula function. The vine copula is employed because of its flexibility in modeling the high dimensional joint distribution of multivariate data by building a hierarchy of conditional bivariate copulas. We investigate two cases to evaluate the performance and applicability of the proposed approach. In the first case, we generate one month ahead streamflow forecasts that incorporate multiple predictors including antecedent precipitation and streamflow records in a basin located in South China. The prediction accuracy of the vine-based model is compared with that of traditional data-driven models such as the support vector regression (SVR) and the adaptive neuro-fuzzy inference system (ANFIS). The results indicate that the proposed model produces more skillful forecasts than SVR and ANFIS. Moreover, this probabilistic model yields additional information concerning the predictive uncertainty. The second case involves refining spatial precipitation estimates derived from the tropical rainfall measuring mission precipitationproduct for the Yangtze River basin by incorporating remotely sensed soil moisture data and the observed precipitation from meteorological gauges over the basin. The validation results indicate that the proposed model successfully refines the spatial precipitation estimates. Although this model is tested for specific cases, it can be extended to other hydrometeorological variables for predictions and spatial estimations.

  13. Hydrology of precipitation and groundwater in a plateau area, southward South Carpathians, Mehedinti district, Romania, identified from isotope and climate monitoring

    NASA Astrophysics Data System (ADS)

    Bojar, Ana-Voica; Halas, Stanislaw

    2014-05-01

    permil. The d-excess values are the lowest in the summer/early fall and highest in the winter. Spring distribution with altitude indicate the presence of two aquifers. The hydrogen and oxygen isotopic composition of spring waters plot close to the midpoint of the LMWL. The isotope data indicate that an integration rain- and snowfall is the water source for the springs and drill water. Therefore, spring isotopic composition is controlled by climate, including amounts of precipitation gain and evaporation loss. Less moisture on multiannual to decadal time scale most probably leads to lower water table height and reduced inflow. We are grateful to the Faculty of Earth Sciences and Spatial Managements, Maria Curie-Sklodowska University, Lublin, for free access to PICARRO cavity ring down spectrometer.

  14. Quantification of dynamic soil-vegetation feedbacks following an isotopically labelled precipitation pulse

    NASA Astrophysics Data System (ADS)

    Piayda, Arndt; Dubbert, Maren; Siegwolf, Rolf; Cuntz, Matthias; Werner, Christiane

    2017-05-01

    The presence of vegetation alters hydrological cycles of ecosystems. Complex plant-soil interactions govern the fate of precipitation input and water transitions through ecosystem compartments. Disentangling these interactions is a major challenge in the field of ecohydrology and a pivotal foundation for understanding the carbon cycle of semi-arid ecosystems. Stable water isotopes can be used in this context as tracer to quantify water movement through soil-vegetation-atmosphere interfaces. The aim of this study is to disentangle vegetation effects on soil water infiltration and distribution as well as dynamics of soil evaporation and grassland water use in a Mediterranean cork oak woodland during dry conditions. An irrigation experiment using δ18O labelled water was carried out in order to quantify distinct effects of tree and herbaceous vegetation on the infiltration and distribution of event water in the soil profile. Dynamic responses of soil and herbaceous vegetation fluxes to precipitation regarding event water use, water uptake depth plasticity, and contribution to ecosystem soil evaporation and transpiration were quantified. Total water loss to the atmosphere from bare soil was as high as from vegetated soil, utilizing large amounts of unproductive evaporation for transpiration, but infiltration rates decreased. No adjustments of main root water uptake depth to changes in water availability could be observed during the experiment. This forces understorey plants to compete with adjacent trees for water in deeper soil layers at the onset of summer. Thus, understorey plants are subjected to chronic water deficits faster, leading to premature senescence at the onset of drought. Despite this water competition, the presence of cork oak trees fosters infiltration and reduces evapotranspirative water losses from the understorey and the soil, both due to altered microclimatic conditions under crown shading. This study highlights complex soil-plant-atmosphere and

  15. [Spatial Distribution of Stable Isotope from the Lakes in Typical Temperate Glacier Region].

    PubMed

    Shi, Xiao-yi; Pu, Tao; He, Yuan-qing; Lu, Hao; Niu, He-wen; Xia, Dun-sheng

    2016-05-15

    We focused mainly on the spatial variation and influencing factors of hydrogen and oxygen stable isotopes between water samples collected at the surface and different depths in the Lashi Lake in August, 2014. Hydrological supply characteristics of the lake in typical temperate glacier region were discussed. The results showed that the values of δ¹⁸O and δD in the Lashi Lake ranged from -12.98 per thousand to -8.16 per thousand with the mean of -9.75 per thousand and from -99.42 per thousand to -73.78 per thousand with the mean of -82.23 per thousand, respectively. There was a reversed spatial variation between δ¹⁸O and d. Relatively low values of δ¹⁸O with high values of d were found at the edge of the lake where the rivers drained into. Meanwhile, the values of d in the vertical profile varied little with depth, suggesting that the waters mixed sufficiently in the vertical direction. The d values increased at first and then decreased from east to west at different layers, but both increase and decrease exhibited different velocities, which were related to the river distribution, the locality of the lake and environmental conditions etc. River water and atmospheric precipitation were the main recharge sources of the Lashi Lake, and the melt-water of snow and ice might also be the supply resource. The δ¹⁸O values of lake water in glacier region decreased along the elevation (except for Lashi Lake), generally, this phenomenon was called "altitude effect". Moreover, high isotopic values of the lake water from non-glacier region were due to the evaporation effect.

  16. Spatial and temporal changes of precipitation concentration in Fars province, southwestern Iran

    NASA Astrophysics Data System (ADS)

    Abolverdi, Javad; Ferdosifar, Ghasem; Khalili, Davar; Kamgar-Haghighi, Ali Akbar

    2016-04-01

    Spatial and temporal changes in precipitation concentration are investigated using precipitation concentration index (CI), precipitation concentration period (PCP) and precipitation concentration degree (PCD). The non-parametric Mann-Kendall test is used to detect monotonic trends in CI time series. The study area is Fars province (southwestern Iran), represented by 47 recording gauges with daily precipitation time series records of at least 30 years, ending in 2008. The results revealed that based on CI values two sub-regions were identified, the central/northern sub-region with low CI values (high rainfall depths/several rainy days) and the southern sub-region with low rainfall/few rainy days. PCP analysis indicated an earlier arrival of the rainy season in western parts compared to eastern Fars province and also that annual precipitation mainly falls in winter. However, PCD analysis revealed that annual precipitation in northwestern Fars is less concentrated in several months, whereby, concentration in several months is observed in other parts of the study area. Significant upward trends at 5 % significance level is detected in 19 out of 47 stations with the tendency for occurrence of a rather high percentage of the annual total precipitation in a few days, which has the potential to cause major floods or droughts.

  17. Spatial and temporal precipitation variability as a component of site-specific crop yield variability

    NASA Astrophysics Data System (ADS)

    O'Neal, Monte Ray

    The purpose of this study was to determine spatial and temporal precipitation variability, and the effect of this variability on yield and profitability. On-farm precipitation data is currently being measured by site- specific farmers. One potential use of the data is to provide inputs for corn yield modeling, which has been performed with neural networks and simulation. Profitability of measuring on-farm data depends on spatial precipitation variability and its effect on yield. Precipitation and air temperature from corn silking to dent stages, scale of yield data, and a technology factor were used to model corn yield in east central Indiana at farm (250 ha), county, and state scales, using backpropagation neural networks with five data coding schemes. The best net gave a root-mean-squared error of 11.9% overall (10.9% farm, 10.5% county, 7.9% state yield), with maximum-value interval coding. Four rain gauges on the same farm, spaced apart 1.02 to 3.04 km, gave a median absolute deviation of precipitation among gauges, by corn and soybean phenological phase, of 0.25 to 1.73 mm.day-1 (spatial variability). Median absolute deviation from a reference year was 0.17 to 3.40 mm.day-1 (temporal/year-to- year variability). Spatial variability was less than temporal variability, and frequently less than 1 mm. Three precipitation data sources-a National Weather Service (NWS) station on the same farm, the nearest non- urban NWS station, and a weighted mean of three nearest non-urban NWS stations (27-35 km distance)-were used to simulate corn yield by 1-ha grid cells with CERES-Maize. The percent absolute difference of simulated yield among the three sources (effect of spatial precipitation variability) was 15.8%. The percent absolute difference from long-term mean (temporal variability) was 21.5%, of the same order as spatial variability. A choice among nitrogen application strategies-variable-rate versus whole-field application, starter versus no starter-was made for the

  18. Non-Linear Responses to Precipitation and Shrub Encroachment in Semi-Arid Grassland: Isotopes and CO2 Fluxes Reveal Soil Microsite Alteration as Explanation

    NASA Astrophysics Data System (ADS)

    Cable, J. M.; Sun, W.; Ogle, K.; Williams, D. G.; Potts, D. L.; Scott, R. L.; Huxman, T. E.

    2006-12-01

    , where microbial respiration is expected to exceed root respiration. Spatial and temporal variation in root and microbial responses to precipitation suggest that root activity patterns and heterogeneous soil microsites contribute to the non-linearity between ecosystem production and seasonal precipitation. To develop a more process-based understanding of this non-linear phenomenon, we are developing a Bayesian inverse model that couples the respiration and isotope data, spatial variability in soil microsite properties, and models of root and microbial respiration. The inverse model is being used to explore the importance of small- scale processes (e.g., plant and microsite fluxes) to emergent properties at larger-scales (e.g., ecosystem dynamics along the encroachment gradient).

  19. Impact of spatial resolution of the precipitation data on hydrological Forecast

    NASA Astrophysics Data System (ADS)

    Davis, M.; Bardossy, A.; Sudheer, K.

    2013-05-01

    Flooding is a devastating problem for many countries all over the world. Real time forecasting is a necessary non-structural measure to fight against the damage. Adequate quantitative forecasting of the flood is necessary to provide enough precaution for the affected population. Time lead in the forecast is also a matter of concern considering its significance in the preparedness. The time-lead of forecast depends on the computational time along with the various other issues. The computation time depends on the whether the model is data intensive or process intensive. Considering the use of spatially distributed models in the forecast, the main dynamic data involved in the rainfall runoff models are the precipitation measurement. The data intensity of that depends on the spatial and temporal resolution of the precipitation data. The spatial resolution of the precipitation has the significance in the spatially distributed hydrological models. Neither should the resolution be so less that the quantitative prediction is disturbed nor too much to affect the time lead considerably. Finer spatial resolution of precipitation data may not even yield better forecast (A.Bardossy and T.Das, 2008). So the current study focuses on the impact of spatial and temporal resolution of the hydrological forecast. The spatially distributed model of HBV and HYMOD is being used for the analysis. Spatial resolutions from 1, 4, 9 and 25 square kilometers and a temporal resolution of daily to hourly time-series is also being analysed for their respective effects on prediction. The data from rain gauges are interpolated using the External Drift Kriging Method (EDK). The calibrations of the models are carried out using the Robust Parameter Estimation (ROPE) algorithm (S.K Singh and A. Bardossy, 2010). The framework is illustrated on the Upper Neckar catchment with 13 sub-catchments located in South West Germany. Preliminary results are encouraging. The optimum spatial resolution can be

  20. Spatial and Temporal Trends in Stable Carbon and Oxygen Isotope Ratios of Juvenile Winter Flounder

    EPA Science Inventory

    Isotopic ratios of fish otoliths have been used in numerous studies as natural tags or markers to aid the study of connectivity among fish populations. We investigated the use of spatial and temporal changes in the stable carbon and oxygen isotope ratios of otoliths to different...

  1. Spatial and Temporal Trends in Stable Carbon and Oxygen Isotope Ratios of Juvenile Winter Flounder

    EPA Science Inventory

    Isotopic ratios of fish otoliths have been used in numerous studies as natural tags or markers to aid the study of connectivity among fish populations. We investigated the use of spatial and temporal changes in the stable carbon and oxygen isotope ratios of otoliths to different...

  2. Quantification of dynamic soil - vegetation feedbacks following an isotopically labelled precipitation pulse

    NASA Astrophysics Data System (ADS)

    Piayda, Arndt; Dubbert, Maren; Siegwolf, Rolf; Cuntz, Matthias; Werner, Christiane

    2017-04-01

    The presence of vegetation alters hydrological cycles of ecosystems. Complex plant-soil interactions govern the fate of precipitation input and water transitions through ecosystem compartments. Disentangling these interactions is a major challenge in the field of ecohydrology and pivotal foundation for understanding the carbon cycle of semi-arid ecosystems. Stable water isotopes can be used in this context as tracer to quantify water movement through soil-vegetation-atmosphere interfaces. The aim of this study is to disentangle vegetation effects on soil water infiltration and distribution as well as dynamics of soil evaporation and grassland water-use in a Mediterranean cork-oak woodland during dry conditions. An irrigation experiment using δ18O-labeled water was carried out in order to quantify distinct effects of tree and herbaceous vegetation on infiltration and distribution of event water in the soil profile. Dynamic responses of soil and herbaceous vegetation fluxes to precipitation regarding event water-use, water uptake depth plasticity and contribution to ecosystem evapotranspiration were quantified. Total water loss to the atmosphere from bare soil was as high as from vegetated soil, utilizing large amounts of unproductive water loss for biomass production, carbon sequestration and nitrogen fixation. During the experiment no adjustments of main root water uptake depth to changes of water availability could be observed, rendering light to medium precipitation events under dry conditions useless. This forces understory plants to compete with adjacent trees for soil water in deeper soil layers. Thus understory plants are faster subject to chronic drought, leading to premature senescence at the onset of drought. Despite this water competition, the presence of Cork oak trees fosters infiltration to large degrees. That reduces drought stress, caused by evapotranspiration, due to favourable micro climatic conditions under tree crown shading. This study

  3. A stable isotope record of orographic precipitation and continental evaporation across the Central Anatolian Plateau

    NASA Astrophysics Data System (ADS)

    Schemmel, Fabian; Mikes, Tamas; Rojay, Bora; Mulch, Andreas

    2013-04-01

    The Central Anatolian Plateau (CAP) in central Turkey, much like its larger counterparts in Tibet or the Andes, has a clear influence on regional atmospheric circulations and thus creates a distinct pattern of orographic rainout and rainshadow. Reconstructing these patterns over geological time is a major challenge for understanding the interplay of tectonic and Earth surface processes and their subsequent impact on atmospheric circulation and regional hydrology and ultimately on changes in biodiversity and ecosystems over time. Here we present the first large-scale characterization of hydrogen (δD) and oxygen (δ18O) stable isotopes in precipitation from more than 480 spring and surface water samples from the CAP as well as its northern (Pontic Mts.) and southern (Taurus Mts.) margins. The aim of this study is to quantify the influence of orographic rainout and secondary evaporation on the stable isotopic composition of these meteoric waters and further to establish a robust first-order isotopic template against which continental paleoclimate proxy data can be interpreted. The CAP is bordered by two E-W trending mountain ranges: the Pontic Mountains at the Black Sea coast and the Taurus Mountains at the Mediterranean coast that both serve as major orographic barriers to the transport of moisture, hence developing semi-humid climatic conditions on their windward flanks and arid conditions over the plateau interior. Differences in δD and δ18O values on the northern and southern plateau margins indicate different source regions and are in agreement with observed air parcel trajectories. The orographic rainout on the windward flanks of the Pontic Mountains exhibits isotopic lapse rates of -19 ‰/km for δD and -2.6 ‰/km for δ18O whereas the lapse rates of the Taurus Mountains are slightly higher with -20 ‰/km for δD and -2.9 ‰/km for δ18O across an elevation range of nearly 3000 m. The δD and δ18O values immediate lee of both mountain ranges attain the

  4. Spatial Bayesian hierarchical modeling of precipitation extremes over a large domain

    NASA Astrophysics Data System (ADS)

    Bracken, C.; Rajagopalan, B.; Cheng, L.; Kleiber, W.; Gangopadhyay, S.

    2016-08-01

    We propose a Bayesian hierarchical model for spatial extremes on a large domain. In the data layer a Gaussian elliptical copula having generalized extreme value (GEV) marginals is applied. Spatial dependence in the GEV parameters is captured with a latent spatial regression with spatially varying coefficients. Using a composite likelihood approach, we are able to efficiently incorporate a large precipitation data set, which includes stations with missing data. The model is demonstrated by application to fall precipitation extremes at approximately 2600 stations covering the western United States, -125°E to -100°E longitude and 30°N-50°N latitude. The hierarchical model provides GEV parameters on a 1/8° grid and, consequently, maps of return levels and associated uncertainty. The model results indicate that return levels and their associated uncertainty have a well-defined spatial structure. Maps of return levels provide information about the spatial variations of the risk of extreme precipitation in the western US and is expected to be useful for infrastructure planning.

  5. Precipitation regime and stable oxygen isotopes at Dome C, East Antarctica - a comparison of two extreme years 2009 and 2010

    NASA Astrophysics Data System (ADS)

    Schlosser, E.; Stenni, B.; Valt, M.; Cagnati, A.; Powers, J. G.; Manning, K. W.; Raphael, M.; Duda, M. G.

    2015-11-01

    At the East Antarctic deep ice core drilling site Dome C, daily precipitation measurements have been initiated in 2006 and are being continued until today. The amounts and stable isotope ratios of the precipitation samples as well as crystal types are determined. Within the measuring period, the two years 2009 and 2010 showed striking contrasting temperature and precipitation anomalies, particularly in the winter seasons. The reasons for these anomalies and their relation to stable isotope ratios are analysed using data from the mesoscale atmospheric model WRF (Weather Research and Forecasting Model) run under the Antarctic Mesoscale Prediction System (AMPS). 2009 was relatively warm and moist due to frequent warm air intrusions connected to amplification of Rossby waves in the circumpolar westerlies, whereas the winter of 2010 was extremely dry and cold. It is shown that while in 2010 a strong zonal atmospheric flow was dominant, in 2009 an enhanced meridional flow prevailed, which increased the meridional transport of heat and moisture onto the East Antarctic plateau and led to a number of high-precipitation/warming events at Dome C. This was also evident in a positive (negative) SAM index and a negative (positive) ZW3 index during the winter months of 2010 (2009). Changes in the frequency or seasonality of such event-type precipitation can lead to a strong bias in the air temperature derived from stable water isotopes in ice cores.

  6. Episodic carbonate precipitation in the CM chondrite ALH 84049: An ion microprobe analysis of O and C isotopes

    NASA Astrophysics Data System (ADS)

    Tyra, Mark; Brearley, Adrian; Guan, Yunbin

    2016-02-01

    We have determined the O and C isotope compositions of dolomite grains and the C isotope compositions of calcite grains in the highly altered CM1 chondrite, ALH 84049, using Secondary Ion Mass Spectrometry (SIMS). Chemically-zoned dolomite constitutes 0.8 volume percent (vol%) of the sample and calcite 0.9 vol%. Thirteen separate dolomite grains have δ13C values that range from 37 to 60 (±2) ‰, δ18O values from 25 to 32 (±3) ‰, and δ17O values from 10 to 16 (±3) ‰ (VSMOW). Intragrain δ13C values in dolomite vary up to 10‰. The δ13C values of three calcite grains are distinct from those of dolomite and range from 10 to 13 (±2) ‰ (PDB). Calcite and dolomite appear to record different precipitation episodes. Carbon isotope values of both dolomite and calcite in this single sample encompass much of the reported range for CM chondrites; our results imply that bulk carbonate C and O isotope analyses may oversimplify the history of carbonate precipitation. Multiple generations of carbonates with variable isotope compositions exist in ALH 84049 and, perhaps, in many CM chondrites. This work shows that one should exercise caution when using a clumped isotope approach to determine the original temperature and the isotopic compositions of water for CM chondrite carbonates. Less altered CM meteorites with more-homogeneous C isotope compositions, however, may be suitable for bulk-carbonate analyses, but detailed carbonate petrologic and isotopic characterization of individual samples is advised.

  7. Spatial interpolation of hourly precipitation and dew point temperature for the identification of precipitation phase and hydrologic response in a mountainous catchment

    NASA Astrophysics Data System (ADS)

    Garen, D. C.; Kahl, A.; Marks, D. G.; Winstral, A. H.

    2012-12-01

    In mountainous catchments, it is well known that meteorological inputs, such as precipitation, air temperature, humidity, etc. vary greatly with elevation, spatial location, and time. Understanding and monitoring catchment inputs is necessary in characterizing and predicting hydrologic response to these inputs. This is true all of the time, but it is the most dramatically critical during large storms, when the input to the stream system due to rain and snowmelt creates the potential for flooding. Besides such crisis events, however, proper estimation of catchment inputs and their spatial distribution is also needed in more prosaic but no less important water and related resource management activities. The first objective of this study is to apply a geostatistical spatial interpolation technique (elevationally detrended kriging) to precipitation and dew point temperature on an hourly basis and explore its characteristics, accuracy, and other issues. The second objective is to use these spatial fields to determine precipitation phase (rain or snow) during a large, dynamic winter storm. The catchment studied is the data-rich Reynolds Creek Experimental Watershed near Boise, Idaho. As part of this analysis, precipitation-elevation lapse rates are examined for spatial and temporal consistency. A clear dependence of lapse rate on precipitation amount exists. Certain stations, however, are outliers from these relationships, showing that significant local effects can be present and raising the question of whether such stations should be used for spatial interpolation. Experiments with selecting subsets of stations demonstrate the importance of elevation range and spatial placement on the interpolated fields. Hourly spatial fields of precipitation and dew point temperature are used to distinguish precipitation phase during a large rain-on-snow storm in December 2005. This application demonstrates the feasibility of producing hourly spatial fields and the importance of doing

  8. A Study of the Microbial Spatial Heterogeneity of Bahamian Thrombolites Using Molecular, Biochemical, and Stable Isotope Analyses

    NASA Astrophysics Data System (ADS)

    Louyakis, Artemis S.; Mobberley, Jennifer M.; Vitek, Brooke E.; Visscher, Pieter T.; Hagan, Paul D.; Reid, R. Pamela; Kozdon, Reinhard; Orland, Ian J.; Valley, John W.; Planavsky, Noah J.; Casaburi, Giorgio; Foster, Jamie S.

    2017-05-01

    Thrombolites are buildups of carbonate that exhibit a clotted internal structure formed through the interactions of microbial mats and their environment. Despite recent advances, we are only beginning to understand the microbial and molecular processes associated with their formation. In this study, a spatial profile of the microbial and metabolic diversity of thrombolite-forming mats of Highborne Cay, The Bahamas, was generated by using 16S rRNA gene sequencing and predictive metagenomic analyses. These molecular-based approaches were complemented with microelectrode profiling and in situ stable isotope analysis to examine the dominant taxa and metabolic activities within the thrombolite-forming communities. Analyses revealed three distinctive zones within the thrombolite-forming mats that exhibited stratified populations of bacteria and archaea. Predictive metagenomics also revealed vertical profiles of metabolic capabilities, such as photosynthesis and carboxylic and fatty acid synthesis within the mats that had not been previously observed. The carbonate precipitates within the thrombolite-forming mats exhibited isotopic geochemical signatures suggesting that the precipitation within the Bahamian thrombolites is photosynthetically induced. Together, this study provides the first look at the spatial organization of the microbial populations within Bahamian thrombolites and enables the distribution of microbes to be correlated with their activities within modern thrombolite systems.

  9. Use of precipitation and groundwater isotopes to interpret regional hydrology on a tropical volcanic island: Kilauea volcano area, Hawaii

    USGS Publications Warehouse

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

    1996-01-01

    Isotope tracer methods were used to determine flow paths, recharge areas, and relative age for groundwater in the Kilauea volcano area of the Island of Hawaii. A network of up to 66 precipitation collectors was emplaced in the study area and sampled twice yearly for a 3-year period. 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 precipitation isotopes are controlled more by the frequency of storms than by seasonal temperature fluctuations. Results from this study suggest that (1) sampling network design must take into account areal variations in rainfall patterns on islands and in continental coastal areas and (2) isotope/elevation gradients on other tropical islands may be predictable on the basis of similar climatology. Groundwater was sampled yearly in coastal springs, wells, and a few high-elevation springs. Areal contrasts in groundwater stable isotopes and tritium indicate that the volcanic rift zones compartmentalize the regional groundwater system, isolating the groundwater south of Kilauea's summit and rift zones. Part of the Southwest Rift gone appears to act as a conduit for water from higher elevation, but there is no evidence for downrift flow in the springs and shallow wells sampled in the lower East Rift Zone.

  10. Improving High-resolution Spatial Estimates of Precipitation in the Equatorial Americas

    NASA Astrophysics Data System (ADS)

    Verdin, A.; Rajagopalan, B.; Funk, C. C.

    2013-12-01

    Drought and flood management practices require accurate estimates of precipitation in space and time. However, data is sparse in regions with complicated terrain (such as the Equatorial Americas), often in valleys (where people farm), and of poor quality. Consequently, extreme precipitation events are poorly represented. Satellite-derived rainfall data is an attractive alternative in such regions and is being widely used, though it too suffers from problems such as underestimation of extreme events (due to its dependency on retrieval algorithms) and the indirect relationship between satellite radiation observations and precipitation intensities. Thus, it seems appropriate to blend satellite-derived rainfall data of extensive spatial coverage with rain gauge data in order to provide a more robust estimate of precipitation. To this end, in this research we offer three techniques to blend rain gauge data and the Climate Hazards group InfraRed Precipitation (CHIRP) satellite-derived precipitation estimate for Central America and Colombia. In the first two methods, the gauge data is assigned to the closest CHIRP grid point, where the error is defined as r = Yobs - Ysat. The spatial structure of r is then modeled using physiographic information (Easting, Northing, and Elevation) by two methods (i) a traditional Cokriging approach whose variogram is calculated in Euclidean space and (ii) a nonparametric method based on local polynomial functional estimation. The models are used to estimate r at all grid points, which is then added to the CHIRP, thus creating an improved satellite estimate. We demonstrate these methods by applying them to pentadal and monthly total precipitation fields during 2009. The models' predictive abilities and their ability to capture extremes are investigated. These blending methods significantly improve upon the satellite-derived estimates and are also competitive in their ability to capture extreme precipitation. The above methods assume

  11. Spatial and temporal patterns of precipitation and stream flow variations in Tigris-Euphrates river basin.

    PubMed

    Daggupati, Prasad; Srinivasan, Raghavan; Ahmadi, Mehdi; Verma, Deepa

    2017-01-01

    Tigris and Euphrates river basin (TERB) is one of the largest river basins in the Middle East, and the precipitation (in the form of snowfall) is a major source of streamflow. This study investigates the spatial and temporal variability of precipitation and streamflow in TERB to better understand the hydroclimatic variables and how they varied over time. The precipitation shows a decreasing trend with 1980s being wetter and 2000s being drier. A total of 55 and 40% reduction in high flows in Tigris and Euphrates rivers at T20 and E3 was seen in post-reservoir period. A lag time of 3 to 4 and 5 to 6 months was estimated between peak snowfall and runoff time periods. Decreasing precipitation and streamflow along with several planned dams could hamper the sustainability of several Mesopotamian marshlands that completely depend on the water from the Tigris and Euphrates rivers.

  12. Effects of nitrate and water on the oxygen isotopic analysis of barium sulfate precipitated from water samples

    USGS Publications Warehouse

    Hannon, J.E.; Böhlke, J.K.; Mroczkowski, S.J.

    2008-01-01

    BaSO4 precipitated from mixed salt solutions by common techniques for SO42- isotopic analysis may contain quantities of H2O and NO3- that introduce errors in O isotope measurements. Experiments with synthetic solutions indicate that ??18O values of CO produced by decomposition of precipitated BaSO4 in a carbon reactor may be either too low or too high, depending on the relative concentrations of SO42- and NO3- and the ??18O values of the H2O, NO3-, and SO42-. Typical ??18O errors are of the order of 0.5 to 1??? in many sample types, and can be larger in samples containing atmospheric NO 3-, which can cause similar errors in ?? 17O and ??17O. These errors can be reduced by (1) ion chromatographic separation of SO42- from NO 3-, (2) increasing the salinity of the solutions before precipitating BaSO4 to minimize incorporation of H2O, (3) heating BaSO4 under vacuum to remove H2O, (4) preparing isotopic reference materials as aqueous samples to mimic the conditions of the samples, and (5) adjusting measured ??18O values based on amounts and isotopic compositions of coexisting H2O and NO 3-. These procedures are demonstrated for SO 42- isotopic reference materials, synthetic solutions with isotopically known reagents, atmospheric deposition from Shenandoah National Park, Virginia, USA, and sulfate salt deposits from the Atacama Desert, Chile, and Mojave Desert, California, USA. These results have implications for the calibration and use of O isotope data in studies of SO42- sources and reaction mechanisms.

  13. Effects of nitrate and water on the oxygen isotopic analysis of barium sulfate precipitated from water samples.

    PubMed

    Hannon, Janet E; Böhlke, John Karl; Mroczkowski, Stanley J

    2008-12-01

    BaSO(4) precipitated from mixed salt solutions by common techniques for SO(4) (2-) isotopic analysis may contain quantities of H(2)O and NO(3) (-) that introduce errors in O isotope measurements. Experiments with synthetic solutions indicate that delta(18)O values of CO produced by decomposition of precipitated BaSO(4) in a carbon reactor may be either too low or too high, depending on the relative concentrations of SO(4) (2-) and NO(3) (-) and the delta(18)O values of the H(2)O, NO(3) (-), and SO(4) (2-). Typical delta(18)O errors are of the order of 0.5 to 1 per thousand in many sample types, and can be larger in samples containing atmospheric NO(3) (-), which can cause similar errors in delta(17)O and Delta(17)O. These errors can be reduced by (1) ion chromatographic separation of SO(4) (2-) from NO(3) (-), (2) increasing the salinity of the solutions before precipitating BaSO(4) to minimize incorporation of H(2)O, (3) heating BaSO(4) under vacuum to remove H(2)O, (4) preparing isotopic reference materials as aqueous samples to mimic the conditions of the samples, and (5) adjusting measured delta(18)O values based on amounts and isotopic compositions of coexisting H(2)O and NO(3) (-). These procedures are demonstrated for SO(4) (2-) isotopic reference materials, synthetic solutions with isotopically known reagents, atmospheric deposition from Shenandoah National Park, Virginia, USA, and sulfate salt deposits from the Atacama Desert, Chile, and Mojave Desert, California, USA. These results have implications for the calibration and use of O isotope data in studies of SO(4) (2-) sources and reaction mechanisms.

  14. Effect of precipitation spatial distribution uncertainty on the uncertainty bounds of a snowmelt runoff model output

    NASA Astrophysics Data System (ADS)

    Jacquin, A. P.

    2012-04-01

    This study analyses the effect of precipitation spatial distribution uncertainty on the uncertainty bounds of a snowmelt runoff model's discharge estimates. Prediction uncertainty bounds are derived using the Generalized Likelihood Uncertainty Estimation (GLUE) methodology. The model analysed is a conceptual watershed model operating at a monthly time step. The model divides the catchment into five elevation zones, where the fifth zone corresponds to the catchment glaciers. Precipitation amounts at each elevation zone i are estimated as the product between observed precipitation (at a single station within the catchment) and a precipitation factor FPi. Thus, these factors provide a simplified representation of the spatial variation of precipitation, specifically the shape of the functional relationship between precipitation and height. In the absence of information about appropriate values of the precipitation factors FPi, these are estimated through standard calibration procedures. The catchment case study is Aconcagua River at Chacabuquito, located in the Andean region of Central Chile. Monte Carlo samples of the model output are obtained by randomly varying the model parameters within their feasible ranges. In the first experiment, the precipitation factors FPi are considered unknown and thus included in the sampling process. The total number of unknown parameters in this case is 16. In the second experiment, precipitation factors FPi are estimated a priori, by means of a long term water balance between observed discharge at the catchment outlet, evapotranspiration estimates and observed precipitation. In this case, the number of unknown parameters reduces to 11. The feasible ranges assigned to the precipitation factors in the first experiment are slightly wider than the range of fixed precipitation factors used in the second experiment. The mean squared error of the Box-Cox transformed discharge during the calibration period is used for the evaluation of the

  15. Effects of brine chemistry and polymorphism on clumped isotopes revealed by laboratory precipitation of mono- and multiphase calcium carbonates

    NASA Astrophysics Data System (ADS)

    Kluge, Tobias; John, Cédric M.

    2015-07-01

    Carbonate clumped isotopes are applied to an increasing number of geological archives to address a wide range of Earth science questions. However, the effect of changes in salinity on the carbonate clumped isotope technique has not been investigated experimentally yet. In particular, evaporated sea water and diagenetic fluids differ substantially from solutions used to calibrate the clumped isotope thermometer as they exhibit high ionic concentrations of e.g., Na+, Ca2+, Mg2+, and Cl-. High ionic concentrations are known to have an impact on δ18O values, and could potentially impact the successful application of clumped isotopes to the reconstruction of diagenetic processes, including precipitation temperatures and the origin of the diagenetic fluid. In order to address the potential influence of salt ions on the clumped isotope Δ47 value we precipitated CaCO3 minerals (calcite, aragonite and vaterite), hydromagnesite and mixtures of these minerals in the laboratory from solutions containing different salt ions (Na+, Ca2+, Mg2+, Cl-) at various concentrations and temperatures. The precipitation of some mineralogies was restricted to solutions with specific ionic concentrations, limiting direct comparability. NaCl-rich solutions mostly led to vaterite formation. In control experiments CaCO3 minerals (calcite and aragonite) were precipitated from a CaCO3 supersaturated solution without addition of any other ions. Our results show that calcium carbonates precipitated from high NaCl concentrations yield Δ47 values identical to our NaCl-free control solution. Although addition of Mg led to the formation of hydromagnesite, it also follows the same Δ47-T calibration as calcite. In contrast, Δ47 values increase together with increased CaCl2 concentrations, and deviate by a few 0.01‰ from expected equilibrium values. Overall, clumped isotope values of CaCO3 minerals precipitated between 23 °C and 91 °C (with and without NaCl addition) follow a line with a slope

  16. Spatial distribution and temporal variability of stable water isotopes in a large and shallow lake.

    PubMed

    Xiao, Wei; Wen, Xuefa; Wang, Wei; Xiao, Qitao; Xu, Jingzheng; Cao, Chang; Xu, Jiaping; Hu, Cheng; Shen, Jing; Liu, Shoudong; Lee, Xuhui

    2016-01-01

    Stable isotopic compositions of lake water provide additional information on hydrological, meteorological and paleoclimate processes. In this study, lake water isotopic compositions were measured for more than three years in Lake Taihu, a large and shallow lake in southern China, to investigate the isotopic spatial and seasonal variations. The results indicated that (1) the whole-lake mean δ(2)H and δ(18)O values of the lake water varied seasonally from -48.4 ± 5.8 to -25.1 ± 3.2 ‰ and from -6.5 ± 0.9 to -3.5 ± 0.8 ‰, respectively, (2) the spatial pattern of the lake water isotopic compositions was controlled by the direction of water flow and not by local evaporation rate, and (3) using a one-site isotopic measurement to represent the whole-lake mean may result in unreasonable estimates of the isotopic composition of lake evaporation and the lake water residence time in poorly mixed lakes. The original data, documented here as an online supplement, provides a good reference for testing sensitivity of lake water budget to various isotopic sampling strategies. We propose that detailed spatial measurement of lake water isotopic compositions provides a good proxy for water movement and pollutant and alga transports, especially over big lakes.

  17. Multi-proxy reconstructions of South American precipitation from oxygen isotopes and growth rings in tropical trees

    NASA Astrophysics Data System (ADS)

    Ballantyne, A. P.; Baker, P.; Chambers, J.; Villalba, R.

    2004-12-01

    Most of our knowledge about climate variability is restricted to the high latitudes of the Northern Hemisphere. Although the tropics constitute 40% of the Earth's surface, very little is known about temperature and precipitation variability, even during the last century. By analyzing the growth and isotopic variability of tropical trees, we may resolve intra-annual fluctuations in precipitation. Certain taxa of tropical trees are known to possess annual growth rings and some taxa exceed 1,000 years old. Recent progress in tropical dendrochronology, has established a strong relationship between growth and precipitation amount, especially during the growth season. The relationship between \\delta18O in precipitation and precipitation amount has been well established; and is moderately significant for certain regions of the neotropics (r= -65). Although much of the variability in the \\delta18O of precipitation has been ascribed to changes in sea surface temperatures resulting from El Niño events, longer periods (12 yr.) of variability in \\delta18O remain unexplained. Here we combine measures of tree ring growth and \\delta18O in the cellulose of several tropical trees to capture the inter-annual variability in precipitation. Samples from the Andean genus Polylepis were cross-dated and analyzed for \\delta18O. The resulting 146-year time series reveals pronounced inter-annual variability in \\delta18O, as well as low frequency variability similar to the \\delta18O. An appreciable amount of regional precipitation is described by the ring-width and the high pass-filtered \\delta18O data. To validate the relationship between growth and cellulose \\delta18O, we also analyzed samples from Dipterix spp. and Tachigali spp. from the Amazon. In both taxa growth maxima and cellulose \\delta18O minima coincided during the rainy season (DJF). The analysis of \\delta13C, another isotope known to be fractionated under arid conditions may increase our ability to reconstruct

  18. Detectability of change in winter precipitation within mountain landscapes: Spatial patterns and uncertainty

    NASA Astrophysics Data System (ADS)

    Silverman, N. L.; Maneta, M. P.

    2016-06-01

    Detecting long-term change in seasonal precipitation using ground observations is dependent on the representativity of the point measurement to the surrounding landscape. In mountainous regions, representativity can be poor and lead to large uncertainties in precipitation estimates at high elevations or in areas where observations are sparse. If the uncertainty in the estimate is large compared to the long-term shifts in precipitation, then the change will likely go undetected. In this analysis, we examine the minimum detectable change across mountainous terrain in western Montana, USA. We ask the question: What is the minimum amount of change that is necessary to be detected using our best estimates of precipitation in complex terrain? We evaluate the spatial uncertainty in the precipitation estimates by conditioning historic regional climate model simulations to ground observations using Bayesian inference. By using this uncertainty as a null hypothesis, we test for detectability across the study region. To provide context for the detectability calculations, we look at a range of future scenarios from the Coupled Model Intercomparison Project 5 (CMIP5) multimodel ensemble downscaled to 4 km resolution using the MACAv2-METDATA data set. When using the ensemble averages we find that approximately 65% of the significant increases in winter precipitation go undetected at midelevations. At high elevation, approximately 75% of significant increases in winter precipitation are undetectable. Areas where change can be detected are largely controlled by topographic features. Elevation and aspect are key characteristics that determine whether or not changes in winter precipitation can be detected. Furthermore, we find that undetected increases in winter precipitation at high elevation will likely remain as snow under climate change scenarios. Therefore, there is potential for these areas to offset snowpack loss at lower elevations and confound the effects of climate change

  19. Simulating speleothem growth in the laboratory: Determination of stable isotope fractionation factors during precipitation of speleothem calcite

    NASA Astrophysics Data System (ADS)

    Hansen, Maximilian; Schöne, Bernd R.; Spötl, Christoph; Scholz, Denis

    2016-04-01

    We present laboratory experiments aiming to understand the processes affecting the δ13C and δ18O values of speleothems during precipitation of calcite from a thin layer of solution. In particular, we determined the precipitation rates and the isotope fractionation factors in dependence of several parameters, such as temperature, cave pCO2 and supersaturation with respect to calcite. The experiments were performed in a climate box in order to simulate cave conditions and to control them during the experiments[1]. In the experiments, a thin film of a CaCO3-CO2-H2O-solution supersaturated with respect to calcite flew down an inclined marble surface or a sand-blasted borosilicate glass plate, and the drip water was sampled at different distances and, thus, residence times on the plate. Subsequently, pH, electrical conductivity and the δ13C and δ18O values of the dissolved inorganic carbon (DIC) as well as the precipitated CaCO3 were determined. In addition, we determined the stable isotope values of the drip water and the atmosphere inside the box during the experiments. This enabled the identification of carbon and oxygen isotope fractionation factors between all carbonate species. The experiments were conducted at 10, 20 and 30 ° C, a pCO2 of 1000 and 3000 ppmV and with a Ca2+ concentration of 2 and 5 mmol/l. We observed an exponential decay of conductivity with increasing distance of flow documenting progressive precipitation of calcite confirming previous observations[2]. The corresponding time constants of precipitation range from 180 to 660 s. Both the δ13C and δ18O values show a progressive increase along the flow path. The enrichment of the δ13C values seems to be strongly influenced by kinetic isotope fractionation, whereas the δ18O values are in the range of isotopic equilibrium. The fractionation between the precipitated CaCO3 and DIC is between -1 and - 6.5 ‰ for carbon isotopes (13ɛ) and between -1.5 and -3 ‰ for oxygen isotopes (18ɛ). The

  20. Air temperature and precipitation spatial evaluation in Slovakia using the regularized splain with tension method

    NASA Astrophysics Data System (ADS)

    Mikulová, K.; Pecho, J.; Šâstný, P.; Faško, P.; Šiška, B.

    2009-09-01

    Over the last few years improvement of various GIS applications that involve spatial processing of climatological and meteorological data has been quite noticeable. This upsurge of interest is related directly to the fall in price of `commercial off-the-shelf' GIS products together with large advances in computer processing ability. GIS methods allow the detailed analysis of spatial patterns of various atmospheric parameters, providing an in depth look into the regularities and variability of weather and climate over time and space. Many climatic parameters, such as air temperature, precipitation and snow cover as well, are strongly dependent on geographical factors such as topography, land use and vegetation height. The paper presented here deals with spatial evaluation of the air temperature mean and mean precipitation totals within normal period 1961-1990 using GIS 3D interpolation methods. Through the homogenization process the utilized data sets were tested using the quality and quantity control procedures particularly concerning the filling and correction all data gaps and shifts recognized in the long time series within the period 1961-1990. Nevertheless, the network of climatological as well as rain gauge stations is quite dense in Slovakia it was needed to use additional supporting points (so-called "virtual stations") particularly in the mountainous regions during the pre-processing stage of spatial analysis. In the case of air temperature analysis the regional approach of statistical regression modeling was applied and available in-situ air temperature measurements were supported by the regularly distributed grid points with spatial resolution 10 × 10 km. In the contrast to the proceeding the precipitation data were advanced with irregular spatial network of "virtual stations". Supplementary data sets represented by grid and virtual points were evaluated using the regional regression function whereby the statistical relation between variables and

  1. The roles of convective entrainment in spatial distributions and temporal variations of precipitation over tropical oceans

    NASA Astrophysics Data System (ADS)

    Hirota, N.; Takayabu, Y. N.; Watanabe, M.; Kimoto, M.; Chikira, M.

    2013-12-01

    This study shows that a proper treatment of convective entrainment is essential in determining spatial distributions and temporal variations of precipitation by numerical experiments. They have performed and compared four experiments with different entrainment characteristics: a control (Ctl), no entrainment (NoEnt), original Arakawa Schubert (AS), and AS with simple empirical suppression of convection (ASRH). The fractional entrainment rate of AS and ASRH are constant for each cloud type and are very small near cloud base compared to Ctl, in which half of buoyancy-generated energy is consumed by the entrainment. Ctl well reproduces the spatial and temporal variations, whereas NoEnt and AS, which are very similar to each other, significantly underestimated the variations with the so-called the double ITCZ problem. The enhanced variations in Ctl are due to the larger entrainment that strengthens the coupling of convection and free tropospheric humidity. Time variations are also more realistic in Ctl; mid-height convection moistens mid-troposphere and large precipitation events occur after sufficient moisture is available. In contrast, deep convection is more frequent but with smaller precipitation amount in NoEnt and AS. ASRH shows smaller spatial but excessive temporal variations suggesting that its empirical suppression condition is too simple and a more sophisticated formulation is required for more realistic precipitation variations. This study was supported by the Ministry of Education, Culture, Sports, Science and Technology (GRENE), and by the Ministry of the Environment (2A-1201), Japan.

  2. Simulation of stable isotopic pools and fluxes by a land-surface scheme forced with observed isotopic ratios in precipitation and atmospheric water vapour.

    NASA Astrophysics Data System (ADS)

    Henderson-Sellers, A.; Griffith, D.; Irannejad, P.; Williams, A.; Stone, D.

    2004-12-01

    Stable isotopes provide independent tools for evaluating key components of the hydrological and carbon cycles as simulated by land-surface schemes (LSS). The Project for Intercomparison of Land-surface Parameterisation Schemes (PILPS http://www.pilps.mq.edu.au) is initiating a new type of experiment (IPILPS) to assess the ability of LSSs to reproduce isotopic components of water and mass (carbon) budgets. The project aims to intercompare LSS simulations of diurnal and annual cycles of isotopic pools and fluxes, and to evaluate the performance of isotope-enabled LSSs under varying environmental conditions. The need for evaluation data is driving a new experimental effort concentrating on the measurement of stable water isotopes (SWI), in precipitation, atmospheric and canopy water vapour, soil water and leaf/stem water, on annual and diurnal time scales at three sites in the GEWEX CSE Amazon, Murray-Darling and Baltic Sea basins. We present diurnal and annual cycles of stable isotopes in the ecosystem as simulated by an isotope enabled LSS (ISOLSM)1 over an agricultural pasture in Wagga Wagga (SE Australia). Climatological values of SWI in precipitation and water vapour, as well as continuous in situ D/H ratios of atmospheric water vapour obtained during a three-week field campaign, are used to force the LSS. The D/H ratio was measured using a fully automated and mobile Fourier Transform Infrared (FTIR)2 spectrometer. The sensitivity of simulated isotopes (in soil water, plants and canopy air space, as well as isotopic exchanges between the land surface and the atmosphere) to the atmospheric forcing is analysed. The results highlight the importance of intensive field campaigns for measuring SWI in the environment as both forcing and evaluation data for land surface simulations. 1. A. Henderson-Sellers et al., 2004, Using stable water isotopes to evaluate basin-scale simulations of surface water budgets, in press, J. Hydrometeorol. 2. D.W.T. Griffith et al., 2002

  3. The Effect of Moisture Source Temperature Fluctuations on Seasonal Patterns of Precipitation Isotopes within the United States.

    NASA Astrophysics Data System (ADS)

    Vachon, R. W.; White, J. W.; Welker, J.

    2005-12-01

    Numerous studies have highlighted significantly decreased slopes between water isotopes and surface temperatures in coastal regions. Similar patterns have been determined from seasonal data within the United States Network for Isotopes in Precipitation (USNIP) dataset. The causes for these findings are not obvious; but it is becoming increasingly clear that such isotopic signals are linked to climatological data other than surface temperatures, such as moisture source conditions. Seasonal fluctuations of moisture source temperatures can define the specific humidity within an air mass and thus adjust the amount of moisture wrung as it is transported to a given temperature. This dynamic can skew observed relationships between seasonal isotopes and surface temperatures. In this study, a number of theoretical experiments, using the Rayleigh Model, were conducted to examine how various seasonal source temperature amplitudes can modify seasonal isotope-temperature slopes. Realistic seasonal moisture source conditions were then applied to the Rayleigh Model to explore the role of source conditions in driving the observed patterns of isotope-temperature slopes in the US. It is concluded that moisture source temperatures from geographically stationary locations within the Atlantic Ocean, Pacific Ocean and Gulf of Mexico, would contribute significantly to observed isotope-temperature slopes, however do not explain the patterns completely. A more complete explanation of the patterns could come from the geographic migration of moisture sources, but wind vector maps leave this problem unresolved. Alternatively, a seasonally fluctuating relationship between surface temperatures and the average height of condensation could bring resolution to the inconsistencies.

  4. Fundamental limits to the accuracy of deuterium isotopes for identifying the spatial origin of migratory animals

    USGS Publications Warehouse

    Farmer, A.; Cade, B.S.; Torres-Dowdall, J.

    2008-01-01

    Deuterium isotope analyses have revolutionized the study of migratory connectivity because global gradients of deuterium in precipitation (??DP) are expressed on a continental scale. Several authors have constructed continental scale base maps of ??DP to provide a spatial reference for studying the movement patterns of migratory species and, although they are very useful, these maps present a static, 40-year average view of the landscape that ignores much underlying inter-annual variation. To more fully understand the consequences of this underlying variation, we analyzed the GNIP deuterium data, the source for all current ??DP maps, to estimate the minimum separation in ??DP (and latitude) necessary to conclude with a given level of confidence that distinct ??DP values represent different geographic sites. Extending analyses of ??DP successfully to deuterium in tissues of living organisms, e.g., feathers in migratory birds (??DF), is dependent on the existence of geographic separation of ??DP, where every geographic location has a distribution of values associated with temporal variability in ??DP. Analyses were conducted for three distinct geographic regions: North America, eastern North America (east of longitude 100??W), and Argentina. At the 80% confidence level, the minimum separation values were 12, 7, and 14?? of latitude (equivalent to 53, 31, and 32???) for North America, eastern North America, and Argentina, respectively. Hence, in eastern North America, for example, one may not be able to accurately assign individual samples to sites separated by less than about 7?? of latitude as the distributions of ??DP were not distinct at latitudes <7?? apart. Moreover, two samples that differ by less than 31??? cannot be confidently said to originate from different latitudes. These estimates of minimum separation for ??DP do not include other known sources of variation in feather deuterium (??D F) and hence are a first order approximation that may be useful, in

  5. A lab in the field: high-frequency analysis of water quality and stable isotopes in stream water and precipitation

    NASA Astrophysics Data System (ADS)

    von Freyberg, Jana; Studer, Bjørn; Kirchner, James W.

    2017-03-01

    High-frequency measurements of solutes and isotopes (18O and 2H) in rainfall and streamflow can shed important light on catchment flow pathways and travel times, but the workload and sample storage artifacts involved in collecting, transporting, and analyzing thousands of bottled samples severely constrain catchment studies in which conventional sampling methods are employed. However, recent developments towards more compact and robust analyzers have now made it possible to measure chemistry and water isotopes in the field at sub-hourly frequencies over extended periods. Here, we present laboratory and field tests of a membrane-vaporization continuous water sampler coupled to a cavity ring-down spectrometer for real-time measurements of δ18O and δ2H combined with a dual-channel ion chromatograph (IC) for the synchronous analysis of major cations and anions. The precision of the isotope analyzer was typically better than 0.03 ‰ for δ18O and 0.17 ‰ for δ2H in 10 min average readings taken at intervals of 30 min. Carryover effects were less than 1.2 % between isotopically contrasting water samples for 30 min sampling intervals, and instrument drift could be corrected through periodic analysis of secondary reference standards. The precision of the ion chromatograph was typically ˜ 0.1-1 ppm or better, with relative standard deviations of ˜ 1 % or better for most major ions in stream water, which is sufficient to detect subtle biogeochemical signals in catchment runoff. We installed the coupled isotope analyzer/IC system in an uninsulated hut next to a stream of a small catchment and analyzed stream water and precipitation samples every 30 min over 28 days. These high-frequency measurements facilitated a detailed comparison of event-water fractions via endmember mixing analysis with both chemical and isotope tracers. For two events with relatively dry antecedent moisture conditions, the event-water fractions were < 21 % based on isotope tracers but were

  6. Periodicity analysis of δ18O in precipitation over Central Europe: Time-frequency considerations of the isotopic 'temperature' effect

    NASA Astrophysics Data System (ADS)

    Salamalikis, V.; Argiriou, A. A.; Dotsika, E.

    2016-03-01

    In this paper the periodic patterns of the isotopic composition of precipitation (δ18O) for 22 stations located around Central Europe are investigated through sinusoidal models and wavelet analysis over a 23 years period (1980/01-2002/12). The seasonal distribution of δ18O follows the temporal variability of air temperature providing seasonal amplitudes ranging from 0.94‰ to 4.47‰; the monthly isotopic maximum is observed in July. The isotopic amplitude reflects the geographical dependencies of the isotopic composition of precipitation providing higher values when moving inland. In order to describe the dominant oscillation modes included in δ18O time series, the Morlet Continuous Wavelet Transform is evaluated. The main periodicity is represented at 12-months (annual periodicity) where the wavelet power is mainly concentrated. Stations (i.e. Cuxhaven, Trier, etc.) with limited seasonal isotopic effect provide sparse wavelet power areas at the annual periodicity mode explaining the fact that precipitation has a complex isotopic fingerprint that cannot be examined solely by the seasonality effect. Since temperature is the main contributor of the isotopic variability in mid-latitudes, the isotope-temperature effect is also investigated. The isotope-temperature slope ranges from 0.11‰/°C to 0.47‰/°C with steeper values observed at the southernmost stations of the study area. Bivariate wavelet analysis is applied in order to determine the correlation and the slope of the δ18O - temperature relationship over the time-frequency plane. High coherencies are detected at the annual periodicity mode. The time-frequency slope is calculated at the annual periodicity mode ranging from 0.45‰/°C to 0.83‰/°C with higher values at stations that show a more distinguishable seasonal isotopic behavior. Generally the slope fluctuates around a mean value but in certain cases (sites with low seasonal effect) abrupt slope changes are derived and the slope becomes

  7. Key drivers controlling stable isotope variations in daily precipitation of Costa Rica: Caribbean Sea versus Eastern Pacific Ocean moisture sources

    NASA Astrophysics Data System (ADS)

    Sánchez-Murillo, R.; Birkel, C.; Welsh, K.; Esquivel-Hernández, G.; Corrales-Salazar, J.; Boll, J.; Brooks, E.; Roupsard, O.; Sáenz-Rosales, O.; Katchan, I.; Arce-Mesén, R.; Soulsby, C.; Araguás-Araguás, L. J.

    2016-01-01

    Costa Rica is located on the Central American Isthmus, which receives moisture inputs directly from the Caribbean Sea and the Eastern Pacific Ocean. This location includes unique mountainous and lowland microclimates, but only limited knowledge exists about the impact of relief and regional atmospheric circulation patterns on precipitation origin, transport, and isotopic composition. Therefore, the main scope of this project is to identify the key drivers controlling stable isotope variations in daily-scale precipitation of Costa Rica. The monitoring sites comprise three strategic locations across Costa Rica: Heredia (Central Valley), Turrialba (Caribbean slope), and Caño Seco (South Pacific slope). Sporadic dry season rain is mostly related to isolated enriched events ranging from -5.8‰ to -0.9‰ δ18O. By mid-May, the Intertropical Convergence Zone reaches Costa Rica resulting in a notable depletion in isotope ratios (up to -18.5‰ δ18O). HYSPLIT air mass back trajectories indicate the strong influence on the origin and transport of precipitation of three main moisture transport mechanisms, the Caribbean Low Level Jet, the Colombian Low Level Jet, and localized convection events. Multiple linear regression models constructed based on Random Forests of surface meteorological information and atmospheric sounding profiles suggest that lifted condensation level and surface relative humidity are the main factors controlling isotopic variations. These findings diverge from the recognized 'amount effect' in monthly composite samples across the tropics. Understanding of stable isotope dynamics in tropical precipitation can be used to a) enhance groundwater modeling efforts in ungauged basins where scarcity of long-term monitoring data drastically limit current and future water resources management, b) improve the re-construction of paleoclimatic records in the Central American land bridge, c) calibrate and validate regional circulation models.

  8. Oxygen isotopes in tree rings are a good proxy for Amazon precipitation and El Nino-Southern Oscillation variability.

    PubMed

    Brienen, Roel J W; Helle, Gerd; Pons, Thijs L; Guyot, Jean-Loup; Gloor, Manuel

    2012-10-16

    We present a unique proxy for the reconstruction of variation in precipitation over the Amazon: oxygen isotope ratios in annual rings in tropical cedar (Cedrela odorata). A century-long record from northern Bolivia shows that tree rings preserve the signal of oxygen isotopes in precipitation during the wet season, with weaker influences of temperature and vapor pressure. Tree ring δ(18)O correlates strongly with δ(18)O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ(18)O showing that the signal is coherent over large areas. The signal correlates most strongly with basin-wide precipitation and Amazon river discharge. We attribute the strength of this (negative) correlation mainly to the cumulative rainout processes of oxygen isotopes (Rayleigh distillation) in air parcels during westward transport across the basin. We further find a clear signature of the El Niño-Southern Oscillation (ENSO) in the record, with strong ENSO influences over recent decades, but weaker influence from 1925 to 1975 indicating decadal scale variation in the controls on the hydrological cycle. The record exhibits a significant increase in δ(18)O over the 20th century consistent with increases in Andean δ(18)O ice core and lake records, which we tentatively attribute to increased water vapor transport into the basin. Taking these data together, our record reveals a fresh path to diagnose and improve our understanding of variation and trends of the hydrological cycle of the world's largest river catchment.

  9. How do Cloud Macrostructure and Weather Pattern Modulate the Removal of Ice Nucleating Particles and Stable Isotopes in Precipitation?

    NASA Astrophysics Data System (ADS)

    Creamean, J.; Martin, A.; Mix, H.

    2016-12-01

    Precipitation collected at the Earth's surface, while primarily comprised of the molecule H2O16, contains significant heterogeneous material that has recorded the history of the hydrometeors, from vapor to condensate to cloud particles to precipitation. The use of stable water isotopes as a way to quantitatively evaluate the efficient removal of INPshas received significant attention recently, with some authors proposing that the efficiency of removal of atmospheric water vapor and the temperature of INP activation in the same weather system are related. Here, we present detailed chemical analysis of individual insoluble precipitation residues and the stable isotope composition of water (δ18O and δD) in time-resolved precipitation collected in atmospheric rivers in Northern California during winter 2016. Using size-resolved drop freezing spectra, nano-particle tracking analysis, ion chromatography and single particle aerosol mass spectrometry in concert with synoptic meteorological analysis and profiles of S-band radar reflectivity, we examine the relationships between insoluble residues, their ice nucleating properties, stable isotopes, cloud macrostructure and synoptic weather patterns. In particular, we will address the role meteorology plays in modulating the preferential removal of ice nucleating particles during atmospheric rivers.

  10. Arctic and Tropical Influence on Extreme Precipitation Events, Atmospheric Rivers, and Associated Isotopic Values in the Western U.S.

    NASA Astrophysics Data System (ADS)

    McCabe-Glynn, S. E.; Johnson, K. R.; Zou, Y.; Welker, J. M.; Strong, C.; Rutz, J. J.; Yu, J. Y.; Yoshimura, K.; Sellars, S. L.; Payne, A. E.

    2014-12-01

    Extreme precipitation events along the U.S. West Coast can result in major damage and are projected by most climate models to increase in frequency and severity. One of the most prevalent extreme precipitation events that occurs along the west coast of North America are known as 'Atmospheric Rivers' (ARs), whereby extensive fluxes of water vapor are transported from the tropics and/or subtropics, delivering substantial precipitation and contributing to flooding when they encounter mountains. This region is particularly vulnerable to ARs, with 30-50% of annual precipitation in this region occurring from just a few AR events. Because of the tropical and/or subtropical origin of ARs, they can carry unique isotopic properties. Here we present the results of analysis of weekly precipitation data and accompanying isotopic values from Giant Forest, in Sequoia National Park, in the southwestern Sierra Nevada Mountains (36.57° N; 118.78° W; 1921m) from 2001 to 2011. To better characterize these events, we focused on the 10 weeks with the highest precipitation totals (all greater than 150 mm) during the study period. We show that nine of the top ten weeks contain documented 'AR' events and that 90% occurred during the negative phase of the Arctic Oscillation. A comparison of extreme precipitation events across the Western U.S. with several key climate indices demonstrate these events occur most frequently when the negative phase of the Arctic Oscillation is in sync with the negative phase of the El Niño Southern Oscillation (ENSO) and the negative or neutral Pacific North American (PNA) pattern. We also demonstrate that central or eastern Pacific location of ENSO sea surface temperature anomalies can further enhance predictive capabilities of the landfall location of extreme precipitation. Stable isotope results show that extreme precipitation events are characterized by highly variable δ18O (-7.20‰ to -19.27‰), however, we find that more negative δ18O values

  11. Isotopic composition of nitrate in sequential Hurricane Irene precipitation samples: Implications for changing NOx sources

    NASA Astrophysics Data System (ADS)

    Felix, J. David; Elliott, Emily M.; Avery, G. Brooks; Kieber, Robert J.; Mead, Ralph N.; Willey, Joan D.; Mullaugh, Katherine M.

    2015-04-01

    Previous studies have concentrated on adverse ecosystem effects resulting from nitrogen (N) loading from runoff and increased N2O emissions due to hurricane activity but little focus has been placed on N inputs delivered by hurricane precipitation. Understanding these N inputs during extreme rain events is increasingly important since global climate change may alter hurricane activity. In this study, ten sequential Hurricane Irene rain samples were analyzed for isotopic composition of nitrate (NO3-) to investigate NOx (=NO + NO2) sources contributing to NO3- deposited by a hurricane. The samples were divided into three groups (I, II, II) by k-means clustering using rain event back trajectories, δ15N-NO3- values, and NO3- concentrations. Chemical, physical and isotopic analyses, including δ15N- and δ18O-NO3-, anions, cations, H+, H2O2, DOC, acetaldehyde, ethanol and rainfall intensity, were then used to explore similarities in geographic origins and potential relationships with NOx and other emission sources. While it is possible that all samples had contributions from various NOx sources, group I samples had marine back trajectories and a mean δ15N-NO3- value (-0.7 ± 1.9‰) suggesting primarily lightning-sourced NOx contributions to NO3- deposition. As the hurricane made landfall, Group II samples transitioned to reflect more of a terrestrial signature with a higher mean δ15N-NO3- value (+11.0 ± 0.5‰) indicating NOx emission contributions from vehicles and power plants sources. As the hurricane continued to move inland, Group III δ15N-NO3- values (-5.5 and -5.7‰) reflect the potential mixing of biogenic soil NOx emissions with vehicle and power plant sources. Higher concentrations of ethanol, acetaldehyde, NH4+, and carbohydrates in Group III samples support the influence of biogenic sources. The isotopic composition of NO3- in hurricane rain can aid in discerning varying NOx sources contributing to nitrate concentrations in extreme rain events. This

  12. Stochastic modelling of spatially and temporally consistent daily precipitation time-series over complex topography

    NASA Astrophysics Data System (ADS)

    Keller, D. E.; Fischer, A. M.; Frei, C.; Liniger, M. A.; Appenzeller, C.; Knutti, R.

    2014-07-01

    Many climate impact assessments over topographically complex terrain require high-resolution precipitation time-series that have a spatio-temporal correlation structure consistent with observations. This consistency is essential for spatially distributed modelling of processes with non-linear responses to precipitation input (e.g. soil water and river runoff modelling). In this regard, weather generators (WGs) designed and calibrated for multiple sites are an appealing technique to stochastically simulate time-series that approximate the observed temporal and spatial dependencies. In this study, we present a stochastic multi-site precipitation generator and validate it over the hydrological catchment Thur in the Swiss Alps. The model consists of several Richardson-type WGs that are run with correlated random number streams reflecting the observed correlation structure among all possible station pairs. A first-order two-state Markov process simulates intermittence of daily precipitation, while precipitation amounts are simulated from a mixture model of two exponential distributions. The model is calibrated separately for each month over the time-period 1961-2011. The WG is skilful at individual sites in representing the annual cycle of the precipitation statistics, such as mean wet day frequency and intensity as well as monthly precipitation sums. It reproduces realistically the multi-day statistics such as the frequencies of dry and wet spell lengths and precipitation sums over consecutive wet days. Substantial added value is demonstrated in simulating daily areal precipitation sums in comparison to multiple WGs that lack the spatial dependency in the stochastic process: the multi-site WG is capable to capture about 95% of the observed variability in daily area sums, while the summed time-series from multiple single-site WGs only explains about 13%. Limitation of the WG have been detected in reproducing observed variability from year to year, a component that has

  13. A Two-year Record of Daily Rainfall Isotopes from Fiji: Implications for Reconstructing Precipitation from Speleothem δ18O

    NASA Astrophysics Data System (ADS)

    Brett, M.; Mattey, D.; Stephens, M.

    2015-12-01

    Oxygen isotopes in speleothem provide opportunities to construct precisely dated records of palaeoclimate variability, underpinned by an understanding of both the regional climate and local controls on isotopes in rainfall and groundwater. For tropical islands, a potential means to reconstruct past rainfall variability is to exploit the generally high correlation between rainfall amount and δ18O: the 'amount effect'. The GNIP program provides δ18O data at monthly resolution for several tropical Pacific islands but there are few data for precipitation isotopes at daily resolution, for investigating the amount effect over different timescales in a tropical maritime setting. Timescales are important since meteoric water feeding a speleothem has undergone storage and mixing in the aquifer system and understanding how the isotope amount effect is preserved in aquifer recharge has fundamental implications on the interpretation of speleothem δ18O in terms of palaeo-precipitation. The islands of Fiji host speleothem caves. Seasonal precipitation is related to the movement of the South Pacific Convergence Zone, and interannual variations in rainfall are coupled to ENSO behaviour. Individual rainfall events are stratiform or convective, with proximal moisture sources. We have daily resolution isotope data for rainfall collected at the University of the South Pacific in Suva, covering every rain event in 2012 and 2013. δ18O varies between -18‰ and +3‰ with the annual weighted averages at -7.6‰ and -6.8‰ respectively, while total recorded rainfall amount is similar in both years. We shall present analysis of our data compared with GNIP, meteorological data and back trajectory analyses to demonstrate the nature of the relationship between rainfall amount and isotopic signatures over this short timescale. Comparison with GNIP data for 2012-13 will shed light on the origin of the amount effect at monthly and seasonal timescales in convective, maritime, tropical

  14. 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

  15. Spatial and temporal variation of polychlorinated biphenyl (PCB) in precipitation in southern Sweden.

    PubMed

    Backe, Cecilia; Larsson, Per; Agrell, Cecilia

    2002-02-21

    Spatial and temporal variations in polychlorinated biphenyl (PCB) concentrations were studied in precipitation at 11 sampling-sites over a period of 1 year and compared with PCB concentrations in the air. The study was carried out in a region of southern Sweden approximately 11 000 km2 in area. The PCB concentration in precipitation ranged between 1.18 and 81.4 ng l(-1). Two of the sampling sites showed concentrations that were approximately 30 times higher than at the rest of the sites. The variation in concentration between sites may be explained by location as well as by differences in weather conditions and particle content in the air. Wind direction played an important role for PCB concentration in precipitation in coastal areas, while at the inland sites this variable seemed to have a minor influence. We found no seasonal trends in PCB concentration in precipitation or any dependence on air temperature. To examine the intensity of precipitation scavenging, the total washout ratios (Wt) were calculated. There was a large variation in Wt over time, and the highest ratios were observed at the two sites where PCB concentration in the air was high. Furthermore, high concentrations of PCB in precipitation correlated with a high-chlorinated pattern, as shown by principal component analysis. For most of the sites there was a significantly negative relationship between PCB concentration and rain volume.

  16. Spatially Resolved Genomic, Stable Isotopic, and Lipid Analyses of a Modern Freshwater Microbialite from Cuatro Ciénegas, Mexico

    PubMed Central

    Nitti, Anthony; Daniels, Camille A.; Siefert, Janet; Souza, Valeria; Hollander, David

    2012-01-01

    Abstract Microbialites are biologically mediated carbonate deposits found in diverse environments worldwide. To explore the organisms and processes involved in microbialite formation, this study integrated genomic, lipid, and both organic and inorganic stable isotopic analyses to examine five discrete depth horizons spanning the surface 25 mm of a modern freshwater microbialite from Cuatro Ciénegas, Mexico. Distinct bacterial communities and geochemical signatures were observed in each microbialite layer. Photoautotrophic organisms accounted for approximately 65% of the sequences in the surface community and produced biomass with distinctive lipid biomarker and isotopic (δ13C) signatures. This photoautotrophic biomass was efficiently degraded in the deeper layers by heterotrophic organisms, primarily sulfate-reducing proteobacteria. Two spatially distinct zones of carbonate precipitation were observed within the microbialite, with the first zone corresponding to the phototroph-dominated portion of the microbialite and the second zone associated with the presence of sulfate-reducing heterotrophs. The coupling of photoautotrophic production, heterotrophic decomposition, and remineralization of organic matter led to the incorporation of a characteristic biogenic signature into the inorganic CaCO3 matrix. Overall, spatially resolved multidisciplinary analyses of the microbialite enabled correlations to be made between the distribution of specific organisms, precipitation of carbonate, and preservation of unique lipid and isotopic geochemical signatures. These findings are critical for understanding the formation of modern microbialites and have implications for the interpretation of ancient microbialite records. Key Words: Microbial ecology—Microbe-mineral interactions—Microbial mats—Stromatolites—Genomics. Astrobiology 12, 685–698. PMID:22882001

  17. Mineral dissolution and precipitation in carbonate dominated terranes assessed using Mg isotopes

    NASA Astrophysics Data System (ADS)

    Tipper, E.; Calmels, D.; Gaillardet, J.; Galy, A.

    2013-12-01

    Carbonate weathering by carbonic acid consumes atmospheric CO2 during mineral dissolution, fixing it as aqueous bicarbonate over millennial time-scales. Ocean acidification has increased the solubility of CO2 in seawater by changing the balance of pH to alkalinity (the oceanic reservoir of carbon). This has lengthened the time-scale for CO2 sequestration by carbonate weathering to tens of thousands of years. At a global scale, the net consumption of CO2 is at least equal to that from silicate weathering, but there is far less work on carbonate weathering compared to silicate weathering because it has generally been assumed to be CO2 neutral on geological time-scales. Carbonate rocks are more readily dissolved than silicate rocks, meaning that their dissolution will likely respond much more rapidly to global environmental change when compared with the dissolution of silicate minerals. Although far less concentrated than Ca in many carbonates, Mg substitutes for Ca and is more concentrated than any other metal ion. Tracing the behavior of Mg in river waters, using Mg stable isotopes (26Mg/24Mg ratio expressed as delta26Mg in per mil units) is therefore a novel way to understand the complex series of dissolution/precipitation reactions that govern solute concentrations of Ca and Mg, and hence CO2 transfer by carbonate weathering. We present new Mg isotope data on a series of river and spring waters from the Jura mountains in North-East France. The stratigraphic column is relatively uniform throughout the Jura mountains and is dominated by limestones. As the limestone of the Jura Mountains were deposited in high-energy shallow water environments (shore line, lagoon and coral reefs), they are usually clay and organic poor. The delta26Mg of the local rocks is very constant at circa -4permil. The delta26Mg of the river waters is also fairly constant, but offset from the rock at -2.5permil. This is an intriguing observation because the dissolution of limestones is expected

  18. Temporal and spatial variations of precipitation in the Jinsha River basin during 1961-2010

    NASA Astrophysics Data System (ADS)

    Zeng, X.; Zhao, N.; Sun, H.; Ye, L.; Zhai, J.

    2015-05-01

    Knowing the variations of precipitation at the basin scale is very important to study the impacts of climate change on water resources and hydrological processes. To achieve the temporal and spatial variations of precipitation on long time scales and some extreme indicators in the Jinsha River basin, some typical precipitation indices were analysed based on daily precipitation data for 1961-2010 for the research area. The results showed that AP had a certain increasing tendency without passing the significance test, while AP in the lower reach of the basin decreased slightly. PFS had no obvious changes, while MP through a year (except rainfall in September and December) had a slight increasing tendency. In addition, AP and PFS showed obvious spatial differences, and the higher rainfall area was located in the lower basin especially in the Hengduan Mountain area. LRD and MRD increased slightly in the upper and middle regions, while they decreased slightly in the lower basin. HRD increased over most of the whole basin, but it had a decreasing tendency in the headwater region and around Dege station but did not pass the significance test. DD and CDD in one year showed similar spatial change patterns and had an obvious decreasing tendency in the upper and middle basin, while they had an obvious increasing tendency in the lower basin. CWD almost decreased over the whole basin, and decreased significantly in a small part of the lower basin. The temporal changes of the typical precipitation indices may confirm the possible increasing tendency for occurrence of drier climate and even drought events in the downstream of Jinsha River basin.

  19. Continuous, high-resolution spatial mapping of water isotopes: improving tools for quantifying local evaporation and residence times

    NASA Astrophysics Data System (ADS)

    Dennis, Kate J.; Carter, Jeffrey A.; Winkler, Renato; Downing, Brian; Kendall, Carol; Bergamaschi, Brian

    2015-04-01

    Stable isotopes of water (d2H, d18O) are unique tracers of many hydrological processes including evaporation, precipitation, reservoir mixing and residence time. Historically, discrete water samples have been collected and analyzed via either Isotope Ratio Mass Spectrometry, or more recently laser-based spectroscopic methods, such as Cavity Ring-Down Spectroscopy (CRDS). However, the analysis of discrete samples precludes the ability to construct high resolution water isotope data sets through time and space. By coupling a recently developed front-end peripheral device (Continuous Water Sampler or CWS) to a CRDS analyzer (Picarro L2130-i), we continuously measured and spatially mapped water isotopes on a transect of the Sacramento River Delta following an extended period of drought. More than two-thousand five-second average d18O and d2H measurements were made aboard the R/V King (USGS) over a six-hour period. In addition to water isotopes, nitrate, chlorophyll, dissolved organic matter (DOM) fluorescence, and other water quality parameters were also measured continuously. As you travel northeast up the delta, surface waters become progressively more enriched in 18O and 2H, while nitrate decreased in concentration and chlorophyll and DOM increased. We utilize the spatially-mapped isotope data within a single transect to understand local evaporation and residence time by (i) utilizing the secondary parameter, d-excess, and (ii) using a simple mass balance model of water moving through the system (inflow, outflow and evaporation). Additional transects, to be conducted during the rainy season, should highlight how the Delta system evolves seasonally. In concert with other data previously collected from the Sacramento River Delta, we suggest the lower region represents a mixture of river waters derived from the Sierra Nevada Mountains and the more marine waters from the mouth of the San Francisco Bay. Moving NE up the Delta into shallow sloughs through flooded wetlands

  20. Spatial hydrochemical and isotopic variations within the alluvial aquifer of the Allier River (Massif Central, France)

    NASA Astrophysics Data System (ADS)

    Mohammed, N.; Celle-Jeanton, H.; Huneau, F.; Le Coustumer, P.; Lavastre, V.; Bertrand, G.

    2012-04-01

    Hydrodynamic, hydrochemical (major ions, traces, pharmaceuticals and pesticides), isotopic (oxygen, hydrogen and carbon stable isotopes) and biological investigations were conducted every two weeks, since December 2010, to assess groundwater quality in the unconfined shallow alluvial aquifer of the Allier River (main tributary of the Loire River). The aquifer is mainly composed of unconsolidated alluvial deposits produced by the erosion of local crystalline rocks, the aquifer overlies impervious Oligocene marls; the surrounding hills are constituted with Quaternary deposits (early and old alluvial deposits on both sides of river), Oligocene limestones, marls and sandstones and Miocene volcano-sedimentary formations (Peperites). The study area is located in the east of the city of Clermont-Ferrand (France) where groundwater resources are used mainly for water supplies and then play an important socio-economic role as it is the major source of drinking water for about 100 000 inhabitants. This study aims at determining the factors and processes controlling shallow groundwater quality and groundwater origin by using the hydrochemical and hydrodynamical data collected on 87 water samples (71 boreholes, 13 piezometers and 4 surface waters) during a first field campaign carried out from the 9th to the 14th of December 2010. The Cournon Meteoric Water Line was determined according to 30 weekly rainfall samples. The results of this study show that spatial variations of physico-chemical parameters do exist in the study area, and the groundwater chemical composition is characterized by different water types with the predominance of the Ca-HCO3 type. Ionic concentration increases in boreholes far from the Allier River due to the increase of residence time or by a mixing with groundwater coming from the hills. The ð2H and ð18O signature of groundwater and surface water indicate that most of the boreholes close to the river are recharged by the Allier River, while boreholes

  1. An assessment of the isotopic (2H/18O) integrity of water samples collected and stored by unattended precipitation totalizers

    NASA Astrophysics Data System (ADS)

    Terzer, Stefan; Wassenaar, Leonard I.; Douence, Cedric; Araguas-Araguas, Luis

    2016-04-01

    The IAEA-WMO Global Network of Isotopes in Precipitation (GNIP) provides worldwide δ18O and δ2H data for numerous hydrological and climatological studies. The traditional GNIP sample collection method relies on weather station operators to accumulate precipitation obtained from manual rain gauges. Over the past decades, widespread weather station automatization resulted in the increased use of unattended precipitation totalizers that accumulate and store the rainwater in the field for up to one month. Several low-tech measures were adopted to prevent in situ secondary evaporative isotopic enrichment (SEE) of totalized water samples (i.e. disequilibrium isotopic fractionation after precipitation is stored in the collection device). These include: (a) adding a 0.5-1 cm floating layer of paraffin oil to the totalizer bottle, (b) using an intake tube leading from the collection funnel and submerged to the bottom of the totalizer bottle, or (c) placing a table tennis ball in the funnel aiming to reduce evaporation of the collected water from the receiving bottle to the atmosphere. We assessed the isotopic integrity of stored rainwater samples for three totalizers under controlled settings: each aforementioned totalizer was filled with a 100 or 500 mL of isotopically known water and installed in the field with the intake funnels sheltered to prevent rainwater collection. Potential evapotranspiration (PET) was obtained from on-site meteorological recordings. Stored evaporative loss from each totalizer was evaluated on a monthly basis; gravimetrically and by analysing δ18O and δ2H of the stored water, for a period of 6 months and a cumulative PET of ˜500 mm. The gravimetric and isotope results revealed that for smaller water volumes (100 ml, corresponding to ca. 5 mm of monthly precipitation), negligible isotope enrichment (δ18O) was observed in the paraffin-oil based totalizer, whereas unacceptable evaporative isotope effects were observed for the ball

  2. Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: an hypothesis

    NASA Astrophysics Data System (ADS)

    Daley, T. J.; Mauquoy, D.; Chambers, F. M.; Street-Perrott, F. A.; Hughes, P. D. M.; Loader, N. J.; Roland, T. P.; van Bellen, S.; Garcia-Meneses, P.; Lewin, S.

    2012-09-01

    Ombrotrophic raised peatlands provide an ideal archive for integrating late Holocene records of variations in hydroclimate and the estimated stable isotope composition of precipitation with recent instrumental measurements. Modern measurements of mean monthly surface air temperature, precipitation, and δD and δ18O-values in precipitation from the late twentieth and early twenty-first centuries provide a short but invaluable record with which to investigate modern relationships between these variables, thereby enabling improved interpretation of the peatland palaeodata. Stable isotope data from two stations in the Global Network for Isotopes in Precipitation (GNIP) from southern South America (Punta Arenas, Chile and Ushuaia, Argentina) were analysed for the period 1982 to 2008 and compared with longer-term meteorological data from the same locations (1890 to present and 1931 to present, respectively). δD and δ18O-values in precipitation have exhibited quite different trends in response to local surface air temperature and precipitation amount. At Punta Arenas, there has been a marked increase in the seasonal difference between summer and winter δ18O-values. A decline in the deuterium excess of summer precipitation at this station was associated with a general increase in relative humidity at 1000 mb over the surface of the Southeast Pacific Ocean, believed to be the major vapour source for the local precipitation. At Ushuaia, a fall in δ18O-values was associated with an increase in the mean annual amount of precipitation. Both records are consistent with a southward retraction and increase in zonal wind speed of the austral westerly wind belt. These regional differences, observed in response to a known driver, should be detectable in peatland sites close to the GNIP stations. Currently, insufficient data with suitable temporal resolution are available to test for these regional differences over the last 3000 yr. Existing peatland palaeoclimate data from two

  3. Mass-dependent and mass-independent fractionation of mercury isotopes in precipitation from Guiyang, SW China

    NASA Astrophysics Data System (ADS)

    Wang, Zhuhong; Chen, Jiubin; Feng, Xinbin; Hintelmann, Holger; Yuan, Shengliu; Cai, Hongming; Huang, Qiang; Wang, Shuxiao; Wang, Fengyang

    2015-11-01

    The isotopic composition of mercury (Hg) is increasingly used to constrain the sources and pathways of this metal in the atmosphere. Though China has the highest Hg production, consumption and emission in the world, Hg isotope ratios are rarely reported for Chinese wet deposition. In this study, we examined, for the first time outside North America, both mass-dependent fractionation (MDF, expressed as δ202Hg) and mass-independent fractionation of odd (odd-MIF, Δ199Hg) and even (even-MIF, Δ200Hg) Hg isotopes in 15 precipitation samples collected from September 2012 to August 2013 in Guiyang (SW China). All samples displayed significant negative δ202Hg (-0.44 ∼ -4.27‰), positive Δ199Hg (+0.19 to +1.16‰) and slightly positive Δ200Hg (-0.01‰ to +0.20‰). Potential sources of Hg in precipitation were identified by coupling both MDF and MIF of Hg isotopes with a back-trajectory model. The results showed that local emission from coal-fired power plants and cement plants and western long-range transportation are two main contributing sources, while the contribution of Hg from south wind events would be very limited on an annual basis. The relatively lower Δ200Hg values in Guiyang precipitation may indicate a dilution effect by local sources and/or insignificant even-MIF in the tropopause contribution of this subtropical region. Our study demonstrates the usefulness of isotope fractionation, especially MIF for tracing sources and pathways of Hg in the atmosphere.

  4. Precipitation efficiency derived from isotope ratios in water vapor distinguishes dynamical and microphysical influences on subtropical atmospheric constituents

    NASA Astrophysics Data System (ADS)

    Bailey, A.; Nusbaumer, J.; Noone, D.

    2015-09-01

    With water vapor and clouds expected to effect significant feedbacks on climate, moisture transport through convective processes has important implications for future temperature change. The precipitation efficiency—the ratio of the rates at which precipitation and condensation form (e = P/C)—is useful for characterizing how much boundary layer moisture recycles through precipitation versus mixes into the free troposphere through cloud detrainment. Yet it is a difficult metric to constrain with traditional observational techniques. This analysis characterizes the precipitation efficiency of convection near the Big Island of Hawaii, USA, using a novel tracer: isotope ratios in water vapor. The synoptic circulation patterns associated with high and low precipitation efficiency are identified, and the importance of large-scale dynamics and local convective processes in regulating vertical distributions of atmospheric constituents important for climate is evaluated. The results suggest that high e days are correlated with plume-like transport originating from the relatively clean tropics, while low e days are associated with westerly transport, generated by a branching of the jet stream. Differences in transport pathway clearly modify background concentrations of water vapor and other trace gases measured at Mauna Loa Observatory; however, local convective processes appear to regulate aerosols there. Indeed, differences between observed and simulated diurnal cycles of particle number concentration indicate that precipitation scavenges aerosols and possibly facilitates new particle formation when e is high. As measurements of isotope ratios in water vapor expand across the subtropics, the techniques presented here can further our understanding of how synoptic weather, precipitation processes, and climate feedbacks interrelate.

  5. Investigating late Holocene variations in hydroclimate and the stable isotope composition of precipitation using southern South American peatlands: a hypothesis

    NASA Astrophysics Data System (ADS)

    Daley, T. J.; Mauquoy, D.; Chambers, F. M.

    2012-02-01

    Ombrotrophic raised peatlands provide an ideal archive for integrating late Holocene records of variations in hydroclimate and the estimated stable isotope composition of precipitation with recent instrumental measurements. Modern measurements of mean monthly surface air temperature, precipitation and δD and δ18O values in precipitation from the late twentieth and early twenty-first centuries provide a short but invaluable record with which to investigate modern relationships between these variables, thereby enabling improved interpretation of the peatland palaeodata. Data from two stations in the Global Network for Isotopes in Precipitation (GNIP) from Tierra del Fuego (Punta Arenas, Chile and Ushuaia, Argentina) were analysed for the period 1982 to 2008. In both locations, δD and δ18O values have decreased in response to quite different trends in local surface air temperature and total precipitation amount. At Ushuaia, the fall in δ18O values is associated with an increase in the mean annual amount of precipitation. At Punta Arenas, the fall in δ18O values is weakly associated with decrease in the precipitation amount and an increase in local temperatures. The pattern in both records is consistent with an increase in the zonal intensity of the southern westerly wind belt. These regional differences, observed in response to a known driver, should be detectable in peatland sites close to the GNIP stations. There is currently insufficient availability of suitably temporally resolved data to test for these regional differences over the last 3000 yr. Existing peatland palaeoclimate data from two sites near Ushuaia, however, provide evidence for changes in the late Holocene that are consistent with the pattern observed in modern observations. Furthermore, the records suggest synchroneity in millennial-scale oscillations between the Northern and Southern Hemispheres.

  6. Insights into streamflow generation mechanisms using high-frequency analysis of isotopes and water quality in streamflow and precipitation

    NASA Astrophysics Data System (ADS)

    von Freyberg, Jana; Kirchner, James W.

    2017-04-01

    In the pre-Alpine Alptal catchment in central Switzerland, snowmelt and rainfall events cause rapid changes not only in hydrological conditions, but also in water quality. A flood forecasting model for such a mountainous catchment thus requires process understanding that is informed by high-frequency monitoring of hydrological and hydrochemical parameters. Therefore, we installed a high-frequency sampling and analysis system near the outlet of the 0.7 km2 Erlenbach catchment, a headwater tributary of the Alp river. We measured stable water isotopes (δ18O, δ2H) in precipitation and streamwater using Picarro, Inc.'s (Santa Clara, CA, USA) newly developed Continuous Water Sampler Module (CWS) coupled to their L2130-i Cavity Ring-Down Spectrometer, at 30 min temporal resolution. Water quality was monitored with a dual-channel ion chomatograph (Metrohm AG, Herisau, Switzerland) for analysis of major cations and anions, as well as with a UV-Vis spectroscopy system and electrochemical probes (s::can Messtechnik GmbH, Vienna, Austria) for characterization of nutrients and basic water quality parameters. For quantification of trace elements and metals, we collected additional water samples for subsequent ICP-MS analysis in the laboratory. To illustrate the applicability of our newly developed automated analysis and sampling system under field conditions, we will present initial results from the 2016 fall and winter seasons at the Erlenbach catchment. During this period, river discharge was mainly fed by groundwater, as well as intermittent snowmelt and rain-on-snow events. Our high-frequency data set, along with spatially distributed sampling of snowmelt, enables a detailed analysis of source areas, flow pathways and biogeochemical processes that control chemical dynamics in streamflow and the discharge regime.

  7. Precipitation Estimate Using NEXRAD Ground-Based Radar Images: Validation, Calibration and Spatial Analysis

    SciTech Connect

    Zhang, Xuesong

    2012-12-17

    Precipitation is an important input variable for hydrologic and ecological modeling and analysis. Next Generation Radar (NEXRAD) can provide precipitation products that cover most of the continental United States with a high resolution display of approximately 4 × 4 km2. Two major issues concerning the applications of NEXRAD data are (1) lack of a NEXRAD geo-processing and geo-referencing program and (2) bias correction of NEXRAD estimates. In this chapter, a geographic information system (GIS) based software that can automatically support processing of NEXRAD data for hydrologic and ecological models is presented. Some geostatistical approaches to calibrating NEXRAD data using rain gauge data are introduced, and two case studies on evaluating accuracy of NEXRAD Multisensor Precipitation Estimator (MPE) and calibrating MPE with rain-gauge data are presented. The first case study examines the performance of MPE in mountainous region versus south plains and cold season versus warm season, as well as the effect of sub-grid variability and temporal scale on NEXRAD performance. From the results of the first case study, performance of MPE was found to be influenced by complex terrain, frozen precipitation, sub-grid variability, and temporal scale. Overall, the assessment of MPE indicates the importance of removing bias of the MPE precipitation product before its application, especially in the complex mountainous region. The second case study examines the performance of three MPE calibration methods using rain gauge observations in the Little River Experimental Watershed in Georgia. The comparison results show that no one method can perform better than the others in terms of all evaluation coefficients and for all time steps. For practical estimation of precipitation distribution, implementation of multiple methods to predict spatial precipitation is suggested.

  8. Macroscale Circulation Patterns as Reflected in Spatial and Temporal Patterns of Precipitation over the Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Conselyea, K.; Yin, Z.

    2007-12-01

    Circulation patterns such as the NAO, PNA, and AO have been known to impact climate both near the action centers and at great distances away. These macroscale circulation patterns can impact regional wind patterns, temperature gradients and pressure gradients. Changes in these gradients can cause an onset of various weather conditions including precipitation. Precipitation across the Tibetan Plateau is influenced by known phenomena such as monsoon systems and teleconnections. Previous studies have suggested that other forcing mechanisms also may play a vital role in influencing precipitation in this region. To evaluate potential forcing factors affecting precipitation across the Tibetan Plateau, the relationship between the spatial and temporal patterns of precipitation and the regional and macroscale circulation patterns will be investigated. To explore this relationship statistical analysis, such as Principal Component Analysis (PCA), Correlation Field Analysis, and Canonical Correspondence Analysis (CCA), is preformed. This study also incorporates tree ring chronologies from Qilian junipers (Sabina przewalskii Kom.) sampled in the Qaidam Basin, northeastern Tibetan Plateau. These data have been used in previous studies to indicate environmental change, and tree rings taken from this region have shown signatures of circulation patterns such as Arctic Oscillation (AO). Based on the relationship between tree ring data and circulation patterns it is possible to reconstruct past events. This information along with examination of National Centers for Environmental Protection/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis data will aid in the examination of the relationship between teleconnection patterns and precipitation, and develop a greater understanding of the precipitation variability across the Tibetan Plateau.

  9. Spatial-Temporal Structures of Trend and Oscillatory Variabilities of Precipitation over Northern Eurasia.

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolan L.; Cho, Han-Ru

    1997-09-01

    Combinations of statistical analyses including principal component analysis, and uni- and multivariate singular spectrum analyses, were carried out to characterize the spatial-temporal structures of trend and interannual oscillatory variabilities of precipitation over the major north-flowing river basins in the former Soviet Union.The series of monthly precipitation were corrected for the biases of precipitation measurement due to the gauge-type change and changes in observing procedures. An upward trend was found in the monthly precipitation series for the last half century. This upward trend was stronger in the North Dvina and Pechora River basins, and in the Ob-Irtysh River basins, but much weaker (still upward, though) in the Yenisey-Lena River basins. The notable increases of precipitation over the southwestern part-the Volga and Ural River basins-were found to be due at least in part to the upward phase of some quasi-century periodicity. Generally speaking, the precipitation increases appeared to be more apparent during the cold seasons in the western half of the sector, while in the eastern part, it appeared to be equally or more notable during summer.On the interannual timescales, signals of 4-5-yr and quasi-biennial oscillations were found in the space-time-dependent precipitation series. The 4-5-yr oscillation was quite apparent over the entire Northern Eurasian sector, being stronger over the southeastern and western parts. This oscillation appeared to propagate eastward. The quasi-biennial oscillation was generally weaker; it was very weak during the 1955-65 period. This oscillation was relatively stronger in the western half of the sector and weaker over the eastern half.

  10. Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China

    NASA Astrophysics Data System (ADS)

    Fang, Y. T.; Koba, K.; Wang, X. M.; Wen, D. Z.; Li, J.; Takebayashi, Y.; Liu, X. Y.; Yoh, M.

    2011-02-01

    Nitric acid (HNO3) or nitrate (NO3-) is the dominant sink for reactive nitrogen oxides (NOx = NO + NO2) in the atmosphere. In many Chinese cities, HNO3 is becoming a significant contributor to acid deposition. In the present study, we measured nitrogen (N) and oxygen (O) isotopic composition of NO3- in 113 precipitation samples collected from Guangzhou City in southern China over a two-year period (2008 and 2009). We attempted to better understand the spatial and seasonal variability of atmospheric NOx sources and the NO3- formation pathways in this N-polluted city in the Pearl River Delta region. The δ15N values of NO3- (versus air N2) ranged from -4.9 to +10.1‰, and averaged +3.9‰ in 2008 and +3.3‰ in 2009. Positive δ15N values were observed throughout the year, indicating the anthropogenic contribution of NOx emissions, particularly from coal combustion. Different seasonal patterns of δ15N-NO3- were observed between 2008 and 2009, which might reflect different human activities associated with the global financial crisis and the intensive preparations for the 16th Asian Games. Nitrate δ18O values (versus Vienna Standard Mean Ocean Water) varied from +33.4 to +86.5‰ (average +65.0‰ and +67.0‰ in 2008 and 2009, respectively), a range being lower than those reported for high latitude and polar areas. Sixteen percent of δ18O values was observed lower than the expected minimum of +55‰ at our study site. This was likely caused by the reaction of NO with peroxy radicals; peroxy radicals can compete with O3 to convert NO to NO2, thereby donate O atoms with much lower δ18O value than that of O3 to atmospheric NO3-. Our results highlight that the influence of human activities on atmospheric chemistry can be recorded by the N and O isotopic composition of atmospheric NO3- in a N-polluted city.

  11. Anthropogenic imprints on nitrogen and oxygen isotopic composition of precipitation nitrate in a nitrogen-polluted city in southern China

    NASA Astrophysics Data System (ADS)

    Fang, Y. T.; Koba, K.; Wang, X. M.; Wen, D. Z.; Li, J.; Takebayashi, Y.; Liu, X. Y.; Yoh, M.

    2010-09-01

    Nitric acid (HNO3) or nitrate (NO3-) is the dominant sink for reactive nitrogen oxides (NOx = NO + NO2) in the atmosphere. In many Chinese cities, HNO3 is becoming a significant contributor to acid deposition. In the present study, we used the denitrifier method to measure nitrogen (N) and oxygen (O) isotopic composition of NO3- in 113 precipitation samples collected from Guangzhou City in southern China over a two-year period (2008 and 2009). We attempted to better understand the spatial and seasonal variability of atmospheric NOx sources and the NO3- formation pathways in this N-polluted city in the Pearl River Delta region. The δ15N values of NO3- (versus air N2) ranged from -4.9 to +10.1‰, and averaged +3.9‰ in 2008 and +3.3‰ in 2009. Positive δ15N values were observed throughout the year, indicating the anthropogenic contribution of NOx emissions, particularly from coal combustion. Different seasonal patterns of δ15N-NO3- were observed between 2008 and 2009, which might reflect different human activities associated with the global financial crisis and the intensive preparations for the 16th Asian Games. Nitrate δ18O values (versus Vienna Standard Mean Ocean Water) varied from +33.4 to +86.5‰ (average +65.0‰ and +67.0‰ in 2008 and 2009, respectively), a range being lower than those reported for high altitude and polar areas. Several δ18O values were observed lower than the expected minimum of 50‰ at our study site. This was likely caused by the reaction of NO with peroxy radicals; peroxy radicals can compete with O3 to convert NO to NO2, thereby donate O atoms with much lower δ18O value than that of O3 to atmospheric NO3-. Our results highlight that the influence of human activities on atmospheric chemistry can be recorded by the N and O isotopic composition of atmospheric NO3- in a N-polluted city.

  12. Clumped isotope disequilibrium during rapid CO2 uptake and carbonate precipitation in subaerial alkaline springs associated with ongoing serpentinization

    NASA Astrophysics Data System (ADS)

    Falk, E. S.; Guo, W.; Kelemen, P. B.

    2014-12-01

    Ongoing serpentinization in tectonically exposed ultramafic bodies is manifested at the surface in alkaline springs (pH >11). Where these high-pH waters come in contact with CO2 at the surface, rapid calcite precipitation forms extensive travertines. We study natural travertine samples from Oman and synthetic witherite (BaCO3) from high-pH experiments to identify disequilibrium signals in δ18O, δ13C and clumped isotopes (measured as Δ47) that characterize rapid uptake of atmospheric CO2 and carbonate precipitation from high pH fluids. Kinetic effects preclude the use of clumped or oxygen isotopes for carbonate thermometry in these environments, but trends in δ18O, δ13C and Δ47 could help identify extinct alkaline systems or distinguish CO2 sources. Oman travertines formed at peridotite-hosted alkaline springs have long been known to exhibit a large range of kinetically depleted δ18O and δ13C values. We find fresh carbonate precipitated at these alkaline springs also exhibit large enrichments in Δ47 that covary with the depletions in δ18O and δ13C, thought to arise during hydroxylation of CO2 in high-pH fluids. Witherite precipitated during rapid CO2 uptake and carbonate precipitation in high pH experiments also exhibits disequilibrium values in δ18O, δ13C and Δ47, with the Δ47 of carbonate precipitates strongly affected by the Δ47 the reactant CO2. δ18O, δ13C and Δ47 trends could serve as a marker for carbonates formed in subaerial alkaline environments and track carbon sources in these systems. For example, the δ18O-δ13C slope in carbonates from Martian meteorites is similar to that observed in carbonates from terrestrial alkaline springs, so if corresponding enrichments in Δ47 could be identified in Martian carbonates, it could suggest that alkaline springs were present on the surface of Mars. Clumped isotope signals could also help distinguish carbon sources: kinetic enrichments in Δ47 would be absent or diminished in high-pH carbonates

  13. Positive precipitation-evaporation budget from AD 460 to 1090 in the Saloum Delta (Senegal) indicated by mollusk oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Azzoug, Moufok; Carré, Matthieu; Chase, Brian M.; Deme, Abdoulaye; Lazar, Alban; Lazareth, Claire E.; Schauer, Andrew J.; Mandeng-Yogo, Magloire; Simier, Monique; Thierno-Gaye, Amadou; de Morais, Luis Tito

    2012-12-01

    There is a critical need to document the long-term variability of the West African Monsoon (WAM) in the Sahel region. We present here a multidecadal proxy record of the past hydrology from AD 460 to 1090 in the Saloum Delta, Senegal. The Saloum Delta is a hypersaline estuary where the salinity and the water isotopic composition are highly sensitive to rainfall variations. The past hydrology was studied using the oxygen isotopic ratio of Anadara senilis fossil shells, since mollusk shell isotopic composition (δ18O) in this environment is primarily determined by the precipitation-evaporation budget. Successive samples of shells were taken along the stratigraphy of the massive Dioron Boumak fossil shell middens for new insights into the past WAM multi-decadal to centennial variability. The averaged δ18O value of fossil shells was more negative by 1.4‰ compared to modern shells' isotopic signature. This result indicates substantially fresher mean conditions in the Saloum Delta, that was likely not hypersaline as it is today. The precipitation-evaporation budget was thus more positive in response to a more intense and/or longer monsoon season during the studied period. Our record suggests that strong multidecadal droughts as observed in the Sahel in the late 20th century did likely not occur in Senegal during this ~ 600-yr time period.

  14. Stable isotope study of precipitation and cave drip water in Florida (USA): implications for speleothem-based paleoclimate studies.

    PubMed

    Onac, Bogdan P; Pace-Graczyk, Kali; Atudirei, Viorel

    2008-06-01

    Stable isotopes of hydrogen and oxygen were used to examine how the isotopic signal of meteoric water is modified as it travels through soil and epikarst into two caves in Florida. Surface and cave water samples were collected every week from February 2006 until March 2007. The isotopic composition of precipitation at the investigated sites is highly variable and shows little seasonal control. The delta18O vs. delta2H plot shows a mixing line having a slope of 5.63, suggesting evaporation effects dominate the isotopic composition of most rainfall events of less than 8 cm/day, as indicated by their low d-excess values. The delta18O values of the drip water show little variability (<0.6 per thousand), which is loosely tied to local variations in the seasonal amount of precipitation. This is only seen during wintertime at the Florida Caverns site. The lag time of over two months and the lack of any relationship between rainfall amount and the increase in drip rate indicate a dominance of matrix flow relative to fracture/conduit flow at each site. The long residence time of the vadose seepage waters allows for an effective isotopic homogenisation of individual and seasonal rainfall events. We find no correlation between rainfall and drip water delta18O at any site. The isotopic composition of drip water in both caves consistently tends to resemble the amount-weighted monthly mean rainfall input. This implies that the delta18O of speleothems from these two caves in Florida cannot record seasonal cycle in rainfall delta18O, but are suitable for paleoclimate reconstructions at inter-annual time scales.dagger.

  15. Modeling the response of precipitation oxygen stable isotopes to the Eocene climate changes over Asia

    NASA Astrophysics Data System (ADS)

    Botsyun, Svetlana; Sepulchre, Pierre; Donnadieu, Yannick; Risi, Camille; Caves, Jeremy K.; Licht, Alexis

    2017-04-01

    The Himalayas and the Tibetan Plateau have become a focus of the Earth sciences because they provide a classical example of tectonics-climate interactions. Present-day high elevations of the Himalayas and the Tibetan Plateau is the ultimate result of the collision between Indian and Asia plates during the Cenozoic, however, the precise uplift history of the Himalayas and the Tibetan Plateau is still uncertain, especially for the early Cenozoic. For the purpose of paleoelevations reconstructions, multiple methods are available, but stable oxygen paleoaltimetry is considered to be one of the most efficient techniques and has been widely applied in Asia. However, paleoelevations studies using stable oxygen presume that climatic processes control δ18O in a uniform way through time. We use climate modeling tools in order to investigate Eocene climate and δ18O over Asia and its controlling factors. The state-of-the-art general circulation model embedded with isotopes LMDz-iso has been applied together with Eocene boundary conditions and varied Eocene topography of the Himalayas and Tibet. The results of our simulations suggest that topography change has a minor direct impact on δ18O over the Himalayas and the Tibetan Plateau. On the contrary, Eocene δ18O in precipitation is primarily controlled by the atmosphere circulation and global temperature changes. Based on our numerical experiments, we show that despite persistence of large-scale atmospheric flows such as the monsoons and westerlies, Eocene δ18O over the region is different from those of the present-day due to global higher temperatures, southward shift to a zone of strong convection and increased role of westerlies moisture source. We show that the Rayleigh distillation is not applicable for the Eocene Himalayas and conclude that the assumption about the stationarity of δ18O-elevation relationship through geological time is inaccurate and misleading for paleoelevation estimates. We also show that Eocene

  16. Spatial and Temporal Migration Patterns of Neotropical Migrants in the Southwest Revealed by Stable Isotopes

    USGS Publications Warehouse

    Paxton, Kristina L.; van Riper, Charles

    2006-01-01

    Executive Summary We used stable hydrogen isotopes (?D) to investigate both temporal and spatial patterns during spring migration for three warbler species, Wilson's Warbler (Wilsonia pusilla), MacGillivray's Warbler (Oporornis tolmiei), and Nashville Warbler (Vermivora ruficapilla), across multiple migration routes in southwest North America. A strong correlation between stable hydrogen isotope values of feathers and the local precipitation at sites where feathers where collected across the breeding range for all three species reaffirmed that stable hydrogen isotopes were a good predictor of breeding locations. For the Wilson's Warbler, we found a significant negative relationship between the date when warblers passed through the sampling station and ?D values of their feathers, indicating that warblers who bred the previous season at southern latitudes migrated through the migration stations earlier than did warblers that had previously bred at more northern latitudes. This pattern was consistent across their southwestern migration route (5 sites sampled) and was consistent between years. Comparing ?D values between migration stations also showed a shift towards more negative ?D values from the western to the eastern migration stations sampled in this study, which corresponded to different geographical regions of the Wilson's Warblers' western breeding range. For MacGillivray's Warbler we found the same temporal pattern as Wilson's Warbler, with warblers that bred the previous season at southern latitudes migrating through the migration stations earlier than warblers that had previously bred at more northern latitudes. This pattern was consistent at the Lower Colorado River and Arivaca Creek, the two sites where sample sizes were adequate to test these hypotheses. Comparison of the ?D between the two sites indicated that the majority of warblers migrating through these stations were breeding within a geographically limited area of MacGillivray's Warblers' overall

  17. Impact of precipitation and physical characteristics spatial variabilities on hydrological response at large catchment scale

    NASA Astrophysics Data System (ADS)

    Rouhier, Laura; Garavaglia, Federico; Le Lay, Matthieu; Le Moine, Nicolas; Ribstein, Pierre; Hendrickx, Frédéric

    2017-04-01

    The spatial variability of the hydrological response is controlled by the interaction of two spatial variabilities: (i) meteorological forcing and (ii) physical characteristics. This work aims at evaluating their relative impact on streamflow modeling throughout a catchment. To tackle the issue, a spatially distributed rainfall-runoff model, named MORDOR-TS, is used. It is a distributed version of the conceptual rainfall-runoff model currently used at Électricité de France (EDF, French electric utility company) for operational applications. The analysis is conducted at large catchment scale, on the French Loire catchment at Gien (35 707 km2) discretised at the maximum into 387 hydrological meshes of about 100km2. Within this one, 106 streamflow time series are available between 1980 and 2012. According to a spatial split-sample test scheme, the data is split into two similar parts: a calibration and a validation sample of 53 gauges each. For a model calibrated on the catchment outlet only, the impact of the rainfall pattern is assessed by testing several aggregations of the precipitation field, from uniform to mesh scale. Then, the spatial physical information is added in two steps. Firstly, the valuable information about interior gauges is taken into account by calibrating a uniform set of parameters on the whole calibration sample. Secondly, the parameters are spatialised to represent the physiographic and pedologic spatial variabilities. Dividing the catchment into sub-basins, there could be as many parameter sets calibrated as there are calibration sites. Regarding the validation sample, the worst performance is provided by a unique lumped model, while the best is given by a set of 53 independent distributed models calibrated on each validation station. The main progress from the worst towards the best case is obtained with the precipitation spatial variability (around 85% of the total progress). Interior gauges and parameters spatialisation bring some

  18. Seasonal transfer of oxygen isotopes from precipitation and soil to the tree ring: source water versus needle water enrichment.

    PubMed

    Treydte, Kerstin; Boda, Sonja; Graf Pannatier, Elisabeth; Fonti, Patrick; Frank, David; Ullrich, Bastian; Saurer, Matthias; Siegwolf, Rolf; Battipaglia, Giovanna; Werner, Willy; Gessler, Arthur

    2014-05-01

    For accurate interpretation of oxygen isotopes in tree rings (δ(18) O), it is necessary to disentangle the mechanisms underlying the variations in the tree's internal water cycle and to understand the transfer of source versus leaf water δ(18) O to phloem sugars and stem wood. We studied the seasonal transfer of oxygen isotopes from precipitation and soil water through the xylem, needles and phloem to the tree rings of Larix decidua at two alpine sites in the Lötschental (Switzerland). Weekly resolved δ(18) O records of precipitation, soil water, xylem and needle water, phloem organic matter and tree rings were developed. Week-to-week variations in needle-water (18) O enrichment were strongly controlled by weather conditions during the growing season. These short-term variations were, however, not significantly fingerprinted in tree-ring δ(18) O. Instead, seasonal trends in tree-ring δ(18) O predominantly mirrored trends in the source water, including recent precipitation and soil water pools. Modelling results support these findings: seasonal tree-ring δ(18) O variations are captured best when the week-to-week variations of the leaf water signal are suppressed. Our results suggest that climate signals in tree-ring δ(18) O variations should be strongest at temperate sites with humid conditions and precipitation maxima during the growing season.

  19. Diurnal and spatial variation of remotely sensed precipitation over Indian region

    NASA Astrophysics Data System (ADS)

    Rajan, D.; Iyengar, G. R.; Mitra, A. K.

    2016-05-01

    The climate of India is dominated by monsoon systems. The remotely sensed estimates obtained from the Tropical Rainfall Measuring Mission (TRMM) are used to examine the most of the Indian monsoon systems. This study deals with the diurnal and spatial variation of precipitation over the Indian region. The precipitation data from TRMM Multi-satellite Precipitation Analysis (TMPA), blended from a variety of sources (including rain gauges over land) and having both daily and 3- hourly output are being used for evaluation of the Numerical Weather Prediction models Basu (2007) of National Centre for Medium Range Weather Forecasting. The precipitation obtained from TRMM 3B42 for this study period has a spatial resolution of 0.25º X 0.25º latitude-longitude. The 3-hourly averaged values are centered at the middle of each 3 hr period. South Asian regions are dominated by seasonal climatic fluctuations and the major rainy season is the southwest monsoon season. In addition to the seasonal fluctuations, Indian summer monsoon is modulated by diurnal fluctuations; nature of diurnal variation of rainfall varies from place to place and depends upon the locations, topography of the region. Diurnal variation of rain-rate, frequency of rain, conditional rain rate, and maximum and minimum rain occurrence is studied. Over Indian tropical region, maximum rainfall over land and Bay of Bengal regions is observed during the late-afternoon and early-morning period, respectively. Drizzle or less rainfall occur frequently in the morning over most land areas, whereas convective activity occurs during the afternoon. The model predicted diurnal cycle of precipitation peaks too early (by ~3h) and the amplitude is too strong over Indian land region and tropical ocean region.

  20. Summer precipitation influences the stable oxygen and carbon isotopic composition of tree-ring cellulose in Pinus ponderosa.

    PubMed

    Roden, John S; Ehleringer, James R

    2007-04-01

    The carbon and oxygen isotopic composition of tree-ring cellulose was examined in ponderosa pine (Pinus ponderosa Dougl.) trees in the western USA to study seasonal patterns of precipitation inputs. Two sites (California and Oregon) had minimal summer rainfall inputs, whereas a third site (Arizona) received as much as 70% of its annual precipitation during the summer months (North American monsoon). For the Arizona site, both the delta(18)O and delta(13)C values of latewood cellulose increased as the fraction of annual precipitation occurring in the summer (July through September) increased. There were no trends in latewood cellulose delta(18)O with the absolute amount of summer rain at any site. The delta(13)C composition of latewood cellulose declined with increasing total water year precipitation for all sites. Years with below-average total precipitation tended to have a higher proportion of their annual water inputs during the summer months. Relative humidity was negatively correlated with latewood cellulose delta(13)C at all sites. Trees at the Arizona site produced latewood cellulose that was significantly more enriched in (18)O compared with trees at the Oregon or California site, implying a greater reliance on an (18)O-enriched water source. Thus, tree-ring records of cellulose delta(18)O and delta(13)C may provide useful proxy information about seasonal precipitation inputs and the variability and intensity of the North American monsoon.

  1. Uncertainty in watershed response predictions induced by spatial variability of precipitation.

    PubMed

    Chang, Chia-Ling; Lo, Shang-Lien; Chen, Ming-Ying

    2007-04-01

    Negligence to consider the spatial variability of rainfall could result in serious errors in model outputs. The objective of this study was to examine the uncertainty of both runoff and pollutant transport predictions due to the input errors of rainfall. This study used synthetic data to represent the "true" rainfall pattern, instead of interpolated precipitation. It was conducted on a synthetic case area having a total area of 20 km(2) with ten subbasins. Each subbasin has one rainfall gauge with synthetic precipitation records. Six rainfall storms with varied spatial distribution were generated. The average rainfall was obtained from all of the ten gauges by the arithmetic average method. The input errors of rainfall were induced by the difference between the actual rainfall pattern and estimated average rainfall. The results show that spatial variability of rainfall can cause uncertainty in modeling outputs of hydrologic, which would be transport to pollutant export predictions, when uniformity of rainfall is assumed. Since rainfall is essential information for predicting watershed responses, it is important to consider the properties of rainfall, particularly spatial rainfall variability, in the application of hydrologic and water quality models.

  2. Carbon Isotopes in Pinus elliotti from Big Pine Key, Florida: Indicators of Seasonal Precipitation, ENSO and Disturbance Events

    NASA Astrophysics Data System (ADS)

    Rebenack, C.; Willoughby, H. E.; Anderson, W. T.; Cherubini, P.

    2013-12-01

    The South Florida coastal ecosystem is among the world's subtropical coastlines which are threatened by the potential effects of climate change. A well-developed localized paleohistory is essential in the understanding of the role climate variability/change has on both hydrological dynamics and disturbance event frequency and intensity; this understanding can then aid in the development of better predictive models. High resolution paleoclimate proxies, such as those developed from tree-ring archives, may be useful tools for extrapolating actual climate trends over time from the overlapping long-term and short-term climate cycles, such as the Atlantic Multidecadal Oscillation (AMO) and the El Niño-Southern Oscillation (ENSO). In South Florida, both the AMO and ENSO strongly influence seasonal precipitation, and a more complete grasp of how these cycles have affected the region in the past could be applied to future freshwater management practices. Dendrochronology records for the terrestrial subtropics, including South Florida, are sparse because seasonality for this region is precipitation driven; this is in contrast to the drastic temperature changes experienced in the temperate latitudes. Subtropical seasonality may lead to the complete lack of visible rings or to the formation of ring structures that may or may not represent annual growth. Fortunately, it has recently been demonstrated that Pinus elliottii trees in South Florida produce distinct annual growth rings; however ring width was not found to significantly correlate with either the AMO or ENSO. Dendrochronology studies may be taken a step beyond the physical tree-ring proxies by using the carbon isotope ratios to infer information about physiological controls and environmental factors that affect the distribution of isotopes within the plant. It has been well established that the stable isotope composition of cellulose can be related to precipitation, drought, large-scale ocean/atmospheric oscillations

  3. Spatial and temporal variation of H and O isotopic compositions of the Xijiang River system, Southwest China.

    PubMed

    Han, Guilin; Lv, Pin; Tang, Yang; Song, Zhaoliang

    2017-08-30

    Ratios of stable isotopes of hydrogen and oxygen ((2)H/(1)H and (18)O/(16)O) in river waters were measured to investigate the hydrological pathway of the Xijiang River, Southwest China. The δ(2)H and δ(18)O values of river waters exhibit significant spatial and temporal variations and the isotopic compositions vary with elevation, temperature and precipitation of the recharge area. Spatially, δ(18)O values of river waters from high mountain areas are lower than those from the lower reaches of the Xijiang River due to lower temperature and higher elevation for the recharge area. However, both (2)H and (18)O are enriched differently in river waters from the middle reaches during the high flow season, depending on the season and degree of anthropogenic disturbances (e.g. water impoundments). In contrast, deuterium excess (d-excess) values of waters from the middle reaches are substantially lower than those from the upper and lower reaches, suggesting that river waters may be resided in the reservoir and evaporation increases in the middle reaches of the Xijiang River.

  4. Separation of spatial and temporal structure of auroral particle precipitation (Invited)

    NASA Astrophysics Data System (ADS)

    Boudouridis, A.; Spence, H.

    2013-12-01

    Knowledge of the dominant temporal and spatial scales of auroral features is instrumental in understanding the various mechanisms responsible for auroral particle precipitation. Single spacecraft data suffer from temporal/spatial ambiguity. In an effort to separate the temporal and spatial variations of the aurora, we use electron and ion precipitation data from two co-orbiting satellites, F6 and F8 of the Defense Meteorological Satellite Program (DMSP). The two spacecraft have almost identical polar orbits with a small difference in period. As a result the time difference between the two measurements varies with time. We use two statistical tools in order to determine the most probable lifetimes and spatial dimensions of the prevalent auroral features, Cross Correlation Analysis (CCA) and Cross Spectral Analysis (CSA). The CCA is applied to the magnetic latitude series of electron and ion, integral number and energy fluxes measured by the two DMSP spacecraft. As one spacecraft overtakes the other, the variable time lag between the two measurements results in different cross correlation of the two series. We explore the dependence of this variation on the time lag between the satellites. We find that the electron precipitation exhibits a decreasing correlation between the two spacecraft with increasing time lag, whereas there is only a small similar effect for the ion precipitation data. For the CSA we compute the so-called coherence function as a function of frequency (or inverse wavelength), and hence size of the auroral features. The coherence function is a measure of the stability of auroral features of different sizes. We investigate its variation as a function of the time separation between the two DMSP spacecraft measurements. We show that the coherence function of both electrons and ions remains high for up to 1.5 min spacecraft separations for all features larger than about 100 km in width. For smaller features the coherence is lower even for time lags of

  5. Spatially resolved Fe- and S-isotope composition of sedimentary pyrite

    NASA Astrophysics Data System (ADS)

    Rouxel, O.; Bekker, A.; Germain, Y.; Ponzevera, E.

    2012-04-01

    Past studies of iron and sulfur isotope records of sedimentary sulfides over geological time have placed important constraints on the biogeochemical cycle of sulfur and iron and the evolution of ocean chemistry. Since biogeochemical cycles of Fe and S are closely coupled in marine systems, Fe-limitation and S-limitation for pyrite formation in black shales should leave an imprint on the isotopic record of both elements. We developed a technique for accurate and spatially-resolved measurement of 34S/32S, 33S/32S, 56Fe/54Fe, and 57Fe/54Fe isotope ratios in sedimentary pyrite using a combination of solution and laser ablation analysis. Fe- and S-isotope ratios were measured by high-resolution MC-ICP-MS (ThermoElectron Neptune), enabling us to resolve major isobaric interferences on S isotopes and Fe isotopes from O2+, ArN+, and ArO+. A CETAC LSX 213 nm laser was used as the ablation source with He as the sample carrier gas. Fe- and S-isotope ratios were calibrated against several pyrite standards using the conventional "sample-standard bracketing technique". Instrumental mass bias of Fe and S isotopes were also corrected through an internal normalization technique using respectively Ni and Mg of known isotope composition. The long-term reproducibility of S- and Fe-isotope compositions was typically better than 0.2 per mil. We investigated the fine scale variations of d56Fe, d34S and d33S values of diagenetic pyrite nodules in several Devonian, Paleoproterozoic and Archean black shales in order to (1) explore biosignature potential of co-variations of Fe- and S-isotopes at the grain-size scale; (2) assess potential diagenetic effects on Fe-isotope fractionation during sulfide formation; and (3) assess potential mixing between isotopically distinct Fe- and S-pools using multiple S isotope data. Those results will be presented together with bulk stratigraphic S- and Fe-isotopic variations and Fe speciation data in order to establish an Fe isotope mass balance in black

  6. Developing robust spatial interpolation techniques for temperature and precipitation in a data-sparse alpine catchment

    NASA Astrophysics Data System (ADS)

    Jobst, Andreas; Kingston, Daniel; Cullen, Nicolas

    2015-04-01

    Providing adequate input data are available, distributed and physically-based hydrological models should constitute the most detailed and realistic possible representation of catchment hydrology. However, the combination of sparse monitoring networks and the high spatio-temporal variability of climate in alpine environments makes such models challenging to implement. Here, a fully distributed hydrological model (WaSIM) is implemented for the Clutha river, New Zealand, at a spatial resolution of 1 km2. The Clutha catchment (21680 km2) is the largest in New Zealand and is situated in the lower half of the South Island, extending eastwards from the Southern Alps. The interaction of the predominant westerly winds with the steep orography of the Southern Alps leads to a large precipitation gradient decreasing sharply from annual totals above 10 m near the main divide to less than 0.5 m inland. In the upper catchment, large amounts of precipitation are stored as seasonal snow, which significantly influences the annual discharge regime. As such, a correct spatial representation of precipitation totals and high elevation temperature is fundamental to the realistic simulation of river flow. However, there are no long term precipitation sites in the headwaters, and only two (relatively short) high elevation temperature records. Furthermore, the majority of long-term temperature records are located in inter-montane valleys that are prone to strong winter lapse rate inversions. Consequently, standard interpolation techniques or fixed lapse rates do not provide suitably realistic temperature or precipitation fields that are fundamental to accurately simulate the spatial variation in catchment hydrology. In order to overcome these issues of data availability, a variety of geostatistical techniques have been investigated as the basis for generating realistic climate fields. The development of the precipitation field was based on a trivariate spline and a 30-year rainfall normal

  7. Tracing atmospheric moisture from precipitation δ18O to climate proxy using an isotope enabled land surface model

    NASA Astrophysics Data System (ADS)

    Kanner, L.; Buenning, N. H.; Stott, L. D.; Timmermann, A.

    2013-12-01

    A paleoclimate interpretation of a terrestrial hydrologic proxy such as the δ18O of tree cellulose or speleothem calcite may be biased or misinterpreted if the isotopic composition of the soil water from which the proxy originated undergoes isotopic exchange or fractionation. In this study, we use a global isotope-enabled land surface model (IsoLSM) to investigate how the δ18O of precipitation may be altered in a soil column due to evaporation and vertical moisture flux. In order to assess how precipitation and evaporation contribute the soil water isotopic variability, we compare seasonal and interannual changes in simulated xylem water δ18O within a control simulation and in a suite of experiments where the effect of precipitation δ18O, water vapor δ18O, and ground water evaporation are independently removed. The simulations, carried out for 1979 to 2004, reveal that in semi-arid regions, such as the southwest United States, the seasonal cycle in xylem water δ18O is strongly affected by evaporative loss during the dry season and this can constitute as much as 50% of the interannual δ18O variance. Additional simulations, including soil water tagging experiments, indicate that upward fluxes of soil water occur during drier periods. For soil water δ18O profiles that are isotopically more depleted in 18O at depth, this imparts a low isotopic signature to xylem water δ18O during such dry intervals. Hence, without taking into account moisture flux processes, an isotopic proxy could be misinterpreted as wet conditions (due to decreased evaporative enrichment) for low δ18O years when instead drier conditions are equally as likely. Using IsoLSM simulated xylem water and leaf water δ18O, offline calculations of cellulose δ18O compare well with observations in diverse climatic regimes. Thus, the driving mechanisms on soil water δ18O identified in this study, and in particular the important role of evaporation on seasonal and interannual timescales, may

  8. Stable isotope signatures of northern California precipitation during an El Niño winter: implications for speleothem paleoclimate reconstructions

    NASA Astrophysics Data System (ADS)

    Weisman, I. E.; Oster, J. L.; Ahmed, A.; Fogarty, M.; Mix, H.

    2016-12-01

    Despite the significant influence that the El Niño/Southern Oscillation (ENSO) can have on California precipitation, stable isotope signatures of precipitation during strong El Niño events in California remain poorly constrained. In order to investigate the potentially variable isotopic signature of El Niño storms in northern California, we placed automatic precipitation samplers at five sites along a N-S transect. At each location, we collected monthly integrated and hourly event-scale rain samples for stable isotope (δ2Hp, δ18Op) analysis beginning in December 2015. Here we present data from two sites, Santa Cruz and Shasta Lake, that are adjacent to sites of ongoing cave monitoring and speleothem record development, and thus can inform our understanding of how ENSO is recorded in the paleo-record. Three large atmospheric river (AR) storms hit northern California in February and March 2016. Precipitation from these ARs comprised 18% of total winter rainfall at both sites. At Shasta Lake monthly-integrated δ2Hp and δ18Op from March are the least negative of the winter, and HYSPLIT back-trajectory analysis suggests a subtropical origin for the March ARs. The most negative monthly integrated δ2Hp and δ18Op at Shasta Lake occur in December, and HYSPLIT back-trajectories suggest Central-North Pacific storm origins. However, monthly δ18Op at Shasta Lake also shows a positive correlation with rain day surface temperature. At Santa Cruz, March δ2Hp and δ18Op are the most negative of the winter, suggesting factors besides vapor source may also influence precipitation isotope values, but there is no clear relationship between monthly δ18Op and surface temperature or rainfall amount. Drip water δ2H and δ18O from both caves are similar to local precipitation but changes are lagged relative to changes in monthly δ2Hp and δ18Op. This modern analysis, which will continue through non-El Niño winters, will help improve speleothem-based ENSO reconstructions in

  9. The Spatial and Temporal Variability of Precipitation in the Western United States

    NASA Astrophysics Data System (ADS)

    Goris, K. J.; Avissar, R.

    2006-12-01

    The capability of the Ocean-Land-Atmosphere Model (OLAM) to simulate global precipitation is evaluated with Global Precipitation Climatology Project (GPCP) Version 2 data. OLAM is a new generation of Earth System Models that has an unstructured grid, which can be set up to simulate designated regions at very-high resolution. The model is run at three different global resolutions (4° x 4°, 2° x 2°, and 1° x 1°). We also run the model with a very-high resolution over the western US that we use together with observationally-based precipitation data to improve hydrometeorological predictions at various space/time scales in that region. Using the Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP), GPCP (version 2 and the 1 degree daily product), the Parameter-elevation Regressions on Independent Slopes Model (PRISM), North American Regional Reanalysis, Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks (PERSIANN), CPC raingauge data, ground-based radar products, and data from the Tropical Rainfall Measuring Mission (TRMM), we quantify time- and location-specific uncertainty for five spatially cohesive subregions of the western US, where the subregions were identified using principal component-based regionalization techniques. We use methods designed for forecast verification and consider both local climatology and specific storm events. Specifically, we use skill scores relative to a given dataset if that dataset were taken to represent the "truth", as well object oriented methods applied to monthly anomaly fields and scale decomposition techniques applied to daily or subdaily data products. Our results suggest that the choice of observational dataset selected for a particular study can affect conclusions regarding model skill. Additionally, the degree of precipitation data uncertainty demonstrates important space/time dependency, which should be considered when evaluating model performance against

  10. Assessing the potential for re-emission of mercury deposited in precipitation from arid soils using a stable isotope

    USGS Publications Warehouse

    Ericksen, J.A.; Gustin, M.S.; Lindberg, S.E.; Olund, S.D.; Krabbenhoft, D.P.

    2005-01-01

    A solution containing 198Hg in the form of HgCl2 was added to a 4 m2 area of desert soils in Nevada, and soil Hg fluxes were measured using three dynamic flux chambers. There was an immediate release of 198Hg after it was applied, and then emissions decreased exponentially. Within the first 6 h after the isotope was added to the soil, ???12 ng m-2 of 198Hg was emitted to the atmosphere, followed by a relatively steady flux of the isotope at 0.2 ?? 0.2 ng m-2 h-1 for the remainder of the experiment (62 days). Over this time, -200 ng m-2 or 2% of the 198Hg isotope was emitted from the soil, and we estimate that ???6% of the isotope would be re-emitted in a year's time. During the experiment, dry deposition of elemental Hg from the atmosphere was measured with an average deposition rate of 0.2 ?? 0.1 ng m-2 h-1. Emission of ambient Hg from the soil was observed after soil wetting with the isotope solution and after a storm event. However, the added moisture from the storm event did not affect 198Hg flux. Results suggest that in this desert environment, where there is limited precipitation, Hg deposited by wet processes is not readily re-emitted and that dry deposition of elemental Hg may be an important process. ?? 2005 American Chemical Society.

  11. Isotopic modeling of the sub-cloud evaporation effect in precipitation.

    PubMed

    Salamalikis, V; Argiriou, A A; Dotsika, E

    2016-02-15

    In dry and warm environments sub-cloud evaporation influences the falling raindrops modifying their final stable isotopic content. During their descent from the cloud base towards the ground surface, through the unsaturated atmosphere, hydrometeors are subjected to evaporation whereas the kinetic fractionation results to less depleted or enriched isotopic signatures compared to the initial isotopic composition of the raindrops at cloud base. Nowadays the development of Generalized Climate Models (GCMs) that include isotopic content calculation modules are of great interest for the isotopic tracing of the global hydrological cycle. Therefore the accurate description of the underlying processes affecting stable isotopic content can improve the performance of iso-GCMs. The aim of this study is to model the sub-cloud evaporation effect using a) mixing and b) numerical isotope evaporation models. The isotope-mixing evaporation model simulates the isotopic enrichment (difference between the ground and the cloud base isotopic composition of raindrops) in terms of raindrop size, ambient temperature and relative humidity (RH) at ground level. The isotopic enrichment (Δδ) varies linearly with the evaporated raindrops mass fraction of the raindrop resulting to higher values at drier atmospheres and for smaller raindrops. The relationship between Δδ and RH is described by a 'heat capacity' model providing high correlation coefficients for both isotopes (R(2)>80%) indicating that RH is an ideal indicator of the sub-cloud evaporation effect. Vertical distribution of stable isotopes in falling raindrops is also investigated using a numerical isotope-evaporation model. Temperature and humidity dependence of the vertical isotopic variation is clearly described by the numerical isotopic model showing an increase in the isotopic values with increasing temperature and decreasing RH. At an almost saturated atmosphere (RH=95%) sub-cloud evaporation is negligible and the isotopic

  12. Precipitation climatology over India: validation with observations and reanalysis datasets and spatial trends

    NASA Astrophysics Data System (ADS)

    Kishore, P.; Jyothi, S.; Basha, Ghouse; Rao, S. V. B.; Rajeevan, M.; Velicogna, Isabella; Sutterley, Tyler C.

    2016-01-01

    Changing rainfall patterns have significant effect on water resources, agriculture output in many countries, especially the country like India where the economy depends on rain-fed agriculture. Rainfall over India has large spatial as well as temporal variability. To understand the variability in rainfall, spatial-temporal analyses of rainfall have been studied by using 107 (1901-2007) years of daily gridded India Meteorological Department (IMD) rainfall datasets. Further, the validation of IMD precipitation data is carried out with different observational and different reanalysis datasets during the period from 1989 to 2007. The Global Precipitation Climatology Project data shows similar features as that of IMD with high degree of comparison, whereas Asian Precipitation-Highly-Resolved Observational Data Integration Towards Evaluation data show similar features but with large differences, especially over northwest, west coast and western Himalayas. Spatially, large deviation is observed in the interior peninsula during the monsoon season with National Aeronautics Space Administration-Modern Era Retrospective-analysis for Research and Applications (NASA-MERRA), pre-monsoon with Japanese 25 years Re Analysis (JRA-25), and post-monsoon with climate forecast system reanalysis (CFSR) reanalysis datasets. Among the reanalysis datasets, European Centre for Medium-Range Weather Forecasts Interim Re-Analysis (ERA-Interim) shows good comparison followed by CFSR, NASA-MERRA, and JRA-25. Further, for the first time, with high resolution and long-term IMD data, the spatial distribution of trends is estimated using robust regression analysis technique on the annual and seasonal rainfall data with respect to different regions of India. Significant positive and negative trends are noticed in the whole time series of data during the monsoon season. The northeast and west coast of the Indian region shows significant positive trends and negative trends over western Himalayas and

  13. Sensitivity of grassland plant community composition to spatial vs. temporal variation in precipitation.

    PubMed

    Cleland, Elsa E; Collins, Scott L; Dickson, Timothy L; Farrer, Emily C; Gross, Katherine L; Gherardi, Laureano A; Hallett, Lauren M; Hobbs, Richard J; Hsu, Joanna S; Turnbull, Laura; Suding, Katharine N

    2013-08-01

    Climate gradients shape spatial variation in the richness and composition of plant communities. Given future predicted changes in climate means and variability, and likely regional variation in the magnitudes of these changes, it is important to determine how temporal variation in climate influences temporal variation in plant community structure. Here, we evaluated how species richness, turnover, and composition of grassland plant communities responded to interannual variation in precipitation by synthesizing long-term data from grasslands across the United States. We found that mean annual precipitation,(MAP) was a positive predictor of species richness across sites, but a positive temporal relationship between annual precipitation and richness was only evident within two sites with low MAP. We also found higher average rates of species turnover in dry sites that in turn had a high proportion of annual species, although interannual rates of species turnover were surprisingly high across all locations. Annual species were less abundant than perennial species at nearly all sites, and our analysis showed that the probability of a species being lost or gained from one year to the next increased with decreasing species abundance. Bray-Curtis dissimilarity from one year to the next, a measure of species composition change that is influenced mainly by abundant species, was insensitive to precipitation at all sites. These results suggest that the richness and turnover patterns we observed were driven primarily by rare species, which comprise the majority of the local species pools at these grassland sites. These findings are consistent with the idea that short-lived and less abundant species are more sensitive to interannual climate variability than longer-lived and more abundant species. We conclude that, among grassland ecosystems, xeric grasslands are likely to exhibit the greatest responsiveness of community composition (richness and turnover) to predicted future

  14. Can weather generation capture precipitation patterns across different climates, spatial scales and under data scarcity?

    PubMed

    Breinl, Korbinian; Di Baldassarre, Giuliano; Girons Lopez, Marc; Hagenlocher, Michael; Vico, Giulia; Rutgersson, Anna

    2017-07-14

    Stochastic weather generators can generate very long time series of weather patterns, which are indispensable in earth sciences, ecology and climate research. Yet, both their potential and limitations remain largely unclear because past research has typically focused on eclectic case studies at small spatial scales in temperate climates. In addition, stochastic multi-site algorithms are usually not publicly available, making the reproducibility of results difficult. To overcome these limitations, we investigated the performance of the reduced-complexity multi-site precipitation generator TripleM across three different climatic regions in the United States. By resampling observations, we investigated for the first time the performance of a multi-site precipitation generator as a function of the extent of the gauge network and the network density. The definition of the role of the network density provides new insights into the applicability in data-poor contexts. The performance was assessed using nine different statistical metrics with main focus on the inter-annual variability of precipitation and the lengths of dry and wet spells. Among our study regions, our results indicate a more accurate performance in wet temperate climates compared to drier climates. Performance deficits are more marked at larger spatial scales due to the increasing heterogeneity of climatic conditions.

  15. Coupled spatial variations in precipitation and long-term erosion rates across the Washington Cascades.

    PubMed

    Reiners, Peter W; Ehlers, Todd A; Mitchell, Sara G; Montgomery, David R

    2003-12-11

    Past studies of tectonically active mountain ranges have suggested strong coupling and feedbacks between climate, tectonics and topography. For example, rock uplift generates topographic relief, thereby enhancing precipitation, which focuses erosion and in turn influences rates and spatial patterns of further rock uplift. Although theoretical links between climate, erosion and uplift have received much attention, few studies have shown convincing correlations between observable indices of these processes on mountain-range scales. Here we show that strongly varying long-term (>10(6)-10(7) yr) erosion rates inferred from apatite (U-Th)/He cooling ages across the Cascades mountains of Washington state closely track modern mean annual precipitation rates. Erosion and precipitation rates vary over an order of magnitude across the range with maxima of 0.33 mm yr(-1) and 3.5 m yr(-1), respectively, with both maxima located 50 km west (windward) of the topographic crest of the range. These data demonstrate a strong coupling between precipitation and long-term erosion rates on the mountain-range scale. If the range is currently in topographic steady state, rock uplift on the west flank is three to ten times faster than elsewhere in the range, possibly in response to climatically focused erosion.

  16. Stable isotopes in monsoon precipitation and water vapour in Nagqu, Tibet, and their implications for monsoon moisture

    NASA Astrophysics Data System (ADS)

    He, Siyuan; Richards, Keith

    2016-09-01

    Understanding climate variations over the Qinghai-Tibetan plateau has become essential because the high plateau sustains various ecosystems and water sources, and impacts on the Asian monsoon system. This paper provides new information from isotopic signals in meteoric water and atmospheric water vapour on the Qinghai-Tibetan Plateau using high frequency observation data over a relatively short period. The aim is to explore temporal moisture changes and annual variations at the onset and during the summer monsoon season at a transitional site with respect to the monsoon influence. Data show that high frequency and short period observations can reveal typical moisture changes from the pre-monsoon to the monsoon seasons (2010), and the large variation in isotopic signals in different years with respect to active/inactive periods during a mature phase of the monsoon (2011), especially inferring from the temporal changes in the d-excess of precipitation and its relationship with δ18O values, when higher d-excess is found in the pre-monsoon precipitation. In this transition zone on a daily basis, δ18O values in precipitation are controlled mainly by the amount of rainfall during the monsoon season, while temperature seems more important before the onset of monsoon. Furthermore, the ;amount effect; is significant for night-time rain events. From comparison of signals in both the precipitation and water vapour, an inconsistent relationship between d-excess values suggests various moisture fluxes are active in a short period. The temporal pattern of isotopic signal change from the onset of the monsoon to the mature monsoon phase provides information about the larger circulation dynamics of the Asian monsoon.

  17. Oxygen isotope content of CO2 in nocturnal ecosystem respiration: 1. Observations in forests along a precipitation transect in Oregon, USA

    NASA Astrophysics Data System (ADS)

    Bowling, D. R.; McDowell, N. G.; Welker, J. M.; Bond, B. J.; Law, B. E.; Ehleringer, J. R.

    2003-12-01

    The oxygen isotope content of nocturnal ecosystem respiration (δ18OR) was examined in forests along a precipitation gradient in Oregon, USA, to determine whether site-to-site variation in δ18OR was more strongly related to variation in δ18O of precipitation or to evaporative processes that isotopically modify water pools within ecosystems. Measurements were made over 4 years at sites ranging in mean annual precipitation from 227 to 2760 mm. There was a gradient in the isotopic content (δ18O) of precipitation, with inland sites receiving isotopically depleted precipitation (more negative δ18O) relative to coastal sites. The δ18O of water in plant xylem generally followed the isotopic pattern of precipitation. Inland forests were drier than coastal forests, leading to a gradient in the vapor pressure deficit of air that caused isotopic enrichment of soil and leaf water. The enriched soil and leaf water pools influenced the isotopic composition of respired CO2, leading to variation in observed δ18OR (Keeling-plot intercepts). Keeling plots with non-significant (p > 0.01) regression slopes and those sampled over a time period (t) greater than 5 hours yielded unacceptably high uncertainty in δ18OR. The range of observed δ18OR was 21.7 to 35.3‰ (VSMOW), with variation within a single site as large as 10.7‰ (range 24.2 to 34.9‰ at different sites). The results suggested a trend of more positive δ18OR at inland sites relative to those nearer the coast, indicating that fractionation due to evaporative enrichment overshadowed the original isotopic composition of precipitation as a first order control on δ18OR.

  18. Analysis of the interdecadal variability of summer precipitation in central Japan using a reconstructed 106 year long oxygen isotope record from tree ring cellulose

    NASA Astrophysics Data System (ADS)

    Kurita, Naoyuki; Nakatsuka, Takeshi; Ohnishi, Keiko; Mitsutani, Takumi; Kumagai, Tomo'omi

    2016-10-01

    We present a unique proxy for reconstructing the interannual variability of summer precipitation associated with the quasi-stationary front (Baiu front) in central Japan. The rainfall from the Baiu front has a relatively lower oxygen isotopic composition than other types of nonfrontal precipitation. The variability in the oxygen isotopes in summer rainfall is closely related to the Baiu frontal activity. In this study we used a mechanistic tree ring isotope model to reconstruct a 106 year long oxygen isotopic composition of precipitation during the early rainy season (June) based on the oxygen isotopic compositions of the annual rings of Chamaecyparis obtusa Endl trees from central Japan. The year-to-year variations of the isotopes over the most recent 25 years are associated with several teleconnection patterns that often lead to the Baiu precipitation anomalies in central Japan (such as the Pacific-Japan (PJ) pattern, Silk Road pattern, and wave train pattern along the polar jet). Yet none of these external forcing mechanisms apply further back in time. From the 1950s to 1980s, the interannual isotopic variability is predominantly related to local factors such as anomalous intensification/weakening of the Bonin High. Before the 1950s, the variability of the oxygen isotopic composition of precipitation is mainly associated with a wave train pattern along the polar jet. The isotopic variability is predominantly linked to the PJ pattern, while the PJ index is correlated with El Niño-Southern Oscillation. These findings suggest that the teleconnection patterns influencing Baiu precipitation variability vary according to interdecadal time scales during the twentieth century.

  19. Carbon and oxygen isotope ratios in wood constituents of Pinus halepensis as indicators of precipitation, temperature and vapour pressure deficit

    NASA Astrophysics Data System (ADS)

    Ferrio, J. P.; Voltas, J.

    2005-04-01

    Carbon and oxygen isotope compositions (δ13C, δ18O) in tree rings have been shown to bear relevant climatic signals. However, little is known about the interrelationship between both isotopes in wood constituents for species from other than relatively wet climates. We hypothesized that in a species adapted to temporary droughts (e.g. Pinus halepensis Mill.) the signal derived from δ18O in precipitation would be hidden by the strong variability in leaf transpirative enrichment. To test this assumption, we compared the effect of precipitation, temperature and vapour pressure deficit (VPD) on δ18O and δ13C along 23 sites covering the ecological range for this species. We extracted the cores from the south side of four to six adult dominant trees per aspect (north/south) within each site. For each aspect and site, fragments of the period 1975 1999 were pooled and milled to a fine powder. To further test the postulated need for cellulose purification in the assessment of climatic information, we studied these relationships in whole and extracted wood, holocellulose and lignin. In all wood fractions, δ13C was related to annual precipitation [r=-0.58 (P< 0.01) to -0.78 (P< 0.001)] and VPD [r= 0.53 (P< 0.01) to 0.57 (P< 0.01)]. In contrast, for δ18O only holocellulose showed consistent relationships with climatic data, being strongly significant for VPD [r= 0.66 (P< 0.001)]. However, it was unrelated to modelled δ18O in precipitation, confirming that transpirative enrichment (driven by VPD) dampened the source signal in P. halepensis. The relationships between δ13C and δ18O were generally poor, regardless of the wood constituent, suggesting that although both variables were somewhat related to transpirative demand, they were relatively independent. This was further confirmed by building stepwise models using both isotopes to predict annual and seasonal precipitation [r2= 0.34 (P< 0.01) to 0.68 (P< 0.001)], temperature [r2= 0.15 (P< 0.05) to 0.37 (P< 0.01)] and

  20. Controls on the isotopic composition of surface water and precipitation in the Northern Andes, Colombian Eastern Cordillera

    NASA Astrophysics Data System (ADS)

    Saylor, Joel E.; Mora, Andrés; Horton, Brian K.; Nie, Junsheng

    2009-12-01

    Empirical datasets provide the constraints on the variability and causes of variability in stable isotope compositions (δD or δ 18O) of surface water and precipitation that are essential not only for models of modern and past climate but also for investigations of paleoelevation. This study presents stable isotope data for 76 samples from four elevation transects and three IAEA GNIP stations in the Eastern Cordillera of Colombia and the northern Andean foreland. These data are largely consistent with theories of stable isotope variability developed based on a global dataset. On a monthly basis, the precipitation-amount effect exerts the dominant control on δD p and δ 18O p values at the IAEA GNIP stations. At the Bogotá station (2547 m), the δD p and δ 18O p values vary seasonally, with isotopic minima correlating with maxima in precipitation-amount. Although surface water samples from Eastern Cordilleran streams and rivers fall on the Global Meteoric Water Line, samples from three of four lakes (2842-3459 m) have evaporatively elevated δD sw and δ 18O sw values. The IAEA GNIP station data averaged over multiple years, combined with stream and river water data, define vertical lapse rates of -1.8‰ km -1 for Δδ 18O and -14.6‰ km -1 for ΔδD, and are a close fit to a common thermodynamically based Rayleigh distillation model. Elevation uncertainties for these relationships are also evaluated. Comparison of this Colombian dataset with the elevation uncertainties generated by the thermodynamically based model shows that the model underestimates uncertainty at high Δδ 18O and ΔδD values while overestimating it for low Δδ 18O and ΔδD values. This study presents an independent, empirical assessment of stable isotope-based elevation uncertainties for the northern Andes based on a dataset of sufficient size to ensure statistical integrity. These vertical lapse rates and associated uncertainties form the basis for stable isotope paleoelevation studies

  1. Isotopic signature of extreme precipitation events in the western U.S. and associated phases of Arctic and tropical climate modes

    NASA Astrophysics Data System (ADS)

    McCabe-Glynn, Staryl; Johnson, Kathleen R.; Strong, Courtenay; Zou, Yuhao; Yu, Jin-Yi; Sellars, Scott; Welker, Jeffrey M.

    2016-08-01

    Extreme precipitation events, commonly associated with "Atmospheric Rivers," are projected to increase in frequency and severity in western North America; however, the intensity and landfall position are difficult to forecast accurately. As the isotopic signature of precipitation has been widely utilized as a tracer of the hydrologic cycle and could potentially provide information about key physical processes, we utilize both climate and precipitation isotope data to investigate these events in California from 2001 to 2011. Although individual events have extreme isotopic signatures linked to associated circulation anomalies, the composite across all events unexpectedly resembles the weighted mean for the entire study period, reflecting diverse moisture trajectories and associated teleconnection phases. We document that 90% of events reaching this location occurred during the negative Arctic Oscillation, suggesting a possible link with higher-latitude warming. We also utilize precipitation data of extreme precipitation events across the entire western U.S. to investigate the relationships between key tropical and Arctic climate modes known to influence precipitation in this region. Results indicate that the wettest conditions occur when the negative Arctic Oscillation, negative Pacific/North American pattern, and positive Southern Oscillation are in sync and that precipitation has increased in the southwestern U.S. and decreased in the northwestern U.S. relative to this phase combination's 1979-2011 climatology. Furthermore, the type of El Niño-Southern Oscillation event, Central Pacific or Eastern Pacific, influences the occurrence, landfall location, and isotopic composition of precipitation.

  2. Multicentury Reconstruction of Precipitations (1300-2014) in Eastern Canada from Tree-Ring Width and Carbon and Oxygen Isotopes

    NASA Astrophysics Data System (ADS)

    Giguère, Claudie; Boucher, Étienne; Bergeron, Yves

    2016-04-01

    Tree ring series enabling long hydroclimatic reconstructions are scarce in Northeastern America, mostly because most boreal species are rather thermo-dependant. Here we propose a new multi-proxy analysis (tree-ring, δ13C and δ18O) from one of the oldest Thuja occidentalis population in NE America (lake Duparquet, Quebec). These rare precipitation-sensitive, long-living trees (> 800 years) grow on xeric rocky shores and their potential for paleo-hydroclimatic reconstructions (based on ring widths solely) was previously assessed. The objectives of this study are twofold i) to strengthen the hydroclimatic signal of this long tree-ring chronology by adding analysis of stable isotope ratios (δ13C and δ18O) and ii) to reconstruct summer precipitation back to 1300 AD, which will represent, by far, the longest high-resolution hydroclimatic reconstruction in this region. A tree-ring chronology was constructed from 61 trees sampled in standing position. Eleven trees were also sampled to produce pooled carbon and oxygen isotope chronologies (annually resolved) with a replication of five to six trees per year. Signal analysis (correlation between climatic data and proxy values) confirms that growth is positively influenced by spring precipitations (May-June), while δ13C is negatively correlated to summer precipitation (June to August) and positively to June temperature. Adding δ18O analysis will strengthen the signal even more, since wood cellulose should be enriched in δ18O when high evapotranspiration conditions prevail. Based on a multi-proxy approach, a summer precipitation reconstruction was developed and compared to other temperature reconstructions from this region as well as to southernmost hydroclimatic reconstructions (e.g. Cook et al). A preliminary analysis of external and internal forcing is proposed in conclusion.

  3. Preserving spatial linear correlations between neighboring stations in simulating daily precipitation using extended Markov models

    NASA Astrophysics Data System (ADS)

    Ababaei, Behnam; Sohrabi, Teymour; Mirzaei, Farhad

    2014-10-01

    Most stochastic weather generators have their focus on precipitation because it is the most important variable affecting environmental processes. One of the methods to reproduce the precipitation occurrence time series is to use a Markov process. But, in addition to the simulation of short-term autocorrelations in one station, it is sometimes important to preserve the spatial linear correlations (SLC) between neighboring stations as well. In this research, an extension of one-site Markov models was proposed to preserve the SLC between neighboring stations. Qazvin station was utilized as the reference station and Takestan (TK), Magsal, Nirougah, and Taleghan stations were used as the target stations. The performances of different models were assessed in relation to the simulation of dry and wet spells and short-term dependencies in precipitation time series. The results revealed that in TK station, a Markov model with a first-order spatial model could be selected as the best model, while in the other stations, a model with the order of two or three could be selected. The selected (i.e., best) models were assessed in relation to preserving the SLC between neighboring stations. The results depicted that these models were very capable in preserving the SLC between the reference station and any of the target stations. But, their performances were weaker when the SLC between the other stations were compared. In order to resolve this issue, spatially correlated random numbers were utilized instead of independent random numbers while generating synthetic time series using the Markov models. Although this method slightly reduced the model performances in relation to dry and wet spells and short-term dependencies, the improvements related to the simulation of the SLC between the other stations were substantial.

  4. The spatial scale distribution of extreme precipitation synchronizations around the globe

    NASA Astrophysics Data System (ADS)

    Boers, Niklas; Rheinwalt, Aljoscha; Goswami, Bedartha; Bookhagen, Bodo; Kurths, Jürgen

    2016-04-01

    Extreme precipitation events (EPEs) on the earth's surface occur with varying degrees of synchronization, depending on spatial distances and the governing atmospheric processes. The spatial scales across which such EPEs synchronize around the globe, as well as the dependence of these interaction distances on the event magnitudes, have not yet been rigorously addressed in the literature. Here, we address these questions on the basis of a globally gridded, high-resolution satellite dataset (TRMM 3B42) of 576 000 daily precipitation time series for the time period 1998 - 2014. EPE synchronizations around the globe are in our approach represented as spatially embedded functional networks, and the object we are interested in is the probability distribution of spatial link lengths in these networks. First, it is shown how Bayes' Theorem can be employed to derive a scheme to correct for spatial embedding effects in node-based network measures from this distribution. We then discuss the problem of multiple comparisons immanent to all functional network approaches as soon as the statistical significance of single links is addressed. A statistical method is proposed to distinguish physical network links from those occurring by chance due to multiple comparisons, which is generally applicable to spatially embedded functional networks. Finally, a combination of maximum likelihood estimation and Markov Chain Monte Carlo sampling is used to find the most likely functional form of the spatial length distributions of physical EPE synchronizations. We find that the spatial distances of physical EPE synchronizations are distributed according to an exponentially truncated power law. Furthermore, it is shown that the distributions' tail becomes nonlinearly heavier the stronger the events are, providing statistical evidence for the importance of atmospheric teleconnections for the most extreme events. Since this implies that the most extreme events are typically part of particularly

  5. Chemistry and isotopic composition of precipitation and surface waters in Khumbu valley (Nepal Himalaya): N dynamics of high elevation basins.

    PubMed

    Balestrini, Raffaella; Polesello, Stefano; Sacchi, Elisa

    2014-07-01

    We monitored the chemical and isotopic compositions of wet depositions, at the Pyramid International Laboratory (5050 ma.s.l.), and surrounding surface waters, in the Khumbu basin, to understand precipitation chemistry and to obtain insights regarding ecosystem responses to atmospheric inputs. The major cations in the precipitation were NH4(+) and Ca(2+), whereas the main anion was HCO3(-), which constituted approximately 69% of the anions, followed by NO3(-), SO4(2-) and Cl(-). Data analysis suggested that Na(+), Cl(-) and K(+) were derived from the long-range transport of marine aerosols. Ca(2+), Mg(2+) and HCO3(-) were related to rock and soil dust contributions and the NO3(-) and SO4(2-) concentrations were derived from anthropogenic sources. Furthermore, NH4(+) was derived from gaseous NH3 scavenging. The isotopic composition of weekly precipitation ranged from -1.9 to -23.2‰ in δ(18)O, and from -0.8 to -174‰ in δ(2)H, with depleted values characterizing the central part of the monsoon period. The chemical composition of the stream water was dominated by calcite and/or gypsum dissolution. However, the isotopic composition of the stream water did not fully reflect the composition of the monsoon precipitation, which suggested that other water sources contributed to the stream flow. Precipitation contents for all ions were the lowest ones among those measured in high elevation sites around the world. During the monsoon periods the depositions were not substantially influenced by anthropogenic inputs, while in pre- and post-monsoon seasons the Himalayas could not represent an effective barrier for airborne pollution. In the late monsoon phase, the increase of ionic contents in precipitation could also be due to a change in the moisture source. The calculated atmospheric N load (0.30 kg ha(-1) y(-1)) was considerably lower than the levels that were measured in other high-altitude environments. Nevertheless, the NO3(-) concentrations in the surface waters

  6. Identifying Energy Sources Supporting Coastal Fish; Spatial Differences Revealed by Stable Isotope Ratios

    EPA Science Inventory

    The goal of our research is to identify energy inputs that support production of young fishes in coastal wetland ecosystem food webs using stable isotopes. The data demonstrate that strong spatial heterogeneity exists in this food web, implying that the energy sources supporting...

  7. Identifying Energy Sources Supporting Coastal Fish; Spatial Differences Revealed by Stable Isotope Ratios

    EPA Science Inventory

    The goal of our research is to identify energy inputs that support production of young fishes in coastal wetland ecosystem food webs using stable isotopes. The data demonstrate that strong spatial heterogeneity exists in this food web, implying that the energy sources supporting...

  8. Analyzing Spatial and Temporal Variation in Precipitation Estimates in a Coupled Model

    NASA Astrophysics Data System (ADS)

    Tomkins, C. D.; Springer, E. P.; Costigan, K. R.

    2001-12-01

    the LADHS and RAMS cumulative precipitation reveal a disassociation over time, with R equal to 0.74 at day eight and R equal to 0.52 at day 31. Linear correlation coefficients (Pearson) returned a stronger initial correlation of 0.97, decreasing to 0.68. The standard deviations for the 2500 LADHS cells underlying each 5km RAMS cell range from 8 mm to 695 mm in the Sangre de Cristo Mountains and 2 mm to 112 mm in the San Luis Valley. Comparatively, the standard deviations of the RAMS estimates in these regions are 247 mm and 30 mm respectively. The LADHS standard deviations provide a measure of the variability introduced through the downscaling routine, which exceeds RAMS regional variability by a factor of 2 to 4. The coefficient of variation for the average LADHS grid cell values and the RAMS cell values in the Sangre de Cristo Mountains are 0.66 and 0.27, respectively, and 0.79 and 0.75 in the San Luis Valley. The coefficients of variation evidence the uniformity of the higher precipitation estimates in the mountains, especially for RAMS, and also the lower means and variability found in the valley. Additionally, Kolmogorov-Smirnov tests indicate clear spatial and temporal differences in mean simulated precipitation across the grid.

  9. Atmospheric Moisture Budget and Spatial Resolution Dependence of Precipitation Extremes in Aquaplanet Simulations

    SciTech Connect

    Yang, Qing; Leung, Lai-Yung R.; Rauscher, Sara; Ringler, Todd; Taylor, Mark

    2014-05-01

    data aggregation effect in omega, thermodynamic changes become relatively significant in offsetting the effect of dynamics leading to reduce differences between the simulated and aggregated results. Compared to MPAS, the simulated stronger vertical motion with HOMME also results in larger resolution dependency. Compared to the simulation at fine resolution, the vertical motion during extremes is insufficiently resolved/parameterized at the coarser resolution even after accounting for the natural reduction in variability with coarser resolution, and this is more distinct in the simulation with HOMME. To reduce uncertainties in simulated precipitation extremes, future development in cloud parameterizations must address their sensitivity to spatial resolution as well as dynamical cores.

  10. Precipitation Variability and Analysis of Satellite - Rainfall Using a Spatial Synoptic Classification

    NASA Astrophysics Data System (ADS)

    Greene, John Scott

    The objective of this research is to use a new synoptic-scale climatological classification procedure to develop a more thorough understanding of precipitation variation to facilitate the calibration and validation of satellite-derived rainfall estimation models. An automated classification procedure based on "seed" day identification of synoptic events and discriminant analysis makes possible the evaluation of the frequency and modification of air masses across a large region. Seed days, which represent the mean characteristics of the various synoptic types, are selected for each type at each site using an automated iterative procedure. The classification was used to identify occurrences of six air masses (dry polar, dry temperate, dry tropical, moist polar, moist temperate, and moist tropical) at 126 locations east of the Rocky Mountains for winter and summer from 1961-1990. An analysis of the results indicates that the air mass patterns identified are both spatially and temporally consistent. Maps of air mass frequencies and afternoon temperatures and dew points illustrate the modification rates of each air mass. For example, the modification of dry polar in winter is much faster than moist tropical in summer. The homogeneous land cover and the relatively uniform solar insolation help explain the reduced modification rates of the air masses during summer. Precipitation occurrence and intensity relationships were evaluated for each air mass. Significant convective activity is identifiable during both moist tropical and moist temperate in summer. Generally speaking, moist tropical exhibits more convective, air-mass thunderstorm-type precipitation, while moist temperate is more often associated with frontal stratiform precipitation. Although bulk-statistical satellite algorithms appear to be the most appropriate methods to produce rainfall estimates averaged over large areas, they have not been validated when discriminated by synoptic pattern. Thus, the determined

  11. An exploratory study of spatial annual maximum of monthly precipitation in the northern region of Portugal

    NASA Astrophysics Data System (ADS)

    Prata Gomes, D.; Neves, M. M.; Moreira, E.

    2016-08-01

    Adequately analyzing and modeling the extreme rainfall events is of great importance because of the effects that their magnitude and frequency can have on human life, agricultural productivity and economic aspects, among others. A single extreme event may affect several locations, and their spatial dependence has to be appropriately taken into account. Classical geostatistics is a well-developed field for dealing with location referenced data, but it is largely based on Gaussian processes and distributions, that are not appropriate for extremes. In this paper, an exploratory study of the annual maximum of monthly precipitation recorded in the northern area of Portugal from 1941 to 2006 at 32 locations is performed. The aim of this paper is to apply max-stable processes, a natural extension of multivariate extremes to the spatial set-up, to briefly describe the models considered and to estimate the required parameters to simulate prediction maps.

  12. Spatial similarity and transferability of analog dates for precipitation downscaling over France

    NASA Astrophysics Data System (ADS)

    Chardon, Jérémy; Hingray, Benoit; Favre, Anne-Catherine; Autin, Philémon; Gailhard, Joël; Zin, Isabella; Obled, Charles

    2014-05-01

    High-resolution weather scenarios generated for climate change impact studies from the output of climate models have to be spatially coherent. Analog Models (AMs) have a high potential to generate such scenarios. For each prediction day, they use as scenario the weather observed for days in a historical archive that are analog according to different predictors. When a same 'analog date' is chosen for a prediction at several sites, the spatial coherency is automatically fulfilled. The optimal predictors and next the optimal analog dates are however expected to depend on the location for which the prediction has to be made. In this study, a set of 8,981 locally AMs - specifically optimized for the probabilistic prediction of 8,981 local precipitation 'stations' over France - is used to explore the two following questions: How does the domain-optimized AM perform for precipitation prediction at another location if the analogy domain used to identify the analog dates (in terms of spatial shape of 1000 and 500 hPa geopotential fields) is optimized to predict precipitation at a given location (question of transferability)? To what extent are the analog dates derived from a first AM domain-optimized for a given location similar to those of a second AM domain-optimized for a second location (question of similarity)? The mean similarity level of analog dates obtained from two different AMs is assessed with the percentage of issued predictions for which the number of identical analog dates is larger to a given percentage threshold. The spatial transferability is assessed with the loss of prediction performance - expressed by the Continuous Ranked Probability Skill Score (CRPSS) - when the transposed AM is used instead of the locally domain-optimized one. In our case, the mean similarity level is very low excepted when the two locations are very close. The spatial transferability of the optimal analog dates obtained for a given location is conversely very wide: when they are

  13. Precipitation source inferred from stable isotopic composition of Pleistocene groundwater and carbonate deposits in the western desert of Egypt.

    SciTech Connect

    Sultan, M.; Sturchio, N.; Hassan, F. A.; Abdel, M.; Hamdan, R.; Mahmood, A. M.; Alfy, Z. E.; Stein, T.; Environmental Research; Univ. Coll. London; Cairo Univ.; Ain Shams Univ.; Egyptian Geological survey and Mining Authority; Washington Univ.

    1997-01-01

    An Atlantic source of precipitation can be inferred from stable isotopic data (H and O) for fossil groundwaters and uranium-series-dated carbonate spring deposits from oases in the Western Desert of Egypt. In the context of available stable isotopic data for fossil groundwaters throughout North Africa, the observed isotopic depletions ({delta}D -72 to -81{per_thousand}; {delta}{sup 18}O -10.6 to -11.5{per_thousand}) of fossil ({ge}32,000 yr B.P.) groundwaters from the Nubian aquifer are best explained by progressive condensation of water vapor from paleowesterly wet oceanic air masses that traveled across North Africa and operated at least as far back as 450,000 yr before the present. The values of {delta}{sup 18}O (17.1 to 25.9{per_thousand}) for 45,000- to >450,000-yr-old tufas and vein-filling calcite deposits from the Kharga and Farafra Oases are consistent with deposition from groundwaters having oxygen isotopic compositions similar to those of fossil groundwaters sampled recently at these locations.

  14. Factors controlling the growth rate, carbon and oxygen isotope variation in modern calcite precipitation in a subtropical cave, Southwest China

    NASA Astrophysics Data System (ADS)

    Pu, Junbing; Wang, Aoyu; Shen, Licheng; Yin, Jianjun; Yuan, Daoxian; Zhao, Heping

    2016-04-01

    A prerequisite for using cave speleothems to reconstruct palaeoenvironmental conditions is an accurate understanding of specific factors controlling calcite growth, in particular the isotopic partitioning of oxygen (δ18O) and carbon (δ13C) which are the most commonly used proxies. An in situ monitoring study from April 2008 to September 2009 at Xueyu Cave, Chongqing, SW China, provides insight into the controls on calcite growth rates, drip water composition, cave air parameters and δ18O and δ13C isotopic values of modern calcite precipitation. Both cave air PCO2 and drip water hydrochemical characteristics show obvious seasonality driven by seasonal changes in the external environment. Calcite growth rates also display clear intra-annual variation, with the lowest values occurring during wet season and peak values during the dry season. Seasonal variations of calcite growth rate are primarily controlled by variations of cave air PCO2 and drip water rate. Seasonal δ18O-VPDB and δ13C-VPDB in modern calcite precipitates vary, with more negative values in the wet season than in the dry season. Strong positive correlation of δ18O-VPDB vs. δ13C-VPDB is due to simultaneous enrichment of both isotopes in the calcite. This correlation indicates that kinetic fractionation occurs between parent drip water and depositing calcite, likely caused by the variations of cave air PCO2 and drip rate influenced by seasonal cave ventilation. Kinetic fractionation amplifies the equilibrium fractionation value of calcite δ18O (by ∼1.5‰) and δ13C (by ∼1.7‰), which quantitatively reflects surface conditions during the cave ventilation season. These results indicate that the cave monitoring of growth rate and δ18O and δ13C of modern calcite precipitation are necessary in order to use a speleothem to reconstruct palaeoenvironment.

  15. Global spatial distributions of nitrogen and carbon stable isotope ratios of modern human hair.

    PubMed

    Hülsemann, Frank; Lehn, Christine; Schneider, Sabine; Jackson, Glen; Hill, Sarah; Rossmann, Andreas; Scheid, Nicole; Dunn, Philip J H; Flenker, Ulrich; Schänzer, Wilhelm

    2015-11-30

    Natural stable carbon (δ(13)C) and nitrogen isotope ratios (δ(15)N) of humans are related to individual dietary habits and environmental and physiological factors. In forensic science the stable isotope ratios of human remains such as hair and nail are used for geographical allocation. Thus, knowledge of the global spatial distribution of human δ(13)C and δ(15)N values is an essential component in the interpretation of stable isotope analytical results. No substantial global datasets of human stable isotope ratios are currently available, although the amount of available (published) data has increased within recent years. We have herein summarised the published data on human global δ(13)C andδ(15)N values (around 3600 samples) and added experimental values of more than 400 additional worldwide human hair and nail samples. In order to summarise isotope ratios for hair and nail samples correction factors were determined. The current available dataset of human stable isotope ratios is biased towards Europe and North America with only limited data for countries in Africa, Central and South America and Southeast Asia. The global spatial distribution of carbon isotopes is related to latitude and supports the fact that human δ(13)C values are dominated by the amount of C4 plants in the diet, either due to direct ingestion as plant food, or by its use as animal feed. In contrast, the global spatial distribution of human δ(15)N values is apparently not exclusively related to the amount of fish or meat ingested, but also to environmental factors that influence agricultural production. There are still a large proportion of countries, especially in Africa, where there are no available data for human carbon and nitrogen isotope ratios. Although the interpretation of modern human carbon isotope ratios at the global scale is quite possible, and correlates with the latitude, the potential influences of extrinsic and/or intrinsic factors on human nitrogen isotope ratios

  16. Silicon isotope fractionation during silica precipitation from hot-spring waters: Evidence from the Geysir geothermal field, Iceland

    NASA Astrophysics Data System (ADS)

    Geilert, Sonja; Vroon, Pieter Z.; Keller, Nicole S.; Gudbrandsson, Snorri; Stefánsson, Andri; van Bergen, Manfred J.

    2015-09-01

    This study aims to explore the extent and controls of silicon isotope fractionation in hot spring systems of the Geysir geothermal area (Iceland), a setting where sinter deposits are actively formed. The δ30Si values of dissolved silica measured in the spring water and sampling sites along outflowing streams, covering a temperature range between 20 and 100 °C, were relatively constant around +0.2‰, whereas the δ30Si signatures of associated opaline sinters from the streambeds were between -0.1‰ and -4.0‰, becoming progressively more negative in the downstream parts of the aprons. Here, the deposited sinters represent some of the most 30Si depleted abiotically produced terrestrial materials documented to date. Compared to the data reported for Icelandic basalts, considered to be the source of the silicon, the δ30Si values of the fluids and sinter deposits are higher and lower, respectively. The resulting values for apparent solid-water isotope fractionation (Δ30Sisolid-water) decreased with decreasing temperature from ca. -0.7‰ at ∼80 °C to -3.7‰ at ∼20 °C, locally down to -4.4‰. This temperature relationship was reproducible in each of the investigated hot spring systems and is qualitatively consistent with recent findings in laboratory experiments on kinetic fractionation for a flowing fluid. However, the apparent fractionation magnitudes observed in the field are ca. -2‰ more negative and thus significantly larger. We infer that solid-water silicon isotope fractionation during deposition of amorphous silica from a flowing fluid correlates inversely with temperature, but is essentially a function of the precipitation rate, such that the fractionation factor decreases with increasing rate. As an important corollary, the effective fractionation behavior during precipitation of silica from saturated solutions is a system-dependent feature, which should be taken into account when using silicon isotopes for paleo-environmental reconstructions.

  17. Calcium and strontium isotope fractionation during precipitation from aqueous solutions as a function of temperature and reaction rate; II. Aragonite

    NASA Astrophysics Data System (ADS)

    AlKhatib, Mahmoud; Eisenhauer, Anton

    2017-07-01

    In order to study Strontium (Sr) partitioning and isotope fractionation of Sr and Calcium (Ca) in aragonite we performed precipitation experiments decoupling temperature and precipitation rates (R∗, μmol/m2 h) in the interval of about 2.3-4.5 μmol/m2 h. Aragonite is the only pure solid phase precipitated from a stirred solutions exposed to an atmosphere of NH3 and CO2 gases throughout the spontaneous decomposition of (NH4)2CO3. The order of reaction with respect to Ca ions is one and independent of temperature. However, the order of reaction with respect to the dissolved inorganic carbon (DIC) is temperature dependent and decreases from three via two to one as temperature increases from 12.5 and 25.0 to 37.5 °C, respectively. Strontium distribution coefficient (DSr) increases with decreasing temperature. However, R∗ responds differently depending on the initial Sr/Ca concentration and temperature: at 37.5 °C DSr increase as a function of increasing R∗ but decrease for 12.5 and 25 °C. Not seen at 12.5 and 37.5 °C but at 25 °C the DSr-R∗ gradient is also changing sign depending on the initial Sr/Ca ratio. Magnesium (Mg) adsorption coefficient between aragonite and aqueous solution (DMg) decreases with temperature but increases with R∗ in the range of 2.4-3.8 μmol/m2 h. Strontium isotope fractionation (Δ88/86Sraragonite-aq) follows the kinetic type of fractionation and become increasingly negative as a function of R∗ for all temperatures. In contrast Ca isotope fractionation (Δ44/40Caaragonite-aq) shows a different behavior than the Sr isotopes. At low temperatures (12.5 and 25 °C) Ca isotope fractionation (Δ44/40Caaragonite-aq) becomes positive as a function of R∗. In contrast, at 37.5 °C and as a function of increasing R∗ the Δ44/40Caaragonite-aq show a Sr type like behavior and becomes increasingly negative. Concerning both the discrepant behavior of DSr as a function of temperature as well as for the Ca isotope fractionation as a

  18. A Stochastic Technique for Error Correction and Spatial Downscaling of Global Gridded Precipitation Products

    NASA Astrophysics Data System (ADS)

    Seyyedi, H.; Kaheil, Y.; Anagnostou, E. N.; McCollum, J.; Beighley, E.

    2013-12-01

    Deriving flood maps requires an accurate characterization of precipitation variability at high spatio-temporal resolution. Most of the available global-scale gridded precipitation products are available at resolutions (e.g., 25 km) not directly applicable to flood modeling. An error correction and spatial downscaling method based on a two-dimensional satellite rainfall error model (SREM2D) is tested in this study based on a long-term (2001-2010) dataset. Specifically, the model is applied on two rainfall datasets: a satellite precipitation product (TRMM-3B42.V7 at 0.25 degree) and a global land-atmosphere re-analysis product (GLDAS-CLM at 1 degree), to produce error corrected rainfall ensembles at 0.05 degree spatial resolution. The NCEP hourly, 4-km resolution multi-sensor precipitation product (WSR-88D stage IV gauge-adjusted radar-rainfall product) is used as the reference rainfall dataset. The Hillslope River Routing (HRR) hydrologic model is forced with the downscaled ensemble rainfall data to produce an ensemble of runoff values. The Susquehanna River basin is the study area, consisting of 1000 sub-basins ranging from 39 to 67,000 square kilometers including complex terrain and high latitude locations. There are 437 significant storm events selected over the study area based on the 10-year database. The analysis performed is based on 60 percent of events in each season kept for model calibration and 40 percent for validation. The statistical analysis consists of two parts: (1) evaluation of error metrics (relative standard deviation and efficiency coefficient) to quantify improvements in rainfall and runoff simulations as function of basin size and storm severity, and (2) ensemble verification (exceedance probability and mean uncertainty ratio) of the rainfall and runoff ensembles to assess the accuracy of the ensemble-based uncertainty characterization. The study investigates how well the ensemble of downscaled and error-corrected rainfall data performs

  19. Stochastic modelling of spatially and temporally consistent daily precipitation time-series over complex topography

    NASA Astrophysics Data System (ADS)

    Keller, Denise E.; Fischer, Andreas M.; Frei, Christoph; Liniger, Mark A.; Appenzeller, Christof; Knutti, Reto

    2014-05-01

    There is a growing demand for high-resolution precipitation time-series at the local scale that are both consistent in time and in space. This is of high relevance for climate impact models that are sensitive to averaged rainfall amount over a specific region and over a multi-day period (e.g. for modeling river runoff regimes). In this regard, weather generators (WGs) calibrated at multiple sites, are an appealing technique that allow the simulation of synthetic series of unlimited length taking into account the spatio-temporal correlation structure. To date, only a few multi-site WGs have been documented in the literature and those that exist have rarely been tested for a topography as complex as the Alps. It is the aim of this study to fill this gap. Here, we present results from multi-site precipitation simulations with a generator that has been inspired by Wilks (1998). In essence, it is a Richardson-type WG that additionally takes into account the spatial correlation structure between all the station pairs. A first-order two-state Markov process is chosen to simulate daily precipitation occurrences, while precipitation amounts are re-sampled from a mixture model of two exponential distributions fitted at individual stations. Our multi-site WG is tested and evaluated here at the example of the hydrological catchment "Thur" in the Swiss Alps for the time-period 1961-2011 and on a monthly basis. In the catchment eight meteorological stations (from MeteoSwiss) are considered at which artificial time-series with the respective spatio-temporal dependence structure are simulated. The eight measurement sites are evenly distributed over the catchment, representing the complex topographical and associated precipitation characteristics. The study reveals first that our stochastic model is able to generate time-series that well represent the annual cycle of the precipitation statistics, such as mean wet day frequency and intensity as well as accumulated precipitation

  20. Halite precipitation rates in the Dead Sea: Seasonal and spatial variations and their limnological and geological implications

    NASA Astrophysics Data System (ADS)

    Lensky, Nadav G.; Arnon, Ali; Sirota, Ido

    2015-04-01

    Halite precipitates from natural hypersaline brines when supersaturation is achieved. Negative water balance (evaporation > inflows) causes salinity increase and may cause continuous halite precipitation. The dependence of halite solubility on both temperature and salinity results in a complicated seasonal and spatial (depth) variations of halite precipitation in a stratified hypersaline lake. The seasonal thermo-haline stratification and the fluxes of heat, water and salt - dictates the spatial and temporal variations in the degree of halite saturation and the rate of precipitation. We present in situ observational data set from the Dead Sea, a hypersaline terminal lake in a negative water balance that actively precipitates halite. The data set includes the seasonal and depth variations of the following quantities: (i) halite precipitation rate, (ii) temperature, (iii) salinity, (iv) solubility, and (v) video documentation of active halite precipitation. We present the seasonal and depth variations of the above quantities along a year of observations. We discuss the seasonal variations of the atmospheric forcing - the heat and water fluxes, and the response of the lake - thermo-haline stratification and the precipitation of halite along the water column. We also discuss the role of diapycnal flux on the precipitation of halite and the salt fluxes. Geological implications on the lateral extent and thickness variations of evaporitic layers in evaporitic environments is also discussed.

  1. On the spatial and temporal variability of ENSO precipitation and drought teleconnection in mainland Southeast Asia

    NASA Astrophysics Data System (ADS)

    Räsänen, Timo A.; Lindgren, Ville; Guillaume, Joseph H. A.; Buckley, Brendan M.; Kummu, Matti

    2016-09-01

    The variability of the hydroclimate over mainland Southeast Asia is strongly influenced by the El Niño-Southern Oscillation (ENSO), which has been linked to severe droughts and floods that profoundly influence human societies and ecosystems alike. Although the significance of ENSO is well understood, there are still limitations in the understanding of its effects on hydroclimate, particularly with regard to understanding the spatio-temporal characteristics and the long-term variation of its effects. Therefore we analysed the seasonal evolution and spatial variations in the effect of ENSO on precipitation over the period of 1980-2013 and the long-term variation in the ENSO teleconnection using tree-ring-derived Palmer drought severity indices (PDSIs) for the March-May season that span over the time period 1650-2004. The analyses provided an improved understanding of the seasonal evolution of the precipitation anomalies during ENSO events. The effects of ENSO were found to be most consistent and expressed over the largest areal extents during March-May of the year when the ENSO events decay. On a longer timescale, we found that ENSO has affected the region's March-May hydroclimate over the majority (95 %) of the 355-year study period and that during half (52 %) of the time ENSO caused a significant increase in hydroclimatic variability. The majority of the extremely wet and dry March-May seasons also occurred during ENSO events. However, considerable variability in ENSO's influence was revealed: the spatial pattern of precipitation anomalies varied between individual ENSO events, and the strength of ENSO's influence was found to vary through time. Given the high variability in ENSO teleconnection that we described and the limitations of the current understanding of the effects of ENSO, we suggest that the adaptation to ENSO-related extremes in hydroclimate over mainland Southeast Asia needs to recognise uncertainty as an inherent part of adaptation, must go beyond

  2. The transfer of seasonal isotopic variability between precipitation and drip water at eight caves in the monsoon regions of China

    NASA Astrophysics Data System (ADS)

    Duan, Wuhui; Ruan, Jiaoyang; Luo, Weijun; Li, Tingyong; Tian, Lijun; Zeng, Guangneng; Zhang, Dezhong; Bai, Yijun; Li, Jilong; Tao, Tao; Zhang, Pingzhong; Baker, Andy; Tan, Ming

    2016-06-01

    This study presents new stable isotope data for precipitation (δ18Op) and drip water (δ18Od) from eight cave sites in the monsoon regions of China (MRC), with monthly to bi-monthly sampling intervals from May-2011 to April-2014, to investigate the regional-scale climate forcing on δ18Op and how the isotopic signals are transmitted to various drip sites. The monthly δ18Op values show negative correlation with surface air temperature at all the cave sites except Shihua Cave, which is opposite to that expected from the temperature effect. In addition, although the monthly δ18Op values are negatively correlated with precipitation at all the cave sites, only three sites are significant at the 95% level. These indicate that, due to the various vapor sources, a large portion of variability in δ18Op in the MRC cannot be explained simply by either temperature or precipitation alone. All the thirty-four drip sites are classified into three types based on the δ18Od variability. About 82% of them are static drips with little discernable variation in δ18Od through the whole study period, but the drip rates of these drips are not necessary constant. Their discharge modes are site-specific and the oxygen isotopic composition of the stalagmites growing from them may record the average of multi-year climatic signals, which are modulated by the seasonality of recharge and potential effects of evaporation, and in some cases infiltration from large rainfall events. About 12% of the thirty-four drip sites are seasonal drips, although the amplitude of δ18Od is narrower than that of δ18Op, the monthly response of δ18Od to coeval precipitation is not completely damped, and some of them follow the seasonal trend of δ18Op very well. These drips may be mainly recharged by present-day precipitation, mixing with some stored water. Thus, the stalagmites growing under them may record portions of the seasonal climatic signals embedded in δ18Op. About 6% of the thirty-four drip sites

  3. Carbon and hydrogen isotope composition of plant biomarkers as proxies for precipitation changes across Heinrich Events in the subtropics

    NASA Astrophysics Data System (ADS)

    Arnold, T. E.; Freeman, K.; Brenner, M.; Diefendorf, A. F.

    2014-12-01

    Lake Tulane is a relatively deep (~23 m) solution lake in south-central Florida. Its depth and location on a structural high, the Lake Wales Ridge, enabled continuous lacustrine sediment accumulation over the past >60,000 years. Pollen in the lake sediments indicate repeated major shifts in the vegetation community, with six peaks in Pinus (pine) abundance that coincide with the most intense cold phases of Dansgaard-Oeschger cycles and the Heinrich events that terminate them. Alternating with Pinus peaks are zones with high relative percentages of Quercus (oak), Ambrosia (ragweed), Lyonia (staggerbush) and Ceratiola (rosemary) pollen, genera that today occupy the most xeric sites on the Florida landscape. This suggests the pollen record indicates the Pinus phases, and therefore Heinrich Events, were wetter than the intervening Quercus phases. To test the connection between Heinrich Events and precipitation in Florida, we analyzed the carbon (δ13C) and hydrogen (δD) isotope signatures of plant biomarkers extracted from the Lake Tulane sediment core as proxies of paleohydrology. The δ13C of plant biomarkers, such as n-alkanes and terpenoids, are determined, in part, by changes in water-use efficiency (WUE = Assimilation/Transpiration) in plant communities, which changes in response to shifts in mean annual precipitation. Plant δ13C values can, therefore, provide a rough indication of precipitation changes when other factors, such as plant community, are relatively stable throughout time. Paleohydrology is also recorded in the δD of plant leaf waxes, which are strongly controlled by precipitation δD. In this region, precipitation δD is negatively correlated with rainfall amount (i.e. the "amount" effect) and positively correlated with aridity. Thus, the δ13C and δD signatures of molecular plant biomarkers provide relative indicators of precipitation change, and when combined, provide a test of our hypothesis that vegetation changes in this region are driven

  4. A spatial climatology of precipitation from North Atlantic tropical cyclones over the Eastern United States

    NASA Astrophysics Data System (ADS)

    Zhou, Y.

    2015-12-01

    The precipitation associated with tropical cyclones (TCs) over the eastern U.S has drawn significant attention from researchers. Among studies about tropical cyclone precipitation (TCP), separating rainfall into tropical and non-tropical cyclone components is a challenging task. Therefore, a need exists for continued spatial climatological analysis of rainfall associated of TCs. To provide a long-term climatology of TCP in this study, 305 TCs having tracks located within 500 km of the U.S. coastline from 1948-2012 are examined. The daily precipitation amounts on 0.25°× 0.25° latitude-longitude grids are from the Climate Prediction Center (CPC) Unified Precipitation Data (UPD). A GIS and Python based method is developed to identify rainfall swaths produced by TCs. Then we overlay all TCP swaths on a U.S. county map to get cumulative frequency of counties receiving rainfall from a TC with value greater than 25.4 mm. We find that there are 2533 counties in 25 states had been affected by TCP with value greater than 25.4 mm at least once during 1948 to 2012. The total area of TCP and TCP area averaged by annual TC counts and days shows significant increases after the 1990s. By comparing the rainfall swaths to the wind swaths as reported by previous work, we determine the frequency with which locations receive either condition produced by TCs. The results reveal that TCPs extend more inland and have more frequency than TC winds, since TC winds decays quickly after make landfall, while rainfall field may expand due to extra-tropical transition or land surface conditions.

  5. Isotopic constraints on fluid evolution and precipitation mechanisms for the Boléo Cu-Co-Zn district, Mexico

    NASA Astrophysics Data System (ADS)

    Conly, Andrew G.; Beaudoin, Georges; Scott, Steven D.

    2006-05-01

    Stable and radiogenic isotope composition of stratiform Cu-Co-Zn mineralization and associated sedimentary rocks within the Boléo district of the Miocene Santa Rosalía basin, Baja California Sur, constrains the evolution of seawater and hydrothermal fluids and the mechanisms responsible for sulfide and oxide deposition. Stable isotope geochemistry of limestone and evaporite units indicates a strong paleogeographic influence on the chemistry of the water column. Near-shore limestone at the base of the Boléo Formation is characterized by modified marine carbon ( δ 13CPDB=-6.0 to +4.4‰) and oxygen ( δ 18OSMOW=+19.5 to +26.2‰) isotope composition due to the influx of 13C- and 18O-depleted fluvial water. Sulfate sulfur isotope composition ( δ 34SCDT=+17.21 to +22.3‰ and δ 18OSMOW=+10.7 to +13.1‰) for basal evaporite and claystone facies are similar to Miocene seawater. Strontium isotopes are less radiogenic than expected for Miocene seawater due to interaction with volcanic rocks. Low S/C ratios, high Mn contents and sedimentological evidence indicate the basin water column was oxidizing. The oxygenated basin restricted sulfide precipitation to within the sedimentary pile by replacement of early diagenetic framboidal pyrite and pore-space filling by Cu-Co-Zn sulfides to produce disseminated sulfides. Quartz-Mn oxide oxygen isotope geothermometry constrains mineralization temperature between 18 and 118°C. Sulfur isotopes indicate the following sources of sulfide: (1) bacterial sulfate reduction within the sedimentary pile produced negative δ 34S values (<-20‰) in framboidal pyrite; and (2) bacterial sulfate reduction at high temperature (80-118°C) within the sedimentary pile during the infiltration of the metal-bearing brines produced Cu-Co-Zn sulfides with negative, but close to 0‰, δ 34S values. Isotope modeling of fluid-rock reaction and fluid mixing indicates: (1) sedimentary and marine carbonates ( δ 13C=-11.6 to -3.2‰ and δ 18O=+19.0 to

  6. Spatial variability in sulphur isotope values of archaeological and modern cod (Gadus morhua).

    PubMed

    Nehlich, Olaf; Barrett, James H; Richards, Michael P

    2013-10-30

    This study presents the first sulphur isotope data of modern and archaeological cod (Gadus morhua) bone collagen, undertaken to identify large-scale spatial variability of significance as both baseline values for studies of human diet and a potential variable in isotope-based studies of fish trading. Collagen was extracted from modern and archaeological cod bones using a weak HCl solution and analysed for its sulphur isotopic composition by isotope ratio mass spectrometry (IRMS). The archaeological cod have sulphur isotope values ranging from +9.1‰ to +18.2‰, whereas values for modern specimens range from +14.8‰ to +18.3‰. The modern data show values implying less freshwater influence, consistent with their offshore catch locations, but also corroborate some of the regional variability evident from the archaeological evidence. The archaeological data have a large range of sulphur isotope values compared with the modern populations, probably indicating they were taken from a wide range of geographic locations, including both coastal and offshore locales. They show broad trends of regional difference that may relate to both the fish populations targeted (e.g. 'inshore' versus 'offshore') and the baseline values of the local ecosystem (e.g. degree of freshwater input from river systems). Copyright © 2013 John Wiley & Sons, Ltd.

  7. Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks

    USGS Publications Warehouse

    Tangalos, G.E.; Beard, B.L.; Johnson, C.M.; Alpers, C.N.; Shelobolina, E.S.; Xu, H.; Konishi, H.; Roden, E.E.

    2012-01-01

    The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)am] that allow dissimilatory iron reduction (DIR) to predominate over Fe–S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. δ56Fe values for bulk HCl- and HF-extractable Fe were ≈ 0. These near-zero bulk δ56Fe values, together with the very low abundance of dissolved Fe in the overlying water column, suggest that the pyrite Fe source had near-zero δ56Fe values, and that complete oxidation of Fe(II) took place prior to deposition of the Fe(III) oxide-rich sediment. Sediment core analyses and incubation experiments demonstrated the production of millimolar quantities of isotopically light (δ56Fe ≈ -1.5 to -0.5‰) aqueous Fe(II) coupled to partial reduction of Fe(III)am by DIR. Trends in the Fe isotope composition of solid-associated Fe(II) and residual Fe(III)am are consistent with experiments with synthetic Fe(III) oxides, and collectively suggest an equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III)am of approximately -2‰. These Fe(III) oxide-rich sediments provide a model for early diagenetic processes that are likely to have taken place in Archean and Paleoproterozoic marine sediments that served as precursors for banded iron formations. Our results suggest pathways whereby DIR could have led to the formation of large quantities of low-δ56Fe minerals during BIF genesis.

  8. Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks.

    PubMed

    Tangalos, G E; Beard, B L; Johnson, C M; Alpers, C N; Shelobolina, E S; Xu, H; Konishi, H; Roden, E E

    2010-06-01

    The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)(am)] that allow dissimilatory iron reduction (DIR) to predominate over Fe-S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. delta(56)Fe values for bulk HCl- and HF-extractable Fe were approximately 0. These near-zero bulk delta(56)Fe values, together with the very low abundance of dissolved Fe in the overlying water column, suggest that the pyrite Fe source had near-zero delta(56)Fe values, and that complete oxidation of Fe(II) took place prior to deposition of the Fe(III) oxide-rich sediment. Sediment core analyses and incubation experiments demonstrated the production of millimolar quantities of isotopically light (delta(56)Fe approximately -1.5 to -0.5 per thousand) aqueous Fe(II) coupled to partial reduction of Fe(III)(am) by DIR. Trends in the Fe isotope composition of solid-associated Fe(II) and residual Fe(III)(am) are consistent with experiments with synthetic Fe(III) oxides, and collectively suggest an equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III)(am) of approximately -2 per thousand. These Fe(III) oxide-rich sediments provide a model for early diagenetic processes that are likely to have taken place in Archean and Paleoproterozoic marine sediments that served as precursors for banded iron formations. Our results suggest pathways whereby DIR could have led to the formation of large quantities of low-delta(56)Fe minerals during BIF genesis.

  9. Spatial distribution of electrical conductivity and stable isotopes in groundwater in large catchments: a geostatistical approach in the Quequén Grande River catchment, Argentina.

    PubMed

    Quiroz Londoño, Orlando Mauricio; Martínez, Daniel Emilio; Massone, Hector Enrique; Londoño Ciro, Libardo Antonio; Dapeña, Cristina

    2015-01-01

    Stable isotopes and electrical conductivity in groundwater were used as natural tracers to adjust the hydrogeological conceptual model in one of the largest catchments within the inter-mountainous Pampa plain, Argentina. Geostatistical tools were used to define the model that best fitted the spatial distribution of each tracer, and information was obtained in areas where there was a lack of data. The conventional isotopic analysis allowed the identification of three groundwater groups with different isotopic fingerprints. One group containing 56% of the total groundwater samples suggested a well-mixed system and soil infiltration precipitation as the main recharge source to the aquifer. The other two groups included samples with depleted (25.5%) and enriched (18.5%) isotopic compositions, respectively. The combination of δ(18)O, δ(2)H and electrical conductivities maps suggested ascending regional flows and water transfer from the Quequén Grande River catchment to the Moro creek. The spatial interpretation of these tracers modified the conceptual hydrogeological model of the Quequén Grande River.

  10. Characterizing the Spatial Contiguity of Extreme Precipitation over the US in the Recent Past

    NASA Astrophysics Data System (ADS)

    Touma, D. E.; Swain, D. L.; Diffenbaugh, N. S.

    2016-12-01

    The spatial characteristics of extreme precipitation over an area can define the hydrologic response in a basin, subsequently affecting the flood risk in the region. Here, we examine the spatial extent of extreme precipitation in the US by defining its "footprint": a contiguous area of rainfall exceeding a certain threshold (e.g., 90th percentile) on a given day. We first characterize the climatology of extreme rainfall footprint sizes across the US from 1980-2015 using Daymet, a high-resolution observational gridded rainfall dataset. We find that there are distinct regional and seasonal differences in average footprint sizes of extreme daily rainfall. In the winter, the Midwest shows footprints exceeding 500,000 sq. km while the Front Range exhibits footprints of 10,000 sq. km. Alternatively, the summer average footprint size is generally smaller and more uniform across the US, ranging from 10,000 sq. km in the Southwest to 100,000 sq. km in Montana and North Dakota. Moreover, we find that there are some significant increasing trends of average footprint size between 1980-2015, specifically in the Southwest in the winter and the Northeast in the spring. While gridded daily rainfall datasets allow for a practical framework in calculating footprint size, this calculation heavily depends on the interpolation methods that have been used in creating the dataset. Therefore, we assess footprint size using the GHCN-Daily station network and use geostatistical methods to define footprints of extreme rainfall directly from station data. Compared to the findings from Daymet, preliminary results using this method show fewer small daily footprint sizes over the US while large footprints are of similar number and magnitude to Daymet. Overall, defining the spatial characteristics of extreme rainfall as well as observed and expected changes in these characteristics allows us to better understand the hydrologic response to extreme rainfall and how to better characterize flood

  11. A sampling method for improving the representation of spatially varying precipitation and soil moisture using the Simple Biosphere Model

    NASA Astrophysics Data System (ADS)

    Medina, Isaac D.; Denning, A. Scott; Baker, Ian T.; Ramirez, Jorge A.; Randall, David A.

    2014-03-01

    spatially varying precipitation for current grid length scales used in General Circulation Models (GCMs) is a continuing challenge. Furthermore, to fully capture the hydrologic effects of nonuniform precipitation, a representation of soil moisture heterogeneity and distribution of spatially varying precipitation must exist within the same framework. For this study, the explicit and sampling methods of Sellers et al. (2007) are tested off-line using the Simple Biosphere Model (SiB3) in an arid, semiarid, and wet site, and are numerically compared to the bulk method, which is currently used in GCMs. To carry out the numerical experiments, an arbitrary grid area was defined by (1) a single instance of SiB3 (bulk method), (2) 100 instances of SiB3 (explicit method), and (3) less than 100 instances of SiB3 (sampling method). Precipitation was randomly distributed over fractions of the grid area for the explicit and sampling methods, while the standard SiB3 exponential distribution relating precipitation intensity to the grid area wet fraction was used in the bulk method. Comparing the sampling and bulk method to the explicit method indicates that 10 instances of SiB3 in the sampling method better captures the spatial variability in soil moisture and grid area flux calculations produced by the explicit method, and deals realistically with spatially varying precipitation at little additional computational cost to the bulk method.

  12. Analysis of stable isotope ratios (δ18O and δ2H) in precipitation of the Verde River watershed, Arizona 2013 through 2014

    USGS Publications Warehouse

    Beisner, Kimberly R.; Paretti, Nicholas V.; Tucci, Rachel S.

    2016-04-25

    Stable isotope delta values (δ18O and δ2H) of precipitation can vary with elevation, and quantification of the precipitation elevation gradient can be used to predict recharge elevation within a watershed. Precipitation samples were analyzed for stable isotope delta values between 2003 and 2014 from the Verde River watershed of north-central Arizona. Results indicate a significant decrease in summer isotopic values overtime at 3,100-, 4,100-, 6,100-, 7,100-, and 8,100-feet elevation. The updated local meteoric water line for the area is δ2H = 7.11 δ18O + 3.40. Equations to predict stable isotopic values based on elevation were updated from previous publications in Blasch and others (2006), Blasch and Bryson (2007), and Bryson and others (2007). New equations were separated for samples from the Camp Verde to Flagstaff transect and the Prescott to Chino Valley transect. For the Camp Verde to Flagstaff transect, the new equations for winter precipitation are δ18O = -0.0004z − 8.87 and δ2H = -0.0029z − 59.8 (where z represents elevation in feet) and the summer precipitation equations were not statistically significant. For the Prescott to Chino Valley transect, the new equations for summer precipitation are δ18O = -0.0005z − 3.22 and δ2H = -0.0022z − 27.9; the winter precipitation equations were not statistically significant and, notably, stable isotope values were similar across all elevations. Interpretation of elevation of recharge contributing to surface and groundwaters in the Verde River watershed using the updated equations for the Camp Verde to Flagstaff transect will give lower elevation values compared with interpretations presented in the previous studies. For waters in the Prescott and Chino Valley area, more information is needed to understand local controls on stable isotope values related to elevation.

  13. Analysis of stable isotope ratios (δ18O and δ2H) in precipitation of the Verde River watershed, Arizona 2003 through 2014

    USGS Publications Warehouse

    Beisner, Kimberly R.; Paretti, Nicholas V.; Tucci, Rachel S.

    2016-04-25

    Stable isotope delta values (δ18O and δ2H) of precipitation can vary with elevation, and quantification of the precipitation elevation gradient can be used to predict recharge elevation within a watershed. Precipitation samples were analyzed for stable isotope delta values between 2003 and 2014 from the Verde River watershed of north-central Arizona. Results indicate a significant decrease in summer isotopic values overtime at 3,100-, 4,100-, 6,100-, 7,100-, and 8,100-feet elevation. The updated local meteoric water line for the area is δ2H = 7.11 δ18O + 3.40. Equations to predict stable isotopic values based on elevation were updated from previous publications in Blasch and others (2006), Blasch and Bryson (2007), and Bryson and others (2007). New equations were separated for samples from the Camp Verde to Flagstaff transect and the Prescott to Chino Valley transect. For the Camp Verde to Flagstaff transect, the new equations for winter precipitation are δ18O = -0.0004z − 8.87 and δ2H = -0.0029z − 59.8 (where z represents elevation in feet) and the summer precipitation equations were not statistically significant. For the Prescott to Chino Valley transect, the new equations for summer precipitation are δ18O = -0.0005z − 3.22 and δ2H = -0.0022z − 27.9; the winter precipitation equations were not statistically significant and, notably, stable isotope values were similar across all elevations. Interpretation of elevation of recharge contributing to surface and groundwaters in the Verde River watershed using the updated equations for the Camp Verde to Flagstaff transect will give lower elevation values compared with interpretations presented in the previous studies. For waters in the Prescott and Chino Valley area, more information is needed to understand local controls on stable isotope values related to elevation.

  14. Climatic trends in hail precipitation in France: spatial, altitudinal, and temporal variability.

    PubMed

    Hermida, Lucía; Sánchez, José Luis; López, Laura; Berthet, Claude; Dessens, Jean; García-Ortega, Eduardo; Merino, Andrés

    2013-01-01

    Hail precipitation is characterized by enhanced spatial and temporal variability. Association Nationale d'Etude et de Lutte contre les Fléaux Atmosphériques (ANELFA) installed hailpad networks in the Atlantic and Midi-Pyrénées regions of France. Historical data of hail variables from 1990 to 2010 were used to characterize variability. A total of 443 stations with continuous records were chosen to obtain a first approximation of areas most affected by hail. The Cressman method was selected for this purpose. It was possible to find relationships between spatial distributions of the variables, which are supported by obtained Pearson correlations. Monthly and annual trends were examined using the Mann-Kendall test for each of the total affected hailpads. There were 154 pads with a positive trend; most were located between Tarbes and Saint-Gaudens. We found 177 pads with a negative trend, which were largely south of a pine forest in Landes. The remainder of the study area showed an elevated spatial variability with no pattern, even between relatively close hailpads. A similar pattern was found in Lérida (Spain) and Southeast France. In the entire area, monthly trends were predominantly negative in June, July, and August, whereas May had a positive trend; again, however, there was no spatial pattern. There was a high concentration of hailpads with positive trend near the Pyrenees, probably owing to orographic effects, and if we apply cluster analysis with the Mann-Kendall values, the spatial variability is accentuated for stations at higher altitude.

  15. Climatic Trends in Hail Precipitation in France: Spatial, Altitudinal, and Temporal Variability

    PubMed Central

    Hermida, Lucía; Sánchez, José Luis; López, Laura; Berthet, Claude; Dessens, Jean; García-Ortega, Eduardo; Merino, Andrés

    2013-01-01

    Hail precipitation is characterized by enhanced spatial and temporal variability. Association Nationale d'Etude et de Lutte contre les Fléaux Atmosphériques (ANELFA) installed hailpad networks in the Atlantic and Midi-Pyrénées regions of France. Historical data of hail variables from 1990 to 2010 were used to characterize variability. A total of 443 stations with continuous records were chosen to obtain a first approximation of areas most affected by hail. The Cressman method was selected for this purpose. It was possible to find relationships between spatial distributions of the variables, which are supported by obtained Pearson correlations. Monthly and annual trends were examined using the Mann-Kendall test for each of the total affected hailpads. There were 154 pads with a positive trend; most were located between Tarbes and Saint-Gaudens. We found 177 pads with a negative trend, which were largely south of a pine forest in Landes. The remainder of the study area showed an elevated spatial variability with no pattern, even between relatively close hailpads. A similar pattern was found in Lérida (Spain) and Southeast France. In the entire area, monthly trends were predominantly negative in June, July, and August, whereas May had a positive trend; again, however, there was no spatial pattern. There was a high concentration of hailpads with positive trend near the Pyrenees, probably owing to orographic effects, and if we apply cluster analysis with the Mann-Kendall values, the spatial variability is accentuated for stations at higher altitude. PMID:24307872

  16. Spatially resolved δ13C analysis using laser ablation isotope ratio mass spectrometry

    NASA Astrophysics Data System (ADS)

    Moran, J.; Riha, K. M.; Nims, M. K.; Linley, T. J.; Hess, N. J.; Nico, P. S.

    2014-12-01

    Inherent geochemical, organic matter, and microbial heterogeneity over small spatial scales can complicate studies of carbon dynamics through soils. Stable isotope analysis has a strong history of helping track substrate turnover, delineate rhizosphere activity zones, and identifying transitions in vegetation cover, but most traditional isotope approaches are limited in spatial resolution by a combination of physical separation techniques (manual dissection) and IRMS instrument sensitivity. We coupled laser ablation sampling with isotope measurement via IRMS to enable spatially resolved analysis over solid surfaces. Once a targeted sample region is ablated the resulting particulates are entrained in a helium carrier gas and passed through a combustion reactor where carbon is converted to CO2. Cyrotrapping of the resulting CO2 enables a reduction in carrier gas flow which improves overall measurement sensitivity versus traditional, high flow sample introduction. Currently we are performing sample analysis at 50 μm resolution, require 65 ng C per analysis, and achieve measurement precision consistent with other continuous flow techniques. We will discuss applications of the laser ablation IRMS (LA-IRMS) system to microbial communities and fish ecology studies to demonstrate the merits of this technique and how similar analytical approaches can be transitioned to soil systems. Preliminary efforts at analyzing soil samples will be used to highlight strengths and limitations of the LA-IRMS approach, paying particular attention to sample preparation requirements, spatial resolution, sample analysis time, and the types of questions most conducive to analysis via LA-IRMS.

  17. Surface Kinetic Model for the Fractionation of Trace Elements and Isotopes in Calcite Precipitated from Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Depaolo, D. J.; Ryerson, F. J.; Watkins, J. M.; Bourg, I. C.; Yang, W.; Nielsen, L. C.; Druhan, J. L.

    2010-12-01

    The isotopic and trace element concentrations in calcite and other carbonate minerals form the basis for several paleoceanographic and paleoenvironmental indicators. The chemical and isotopic composition of natural calcites is determined by a combination of equilibrium partitioning and kinetic fractionations. Currently there is no general model that describes when equilibrium applies and how kinetic effects depend on the circumstances and rates of mineral growth. A useful approach is to separate the growth of calcite from aqueous solutions into forward (f) and backward (b) reactions, and to consider the mechanisms and fractionations that may be associated with each. We are evaluating a model where the net precipitation rate of calcite (Rp) is expressed as the difference between a forward rate (Rf) and a backward (dissolution) rate (Rb). Dissolution is approached only as Rp/Rb->0. Much natural calcite, including biogenic, forms under conditions where Rp ≫ Rb, hence the isotopic and trace element partitioning is strongly influenced by the kinetics of the forward reaction. Assuming that there are kinetic fractionations associated with the forward and backward reactions, a simple model can be developed for the dependence of calcite composition on precipitation rate. This model can explain most available experimental data on Ca and O isotopes, as well as Sr/Ca and Mn/Ca in calcite, and can be used to infer the behavior of other trace and minor elements. The critical parameter in applying the model is the value of Rb which to first order can be estimated from mineral dissolution rates, but apparently is not a constant, but instead varies with solution chemistry, especially at saturation conditions close to equilibrium. The surface kinetic model requires three parameters that are measureable experimentally and potentially also predictable from molecular dynamics simulation approaches. In this way it differs from the surface entrapment model of Watson (2004) which

  18. Spatial variability of summer Florida precipitation and its impact on microwave radiometer rainfall-measurement systems

    NASA Technical Reports Server (NTRS)

    Turner, B. J.; Austin, G. L.

    1993-01-01

    Three-dimensional radar data for three summer Florida storms are used as input to a microwave radiative transfer model. The model simulates microwave brightness observations by a 19-GHz, nadir-pointing, satellite-borne microwave radiometer. The statistical distribution of rainfall rates for the storms studied, and therefore the optimal conversion between microwave brightness temperatures and rainfall rates, was found to be highly sensitive to the spatial resolution at which observations were made. The optimum relation between the two quantities was less sensitive to the details of the vertical profile of precipitation. Rainfall retrievals were made for a range of microwave sensor footprint sizes. From these simulations, spatial sampling-error estimates were made for microwave radiometers over a range of field-of-view sizes. The necessity of matching the spatial resolution of ground truth to radiometer footprint size is emphasized. A strategy for the combined use of raingages, ground-based radar, microwave, and visible-infrared (VIS-IR) satellite sensors is discussed.

  19. Spatial variability of seasonal extreme precipitation in the western United States

    NASA Astrophysics Data System (ADS)

    Bracken, C.; Rajagopalan, B.; Alexander, M.; Gangopadhyay, S.

    2015-05-01

    We examine the characteristics of 3 day total extreme precipitation in the western United States. Coherent seasonal spatial patterns of timing and magnitude are evident in the data, motivating a seasonally based analysis. Using a clustering method that is consistent with extreme value theory, we identify coherent regions for extremes that vary seasonally. Based on storm back trajectory analysis, we demonstrate unique moisture sources and dominant moisture pathways for each spatial region. In the winter the Pacific Ocean is the dominant moisture source across the west, but in other seasons the Gulf of Mexico, the Gulf of California, and the land surface over the midwestern U.S. play an important role. We find the El Niño-Southern Oscillation (ENSO) to not have a strong impact on dominant moisture delivery pathways or moisture sources. The frequency of extremes under ENSO is spatially coherent and seasonally dependent with certain regions tending to have more (less) frequent extreme events in El Niño (La Niña) conditions.

  20. Annual precipitation regulates spatial and temporal drivers of lake water clarity.

    PubMed

    Rose, Kevin C; Greb, Steven R; Diebel, Matthew; Turner, Monica G

    2017-03-01

    Understanding how and why lakes vary and respond to different drivers through time and space is needed to understand, predict, and manage freshwater quality in an era of rapidly changing land use and climate. Water clarity regulates many characteristics of aquatic ecosystems and is responsive to watershed features, making it a sentinel of environmental change. However, whether precipitation alters the relative importance of features that influence lake water clarity or the spatial scales at which they operate is unknown. We used a data set of thousands of northern temperate lakes and asked (1) How does water clarity differ between a very wet vs. dry year? (2) Does the relative importance of different watershed features, or the spatial extent at which they are measured, vary between wet and dry years? (3) What lake and watershed characteristics regulate long-term water clarity trends? Among lakes, water clarity was reduced and less variable in the wet year than in the dry year; furthermore, water clarity was reduced much more in high-clarity lakes during the wet year than in low-clarity lakes. Climate, land use/land cover, and lake morphometry explained most variance in clarity among lakes in both years, but the spatial scales at which some features were important differed between the dry and wet years. Watershed percent agriculture was most important in the dry year, whereas riparian zone percent agriculture (around each lake and upstream features) was most important in the wet year. Between 1991 and 2012, water clarity declined in 23% of lakes and increased in only 6% of lakes. Conductance influenced the direction of temporal trend (clarity declined in lakes with low conductance), whereas the proportion of watershed wetlands, catchment-to-lake-area ratio, and lake maximum depth interacted with antecedent precipitation. Many predictors of water clarity, such as lake depth and landscape position, are features that cannot be readily managed. Given trends of

  1. Controls on oxygen isotope variability in precipitation and drip water at eight caves in the monsoon regions of China

    NASA Astrophysics Data System (ADS)

    Duan, Wuhui; Ruan, Jiaoyang; Luo, Weijun; Li, Tingyong; Tian, Lijun; Zeng, Guangneng; Zhang, Dezhong; Bai, Yijun; Li, Jilong; Tao, Tao; Zhang, Pingzhong; Tan, Ming

    2015-04-01

    Cave monitoring is important to fully understand the climatic significance of stalagmite δ18O records. Most previous studies focus on one cave, or several caves in one area. A large regional-scale investigation on the isotopic composition of precipitation and drip water is scarce. To investigate the regional-scale climate forcing on the oxygen isotopic composition of precipitation in the monsoon regions of China (MRC) and how the isotopic signals are transmitted to various drip sites, a three-year-long (2011-2014) on-site rainfall and drip water monitoring program has been carried out with approximately monthly sampling at 37 drip sites in eight caves in the MRC. Neither rainfall amount nor air temperature are the predominant controls on the oxygen isotopic composition of monthly precipitation. The rain in the wet season (May to October), with relatively low δ18O values, is sourced from tropical air masses, whereas the rainfall in the dry season (November to April), with relatively high δ18O values, is mostly sourced from continental air masses. Additionally, the weighted summer rainwater δ18O values decrease from coastal southwest China to inland northeast China, which suggests that the moisture of monsoon rainfall in China originates mainly from Indian Ocean, and transports to the north along the southwest-northeast path. 28 of the 37 drip sites are constant drips with little discernable variation in drip water δ18O through the whole study period. For most of the constant drips, the mean value of each drip water δ18O is nearly identical to or slightly higher than the three-year weighted mean value of the corresponding local rainwater δ18O, indicating these drips may be mainly recharged by none-evaporated or slightly evaporated, well-mixed older water stored in the vadose zone. 7 of all the 37 drip sites are seasonal drips, for which, although the amplitude of drip water δ18O is narrower than that of rainfall, the monthly response of drip water δ18O to

  2. D/H ratios in speleothem fluid inclusions: A guide to variations in the isotopic composition of meteoric precipitation?

    USGS Publications Warehouse

    Harmon, R.S.; Schwarcz, H.P.; O'Neil, J.R.

    1979-01-01

    D/H ratios of fluid inclusion waters extracted from 230Th/234U-dated speleothems that were originally deposited under conditions of isotopic equilibrium should provide a direct estimate of the hydrogen isotopic composition of ancient meteoric waters. We present here D/H ratios for 47 fluid inclusion samples from thirteen speleothems deposited over the past 250,000 years at cave sites in Iowa, West Virginia, Kentucky and Missouri. At each site glacial-age waters are depleted in deuterium relative to those of interglacial age. The average interglacial/glacial shift in the hydrogen isotopic composition of meteoric precipitation over ice-free areas of east-central North America is estimated to be -12???. This shift is consistent with the present climatic models and can be explained in terms of the prevailing pattern of atmospheric circulation and an increased ocean-continent temperature gradient during glacial times which more than compensated for the increase in deuterium content of the world ocean. ?? 1979.

  3. High Spatial Resolution Isotopic Abundance Measurements by Secondary Ion Mass Spectrometry: Status and Prospects

    NASA Astrophysics Data System (ADS)

    McKeegan, K. D.

    2007-12-01

    Secondary Ion Mass Spectrometry, SIMS or ion microprobe analysis, has become an important tool for geochemistry because of its ability study the distributions of elemental and isotopic abundances in situ on polished samples with high (typically a few microns to sub-micron) spatial resolution. In addition, SIMS exhibits high sensitivity for a wide range of elements (H to Pu) so that isotope analyses can sometimes be performed for elements that comprise only trace quantities of some mineral phase (e.g., Pb in zircon) or on major and/or minor elements in very small samples (e.g., presolar dust grains). Offsetting these positive attributes are analytical difficulties due to the complexity of the sputtering source of analyte ions: (1) relatively efficient production of molecular ion species (especially from a complex matrix such as most natural minerals) that cause interferences at the same nominal mass as atomic ions of interest, and (2) quantitation problems caused by variations in the ionization efficiencies of different elements and/or isotopes depending upon the chemical state of the sample surface during sputtering--the so-called "matrix effects". Despite the availability of high mass resolution instruments (e.g., SHRIMP II/RG, CAMECA 1270/1280/NanoSIMS), the molecular ion interferences effectively limit the region of the mass table that can be investigated in most samples to isotope systems at Ni or lighter or at Os or heavier. The matrix effects and the sensitivity of instrumental mass discrimination to the physical state of the sample surface can hamper reproducibility and have contributed to a view that SIMS analyses, especially for so- called stable isotopes, are most appropriate for extraterrestrial samples which are often small, rare, and can exhibit large magnitude isotopic effects. Recent improvements in instrumentation and technique have extended the scope of SIMS isotopic analyses and applications now range from geochronology to paleoclimatology to

  4. Temporal and spatial intermittency of sub-daily precipitation in general circulation models

    NASA Astrophysics Data System (ADS)

    Klingaman, Nicholas; Martin, Gill; Moise, Aurel

    2015-04-01

    General circulation models often fail to reproduce the observed spatial and temporal distributions of tropical precipitation (e.g. Stephens et al. 2010). The need for improved understanding of how a warming climate may change precipitation variability and extremes has focused model developers' attention on the inability of convection parameterizations to represent the observed range of deep convective processes (e.g. Rossow et al. 2013). As climate-model resolutions increase towards scales previously used for short-term forecasting, the benefits of seamless modelling are being balanced by increasingly apparent deficiencies in convection parameterizations. Under particular scrutiny are the consequences of poorly simulated sub-daily, gridpoint precipitation variability on rainfall distributions at longer (e.g., daily, seasonal, decadal) and larger scales. We present the behaviour of tropical convection in the MetUM in a hierarchy of global configurations from ~10km to ~100km resolution, and in ten climate models from the "Vertical Structure and Diabatic Processes of the Madden-Julian Oscillation" project. We establish new methods of analysing timestep precipitation that allow comparisons between resolutions and physical parameterizations. We first investigate the relationship between timestep-to-timestep variations of modelled convection at the gridbox scale and its variability on longer and larger scales, and compare simulated and observed rainfall variability. We demonstrate that convection parameterization changes that alter timestep variability (e.g., entrainment and detrainment rates and closure timescales) also affect longer-scale variability. For example, we show that ~100 km configurations exhibit coherent timestep intermittency at large spatial scales, which reduce at finer resolutions and with parameterisation changes that suppress the depth and intensity of convection. Despite a wide variety of timestep behaviour, the models from the "Vertical Structure

  5. APHRODITE daily precipitation and temperature dataset: Development, QC, Homogenization and Spatial Correlation

    NASA Astrophysics Data System (ADS)

    Yatagai, Akiyo; Zhao, Tianbao

    2014-05-01

    A daily gridded precipitation dataset for the period 1951-2007 was created by collecting and analyzing rain-gauge observation data across Asia through the activities of the Asian Precipitation - Highly Resolved Observational Data Integration Towards Evaluation (APHRODITE) of water resources project. They are available at http://www.chikyu.ac.jp/precip/. Utilization of station data is ideal for analyses of climatic trends, especially for those of extreme events. However, there was an increasing demand for accurate high-resolution gauge-based precipitation analyses. Rain-gauge based products are sometimes used for assessing trends of climate models or that of river runoff through driving hydrological models, because they are convenient and long records. On the other hand, some information is lost during the gridding process. Hence, in-house results of testing interpolation scheme, quality control and homogenization may give important information for the users. We will present such results as well as our quality control (QC) in the APHRODITE project activities. Before gridding, 14 objective QC steps were applied to the rain-gauge data, which mainly includes position checking, duplicate data checking and inhomogeneity and spatiotemporal isolation etc. Details are described in Hamada et al. (2011). For Chinese data, basic QC steps such as duplicate checking and position checking have been made by the local meteorological agency. Hence we made homogenization test and spatial correlation analyses separately. For 756 Chinese daily temperature stations, we applied Multiple Analysis of Series for Homogenization (MASH) developed by Szentimrey (1999, 2008). The results show this statistical method we used has a good performance to detect the discontinuities in climate series caused by station relocation, instrument change etc. regardless of the absence of metadata. Through the homogenization, most of discontinuities existed in original temperature data can be removed, and the

  6. [Effect of Below-cloud Secondary Evaporation in Precipitations over the Loess Plateau Based on the Stable Isotopes of Hydrogen and Oxygen].

    PubMed

    Jin, Xiao-gang; Zhang, Ming-jun; Wang, Sheng-jie; Zhu, Xiao-fan; Dong, Lei; Ren, Zheng-guo; Chen, Fen-li

    2015-04-01

    Based on stable isotopes in 409 precipitation samples provided by GNIP and meteorological records at the eight stations in Loess Plateau from January 1985 to December 2004, as well as the trajectory model of HYSPLIT 4.9, the spatial and temporal variations of d-excess and Δ18O were analyzed. The spatial distribution of secondary evaporation rate and the impact of meteorological factors on below-cloud secondary evaporation were also discussed. The result showed that: (1) During summer and winter monsoon periods, Δ18O showed an uptrend variation and d-excess showed a downtrend variation from south to north in Loess Plateau. From east to west, Δ180 showed an uptrend variation only in summer monsoon period and a downtrend variation in winter monsoon period. The value of d-excess also showed a downtrend variation. Amplitude of variation Δ18O and d-excess could indicate the routes of monsoon. (2) Secondary evaporation existed on an annual basis, and it was relatively significant during the summer monsoon period, with ranges from 1.51% to 5.88% and an average rate of 3.87%. While winter monsoon became lower, the rates ranged from 1.06% to 5.46%, and the average rate dropped to 3.03%. Monsoon had larger influence on secondary evaporation in margin area of the plateau, while the influence on the central stations was little. (3) Temperature had the highest contribution to secondary evaporation, followed by precipitation amount and water vapor pressure, and relative humidity had a small contribution. Moreover, the influence of wind speed and altitude on secondary evaporation was weak.

  7. Plant community responses to precipitation and spatial pattern of nitrogen supply in an experimental grassland ecosystem.

    PubMed

    Xi, Nianxun; Carrère, Pascal; Bloor, Juliette M G

    2015-06-01

    Recent work suggests that soil nutrient heterogeneity may modulate plant responses to drivers of global change, but interactions between N heterogeneity and changes in rainfall regime remain poorly understood. We used a model grassland system to investigate the interactive effects of N application pattern (homogeneous, heterogeneous) and precipitation-magnitude manipulation during the growing season (control, +50 % rainfall, -50 % rainfall) on aboveground biomass and plant community dominance patterns. Our study resulted in four major findings: patchy N addition increased within-plot variability in plant size structure at the species level, but did not alter total aboveground biomass; patchy N addition increased community dominance and caused a shift in the ranking of subordinate plant species; unlike community-level biomass, plant species differed in their biomass response to the rainfall treatments; and neither aboveground biomass nor community dominance showed significant interactions between N pattern and rainfall manipulation, suggesting that grassland responses to patchy N inputs are insensitive to water addition or rainfall reduction in our temperate study system. Overall, our results indicate that the spatial pattern of N inputs has greater effects on species biomass variability and community dominance than on aboveground production. These short-term changes in plant community structure may have significant implications for longer-term patterns of vegetation dynamics and plant-soil feedbacks. Moreover our results suggest that the magnitude of precipitation during the growing season plays a limited role in grassland responses to heterogeneous organic N inputs, emphasizing the need to consider other components of precipitation change in future heterogeneity studies.

  8. Dependence of long-term persistence properties of precipitation on spatial and regional characteristics

    NASA Astrophysics Data System (ADS)

    Tyralis, Hristos; Dimitriadis, Panayiotis; Iliopoulou, Theano; Tzouka, Katerina; Koutsoyiannis, Demetris

    2017-04-01

    The long-term persistence (LTP), else known in hydrological science as the Hurst phenomenon, is a behaviour observed in geophysical processes in which wet years or dry years are clustered to respective long time periods. A common practice for evaluating the presence of the LTP is to model the geophysical time series with the Hurst-Kolmogorov process (HKp) and estimate its Hurst parameter H where high values of H indicate strong LTP. We estimate H of the mean annual precipitation using instrumental data from approximately 1 500 stations which cover a big area of the earth's surface and span from 1916 to 2015. We regress the H estimates of all stations on their spatial and regional characteristics (i.e. their location, elevation and Köppen-Geiger climate class) using a random forest algorithm. Furthermore, we apply the Mann-Kendall test under the LTP assumption (MKt-LTP) to all time series to assess the significance of observed trends of the mean annual precipitation. To summarize the results, the LTP seems to depend mostly on the location of the stations, while the predictive value of the fitted regression model is good. Thus when investigating for LTP properties we recommend that the local characteristics should be considered. Additionally, the application of the MKt-LTP suggests that no significant monotonic trend can characterize the global precipitation. Dominant positive significant trends are observed mostly in main climate type D (snow), while in the other climate types the percentage of stations with positive significant trends was approximately equal to that of negative significant trends. Furthermore, 50% of all stations do not exhibit significant trends at all.

  9. Spatial and seasonal patterns in climate change, temperatures, and precipitation across the United States.

    PubMed

    Portmann, Robert W; Solomon, Susan; Hegerl, Gabriele C

    2009-05-05

    Changes in climate during the 20th century differ from region to region across the United States. We provide strong evidence that spatial variations in US temperature trends are linked to the hydrologic cycle, and we also present unique information on the seasonal and latitudinal structure of the linkage. We show that there is a statistically significant inverse relationship between trends in daily temperature and average daily precipitation across regions. This linkage is most pronounced in the southern United States (30-40 degrees N) during the May-June time period and, to a lesser extent, in the northern United States (40-50 degrees N) during the July-August time period. It is strongest in trends in maximum temperatures (T(max)) and 90th percentile exceedance trends (90PET), and less pronounced in the T(max) 10PET and the corresponding T(min) statistics, and it is robust to changes in analysis period. Although previous studies suggest that areas of increased precipitation may have reduced trends in temperature compared with drier regions, a change in sign from positive to negative trends suggests some additional cause. We show that trends in precipitation may account for some, but not likely all, of the cause point to evidence that shows that dynamical patterns (El Niño/Southern Oscillation, North Atlantic Oscillation, etc.) cannot account for the observed effects during May-June. We speculate that changing aerosols, perhaps related to vegetation changes, and increased strength of the aerosol direct and indirect effect may play a role in the observed linkages between these indices of temperature change and the hydrologic cycle.

  10. Spatial and temporal variability of clouds and precipitation over Germany: multiscale simulations across the "gray zone"

    NASA Astrophysics Data System (ADS)

    Barthlott, C.; Hoose, C.

    2015-11-01

    This paper assesses the resolution dependance of clouds and precipitation over Germany by numerical simulations with the COnsortium for Small-scale MOdeling (COSMO) model. Six intensive observation periods of the HOPE (HD(CP)2 Observational Prototype Experiment) measurement campaign conducted in spring 2013 and 1 summer day of the same year are simulated. By means of a series of grid-refinement resolution tests (horizontal grid spacing 2.8, 1 km, 500, and 250 m), the applicability of the COSMO model to represent real weather events in the gray zone, i.e., the scale ranging between the mesoscale limit (no turbulence resolved) and the large-eddy simulation limit (energy-containing turbulence resolved), is tested. To the authors' knowledge, this paper presents the first non-idealized COSMO simulations in the peer-reviewed literature at the 250-500 m scale. It is found that the kinetic energy spectra derived from model output show the expected -5/3 slope, as well as a dependency on model resolution, and that the effective resolution lies between 6 and 7 times the nominal resolution. Although the representation of a number of processes is enhanced with resolution (e.g., boundary-layer thermals, low-level convergence zones, gravity waves), their influence on the temporal evolution of precipitation is rather weak. However, rain intensities vary with resolution, leading to differences in the total rain amount of up to +48 %. Furthermore, the location of rain is similar for the springtime cases with moderate and strong synoptic forcing, whereas significant differences are obtained for the summertime case with air mass convection. Domain-averaged liquid water paths and cloud condensate profiles are used to analyze the temporal and spatial variability of the simulated clouds. Finally, probability density functions of convection-related parameters are analyzed to investigate their dependance on model resolution and their impact on cloud formation and subsequent precipitation.

  11. Structure of the spatial periphery of the isotopes {sup 9,11}Li

    SciTech Connect

    Galanina, L. I. Zelenskaya, N. S.

    2015-07-15

    The cross sections for the (t, p) reactions on the lithium isotopes {sup 9,11}Li were calculated within a theoretical approach based on employing integral equations of the four-body problem in the Alt—Grassberger-Sandhas formalism and the multiparticle shell model. This made it possible to determine the wave functions for the relative motion of various clusters and the nuclear core and to calculate, on their basis, the root-mean-square radii of nuclei of the isotopes {sup 9,11}Li and the spatial structure of their neutron periphery. It is shown that the {sup 9}Li nucleus has virtually no neutron halo. The {sup 11}Li nucleus is a Borromean halo nucleus. The two-neutron periphery of this nucleus manifests itself in both spatial configurations, a dineutron and a cigar one, the respective root-mean-square radii being large (about 6.5 to 6.9 fm)

  12. Isotopic composition in precipitation and groundwater in the northern mountainous region of the Central Valley of Costa Rica.

    PubMed

    Sánchez-Murillo, Ricardo; Esquivel-Hernández, Germain; Sáenz-Rosales, Oscar; Piedra-Marín, Gilberto; Fonseca-Sánchez, Alicia; Madrigal-Solís, Helga; Ulloa-Chaverri, Franz; Rojas-Jiménez, Luis D; Vargas-Víquez, José A

    2017-03-01

    The linkage between precipitation and recharge is still poorly understood in the Central America region. This study focuses on stable isotopic composition in precipitation and groundwater in the northern mountainous region of the Central Valley of Costa Rica. During the dry season, rainfall samples corresponded to enriched events with high deuterium excess. By mid-May, the Intertropical Convergence Zone poses over Costa Rica resulting in a depletion of (18)O/(16)O and (2)H/H ratios. A parsimonious four-variable regression model (r(2 )= 0.52) was able to predict daily δ(18)O in precipitation. Air mass back trajectories indicated a combination of Caribbean Sea and Pacific Ocean sources, which is clearly depicted in groundwater isoscape. Aquifers relying on Pacific-originated recharge exhibited a more depleted pattern, whereas recharge areas relying on Caribbean parental moisture showed an enrichment trend. These results can be used to enhance modelling efforts in Central America where scarcity of long-term data limits water resources management plans.

  13. North Atlantic Oscillation controls on oxygen and hydrogen isotope gradients in winter precipitation across Europe; implications for palaeoclimate studies

    NASA Astrophysics Data System (ADS)

    Deininger, Michael; Werner, Martin; McDermott, Frank

    2016-11-01

    Winter (October to March) precipitation δ18OP and δDP values in central Europe correlate with the winter North Atlantic Oscillation index (wNAOi), but the causal mechanisms remain poorly understood. Here we analyse the relationships between precipitation-weighted δ18OP and δDP datasets (δ18Opw and δDpw) from European GNIP and ANIP stations and the wNAOi, with a focus on isotope gradients. We demonstrate that longitudinal δ18Opw and δDpw gradients across Europe ("continental effect") depend on the wNAOi state, with steeper gradients associated with more negative wNAOi states. Changing gradients reflect a combination of air temperature and variable amounts of precipitable water as a function of the wNAOi. The relationships between the wNAOi, δ18Opw and δDpw can provide additional information from palaeoclimate archives such as European speleothems that primarily record winter δ18Opw. Comparisons between present-day and past European longitudinal δ18O gradients inferred from Holocene speleothems suggest that atmospheric pressure configurations akin to negative wNAO modes dominated the early Holocene, whereas patterns resembling positive wNAO modes were more common in the late Holocene, possibly caused by persistent shifts in the relative locations of the Azores High and the Icelandic Low.

  14. Seasonal and Spatial Variations of Stable Strontium Isotope in the Suspended Sediments of the Changjiang ( Yangtze) River

    NASA Astrophysics Data System (ADS)

    WANG, X.; Yang, S.; Wei, G.

    2014-12-01

    In recent years, remarkable stable strontium fractionation has been found in many geological and biological processes such as chemical weathering and carbonate precipitation. The stable strontium isotope (δ88/86Sr) compositions in various natural materials have been studied, yet its behavior in river water and sediment remains to be clarified. The Changjiang is the largest river originating from the Tibetan Plateau, and bridges the Eurasian continent and East Asian marginal sea by delivering a large volume of dissolved and particulate materials into the sea. It has complicated tributary system and source rock types and is subject to strong Asian monsoon impacts, which makes it an ideal river for the study of sediment weathering, recycling and source-to-sink transport processes. In this study, spatial and seasonal suspended sediments were collected from the Changjiang mainstream by filtering with 0.45 μm Millipore membrane in the field. The seasonal samples were taken from Datong hydrological station in the lower reaches during a whole hydrological year. All these samples were dissolved with 4N HNO3 to separate them into two different phases: leachate and residue. The stable strontium isotope ratios in these two phases were analyzed using SSB method described in Ma et al. (2013) with MC-ICP-MS. The reference material was SRM 987. The external precision of our method is ±0.013‰ (1SD). The results show that δ88/86Sr values in the residue phase are much higher (0.071-1.172‰) than those in the leachate phase (0.133-0.281‰). Together with major and trace elemental data, we suggest that heavy Sr prefers to enrich in the silicates, rather than carbonate minerals, during the fractionation process. Regular variations of δ88/86Sr are observed in the spatial samples, with the leachates showing overall decreasing trends towards the lower reaches. The values of δ88/86Sr are higher in the flood season than in the dry season. We infer that parent rock types, sediment

  15. A model for the spatial distribution of snow water equivalent parameterized from the spatial variability of precipitation

    NASA Astrophysics Data System (ADS)

    Skaugen, Thomas; Weltzien, Ingunn H.

    2016-09-01

    Snow is an important and complicated element in hydrological modelling. The traditional catchment hydrological model with its many free calibration parameters, also in snow sub-models, is not a well-suited tool for predicting conditions for which it has not been calibrated. Such conditions include prediction in ungauged basins and assessing hydrological effects of climate change. In this study, a new model for the spatial distribution of snow water equivalent (SWE), parameterized solely from observed spatial variability of precipitation, is compared with the current snow distribution model used in the operational flood forecasting models in Norway. The former model uses a dynamic gamma distribution and is called Snow Distribution_Gamma, (SD_G), whereas the latter model has a fixed, calibrated coefficient of variation, which parameterizes a log-normal model for snow distribution and is called Snow Distribution_Log-Normal (SD_LN). The two models are implemented in the parameter parsimonious rainfall-runoff model Distance Distribution Dynamics (DDD), and their capability for predicting runoff, SWE and snow-covered area (SCA) is tested and compared for 71 Norwegian catchments. The calibration period is 1985-2000 and validation period is 2000-2014. Results show that SDG better simulates SCA when compared with MODIS satellite-derived snow cover. In addition, SWE is simulated more realistically in that seasonal snow is melted out and the building up of "snow towers" and giving spurious positive trends in SWE, typical for SD_LN, is prevented. The precision of runoff simulations using SDG is slightly inferior, with a reduction in Nash-Sutcliffe and Kling-Gupta efficiency criterion of 0.01, but it is shown that the high precision in runoff prediction using SD_LN is accompanied with erroneous simulations of SWE.

  16. Spatial distribution and energy deposition of precipitating Oxygen ions and their relation with the Martian crustal fields

    NASA Astrophysics Data System (ADS)

    Li, Lei; Zhang, Yiteng

    In the electromagnetic environment set by the MHD model (Ma et al.,2004), considering the dynamic feature of O+ ions, the spatial distributions and energy spectra of O+ ions impacting the atmosphere of Mars are calculated by tracing the trajectories of cold O+ ions launched from the sunlit hemisphere. The effects of the crustal fields on the spatial distribution of precipitating O+ ions are investigated by turning on or off the crustal fields. Global maps of precipitating O+ ion flux show that the crustal fields have no significant effect on the spatial distribution of lower energy precipitating ions(<100eV), while the distribution of higher energyprecipitating O+ ions (>100eV) is closely related with the distribution of the crustal fields. Most O+ ions originated in lower exosphere impact day side atmosphere before getting much energy since the electric field is weak there. O+ ions from higher source may impact the atmosphere with higher energy deposition, forming patchy precipitation regions both at dayside and nightside when the crustal fields are present. A precipitation belt formed by high energy O+ ions (around 1keV) is found near the midnight region, revealing that the crustal fields may change the electromagnetic environment near Mars significantly and result in the acceleration of precipitating O+ ions at the nightside. Together with the rotation of the planet, the consequences of the impacting of O+, including heating and sputtering of the atmosphere and ionosphere, should be much more complicated than expected.

  17. Graphite-bearing CO 2-fluid inclusions in granulites: Insights on graphite precipitation and carbon isotope evolution

    NASA Astrophysics Data System (ADS)

    Satish-Kumar, Madhusoodhan

    2005-08-01

    Graphite in deep crustal enderbitic (orthopyroxene + garnet + plagioclase + quartz) granulites (740°C, 8.9 kb) of Nilgiri hills, southern India were investigated for their spectroscopic and isotopic characteristics. Four types of graphite crystals were identified. The first type (Gr I), which is interstitial to other mineral grains, can be grouped into two subtypes, Gr IA and Gr IB. Gr IA is either irregular in shape or deformed, and rough textured with average δ 13C values of -12.7 ± 0.4‰ ( n = 3). A later generation of interstitial graphite (Gr IB) shows polygonal crystal shapes and highly reflecting smooth surface features. These graphite grains are more common and have δ 13C values of -11.9 ± 0.3‰ ( n = 14). Both subtypes show well-defined Raman shifts suggesting a highly crystalline nature. Cores of interstitial graphite grains have, on average, lower δ 13C values by ˜0.5‰ compared to that of the rim. The second type of graphite (Gr II) occurs as solid inclusions in silicate minerals, commonly forming regular hexagonal crystals with a slightly disordered structure. The third type of graphite (Gr III) is associated with solid inclusions (up to 100 μm) that have decrepitation halos of numerous small (<15 μm) satellite fluid inclusions of pure CO 2 with varying density (1.105 to 0.75 g/cm 3). The fourth type of graphite (Gr IV) is found as daughter crystals within primary type CO 2-fluid inclusions in garnet and quartz. These fluid inclusions have a range of densities (1.05 to 0.90 g/cm 3), but in general are significantly less dense than graphite-free primary, pure CO 2 fluid inclusions (1.12 g/cm 3). Raman spectral characteristics of graphite inside fluid inclusions suggest graphite crystallization at low temperature (˜ 500°C). The precipitation of graphite probably occurred during the isobaric cooling of CO 2-rich peak metamorphic fluid as a result of oxyexsolution of oxide phases. The oxyexsolution process is evidenced by the magnetite

  18. Stable isotope compositions of waters in the Great Basin, United States 2. Modern precipitation

    USGS Publications Warehouse

    Friedman, I.; Smith, G.I.; Johnson, C.A.; Moscati, R.J.

    2002-01-01

    Precipitation was collected between 1991 and 1997 at 41 locations within and adjacent to parts of the Great Basin lying in California, Oregon, Nevada, and Utah. These samples were analyzed for their deuterium (??D) and oxygen-18 (??18O) contents. Separate collections were made of summer and winter season precipitation at stations ranging in elevation from -65 m to 3246 m. The ??D per mil values of stations that were closely spaced but at different elevations showed an average ??D decrease of approximately 10???/km rise in elevation. Data for all samples representing winter precipitation, when plotted on a ??D versus ??18O plot, fall close to the Meteoric Water Line (??D = 8 ??18O + 10); samples representing summer precipitation define a line of slightly lower slope due to evaporation of the raindrops during their passage from cloud to ground. Comparison of our 1991-1997 ??D data with those from the same three stations reported by an earlier study in the southeastern California shows seasonal differences ranging from 0 per mil to 19??? (average: 15) and annual differences ranging from 0 to 13 per mil (average: 2), illustrating the degree of annual and seasonal variability in this region. When contoured, the ??D values display gradients indicating a north to northwest decrease in deuterium, with values ranging from -60 to -125??? in winter precipitation and from -40 to -110??? in summer precipitation. These gradient trends can be explained by the predominance of air mass trajectories originating in the tropical Pacific, the Gulf of California, and (in summer) the Gulf of Mexico.

  19. Disentangling Seasonality and Mean Annual Precipitation in the Indo-Pacific Warm Pool: Insights from Coupled Plant Wax C and H Isotope Measurements

    NASA Astrophysics Data System (ADS)

    Galy, V.; Oppo, D.; Dubois, N.; Arbuszewski, J. A.; Mohtadi, M.; Schefuss, E.; Rosenthal, Y.; Linsley, B. K.

    2016-12-01

    There is ample evidence suggesting that rainfall distribution across the Indo-Pacific Warm Pool (IPWP) - a key component of the global climate system - has substantially varied over the last deglaciation. Yet, the precise nature of these hydroclimate changes remains to be elucidated. In particular, the relative importance of variations in precipitation seasonality versus annual precipitation amount is essentially unknown. Here we use a set of surface sediments from the IPWP covering a wide range of modern hydroclimate conditions to evaluate how plant wax stable isotope composition records rainfall distribution in the area. We focus on long chain fatty acids, which are exclusively produced by vascular plants living on nearby land and delivered to the ocean by rivers. We relate the C (δ13C) and H (δD) isotope composition of long chain fatty acids preserved in surface sediments to modern precipitation distribution and stable isotope composition in their respective source area. We show that: 1) δ13C values reflect vegetation distribution (in particular the relative abundance of C3 and C4 plants) and are primarily recording precipitation seasonality (Dubois et al., 2014) and, 2) once corrected for plant fractionation effects, δD values reflect the amount-weighted average stable isotope composition of precipitation and are primarily recording annual precipitation amounts. We propose that combining the C and H isotope composition of long chain fatty acids thus allows independent reconstructions of precipitation seasonality and annual amounts in the IPWP. The practical implications for reconstructing past hydroclimate in the IPWP will be discussed.

  20. Defining predictand areas with homogeneous predictors for spatially coherent precipitation downscaling

    NASA Astrophysics Data System (ADS)

    Radanovics, Sabine; Vidal, Jean-Philippe; Sauquet, Eric; Ben Daoud, Aurélien; Bontron, Guillaume

    2013-04-01

    Statistical downscaling aims at finding relationships between local precipitation (predictand) and large-scale predictor fields, in various contexts, from medium-term forecasting to climate change impact studies. For distributed hydrological modelling the downscaled precipitation spatial fields have furthermore to be coherent over possibly large river basins. This study addresses this issue by grouping coherent predictand areas in terms of optimised predictor domains over the whole of France, for an analogue downscaling method developed by Ben Daoud et al. (2011). This downscaling method is based on analogies on different variables: temperature, relative humidity, vertical velocity and geopotentials. These predictor variables are taken from ERA40 at 2.5 degree resolution and local precipitation over 608 climatologically homogeneous zones in France are taken from the Safran near-surface atmospheric reanalysis (Vidal et al., 2010). The predictor domains for each zone consist of the nearest grid cell for all variables except geopotentials for which the optimum domain is sensitive to the predictand location. For large catchments with diverse meteorological influences it is thus beneficial to optimise the predictor domains individually for areas with different influences (e.g. Timbal et al., 2003). The drawback is that different predictor domains may provide inconsistent values between elementary zones. This study therefore aims at reducing the number of different predictor domains by grouping the predictand areas that may use the same predictor domain. The geopotential predictor domains were first optimised for each of the 608 zones in the Safran data separately. The predictive skill of different predictor domains is evaluated with the Continuous Ranked Probability Skill Score (CRPSS) for the 25 best analogue days found with the statistical downscaling method averaged over 20 years. Rectangular predictor domains of different sizes, shapes and locations are tested, and