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Sample records for precipitation isotope spatial

  1. Mapping the Spatial and Temporal Distribution of N and O Isotopes in Precipitation Nitrate Across the Northeastern and Mid-Atlantic United States

    NASA Astrophysics Data System (ADS)

    Elliott, E. M.; Kendall, C.; Harlin, K.; Butler, T.; Carlton, R.; Wankel, S.

    2004-12-01

    Atmospheric deposition of N is a universally important pathway by which ecosystems receive fixed, bioavailable N. Since the 1880s, atmospheric deposition of N has become increasingly important, as NOx emissions from fossil fuel combustion have steadily increased. In particular, the Northeastern and Mid-Atlantic U.S. receive some of the highest rates of nitrate wet deposition in the country, causing a cascade of detrimental effects. In order to effectively mediate the impacts of nitrate deposition, it is critical to understand the dynamics among NOx sources, atmospheric chemical transformations and transport, and the characteristics of the nitrate that is ultimately deposited. To address this need, this research takes advantage of recent methodological improvements, coupled with national networks (NADP, AIRMoN) of archived precipitation, to characterize N and O isotopic composition of nitrate in precipitation across the Northeastern and Mid-Atlantic U.S. We investigate the critical question of whether variations in \\delta15N and \\delta18O of nitrate wet deposition are mainly a function of atmospheric processes (e.g., seasonal variations in reaction pathways) or variable NOx source contributions (e.g., power plant emissions, vehicle exhaust). Spatial and seasonal variability of \\delta15N and \\delta18O is investigated using bimonthly archived samples from 2000. Furthermore, a high resolution record of daily precipitation from a single site is used to highlight within-season isotopic variability. Potential correlations between isotopic values and major NOx sources are explored using EPA datasets for monthly county-level emissions from two major NOx sources, electric generating units and on-road vehicles. Analysis of samples for \\Delta17O is in progress. A key concern regarding analysis of archived samples is nitrate preservation. We tested the stability of nitrate concentrations, and hence potential isotopic fractionations, by reanalyzing filtered, refrigerated

  2. 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.

  3. Isotopic characteristics of Indian precipitation

    NASA Astrophysics Data System (ADS)

    Kumar, Bhishm; Rai, S. P.; Kumar, U. Saravana; Verma, S. K.; Garg, Pankaj; Kumar, S. V. Vijaya; Jaiswal, Rahul; Purendra, B. K.; Kumar, S. R.; Pande, N. G.

    2010-12-01

    Hydrogen (2H/1H) and oxygen (18O/16O) isotopic ratios were measured in precipitation (900 samples) collected from several locations in India during the period 2003-2006 (12 locations in 2003 and 18 locations in 2004-2006). The amount of rainfall along with air temperature and humidity were also measured. The meteoric water line developed for India using isotopic data of precipitation samples, namely, δ2H = 7.93(±0.06) × δ18O + 9.94(±0.51) (n = 272, r2 = 0.98), differs slightly from the global meteoric water line. Regional meteoric water lines were developed for several Indian regions (i.e., northern and southern regions of India, western Himalayas) and found to be different from each other (southern Indian meteoric water line, slope is 7.82, intercept or D excess is 10.23; northern Indian meteoric water line, slope is 8.15, intercept is 9.55) which is attributed to differences in their geographic and meteorological conditions and their associated atmospheric processes (i.e., ambient temperature, humidity, organ, and source of vapor masses). The local meteoric water lines developed for a number of locations show wide variations in the slope and intercept. These variations are due to different vapor sources such as the northeast (NE) monsoon that originates in the Bay of Bengal; the southwest monsoon (SW) that originates in the Arabian Sea; a mixture of NE and SW monsoons; retreat of NE and SW monsoons and western disturbances that originate in the Mediterranean Sea. The altitude effect in the isotopic composition of precipitation estimated for western Himalayan region also varies from month to month.

  4. Canadian Network for Isotopes in Precipitation (CNIP)and Isotope Climatology and Hydroclimatology in Canada

    NASA Astrophysics Data System (ADS)

    Birks, S. J.; Edwards, T. W.; Gibson, J. J.

    2002-12-01

    The distribution of stable isotopes in precipitation provides fundamental information about the partitioning of the global atmospheric water budget, and hence about key aspects of Earth's climate, that cannot be discerned using other means. Although continuing demand exists for monitoring of isotopes in precipitation to define isotopic input functions for local hydrologic studies or for calibration of isotopic indicators of paleoclimate, based on longterm averages and climatological norms, awareness is also growing of the significant value of the monthly snapshots of the precipitation isotope field provided by the IAEA/WMO Global Network for Isotopes in Precipitation and its affiliated national networks as benchmark maps of the ongoing and dynamic evolution of the global water cycle. An initiative within the Canadian Network for Isotopes in Precipitation program includes development of a spatial and temporal database incorporating Canadian data to create a gridded isotope overlay compatible with gridded pressure and flux field data from the NCAR/CDAS Re-analysis Project. This database includes interpolated fields of our current best approximations of climatological isotopic means in addition to the original monthly data for the period 1997-2000. Studies are underway to test the sensitivity of the isotope-climate signal in precipitation to changes in these parameters utilizing perturbations in local climate arising from the El Nino/Southern Oscillation (ENSO). Intriguing results have been obtained from preliminary studies incorporating pressure and flux field data for the 1997-98 El Nino with CNIP isotope overlays. The strongest climate anomalies were found during the winter following the 1997 El Nino event, consistent with the expected strengthening of the Pacific North American pattern during this period. Comparisons of the isotopic fields with climate fields illustrate the complexity and dynamic nature of isotope climate not evident in time-series of data from

  5. Isotopic composition of precipitation in Greece

    NASA Astrophysics Data System (ADS)

    Argiriou, Athanassios A.; Lykoudis, Spyros

    2006-08-01

    SummaryThe contribution of stable isotopes in meteorological, climatological and hydrological research is well known. Until this date and despite the fact that several hydrological studies of water sources in Greece have been published, no systematic isotopic study of precipitation has been performed in the country. This paper presents all the available isotopic data collected since 1960 in several Hellenic measurement stations. This data is divided in two periods: the first covers data that was collected in the past, in the frame of a preliminary survey of the isotope composition of precipitation in the Eastern Mediterranean Sea and specific hydrological studies; the second is the result of a three-year coordinated research project of the International Atomic Energy Agency, in which the authors participated, aiming at the systematic study of stable isotopes ( 2H and 18O) and 3H in precipitation around the Mediterranean basin. No statistically significant behavior between the two periods of data was found. The isotopic content of precipitation presents characteristics intermediate of those of the Eastern and Western Mediterranean. The tritium concentration in precipitation declines as expected towards the pre-bomb levels, however there is an indication that tritium concentrations are higher in Northern Greece.

  6. On scaling in spatial precipitation from radar

    NASA Astrophysics Data System (ADS)

    Paschalis, Athanasios; Molnar, Peter; Burlando, Paolo

    2013-04-01

    The topic of self-similarity in precipitation in time and space has been prominent in precipitation research for at least the last 3 decades. Data analysts have explored evidence for self-similarity and reported departures from it. Modellers have developed stochastic models that are based on self-similarity concepts or at least reproduce the observed scaling behaviour. Physicists and meteorologists have argued why scale invariance should, or should not, exist in precipitation. Although there appears to be consensus between these communities that precipitation may exhibit scale invariance in some range of scales, most of us would probably also agree that the scaling properties are connected to the precipitation generation mechanisms (e.g. convection, orographic enhancement, etc.) and are not generally valid. The demonstration of this variability in scaling properties of precipitation and their relation to possible precipitation generating mechanisms is the focus of this paper. We analyse the spatial structure of radar precipitation for the orographically complex environment of the Swiss Alps as a multi-scaling process. A reliable 7 year long, high quality precipitation radar dataset, derived from the operational weather radars of MeteoSwiss is used to conduct a comprehensive data analysis and to reveal potential connections of the scaling processes of the precipitation structure and its respective generating mechanisms. We use different analysis techniques to quantify scale-dependent properties, from spectral analysis to multiplicative random cascades, employing estimation techniques spanning from traditional moment scaling to wavelet based estimators. We compare the results seasonally for radars in two different locations, one north and one south of the main Alpine divide, with very different topography. The main result is that distinct seasonal and spatial patterns in precipitation scaling properties exist which highlight the effect of topography on precipitation

  7. Spatial dependences among precipitation maxima over Belgium

    NASA Astrophysics Data System (ADS)

    Vannitsem, S.; Naveau, P.

    2007-09-01

    For a wide range of applications in hydrology, the probability distribution of precipitation maxima represents a fundamental quantity to build dykes, propose flood planning policies, or more generally, to mitigate the impact of precipitation extremes. Classical Extreme Value Theory (EVT) has been applied in this context by usually assuming that precipitation maxima can be considered as Independent and Identically Distributed (IID) events, which approximately follow a Generalized Extreme Value distribution (GEV) at each recording site. In practice, weather stations records can not be considered as independent in space. Assessing the spatial dependences among precipitation maxima provided by two Belgium measurement networks is the main goal of this work. The pairwise dependences are estimated by a variogram of order one, also called madogram, that is specially tailored to be in compliance with spatial EVT and to capture EVT bivariate structures. Our analysis of Belgium precipitation maxima indicates that the degree of dependence varies greatly according to three factors: the distance between two stations, the season (summer or winter) and the precipitation accumulation duration (hourly, daily, monthly, etc.). Increasing the duration (from one hour to 20 days) strengthens the spatial dependence. The full independence is reached after about 50 km (100 km) for summer (winter) for a duration of one hour, while for long durations only after a few hundred kilometers. In addition this dependence is always larger in winter than in summer whatever is the duration. An explanation of these properties in terms of the dynamical processes dominating during the two seasons is advanced.

  8. Stable isotope composition of precipitation over southeast Asia

    NASA Astrophysics Data System (ADS)

    AraguáS-AraguáS, Luis; Froehlich, Klaus; Rozanski, Kazimierz

    1998-11-01

    Spatial and temporal variability of the stable isotope composition of precipitation in the southeast Asia and western Pacific region is discussed, with emphasis on the China territory, based on the database of the International Atomic Energy Agency/World Meteorological Organization Global Network "Isotopes in Precipitation" and the available information on the regional climatology and atmospheric circulation patterns. The meteorological and pluviometric regime of southeast Asia is controlled by five different air masses: (1) polar air mass originating in the Arctic, (2) continental air mass originating over central Asia, (3) tropical-maritime air mass originating in the northern Pacific, (4) equatorial-maritime air mass originating in the western equatorial Pacific, and (5) equatorial-maritime air mass originating in the Indian Ocean. The relative importance of different air masses in the course of a given year is modulated by the monsoon activity and the seasonal displacement of the Intertropical Convergence Zone (ITCZ). Gradual rain-out of moist, oceanic air masses moving inland, associated with monsoon circulation, constitutes a powerful mechanism capable of producing large isotopic depletions in rainfall, often completely overshadowing the dependence of δ18O and δ2H on temperature. For instance, precipitation at Lhasa station (Tibetan Plateau) during rainy period (June-September) is depleted in 18O by more than 6‰ with respect to winter rainfall, despite of 10°C higher surface air temperature in summer. This characteristic isotopic imprint of monsoon activity is seen over large areas of the region. The oceanic air masses forming the two monsoon systems, Pacific and Indian monsoon, differ in their isotope signatures, as demonstrated by the average δ18O of rainfall, which in the south of China (Haikou. Hong Kong) is about 2.5‰ more negative than in the Bay of Bengal (Yangoon). Strong seasonal variations of the deuterium excess values in precipitation

  9. Spatial periphery of lithium isotopes

    SciTech Connect

    Galanina, L. I. Zelenskaja, N. S.

    2013-12-15

    The spatial structure of lithium isotopes is studied with the aid of the charge-exchange and (t, p) reactions on lithium nuclei. It is shown that an excited isobaric-analog state of {sup 6}Li (0{sup +}, 3.56MeV) has a halo structure formed by a proton and a neutron, that, in the {sup 9}Li nucleus, there is virtually no neutron halo, and that {sup 11}Li is a Borromean nucleus formed by a {sup 9}Li core and a two-neutron halo manifesting itself in cigar-like and dineutron configurations.

  10. 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.

  11. Inter-annual Variations and Trend Analyses of Precipitation and Vapor Isotopes with a Global Isotope Circulation Model and Observations

    NASA Astrophysics Data System (ADS)

    Yoshimura, K.; Oki, T.

    2006-12-01

    An atmosphere, land, sea surface, and river-coupled global isotope circulation model has been developed and it successfully reproduced spatial distribution of precipitation and vapor isotopes as well as those of "real" daily to inter-annual cycles provided by GNIP. A relationship between ENSO and simulated isotope ratio anomaly shows significant signals in DJF. They show lows in Greenland, southern USA and center of the Pacific, and highs in the northern North America, South America, and center of Asia in El Nino periods. Mostly vice versa in La Nina periods. In low latitude zones, it corresponds with the anomaly variations of precipitation amount, but in high latitudes, isotopes show original information on complex water circulation. Further investigation will be done by the presentation. Long-term trends of anomaly of precipitation isotopes are interesting, too. The observation show significant increase of precipitation isotope ratio over west Europe and the simulation agrees with it. Very simply speaking, when hydrologic cycle is enhanced, precipitation isotope will be increased, because the residence time of vapor becomes shorter. The trends in GNIP and the model is well agreed with Dirmeyer and Brubaker's (2006) finding the increase trend of recycling ratio in Northern Hemisphere. GNIP, we often regard it as "already understood", still has unknown to be tackled with.

  12. Changes in Oxygen Isotopes Composition of Precipitation over Tibetan Plateau during Cenozoic

    NASA Astrophysics Data System (ADS)

    Botsyun, S.; Sepulchre, P.; Donnadieu, Y.; Risi, C. M.; Fluteau, F.

    2014-12-01

    Despite the increasing role of the stable oxygen isotopes measurements for reconstructing mountains belts paleoelevation, some issues remain that lead to a large uncertainty in paleoelevation estimationes. Among them, the use of modern isotopic lapse rate with no account of climate change linked to lower topography can lead to misinterpretation of uplift rates. In this study, we use the atmospheric general circulation model LMDZ-iso to simulate changes in isotopic composition of precipitation due to uplift of the Himalayas and Tibetan plateau. Various scenarios of TP growth have been applied together with Paleocene, Eocene, Oligocene and Miocene boundary conditions. Our simulations allow us to estimate the magnitude of precipitation, temperature and wind field changes related to the spatial and temporal evolution of the Tibetan Plateau and Himalayas. Such changes affected the isotopic composition of precipitation during the Cenozoic.We investigate the impact of these changes on the isotopic lapse rate and the implications for paleoelevation estimates.

  13. 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.

  14. Modern monsoon extent and moisture dynamics over eastern Asian: evidence from precipitation and water vapor isotopes

    NASA Astrophysics Data System (ADS)

    Liu, Zhongfang; Kei, Yoshimura; Bowen, Gabriel J.; Tian, Lide

    2013-04-01

    The climate of eastern Asia is dominated by the Asia monsoon (AM) system, which controls seasonal patterns of moisture sources and transport to the region. Measurements of water isotopes can provide insight into monsoon extent and moisture dynamics. Here we present an analysis of a spatially dense network of precipitation isotopes (d18O and dD) from a ground-based network and water vapor dD retrieved from satellite measurements. The results show that isotopic seasonality for both precipitation and water vapor exhibits two distinctly different, spatially coherent modes. Summer-season isotope ratios are relatively low to the south of ~35°N and high to the north, with the transition between these zones reflecting the approximate northward extent of Asia summer monsoon influence. In the southern monsoon domain, low isotope values with relatively low precipitation d-excess (9.4‰ in SE China) in summer appear not to reflect the amount effect, but rather the dominance of monsoon moisture with long-distance transport from the Indian and southern Pacific oceans and continental convective recycling (contribute to about 30-48% moisture in SE China). In contrast, other seasons are dominated by dry continental masses, characterized by high d-excess (12.7‰) and isotope values. In northern China, a region that is beyond extent of monsoon, the moisture is derived overwhelmingly from the dry continental air masses. Here, water isotope ratios exhibit stronger temperature dependence, with enriched values in summer and depleted values in other seasons. The relatively low precipitation d-excess (<8‰) in northern China and inverse spatial isotope patterns between precipitation and water vapor across China during the summer further suggest that re-evaporation of falling raindrops is a key driver of water isotope behavior in northern China.

  15. 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.

  16. Isotopic content of mixed-phase orographic precipitation

    NASA Astrophysics Data System (ADS)

    Blossey, P. N.; Moore, M.; Kuang, Z.; Muhlbauer, A. D.

    2014-12-01

    The isotopic content of mixed-phase orographic precipitation is explored in idealized simulations using the Weather Research and Forecasting Model (WRF). The isotopic exchanges among water vapor, hydrometeors and precipitation have been fully integrated into the Thompson microphysics scheme, including both fractionating (e.g., vapor deposition) and non-fractionation (e.g., melting/freezing) processes. The stable isotopes of water, HDO and H2O18, are included in the present study. The deviation of the isotopic content from linear theory predictions is studied, following Galewsky (2009, doi:10.1130/G30008A.1). The main focus, however, is on the response of orographic precipitation to aerosols and the impact of this response on the isotopic content of the precipitation. Changes in the prescribed cloud droplet number concentration are used as a proxy for changes in background aerosol concentrations. Elevated droplet concentrations lead to a decrease in precipitation over the mountain barrier and a shift of precipitation towards the lee side. In addition, the precipitation over the mountain itself becomes more depleted at some locations.

  17. 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.

  18. 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

  19. 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.

  20. Proportions of convective and stratiform precipitation revealed in water isotope ratios

    NASA Astrophysics Data System (ADS)

    Aggarwal, Pradeep K.; Romatschke, Ulrike; Araguas-Araguas, Luis; Belachew, Dagnachew; Longstaffe, Frederick J.; Berg, Peter; Schumacher, Courtney; Funk, Aaron

    2016-08-01

    Tropical and midlatitude precipitation is fundamentally of two types, spatially limited and high-intensity convective or widespread and lower-intensity stratiform, owing to differences in vertical air motions and microphysical processes governing rain formation. These processes are difficult to observe or model and precipitation partitioning into rain types is critical for understanding how the water cycle responds to changes in climate. Here, we combine two independent data sets--convective and stratiform precipitation fractions, derived from the Tropical Rainfall Measuring Mission satellite or synoptic cloud observations, and stable isotope and tritium compositions of surface precipitation, derived from a global network--to show that isotope ratios reflect rain type proportions and are negatively correlated with stratiform fractions. Condensation and riming associated with boundary layer moisture produces higher isotope ratios in convective rain, along with higher tritium when riming in deep convection occurs with entrained air at higher altitudes. On the basis of our data, stable isotope ratios can be used to monitor changes in the character of precipitation in response to periodic variability or changes in climate. Our results also provide observational constraints for an improved simulation of convection in climate models and a better understanding of isotope variations in proxy archives, such as speleothems and tropical ice.

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. Microphysical controls on the isotopic composition of wintertime orographic precipitation

    NASA Astrophysics Data System (ADS)

    Moore, M.; Blossey, P. N.; Muhlbauer, A.; Kuang, Z.

    2016-06-01

    The sensitivity of mixed-phase orographic clouds, precipitation, and their isotopic content to changes in dynamics, thermodynamics, and microphysics is explored in idealized two-dimensional flow over a mountain barrier. These simulations use the Weather Research and Forecasting (WRF) model with stable water isotopologues (HDO and H218O), which have been integrated into the Thompson microphysics scheme within WRF as part of the present project. In order to understand how the isotopic composition of precipitation (δ18Oprecip) is fixed, the mountain height, temperature, and the prescribed cloud droplet number concentration (CDNC) have been varied in a series of simulations. For the given range of values explored in this work, changes in mountain height and temperature induce stronger responses in domain-averaged δ18Oprecip than do changes in CDNC by a factor of approximately 10. The strongest response to changing CDNC leads to local variations of δ18Oprecip of about 3‰, though those occur in regions of weak precipitation (<0.1 mm h-1). Changes in δ18Oprecip can be understood through the microphysical pathways by which precipitable hydrometeors are formed and by the isotopic signature associated with each pathway. The decrease in δ18Oprecip with increasing mountain height is not just a function of decreasing temperature but also reflects the changing contributions and distinct isotopic signatures of riming of cloud liquid and vapor deposition onto snow, the leading sources of precipitation in these simulations. The changes in δ18Oprecip with mountain height, temperature, and CDNC are governed in part by the microphysical pathways through which precipitating hydrometeors are formed and grow.

  6. 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. PMID:23937110

  7. New approaches to paleothermometry from isotopes in precipitation

    NASA Astrophysics Data System (ADS)

    Steig, E. J.

    2015-12-01

    Water isotope ratios in precipitation have been used as paleothermometers for at least 50 years. Most temperature reconstructions using isotope ratios rely on the empirical observation of a correlation between isotope ratios and temperature. While this approach is supported by theoretical considerations, it is nevertheless inherently imprecise because the correlation arises from myriad processes in the atmosphere that cannot be direclty quantified. In this talk, I will discuss two major innovations in the use of isotope ratios to obtain paleotemperature from ice cores. First, the measurement of very high resolution isotope records allows for the determination of the diffusion length (the amount of isotope diffusion that has occurred), which is strongly dependent on temperature. Second, the novel measurement of the third naturally occuring isotope of oxygen -- oxygen 17 -- allows the measurement of the oxygen-17 excess, which provides new constraints temperature because it depends strongly on the temperature-dependent supersaturation. Both these approaches have a stronger theoretical foundation than the tradiational δ18O method, and have the potential to be both more accurate and precise.

  8. 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

  9. 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.

  10. 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

  11. Isotopic variation in Indian Monsoon precipitation: Records from Bombay and New Delhi

    NASA Astrophysics Data System (ADS)

    Bhattacharya, S. K.; Froehlich, K.; Aggarwal, P. K.; Kulkarni, K. M.

    2003-12-01

    The stable isotope composition and the tritium content of precipitation analysed within the framework of the IAEA/WMO Global Network for Isotopes in Precipitation (GNIP) have been evaluated for the Indian stations Bombay and New Delhi representing two different regions of the Indian Monsoon. The rainfall at New Delhi is controlled by north-west moving depressions with diverse routes and variable transit times over the land subsequent to their formation at the head of Bay of Bengal. In contrast, Bombay rains are caused by spatially locked cyclonic vortices on the west coast of India with continuous supply of oceanic moisture resulting in negligible isotopic variation over the rainy months. The evaluation of the long-term isotope data of the two stations provided specific information on monsoon rain formation mechanism and the moisture source of the monsoon rains. The average isotope ratios clearly represent an imprint of oceanic moisture during the summer monsoon and of continental moisture during the winter monsoon period. The rainout efficiency is about 30% in case of Bombay (representative of west coast region) and about 56% in case of New Delhi (representative of north Indian Plains). Furthermore, the isotope data indicate that the moisture for low-intensity rains during the post-monsoon phase originates from the Asian continent.

  12. Impact of elevation and weather patterns on the isotopic composition of precipitation in a tropical montane rainforest

    NASA Astrophysics Data System (ADS)

    Windhorst, D.; Waltz, T.; Timbe, E.; Frede, H.-G.; Breuer, L.

    2013-01-01

    This study presents the spatial and temporal variability of δ18O and δ2H isotope signatures in precipitation of a south Ecuadorian montane cloud forest catchment (San Francisco catchment). From 2 September to 25 December 2010, event sampling of open rainfall was conducted along an altitudinal transect (1800 to 2800 m a.s.l.) to investigate possible effects of altitude and weather conditions on the isotope signature. The spatial variability is mainly affected by the altitude effect. The event based δ18O altitude effect for the study area averages -0.22‰ × 100 m-1 (δ2H: -1.12‰ × 100 m-1). The temporal variability is mostly controlled by prevailing air masses. Precipitation during the times of prevailing southeasterly trade winds is significantly enriched in heavy isotopes compared to precipitation during other weather conditions. In the study area, weather during austral winter is commonly controlled by southeasterly trade winds. Since the Amazon Basin contributes large amounts of recycled moisture to these air masses, trade wind-related precipitation is enriched in heavy isotopes. We used deuterium excess to further evaluate the contribution of recycled moisture to precipitation. Analogously to the δ18O and δ2H values, deuterium excess is significantly higher in trade wind-related precipitation. Consequently, it is assumed that evaporated moisture is responsible for high concentrations of heavy isotopes during austral winter.

  13. Impact of elevation and weather patterns on the isotopic composition of precipitation in a tropical montane rainforest

    NASA Astrophysics Data System (ADS)

    Windhorst, D.; Waltz, T.; Frede, H.-G.; Breuer, L.

    2012-07-01

    This study presents the spatial and temporal variability of δ18O and δ2H isotope signatures in precipitation of a south Ecuadorian montane cloud forest catchment (San Francisco Catchment). From 2 September to 25 December 2010, event sampling of open rainfall was conducted along an altitudinal transect (1800 m a.s.l. to 2800 m a.s.l.) to investigate possible effects of altitude and weather conditions on the isotope signature. The spatial variability is mainly affected by the altitude effect. The event based δ18O altitude effect for the study area averages -0.22‰ × 100 m-1 (δ2H: -1.12‰ × 100 m-1). The temporal variability is mostly controlled by prevailing air masses. Precipitation during the times of prevailing southeasterly trade winds is significantly enriched in heavy isotopes compared to precipitation during other weather conditions. In the study area, weather during austral winter is commonly controlled by southeasterly trade winds. Since the Amazon Basin contributes large amounts of recycled moisture to these air masses, trade wind-related precipitation is enriched in heavy isotopes. We used deuterium excess to further evaluate the contribution of recycled moisture to precipitation. Analogously to the δ18O and δ2H values, deuterium excess is significantly higher in trade wind related precipitation. Consequently, it is assumed that evaporated moisture is responsible for high concentrations of heavy isotopes during austral winter.

  14. 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

  15. 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

  16. 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).

  17. Spatial and temporal changes in precipitation in Tuscany

    NASA Astrophysics Data System (ADS)

    Fatichi, S.; Caporali, E.

    2009-04-01

    Climate change implications and detections are becoming an important field of research, and climate change science interests not only scientists and specialists but also national governments and common people. An important issue related to this science is covered by the modification of precipitation regime and their repercussions in term of drought periods, water resources availability or flood risk modification. The general lack of long sequences of data increase the difficulties in analyze long periods of climatic events. Here the authors provide a spatial analysis of trends in 6 indexes of precipitation regime. Through spatial interpolation techniques, a specific methodology is adopted to use more data than usual, which include the gauges with very short time series, even only 1 year long. The six indexes are: Total Annual Precipitation (TAP), the number of wet days (precipitation > 1 mm), the Precipitation Concentration Index (PCI), the number of days with more than 10 mm of precipitation, the maximum number of consecutive dry days (precipitation < 1 mm) and the Standardized Precipitation Index (SPI). The analyzed region is Tuscany, in the central part of Italy, with a dataset of 785 recording rain gauges, covering mainly the second half of 20th century. The Mann-Kendall test, modified to take into account the autocorrelation on the data, is employed for the distributed trend analyses. The results do not show any clear signal of changes in the precipitation in Tuscany during the last century. Effects of climate modifications in the analyzed region are not significant through the precipitation.

  18. Climatic significance of stable isotopes in precipitation from western Romania

    NASA Astrophysics Data System (ADS)

    Ersek, Vasile; Onac, Bogdan

    2016-04-01

    The oxygen and deuterium (δ18O and δD) isotopic composition of meteoric precipitation has been used as proxy to advance our understanding of past and present atmospheric circulation. Precipitation δ18O is a primary control on cave speleothem δ18O which is one of the main methods used to reconstruct past climatic variability on a variety of timescales. Here we present δ18O and δD in precipitation and cave drip waters from Urşilor Cave located in the Apuseni Mountains, western Romania in order to better understand the relationship between climate and speleothem δ18O at this site. Samples of weekly precipitation and cave drip water (4-day intervals) were collected between July 2010 and June 2011. In order to draw robust palaeoclimatic information from speleothems at Ursilor Cave we aim to establish the climatic controls on δ18O composition of precipitation in western Romania and determine the source of air masses delivering moisture at our site. Furthermore, we evaluate the extent to which any climatic signature is preserved in the drip waters from which the speleothem calcite precipitates.

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

    NASA Astrophysics Data System (ADS)

    Wang, Tao; Chen, Jiansheng; Li, Ling

    2016-08-01

    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.

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

    PubMed

    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 (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. PMID:27507656

  1. 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

  2. [Variations and simulation of stable isotopes in precipitation in the Heihe River basin].

    PubMed

    Wu, Jin-Kui; Yang, Qi-Yue; Ding, Yong-Jian; Ye, Bai-Sheng; Zhang, Ming-Quan

    2011-07-01

    To study the variations of deltaD and delta18O in precipitation, 301 samples were sampled during 2002-2004 in 6 sites in the Heihe River basin, Northwestern China. The deltaD and delta18O values ranged from 59 per thousand to -254 per thousand and 6.5 per thousand to -33.4 per thousand, respectively. This wide range indicated that stable isotopes in precipitation were controlled by different condensation mechanisms as a function of air temperature and varying sources of moisture. delta18O in precipitation had a close positive relationship with the air temperature, i. e., a clear temperature effect existed in this area. At a monthly scale, no precipitation effect existed. On the other hand, a weak precipitation effect still accrued at precipitation events scale. The spatial variation of delta18O showed that the weighted average delta18O values decreased with the increasing altitude of sampling sites at a gradient of -0. 47 per thousand/100m. A regional Meteoric Water Line, deltaD = 7.82 delta18O + 7.63, was nearly identical to the Meteoric Water Line in the Northern China. The results of backward trajectory of each precipitation day at Xishui showed that the moisture of the precipitation in cold season (October to March) mainly originated from the west while the moisture source was more complicated in warm season (April to September). The simulation of seasonal delta18O variation showed that the stable isotope composition of precipitation tended to a clear sine-wave seasonal variation. PMID:21922801

  3. 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

  4. Cenozoic climate evolution in Asian region and its influence on isotopic composition of precipitation

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    The evolution of Asian climate during the Cenozoic as well as the onset of monsoon systems in this area is highly debated. Factors that control climate include the geographical position of continents, the land-sea distribution and altitude of orogens. In tern, several climatic parameters such as air temperature, precipitation amount and isotopic fractionation through mass-dependent processes impact precipitation δ18O lapse rate. Stable oxygen paleoaltimetry is considered to be a very efficient and widely applied technique, but the link between stable oxygen composition of precipitation and climate is not well established. To quantify the influence of paleogeography changes on climate and precipitation δ18O over Asia, the atmospheric general circulation model LMDZ-iso, with embedded stable oxygen isotopes, was used. For more realistic experiments, sea surface temperatures were calculated with the fully coupled model FOAM. Various scenarios of TP growth have been applied together with Paleocene, Eocene, Oligocene and Miocene boundary conditions. The results of our numerical modelling show a significant influence of paleogeography changes on the Asian climate. The retreat of the Paratethys ocean, the changes in latitudinal position of India, and the height of the Tibetan Plateau most likely control precipitation patterns over Asia and cause spatial and temporal isotopic variations linked with the amount effect. Indian Ocean currents restructuring during the Eocene induces a substantial warming over Asian continent. The adiabatic and non-adiabatic temperature effects explain some of δ18O signal variations. We highlight the importance of these multiple factor on paleoelevations estimates derived using oxygen stable isotopes.

  5. 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.

  6. 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

  7. Orbital-scale summer precipitation and temperature variability in central China reconstructed with leaf wax hydrogen isotopes and branched GDGTs

    NASA Astrophysics Data System (ADS)

    Thomas, E. K.; Clemens, S. C.; Prell, W. L.; Sun, Y.; Huang, Y.

    2013-12-01

    Reconstructions of monsoon variability on orbital time scales inform how the monsoon responds to large variations in forcing mechanisms (e.g., insolation, ice volume, greenhouse gases). The timing, or phase, of proxy response relative to forcing mechanisms (e.g., maximum insolation, maximum ice volume) can provide insights into which mechanisms control monsoon variability. Furthermore, obtaining summer monsoon records from different regions of Asia provides information about the spatial expression of monsoon variability. Deciphering which mechanisms control orbital-scale summer monsoon variability, however, requires reconstructions using proxies that respond mainly to summer monsoon variability. We present a 300-kyr-long, millennial-resolution record of Pleistocene summer monsoon precipitation variability on the Chinese Loess Plateau, generated using leaf wax hydrogen isotopes. The loess plateau receives ca. 50% of total annual precipitation during the summer monsoon, and plants produce leaf waxes during the warm, wet summer months. Thus, leaf wax hydrogen isotopes reflect summer precipitation isotopes. Precipitation isotopes change in response to changes in transport history (e.g. source water isotope ratios, transport path, etc.), which is influenced by changes in monsoon strength. Precipitation isotopes are also affected by local condensation temperature, which we account for using an independent temperature proxy, branched glycerol dialkyl glycerol tetraethers. We present these independent monsoon and temperature records and examine implications for mechanisms controlling monsoon variability in central China.

  8. 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

  9. 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

  10. Seasonality of isotopes in precipitation: A global perspective

    NASA Astrophysics Data System (ADS)

    Feng, Xiahong; Faiia, Anthony M.; Posmentier, Eric S.

    2009-04-01

    We use data from Global Network of Isotopes in Precipitation (GNIP) database to explore how the atmosphere's meridional circulation cells control the latitudinal and seasonal distribution of δ18O and d-excess in precipitation. We demonstrate that the atmospheric general circulation (AGC) cells determine variations of zonally averaged isotopic composition of meteoric water; the local isotopic minimum near the equator coincides with the intertropical convergence (ITC), and two maxima on either side of the ITC coincide with the subtropical highs (STHs). Both the ITC and STHs migrate cum sole, as part of the systematic annual migration of the meridional cells. This migratory circulation pattern controls the phase of the annual oscillation of the precipitation δ18O. At latitudes equatorward of the STHs, δ18O reaches its maximum in the winter of the respective hemisphere and at higher latitudes in the summer. From the monthly latitudinal distribution of the vertical velocity at the 500-hPa level, we obtain the seasonal variations of the latitudinal positions of the subtropical moisture source regions and their climates. The sea surface temperature and relative humidity at the moisture source regions are used to predict seasonal changes of the d-excess of water vapor evaporated from the source regions. The GNIP data is consistent with the predicted phase of the d-excess. However, the observed magnitude of the seasonal oscillation is greater than the predicted values. This work provides a baseline for understanding the influence of subtropical moisture source regions and other climatological factors on the d-excess.

  11. A model of the spatial distribution of ammonium in precipitation

    SciTech Connect

    Liljestrand, H.M.

    1986-04-01

    The net acidity of precipitation depends on both acid and base contributions, with ammonia being one of the two major bases. A model of ammonium concentrations in precipitation is developed from estimates of the spatial and seasonal emission densities of NH/sub 3/ across the continental United States. Box models are used to determine the transport, reactions and distribution between gaseous and particulate phases. An acid-base scavenging model is developed to estimate area average ammonium concentrations in precipitation. Model predictions are compared with historical data.

  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. 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.

  15. Event Detection and Spatial Analysis for Characterizing Extreme Precipitation

    NASA Astrophysics Data System (ADS)

    Jeon, S.; Prabhat, M.; Byna, S.; Collins, W.; Wehner, M. F.

    2013-12-01

    Atmospheric Rivers (ARs) are large spatially coherent weather systems with high concentrations of elevated water vapor that often cause severe downpours and flooding over western coastal United States. With the availability of more atmospheric moisture in the future under global warming, we expect ARs to play an important role as a potential cause of extreme precipitation. We have recently developed TECA software for automatically identifying and tracking features in climate datasets. In particular, we are able to identify ARs that make landfall on the western coast of North America. This detection tool examines integrated water vapor field above a certain threshold and performs geometric analysis. Based on the detection procedure, we investigate impacts of ARs by exploring spatial extent of AR precipitation for CMIP5 simulations, and characterize spatial pattern of dependence for future projections under climate change within the framework of extreme value theory. The results show that AR events in RCP8.5 scenario (2076-2100) tend to produce heavier rainfall with higher frequency and longer duration than the events from historical run (1981-2005). Range of spatial dependence between extreme precipitations is concentrated on smaller localized area in California under the highest emission scenario than present day. Preliminary results are illustrated in Figure 1 and 2. Fig 1: Boxplot of annual max precipitation (left two) and max AR precipitation (right two) from GFDL-ESM2M during 25-year time period by station in California, US. Fig 2: Spatial dependence of max AR precipitation calculated from Station 4 (triangle) for historical run (left) and for future projections of RCP8.5 (right) from GFDL-ESM2M. Green and orange colors represent complete dependence and independence between two stations respectively.

  16. 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. PMID:26573310

  17. 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

  18. 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

  19. SPATIAL AND TEMPORAL PATTERNS OF ACID PRECIPITATION AND THEIR INTERPRETATION

    EPA Science Inventory

    Using data compiled from seven nationwide precipitation chemistry networks in the U.S. and Canada, the spatial distribution of hydrogen, sulfate, and nitrate ions in North America is discussed. Geographic patterns of concentration and deposition are characterized using isopleth m...

  20. 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 ...

  1. Seasonal and diurnal spatial patterns of precipitation frequency from the TRMM Precipitation Radar

    NASA Astrophysics Data System (ADS)

    Yuter, Sandra; Biasutti, Michela; Sobel, Adam; Burleyson, Casey

    2010-05-01

    The detailed spatial distribution of rainfall is currently poorly understood over the oceans and for land regions without routine precipitation observation infrastructure. Many of these poorly observed areas are in the tropics where most of the global precipitation occurs. NASA's Tropical Rainfall Measuring Mission (TRMM) satellite was launched in 1997 and continues to operate. TRMM carries the first space-borne Precipitation Radar (PR) which provides high spatial resolution data of the vertical structure of precipitation. We utilize TRMM PR orbit data to construct 5 km x 5 km grids of precipitation statistics over several tropical regions. We focus on several statistics derived from over 10 years of TRMM PR data --the frequency of precipitation above a threshold corresponding to ~0.4 mm/hr, the conditional rain rate near the surface, and conditional radar reflectivities at 3 km and 6 km altitude. Maps of seasonal precipitation frequency reveal the expected large-scale latitudinal variations of the ITCZ and monsoon as well as smaller scale regional precipitation patterns related to sea and land breezes and mountain upslope and downslope flow. In comparison, maps of conditional rain rates and reflectivities indicate less regional variation and primarily illustrate differences between continental and oceanic precipitation. Use of a single satellite-based precipitation instrument over the global tropics facilitates intercomparison among geographic regions. In Asia and the Maritime Continent, there are very high frequencies of precipitation off the coast of Myanmar north toward Bangladesh and off the west coast of Sumatra. The precipitation frequencies off the coast of Myanmar are likely associated with a land breeze but are comparable in magnitude to those for orographic precipitation. The Central Range of the island of New Guinea exhibits a strong diurnal cycle with the precipitation near the crest during day associated with upslope flow and similar magnitude

  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. 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.

  4. Exploring R for modeling spatial extreme precipitation data

    NASA Astrophysics Data System (ADS)

    Gomes, Dora Prata; Neves, Manuela

    2014-10-01

    Natural hazards such as high rainfall and windstorms arise due to physical processes and are usually spatial in its nature. Classical geostatistics, mostly based on multivariate normal distributions, is inappropriate for modeling tail behavior. Several methods have been proposed for the spatial modeling of extremes, among which max-stable processes are perhaps the most well known. They form a natural class of processes extending extreme value theory when sample maxima are observed at each site of a spatial process. Jointly with the theoretical framework for modeling and characterizing measures of dependence of those processes, to deal with free and open-source software is of great value for practitioners. In this note, we illustrate how R can be used for modeling spatial extreme precipitation data.

  5. Stable isotopic study of precipitation and spring discharge on the Nevada Test Site

    SciTech Connect

    Ingraham, N.L.; Jacobson, R.L.; Hess, J.W.; Lyles, B.F. . Water Resources Center Nevada Univ., Reno, NV . Water Resources Center)

    1990-07-01

    Precipitation was collected in southern Nevada (on the Nevada Test Site) on a semi-regular monthly basis at 41 locations for six years for stable isotopic analysis. The precipitation record shows two time-based regimes. For the first three years of collection, the precipitation was highly variable with several large events and several dry periods. During the last three years of collection, the precipitation was much more even with no large events. However, there is no correlation between the variability in the amount of precipitation and the stable isotopic composition of precipitation. In addition, the oxygen isotope composition and discharge of two springs, Whiterock Spring and Cane Spring, issuing from perched water tables, were monitored for five years in a similar time frame as for the precipitation. 17 refs., 42 figs., 3 tabs.

  6. Spatial and diurnal variation of precipitation systems over Asia observed by the TRMM Precipitation Radar

    NASA Astrophysics Data System (ADS)

    Hirose, Masafumi; Nakamura, Kenji

    2005-03-01

    The spatial and diurnal variation of rainfall over Asia was investigated using the spaceborne radar data for four seasons during 1998-2003. The regional variation of the prevailing precipitation systems most closely associated with the maximum hourly rainfall was shown by examining the fine spatial distribution of rainfall amount and scale-based precipitation systems. Small precipitation systems (<102 km2) occurred most frequently around early afternoon over most land. The south facing slopes of the Himalayas, especially south of Mount Everest and the upper portion of the Brahmaputra valley, is the most obvious region of the daytime genesis of the convective systems over the Asian landmass. Over the Tibetan Plateau the occurrence of the small systems was larger than over inland India and the foothills. Large systems (>104 km2) developed mostly in the evening over nearly flat landmasses. Wide-spread systems with intense rain pixels developed over the foothills of the Himalayas in late night-early morning period, which was distinct from the daytime convection. Over ocean, in addition to the morning signature, spatially inhomogeneous and systematic characteristics were evident over the offshore region, for example, around the maritime continent. Large systems, which are strongly associated with terrain, have a great influence on the total number of rain pixels and the total amount of rainfall. For 86% of the region where large system is dominant the time of maximum rainfall is within 3 hours of the time of maximum rainfall for large systems.

  7. Spatial regression models for extreme precipitation in Belgium

    NASA Astrophysics Data System (ADS)

    van de Vyver, H.

    2012-09-01

    Quantification of precipitation extremes is important for flood planning purposes, and a common measure of extreme events is the T year return level. Extreme precipitation depths in Belgium are analyzed for accumulation durations ranging from 10 min to 30 days. Spatial generalized extreme value (GEV) models are presented by considering multisite data and relating GEV parameters to geographical/climatological covariates through a common regression relationship. Methods of combining data from several sites are in common use, and in such cases, there is likely to be nonnegligible intersite dependence. However, parameter estimation in GEV models is generally done with the maximum likelihood estimation method (MLE) that assumes independence. Estimates of uncertainty are adjusted for spatial dependence using methodologies proposed earlier. Consistency of GEV distributions for various durations is obtained by fitting a smooth function to the preliminary estimations of the shape parameter. Model quality has been assessed by various statistical tests and indicates the relevance of our approach. In addition, a methodology is applied to account for the fact that measurements have been made in fixed intervals (usually 09:00 UTC-09:00 UTC). The distribution of the annual sliding 24 h maxima was specified through extremal indices of a more than 110 year time series of 24 h aggregated 10 min rainfall and daily rainfall. Finally, the selected models are used for producing maps of precipitation return levels.

  8. A spatial hybrid approach for downscaling of extreme precipitation fields

    NASA Astrophysics Data System (ADS)

    Bechler, Aurélien; Vrac, Mathieu; Bel, Liliane

    2015-05-01

    For a few decades, climate models are used to provide future scenarios of precipitation with increasingly higher spatial resolution. However, this resolution is not yet sufficient to describe efficiently what happens at local scale. Dynamical and statistical methods of downscaling have been developed and allow us to make the link between two levels of resolution and enable us to get values at a local scale based on large-scale information from global or regional climate models. Nevertheless, both the extreme behavior and the spatial structures are not well described by these downscaling methods. We propose a two-step methodology, called spatial hybrid downscaling (SHD), to solve this problem. The first step consists in applying a univariate (i.e., one-dimensional) statistical downscaling to link the high- and low-resolution variables at some given locations. Once this 1d-link is performed, a conditional simulation algorithm of max-stable processes adapted to the extremal t process enables us to get conditional distributions of extreme precipitation at any point of the region. An application is performed on precipitation data in the south of France where extreme (Cevenol) events have major impacts (e.g., floods). Different versions of the SHD approach are tested. Most of them show particularly good results regarding univariate and multivariate criteria and overcome classical downscaling techniques tested in comparison. Furthermore, these conclusions are robust to the choice of the 1d-link functions tested and to the choice of the conditioning points to drive the conditional local-scale simulations performed by the SHD approach.

  9. 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.

  10. 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

  11. Climatic Controls on the Stable Isotopic Composition of Precipitation in Northeast Asia : applicability to groundwater recharge study

    NASA Astrophysics Data System (ADS)

    Lee, K.; Wenner, D. B.; Grunstein, A. J.; Choi, M.; Woo, N.

    2001-05-01

    Based on the data available from the IAEA/WMO Global Network for Isotopes in Precipitation (GNIP), spatial and temporal variability of oxygen and hydrogen isotope composition of precipitation is reviewed for 9 selected sites in the Northeast Asia. These sites include Pohang (Korea), Tokyo and Ryori (Japan) and Shijiazhuang, Baotou, Tianjin, Wulumuqi, Zhangye and Qiqihar (China). The temperature is 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 IAEA/WMO data set reveals that many sites in Northeast Asia show a distinct winter-summer cyclic pattern in deuterium excess values that appears to reflect different climatic conditions. To further understand this pattern, stable isotopic data were obtained for individual rainfall events over a two-year period at Cheju Island, Korea. The d18- and dD- values of precipitation at Cheju Island are not dependent upon temperature. However, the deuterium excess values, which range from 3.0 to 40.6 per mil show a distinct seasonal variation with higher d-values in winter (> ~15 per mil) and lower values in summer (~10 permil). Such a seasonal variation appears to be closely related to different air masses affecting the island during different seasons: cold-dry continental polar air mass in winter and hot-humid maritime tropical air mass in summer. Such stable isotopic characteristics in Northeast Asia could potentially provide a means for evaluating the relative contribution of summer and winter precipitation to groundwater recharge.

  12. 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.

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

    PubMed

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

    2015-04-01

    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. PMID:25782104

  14. 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.

  15. 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.

  16. 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).

  17. Mapping Precipitation Patterns from the Stable Isotopic Composition of Surface Waters: Olympic Peninsula, Washington State

    NASA Astrophysics Data System (ADS)

    Anders, A. M.; Brandon, M. T.

    2008-12-01

    Available data indicate that large and persistent precipitation gradients are tied to topography at scales down to a few kilometers, but precipitation patterns in the majority of mountain ranges are poorly constrained at scales less than tens of kilometers. A lack of knowledge of precipitation patterns hampers efforts to understand the processes of orographic precipitation and identify the relationships between geomorphic evolution and climate. A new method for mapping precipitation using the stable isotopic composition of surface waters is tested in the Olympic Mountains of Washington State. Measured δD and δ18O of 97 samples of surface water are linearly related and nearly inseparable from the global meteoric water line. A linear orographic precipitation model extended to include in effects of isotopic fractionation via Rayleigh distillation predicts precipitation patterns and isotopic composition of surface water. Seven parameters relating to the climate and isotopic composition of source water are used. A constrained random search identifies the best-fitting parameter set. Confidence intervals for parameter values are defined and precipitation patterns are determined. Average errors for the best-fitting model are 4.8 permil in δD. The difference between the best fitting model and other models within the 95% confidence interval was less than 20%. An independent high-resolution precipitation climatology documents precipitation gradients similar in shape and magnitude to the model derived from surface water isotopic composition. This technique could be extended to other mountain ranges, providing an economical and fast assessment of precipitation patterns requiring minimal field work.

  18. A preliminary characterization of the spatial variability of precipitation at Yucca Mountain, Nevada

    SciTech Connect

    Hevesi, J.A.; Flint, A.L.; Ambos, D.S.

    1994-12-31

    Isohyetal maps of precipitation and numerical models for simulating precipitation are needed to characterize natural infiltration at Yucca Mountain, Nevada. The objective of this study was to characterize the spatial variability of precipitation within the domain of the natural catchments overlying the potential repository, and to define preliminary geostatistical models based on differences in storm type for the numerical simulation of precipitation.

  19. 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

  20. 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.

  1. Spatial distribution of stable water isotopes in alpine snow cover

    NASA Astrophysics Data System (ADS)

    Dietermann, N.; Weiler, M.

    2013-07-01

    The aim of this study was to analyse and predict the mean stable water isotopic composition of the snow cover at specific geographic locations and altitudes. In addition, the dependence of the isotopic composition of the entire snow cover on altitude was analysed. Snow in four Swiss catchments was sampled at the end of the accumulation period in April 2010 and a second time during snowmelt in May 2010 and analysed for stable isotope composition of 2H and 18O. The sampling was conducted at both south-facing and north-facing slopes at elevation differences of 100 m, for a total altitude difference of approximately 1000 m. The observed variability of isotopic composition of the snow cover was analysed with stepwise multiple linear regression models. The analysis indicated that there is only a limited altitude effect on the isotopic composition when considering all samples. This is due to the high variability of the isotopic composition of the precipitation during the winter months and, in particular in the case of south-facing slopes, an enrichment of heavy isotopes due to intermittent melting processes. This enrichment effect could clearly be observed in the samples which were taken later in the year. A small altitudinal gradient of the isotopic composition could only be observed at some north-facing slopes. However, the dependence of snow depth and the day of the year were significant predictor variables in all models. This study indicates the necessity to further study the variability of water isotopes in the snow cover to increase prediction for isotopic composition of snowmelt and hence increase model performance of residence time models for alpine areas in order to better understand the accumulation processes and the sources of water in the snow cover of high mountains.

  2. Spatial distribution of stable water isotopes in alpine snow cover

    NASA Astrophysics Data System (ADS)

    Dietermann, N.; Weiler, M.

    2013-03-01

    The aim of this study was to analyze and predict the mean stable water isotopic composition of the snow cover at specific geographic locations and altitudes. In addition, the dependence of the isotopic composition of the entire snow cover on altitude was analyzed. Snow in four Swiss catchments was sampled at the end of the accumulation period in April 2010 and a second time in Mai 2010 and analyzed for stable isotope composition of 2H and 18O. The sampling was conducted at both south-facing and north-facing slopes at elevation differences of 100 m for a total altitude difference of approximately 1000 m. The observed variability of isotopic composition of the snow cover was analyzed with stepwise multiple linear regression models. The analysis indicated that there is only a limited altitude effect on the isotopic composition when considering all samples. This is due to the high variability of the isotopic composition of the precipitation during the winter months and, in particular in the case of south-facing slopes, an enrichment of heavy isotopes due to intermittent melting processes. This enrichment effect could clearly be observed in the samples which were taken later in the year. A small altitudinal gradient of the isotopic composition could only be observed at some north-facing slopes. However, the dependence of snow depth and the day of the year were significant predictor variables in all models. This study indicates the necessity to further study the variability of water isotopes in the snow cover to increase prediction for isotopic composition of snowmelt and hence increase model performance of residence time models in alpine areas and to better understand the accumulation processes and the sources of water in the snow cover of high mountains.

  3. 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

  4. A cluster-optimizing regression-based approach for precipitation spatial downscaling in mountainous terrain

    NASA Astrophysics Data System (ADS)

    Guan, Huade; Wilson, John L.; Xie, Hongjie

    2009-09-01

    SummaryPrecipitation temporal and spatial variability often controls terrestrial hydrological processes and states. Common remote-sensing and modeling precipitation products have a spatial resolution that is often too coarse to reveal hydrologically important spatial variability. A statistical algorithm was developed for downscaling low-resolution spatial precipitation fields. This algorithm auto-searches precipitation spatial structures (rain-pixel clusters), and orographic effects on precipitation distribution without prior knowledge of atmospheric setting. It is composed of three components: rain-pixel clustering, multivariate regression, and random cascade. The only required input data for the downscaling algorithm are coarse-pixel precipitation map and a topographic map. The algorithm was demonstrated with 4 km × 4 km Next Generation Radar (NEXRAD) precipitation fields, and tested by downscaling NEXRAD-aggregated 16 km × 16 km precipitation fields to 4 km × 4 km pixel precipitation, which was then compared to the original NEXRAD data. The demonstration and testing were performed at both daily and hourly temporal resolutions for the northern New Mexico mountainous terrain and the central Texas Hill Country. The algorithm downscaled daily precipitation fields are in good agreement with the original 4 km × 4 km NEXRAD precipitation, as measured by precipitation spatial structures and the statistics between the downscaling and the original NEXRAD precipitation maps. For three daily precipitation events, downscaled precipitation map reproduces precipitation variance of the disaggregation field, and with Pearson correlation coefficients between the downscaled map and the NEXRAD map of 0.65, 0.71, and 0.80. The algorithm does not perform as well on downscaling hourly precipitation fields at the examined scale range (from 16 km to 4 km), which underestimates precipitation variance of the disaggregation field. For a scale range from 4 km to 1 km, the algorithm has

  5. 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. PMID:15487778

  6. Modelling stable water isotopes during "high-precipitation" events at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Schlosser, Elisabeth; Masson-Delmotte, Valérie; Risi, Camille; Stenni, Barbara; Valt, Mauro; Powers, Jordan G.; Manning, Kevin W.; Duda, Michael G.; Cagnati, Anselmo

    2014-05-01

    For a correct paleoclimatologic interpretation of stable water isotopes from ice cores both pre- and post-depositional processes and their role for isotope fractionation have to be better understood. Our study focusses on "pre-depositional processes", namely the atmospheric processes that determine moisture transport and precipitation formation. At the deep ice core drilling site "Dome C", East Antarctica, fresh snow samples have been taken since 2006. These samples have been analysed crystallographically, which enables us to clearly distinguish between blowing snow, diamond dust, and "synoptic precipitation". Also the stable oxygen/hydrogen isotope ratios of the snow samples were measured, including measurements of 17-O. This is the first and only multi-year fresh-snow data series from an Antarctic deep drilling site. The Antarctic Mesoscale Prediction System (AMPS) employs Polar WRF for aviation weather forecasts in Antarctica. The data are archived and can be used for scientific purposes. The mesoscale atmospheric model was adapted especially for polar regions. The horizontal resolution for the domain that covers the Antarctic continent is 10 km. It was shown that precipitation at Dome C is temporally dominated by diamond dust. However, comparatively large amounts of precipitation are observed during several "high-precipitation" events per year, caused by synoptic activity in the circumpolar trough and related advection of relatively warm and moist air from lower latitudes to the interior of Antarctica. AMPS archive data are used to investigate the synoptic situations that lead to "high-precipitation" events at Dome C; in particular, possible moisture sources are determined using back-trajectories. With this meteorological information, the isotope ratios are calculated using two different isotope models, the Mixed Cloud Isotope Model, a simple Rayleigh-type model, and the LMDZ-iso (Laboratoire de Météorologie Dynamic Zoom), a General Circulation Model (GCM

  7. 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

  8. 400-year May-August precipitation reconstruction for Southern England using oxygen isotopes in tree rings

    NASA Astrophysics Data System (ADS)

    Rinne, K. T.; Loader, N. J.; Switsur, V. R.; Waterhouse, J. S.

    2013-01-01

    Few long and well-dated summer precipitation reconstructions that extend beyond the longest records of instrumental measurements exist in Europe. Further understanding of the past trends in summer precipitation and the mechanisms driving that variability are necessary to improve the predictions of climate models. Tree rings are unique in their ability to provide high-resolution, absolutely dated climate signals for the study of palaeoclimatology. The physiological processes controlling oxygen isotope composition (δ18O) in wood are reasonably well understood highlighting its potential as a climate proxy in a variety of environments. Significant correlation between wood δ18O and precipitation has been demonstrated worldwide reflecting both direct rainout processes and indirectly evaporative enrichment. We present an annually resolved reconstruction of precipitation based upon oxygen isotope variations in tree ring cellulose covering the most recent ˜400 years for England. The May-August precipitation series, which was formed by combining reconstructed values based on oxygen isotope composition (δ18O) in tree ring cellulose of pedunculate oak (Quercus robur) (1613-1893) and instrumental data (1894-2003), indicates significant decadal and centennial precipitation variability culminating in dry conditions in the early-middle 17th century and the late 20th century. The analysis demonstrated statistically robust May-August precipitation signal in the δ18O values of oak cellulose back to 1697, the first year of the oldest instrumental precipitation series in England.

  9. Combining stable isotope isotope geochemistry and carbonic anhydrase activity to trace vital effect in carbonate precipitation experiments

    NASA Astrophysics Data System (ADS)

    Thaler, C.; Ader, M.; Menez, B.; Guyot, F. J.

    2013-12-01

    Carbonates precipitated by skeleton-forming eukaryotic organisms are often characterized by non-equilibrium isotopic signatures. This specificity is referred to as the "vital effect" and can be used as an isotopic evidence to trace life. Combining stable isotope geochemistry and enzymology (using the enzyme carbonic anhydrase) we aim to demonstrate that prokaryotes are also able to precipitate carbonate with a non-equilibrium d18OCaCO3. Indeed, if in an biomineralization experiment carbonates are precipitated with a vital effect, the addition of carbonic anhydrase should drive the system to isotope equilibrium, And provide a comparison point to estimate the vital effect range. This protocol allowed us to identify a -20‰ vital effect for the d18O of carbonates precipitated by Sporosarcina pasteurii, a bacterial model of carbonatogen metabolisms. This approach is thus a powerfull tool for the understanding of microbe carbonatogen activity and will probably bring new insights into the understanding of bacterial activity in subsurface and during diagenesis.

  10. Can Mg isotopes be used to trace cyanobacteria-mediated magnesium carbonate precipitation in alkaline lakes?

    NASA Astrophysics Data System (ADS)

    Shirokova, L. S.; Mavromatis, V.; Bundeleva, I.; Pokrovsky, O. S.; Bénézeth, P.; Pearce, C.; Gérard, E.; Balor, S.; Oelkers, E. H.

    2011-07-01

    The fractionation of Mg isotopes was determined during the cyanobacterial mediated precipitation of hydrous magnesium carbonate precipitation in both natural environments and in the laboratory. Natural samples were obtained from Lake Salda (SE Turkey), one of the few modern environments on the Earth's surface where hydrous Mg-carbonates are the dominant precipitating minerals. This precipitation was associated with cyanobacterial stromatolites which were abundant in this aquatic ecosystem. Mg isotope analyses were performed on samples of incoming streams, groundwaters, lake waters, stromatolites, and hydromagnesite-rich sediments. Laboratory Mg carbonate precipitation experiments were conducted in the presence of purified Synechococcus sp cyanobacteria that were isolated from the lake water and stromatolites. The hydrous magnesium carbonates nesquehonite (MgCO3·3H2O) and dypingite (Mg5(CO3)4(OH)25(H2O)) were precipitated in these batch reactor experiments from aqueous solutions containing either synthetic NaHCO3/MgCl2 mixtures or natural Lake Salda water, in the presence and absence of live photosynthesizing Synechococcus sp. Bulk precipitation rates were not to affected by the presence of bacteria when air was bubbled through the system. In the stirred non-bubbled reactors, conditions similar to natural settings, bacterial photosynthesis provoked nesquehonite precipitation, whilst no precipitation occurred in bacteria-free systems in the absence of air bubbling, despite the fluids achieving a similar or higher degree of supersaturation. The extent of Mg isotope fractionation (Δ26Mgsolid-solution) between the mineral and solution in the abiotic experiments was found to be identical, within uncertainty, to that measured in cyanobacteria-bearing experiments, and ranges from -1.4 to -0.7 ‰. This similarity refutes the use of Mg isotopes to validate microbial mediated precipitation of hydrous Mg carbonates.

  11. 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

  12. 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.

  13. Self-consistent ion-by-ion growth model for kinetic isotopic fractionation during calcite precipitation

    NASA Astrophysics Data System (ADS)

    Nielsen, Laura C.; DePaolo, Donald J.; De Yoreo, James J.

    2012-06-01

    Microscopic mechanisms operating at the mineral-aqueous interface control rates of growth and dissolution, isotope fractionation and trace element partitioning during crystal growth. Despite the importance of characterizing surface kinetic controls on isotopic partitioning, no self-consistent microscopic theory has yet been presented which can simultaneously model both mineral growth rate and isotopic composition. Using a kinetic theory for AB or di-ionic crystal growth, we derive a model to predict precipitation rate and isotope fractionation as a function of growth solution oversaturation and solution stoichiometry and apply the theory to calcium isotope fractionation during calcite precipitation. Our model assimilates the current understanding of surface controlled isotope fractionation with kinetic theories of ion-by-ion mineral growth to predict isotopic partitioning during the growth of ionic crystals. This approach accounts for the effect of solution composition on microscopic mineral surface structure and composition, providing numerous testable hypotheses for growth of sparingly soluble AB crystals such as calcite, namely: Both oversaturation and solution stoichiometry control growth rate and partitioning of isotopes during precipitation; for growth driven primarily by step propagation, distinct expressions describe dislocation- and 2D nucleation-driven growth rates, while the expression for isotope fractionation is the same for both mechanisms; mineral precipitation occurring via the formation of an amorphous precursor will generate isotope effects that are not compatible with ion-by-ion growth theory and may therefore be excluded from comparison; and, the absolute kinetic limit of isotope fractionation may not be accessible at high oversaturation due to the formation of amorphous precursors. Using calcite as a model system, we derive expressions for growth rate and isotopic fractionation as a function of oversaturation and Ca:CO32- in solution

  14. Spatial and temporal characteristics of stable isotopes in the Tarim River Basin.

    PubMed

    Sun, Congjian; Li, Xingong; Chen, Yaning; Li, Weihong; Stotler, Randy L; Zhang, Yongqing

    2016-06-01

    By using 233 isotope samples, we investigated the spatial and temporal variations of δ(18)O and δ(2)H in precipitation and surface water, and the contribution of different water sources in the rivers within the Tarim River Basin (TRB), which receives snow/glacier meltwater, groundwater, and rainfall. Our study revealed a similar seasonal pattern of precipitation δ(18)O and δ(2)H at both the north and south edges of the basin, indicating the dominant effect of westerly air masses in the summer and the combined influence of westerly and polar air masses during the winter, although the southern part showed more complex precipitation processes in the summer. River water in the basin has relatively large temporal variations in both δ(18)O and δ(2)H showing a distinct seasonal pattern with lower isotope values in May than in September. Higher d-excess values throughout the year in the Aksu river and the Tizinafu river suggest that water may be intensively recycled in the mountains of the TRB. Based on isotopic hydrograph separation, we found that groundwater is the main water source that discharges the entire basin although individual rivers vary. PMID:26862902

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

    NASA Astrophysics Data System (ADS)

    Schlosser, Elisabeth; Dittmann, Anna; Stenni, Barbara; Masson-Delmotte, Valerie; Powers, Jordan G.; Manning, Kevin W.; Raphael, Marilyn; Fujita, Koji; Werner, Martin; Valt, Mauro; Cagnati, Anselmo

    2016-04-01

    Dome Fuji and Dome C, both deep ice-core drilling sites in East Antarctica, are the only stations, for which direct daily precipitation measurements and stable isotope ratios of the precipitation samples are available. Whereas the Dome F series encompasses only one year of measurements, the Dome C series has been started in 2006 and is ongoing. For Dome C, the type of precipitation (diamond dust, hoar frost, snowfall) was determined based on crystal type analysis. The weather situations causing precipitation at the stations were analysed using data from the Antarctic Mesoscale Prediction System (AMPS). At both sites, major snowfall events were always related to an amplification of Rossby waves in the circumpolar westerlies, which led to an increased meridional transport of moisture and energy. Furthermore, increased amounts of diamond dust were observed after such event-type precipitation. The stable isotope data of the precipitation samples were related to the different weather situations and precipitation types and also simulated using a simple Rayleigh-type model (MCIM) and compared to output from the global isotopic-enhanced model ECHAM5wiso. Possible moisture sources were estimated using the synoptic analysis combined with back-trajectory calculation. MCIM was better in reproducing the annual cycle of deuterium excess, whereas ECHAM5wiso generally showed a smaller bias of the isotope ratios. Hoar frost shows isotope signals very different from diamond dust and snowfall, which hints at a more local cycle of sublimation and deposition for this type of precipitation, whereas both snowfall and diamond dust are related to large-scale moisture transport. Contrary to the literature, a more northern moisture source was found to be not necessarily associated with more depleted snowfall. This is explained by the strong warm air advection accompanying snowfall events, which decreases the temperature difference between source area and deposition site and thus leads to

  16. 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

  17. 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.

  18. Spatial Downscaling of TRMM Precipitation using MODIS product in the Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Cho, H.; Choi, M.

    2013-12-01

    Precipitation is a major driving force in the water cycle. But, it is difficult to provide spatially distributed precipitation data from isolated individual in situ. The Tropical Rainfall Monitoring Mission (TRMM) satellite can provide precipitation data with relatively coarse spatial resolution (0.25° scale) at daily basis. In order to overcome the coarse spatial resolution of TRMM precipitation products, we conducted a downscaling technique using a scaling parameter from the Moderate Resolution Imaging Spectroradiometers (MODIS) sensor. In this study, statistical relations between precipitation estimates derived from the TRMM satellite and the normalized difference vegetation index (NDVI) which is obtained from the MODIS sensor in TERRA satellite are found for different spatial scales on the Korean peninsula in northeast Asia. We obtain the downscaled precipitation mapping by regression equation between yearly TRMM precipitations values and annual average NDVI aggregating 1km to 25 degree. The downscaled precipitation is validated using time series of the ground measurements precipitation dataset provided by Korea Meteorological Organization (KMO) from 2002 to 2005. To improve the spatial downscaling of precipitation, we will conduct a study about correlation between precipitation and land surface temperature, perceptible water and other hydrological parameters.

  19. Influence of regional precipitation patterns on stable isotopes in ice cores from the central Himalayas

    NASA Astrophysics Data System (ADS)

    Pang, H.; Hou, S.; Kaspari, S.; Mayewski, P. A.

    2014-02-01

    Several ice cores have been recovered from the Dasuopu (DSP) Glacier and the East Rongbuk (ER) Glacier in the central Himalayas since the 1990s. Although the distance between the DSP and the ER ice core drilling sites is only ~ 125 km, the stable isotopic record (δ18O or δD) of the DSP core is interpreted in previous studies as a temperature proxy, while the ER core is interpreted as a precipitation proxy. Thus, the climatological significance of the stable isotopic records of these Himalayan ice cores remains a subject of debate. Based on analysis of regional precipitation patterns over the region, we find that remarkable discrepancy in precipitation seasonality between the two sites may account for their disparate isotopic interpretations. At the ER core site, the Indian summer monsoon (ISM) precipitation is dominating due to topographic blocking of the moisture from westerlies by the high ridges of Mt. Qomolangma (Everest), which results in a negative correlation between the ER Δ18O or δD record and precipitation amount along the southern slope of the central Himalayas in response to the "amount effect". At the DSP core site, in comparison with the ISM precipitation, the wintertime precipitation associated with the westerlies is likely more important owing to its local favorable topographic conditions for interacting with the western disturbances. Therefore, the DSP stable isotopic record may be primarily controlled by the westerlies. Our results have important implications for interpreting the stable isotopic ice core records recovered from different climatological regimes of the Himalayas.

  20. Kinetic isotope effect in CO2 degassing: Insight from clumped and oxygen isotopes in laboratory precipitation experiments

    NASA Astrophysics Data System (ADS)

    Affek, Hagit P.; Zaarur, Shikma

    2014-10-01

    Laboratory precipitation experiments provide the basis for the common calibration of both the oxygen isotope and the clumped isotope thermometers. These focus on CaCO3 crystals that form deep in the bulk of the solution, often by the bubbling of N2(g) through a saturated Ca(HCO3)2 solution, following the classic experiments on McCrea (1950). Here we examine oxygen and clumped isotopes in CaCO3 that was precipitated at the surface of a solution that undergoes passive CO2 degassing. This CaCO3 is affected by enhanced disequilibrium that is associated with degassing, and has therefore higher δ18O and lower Δ47 values than those of the accepted thermometer calibrations. These offsets from the common thermometers calibrations increase with decreasing temperature for Δ47 but decrease with decreasing temperature for δ18O. The Δ47-δ18O co-variance is therefore strongly temperature dependent, in contrast to theoretical predictions. This suggests an influence of additional fractionation in fast growing minerals, between DIC and calcite, that affects δ18O and counteracts some of the degassing related enrichment. This effect seems not to influence Δ47. The physical setup of CaCO3 minerals growing at the solution surface is analogous to the degassing and precipitation processes that occur in stalagmites, such that these laboratory experiments may help shed light on the isotopic disequilibrium that is observed in speleothems.

  1. [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. PMID:20030129

  2. 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.

  3. 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.

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

    PubMed

    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

  5. 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

  6. Understanding climatic controls on Svalbard water vapour and precipitation isotopic composition

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, Valérie; Steen-Larsen, Hans-Christian; Zanetti, Nathalie; Cattani, Olivier; Maturilli, Marion; Debatin, Siegrid; Terzer, Stefan; Bonne, Jean-Louis; Schneider, Matthias

    2015-04-01

    We investigate the meteorological and climatic controls on the isotopic composition of vapour and precipitation at Ny Alesund, Svalbard. This is based on the IAEA database of monthly precipitation isotopic composition data spanning 1993-2012 as well as new measurements performed using a PICARRO CRDS analyzer deployed since June 2014 at Ny Alesund. The precipitation data depict a strong decoupling between oxygen 18 and temperature at the seasonal scale and for monthly anomalies. While a relationship is observed between winter precipitation isotopic composition and temperature, this disappears during summer, at the inter-annual scale. Moreover, the deuterium versus oxygen 18 relationship depicts different meteoric water lines in winter and summer, consistent with the strong seasonal cycle of deuterium excess, and indicating shifts in moisture origin. The continuous water vapour data (investigated from July to December 2014 so far) show in contrast a tight relationship between hourly oxygen 18 data and surface temperature and humidity, as well as strong antiphase between deuterium excess and oxygen 18. No significant diurnal variability is observed. We show how precipitation intermittency strongly alters the sampling provided by precipitation data and distorts the relationship with local temperature. The surface vapour deuterium data are compared with FTIR retrievals. The importance of changes in air mass origins is also assessed by comparison with moisture backtrajectories.

  7. 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

  8. STABLE SULFUR ISOTOPES OF SULFATE IN PRECIPITATION AND STREAM SOLUTIONS IN A NORTHERN HARDWOODS WATERSHED

    EPA Science Inventory

    table 5 isotopes of 5042 in precipitation and stream solutions in a northern hardwoods watershed (Bear Brooks Watershed, Maine) were examined to determine sources of stream S042- and to identify watershed processes that may affect atmospherically deposited S042 prior to reaching ...

  9. 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.

  10. 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

  11. Estimation of Missing Precipitation Data using Soft Computing based Spatial Interpolation Techniques

    NASA Astrophysics Data System (ADS)

    Teegavarapu, R. S.

    2007-12-01

    Deterministic and stochastic weighting methods are the most frequently used methods for estimating missing rainfall values at a gage based on values recorded at all other available recording gages. Traditional spatial interpolation techniques can be integrated with soft computing techniques to improve the estimation of missing precipitation data. Association rule mining based spatial interpolation approach, universal function approximation based kriging, optimal function approximation and clustering methods are developed and investigated in the current study to estimate missing precipitation values at a gaging station. Historical daily precipitation data obtained from 15 rain gauging stations from a temperate climatic region, Kentucky, USA, are used to test this approach and derive conclusions about efficacy of these methods in estimating missing precipitation data. Results suggest that the use of soft computing techniques in conjunction with a spatial interpolation technique can improve the precipitation estimates and help to address few limitations of traditional spatial interpolation techniques.

  12. Coupled isotopes of plant wax and hemicellulose markers record information on relative humidity and isotopic composition of precipitation

    NASA Astrophysics Data System (ADS)

    Tuthorn, M.; Zech, R.; Ruppenthal, M.; Oelmann, Y.; Kahmen, A.; del Valle, H. F.; Eglinton, T.; Zech, M.

    2015-02-01

    The δ2H isotopic composition of leaf waxes is used increasingly for paleohydrological and -climate reconstructions. However, it is challenging to disentangle past changes in the isotopic composition of precipitation and changes in evapotranspirative enrichment of leaf water. We analyzed δ2H on n-alkanes and fatty acids in topsoils along a climate transect in Argentina, for which we had previously measured δ18O on plant-derived sugars. Our results indicate that leaf wax biomarker δ2H values (δ2Hlipids) primarily reflect δ2Hsource water (precipitation), but are modulated by evapotranspirative enrichment. A mechanistic model is able to produce the main trends in δ2Hlipids along the transect, but seems to slightly underestimate evapotranspirative enrichment in arid regions and overestimate it in grass-dominated ecosystems. Furthermore, the (i) coupling of the δ2Hlipid and δ18Osugar biomarker results and (ii) application of biosynthetic fractionation factors allows calculating the δ2H-δ18O isotopic composition of leaf water along the transect. This also yields the deuterium excess (d excess) of leaf water, which mainly reflects evapotranspirative enrichment, and can be used to model relative air humidity (RH). The high correlation of modeled (reconstructed based on biomarker results) and measured RH, as well as the good agreement between modeled and actual δ2H and δ18O of precipitation along the transect lends support to the coupled δ2Hlipid and δ18Osugar biomarker approach for future paleoclimate research.

  13. 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.

  14. 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.

  15. Silicon isotope fractionation during abiotic silica precipitation at low temperatures: Inferences from flow-through experiments

    NASA Astrophysics Data System (ADS)

    Geilert, Sonja; Vroon, Pieter Z.; Roerdink, Desiree L.; Van Cappellen, Philippe; van Bergen, Manfred J.

    2014-10-01

    Silicon isotopes have considerable potential as proxy for (near-) surface processes and environmental conditions. However, unambiguous interpretations of isotope signatures in natural silica deposits are often hampered by a lack of independent quantitative information on isotopic fractionations operating under the environmental conditions of interest. We performed seeded silica precipitation experiments using flow-through reactors in the 10-60 °C temperature range to alleviate this problem. The principal objective was to quantify the silicon isotope fractionations during controlled precipitation of amorphous silica from a flowing aqueous solution. The experiments were designed to simulate silica deposition induced by a temperature drop, with particular relevance for (near-) surface hydrothermal systems associated with steep temperature gradients. Monitored differences in silicon isotope ratios (30Si/28Si and 29Si/28Si) between input and output solutions demonstrated a systematic sequence in behavior. During an initial time interval, that is, before the reaction system reached steady state, the observed isotope shifts were influenced by dissolution of the seed material, the saturation state of the solution and the specific surface area of the seeds. After reaching steady state, the selective incorporation of silicon isotopes by the solid phase exhibited an explicit temperature dependency: the lighter isotopes were preferentially incorporated, and apparent fractionation magnitudes increased with decreasing temperature. Calculated magnitudes of silicon isotope fractionations between precipitated and dissolved silica (Δ30Si = δ30Siprecipitate (calculated) - δ30Siinput solution) were -2.1‰ at 10 °C, -1.2‰ at 20 °C, -1.0‰ at 30 °C, -0.5‰ at 40 °C, 0.1‰ at 50 °C, and 0.2‰ at 60 °C (s.d. ⩽ 0.6‰, based on replicate experiments). Hence, fractionation was nearly insignificant at temperatures ⩾50 °C. Apart from this relationship with temperature

  16. Source and Seasonality Effects on Precipitation Isotope Values in the Gulf of Alaska

    NASA Astrophysics Data System (ADS)

    Bailey, H. L.; Welker, J. M.; Klein, E. S.; Rogers, M. C.

    2015-12-01

    A number of paleoisotope records from the Gulf of Alaska region attribute long-term shifts in δ18O and δ2H to changes in moisture source and air mass trajectory. However, the inability to fully quantify the modern relationship between proxy and climate has been problematic due to the paucity of modern precipitation isotopedata in this region. To provide these data, event-based sampling was used between 2005-2014 at Tideview sampling station in Anchorage, Alaska. Precipitation samples were analyzed for stable isotope ratios (δ18O, δ2H, d-excess) and examined in context of climate variables including temperature, air mass source and trajectory, precipitation amount, and relative humidity. Local surface air temperature explains a relatively small (< 30%) proportion of isotope variability, suggesting that paleoisotope archives related to precipitation might not be useful for quantitative temperature reconstructions in this area. Instead, results from a Hybrid Single-Particle Lagrangian Integrated Trajectory Model demonstrate that air mass source and trajectory has the greatest influence on the isotopic composition of precipitation at our site. Specifically, lower (higher) δ18O (d-excess) values are associated with Arctic sourced moisture from the north, while Pacific marine sourced moisture from the south is characterized by the reverse (higher δ18O, lower d-excess).These findings have important implications for local and regional paleoisotope reconstructions which are often interpreted in terms of moisture source and trajectory variations, and which currently rely on a sparse network of isotope measurement sites from across NW North America. Furthermore, these new data highlight the relative importance of regional atmospheric circulation patterns and climate indices (e.g. the North Pacific Index and Pacific Decadal Oscillation) for determining the source, transport, and rain-out history of precipitating moisture in the Gulf of Alaska region.

  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. 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.

  19. Do stable oxygen isotope series from Pinus sylvestris growing in Scotland retain information on precipitation dynamics?

    NASA Astrophysics Data System (ADS)

    Woodley, Ewan; Loader, Neil; McCarroll, Danny; Robertson, Iain; Heaton, Timothy

    2010-05-01

    In order to better constrain climate predictions it is essential to reduce error in climate reconstructions and understand how climate behaves at different temporal frequencies. Few high-resolution climate reconstructions exist for Britain, despite the strong influence of the North Atlantic on this temperate maritime zone. Annually-resolved stable oxygen isotope series from Pinus sylvestris L. growing at Southern Glens (western Highlands of Scotland) may provide information on precipitation dynamics in northern Britain. A significant correlation (r = 0.68; P< 0.01) exists between δ18O cellulose (Southern Glens) and mean June-July δ18O precipitation (Global Network of Isotopes in Precipitation GNIP) from Wallingford, Oxfordshire (AD 1982-2003). Whilst acknowledging the limited length of the GNIP dataset, the strength of the correlation suggests that between AD 1982 and 2003 both Southern Glens and Wallingford were subjected to the same June-July low pressure systems (depressions) as they passed over Britain from west to east. These data indicate that despite evaporative enrichment in the leaf, a significant proportion of variance in δ18O precipitation (R2 = 0.45) may be retained in the cellulose of Pinus sylvestris growing at Southern Glens. Such a relationship demonstrates the potential for reconstructing the δ18O of precipitation at this site, possibly providing information on past variability in air mass dominance and precipitation dynamics in the region.

  20. [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

  1. Quantifying Surface Kinetic Fractionations for Isotopes and Trace Elements in Calcite Precipitated from Aqueous Solution

    NASA Astrophysics Data System (ADS)

    DePaolo, D. J.; Nielsen, L. C.; Hofmann, A. E.; DeYoreo, J.; Gagnon, A. C.; Watkins, J. M.; Ryerson, F. J.; Brown, S. T.

    2011-12-01

    The isotopic ratios and trace element concentrations in calcite and other carbonate minerals form the basis for several paleoenvironmental indicators that are relied upon to reconstruct past Earth climates and ocean processes. Most of these carbonate minerals form at low temperatures (0 to 30C) and consequently are unlikely to have precipitated from aqueous solutions at equilibrium. The non-equilibrium nature of the precipitation process is well illustrated by the experimentally demonstrated precipitation rate-dependence of parameters such as the Ca and O isotopic composition, and the Sr, Mg, and Mn concentrations of calcite. We have been focused on understanding how to predict the magnitude and controls on these kinetic effects using a general transition-state theory approach, as well as models of ion-by-ion growth, molecular dynamics simulations of the desolvation step required for addition of cations to a mineral surface, and further experiments that involve carefully controlled solution compositions and crystal growth rates. Although models have been proposed that invoke diffusion as the primary control on the non-equilibrium aspects of calcite precipitation, it is relatively easy to show that diffusion is not likely to be the primary controlling process. We have focused on understanding the kinetic effects operating at and near the mineral surface, which are undeniably present and important, and appear to be of the correct magnitude and direction to account for observations in both laboratory and natural calcites. The approach we are using is also applicable to higher temperature aqueous precipitation. There are indications from Ca isotopes that similar surface kinetic effects occur at temperatures of 300 to 400C. Kinetic isotope and trace element effects are critically dependent on molecular exchange rates between the mineral surface and the aqueous solution, and the ratio of these rates to the net crystal growth rate. The challenge is to predict and

  2. Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria

    NASA Astrophysics Data System (ADS)

    Mavromatis, Vasileios; Pearce, Christopher R.; Shirokova, Liudmila S.; Bundeleva, Irina A.; Pokrovsky, Oleg S.; Benezeth, Pascale; Oelkers, Eric H.

    2012-01-01

    The hydrous magnesium carbonates, nesquehonite (MgCO 3·3H 2O) and dypingite (Mg 5(CO 3) 4(OH) 2·5(H 2O)), were precipitated at 25 °C in batch reactors from aqueous solutions containing 0.05 M NaHCO 3 and 0.025 M MgCl 2 and in the presence and absence of live photosynthesizing Gloeocapsa sp. cyanobacteria. Experiments were performed under a variety of conditions; the reactive fluid/bacteria/mineral suspensions were continuously stirred, and/or air bubbled in most experiments, and exposed to various durations of light exposure. Bulk precipitation rates are not affected by the presence of bacteria although the solution pH and the degree of fluid supersaturation with respect to magnesium carbonates increase due to photosynthesis. Lighter Mg isotopes are preferentially incorporated into the precipitated solids in all experiments. Mg isotope fractionation between the mineral and fluid in the abiotic experiments is identical, within uncertainty, to that measured in cyanobacteria-bearing experiments; measured δ 26Mg ranges from -1.54‰ to -1.16‰ in all experiments. Mg isotope fractionation is also found to be independent of reactive solution pH and Mg, CO 32-, and biomass concentrations. Taken together, these observations suggest that Gloeocapsa sp. cyanobacterium does not appreciably affect magnesium isotope fractionation between aqueous fluid and hydrous magnesium carbonates.

  3. 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

  4. 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.

  5. SPATIAL ALLOCATION FACTOR PROCEDURES FOR THE 1980 NAPAP (NATIONAL ACID PRECIPITATION ASSESSMENT PROGRAM) EMISSIONS INVENTORY DOCUMENTATION

    EPA Science Inventory

    The report documents the development of spatial allocation factors to apportion National Acid Precipitation Assessment Program (NAPAP) area source emissions from counties to individual grid cells for input to the Regional Acid Deposition Models (RADM) and Regional Oxidant Models ...

  6. COMPARISON OF GEOSTATISTICAL PROCEDURES FOR SPATIAL ANALYSIS OF PRECIPITATION IN MOUTAINOUS TERRAIN

    EPA Science Inventory

    Application of simulation models to assessment of global climate change effects often requires spatially distributed estimates of precipitation, both under current and future climate scenarios. imple interpolation methods fail to consider the effects of topography on precipitatio...

  7. 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. PMID:25761056

  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. 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

  10. 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

  11. 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

  12. 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. ;

  13. 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

  14. Spatial interpolation of daily precipitation in China: 1951-2005

    NASA Astrophysics Data System (ADS)

    Chen, Deliang; Ou, Tinghai; Gong, Lebing; Xu, Chong-Yu; Li, Weijing; Ho, Chang-Hoi; Qian, Weihong

    2010-11-01

    Climate research relies heavily on good quality instrumental data; for modeling efforts gridded data are needed. So far, relatively little effort has been made to create gridded climate data for China. This is especially true for high-resolution daily data. This work, focuses on identifying an accurate method to produce gridded daily precipitation in China based on the observed data at 753 stations for the period 1951-2005. Five interpolation methods, including ordinary nearest neighbor, local polynomial, radial basis function, inverse distance weighting, and ordinary kriging, have been used and compared. Cross-validation shows that the ordinary kriging based on seasonal semi-variograms gives the best performance, closely followed by the inverse distance weighting with a power of 2. Finally the ordinary kriging is chosen to interpolate the station data to a 18 km× 18 km grid system covering the whole country. Precipitation for each 0.5° × 0.5° latitude-longitude block is then obtained by averaging the values at the grid nodes within the block. Owing to the higher station density in the eastern part of the country, the interpolation errors are much smaller than those in the west (west of 100°E). Excluding 145 stations in the western region, the daily, monthly, and annual relative mean absolute errors of the interpolation for the remaining 608 stations are 74%, 29%, and 16%, respectively. The interpolated daily precipitation has been made available on the internet for the scientific community.

  15. 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

  16. Stable Isotope Reveal Sources of Precipitation in the Qinghai Lake Basin of the Northeastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Cui, B.; Li, X.

    2014-12-01

    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 δ2H = 7.86 δ18O + 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 δ18O and δ2H 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 δ18O 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. Our findings demonstrate that the contribution of evaporation from lakes to atmospheric vapor is fundamental to water cycling on the TP.

  17. 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.

  18. Understanding key drivers controlling daily stable isotope variations in precipitation of Costa Rica, Central America

    NASA Astrophysics Data System (ADS)

    Sanchez-Murillo, Ricardo; Welsh, Kristin; Birkel, Christian; Esquivel-Hernández, Germain; Corrales-Salazar, Jose; Boll, Jan; Brooks, Erin; Roupsard, Olivier; Katchan, Irina; Arce-Mesén, Rafael; Soulsby, Chris; Araguás-Araguás, Luis

    2015-04-01

    Costa Rica is located on the Central American Isthmus, which receives direct moisture inputs from the Caribbean Sea and the Pacific Ocean. The relatively narrow, but high relief Central American land bridge is characterized by unique mountainous and lowland microclimates. However, only limited knowledge exists about the impact of relief and regional atmospheric circulation patterns on precipitation origin, transport, and isotopic composition in this tropical region. Therefore, the main scope of this study is to identify the key drivers controlling variations in meteoric waters of Costa Rica using stable isotopes based on daily sample collection for the year 2013. 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‰ d18O up to -0.9‰ d18O. By mid-May, the Intertropical Convergence Zone reaches Costa Rica resulting in a notable depletion in isotope ratios (up to -18.5‰ d18O). HYSPLIT back air mass trajectories indicate the strong influence on the origin and transport of precipitation of two main moisture transport mechanisms, the Caribbean Low Level Jet and the Colombian Low Level Jet as well as 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 enhance catchment and groundwater modeling efforts in ungauged basins where scarcity of long-term monitoring data drastically limit current and future water resources management.

  19. 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.

    2015-12-01

    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.

  20. 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

  1. Spatial disaggregation of bias-corrected GCM precipitation for improved hydrologic simulation: Ping River Basin, Thailand

    NASA Astrophysics Data System (ADS)

    Sharma, D.; Das Gupta, A.; Babel, M. S.

    2007-01-01

    Global Climate Models (GCMs) precipitation scenarios are often characterized by biases and coarse resolution that limit their direct application for basin level hydrological modeling. Bias-correction and spatial disaggregation methods are employed to improve the quality of ECHAM4/OPYC SRES A2 and B2 precipitation for the Ping River Basin in Thailand. Bias-correction method, based on gamma-gamma transformation, is applied to improve the frequency and amount of raw GCM precipitation at the grid nodes. Spatial disaggregation model parameters (β,σ2), based on multiplicative random cascade theory, are estimated using Mandelbrot-Kahane-Peyriere (MKP) function at q=1 for each month. Bias-correction method exhibits ability of reducing biases from the frequency and amount when compared with the computed frequency and amount at grid nodes based on spatially interpolated observed rainfall data. Spatial disaggregation model satisfactorily reproduces the observed trend and variation of average rainfall amount except during heavy rainfall events with certain degree of spatial and temporal variations. Finally, the hydrologic model, HEC-HMS, is applied to simulate the observed runoff for upper Ping River Basin based on the modified GCM precipitation scenarios and the raw GCM precipitation. Precipitation scenario developed with bias-correction and disaggregation provides an improved reproduction of basin level runoff observations.

  2. Spatial disaggregation of bias-corrected GCM precipitation for improved hydrologic simulation: Ping River Basin, Thailand

    NASA Astrophysics Data System (ADS)

    Sharma, D.; Das Gupta, A.; Babel, M. S.

    2007-06-01

    Global Climate Models (GCMs) precipitation scenarios are often characterized by biases and coarse resolution that limit their direct application for basin level hydrological modeling. Bias-correction and spatial disaggregation methods are employed to improve the quality of ECHAM4/OPYC SRES A2 and B2 precipitation for the Ping River Basin in Thailand. Bias-correction method, based on gamma-gamma transformation, is applied to improve the frequency and amount of raw GCM precipitation at the grid nodes. Spatial disaggregation model parameters (β,σ2), based on multiplicative random cascade theory, are estimated using Mandelbrot-Kahane-Peyriere (MKP) function at q=1 for each month. Bias-correction method exhibits ability of reducing biases from the frequency and amount when compared with the computed frequency and amount at grid nodes based on spatially interpolated observed rainfall data. Spatial disaggregation model satisfactorily reproduces the observed trend and variation of average rainfall amount except during heavy rainfall events with certain degree of spatial and temporal variations. Finally, the hydrologic model, HEC-HMS, is applied to simulate the observed runoff for upper Ping River Basin based on the modified GCM precipitation scenarios and the raw GCM precipitation. Precipitation scenario developed with bias-correction and disaggregation provides an improved reproduction of basin level runoff observations.

  3. 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.

  4. Impact of Spatial Interpolation Methods for Precipitation on Ensemble Streamflow Simulation From Watershed Models

    NASA Astrophysics Data System (ADS)

    Hwang, Y.; Clark, M. P.; Rajagopalan, B.

    2005-05-01

    Watershed models are used for simulating basin streamflows based on spatially sparse precipitation and temperature observations. The sparse observations are typically interpolated on a regular grid or a subbasin as inputs to the hydrologic models. Given the paucity in observations and nonhomogenous nature of the precipitation process, differences in interpolation methods can potentially impact the simulated streamflow. Of course, hydrologic model parameter uncertainty also contribute to the errors, but in this paper we focus on the uncertainty due to interpolation methods. To this end, first we developed a two-step process in which the precipitation occurrence is first generated via a logistic regression model, and the amounts are then estimated using a Multiple Linear Regression (MLR) and Locally Weighted Polynomial Regression (LWP). The two-step approach is shown to capture the spatial variability of precipitation effectively than other competing traditional methods. Secondly, interpolated precipitation estimates are input into the watershed model, Precipitation Runoff Modeling System (PRMS) to estimate daily and consequently, monthly and seasonal streamflows. Streamflow estimates from PRMS are obtained for three methods of precipitation interpolation, MLR, LWP and the currently used method in PRMS, Climatological MLR (CMLR). Streamflows are compared on a variety of attributes. We find that the MLR and LWP methods perform much better in simulating the streamflows compared to CMLR. Ensembles of precipitation from the two methods (MLR and LWP) coupled with the logistic regression for precipitation occurrence, are generated to subsequently generate ensembles of streamflows from the watershed model. This approach captures the input uncertainty.

  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. 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

  7. 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.

  8. Oxygen isotope values of precipitation and surface waters in northern Central America (Belize and Guatemala) are dominated by temperature and amount effects

    NASA Astrophysics Data System (ADS)

    Lachniet, Matthew S.; Patterson, William P.

    2009-07-01

    An understanding of the climatic controls on precipitation δ18O is required to interpret isotopic records of paleoclimate and paleoaltimetry. However, variations in precipitation δ18O in time and space are only poorly known in northern Central America. To test the hypothesis that precipitation and surface water δ18O values are dominated by temporal and spatial amount effects, we analyzed δ18O in surface waters collected from Guatemala and Belize, and in precipitation from the Global Network for Isotopes in Precipitation database for Veracruz, Mexico, and San Salvador, El Salvador. Herein we show that the dominant controls on δ18O values of precipitation and surface waters are fairly simple. Temporally, the dominant control on precipitation δ18O values is the amount effect, whereby there is an inverse correlation between rainfall amount and δ18O. Precipitation δ18O values decrease by 1.24‰ per 100 mm increase of monthly rainfall. Spatially, only two variables - distance from the coast and mean catchment altitude - explain 84% of the surface water δ18O variability. Surface water δ18O values show an altitude effect of - 1.9 to - 2.4‰ km - 1 and a continental effect of 0.69‰ per 100 km once corrected for altitude effects. A decrease in surface water δ18O by 3 to 4‰ from the Caribbean Sea to the Pacific Ocean is evident as an isotopic rain shadow on the Pacific slope. Our data also show that river waters in this humid tropical environment are good proxies for δ18O values of precipitation in northern Central America. The Guatemala/Belize surface water line is defined as δD = 8.0 × δ18O + 8.7, which is similar to the meteoric water line at San Salvador of δD = 8.1 × δ18O + 10.9. Spatial variability in δ18O values is interpreted to reflect 1) progressive rainout of Caribbean-sourced air masses upon traverse of Central America, and 2) the temperature-dependent equilibrium fractionation between vapor and condensate related to the altitude effect

  9. 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.

  10. Stable isotopes in water vapor and precipitation for a coastal lagoon at mid latitudes

    NASA Astrophysics Data System (ADS)

    Zannoni, Daniele; Bergamasco, Andrea; Dreossi, Giuliano; Rampazzo, Giancarlo; Stenni, Barbara

    2016-04-01

    The stable oxygen and hydrogen isotope composition in precipitation can be used in hydrology to describe the signature of local meteoric water. The isotopic composition of water vapor is usually obtained indirectly from measurements of δD and δ18O in precipitation, assuming the isotopic equilibrium between rain and water vapor. Only few studies report isotopic data in both phases for the same area, thus providing a complete Local Meteoric Water Line (LMWL). The goal of this study is to build a complete LMWL for the lagoon of Venice (northern Italy) with observations of both water vapor and precipitation. The sampling campaign has started in March 2015 and will be carried out until the end of 2016. Water vapor is collected once a week with cold traps at low temperatures (‑77°C). Precipitation is collected on event and monthly basis with a custom automatic rain sampler and a rain gauge, respectively. Liquid samples are analyzed with a Picarro L1102-i and results are reported vs VSMOW. The main meteorological parameters are continuously recorded in the same area by the campus automatic weather station. Preliminary data show an LMWL close to the Global Meteoric Water Line (GMWL) with lower slope and intercept. An evaporation line is clearly recognizable, considering samples that evaporated between the cloud base and the ground. The deviation from the GMWL parameters, especially intercept, can be attributed to evaporated rain or to the humidity conditions of the water vapor source. Water vapor collected during rainfall shows that rain and vapor are near the isotopic equilibrium, just considering air temperature measured at ground level. Temperature is one of the main factor that controls the isotopic composition of the atmospheric water vapor. Nevertheless, the circulation of air masses is a crucial parameter which has to be considered. Water vapor samples collected in different days but with the same meteorological conditions (air temperature and relative humidity

  11. Precipitation extremes in the Yangtze River Basin, China: regional frequency and spatial-temporal patterns

    NASA Astrophysics Data System (ADS)

    Chen, Yongqin David; Zhang, Qiang; Xiao, Mingzhong; Singh, Vijay P.; Leung, Yee; Jiang, Luguang

    2014-05-01

    Regional frequency analysis and spatial-temporal patterns of precipitation extremes are investigated based on daily precipitation data covering 1960-2009 using the index-flood L-moments method together with some advanced statistical tests and spatial analysis techniques. The results indicate that: (1) the entire Yangtze River basin can be divided into six homogeneous regions in terms of extreme daily precipitation index. Goodness-of-fit test indicates that Pearson type III (PE3, three parameters), general extreme-value (GEV, three parameters), and general normal (GNO, three parameters) perform well in fitting regional precipitation extremes; (2) the regional growth curves for each homogeneous region with 99 % error bands show that the quantile estimates are reliable enough and can be used when return periods are less than 100 years, and the results indicate that extreme precipitation events are highly probable to occur in regions V and VI, and hence higher risk of floods and droughts; and (3) spatial patterns of annual extreme daily precipitation with return period of 20 years indicate that precipitation amount increases gradually from the upper to the lower Yangtze River basin, showing higher risks of floods and droughts in the middle and lower Yangtze River basin, and this result is in good agreement with those derived from regional growth curves.

  12. 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.

  13. 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

  14. 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

  15. Integration of Spatial Interpolation Techniques and Association Rules for Estimation of Missing Precipitation Data

    NASA Astrophysics Data System (ADS)

    Teegavarapu, R. S.

    2006-12-01

    Deterministic and stochastic weighting methods are the most frequently used methods for estimating missing rainfall values at a gage based on values recorded at all other available recording gages. These methods may not always provide accurate estimates due to spatial and temporal variability of rainfall available at point measurements in space and also due to limitations of spatial interpolation techniques. Since an interpolated value of a variable at a point in space depends on observed values at all other points in space, temporal associations among observations in space can be beneficial in interpolation. An association rule mining (ARM) based spatial interpolation approach is proposed and investigated in the current study to estimate missing precipitation values at a gaging station. A stochastic spatial interpolation technique and three deterministic weighting methods are used in the current study. Historical daily precipitation data obtained from 15 rain gauging stations from temperate climatic region, Kentucky, USA, are used to test this approach and derive conclusions about its efficacy for estimating missing precipitation data. Results suggest that the use of association rule mining in conjunction with any spatial interpolation technique can improve the precipitation estimates and help to address one of the major limitations of any spatial interpolation technique.

  16. Isotope evidence for secondary sulfide precipitation along the Marsyandi River, Nepal, Himalayas

    NASA Astrophysics Data System (ADS)

    Turchyn, Alexandra V.; Tipper, Edward T.; Galy, Albert; Lo, Jun-Kai; Bickle, Mike J.

    2013-07-01

    We present sulfur and oxygen isotope data from 41 samples of dissolved riverine sulfate from along 65 km of the Marsyandi River in the Northern Himalayas. Coupled sulfur and oxygen isotopic composition of riverine sulfate (δ34S and δ18O respectively) yield unique constraints on the source of sulfur to the river system. The headwaters of the Marsyandi River have light δ34S and δ18O, which requires that the source of sulfate to the river is through the anoxic weathering of pyrite (likely via Fe3+). The δ34S and δ18O of sulfate in tributaries to the Marsyandi increase downstream, which could result either from inputs from evaporites or bacterial sulfate reduction with subsequent sulfide precipitation in warmer and wetter catchments; either of these processes could result in heavy δ34S and δ18O of the residual river sulfate. Elemental ratios such as Sr/Ca and Ca/SO4 suggest, as previous studies have also concluded, that evaporite weathering is not important in the Marsyandi River. We conclude that the isotope data is most consistent with the onset of bacterial sulfate reduction and secondary sulfide precipitation in the soils in the warmer and wetter downstream catchments. Our results have implications for understanding the source of sulfate to the ocean as well as the redox and acidity budget within rapidly eroding catchments.

  17. Spatial patterns of Transit-Time Distributions using δ18O-isotope tracer simulations at ungauged river locations

    NASA Astrophysics Data System (ADS)

    Stockinger, Michael; Bogena, Heye; Lücke, Andreas; Diekkrüger, Bernd; Weiler, Markus; Vereecken, Harry

    2013-04-01

    Knowledge of catchment response times to a precipitation forcing and of isotope tracer transit times can be used to characterize a catchment's hydrological behavior. The aim of this study was to use one gauging station together with multiple δ18O-isotope monitoring locations along the main stream to characterize the spatial heterogeneity of a catchment's hydrological behavior in the context of transit times. We present a method suitable for small catchments to estimate the Transit-Time Distribution (TTD) of precipitation to any stream point using δ18O tracer data, no matter if the stream point is gauged or ungauged. Hourly runoff and precipitation data were used to determine the effective precipitation under base flow conditions at Wüstebach (Eifel, Germany), a small, forested TERENO/TR32 test site. Modeling was focused on base flow due to the weekly measurement intervals of δ18O. The modeling period of 2.5 years was split up in six different hydrological seasons, based on average soil water content, in order to ensure a good fit of the model. Due to the small size of the Wüstebach catchment (27 ha) we assumed the derived effective precipitation to be applicable for the whole catchment. For subsequent modeling of stream water δ18O data we used effective precipitation as an input variable and corrected in a two-step process for canopy evaporation and soil evaporation. Thus we derived base flow TTDs for the ungauged stream and tributary locations. Results show a different behavior of the catchment's response time for different catchment wetness conditions with respect to base flow formation. Winter seasons show similar response times, as well as summer seasons, with the exception of one summer with a considerable higher response time. The transit time of water across the isotope observation points shows points more influenced by shallow source waters than other points, where a higher contribution of groundwater is observable.

  18. 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.

  19. Effects of spatial resolution in the simulation of daily and subdaily precipitation in the southwestern US

    NASA Astrophysics Data System (ADS)

    Tripathi, Om P.; Dominguez, Francina

    2013-07-01

    We evaluate the effects of spatial resolution on the ability of a regional climate model to reproduce observed extreme precipitation for a region in the Southwestern United States. A total of 73 National Climate Data Center observational sites spread throughout Arizona and New Mexico are compared with regional climate simulations at the spatial resolutions of 50 km and 10 km for a 31 year period from 1980 to 2010. We analyze mean, 3-hourly and 24-hourly extreme precipitation events using WRF regional model simulations driven by NCEP-2 reanalysis. The mean climatological spatial structure of precipitation in the Southwest is well represented by the 10 km resolution but missing in the coarse (50 km resolution) simulation. However, the fine grid has a larger positive bias in mean summer precipitation than the coarse-resolution grid. The large overestimation in the simulation is in part due to scale-dependent deficiencies in the Kain-Fritsch convective parameterization scheme that generate excessive precipitation and induce a slow eastward propagation of the moist convective summer systems in the high-resolution simulation. Despite this overestimation in the mean, the 10 km simulation captures individual extreme summer precipitation events better than the 50 km simulation. In winter, however, the two simulations appear to perform equally in simulating extremes.

  20. 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.

  1. 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. PMID:26803681

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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. PMID:22882001

  7. Evaluation of spatial and temporal characteristics of precipitation variations in Jilin Province, Northeast China

    NASA Astrophysics Data System (ADS)

    Liu, Bo; Xiao, Changlai; Liang, Xiujuan

    2015-10-01

    Precipitation time series were analysed using the Mann-Kendall (MK) test and wavelet analysis based on the mean seasonal and annual precipitation from 29 meteorological stations in Jilin Province for the period 1958-2011. Both the temporal and spatial distribution characteristics of the seasonal and annual precipitation trends and periodicities in different regions in Jilin Province were studied for the first time in this paper. New findings from the intensive calculations and appropriate analysis of data in longer period are as follows: (i) The annual precipitation of Jilin Province has experienced four states: a decrease (1958-1980), increase (1980-1987), decrease (1987-2003) and increase (2003-2011). (ii) The annual precipitation and seasonal precipitation increased from the northwest and northeast of the study area toward the south. (iii) Almost 90 % of the stations showed negative trends in annual precipitation variations. (iv) The trends in spring and winter are mainly increasing, whereas the trends in summer and autumn are mainly decreasing. (v) Jilin Province can be divided into four parts based on the periodicities of annual precipitation sequences: 5-6, 10-20 and 25-30 years in the northwest; 4-8 and 16-25 years in the centre; 7-8 and 13-17 years in the south and 5-10 and 12-17 years in the southeast.

  8. 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.

  9. 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

  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. 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

  12. 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

    2016-01-01

    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 (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. PMID:26971874

  13. 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.

  14. 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

  15. Modeling the water isotopes in Greenland precipitation 1959-2001 with the meso-scale model REMO-iso

    NASA Astrophysics Data System (ADS)

    Sjolte, J.; Hoffmann, G.; Johnsen, S. J.; Vinther, B. M.; Masson-Delmotte, V.; Sturm, C.

    2011-09-01

    Ice core studies have proved the δ18O in Greenland precipitation to be correlated to the phase of the North Atlantic Oscillation (NAO). This subject has also been investigated in modeling studies. However, these studies have either had severe biases in the δ18O levels, or have not been designed to be compared directly with observations. In this study we nudge a meso-scale climate model fitted with stable water isotope diagnostics (REMO-iso) to follow the actual weather patterns for the period 1959-2001. We evaluate this simulation using meteorological observations from stations along the Greenland coast, and δ18O from several Greenland ice core stacks and Global Network In Precipitation (GNIP) data from Greenland, Iceland and Svalbard. The REMO-iso output explains up to 40% of the interannual δ18O variability observed in ice cores, which is comparable to the model performance for precipitation. In terms of reproducing the observed variability the global model, ECHAM4-iso performs on the same level as REMO-iso. However, REMO-iso has smaller biases in δ18O and improved representation of the observed spatial δ18O-temperature slope compared to ECHAM4-iso. Analysis of the main modes of winter variability of δ18O shows a coherent signal in Central and Western Greenland similar to results from ice cores. The NAO explains 20% of the leading δ18O pattern. Based on the model output we suggest that methods to reconstruct the NAO from Greenland ice cores employ both δ18O and accumulation records.

  16. A strong control of the South American SeeSaw on the intra-seasonal variability of the isotopic composition of precipitation in the Bolivian Andes

    NASA Astrophysics Data System (ADS)

    Vimeux, Françoise; Tremoy, Guillaume; Risi, Camille; Gallaire, Robert

    2011-07-01

    Water stable isotopes (δ) in tropical regions are a valuable tool to study both convective processes and climate variability provided that local and remote controls on δ are well known. Here, we examine the intra-seasonal variability of the event-based isotopic composition of precipitation (δD Zongo) in the Bolivian Andes (Zongo valley, 16°20'S-67°47'W) from September 1st, 1999 to August 31st, 2000. We show that the local amount effect is a very poor parameter to explain δD Zongo. We thus explore the property of water isotopes to integrate both temporal and spatial convective activities. We first show that the local convective activity averaged over the 7-8 days preceding the rainy event is an important control on δD Zongo during the rainy season (~ 40% of the δD Zongo variability is captured). This could be explained by the progressive depletion of local water vapor by unsaturated downdrafts of convective systems. The exploration of remote convective controls on δD Zongo shows a strong influence of the South American SeeSaw (SASS) which is the first climate mode controlling the precipitation variability in tropical South America during austral summer. Our study clearly evidences that temporal and spatial controls are not fully independent as the 7-day averaged convection in the Zongo valley responds to the SASS. Our results are finally used to evaluate a water isotope enabled atmospheric general circulation model (LMDZ-iso), using the stretched grid functionality to run zoomed simulations over the entire South American continent (15°N-55°S; 30°-85°W). We find that zoomed simulations capture the intra-seasonal isotopic variation and its controls, though with an overestimated local sensitivity, and confirm the role of a remote control on δ according to a SASS-like dipolar structure.

  17. Circulation controls of the spatial structure of maximum daily precipitation over Poland

    NASA Astrophysics Data System (ADS)

    Stach, Alfred

    2015-04-01

    Among forecasts made on the basis of global and regional climatic models is one of a high probability of an increase in the frequency and intensity of extreme precipitation events. Learning the regularities underlying the recurrence and spatial extent of extreme precipitation is obviously of great importance, both economic and social. The main goal of the study was to analyse regularities underlying spatial and temporal variations in monthly Maximum Daily Precipitation Totals (MDPTs) observed in Poland over the years 1956-1980. These data are specific because apart from being spatially discontinuous, which is typical of precipitation, they are also non-synchronic. The main aim of the study was accomplished via several detailed goals: • identification and typology of the spatial structure of monthly MDPTs, • determination of the character and probable origin of events generating MDPTs, and • quantitative assessment of the contribution of the particular events to the overall MDPT figures. The analysis of the spatial structure of MDPTs was based on 300 models of spatial structure, one for each of the analysed sets of monthly MDPTs. The models were built on the basis of empirical anisotropic semivariograms of normalised data. In spite of their spatial discontinuity and asynchronicity, the MDPT data from Poland display marked regularities in their spatial pattern that yield readily to mathematical modelling. The MDPT field in Poland is usually the sum of the outcomes of three types of processes operating at various spatial scales: local (<10-20 km), regional (50-150 km), and supra-regional (>200 km). The spatial scales are probably connected with a convective/ orographic, a frontal and a 'planetary waves' genesis of high precipitation. Their contributions are highly variable. Generally predominant, however, are high daily precipitation totals with a spatial extent of 50 to 150 km connected with mesoscale phenomena and the migration of atmospheric fronts (35

  18. 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

  19. 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. PMID:27144269

  20. 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

  1. Multi-isotope composition of precipitation in Northern Germany during winter time

    NASA Astrophysics Data System (ADS)

    Böttcher, Michael E.; Schmiedinger, Iris; Lipka, Marko; Böttcher, Ernst O.; Böttcher, Tillman M. C.

    2014-05-01

    We investigated the multi-isotope (H-1, H-2, O-16, O-17, O-18) composition of precipitation (rain, snow) at locations in Northern Germany (Warnemünde, Oldenburg, Lüneburg) and the Netherlands (Texel Island) to derive local meteoric water lines. A particular focus was set on the impact of recent events Xaver and Dirk on stable isotope variations in high time-resolution. Sampling was carried out using a Hellmann-type rain gauge or, in the case of high-resolution sampling open sampling devices. At the Lüneburg site, the amount of fallen rain (volume per area of soil surface) was additionally quantified on a regular daily base. Isotope measurements were conducted by means of a new Picarro CRDS system (L2140-i) giving results in the usual delta-notation versus V-SMOW, and informations about H-2 and O-17 excess. Results are compared to continuous measurements at the GNIP station in Cuxhaven (NW-Germany) and the GMWL. As an example, during storm Xaver, respective variations in delta-18O and delta-2H values in snow and rain samples of up to 5 and 42 per mil were observed. Results for the German stations in the time period around storm Xaver are positioned close to the local meteoric water line proposed for Cuxhaven. Deviations from the GMWL are discussed.

  2. Spatial Variability in Instantaneous Photosynthetic Carbon and Oxygen Isotope Discrimination

    NASA Astrophysics Data System (ADS)

    Barbour, M. M.

    2007-12-01

    Stable carbon and oxygen isotope ratios of CO2 are useful tracers in studies of carbon and water cycling between the terrestrial biosphere and the atmosphere. Interpretation of variation in 13CO2 and C16O18O relies on models describing physical and biochemical processes and their associated fractionations. A layer of complexity not currently quantified or accounted for in canopy models is spatial variation in photosynthetic discrimination within a single leaf. A new measurement technique, employing tunable diode laser absorption spectrometry coupled to an open gas exchange system, enables online measurement of photosynthetic discrimination at high temporal resolution. Using this system, photosynthetic 13C and 18O discrimination was measured along leaves of a C3 monocot. For the forage cereal Triticale, 13C discrimination increased by 2‰ and 18O by 20‰ from the base to the tip of mature leaves when measured at saturating irradiance. The increase in 13C discrimination was associated with an increase in the leaf internal conductance of CO2, and 18O discrimination with carry-forward of evaporative enrichment along the leaf. When numerical averages are compared to flux- and area-weighted averages, the portion of the leaf approximately one third of the way from the base can be shown to provide the most representative area for scaling up.

  3. Spatial Statistics Preserving Interpolation Methods for Estimation of Missing Precipitation Data

    NASA Astrophysics Data System (ADS)

    El Sharif, H.; Teegavarapu, R. S.

    2011-12-01

    Spatial interpolation methods used for estimation of missing precipitation data at a site seldom check for their ability to preserve site and regional statistics. Such statistics are primarily defined by spatial correlations and other site-to-site statistics in a region. Preservation of site and regional statistics represents a means of assessing the validity of missing precipitation estimates at a site. This study will evaluate the efficacy of traditional deterministic and stochastic interpolation methods aimed at estimation of missing data in preserving site and regional statistics. New optimal spatial interpolation methods that are intended to preserve these statistics are also proposed and evaluated in this study. Rain gauge sites in the state of Kentucky, USA, are used as a case study for evaluation of existing and newly proposed methods. Several error and performance measures will be used to evaluate the methods and trade-offs in accuracy of estimation and preservation of site and regional statistics.

  4. The Origin of Moisture Sources for the North American Monsoon Using a Numerical Model and Precipitation Stable Isotopes

    NASA Astrophysics Data System (ADS)

    Hu, H.; Dominguez, F.

    2014-12-01

    This work evaluates the moisture sources that contribute to North American Monsoon precipitation over a 34-year period. The modified analytical dynamic recycling model (DRM) is used to evaluate the contributions from both oceanic and terrestrial regions. This computationally-efficient modeling framework reveals previously overlooked moisture source regions such as Central America and the Caribbean Sea in addition to the well-known Gulf of California and Gulf of Mexico source regions. Our results show that terrestrial evapotranspiration is as important as oceanic evaporation for NAM precipitation, and terrestrial sources contribute to approximately 40% of monsoonal moisture. There is a northward progression of moisture sources, beginning with Central America during the early season and transitioning north into the NAM region itself during the peak of the monsoon season. The most intense precipitation occurs towards the end of the season and tends to originate in the Gulf of California and tropical Pacific associated with tropical cyclones and gulf surges. Heavy stable isotopes of hydrogen and oxygen in precipitation (δD and δ18O) collected for every precipitation event measured in Tucson, AZ for the period 1981-2013 complement our numerical results. Our analysis shows that precipitation events linked to sources from the Gulf of Mexico and Caribbean Sea have a more positive isotopic composition than sources from the Gulf of California and Tropical Pacific. We also see that terrestrial regions that derive their precipitation from the Gulf of Mexico have more positive isotopic composition than those that derive their moisture from the Pacific.

  5. Experimental investigations of Si-isotope fractionation associated with Fe-Si co-precipitates in simulated Precambrian seawater

    NASA Astrophysics Data System (ADS)

    Zheng, X.; Beard, B. L.; Reddy, T. R.; Johnson, C.

    2014-12-01

    The Si cycle was dramatically different in the Precambrian ocean due to the absence of marine Si-secreting organisms. Precambrian Si isotopic compositions were largely controlled by chemical precipitation of Si, input of Si with different isotopic compositions (e.g., continental versus hydrothermal sources) and later alteration and diagenetic processes associated with silicification. In Precambrian banded iron formations (BIFs) and chert deposits there is an over 4‰ spread of Si isotopes (δ30Si), which stands in marked contrast to the narrow range (<0.5) measured in igneous rocks, highlighting the potential of using Si isotopes to reconstruct those processes that controlled the Precambrian marine Si cycle. However, unequivocal interpretations of Si isotope compositions measured in Precambrian Fe-Si rich sediments is hampered by a lack of understanding of Si-isotope fractionation factors associated with formation of these sediments and subsequent diagenetic processes. This study experimentally investigates Si isotope fractionation during the formation of Fe-Si co-precipitates, and between aqueous Si and Fe-Si co-precipitates. All experiments are conducted in an artificially prepared medium that mimics Archean seawater (e.g. Si: ~60 ppm), rather than in a simple Fe-Si solution, because previous studies have revealed distinct Fe isotope fractionation behaviors in artificial Archean seawater (AAS) compared to simple solutions. One set of experiments investigated oxidation of Fe2+ in the AAS at room temperature, which produced amorphous Fe-Si precipitates. Preliminary results show that δ30Si values of Fe-Si co-precipitates are ~2‰ lower than the initial AAS (Δ30Siprecip-AAS = -2.13 ± 0.18‰ (2σ)). A second set of experiments trace Si-isotope exchange between aqueous Si (AAS) and Fe-Si co-precipitates in an anaerobic chamber, using a 29Si spike (i.e. three-isotope method). The results of these experiments will form a basis for reliable interpretations of Si

  6. 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

  7. 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

  8. Interaction of valleys and circulation patterns (CPs) on spatial precipitation patterns in southern Germany

    NASA Astrophysics Data System (ADS)

    Liu, M.; Bárdossy, A.; Zehe, E.

    2013-11-01

    Topography exerts influence on the spatial precipitation distribution over different scales, known typically at the large scale as the orographic effect, and at the small scale as the wind-drift rainfall (WDR) effect. At the intermediate scale (1~10 km), which is characterized by secondary mountain valleys, topography also demonstrates some effect on the precipitation pattern. This paper investigates such intermediate-scale topographic effects on precipitation patterns, focusing on narrow-steep valleys in the complex terrain of southern Germany, based on the daily observations over a 48 yr period (1960~2007) from a high-density rain-gauge network covering two sub-areas, Baden-Wuerttemberg (BW) and Bavaria (BY). Precipitation data at the valley and non-valley stations are compared under consideration of the daily general circulation patterns (CPs) classified by a fuzzy rule-based algorithm. Scatter plots of precipitation against elevation demonstrate a different behavior of valley stations comparing to non-valley stations. A detailed study of the precipitation time series for selected station triplets, each consisting of a valley station, a mountain station and an open station have been investigated by statistical analysis with the Kolmogorov-Smirnov (KS) test supplemented by the One-way analysis of variance (One-way ANOVA) and a graphical comparison of the mean precipitation amounts. The results show an interaction of valley orientation and the direction of the CPs at the intermediate scale, i.e. when the valley is shielded from the CP which carries the precipitation, the precipitation amount within the valley is comparable to that on the mountain crest, and both larger than the precipitation at the open station. When the valley is open to the CP, the precipitation within the valley is similar to the open station but much less than that on the mountain. Such phenomenon where the precipitation is "blind" to the valleys at the intermediate scale conditioned on CPs is

  9. 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.

  10. [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. PMID:27506020

  11. 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. PMID:25265397

  12. Temperature Dependent Sr-Isotope (δ 88Sr) and Ca-Isotope (δ 44Ca) Fractionation in Carbonate Precipitates and Corals

    NASA Astrophysics Data System (ADS)

    Eisenhauer, A.; Fietzke, J.; Gussone, N.; Böhm, F.; Bock, B.; Nägler, T.

    2003-12-01

    The knowledge of the influence of temperature and other environmental factors on isotope fractionation of divalent cations like Ca2+ and Sr2+ during inorganic and biogenic controlled precipitation of calcium carbonate is crucial for their interpretation as paleo proxies. In order to extend our earlier studies on Ca-isotope fractionation (e.g. Gussone et al., 2003), we determined δ 88Sr isotope ratios on seawater and on corals. We define the stable Sr isotope ratio as δ 88Sr=((88Sr/86Sr)Sample/(88Sr/86Sr)Standard -1)*1000; Sr Standard is NBS 987. First measurements of the IAPSO seawater standard result in δ 88Sr of 0.38+/-0.02 ‰ . Coral CaCO3 precipitated from seawater in a temperature range from about 22° C to about 27° C correspond to δ 88Sr-values ranging from 0.17 ‰ to about 0.32 ‰ indicating that carbonate precipitated from seawater is isotopically lighter than seawater itself. The slope of 0.027 ‰ /° C for the temperature-δ 88Sr relationship in corals is about a factor of 1.7 larger than the slope of δ 44Ca ratios in inorganically precipitated aragonite. However, the fractionation α (T)=((88Sr/86Sr)CaCO3)/(88Sr/86Sr)Seawater) at a given temperature is about one order of magnitude less for Sr-isotopes relative to Ca-isotopes. The larger temperature-δ 88Sr gradient in comparison to the Ca-isotopes is interpreted to reflect the smaller ion potential and the correspondingly smaller mass of the associated Sr2+-aquocomplex. The observation that δ 88Sr and δ 44Ca are positively correlated with temperature points to the likelihood that kinetic or equilibrium fractionation effects and the mass of the associated acquocomplex control the degree of divalent cation isotope fractionation during CaCO3-precipitation. Reference: Gussone N., Eisenhauer A., Heuser A., Dietzel M., Bock B., Böhm F., Spero H., Lea D. W., Bijma J., and Nägler T. F. (2003) Model for Kinetic Effects on Calcium Isotope Fractionation (δ 44Ca) in Inorganic Aragonite and Cultured

  13. 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

  14. 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...

  15. High Spatial Resolution Isotope Ratio Imaging and 3D Reconstruction of Presolar SiC Grains

    NASA Astrophysics Data System (ADS)

    Lyon, I. C.; Henkel, T.; Clarke, A.

    2015-07-01

    Presolar SiC grains have been analysed with a new NanoSIMS for isotope ratio measurements of C, N and Si. High spatial resolution imaging suggests that nitrogen isotope heterogeneity within the grains may lead to anomalous results in the literature.

  16. Assessment of sulfate sources in high-elevation Asian precipitation using stable sulfur isotopes.

    PubMed

    Pruett, Lee E; Kreutz, Karl J; Wadleigh, Moire; Aizen, Vladimir

    2004-09-15

    Stable sulfur isotope measurements (delta34S) made on samples collected from a 2 m snowpit on the Inilchek Glacier, Tien Shan Mountains (42.16 degrees N, 80.25 degrees E, 5100 m) are used to estimate sources of sulfate (SO4(2-)) in high-elevation Central Asian precipitation. Comparison of snowpit oxygen isotope (delta18O) data with previous work constrains the age of the snowpit samples to the summer season during which they were retrieved (1999). Delta34S measurements were made at 10 cm resolution (20 samples total), with delta34S values ranging from 0.4/1000 during background ([SO4(2-)] < 1 microequiv L(-1)) periods to 19.4/1000 during a single high [SO4(2-)] event. On the basis of the significant correlation (r = 0.87) between [SO4(2-)] and delta34S values, coupled with major ion concentration time series and concentration ratios, we suggest a two-component mixing system consisting of evaporite dust and anthropogenic SO4(2-) to explain the observed delta34S values. Using a regression model, we estimate that during the 1999 summer season 60% of the deposited SO4(2-) was from an evaporite dust source, while 40% of the SO4(2-) was from anthropogenic sources. Due to the potentially large and unconstrained range of delta34S values for both evaporite and anthropogenic SO4(2-) sources in Asia, the error in our estimates is difficult to assess. However, the delta34S data from the 1999 Tien Shan snowpit provide the first unambiguous identification of evaporite and anthropogenic SO4(2-) in high-elevation Asian precipitation, and future ice core studies using improved analysis techniques and source delta34S values can provide detailed information on sulfur biogeochemistry and anthropogenic impacts in Asian alpine regions. PMID:15487779

  17. Spatially coherent trends of annual maximum daily precipitation in the United States

    NASA Astrophysics Data System (ADS)

    Sun, Xun; Lall, Upmanu

    2015-11-01

    A new multilevel, hierarchical Bayesian model is developed to simultaneously identify clusters of stations with similar temporal patterns, the trend associated with each cluster and for the individual stations within each cluster. An application to the annual maximum daily precipitation in the United States for a common 70 year (1941-2010) period across the HADEX2 sites is presented. The model identifies statistically homogeneous regions, spatially clustering the data into groups according to the intensity and the trend. Partial pooling of model parameters for each group is considered. Spatially consistent trends are detected in the Midwest and Northeast U.S., at the cluster and at the station level. The new approach can dramatically improve trend identification for precipitation extremes; e.g., all 14 stations in the Midwest report a significant trend as opposed to only 4 stations based on single site analysis. The method is generally applicable for improving trend identification over a heterogeneous region.

  18. Chemical and isotope characteristics of a tufa-precipitating stream in Karwów (south-central Poland)

    NASA Astrophysics Data System (ADS)

    Duliński, Marek; Gradziński, Michał; Motyka, Jacek; Czop, Mariusz

    2016-04-01

    Chemical and isotope composition of a tufa-precipitating spring located in Karwów (south-central Poland) is described with the emphasis on the CO2-H2O-CaCO3 system. Carbonate solution is formed with participation of biogenic carbon dioxide and appears at the surface close to saturation state with respect to calcite. At the outflow of the spring the water is characterized by long-term stability of physical and chemical parameters. Along the course of the spring the tufa bed is formed as a result of CO2 outgassing. The carbon and oxygen isotope investigations were performed both on water solutions and the tufa calcite precipitated on CaCO3 plates exposed in water for different periods of time. In general, results of the 13C analyses and numerical modeling using NETPATH code suggest that calcite is precipitated close to carbon isotope equilibrium conditions except for the situations when the extreme outgassing of CO2 takes place. Several measured precipitate samples have shown distinctly lower δ18O values than expected for tufa formation under equilibrium conditions. This cannot be explained by kinetic effects known from karstic caves or lake studies as they lead to higher δ18O values of precipitated carbonates than at isotope equilibrium. Also, short-term fluctuations of water temperature cannot be responsible for the observed deviations in oxygen isotope composition of measured tufa samples from equilibrium values. Further work is needed to better understand the factors controlling 18O isotope composition of tufa deposits.

  19. Oxygen and hydrogen stable isotope content in daily-collected precipitation samples at Dome C, East Antarctica

    NASA Astrophysics Data System (ADS)

    Dreossi, Giuliano; Stenni, Barbara; Del Guasta, Massimo; Bonazza, Mattia; Grigioni, Paolo; Karlicek, Daniele; Mognato, Riccardo; Scarchilli, Claudio; Turchetti, Filippo; Zannoni, Daniele

    2016-04-01

    Antarctic ice cores allow to obtain exceptional past climate records, thanks to their water stable isotope content, which provides integrated tracers of the atmospheric water cycle and local climate. Low accumulation sites of the East Antarctic plateau provide the oldest ice core records, with the record-breaking EPICA Dome C drilling covering the last eight climate cycles. However, the isotope-temperature relationship, commonly used to derive the temperature, may be characterized by significant geographical and temporal variations. Moreover, post-depositional effects may further complicate the climate interpretation. A continuous series of precipitation data is needed in order to gain a better understanding of the factors affecting the water stable isotopes in Antarctic precipitation at a specific site. In this study, we use the first and so-far only multi-year series of daily precipitation sampling and isotope measurements from the French-Italian Concordia Station, located at Dome C in East Antarctica (75°06'S 123°21'E; elevation: 3233 m a.s.l.; mean annual temperature: -54.5°C; snow accumulation rate: 25 kg m-2 yr-1), where the oldest deep Antarctic ice core has been retrieved. Surface air temperature data have been provided by the US automatic weather station (AWS), placed 1.5 km away from the base, while tropospheric temperature profiles are obtained by means of a radiosonde, launched once per day by the IPEV/Italian Antarctic Meteo-climatological Observatory. The new dataset also enables us for the first time to study the isotope-temperature relationship distinguishing between different types of precipitation, namely diamond dust, hoar frost and snowfall, identified by the observations carried out by the winter-over personnel collecting the snow samples. Here we present the complete data series of water stable isotopes in precipitation at Dome C spanning the time period from 2008 to 2014, in the framework of the PNRA PRE-REC project.

  20. Early Eocene changes in the frequency and spatial distribution of extreme precipitation events

    NASA Astrophysics Data System (ADS)

    Carmichael, Matthew; Lunt, Daniel; Pancost, Richard

    2015-04-01

    Global warming over the next 100 years is likely to result not only in changes to the spatial distribution of mean annual precipitation, but also to the seasonality of precipitation and the frequency of hydrological extremes, with far-reaching socio-economic and ecological impacts. The study of the sensitivity of the hydrological cycle to episodes of global warmth in the geologic past is receiving increased attention from the paleoclimate community, but our understanding of the occurrence of hydrological extremes remains limited. The warming associated with the Paleocene-Eocene Thermal Maximum (PETM) hyperthermal (~56 Ma) has received widespread attention given its global nature, rapid onset and transient nature. A range of geomorphological, microfossil and biomarker proxies suggest significant hydrological changes occurred at the PETM which have traditionally been interpreted in terms of changes in mean annual precipitation; recently changes in the frequency of hydrological extremes at the PETM have also been suggested. In this work, we seek to better understand whether numerical climate models run with boundary conditions appropriate for the early Eocene (56 - 49 Ma) are capable of simulating changes in the frequency of intense precipitation ('storm') events by analysing GCM-simulated precipitation rates at an hourly frequency. Our Eocene simulations are performed at x2 and x4 preindustrial CO2 using a coupled atmosphere-ocean GCM, HadCM3L. Differences in climatology between high and low CO2 may be considered analogous to the changes which occurred at the PETM. Our results indicate significant changes occur in the precipitation intensity-frequency relationships at locations which correspond to sites from which PETM proxies exist. The percentage of time during which precipitation occurs and the overall number of events lasting longer than an hour declines in the high-CO2 model. These changes tend to occur with an associated increase in mean storm precipitation

  1. 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.

  2. 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.

  3. 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.

  4. Little Ice Age Recorded in Mn/Fe Precipitates by Pb and Nd Isotopes

    NASA Astrophysics Data System (ADS)

    Liebetrau, V.; Eisenhauer, A.; Frei, R.; Bock, B.; Kronz, A.; Hansen, B. T.; Leipe, T.

    2002-12-01

    Ferromanganese precipitates of the Baltic Sea can be dated by the 226Raexcess/Ba-method (Liebetrau et al., 2002). Recent investigations have shown that these precipitates may represent perfect archives for the postglacial history of the circum Baltic area. In particular, these precipitates offer the possibility to study short term variations of the Scandinavian shield erosion and climate change during the Little Ice Age. The Nd isotope record of a selected Mn/Fe crust from the Mecklenburg Bay of the Baltic Sea shows a significant change of the ɛ Nd-value from around -13 for ages older than 1100 years AD to approx. -18 around 1600 years AD. This shift can be explained by increased erosion and input of Nd from Archean Scandinavian sources and/or a reduced inflow of North Atlantic water (ɛ Nd = -13) to the Baltic Sea. Comparison with a temperature reconstruction for Fennoscandia (Mann, 2001) documents a close relationship of the ɛ Nd record with temperature variations during the Little Ice Age because negative ɛ Nd-value tend to correlate with lower temperature during the last 1000 years. In contrast, the pattern of 207Pb/206Pb record closely correlates with historically known changes of anthropogenic activities during the industrial revolution and times of enhanced Ag and Pb mining. Nd and Pb are correlated before 1100 AD but are decoupled after at about 1100 years AD. We propose that Pb appears to be more sensitive to anthropogenic activities since about 1100 AD. Liebetrau V., Eisenhauer A., Gussone N., W”rner G., Hansen B.T., and Leipe T., 2002, 226Raexcess/Ba growth rates and U-Th-Ra-Ba systematic of Baltic Mn/Fe crusts, Geochim. Cosmochim. Acta, 66, 73-83 Mann M.E., 2001, The Little Ice Age, in: Encyclopedia of Environmental Global Change

  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. 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

  7. Comparison of spatial interpolation methods for the estimation of precipitation distribution in Distrito Federal, Brazil

    NASA Astrophysics Data System (ADS)

    Borges, Pablo de Amorim; Franke, Johannes; da Anunciação, Yumiko Marina Tanaka; Weiss, Holger; Bernhofer, Christian

    2016-01-01

    Available climatological information of Distrito Federal does not satisfy the requirements for detailed climate diagnosis, as they do not provide the necessary spatial resolution for water resources management purposes. Annual and seasonal climatology (1971-2000) of precipitation from 6 meteorological stations and 54 rain gauges from Central Brazil were used to test eight different spatial interpolation methods. Geographical factors (i.e., altitude, longitude and latitude) explain a large portion of precipitation in the region, and therefore, multivariate models were included. The performance of estimations was assessed through independent validation using mean square error, correlation coefficient and Nash-Sutcliffe efficiency criterion. Inverse distance weighting (IDW), ordinary kriging (OK) and the multivariate regression with interpolation of residuals by IDW (MRegIDW) and OK (MRegOK) have performed the lowest errors and the highest correlation and Nash-Sutcliffe efficiency criterion. In general, interpolation methods provide similar spatial distributions of rainfall wherever observation network is dense. However, the inclusion of geographical variables to the interpolation method should improve estimates in areas where the observation network density is low. Nevertheless, the assessment of uncertainties using a geostatistical method provides supplementary and qualitative information which should be considered when interpreting the spatial distribution of rainfall.

  8. Spatial Distribution of The Atmospheric Precipitation Anomalies On The Russian Plain Over The Last Millennium

    NASA Astrophysics Data System (ADS)

    Popova, V. V.

    Data on humidity condition variation on the Russian plain over last millennia basing on documentary and indirect historical evidences (reconstructed atmospheric precip- itation anomalies basing on pollen data, evidences of river runoff and Caspian Sea level variation) have been analysed. As result it has been derived patterns allowed to charge about spatial distribution of precipitation anomalies during Medieval (XI-XIII) period and Little Ice Age (XVII-XIX) from the view point of spatial structure pre- cipitation fluctuation over the Russian plain determined basing on instrumental data. The comparing shows the coincidence between spatial distribution of anomalies dur- ing the Little Ice Age and in 1940-1960-th - period of prevailing of meridional types of circulation (according to B.L.Dzerdzeevsky classification). It has been concluded that Little Ice Age seemed to be characterised by predominance of meridional circu- lation types, for the spatial structure of precipitation fluctuations on the Russian Plain it keeps stability over last 300-400 years. The study was supported by the Russian Foundation for Basic Reserch (grant 01-05- 64395)

  9. Spatial pattern of nitrogen isotopes as an indicator of ecosystem responses to rainfall in semi-arid and arid grasslands

    NASA Astrophysics Data System (ADS)

    WANG, C.; Bai, E.; Liu, D.; Fang, T. Y.; Jiang, P.; Han, G. X.

    2013-12-01

    Nitrogen (N) is an essential element for plant growth, however, whether it is a limiting factor of plant growth in water-limited areas is still not clear. Here we examined spatial variations of plant and soil stable N isotopes along a 3200 km precipitation gradient and proposed a conceptual model to explain ecosystem responses to increasing precipitation in arid and semi-arid grasslands in China. Soil δ15N increased with increasing MAP in areas with MAP < 200 mm, but decreased in areas with 200 mm < MAP < 500 mm. Variations of foliar δ15N, soil total N, and soil C: N provided further evidence of a threshold at MAP = 200 mm for precipitation effects. Results indicated that soil microbes can be activated by precipitation even when MAP < 200 mm while plant N uptake can only be activated when MAP > 200 mm. In areas with MAP < 200 mm, productivity was limited by water, but not nitrogen, although soil N is low. This study provides fundamental inputs for future process-based modeling of nutrient cycling in arid and semi-arid areas. If future climate change leads to drier climate in dryland, the uncoupled plant and microbial response may cause more N losses and higher ecosystem vulnerability. 3 Soil organic carbon (Soil C, a), total nitrogen (Soil N, b), C/N (c) and δ15N (d) of study sites along a MAP gradient. Relationship between MAP and foliar δ15N (a) and root δ15N (b).

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. 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. PMID:19021238

  15. 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

  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. 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

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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

  3. The effect of isotopic substitution of deuterium for hydrogen on the morphology of products precipitated from synthetic Bayer solutions

    NASA Astrophysics Data System (ADS)

    Loh, J. S. C.; Watling, H. R.; Parkinson, G. M.

    2002-04-01

    In the production of alumina (Al 2O 3), the precipitation of gibbsite (Al(OH) 3) is the slowest step in the Bayer process. Gibbsite growth rates are generally in the vicinity of microns per hour. Thus, research is focussed on increasing productivity (gibbsite precipitation rates) without compromising product quality. Fundamental to this is an improved understanding of gibbsite growth mechanisms. Isotopic substitution of deuterium for hydrogen in synthetic Bayer (sodium aluminate) solutions was used primarily to investigate deprotonation and reprotonation of the surface hydroxyl groups. Gibbsite precipitates in a highly alkaline solution. The hydroxyl groups situated on the surfaces of the growing crystals are likely to be deprotonated because the pH of the Bayer liquor is >14 and the pK a for the surface protons is in the range of 9-10. The rate of gibbsite growth may therefore depend on the deprotonation and reprotonation of the hydroxyl groups, as the gibbsite crystal lattice consists of hydrogen bonded layers of Al(OH) 3. However, the gibbsite precipitation rates from equivalent sodium aluminate solutions (NaAl(OH) 3 and NaAl(OD) 3) were very similar, indicating that the deprotonation and reprotonation of the hydroxyl groups are not rate-limiting. Nonetheless, the isotopic substitution of deuterium for hydrogen in synthetic Bayer solutions did have effects on the gibbsite solubility, crystallization growth process, product phase and morphology. This paper focuses on the changes in product morphology. Isotopic substitution resulted in changes in the orientation of nuclei formed on seed surfaces as well as the nuclei morphology. This is the first time that isotopic substitution has been used to investigate gibbsite precipitation in synthetic Bayer solutions.

  4. 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

  5. Stable isotope investigation of the Columbus, Ohio, water supply by examining precipitation, tap water, and surface/reservoir waters

    NASA Astrophysics Data System (ADS)

    Leslie, D. L.; Lyons, W. B.

    2011-12-01

    Management of our water resources requires that human intervention as well as natural processes in the hydrologic cycle be fully understood, and integrated watershed management strategies be implemented to monitor variation and to maximize water resources. In this study of regional water supply, we utilize the stable isotopes of water to characterize the flow and relative residence time of water within a human-dominated watershed-reservoir system. Tap water, precipitation, and water from three reservoirs used for domestic water supply were collected in Franklin County, Ohio, from August 2010 until July 2011. Samples were analyzed for δ18O and δD by a Picarro WS-CRDS Analyzer for Isotopic Water - Model L1102-i at The Ohio State University. Reservoir waters (δ18O= -9.0% to -4.8% and δD= -61% to -30%) are more enriched during the spring/summer months and more depleted during the fall/winter months, following changes in precipitation and capacity of each reservoir. Tap water samples (δ18O= -9.1% to -4.3% and δD= -58% to -29%), distributed from the Dublin Road Water Plant (DRWP) which utilizes surface water from Griggs and O'Shaughnessy Reservoirs on the Scioto River, display an isotopic mixture of these reservoir waters and precipitation. These data demonstrates how quickly precipitation moves through the water conveyance system. Previously collected Columbus, Ohio, tap water samples reported by Bowen et al. (2007) demonstrated a seasonal lag in the city's water supply with more enriched precipitation from the summer months showing up in the water supply during the fall/winter seasons, and more depleted precipitation from winter months being part of the water supply in the spring/summer seasons. The tap water samples from the Bowen et al. (2007) study were distributed by Hap Cremean Water Plant (HPWP) that utilizes surface water from Hoover Reservoir on Big Walnut Creek. This isotopic signature of seasonal enrichment and depletion in the tap water that does not

  6. 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

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

    NASA Astrophysics Data System (ADS)

    Scholl, Martha A.; Murphy, Sheila F.

    2014-05-01

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

  8. 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

  9. 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

  10. Effects of changes in moisture source and the upstream rainout on stable isotopes in summer precipitation - a case study in Nanjing, East China

    NASA Astrophysics Data System (ADS)

    Tang, Y.; Pang, H.; Zhang, W.; Li, Y.; Wu, S.; Hou, S.

    2015-04-01

    In the Asian monsoon region, variations in the stable isotopic composition of speleothems have often been attributed to the "amount effect". However, an increasing number of studies suggest that the "amount effect" in local precipitation is insignificant or even non-existent. To explore this issue further, we examined the variability of daily stable isotopic composition (δ18O) in summer precipitation of 2012-2014 in Nanjing, East China. We found that δ18O was not significantly correlated with local rainfall amount, but could be linked to changes in the location and rainout processes of precipitation source regions. Our findings suggest that the stable isotopes in precipitation could signal the location shift of precipitation source regions in the intertropical convergence zone (ITCZ) over the course of the monsoon season. As a result, changes in moisture source location and upstream rainout effect should be taken into account when interpreting the stable isotopic composition of speleothems in the Asian monsoon region.

  11. Spatial-temporal change in precipitation patterns based on the cloud model across the Wei River Basin, China

    NASA Astrophysics Data System (ADS)

    Huang, Shengzhi; Hou, Beibei; Chang, Jianxia; Huang, Qiang; Chen, Yutong

    2015-04-01

    It is of significant importance to investigate the spatial-temporal change in precipitation patterns due to its great effects on droughts, floods, soil erosion and water resource management. A complete investigation of precipitation structure and its distribution pattern based on daily precipitation covering 1960-2005 at 21 meteorological stations in the Wei River Basin has been performed. In order to comprehensively and objectively describe the changing pattern of precipitation, the cloud model is employed to quantitatively analyse the average, uniformity and stability of precipitation. Results indicate the following: (1) the occurrence of different precipitation durations exhibits a positive exponential curve with the decrease in precipitation durations, and 1-3-day events are the predominant precipitation events which have an increasing trend; (2) precipitation and its non-uniformity is increasingly reducing, while its stability increases initially then decreases; (3) mean precipitation reduces from southeast to northwest, and the precipitation of the Guanzhong Plain has a low uniformity and stability due to its location and increasingly intensifying human activities. The cloud model provides a new idea and quantitative measure for the evaluation of the uniformity and stability of precipitation.

  12. Spatial modelling of summer precipitation over the Czech Republic using auxiliary geographical variables

    NASA Astrophysics Data System (ADS)

    Moliba Bankanza, J. C.

    2010-09-01

    The aim of this study is to develop the spatial model of summer precipitation over the Czech Republic using auxiliary geographical variables in order to produce gridded data needed for various applications. Daily precipitation data from 203 stations for the period 1971 - 2003 are used. Model is performed at different time steps (year, ten-years, and entire period). Considering that models performed at different time steps can vary significantly, it was necessary to verify two assumptions before the development of spatial prediction: (1) whether geographical variables control significantly the spatial distribution of summer precipitation over the Czech Republic; (2) and whether the effects of significant geographical variables (model parameters) do not vary significantly in time. Various candidate geographical predictors are evaluated in the stepwise regression models for summer precipitation: (1) a set of omnidirectional parameters of the elevation characterizing an area of 3 km x 3 km around meteorological stations, (2) various cross products calculated between geographical coordinates and elevation or topographic parameters, (3) slope and four facets of slope aspect which characterize the orographic regimes over the Czech Republic, (4) land cover parameters describing areas of about 10 km by 10 km around meteorological stations and (5) geographical coordinates. The orographic parameters are derived from the 1 km resolution digital elevation model (DEM), while the land cover parameters are derived from the 1 km resolution CORINE (Coordination of information on the environment) land cover data. To assure stability of the regression equations and comparability of regression models in time, both orthogonally rotated Principal Component Analysis (PCA) and frequency of significant predictors - selected using stepwise regression at each time step - are used to select identical significant independent variables for various time steps. Multivariate regression

  13. 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.

  14. 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

  15. 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.

  16. Spatial and altitudinal variation of precipitation and the correction of gridded precipitation datasets for the Upper Indus Basin and the Hindukush-Karakoram-Himalaya

    NASA Astrophysics Data System (ADS)

    Khan, Asif; Richards, Keith S.; Parker, Geoffrey T.; McRobie, Allan; Booij, Martijn J.; Duan, Zheng; Naz, Bibi S.; Lee, Junhak; Khan, Mujahid

    2015-04-01

    Precise and accurate precipitation data (of both snow and rain) are a vital input for hydrological modeling, climatic studies and glacier mass balance analysis. This study investigates the accuracy of eight widely used gridded datasets, based on mass balance assessments, for the Upper Indus Basin (UIB) in the Himalayas-Karakoram-Hindukush (HKH) mountain region. The eight datasets are: 1) Global Precipitation Climatology Project (GPCP) v 2.2, 2) Climate Prediction Centre (CPC) Merged Analysis of Precipitation (CMAP), 3) National Centers for Environmental Prediction (NCEP) / National Center for Atmospheric Research (NCAR), 4) Global Precipitation Climatology Centre (GPCC), 5) Climatic Research Unit (CRU) v 3.2.2, 6) Asian Precipitation Highly Resolved Observational Data Integration Towards Evaluation of Water Resources (APHRODITE), 7) Tropical Rainfall Measuring Mission (TRMM) 3B33 v 7, and 8) European Reanalysis (ERA) interim data. Precipitation derived from these datasets has been compared with the sum of flow, MODIS ETact (Actual Evapo-transpiration), and glacier imbalance contribution to flows. All these datasets significantly underestimate precipitation, being 40-80% less than the measured flows, except for the NCEP/NCAR and ERA interim datasets, which only slightly underestimate precipitation. This is the case for almost all watersheds in the UIB, particularly the Gilgit, Hunza, Shigar and Astore watersheds. To provide alternative, more physically-reasonable precipitation estimates, annual and seasonal (October-May and June-September) precipitation values have been derived for the entire UIB using multiple regressions relating precipitation for 46 climate stations to the local altitude, slope, aspect, latitude and longitude. The results are distributed across the whole basin on a 1km grid, with an estimated uncertainty of 5-10%. The spatial pattern shows good agreement with the Randolph Glacier Inventory (RGI) v 3.2 data, and with previous local studies that

  17. Preliminary spatial Standardized Precipitation Index (SPI) drought reconstructions for central and northern Mexico

    NASA Astrophysics Data System (ADS)

    Gutierrez-Garcia, G.; Mendez, J. M.; Magana, V.; Villanueva-Diaz, J.

    2007-05-01

    We developed a spatial drought reconstruction of the Standardized Precipitation Index (SPI) for northern and central Mexico based on the relationship between tree growth and climate. Many previous tree-rings studies have successfully reconstructed drought indices as Palmer Drought Severity Index (PDSI), although SPI has become a widely accepted drought index; to our knowledge no SPI reconstructions have been developed using tree-ring chronologies over our study region. The methodology used in this work was the Point by Point Regression (PPR). The data set used was a network of tree-ring chronologies for Mexico and south United States and a 7-month Standardized Precipitation Index (SPI) for the season November - May. The observed SPI was based on the Pearson Type III distribution (Guttman 1999), calculated from a 1-degree monthly precipitation dataset (Chen et al 2002). In order to maximize the number of tree-ring chronologies we set our calibration and reconstruction periods for 1948-1985 and 1801- 1985, respectively. According with our analysis, El Nino events are mainly associated with wetter condition over northern Mexico, while La Nina events are characterized by dry conditions. This reconstruction reproduces the 1950s drought which affected most of northern Mexico, the Great Plains and the southwestern United States. Results are compared with other reconstructed gridded drought indices available for the same area (Cook et al 2004).

  18. 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.

  19. 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.

  20. 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

  1. The influence of solution stoichiometry on surface-controlled Ca isotope fractionation during Ca carbonate precipitation from Mono Lake, California

    NASA Astrophysics Data System (ADS)

    Nielsen, L. C.; Depaolo, D. J.

    2010-12-01

    Precipitation of calcite and aragonite from aqueous solution causes kinetic stable Ca isotope fractionation under conditions where Ca2+ is greatly in excess of CO32-. Research on carbonate mineral growth from low Ca2+:CO32- activity ratio solutions is lacking. Mono Lake, California is a highly alkaline lake with a Ca2+:CO32- activity ratio of 9.6 x 10-4, over five orders of magnitude lower than typical terrestrial fresh and ocean water. Aragonitic tufa towers grow along the lakeshore due to the mixing of lake water and Ca-rich spring water, while fine aragonite particles precipitate directly from the lake water, accumulating on the lake bottom. Variations in the Ca2+:CO32- activity ratio affect calcite growth kinetics and could affect the partitioning of Ca isotopes during carbonate precipitation. However, the relationship between solution stoichiometry, microscopic mineral growth mechanisms and calcium isotope fractionation is poorly understood. We analyzed the Sr and Ca isotopic compositions of a suite of lake water, spring, tufa and lake bottom sediment samples from the Mono Basin. Using the Sr isotope signatures of endmember water sources (pure lake water and shoreline spring water), we determined the compositions of carbonate mineral growth solutions, associated isotope separations (Δ44/40Cas-f = δ44/40Casolid - δ44/40Cafluid) and precipitation rates. While lake bottom aragonite precipitates directly from lake water (Ca2+:CO32- ≈ 10-3), tufa grows from mixed solutions with Ca2+:CO32- activity ratios approaching 10, so carbonate precipitation in Mono Lake spans a four order of magnitude range in solution stoichiometry. At Mono Lake, Δ44/40Cas-f and calculated precipitation rates vary between -0.6±0.15‰ at 1.5×10-9 mol m-2 s-1 for aragonite precipitating from lake water and ~ -1.0±0.15‰ at up to 4×10-8 mol m-2 s-1 for tufa growing from mixed spring and lake water. These values are consistent with fractionation observed during CaCO3 precipitation at

  2. 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

  3. 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.

  4. 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.

  5. Variation in the Stable Carbon and Nitrogen Isotope Composition of Plants and Soil along a Precipitation Gradient in Northern China

    PubMed Central

    Ma, Jian-Ying; Sun, Wei; Liu, Xiao-Ning; Chen, Fa-Hu

    2012-01-01

    Water availability is the most influential factor affecting plant carbon (δ13C) and nitrogen (δ15N) isotope composition in arid and semi-arid environments. However, there are potential differences among locations and/or species in the sensitivity of plant δ13C and δ15N to variation in precipitation, which are important for using stable isotope signatures to extract paleo-vegetation and paleo-climate information. We measured δ13C and δ15N of plant and soil organic matter (SOM) samples collected from 64 locations across a precipitation gradient with an isotherm in northern China. δ13C and δ15N for both C3 and C4 plants decreased significantly with increasing mean annual precipitation (MAP). The sensitivity of δ13C to MAP in C3 plants (-0.6±0.07‰/100 mm) was twice as high as that in C4 plants (−0.3±0.08‰/100 mm). Species differences in the sensitivity of plant δ13C and δ15N to MAP were not observed among three main dominant plants. SOM became depleted in 13C with increasing MAP, while no significant correlations existed between δ15N of SOM and MAP. We conclude that water availability is the primary environmental factor controlling the variability of plant δ13C and δ15N and soil δ13C in the studied arid and semi-arid regions. Carbon isotope composition is useful for tracing environmental precipitation changes. Plant nitrogen isotope composition can reflect relative openness of ecosystem nitrogen cycling. PMID:23272186

  6. On the spatial and temporal variability of ENSO precipitation and drought teleconnection in mainland Southeast Asia

    NASA Astrophysics Data System (ADS)

    Räsänen, T. A.; Lindgren, V.; Guillaume, J. H. A.; Buckley, B. M.; Kummu, M.

    2015-11-01

    The variability in the hydroclimate over mainland Southeast Asia is strongly influenced by the El Niño-Southern Oscillation (ENSO) phenomenon, which has been linked to severe drought and floods that profoundly influence human societies and ecosystems alike. However, the spatial characteristics and long-term stationarity of ENSO's influence in the region are not well understood. We thus aim to analyse seasonal evolution and spatial variations in the effect of ENSO on precipitation over the period of 1980-2013, and long-term variation in the ENSO-teleconnection using tree-ring derived Palmer Drought Severity Indices (PDSI) that span from 1650-2004. We found that the majority of the study area is under the influence of ENSO, which has affected the region's hydroclimate over the majority (96 %) of the 355 year study period. Our results further indicate that there is a pattern of seasonal evolution of precipitation anomalies during ENSO. However, considerable variability in the ENSO's influence is revealed: the strength of ENSO's influence was found to vary in time and space, and the different ENSO events resulted in varying precipitation anomalies. Additional research is needed to investigate how this variation in ENSO teleconnection is influenced by other factors, such as the properties of the ENSO events and other ocean and atmospheric phenomena. In general, the high variability we found in ENSO teleconnection combined with limitations of current knowledge, suggests that the adaptation to extremes in hydroclimate in mainland Southeast Asia needs to go beyond "predict-and-control" and recognise both uncertainty and complexity as fundamental principles.

  7. 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.

  8. 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.

  9. Spatial Patterns of Precipitation Anomalies in Eastern China During Centennial Cold and Warm Periods of the Past 2000 Years

    NASA Astrophysics Data System (ADS)

    Hao, Z.

    2015-12-01

    The spatial patterns of precipitation anomalies in eastern China during both warm and cold periods over the past 2000 years were studied. Four warm periods (ad 650-750, ad 1000-1100, ad 1190-1290, and ad 1900-2000) and five cold periods (ad 440-540, ad 780-920, ad 1390-1460, ad 1600-1700, and ad 1800-1900) were selected on a centennial timescale, referring to the synthesized temperature changes over China and Northern Hemisphere. The regional differences in precipitation were analyzed and compared using a data set consisting of the grades in severity of floods and droughts as derived from Chinese historical documents. The results showed that there has been no fixed spatial pattern of precipitation anomalies during either cold or warm periods in eastern China over the past 2000 years. For the most of warm periods, there existed coherence of spatial pattern with dry condition only occurred over north of the Yangtze River, and the consistent spatial patterns were found between the periods 650-750 and 1190-1290, 650-750 and 1000-1100. For the cold periods, the precipitation showed various spatial patterns, and similarities were only presented in the two periods of 1600-1700 and 1800-1900 featured by meridional distribution. Comparing the spatial patterns between cold and warm periods, inverse pattern of 440-540 and 1900-2000 over the most study area can be detected, but similar pattern was also found between the periods 1800-1900 and 1900-2000, and 1600-1700 and 1900-2000. Our results implicated that the relationship between temperature and spatial pattern of precipitation anomaly has high complexity, which would be of significance to understanding the spatial pattern of precipitation in the future climate change study.

  10. The Indian Ocean Zonal Mode over the past millennium in observed and modeled precipitation isotopes

    NASA Astrophysics Data System (ADS)

    Konecky, Bronwen; Russell, James; Vuille, Mathias; Rehfeld, Kira

    2014-11-01

    The Indian Ocean Zonal Mode (IOZM) has gained considerable attention in the past decade due to its role in causing widespread flooding and droughts in the continents and islands surrounding the Indian Ocean. The IOZM has also been observed to vary on a low-frequency (multi-decadal) basis, making its behavior important to understand both for mid-range 21st century climate prediction and for paleoclimate studies. Despite efforts to reconstruct the IOZM using corals and other high-resolution proxies, nonstationarities in the response of paleoclimate proxies to the IOZM have also been noted, raising the possibility that the IOZM may be difficult to reconstruct or to predict in the long-term. It is therefore critical to assess the low-frequency component of the IOZM in observed, modeled, and paleoclimate data from the Indian Ocean region in order to identify nonstationary behavior and to assess its role in low-frequency climate variations. We present an analysis of low-frequency and nonstationary behavior in the IOZM on multi-decadal to centennial timescales using a combination of modeled, observed, and proxy reconstructions of δ18O/δDprecip. In order to assess multiple timescales of low-frequency variability, we focus on two key time periods: the historical period (1870-2003), and the past millennium (1000 C.E.-present). We find significant nonstationarities in the relationships between the IOZM, precipitation amount, and δ18Oprecip/δDprecip during the historical period. These relationships vary on a multi-decadal basis in our model and in observed/reanalysis datasets. Air-sea interactions in the Indo-Pacific Warm Pool and teleconnections to the Pacific Ocean, as well as the phase of the IOZM itself, may contribute to this nonstationary behavior. We examine the potential ramifications of nonstationary IOZM behavior using a synthesis of spatially distributed proxy archives of δ18Oprecip/δDprecip from both sides of the IOZM region spanning the past millennium. Our

  11. Modeling the Spatial and Temporal Variation of Monthly and Seasonal Precipitation on the Nevada Test Site and Vicinity, 1960-2006

    USGS Publications Warehouse

    Blainey, Joan B.; Webb, Robert H.; Magirl, Christopher S.

    2007-01-01

    The Nevada Test Site (NTS), located in the climatic transition zone between the Mojave and Great Basin Deserts, has a network of precipitation gages that is unusually dense for this region. This network measures monthly and seasonal variation in a landscape with diverse topography. Precipitation data from 125 climate stations on or near the NTS were used to spatially interpolate precipitation for each month during the period of 1960 through 2006 at high spatial resolution (30 m). The data were collected at climate stations using manual and/or automated techniques. The spatial interpolation method, applied to monthly accumulations of precipitation, is based on a distance-weighted multivariate regression between the amount of precipitation and the station location and elevation. This report summarizes the temporal and spatial characteristics of the available precipitation records for the period 1960 to 2006, examines the temporal and spatial variability of precipitation during the period of record, and discusses some extremes in seasonal precipitation on the NTS.

  12. 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

  13. 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.

  14. Spatial-temporal changes in Andean plateau climate and elevation from stable isotopes of mammal teeth

    NASA Astrophysics Data System (ADS)

    Bershaw, John; Garzione, Carmala N.; Higgins, Pennilyn; MacFadden, Bruce J.; Anaya, Frederico; Alvarenga, Herculano

    2010-01-01

    Paleoelevation constraints from fossil leaf physiognomy and stable isotopes of sedimentary carbonate suggest that significant surface uplift of the northern Andean plateau, on the order of 2.5 ± 1 km, occurred between ˜ 10.3 and 6.4 Ma. Independent spatial and temporal constraints on paleoelevation and paleoclimate of both the northern and southern plateau are important for understanding the distribution of rapid surface uplift and its relation to climate evolution across the plateau. This study focuses on teeth from modern and extinct mammal taxa (including notoungulates, pyrotheres, and litopterns) spanning ˜ 29 Ma to present, collected from the Altiplano and Eastern Cordillera of Bolivia (16.2°S to 21.4°S), and lowland Brazil. Tooth enamel of large, water-dependent mammals preserves a record of surface water isotopes and the type of plants that animals ingested while their teeth were mineralizing. Previous studies have shown that the δ18O of modern precipitation and surface waters decrease systematically with increasing elevations across the central Andes. Our results from high elevation sites between 3600 and 4100 m show substantially more positive δ18O values for late Oligocene tooth samples compared to < 10 Ma tooth δ18O values. Late Oligocene teeth collected from low elevation sites in southeast Brazil show δ18O values similar (within 2‰) to contemporaneous teeth collected at high elevation in the Eastern Cordillera. This affirms that the Andean plateau was at a very low elevation during the late Oligocene. Late Oligocene teeth from the northern Eastern Cordillera also yield consistent δ13C values of about - 9‰, indicating that the environment was semi-arid at that time. Latitudinal gradients in δ18O values of late Miocene to Pliocene fossil teeth are similar to modern values for large mammals, suggesting that by ˜ 8 Ma in the northern Altiplano and by ˜ 3.6 Ma in the southern Altiplano, both regions had reached high elevation and

  15. 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.

  16. Measurements of temporal and spatial sequences of events in periodic precipitation processes

    NASA Astrophysics Data System (ADS)

    Kai, Shoichi; Müller, Stefan C.; Ross, John

    1982-02-01

    A series of new experiments on Liesegang ring (or band) formation is presented which is concerned with the temporal and spatial evolution of the process of structure formation. We have chosen NH4OH and MgSO4 to form rings of Mg(OH)2 precipitate in a gelatin gel, as well as KI and Pb(NO3)2 for periodic precipitation of PbI2 in an agar gel. A temporal sequence of events during the entire period from the start of a Liesegang experiment in a test tube to the completion of the final ring pattern has been determined at many locations in the tube by visual observations and by measurements of transmitted light, of scattered light, of deflection of the transmitted light beam, and of gravity effects. After diffusion of one electrolyte into the gel medium containing the second electrolyte results in an ion product larger than three times the solubility product, at any and all points in space, we observe the onset of homogeneous nucleation of colloidal particles by a steplike increase of the index of refraction. The colloid concentration and the particle number density at the nucleation site are estimated to be 10-2 mol/l and 1015 to 1016 cm-3, respectively. Nucleation is followed by the growth of colloidal particles which gives rise to distinct light scattering (turbidity). Both nucleation and colloid formation take place in space continuously; the fronts of these phenomena move through the system and obey a simple diffusion law. A substantial time interval after their passage, there arises a localized gradient of the index of refraction at the prospective ring positions which indicates onset of structure formation by means of a focusing mechanism. While the localized gradient becomes more pronounced and narrower in space, the turbidity in the regions on either side of the ring location decreases, which indicates a depletion in colloidal material in the neighboring zones. Eventually, a sharp band of visible precipitate appears, which is clearly separated from the preceding

  17. 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

  18. 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

  19. 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.

  20. 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

  1. 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. PMID:23027960

  2. 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.

  3. 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.

  4. Effects of changes in moisture source and the upstream rainout on stable isotopes in precipitation - a case study in Nanjing, eastern China

    NASA Astrophysics Data System (ADS)

    Tang, Y.; Pang, H.; Zhang, W.; Li, Y.; Wu, S.; Hou, S.

    2015-10-01

    In the Asian monsoon region, variations in the stable isotopic composition of speleothems have often been attributed to the "amount effect". However, an increasing number of studies suggest that the "amount effect" in local precipitation is insignificant or even non-existent. To explore this issue further, we examined the variability of daily stable isotopic composition (δ18O) in precipitation from September 2011 to November 2014 in Nanjing, eastern China. We found that intra-seasonal variations of δ18O during summer were not significantly correlated with local rainfall amount but could be linked to changes in the moisture source location and rainout processes in the source regions. Our findings suggest that the stable isotopes in summer precipitation could signal the location shift of precipitation source regions in the inter-tropical convergence zone (ITCZ) over the course of the monsoon season. As a result, changes in moisture source location and upstream rainout effect should be taken into account when interpreting the stable isotopic composition of speleothems in the Asian monsoon region. In addition, the temperature effect on isotopic variations in non-monsoonal precipitation should also be considered because precipitation in the non-monsoon season accounts for about half of its annual precipitation.

  5. 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.

  6. 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

  7. 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

  8. 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

  9. Ca Isotopes in Evaporite Minerals from Death Valley, California: No Evidence for Non-Biological Fractionation during Precipitation

    NASA Astrophysics Data System (ADS)

    Yang, W.; Depaolo, D. J.; Ingram, B. L.; Owens, T. L.

    2005-12-01

    It has been proposed that Ca isotope fractionation is produced mainly by biological processes, and hence that Ca isotope effects may be a tracer of biological activity in the geologic records of both Earth and Mars. However, Ca isotope fractionation has been produced for rapid precipitation of calcite and aragonite in laboratory experiments, and this fractionation is interpreted to be kinetic% by some investigators and equilibrium by others. Whether the experimental results apply to natural conditions is unknown. To investigate whether there is Ca isotope fractionation in natural inorganic processes, we have measured evaporite minerals precipitated in the Badwater salt pan, Death Valley, California. Death Valley is the hottest and driest desert in North America. Average summer temperatures are 37.8° C with a maximum record of 56.7° C and an annual average of 26° C. Potential evaporation is about 3.8~m/yr, which is 100 times average precipitation. A continuous 200,000-year record of closed-basin calcite and sulfate precipitation is available from a 186-meter sediment core into Badwater Basin. The δ18O and δD variations of fluid inclusion waters in halite are consistent with flooding-dissolution-evaporation cycles (Yang et al., 1995; 1997). The δ18O records of calcite and sulfate reflect the timing and driving forces of late Quaternary paleoclimatic changes (Yang et al., 1998; 2005). The longer-term (96,000, 39,000 and 21,000 years) fluctuations match Milankovitch orbital forcing, and are likely to be global in origin; the shorter-term (14,000 and 8,000 years) fluctuations probably reflect regional climatic and/or hydrologic forcing. Excursions in calcite δ18O are similar to those of δ18O in sulfate in the Death Valley core, and mimic those in marine carbonate (SPECMAP) and polar ice in the Summit ice core (GRIP), Greenland. Preliminary study of Ca isotopes in the calcite and sulfate minerals from the Badwater saline sediment core shows no significant

  10. 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.

  11. 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.

  12. Spatial distribution of precipitation annual cycles over South Africa in 10 CORDEX regional climate model present-day simulations

    NASA Astrophysics Data System (ADS)

    Favre, Alice; Philippon, Nathalie; Pohl, Benjamin; Kalognomou, Evangelia-Anna; Lennard, Christopher; Hewitson, Bruce; Nikulin, Grigori; Dosio, Alessandro; Panitz, Hans-Juergen; Cerezo-Mota, Ruth

    2016-03-01

    This study presents an evaluation of the ability of 10 regional climate models (RCMs) participating in the COordinated Regional climate Downscaling Experiment-Africa to reproduce the present-day spatial distribution of annual cycles of precipitation over the South African region and its borders. As found in previous studies, annual mean precipitation is quasi-systematically overestimated by the RCMs over a large part of southern Africa south of about 20°S and more strongly over South Africa. The spatial analysis of precipitation over the studied region shows that in most models the distribution of biases appears to be linked to orography. Wet biases are quasi-systematic in regions with higher elevation with inversely neutral to dry biases particularly in the coastal fringes. This spatial pattern of biases is particularly obvious during summer and specifically at the beginning of the rainy season (November and December) when the wet biases are found to be the strongest across all models. Applying a k-means algorithm, a classification of annual cycles is performed using observed precipitation data, and is compared with those derived from modeled data. It is found that the in-homogeneity of the spatial and temporal distribution of biases tends to impact the modeled seasonality of precipitation. Generally, the pattern of rainfall seasonality in the ensemble mean of the 10 RCMs tends to be shifted to the southwest. This spatial shift is mainly linked to a strong overestimation of convective precipitation at the beginning of the rainy season over the plateau inducing an early annual peak and to an underestimation of stratiform rainfall in winter and spring over southwestern South Africa.

  13. 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. PMID:26158480

  14. 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.

  15. 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.

  16. Spatial analysis of extreme precipitation deficit as an index for atmospheric drought in Belgium

    NASA Astrophysics Data System (ADS)

    Zamani, Sepideh; Van De Vyver, Hans; Gobin, Anne

    2014-05-01

    The growing concern among the climate scientists is that the frequency of weather extremes will increase as a result of climate change. European society, for example, is particularly vulnerable to changes in the frequency and intensity of extreme events such as heat waves, heavy precipitation, droughts, and wind storms, as seen in recent years [1,2]. A more than 50% of the land is occupied by managed ecosystem (agriculture, forestry) in Belgium. Moreover, among the many extreme weather conditions, drought counts to have a substantial impact on the agriculture and ecosystem of the affected region, because its most immediate consequence is a fall in crop production. Besides the technological advances, a reliable estimation of weather conditions plays a crucial role in improving the agricultural productivity. The above mentioned reasons provide a strong motivation for a research on the drought and its impacts on the economical and agricultural aspects in Belgium. The main purpose of the presented work is to map atmospheric drought Return-Levels (RL), as first insight for agricultural drought, employing spatial modelling approaches. The likelihood of future drought is studied on the basis of precipitation deficit indices for four vegetation types: water (W), grass (G), deciduous (D) and coniferous forests (C) is considered. Extreme Value Theory (EVT) [3,4,5] as a branch of probability and statistics, is dedicated to characterize the behaviour of extreme observations. The tail behaviour of the EVT distributions provide important features about return levels. EVT distributions are applicable in many study areas such as: hydrology, environmental research and meteorology, insurance and finance. Spatial Generalized Extreme Value (GEV) distributions, as a branch of EVT, are applied to annual maxima of drought at 13 hydro-meteorological stations across Belgium. Superiority of the spatial GEV model is that a region can be modelled merging the individual time series of

  17. 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

  18. Temporal and spatial variability of temperature and precipitation over East Africa from 1951 to 2010

    NASA Astrophysics Data System (ADS)

    Ongoma, Victor; Chen, Haishan

    2016-05-01

    This study presents temporal and spatial changes in temperature and precipitation over East Africa (EA) from 1951 to 2010. The study utilized monthly Climate Research Unit (CRU) rainfall and temperature datasets, and Global Precipitation Climate Centre (GPCC) rainfall datasets. Sequential Mann-Kendall test statistic was used for trend analysis. The CRU data performs better than GPCC data in reproducing EA annual rainfall cycle. Overall decrease and increase in rainfall and temperature trends were observed, respectively, with the reduction in the March-May rainfall being significant. The highest rate of change in annual rainfall was experienced in the 1960s at -21.76 mm/year. Although there has been increase in temperature from the late 1960s to date, sudden change in its trend change happened in 1994. The increase in temperature reached a significant level in the year 1992. The highest warming rate of 0.05 °C/year was observed in the 1990s. The highest drying rate was recorded in the 1960s at -21.76 mm/year. There was an observed change in rainfall trend in the year 1953 and about four times in 1980, although the changes are insignificant throughout the study period except for 1963 when a positive significant change occurred at 5 % significance level. The highest amount of rainfall was recorded in the 1960s. Generally, positive rainfall and temperature anomalies are observed over the northern sector of the study area and opposite conditions are noted in the southern sector. The results of this study provide a reliable basis for future climate monitoring, as well as investigating extreme weather phenomena in EA.

  19. On the relationship between open cellular convective cloud patterns and the spatial distribution of precipitation

    NASA Astrophysics Data System (ADS)

    Yamaguchi, T.; Feingold, G.

    2014-10-01

    Precipitation is thought to be a necessary but insufficient condition for the transformation of stratocumulus-topped closed cellular convection to open cellular cumuliform convection. Here we test the hypothesis that the spatial distribution of precipitation is a key element of the closed-to-open cell transition. A series of idealized 3-dimensional simulations are conducted to evaluate the dependency of the transformation on the areal coverage of rain, and to explore the role of interactions between multiple rainy areas in the formation of the open cells. When rain is restricted to a small area, even substantial rain (order few mm day-1) does not result in a transition. With increasing areal coverage of the rain, the transition becomes possible provided that the rain rate is sufficiently large. When multiple small rain regions interact with each other, the transition occurs and spreads over a wider area, provided that the distance between the rain regions is short. When the distance between the rain areas is large, the transition eventually occurs, albeit slowly. For much longer distances between rain regions the system is anticipated to remain in a closed-cell state. These results suggest a connection to the recently hypothesized remote control of open-cell formation. Finally it is shown that phase trajectories of the mean and coefficient of variation of vertically integrated variables such as liquid water path align on one trajectory. This could be used as a diagnostic tool for global analyses of the statistics of closed- and open-cell occurrence and transitions between them.

  20. 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

  1. [Comparison on the methods for spatial interpolation of the annual average precipitation in the Loess Plateau region].

    PubMed

    Yu, Yang; Wei, Wei; Chen, Li-ding; Yang, Lei; Zhang, Han-dan

    2015-04-01

    Based on 57 years (1957-2013) daily precipitation datasets of the 85 meteorological stations in the Loess Plateau region, different spatial interpolation methods, including ordinary kriging (OK), inverse distance weighting (IDW) and radial-based function (RBF), were conducted to analyze the spatial variation of annual average precipitation regionally. Meanwhile, the mean absolute error (MAE), the root mean square error (RMSE), the accuracy (AC) and the Pearson correlation coefficient (R) were compared among the interpolation results in order to quantify the effects of different interpolation methods on spatial variation of the annual average precipitation. The results showed that the Moran's I index was 0.67 for the 57 years annual average precipitation in the Loess Plateau region. Meteorological stations exhibited strong spatial correlation. The validation results of the 63 training stations and 22 test stations indicated that there were significant correlations between the training and test values among different interpolation methods. However, the RMSE (IDW = 51.49, RBF = 43.79) and MAE (IDW = 38.98, RBF = 34.61) of the IDW and the RBF showed higher values than the OK. In addition, the comparison of the four semi-variagram models (Circular, Spherical, Exponential and Gaussian) for the OK indicated that the circular model had the lowest MAE (32.34) and the highest accuracy (0.976), while the MAE of the exponential model was the highest (33.24). In conclusion, comparing the validation between the training data and test results of the different spatial interpolation methods, the circular model of the OK method was the best one for obtaining accurate spatial interpolation of annual average precipitation in the Loess Plateau region. PMID:26259439

  2. Spatial interpolation of precipitation indexes in Sierra Nevada (Spain): comparing the performance of some interpolation methods

    NASA Astrophysics Data System (ADS)

    Pereira, Paulo; Oliva, Marc; Misiune, Ieva

    2015-08-01

    The objective of this paper is to examine the spatial distribution of several precipitation indexes in Sierra Nevada, Spain: mean annual number of wet days (R ≥ 1 mm), mean annual number of heavy rainy days (R ≥ 10 mm) and mean annual number of very heavy precipitation days (R ≥ 20 mm) and test the performance of several interpolation methods using these variables. In total, 17 univariate and multivariate methods were tested. A set of 36 metereological stations distributed in Sierra Nevada and neighbouring areas was analysed in this study. The original data did not followed the normal distribution; thus, a logarithm was applied to data meet normality purposes. Interpolator's performance was assessed using the root mean square error generated from cross-validation. The results showed that the mean annual R ≥ 10 mm and R ≥ 20 mm have a higher variability than R ≥ 1 mm. While the elevation and longitude did not show a significant correlation with the studied indexes, the latitude (i.e. distance to the sea) showed a significant negative correlation. The regressions carried out confirmed that elevation was the covariate with higher capacity to explain the variability of the indexes. The incorporation of elevation and longitude slightly increased the explanation capacity of the models. The data of LogR ≥ 1 mm, LogR ≥ 10 mm and LogR ≥ 20 mm displayed a clustered pattern, especially the last two indexes that also showed a strong spatial dependency attributed to the effects of local topography, slope, aspect and valley orientation. The best fitted variogram model to LogR ≥ 1 mm was the linear one while for the LogR ≥ 10 mm and LogR ≥ 20 mm, the Gaussian was the most appropriate. The best interpolator for LogR ≥ 1 mm was the local polinomyal with the power of 1, whereas for LogR ≥ 10 mm and LogR ≥ 20 mm, regression kriging (ROK) using as auxiliary variables the elevation, latitude and longitude was the most accurate. ROK methods significantly

  3. Evaluation of Fuzzy-Logic Framework for Spatial Statistics Preserving Methods for Estimation of Missing Precipitation Data

    NASA Astrophysics Data System (ADS)

    El Sharif, H.; Teegavarapu, R. S.

    2012-12-01

    Spatial interpolation methods used for estimation of missing precipitation data at a site seldom check for their ability to preserve site and regional statistics. Such statistics are primarily defined by spatial correlations and other site-to-site statistics in a region. Preservation of site and regional statistics represents a means of assessing the validity of missing precipitation estimates at a site. This study evaluates the efficacy of a fuzzy-logic methodology for infilling missing historical daily precipitation data in preserving site and regional statistics. Rain gauge sites in the state of Kentucky, USA, are used as a case study for evaluation of this newly proposed method in comparison to traditional data infilling techniques. Several error and performance measures will be used to evaluate the methods and trade-offs in accuracy of estimation and preservation of site and regional statistics.

  4. Decreasing spatial variability in precipitation extremes in southwestern China and the local/large-scale influencing factors

    NASA Astrophysics Data System (ADS)

    Liu, Meixian; Xu, Xianli; Sun, Alex

    2015-07-01

    Climate extremes can cause devastating damage to human society and ecosystems. Recent studies have drawn many conclusions about trends in climate extremes, but few have focused on quantitative analysis of their spatial variability and underlying mechanisms. By using the techniques of overlapping moving windows, the Mann-Kendall trend test, correlation, and stepwise regression, this study examined the spatial-temporal variation of precipitation extremes and investigated the potential key factors influencing this variation in southwestern (SW) China, a globally important biodiversity hot spot and climate-sensitive region. Results showed that the changing trends of precipitation extremes were not spatially uniform, but the spatial variability of these precipitation extremes decreased from 1959 to 2012. Further analysis found that atmospheric circulations rather than local factors (land cover, topographic conditions, etc.) were the main cause of such precipitation extremes. This study suggests that droughts or floods may become more homogenously widespread throughout SW China. Hence, region-wide assessments and coordination are needed to help mitigate the economic and ecological impacts.

  5. El Niño-Southern Oscillation influence on winter maximum daily precipitation in California in a spatial model

    NASA Astrophysics Data System (ADS)

    Shang, Hongwei; Yan, Jun; Zhang, Xuebin

    2011-11-01

    Recent studies have found that the El Niño-Southern Oscillation (ENSO) has statistically significant influences on extreme precipitation. A limitation of most existing work is that a separate generalized extreme value (GEV) distribution is fitted for each individual site. Such models cannot address important questions that involve events jointly defined across multiple sites; for instance, what is the probability that the 50 year return levels of three sites in the vicinity of a city occur in the same season? With the latest statistical methodology for spatial extremes, we fit max-stable process models to winter maximum daily precipitation of 192 sites in California over 55 years. A composite likelihood approach is used since the full likelihood is unavailable either analytically or numerically. In addition to latitude, longitude, and elevation, the Southern Oscillation Index (SOI) is incorporated into the parameters of the marginal GEV models. We find that, in a spatial context, the ENSO has a significant influence on the extreme precipitation in California by shifting the location parameter of the GEV distributions, with higher values of the SOI corresponding to lower maximum winter daily precipitation. The joint spatial model is used to assess risks concerning joint extremal events at network of sites with spatial dependence properly accounted for. The probability of extremal events occurring at multiple sites in the same season is found to be much higher than what would be expected under the independence assumption.

  6. 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

  7. Comparison of radar and gauge precipitation data in watershed models across varying spatial and temporal scales

    EPA Science Inventory

    Precipitation is a key control on watershed hydrologic modelling output, with errors in rainfall propagating through subsequent stages of water quantity and quality analysis. Most watershed models incorporate precipitation data from rain gauges; higher-resolution data sources are...

  8. GIS based Spatial Precipitation Estimation using Next Generation Radar and Raingauge Data

    SciTech Connect

    Zhang, Xuesong; Srinivasan, Ragahvan

    2010-01-01

    Precipitation is one important input variable for land surface hydrologic and ecological models. Next Generation Radar (NEXRAD) can provide precipitation products that cover most of the conterminous United States at high resolution (approximately 4km×4km).

  9. The Spatial and Temporal Heterogeneity of Precipitation and Aerosol-Cloud Radiative Forcing Uncertainty in Climatically Important Regions

    NASA Astrophysics Data System (ADS)

    Regayre, L.; Pringle, K.; Lee, L.; Booth, B.; Browse, J.; Mann, G.; Woodhouse, M. T.; Reddington, C.; Carslaw, K. S.; Rap, A.

    2015-12-01

    Aerosol-cloud radiative forcing and precipitation sensitivities are quantified within climatically important regions, where surface temperatures and moisture availability are thought to influence large-scale climatic effects. The sensitivity of precipitation and the balance of incoming and outgoing radiation to uncertain historical aerosol emission fluxes and aerosol-cloud parametrisations are quantified and their climatic importance considered. The predictability of monsoon onset and intensity, position of the inter-tropical convergence zone, tropical storm frequency and intensity, heat transport to the Arctic and changes in the mode of the El Niño Southern Oscillation are all limited by the parametric uncertainties examined here. Precipitation and aerosol-cloud radiative forcing sensitivities are found to be both spatially and temporally heterogeneous. Statistical analysis highlights aspects of aerosol-climate research and model development that should be prioritised in order to reduce the impact of uncertainty in regional precipitation and aerosol-cloud forcing on near-term climate projections.

  10. 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)

  11. Structure of the spatial periphery of the isotopes 9,11Li

    NASA Astrophysics Data System (ADS)

    Galanina, L. I.; Zelenskaya, N. S.

    2015-07-01

    The cross sections for the ( t, p) reactions on the lithium isotopes 9,11Li 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 9,11Li and the spatial structure of their neutron periphery. It is shown that the 9Li nucleus has virtually no neutron halo. The 11Li 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. 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

  13. 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.

  14. 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.

    2016-01-01

    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.

  15. 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

  16. Developing an entropy-based model of spatial information estimation and its application in the design of precipitation gauge networks

    NASA Astrophysics Data System (ADS)

    Su, Ho-Ting; You, Gene Jiing-Yun

    2014-11-01

    This study proposed a spatial information estimation model for the analysis of precipitation gauge networks, to improve on previous methods based on information theory. The proposed model employs a two-dimensional transinformation-distance (T-D) relationship in conjunction with multivariate information approximation to estimate transinformation to ungauged locations from existing stations, while taking into consideration the influence of multiple stations and anisotropy. The proposed model is used to evaluate the spatial distribution of precipitation data and the characteristics of information transfer, which are then applied in a spatial optimization algorithm for the selection of additional station locations. This framework was implemented to investigate temporal and spatial patterns in information content in the Shihmen Reservoir watershed. The results demonstrate obvious anisotropy associated with the delivery of information. By comparing different cases, it was determined that the efficiency of information delivery dominates the spatial distribution of the information content, such that eccentricity is merely supplemental. Efficiency in information delivery is also heavily influenced by temporal scale. For data covering long intervals (monthly and annual), efficiency in the delivery of information is relatively high, while the uncertainty or heterogeneity of hourly or daily time series produces low spatial correlations due to the inefficient delivery of information. The proposed spatial optimization algorithm confirmed that the optimal location for new stations lies close to the center of low information zones. Additional stations could improve information content considerably; however, the margin of improvement decreases with the number of stations.

  17. Spatial heterogeneity of uranium isotope variations in a Phanerozoic, epicontintental black shale (Hushpuckney Shale, Swope Formation)

    NASA Astrophysics Data System (ADS)

    Herrmann, A. D.; Gordon, G. W.; Romaniello, S. J.; Algeo, T. J.; Anbar, A. D.

    2012-12-01

    capturing changes in global seawater. We find that the two sections show the same overall trend: light values at the base of the black shale, a change to heavy values in the middle part, and a change back to lighter values at the top of the black shale interval. However, the magnitude and rate of the isotopic variations is different. The isotopic composition of lower part of the black shale in the SE Kansas core is fairly light (~ -0.5 ‰), then rapidly changes to ~ 0.6‰ over the next 20 cm, and then swiftly changes back to ~ -0.15‰ in the next 20 cm. In contrast, the lower part of the black shale in the more shoreward section in Iowa has an isotopic composition of ~0.0‰. Over the next 40 cm the isotopic composition gradually rises to ~0.4 ‰ and then gradually changes to ~-0.15‰ over the next 40 cm. Our results indicate that the complex paleoceanographic conditions of epicontintental seas can lead to spatial gradients in physical and chemical properties that cause differences in the uranium isotopic composition of black shales within the depositional basin. This hampers the ability to precisely reconstruct global redox changes from one section alone. It is not clear yet what environmental conditions lead to the spatial heterogeneity within the LPMS, but ongoing geochemical and modeling work is aimed at understanding the controlling factors.

  18. The hydrogen and oxygen isotopic composition of precipitation, evaporated mine water, and river water in Montana, USA

    NASA Astrophysics Data System (ADS)

    Gammons, Christopher H.; Poulson, Simon R.; Pellicori, Damon A.; Reed, Pamela J.; Roesler, Amber J.; Petrescu, Eugene M.

    2006-08-01

    SummaryThe isotopic composition of 42 samples of rain and snow collected in 2004 were used to construct a local meteoric water line (LMWL) for Butte, Montana. The derived equation (δD = 7.31δ 18O - 7.5, r2 = 0.987), represents one of the first published LMWLs based on direct precipitation for any location in the northern Rocky Mountains. Samples of underground and surface mine waters in Butte, including the Berkeley pit-lake and a nearby tailings pond, define a linear trend with a much lower slope and intercept than the LMWL (δD = 5.00δ 18O - 49.5, r2 = 0.991), consistent with non-equilibrium evaporation at an average relative humidity of roughly 65%. Detailed evaporation calculations are presented which indicate that the shallow Berkeley pit-lake was approximately 25% evaporated in October, 2003, whereas the surface of the tailings pond was at least 50% evaporated. The intersection of the LMWL and mine water evaporation trend was used to calculate the average composition of recharge water to the flooded mine complex (δD = -139‰, δ 18O = -18.0‰). These values are considerably lighter than the weighted total of precipitation for the 2004 calendar year (δD = -118‰, δ 18O = -15.3‰), which is partly explained by the unusually low snowfall that Montana experienced in 2004. Based on this study, the LMWL recently proposed by Kendall and Coplen (2001) [Kendall, C., Coplen, T.B., 2001. Distribution of oxygen-18 and deuterium in river waters across the United States, Hydrological Processes 15, 1363-1393] from regression of isotopic data from a number of Montana rivers is more accurately interpreted as an evaporation line. Isotopic trends based on river data should be treated with caution, particularly in a semi-arid region such as Montana where rivers are often influenced by dams and irrigation withdrawals.

  19. 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.

  20. Spatial and temporal variability of temperature and precipitation over Iraq and its relation with global sea surface temperature

    NASA Astrophysics Data System (ADS)

    Alkhalidi, Jasim; Stefan, Sabina; Dima, Mihai

    2016-04-01

    In this study we have examined the spatial and temporal variability of mean temperature (0C) and precipitation (mm) in winter (DJF) and spring (MAM) in Iraq. The data used were recorded at 12 stations for temperature and 18stations for precipitation over the period 1981-2010. An empirical orthogonal function (EOFs) and principal component (PCs) analysis were employed to characterize the spatial variability of the climatological parameters. The first EOF of temperature has the most variance (80%) and it is monopolar. This means it is related with large scale patterns. The first EOF of precipitation has variance (70%) lower than that of EOF1 for temperature, because the precipitation is a local phenomenon. The analysis of PCS for temperature showed different trends for the different time intervals. In addition, the relation between the global sea surface temperature (SST) and the temperature and precipitation PCs was analyzed. The results derived through correlations maps indicate links between Iraq climate and El Nino southern oscillation (ENSO) and Atlantic multidecadal oscillation (AMO), large scale patterns.

  1. Spatial-temporal variation of precipitation concentration and structure in the Wei River Basin, China

    NASA Astrophysics Data System (ADS)

    Huang, Shengzhi; Huang, Qiang; Chen, Yutong; Xing, Li; Leng, Guoyong

    2015-05-01

    It is of significant importance to investigate precipitation structure and precipitation concentration due to their great impact on droughts, floods, soil erosion, as well as water resources management. A complete investigation of precipitation structure and its distribution pattern in the Wei River Basin was performed based on recorded daily precipitation data in this study. Two indicators were used: concentration index based on daily precipitation (CID), to assess the distribution of rainy days, and concentration index based on monthly precipitation (CIM), to estimate the seasonality of the precipitation. Besides, the modified Mann-Kendall trend test method was employed to capture the variation trends of CID and CIM. The results indicate that: (1) the 1-3-day events are the predominant precipitation events in terms of the occurrence and fractional contribution; (2) the obvious differences in the CID of various areas are found in the Wei River Basin, and the high CID values mainly concentrate in the northern basin, conversely, the southern basin has a relatively low CID value; (3) high CIM values are primarily in the western and northern basin, reflecting a remarkable seasonality of precipitation in these regions; and (4) all of the stations show a downward trend of CIM, which indicates that the monthly precipitation distribution tends to be more uniform.

  2. Spatial-temporal variation of precipitation concentration and structure in the Wei River Basin, China

    NASA Astrophysics Data System (ADS)

    Huang, Shengzhi; Huang, Qiang; Chen, Yutong; Xing, Li; Leng, Guoyong

    2016-07-01

    It is of significant importance to investigate precipitation structure and precipitation concentration due to their great impact on droughts, floods, soil erosion, as well as water resources management. A complete investigation of precipitation structure and its distribution pattern in the Wei River Basin was performed based on recorded daily precipitation data in this study. Two indicators were used: concentration index based on daily precipitation (CID), to assess the distribution of rainy days, and concentration index based on monthly precipitation (CIM), to estimate the seasonality of the precipitation. Besides, the modified Mann-Kendall trend test method was employed to capture the variation trends of CID and CIM. The results indicate that: (1) the 1-3-day events are the predominant precipitation events in terms of the occurrence and fractional contribution; (2) the obvious differences in the CID of various areas are found in the Wei River Basin, and the high CID values mainly concentrate in the northern basin, conversely, the southern basin has a relatively low CID value; (3) high CIM values are primarily in the western and northern basin, reflecting a remarkable seasonality of precipitation in these regions; and (4) all of the stations show a downward trend of CIM, which indicates that the monthly precipitation distribution tends to be more uniform.

  3. Spatial interpolation of precipitation in a dense gauge network for monsoon storm events in the southwestern United States

    NASA Astrophysics Data System (ADS)

    Garcia, Matthew; Peters-Lidard, Christa D.; Goodrich, David C.

    2008-05-01

    Inaccuracy in spatially distributed precipitation fields can contribute significantly to the uncertainty of hydrological states and fluxes estimated from land surface models. This paper examines the results of selected interpolation methods for both convective and mixed/stratiform events that occurred during the North American monsoon season over a dense gauge network at the U.S. Department of Agriculture Agricultural Research Service Walnut Gulch Experimental Watershed in the southwestern United States. The spatial coefficient of variation for the precipitation field is employed as an indicator of event morphology, and a gauge clustering factor CF is formulated as a new, scale-independent measure of network organization. We consider that CF < 0 (a more distributed gauge network) will produce interpolation errors by reduced resolution of the precipitation field and that CF > 0 (clustering in the gauge network) will produce errors because of reduced areal representation of the precipitation field. Spatial interpolation is performed using both inverse-distance-weighted (IDW) and multiquadric-biharmonic (MQB) methods. We employ ensembles of randomly selected network subsets for the statistical evaluation of interpolation errors in comparison with the observed precipitation. The magnitude of interpolation errors and differences in accuracy between interpolation methods depend on both the density and the geometrical organization of the gauge network. Generally, MQB methods outperform IDW methods in terms of interpolation accuracy under all conditions, but it is found that the order of the IDW method is important to the results and may, under some conditions, be just as accurate as the MQB method. In almost all results it is demonstrated that the inverse-distance-squared method for spatial interpolation, commonly employed in operational analyses and for engineering assessments, is inferior to the ID-cubed method, which is also more computationally efficient than the MQB

  4. Examine the potential of spatial downscaling of TRMM precipitation with environmental variables: An evaluation for the Ohio River Basin

    NASA Astrophysics Data System (ADS)

    Yoon, Y.; Beighley, E., II

    2014-12-01

    Accurately quantifying precipitation in both space and time is a central challenge in hydrologic modelling. Data products from the Tropical Rainfall Measuring Mission (TRMM) are commonly used as precipitation forcings in many models. TRMM provides 3-hr precipitation estimates at a near-global scale (-50◦ S to 50◦N) with a 0.25 degree spatial resolution. However, when applied in regional scale hydrologic models, the spatial resolution of the TRMM is often too coarse limiting our ability to simulate relevant hydrologic processes.This study focuses on addressing the science question: can we improve the spatial resolution of the TRMM using statistical downscaling with environmental variables derived from finer scale remote sensing data? The goal is to downscale the TRMM resolution from 0.25 degrees (25 km) to 0.05 degrees (about 5 km). In our approach, we first identify environmental variables (i.e., vegetation cover, topography, and temperature) that are related to the formation of or result from precipitation by exploring their statistical relationships with TRMM precipitation at varying temporal scales (i.e., daily, monthly, and yearly) using an analysis of variance in multiple regression. The MODIS vegetation index, MODIS leaf area index, and SPOT vegetation are examined as a proxy for vegetation. To represent the topography, the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) is used. MODIS land surface temperature are used for temperature. Second, we characterize a residual component, which cannot be explained by the statistical relationship between precipitation and environmental variables, to improve the accuracy of the downscaling results. For example, recent studies have shown that approximately 30-40% of the variability in annual precipitation cannot be explained by vegetation and elevation characteristics. According for this unexplained variability in statistical downscaling methods is a significant challenge. Here, we use a data

  5. Proxies of Tropical Cyclone Isotope Spikes in Precipitation: Landfall Site Selection

    NASA Astrophysics Data System (ADS)

    Lawrence, J. R.; Maddocks, R.

    2011-12-01

    The human experience of climate change is not one of gradual changes in seasonal or yearly changes in temperature or rainfall. Despite that most paleoclimatic reconstructions attempt to provide just such information. Humans experience climate change on much shorter time scales. We remember hurricanes, weeks of drought or overwhelming rainy periods. Tropical cyclones produce very low isotope ratios in both rainfall and in atmospheric water vapor. Thus, climate proxies that potentially record these low isotope ratios offer the most concrete record of climate change to which humans can relate. The oxygen isotopic composition of tropical cyclone rainfall has the potential to be recorded in fresh water carbonate fossil material, cave deposits and corals. The hydrogen isotopic composition of tropical cyclone rainfall has the potential to be recorded in tree ring cellulose and organic matter in fresh water bodies. The Class of carbonate organisms known as Ostracoda form their carapaces very rapidly. Thus fresh water ephemeral ponds in the subtropics are ideal locations for isotopic studies because they commonly are totally dry when tropical cyclones make landfall. The other proxies suffer primarily from a dilution effect. The water from tropical cyclones is mixed with pre-existing water. In cave deposits tropical cyclone rains mix with soil and ground waters. In the near shore coral environment the rain mixes with seawater. For tree rings there are three sources of water: soil water, atmospheric water vapor that exchanges with leaf water and tropical cyclone rain. In lakes because of their large size rainfall runoff mixes with ground water and preexisting water in the lake. A region that shows considerable promise is Texas / Northeast Mexico. In a study of surface waters that developed from the passage of Tropical Storm Allison (2001) in SE Texas both the pond water and Ostracoda that bloomed recorded the low oxygen isotope signal of that storm (Lawrence et al, 2008). In

  6. The Dynamics of Halite Precipitation in the Dead Sea: Seasonal and Spatial Variations

    NASA Astrophysics Data System (ADS)

    Lensky, Nadav G.; Sirota, Ido; Arnon, Ali

    2016-04-01

    The Dead Sea is a deep hypersaline terminal lake that actively precipitates halite as a response to the negative water balance of the lake (evaporation > inflows). From mass balance consideration, a uniform ~3 m thick halite sequence is expected to cover the lake floor following the ~30 m level drop; however such a massive layer does not exist in the shallow water. In this talk we present new insights on the dynamics of halite precipitation and dissolution in a seasonally stratified lake, based on field observations. In situ monthly observations include the depth profile of the following: (i) halite precipitation rate, (ii) temperature, (iii) salinity, (iv) halite saturation, and (v) underwater photography of the sea floor and the water column - documentation of active halite precipitation/dissolution. We found a clear relation between the thermohaline stratification of the water column and halite precipitation/dissolution. The epilimnion experiences seasonal dissolution/precipitation cycle, while the hypolimnion continuously precipitates halite. We discuss the seasonal variations of the atmospheric forcing - the heat and water fluxes, and the response of the lake - thermohaline stratification and the precipitation/dissolution of halite along the water column and lake floor. 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 are also discussed.

  7. The role of precipitation type, intensity, and spatial distribution in source water quality after wildfire

    USGS Publications Warehouse

    Murphy, Sheila F.; Writer, Jeffrey H.; McCleskey, R. Blaine; Martin, Deborah A.

    2015-01-01

    Storms following wildfires are known to impair drinking water supplies in the southwestern United States, yet our understanding of the role of precipitation in post-wildfire water quality is far from complete. We quantitatively assessed water-quality impacts of different hydrologic events in the Colorado Front Range and found that for a three-year period, substantial hydrologic and geochemical responses downstream of a burned area were primarily driven by convective storms with a 30 min rainfall intensity >10 mm h−1. These storms, which typically occur several times each year in July–September, are often small in area, short-lived, and highly variable in intensity and geographic distribution. Thus, a rain gage network with high temporal resolution and spatial density, together with high-resolution stream sampling, are required to adequately characterize post-wildfire responses. We measured total suspended sediment, dissolved organic carbon (DOC), nitrate, and manganese concentrations that were 10–156 times higher downstream of a burned area compared to upstream during relatively common (50% annual exceedance probability) rainstorms, and water quality was sufficiently impaired to pose water-treatment concerns. Short-term water-quality impairment was driven primarily by increased surface runoff during higher intensity convective storms that caused erosion in the burned area and transport of sediment and chemical constituents to streams. Annual sediment yields downstream of the burned area were controlled by storm events and subsequent remobilization, whereas DOC yields were closely linked to annual runoff and thus were more dependent on interannual variation in spring runoff. Nitrate yields were highest in the third year post-wildfire. Results from this study quantitatively demonstrate that water quality can be altered for several years after wildfire. Because the southwestern US is prone to wildfires and high-intensity rain storms, the role of storms in post

  8. The role of precipitation type, intensity, and spatial distribution in source water quality after wildfire

    NASA Astrophysics Data System (ADS)

    Murphy, Sheila F.; Writer, Jeffrey H.; Blaine McCleskey, R.; Martin, Deborah A.

    2015-08-01

    Storms following wildfires are known to impair drinking water supplies in the southwestern United States, yet our understanding of the role of precipitation in post-wildfire water quality is far from complete. We quantitatively assessed water-quality impacts of different hydrologic events in the Colorado Front Range and found that for a three-year period, substantial hydrologic and geochemical responses downstream of a burned area were primarily driven by convective storms with a 30 min rainfall intensity >10 mm h-1. These storms, which typically occur several times each year in July-September, are often small in area, short-lived, and highly variable in intensity and geographic distribution. Thus, a rain gage network with high temporal resolution and spatial density, together with high-resolution stream sampling, are required to adequately characterize post-wildfire responses. We measured total suspended sediment, dissolved organic carbon (DOC), nitrate, and manganese concentrations that were 10-156 times higher downstream of a burned area compared to upstream during relatively common (50% annual exceedance probability) rainstorms, and water quality was sufficiently impaired to pose water-treatment concerns. Short-term water-quality impairment was driven primarily by increased surface runoff during higher intensity convective storms that caused erosion in the burned area and transport of sediment and chemical constituents to streams. Annual sediment yields downstream of the burned area were controlled by storm events and subsequent remobilization, whereas DOC yields were closely linked to annual runoff and thus were more dependent on interannual variation in spring runoff. Nitrate yields were highest in the third year post-wildfire. Results from this study quantitatively demonstrate that water quality can be altered for several years after wildfire. Because the southwestern US is prone to wildfires and high-intensity rain storms, the role of storms in post

  9. Pacific/North American teleconnection controls on precipitation isotope ratios across the contiguous United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Large-scale climate teleconnections such as the Pacific/North American (PNA) pattern stronglyinfluence atmospheric processes and continental climate. Here we show that precipitation deltaO-18 values in the contiguous United States are correlated with an index of the PNA pattern. The deltaO-18/PNA re...

  10. On the Seasonal Variation of Stable Isotopic Composition of Precipitation over Asian Monsoon Region

    NASA Technical Reports Server (NTRS)

    Lee, Jung-Eun; Fung, Inez; Risi, Camille; Worden, John; Scheepmaker, Remco; Frankenberg, Christian

    2011-01-01

    Precipitation is the excess water the atm cannot hold delta18Op records the life history of water: ET source of vapor. variations of delta18Ov during transport. T and delta18Ov at condensation. Post-condensation exchange with vapor. Models relatively mature to aid interpretation of paleoclimate proxies.

  11. Spatial and Temporal Energy Characterization of Precipitating Electrons for the January 10th, 1997 Magnetic Cloud Event

    NASA Technical Reports Server (NTRS)

    Spann, J. F., Jr.; Germany, G. A.; Brittnacher, M. J.; Parks, G. K.; Elsen, R.

    1997-01-01

    The January 10-11, 1997 magnetic cloud event provided a rare opportunity to study auroral energy deposition under varying but intense IMF conditions. The Wind spacecraft located about 100 RE upstream monitored the IMF and plasma parameters during the passing of the cloud. The Polar Ultraviolet Imager (UVI) observed the aurora[ precipitation during the first encounter of the cloud with Earth's magnetosphere and during several subsequent substorm events. The UVI has the unique capability of measuring the energy flux and characteristic energy of the precipitating electrons through the use of narrow band filters that distinguish short and long wavelength molecular nitrogen emissions. The spatial and temporal characteristics of the precipitating electron energy will be discussed beginning with the inception of the event at the Earth early January 1 Oth and continuing through the subsidence of auroral activity on January 11th.

  12. Atom probe microscopy of three-dimensional distribution of silicon isotopes in {sup 28}Si/{sup 30}Si isotope superlattices with sub-nanometer spatial resolution

    SciTech Connect

    Shimizu, Yasuo; Kawamura, Yoko; Uematsu, Masashi; Itoh, Kohei M.; Tomita, Mitsuhiro; Sasaki, Mikio; Uchida, Hiroshi; Takahashi, Mamoru

    2009-10-01

    Laser-assisted atom probe microscopy of 2 nm period {sup 28}Si/{sup 30}Si isotope superlattices (SLs) is reported. Three-dimensional distributions of {sup 28}Si and {sup 30}Si stable isotopes are obtained with sub-nanometer spatial resolution. The depth resolution of the present atom probe analysis is much higher than that of secondary ion mass spectrometry (SIMS) even when SIMS is performed with a great care to reduce the artifact due to atomic mixing. Outlook of Si isotope SLs as ideal depth scales for SIMS and three-dimensional position standards for atom probe microscopy is discussed.

  13. The influence of topographic co-variables on the spatial variability of precipitation over small regions of complex terrain

    NASA Astrophysics Data System (ADS)

    Diodato, Nazzareno

    2005-03-01

    Precipitation variability results from atmospheric circulation and complex site-specific bio-geoclimatic characteristics; therefore, climatic variables are expected to be correlated in a scale-dependent way. This paper studies the influence of topographic co-variables on the spatial variability of precipitation over small regions of complex terrain. For this purpose, the mutual benefits of an integrated geographic information system (GIS) and a geostatistics approach was used for spatial precipitation interpolation from rainfall observations measured at 51 climatic stations in a mountainous region of southern Italy (Benevento province). As no single method is optimal for all regions, it is important to compare the results obtained using alternative methods applied to the same data set. Therefore, besides ordinary kriging examination, two auxiliary variables were added for ordinary co-kriging of annual and seasonal precipitation: terrain elevation data and a topographic index. Cross-validation indicated that the ordinary kriging yielded the largest prediction errors. The smallest prediction errors were produced by a multivariate geostatistical method. However, the results favour the ordinary co-kriging with inclusion of information on the topographic index. The application of co-kriging is particularly justified in areas where there are nearby stations and where landform is very complex. We conclude that ordinary co-kriging is a very flexible and robust interpolation method because it may take into account several properties (soft and hard data) of the landscape.

  14. Climatology of extreme daily precipitation in Colorado and its diverse spatial and seasonal variability

    USGS Publications Warehouse

    Mahoney, Kelly M.; Ralph, F. Martin; Walter, Klaus; Doesken, Nolan; Dettinger, Michael; Gottas, Daniel; Coleman, Timothy; White, Allen

    2015-01-01

    The climatology of Colorado’s historical extreme precipitation events shows a remarkable degree of seasonal and regional variability. Analysis of the largest historical daily precipitation totals at COOP stations across Colorado by season indicates that the largest recorded daily precipitation totals have ranged from less than 60 mm day−1 in some areas to more than 250 mm day−1 in others. East of the Continental Divide, winter events are rarely among the top 10 events at a given site, but spring events dominate in and near the foothills; summer events are most common across the lower-elevation eastern plains, while fall events are most typical for the lower elevations west of the Divide. The seasonal signal in Colorado’s central mountains is complex; high-elevation intense precipitation events have occurred in all months of the year, including summer, when precipitation is more likely to be liquid (as opposed to snow), which poses more of an instantaneous flood risk. Notably, the historic Colorado Front Range daily rainfall totals that contributed to the damaging floods in September 2013 occurred outside of that region’s typical season for most extreme precipitation (spring–summer). That event and many others highlight the fact that extreme precipitation in Colorado has occurred historically during all seasons and at all elevations, emphasizing a year-round statewide risk.

  15. How Well Can the NARCCAP Models Capture the High-Resolution Spatial Patterns of the Precipitation Field in the Western United States

    NASA Astrophysics Data System (ADS)

    Chu, W.; Sellars, S.; Gao, X.; Sorooshian, S.

    2011-12-01

    In the western U.S. where complex terrains present, accurate information on high-resolution spatial distribution of precipitation is critical to many important issues, such as flood/landslide warning, reservoir operation, and water system planning. For instance, due to the highly heterogeneous spatial distribution of precipitation in California, vast manmade infrastructures, such as the Central Valley Project and California Water Project, have been built to resolve the mismatch between where precipitation falls and where water is consumed. In the face of climate variability, prudent planning and proper operation of these water infrastructures are essential to the region's sustainability. The success of planning requires accurate precipitation projection from climate models. In particular, two questions: 1) how well climate models can simulate the precipitation spatial patterns, and 2) how these patterns will change will climate, are of great interest to many researchers and managers in environmental planning and management. Our study are designed to answer these questions based on the dynamical downscaling results from the NARRCAP program and our recent findings on the high-resolution spatial patterns of the daily precipitation field in the western U.S. Using EOF analysis on the U.S. daily precipitation product of Climate Prediction Center (CPC), we revealed that there exists dominant spatial patterns in the precipitation field over the western United States. The spatial patterns are consistent at different spatial resolutions and persistent over decades. Therefore, we intend to evaluate how well climate models can capture these spatial patterns of observed precipitation in this region. EOF analysis is applied to precipitation outputs from NARRCAP, and the derived spatial patterns are compared with those of observation for the same time period. The similarity between model simulations and observation is quantified with mutual information based on Shannon entropy

  16. Massive sulfide deposits and hydrothermal solutions: incremental reaction modeling of mineral precipitation and sulfur isotopic evolution

    SciTech Connect

    Janecky, D.R.

    1986-01-01

    Incremental reaction path modeling of chemical and sulfur isotopic reactions occurring in active hydrothermal vents on the seafloor, in combination with chemical and petrographic data from sulfide samples from the seafloor and massive sulfide ore deposits, allows a detailed examination of the processes involved. This paper presents theoretical models of reactions of two types: (1) adiabatic mixing between hydrothermal solution and seawater, and (2) reaction of hydrothermal solution with sulfide deposit materials. In addition, reaction of hydrothermal solution with sulfide deposit minerals and basalt in feeder zones is discussed.

  17. Linking the isotopic composition of monthly precipitation, cave drip water and tree ring cellulose - 15 years of monitoring and data-model comparison

    NASA Astrophysics Data System (ADS)

    Labuhn, Inga; Genty, Dominique; Daux, Valérie; Bourges, François; Hoffmann, Georg

    2013-04-01

    The isotopic composition of proxies used for palaeoclimate reconstruction, like tree ring cellulose or speleothem calcite, is controlled to a large extent by the isotopic composition of precipitation. In order to calibrate and interpret these proxies in terms of climate, it is necessary to study water isotopes in rainfall and their link with the proxies' source water. We present 10 to 15-year series of stable hydrogen and oxygen isotopes in monthly precipitation from three sites in the south of France, along with corresponding REMOiso model simulations, a monitoring of cave drip water from two of these sites (Villars cave in the south-west and Chauvet cave in the south-east), as well as measurements of oxygen isotopes in tree ring cellulose from oak trees growing in the same area. The isotopic composition of monthly precipitation at the three sites displays a typical annual cycle. At the south-west sites, under Atlantic influence, the interannual variability is much more pronounced during the winter months than during the summer, whereas the south-eastern Mediterranean site shows the same variability throughout the year. The model simulations are able to reproduce the annual cycle of monthly precipitation δ18O as well as the intra-seasonal variability. Compared to the data, however, the modelled average isotopic values and the seasonal amplitude are overestimated. Correlations between temperature and precipitation δ18O are generally weak at all our sites, on both the monthly and the annual scale, even when using temperature averages weighted by the amount of precipitation. Consequently, a proxy which is controlled by the δ18O of precipitation cannot be directly interpreted in terms of temperature in this region. The isotopic composition of cave drip water in both caves remains stable throughout the monitoring period. By calculating different weighted averages of precipitation δ18O for time periods ranging from months to years, we demonstrate that the cave drip

  18. Modeling of the spatial distribution of precipitation and using of satellite systems «GRACE «in hydrological studies

    NASA Astrophysics Data System (ADS)

    Onuchin, Alexander; Musokhranova, Anastasia

    2015-04-01

    The precipitation dynamics was studied in the zone of the atmospheric pollution of the Noril'sk Mining and Smelting Complex (from west to east from 88°-101° E, and from north to south - from 58° -72°). N. The total monthly precipitation as derived from the data of 11 meteorological stations for the period from 1955 to 2009 was used for the analysis. The precipitation being one of the major water balance components affect the hydrological regime of the territory, as well as the state and functioning of ecosystems. The precipitation formation is a complex process depending on many factors. The most important ones are the water content and the temperature of the air mass and the peculiarities of vertical air motion. The cyclogenesis and the forced upward movement of air masses meeting the orographic barriers cause the precipitation. The type of the spatiotemporal distribution of precipitation is caused by the interaction between these two components (the first one is temporally dynamic and the second one, especially in the mountains, is quite spatially variable). For study area were obtained mathematical models which show the relationship background of snow with the amount of solid precipitation on representative meteorological stations and characterize the features of the distribution of solid precipitation in the study area based on geographical coordinates, altitude and terrain parameters that determine the barrier shade effects. The specificity of the natural conditions of formation of water resources and the hydrological regime of rivers in study area requires special methods for studying them. In the study of the dynamics of moisture content in the active layer a promising direction is the use of satellite systems «GRACE» (Gravity Recovery and Climate Experiment). Developed methodological approaches to the assessment snow pack according to GRACE, along with data on the value of solid precipitation at representative weather stations the data on snow pack

  19. Seasonal variation in the stable isotopic composition of precipitation in the tropical montane forests of Monteverde, Costa Rica

    NASA Astrophysics Data System (ADS)

    Rhodes, Amy L.; Guswa, Andrew J.; Newell, Silvia E.

    2006-11-01

    Climate and land use change may diminish orographic clouds over tropical montane forests, stressing biota and water resources during dry seasons. From 2003 to 2005 we measured the stable isotopic composition of precipitation and throughfall in Monteverde, Costa Rica, to distinguish convective, wet season rainfall associated with the Intertropical Convergence Zone (ITCZ) from dry season, orographic rain produced by northeasterly trade winds. While event-to-event fluctuations of δ18O and δ2H are high, monthly samples reveal a seasonal signal that may be used to trace water through the hydrologic cycle. Deuterium excess indicates that water evaporated from land is an important flux to the region during the transitional and dry seasons when winds from the Caribbean slope dominate. Following the shift to convective rainfall at the start of the wet season, when the western equatorial winds influence the Pacific slope of Costa Rica, d excess values become depressed. Yet as the wet season progresses, d excess begins to climb. These data suggest that several months of rain are needed following an acute dry season on the northern Pacific slope before a terrestrial evaporative signal is detected in wet season precipitation. The evaporative flux may result from a wet season expansion of surface water bodies and flooding of seasonal wetlands.

  20. Carbon Isotopes in Pinus elliotti cellulose 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., Jr.; Cherubini, P.

    2014-12-01

    Long-term, high-resolution paleoclimate data has never been more important as a means of putting global climate change in context. The inherent complexities of natural climate variability require a very long paleoproxy record that spans many cycles of overlapping multi-scale climate oscillations, such as the Atlantic Multidecadal Oscillation (AMO) and the El Niño-Southern Oscillation (ENSO), in order to distinguish the true effects of climate change. The tropical region has important linkages to global climate regulation and its annual stability makes it highly sensitive to climate change. It is predicted that tropical ecosystems will experience greater climate-related stress than those located at the poles. Yet, this region has an underrepresentation of high-resolution terrestrial paleoclimate records, such as those derived from the tree ring archives. South Florida, like many areas of the subtropics, has few tree species that are suitable for dendrochronological studies due to non-visible or seasonally inconsistent ring production. This study examines the potential of Pinus elliottii trees from Big Pine Key as a high-resolution terrestrial paleoclimate proxy for South Florida. The trees were difficult to cross-date using standard dendrochronology techniques. Instead, a chronology extending from 1927 to 2005 was developed by cross-dating patterns in the δ13C records. There is a strong, but complex, correlation between δ13C, ENSO and the AMO. The δ13C record trends with ENSO during the cool phase of the AMO, but there is an inverse relationship between δ13C and ENSO during the warm phases. The transition in the relationship between δ13C and ENSO occurs about 5 years before the AMO phase shift. In addition, preliminary analysis shows that about 45% of the variance in the carbon isotope chronology is related to precipitation and the ENSO signal is captured through the timing of that precipitation. During El Niño years, there is an increase in dry season

  1. Impact of moisture source regions on the isotopic composition of precipitation events at high-mountain continental site Kasprowy Wierch, southern Poland

    NASA Astrophysics Data System (ADS)

    Rozanski, Kazimierz; Chmura, Lukasz; Dulinski, Marek

    2016-04-01

    Five-year record of deuterium and oxygen-18 isotope composition of precipitation events collected on top of the Kasprowy Wierch mountain (49° 14'N, 19° 59'E, 1989 m a.s.l.) located in north-western High Tatra mountain ridge, southern Poland, is presented and discussed. In total 670 precipitation samples have been collected and analysed. Stable isotope composition of the analysed precipitation events varied in a wide range, from -2.9 to -26.6‰ for δ18O and from -7 to -195 ‰ for δ2H. The local meteoric water line (LMWL) defined by single events data (δ2H=(7.86±0.05)δ18O+(12.9±0.6) deviate significantly from the analogous line defined by monthly composite precipitation data available for IAEA/GNIP station Krakow-Balice (50o04'N, 19o55'E, 220 m a.s.l.), located ca. 100 km north of Kasprowy Wierch ((δ2H=(7.82±0.11)δ18O+(6.9±1.1). While slopes of those two LMWLs are statistically indistinguishable, the intercept of Kasprowy Wierch line is almost two times higher that that characterizing Krakow monthly precipitation. This is well-documented effect associated with much higher elevation of Kasprowy Wierch sampling site when compared to Krakow. The isotope data for Kasprowy Wierch correlate significantly with air temperature, with the slope of the regression line being equal 0.35±0.02 ‰oC for δ18O, whereas no significant correlation with precipitation amount could be established. The impact of moisture source regions on the isotopic composition of precipitation events collected at Kasprowy Wierch site was analysed using HYSPLITE back trajectory model. Five-days back trajectories were calculated for all analysed precipitation events and seasonal maps of trajectory distribution were produced. They illustrate changes in the prevailing transport patterns of air masses bringing precipitation to the sampling site. Back trajectories for the events yielding extreme isotopic composition of precipitation collected at Kasprowy Wierch were analyzed in detail

  2. Evaluation of kinetic effects on clumped isotope fractionation (Δ47) during inorganic calcite precipitation

    NASA Astrophysics Data System (ADS)

    Tang, Jianwu; Dietzel, Martin; Fernandez, Alvaro; Tripati, Aradhna K.; Rosenheim, Brad E.

    2014-06-01

    Considerable efforts have been made to calibrate the Δ47 paleothermometer, which derives from the quantity of 13C-18O bonds in carbon dioxide produced during acid digestion of carbonate minerals versus its expected stochastic abundance, in a range of materials. However the impacts of precipitation rate, ionic strength, and pH on carbonate Δ47 values are still unclear. Here we present a set of 75 measurements of Δ47 values from inorganic calcites grown under well-controlled experimental conditions, where we evaluate the impact on Δ47 values of precipitation rate (log R = 1.8-4.4 μmol/m2/h), pH (8.3-10.5; NBS pH scale), and ionic strength (I = 35-832 mM). With the data available and at the current instrumental resolution, our study does not resolve any clear effects of pH, ionic strength, growth rate effects on measured Δ47 when compared in magnitude to the effects on δ18O over most of the ranges of parameters sampled by our analyses. If these relationships exist, they must be smaller than our current ability to resolve them within our dataset. Under our experimental conditions, a Δ47-temperature equation, which is apparently insensitive to variation in pH, precipitation rate, and ionic strength over the range of variables sampled, can be written as Δ47=(0.0387±0.0072)×106/T2+(0.2532±0.0829) (r2=0.9998, p=0.009) where Δ47 values were reported on the absolute Δ47 reference frame after normalizing to conventional 25 °C reaction temperature using an acid fractionation factor of -0.00141‰ °C-1.

  3. Iodine isotopes in precipitation: temporal responses to (129)i emissions from the fukushima nuclear accident.

    PubMed

    Xu, Sheng; Freeman, Stewart P H T; Hou, Xiaolin; Watanabe, Akira; Yamaguchi, Katsuhiko; Zhang, Luyuan

    2013-10-01

    The Fukushima Dai-ichi Nuclear Power Plant accident in 2011 has released a large amount of radionuclides to the atmosphere, and the radioactive plume has been dispersed to a large area in Europe and returned to Asia. To explore long-term trend of the Fukushima-derived radioactive plume and the behavior of harmful radioiodine in the atmosphere, long-term precipitation samples have been collected over 2010-2012 at Fukushima, Japan for determination of long-lived (129)I. It was observed that (129)I concentrations of 1.2 × 10(8) atom/L in 2010 before the accident dramatically increased by ∼4 orders of magnitude to 7.6 × 10(11) atom/L in March 2011 immediately after the accident, with a (129)I/(127)I ratio up to 6.9 × 10(-5). Afterward, the (129)I concentrations in precipitation decreased exponentially to ∼3 × 10(9) atom/L by October 2011 with a half-life of about 29 days. This declining trend of (129)I concentrations in precipitation was interrupted around October 2011 by a new input of (129)I to the atmosphere following a second exponential decrease. Such a cycle has occurred three times until the present. This temporal variation can be attributed to alternating (129)I dispersion and resuspension from the contaminated local environment. A (129)I/(131)I atomic ratio of 16 ± 1 obtained from rainwater samples is comparable with a value estimated for surface soil samples. (129)I results from Denmark suggest an insignificant effect of (129)I released from Fukushima to the (129)I levels in Europe. PMID:24000802

  4. The Role of Microbes in the Precipitation of Microbialites in Cuatro Cienegas, Mexico: A Genomic and Stable Isotopic Perspective

    NASA Astrophysics Data System (ADS)

    Hollander, D. J.; Breitbart, M.; Hoare, A.; Seifert, J.; Edwards, R.; Rohwer, F.

    2007-12-01

    Ancient biologically-mediated sedimentary carbonate deposits, including stromatolites and other microbialites, provide insight into conditions on early Earth. However, interpretation of the environmental and evolutionary significance of microbialites throughout the geological record is dependent upon an understanding of the complex linkages between biological and chemical processes, and isotopic properties associated with the formation of modern microbialites. Here we present the results of metagenomic and isotopic analyses two types of actively accreting freshwater microbialites in Cuatro Cienegas: oncolites and thrombolites. To determine the genetic capabilities of the microbial communities and to identify the dominant metabolic pathways present in the samples, total DNA was purified from microbialite surface samples and pyrosequenced. Genes identified in the metagenome included both autotrophic and heterotrophic processes. In addition, 16S rDNA sequences recovered from the metagenome included both cyanobacteria and heterotrophic bacteria. d13C of intra-crystalline organic matter (IC- OM) in the microbialites is -26°, consistent with the enzymatic fractionation associated with oxygenic photosynthesis. The microscopy-based occurrence of cyanobacteria on the microbialites, the visible presence of bubbling O2, and the metagenomic confirmation of genes attributed to photosynthesis confirm the photoautotrophic origin of IC-OM. Carbonate d13C values of the oncolite and thrombolite are depleted relative to equilibrium considerations indicating that a 13C-depeleted source of carbon is strongly influencing the DIC at the site of carbonate precipitation. Respiration of photoautotrophic biomass by heterotrophic organisms would release 13C-depleted CO2 to the DIC reservoir resulting in a localized negative shift in the 13C-DIC. Our results indicate that the microbialites are precipitating at sites in direct association with heterotrophic respiration where the

  5. Effect of organic ligands on Mg partitioning and Mg isotope fractionation during low-temperature precipitation of calcite

    NASA Astrophysics Data System (ADS)

    Mavromatis, Vasileios; Immenhauser, Adrian; Buhl, Dieter; Purgstaller, Bettina; Baldermann, Andre; Dietzel, Martin

    2016-04-01

    Calcite growth experiments have been performed at 25 oC and 1 bar pCO2 in the presence of aqueous Mg and six organic ligands in the concentration range from 10‑5 to 10‑3 M. These experiments were performed in order to quantify the effect of distinct organic ligands on the Mg partitioning and Mg stable isotope fractionation during its incorporation in calcite at similar growth rates normalized to total surface area. The organic ligands used in this study comprise of (i) acetate acid, (ii) citrate, (iii) glutamate, (iv) salicylate, (v) glycine and (vi) ethylenediaminetetraacetic acid (EDTA), containing carboxyl- and amino-groups. These fuctional groups are required for bacterial activity and growth as well as related to biotic and abiotic mineralization processes occurring in sedimentary and earliest diagenetic aquatic environments (e.g. soil, cave, lacustrine, marine). The results obtained in this study indicate that the presence of organic ligands promotes an increase in the partition coefficient of Mg in calcite (DMg = (Mg/Ca)calcite (Mg/Ca)fluid). This behaviour can be explained by the temporal formation of aqueous Mg-ligand complexes that are subsequently adsorbed on the calcite surfaces and thereby reducing the active growth sites of calcite. The increase of DMg values as a function of the supersaturation degree of calcite in the fluid phase can be described by the linear equation LogDMg =0.3694 (±0.0329)×SIcalcite - 1.9066 (±0.0147); R2=0.92 In contrast, the presence of organic ligands, with exception of citrate, does not significantly affect the Mg isotope fractionation factor between calcite and reactive fluid (Δ26Mgcalcite‑fluid = -2.5 ±0.1). Citrate likely exhibits larger fractionation between the Mg-ligand complexes and free aqueous Mg2+, compared to the other organic ligands studied in this work, as evidenced by the smaller Δ26Mgcalcite‑fluid values. These results indicate that in Earth's surface calcite precipitating environments that are

  6. Long Term Ground Based Precipitation Data Analysis in California's 7 Climate Divisions: Spatial and Temporal Variability

    NASA Astrophysics Data System (ADS)

    Rodriguez, L.; El-Askary, H. M.; Rakovski, C.; Allai, M.

    2015-12-01

    California is an area of diverse topography and has what many scientists call a Mediterranean climate. Various precipitation patterns exist due to El Niño Southern Oscillation (ENSO) which can cause abnormal precipitation or droughts. As temperature increases mainly due to the increase of CO2 in the atmosphere, it is rapidly changing the climate of not only California but the world. An increase in temperature is leading to droughts in certain areas as other areas are experiencing heavy rainfall/flooding. Droughts in return are providing a foundation for fires harming the ecosystem and nearby population. Various natural hazards can be induced due to the coupling effects from inconsistent precipitation patterns and vice versa. Using wavelets and ARIMA modeling, we were able to identify anomalies of high precipitation and droughts within California's 7 climate divisions using NOAA's hourly precipitation data from rain gauges and compared the results with modeled data, SOI, PDO, and AMO. The identification of anomalies can be used to compare and correct remote sensing measurements of precipitation and droughts.

  7. Using atmospheric chemistry and storm tracks to explain nitrate stable isotope variations in precipitation at a site in central Pennsylvania, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stable isotopes of NO3- (delta15N-NO3- and delta18O-NO3-) were monitored in precipitation at a central Pennsylvania site during six storm events in 2005 to determine whether information on atmospheric oxidants (e.g. O3, NO2, and NOx), and storm-tracks were capable of explaining observed seasonal and...

  8. Interpreting bryophyte stable carbon isotope composition: Plants as temporal and spatial climate recorders

    NASA Astrophysics Data System (ADS)

    Royles, Jessica; Horwath, Aline B.; Griffiths, Howard

    2014-04-01

    are unable to control tissue water content although physiological adaptations allow growth in a wide range of habitats. Carbon isotope signals in two mosses (Syntrichia ruralis and Chorisodontium aciphyllum) and two liverworts (Conocephalum conicum and Marchantia polymorpha), whether instantaneous (real time, Δ13C), or organic matter (as δ13COM), provide an assimilation-weighted summary of bryophyte environmental adaptations. In mosses, δ13COM is within the measured range of Δ13C values, which suggests that other proxies, such as compound-specific organic signals, will be representative of historical photosynthetic and growth conditions. The liverworts were photosynthetically active over a wider range of relative water contents (RWC) than the mosses. There was a consistent 5‰ offset between Δ13C values in C. conicum and M. polymorpha, suggestive of greater diffusion limitation in the latter. Analysis of a C. aciphyllum moss-peat core showed the isotopic composition over the past 200 years reflects recent anthropogenic CO2 emissions. Once corrected for source-CO2 inputs, the seasonally integrated Δ13COM between 1350 and 2000 A.D. varied by 1.5‰ compared with potential range of the 12‰ measured experimentally, demonstrating the relatively narrow range of conditions under which the majority of net assimilation takes place. Carbon isotope discrimination also varies spatially, with a 4‰ shift in epiphytic bryophyte organic matter found between lowland Amazonia and upper montane tropical cloud forest in the Peruvian Andes, associated with increased diffusion limitation.

  9. Quantification and analysis of deuterium and oxygen-18 isotope composition of precipitation at the southern foothills of Mt. Kilimanjaro (Tanzania)

    NASA Astrophysics Data System (ADS)

    Otte, Insa; Detsch, Florian; Appelhans, Tim; Nauss, Thomas

    2015-04-01

    Tropical rainforest are important ecosystems for cycling water at local, regional and global scales. A number of studies have emphasized the increasing trend of extreme seasonal and inter-annual variability of precipitation and hydrology in the Kilimanjaro region. So far, only a limited number of observations have been available for water budget quantification. For quantifying atmospheric water input at the southern foothills of Mt. Kilimanjaro, rainfall, fog and throughfall were measured for two years along an elevation and disturbance gradient ranging from 950 m a.s.l. to 3,880 m a.s.l.. Measurements were conducted at eight research plots, equipped with one accumulating rainfall bucket, one accumulating standard mesh fog collector and a sampling network of 29 accumulating throughfall buckets. The bimodal rainfall distribution is shaped by a "short" (October to December) and "long" (March to May) rainy season. Maximum annual rainfall is denoted in the midmontane zone between 2,200 m a.s.l. and 2,490 m a.s.l. (approximately 3,300 mm). In higher elevations precipitation amounts declines, reaching 55% of the maximum at 3,880 m a.s.l., while fog water deposition ranges from 2% of rainwater input in the lower montane forest (1,800 m a.s.l.) to 8% at 3,880 m a.s.l.. Stable isotope composition of volume-weighted samples from eight of the 29 throughfall accumulation buckets, the fog mesh grid and the rainfall accumulation gauge were measured in a weekly interval from November 2012 to November 2014 on each of the eight research plots. To get insights into the importance of local vs. remote water sources, two additional rainfall gauges were installed in eastern direction (Same, Mkomazi National Park, Tanga) to get isotope characteristics of the approaching rainfall systems. During one transition from dry to wet (December 2013) and wet to dry (April 2014) season, the sampling interval was increased to a sub-daily resolution to account for amount and elevation effects in the

  10. Prediction of spatial variation in global fallout of 137Cs using precipitation.

    PubMed

    Pálsson, S E; Howard, B J; Wright, S M

    2006-08-31

    Deposition from atmospheric nuclear weapons tests (termed global fallout) has been shown to be proportional to the rate of precipitation. Here we describe methods for using precipitation and radionuclide deposition information for a reference site to estimate global fallout at other locations. These methods have been used to estimate global fallout in Iceland, identified during the Arctic Monitoring and Assessment Programme (AMAP) by Wright et al. [Wright, S.M., Howard, B.J., Strand, P., Nylén, T., Sickel, M.A.K., 1999. Prediction of 137Cs deposition from atmospheric nuclear weapons tests within the Arctic. Environ Pollut 104, 131-143.] as one of the Arctic areas which received the highest global fallout, but where measurements of contamination were sparse, and difficult to obtain due to the remote and inaccessible terrain of much of the country. Measurements of global fallout 137Cs deposition have been made in Iceland at sites close to meteorological stations to ensure that precipitation data were of high quality. The AMAP modeling approach, based on measured precipitation and radionuclide deposition data, was applied using a reference monitoring station located close to Reykjavik. The availability of good precipitation data and locally based estimates of time dependent ratios of 137Cs deposition to precipitation during the fallout period gave a better correlation between predicted and measured 137Cs global fallout (r2=0.96) than that achieved using the much more heterogeneous set of data collected by AMAP over the whole of the Arctic. Having obtained satisfactory results with the model for a number of calibration sites alongside meteorological stations we then produced a map of estimated 137Cs deposition based on a model of estimated precipitation. This deposition map was then successfully validated (r2=0.85) for sites where 137Cs deposition was measured; the associated uncertainty in predictions was also estimated. PMID:16545432

  11. Experimental fractionation of stable carbon isotopes during degassing of carbon dioxide and precipitation of calcite from aqueous solutions

    NASA Astrophysics Data System (ADS)

    Müller, K.; Winde, V.; Escher, P.; von Geldern, R.; Böttcher, M. E.

    2012-04-01

    system of the solution was controlled by both, degassing and carbonate precipitation, still leading to an enrichment of the heavier carbon isotope in the residual DIC. The experimental results are evaluated for both periods, and the influence of salinity and pH is extracted. Acknowledgement: Parts of this study were supported by BMBF within the BIOACID project

  12. Spatial and temporal variations in ecosystem response to monsoon precipitation variability in southwestern North America

    NASA Astrophysics Data System (ADS)

    Forzieri, Giovanni; Feyen, Luc; Cescatti, Alessandro; Vivoni, Enrique R.

    2014-10-01

    Due to its marked vegetation phenology and precipitation gradients, the North American Monsoon Region (NAMR) is a useful domain for studying ecosystem responses to climate variability and change. To this end, we analyze long-term dynamics (1982-2004) in monsoon precipitation (Pr), time-integrated Normalized Difference Vegetation Index (TINDVI) used as proxy of net primary productivity, and rain-use efficiency (RUE). The analysis focuses on six ecoregions, spanning from desert environments to tropical dry forests, to investigate (1) how net primary productivity and rain-use efficiency vary along a precipitation gradient, (2) if interannual variability in net primary productivity is linked to the interannual variability in precipitation, and (3) if there is evidence of a long-term signal imposed on the interannual variability in rain-use efficiency. Variations in TINDVI and RUE with Pr along the NAMR precipitation gradient differ among ecoregions exhibiting intensive or extensive water use strategies. We explain the nonlinear behaviors along the precipitation gradient as resulting from different physiological responses to climatological means and the impact of topographic effects. Statistical analysis indicates that the interannual variability in vegetation response is significantly related to the interannual variability in Pr, but their correlation declines with time. A long-term positive signal in RUE imposed on its interannual variability is identified and results from a constant TINDVI under negative long-term trends of Pr. This important finding suggests the combined long-term effects of ecosystem acclimation to reduced water availability and increasing CO2 concentration across the varied ecosystems of the North American Monsoon Region.

  13. Asynchronous evolution of the isotopic composition and amount of precipitation in north China during the Holocene revealed by a record of compound-specific carbon and hydrogen isotopes of long-chain n-alkanes from an alpine lake

    NASA Astrophysics Data System (ADS)

    Rao, Zhiguo; Jia, Guodong; Li, Yunxia; Chen, Jianhui; Xu, Qinghai; Chen, Fahu

    2016-07-01

    Both the timing of the maximum East Asian summer monsoon (EASM) intensity in monsoonal China and the environmental significance of the Chinese stalagmite oxygen isotopic record (δ18O) have been debated. Here, we present a ca. 120-year-resolution compound-specific carbon (δ13C) and hydrogen (δD) isotopes of terrestrial long-chain n-alkanes extracted from a well-dated sediment core from an alpine lake in north China. Our δ13C data, together with previously reported pollen data from a parallel core, demonstrate a humid mid-Holocene from ca. 8-5 ka BP. Assuming that the climatic humidity of north China is an indicator of the EASM intensity, then the maximum EASM intensity occurred in the mid-Holocene. Our δD data reveal a similar long-term trend to the δ18O record from nearby Lianhua Cave, indicating that the synchronous δD and δ18O records faithfully record the δD and δ18O of precipitation, respectively. The most negative δD and δ18O values occur in the early-mid Holocene, from ca. 11-5 ka BP. This contrast in the timing of isotopic variations demonstrates a complex relationship between the isotopic composition of precipitation and precipitation amount, or EASM intensity. Further comparisons indicate a possible linkage between the precipitation amount in north China and the west-east thermal gradient in the equatorial Pacific. In addition, the temperature of the moisture source area may play an important role in determining the isotopic composition of precipitation in monsoonal China.

  14. Groundwater discharge into an estuary using spatially distributed radon time series and radium isotopes

    NASA Astrophysics Data System (ADS)

    Sadat-Noori, Mahmood; Santos, Isaac R.; Sanders, Christian J.; Sanders, Luciana M.; Maher, Damien T.

    2015-09-01

    Quantifying groundwater discharge remains a challenge due to its large temporal and spatial variability. Here, we quantify groundwater discharge into a small estuary using radon (222Rn) and radium isotopes (223Ra and 224Ra). High temporal resolution (30 min time steps) radon observations at 4 time series stations were used to determine where groundwater discharge is prevalent in the estuary, and to reduce mass balance model uncertainties. A three-endmember mixing model was developed based on short-lived radium isotopes (sampled at a single location) to separate the shallow saline and deep fresh sources of the discharging groundwater. The results show that using multiple 222Rn time series stations decreased the overall uncertainty of groundwater discharge estimates from about 41% to 23%. The radon derived groundwater flux was 56 ± 13 and 35 ± 12 cm d-1 in wet and dry conditions, respectively. The spatially distributed stations detected a well-defined small area located four kilometers upstream from the mouth of the estuary as a groundwater discharging hotspot. Estimates based on a 223Ra and 224Ra mass balance resulted in groundwater discharge estimates of 65 ± 18 and 84 ± 48 cm d-1 in the wet and 18 ± 5 and 20 ± 6 cm d-1 in the dry. The mixing model revealed contrasting results for deep vs. fresh groundwater contribution in wet and dry conditions. In wet conditions, deep fresh groundwater discharging into the estuary contributed 65% compared to the shallow saline groundwater (35%), while during dry conditions a larger contribution (80%) was related to shallow groundwater. A comprehensive spatial and temporal sampling strategy can produce groundwater discharge estimates with lower uncertainty and provides additional insight on where groundwater enters surface waters.

  15. ON THE SPATIAL DISTRIBUTION OF PRECIPITATION SEASONALITY IN THE UNITED STATES

    EPA Science Inventory

    A detailed, long term portrait of the seasonality of precipitation over the United States is developed using a 90 year climate division record. ecadal maps of seasonality are also presented, and their variability over time considered. odel output from four GCMs are analyzed with ...

  16. Spatial and vertical variability of different types of tropical precipitating systems over India and adjoining oceans

    NASA Astrophysics Data System (ADS)

    Narayana Rao, T.; Saikranthi, K.

    2012-07-01

    The classification of precipitation into different rain regimes is useful for a variety of meteorological applications, from fundamental understanding of cloud physics, areal quantification of rainfall using scanning radars (both space-borne and ground-based) and microwave retrieval of rainfall. Also the latent heat profiles of different precipitating systems are distinct, which impact the atmospheric circulation differently. Earlier studies focused their attention on quantification of the surface rainfall and its variability on different temporal scales (intraseasonal, interannual, decadal, etc.). Further, earlier studies on rainfall were not able to study the vertical structure of precipitation, because they are mostly based on rain gauge measurements. The present study, therefore, aims to devise a classification scheme by grouping TRMM PR derived rain types into shallow (stratus and convection) and deep (stratiform, convection and transition) precipitating systems and provide a quantitative description of these systems by effectively utilizing 13 years of TRMM measurements, European Centre for Medium-Range Weather Forecasts (ECMWF)-Interim reanalysis products and radiosonde measurements at 33 stations in India. In particular, this study addresses the following important questions. Which type of rainfall (stratiform, convective, and warm rain) prevails most over different parts of India? How much each type of precipitation contributes to the total rainfall? The present study focuses not on the absolute amounts of precipitation by each type of system, rather on studying the relative contributions of different types of systems to the total precipitation and their occurrence over India and adjoining oceans. We also discuss the problems associated with the utilization of climatological surface data for estimating the freezing level height, which is required for identifying warm rain and also for stratiform rain (for bright band detection). TRMM PR underestimates (in

  17. Precipitation of smithsonite under controlled pCO2 between 25 and 60° C - Fractionation of oxygen isotopes

    NASA Astrophysics Data System (ADS)

    Füger, Anja; Mavromatis, Vasileios; Leis, Albrecht; Dietzel, Martin

    2016-04-01

    Owing to the large fractionation (i.e. Δ18Osolid‑diss. ˜30) between carbonate minerals and aqueous fluids with respect to their 18O/16O composition, the oxygen isotope composition of carbonates has been a fundamental tool for the estimation of mineral formation temperature by the geoscience community. Indeed the last 6 decades, a wide number of experimental studies investigated the temperature relation of Δ18Osolid‑diss. between divalent metal carbonates and aqueous fluids. To date however no experimental data exist for the temperature dependence of Δ18Osolid‑diss. between smithsonite (ZnCO3) and fluid. This lack of data likely stems from a kinetic barrier effect, that of the dehydration of aqueous Zn2+ and the formation of hydrozincite (Zn5(CO3)2(OH)6). Smithsonite is a secondary zinc mineral that is one of the components of zinc ore bodies. It is formed through oxidation of primary zinc ores by the reaction with a carbonate source or by precipitation of zinc salt solutions with a CO2-saturated and bicarbonate-rich solution. In this study we hydrothermally synthesized smithsonite at the temperature range between 25 and 60 ° C and report the temperature dependence of oxygen isotope distribution between smithsonite and aqueous fluid. In order to avoid the formation of hydrozincite our experiments were conducted in titanium batch reactors using Teflon-inlets where the CO2 pressure was adjusted to 10 bars. The low pH conditions provoked by the elevated pCO2 applied, lead to the dissolution of hydrozincite, which is initially formed by mixing of Na2HCO3 (0.1 M) and Zn(NO3)2.4 H2O (0.02 M) solutions, to yield - under the prevailing conditions - the thermodynamically stable mineral smithsonite.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

    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 δ18O correlates strongly with δ18O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ18O 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 δ18O over the 20th century consistent with increases in Andean δ18O 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.

  19. Sensitivity of a simulated extreme precipitation event to spatial resolution, parametrisations and assimilation

    NASA Astrophysics Data System (ADS)

    Ferreira, J.; Carvalho, A.; Carvalheiro, L.; Rocha, A.; Castanheira, J.

    2010-09-01

    In the morning of the 18th of February 2008 Lisbon and Setúbal were under the influence of a heavy rain event associated to a cut-off low formed in southern Azores between the 14th and 15th of February. The total daily precipitation record was exceeded in the 18th of February at Lisboa/Geofísico station; 36 mm of precipitation were registered between 4 and 5 a.m., whereas in Setúbal 60 mm were recorded during one hour (between 11 and 12 a.m.), of the same day. These two cities are located near the mouth of Tagus and Sado rivers, respectively, running to the Atlantic Ocean, and both have experience severe floods. The present work will present the sensitivity of the Weather Research and Forecasting (WRF) model to different geometric model configurations and physical parametrisations, and to data assimilation procedures for the same grid resolution and physical parametrisations. The WRF model is running in operational mode for Portugal at the University of Aveiro in two different horizontal and vertical resolution and physical set of parametrisations, driven by the Global Forecast System (GFS) forecasts. The first configuration (OP1) is shown in http://climetua.fis.ua.pt/main/otempo.php?lang=pt and consists of two nested domains and 27 vertical levels, the coarsest domain (25 km) covering the Iberian Peninsula and part of the East Atlantic and the finer grid domain (5 km) covering Portugal. For the second configuration (OP2) (shown in http://www2.fis.ua.pt/torre/luis/), the outer and inner domains have a horizontal resolution of 21 and 7 km, respectively. The physics parametrisation of the two operational designs differ on the microphysics and cumulus schemes, and on the applied land surface model, which are named respectively for: (i) OP1 - WSM 6 class graupel microphysics scheme, Grell-Devenyi ensemble cumulus scheme and Unified Noah land-surface model; (ii) OP2 - Ferrier microphysics scheme, Kain-Fritsch cumulus scheme and Thermal diffusion land-surface model

  20. Spatially-resolved stable isotope analysis of a hypersaline microbial mat

    NASA Astrophysics Data System (ADS)

    Moran, J.; Cory, A. B.; Lindemann, S. R.; Fredrickson, J. K.

    2012-12-01

    Hot Lake is a hypersaline, meromictic lake located in north-central Washington. High rates of evapotranspiration coupled with its location in an endorrheic basin contribute to the lake's high salinity. The predominant dissolved salt is magnesium sulfate; hypolimnion waters may seasonally exceed 2 M magnesium sulfate concentrations. In addition to extreme salinity, horizons within the lake seasonally exceed 50 °C, in part due to the enhanced light absorption by magnesium sulfate-saturated water. Despite extreme and highly variable seasonal conditions (salinity, temperature, photon flux), dense benthic microbial mats composed of cyanobacteria and bacterial heterotroph populations develop annually at the lake. These mats may exceed 5 mm in thickness and display stratification observable by eye associated with dominant bacterial phototrophic pigments. Typical mat stratification includes an orange surface layer followed by green and purple layers at increasing depth into the mat. Carbonates including aragonite and magnesite are observed within the mat and their formation is likely induced or influenced by microbial activities. While not exclusively limited to the green stratum in the mat, maximum carbonate content is within this layer. We are exploring the role Hot Lake's microbial mats play in carbon cycling within the system. Namely, we seek to understand the rates of carbon accumulation in the mat and associated sediments and the various forms this carbon takes (organic or inorganic species). We are assessing mat development, community composition, and carbon accumulation in pre-cleaned devices installed at the lake as they are colonized by native mat. We are using laser ablation isotope ratio mass spectrometry (LA-IRMS) to provide spatially-resolved stable isotope analysis of mat cross-sections. Currently, this technique permits isotope analysis at the 50 μm scale, and can provide multiple isotope analyses within the thickness of each major layer of the mat. We

  1. Multiple sulfur isotope fractionation and mass transfer processes during pyrite precipitation and recrystallization: An experimental study at 300 and 350 °C

    NASA Astrophysics Data System (ADS)

    Syverson, Drew D.; Ono, Shuhei; Shanks, Wayne C.; Seyfried, William E.

    2015-09-01

    Equilibrium multiple sulfur isotope fractionation factors (33S/32S and 34S/32S) between aqueous SO4, H2S, and coexisting pyrite under hydrothermal conditions were determined experimentally at 300-350 °C and 500 bars. Two different experimental techniques were used to determine the fractionation factors and the rate of S isotope exchange between pyrite and constituent aqueous species, H2S and SO4; (1) closed system gold capsule pyrite-H2S exchange experiments and (2) complimentary time-series experiments at 300 and 350 °C, 500 bars using flexible gold cell hydrothermal equipment, which allowed monitoring the multiple S isotope composition of dissolved S species during pyrite precipitation and subsequent recrystallization. The three isotope technique was applied to the multiple S isotope data to demonstrate equilibrium S isotope fractionation between pyrite and H2S. Results at 350 °C indicate ln34αPyrite/H2S = -1.9‰ and ln33αPyrite/H2S = -1.0‰. The ln34αPyrite/H2S is not only different in magnitude but also in sign from the commonly used value of 1‰ from Ohmoto and Rye (1979). This experimental study also demonstrated initial S isotope disequilibrium amongst the aqueous S-species and pyrite during rapid precipitation, despite aqueous speciation indicating pyrite saturation at all stages. Textural, crystallographic, and S isotope interpretations suggest that pyrite formed by means of the FeS pathway. The initial S isotope disequilibrium between formed pyrite and dissolved S-species was effectively erased and approached isotopic equilibrium upon recrystallization during the course of 4297 h. Interpretation of seafloor hydrothermal vent sulfides using the revised equilibrium 34S/32S fractionation between pyrite and H2S suggests that pyrite is close to S isotope equilibrium with vent H2S, contrary to previous conclusions. The experimental data reported here broaden the range of pyrite formation mechanisms at seafloor hydrothermal vents, in that mineral

  2. Precipitation origin and evaporation of lakes in semi-arid Patagonia (Argentina) inferred from stable isotopes ( δ18O, δ2H)

    NASA Astrophysics Data System (ADS)

    Mayr, Christoph; Lücke, Andreas; Stichler, Willibald; Trimborn, Peter; Ercolano, Bettina; Oliva, Gabriel; Ohlendorf, Christian; Soto, Julio; Fey, Michael; Haberzettl, Torsten; Janssen, Stephanie; Schäbitz, Frank; Schleser, Gerhard H.; Wille, Michael; Zolitschka, Bernd

    2007-02-01

    Stable isotope approaches are often used for estimating water balances of lakes. Such studies require regional background information about hydrogen and oxygen isotope variability of lakes and their potential inflows. Here, a stable isotope database ( δ2H and δ18O) is presented for estimating evaporation to inflow ratios ( E/ I) of lakes in semi-arid southern Patagonia. Water samples of 23 lakes and ponds located in the Patagonian steppe at about 52°S were sampled during three subsequent austral summers. Two deep crater lakes, Laguna Azul and Laguna Potrok Aike, were studied in more detail during a two-years monitoring. Furthermore, precipitation, groundwater and atmospheric water vapor were sampled for isotope analyses. Presented data imply that the isotopic composition of rainfall in southeastern Patagonia is predominantly determined by precipitation amount and moisture source area. For the investigated area, the first meteoric water and evaporation lines in δ2H vs. δ18O space are presented. The database was further used to estimate the water balances of the two crater lakes, Laguna Azul and Laguna Potrok Aike, which are in the focus of recent paleoclimatic investigations. According to that approach about 50% and 60%, respectively, of the water entering Laguna Azul and Laguna Potrok Aike via surface and subsurface inflow evaporates. These results testify a considerable flow of lake waters into the groundwater.

  3. Dayside pickup oxygen ion precipitation at Venus and Mars - Spatial distributions, energy deposition and consequences

    NASA Astrophysics Data System (ADS)

    Luhmann, J. G.; Kozyra, J. U.

    1991-04-01

    The fluxes and energy spectra of picked-up planetary O(+) ions incident on the dayside atmospheres of Venus and Mars are calculated. Maps of precipitating ion number flux and energy flux are presented which show the asymmetrical distribution of dayside energy deposition expected from this source. Although the associated heating of the atmosphere and ionosphere is found to be negligible compared to that from the usual sources, backscattered or sputtered neutral oxygen atoms are produced at energies which exceed that needed for escape from the gravitational fields of both planets. These neutral 'winds', driven by pickup ion precipitation, represent a possibly significant loss of atmospheric constituents over the age of the solar system.

  4. Chemical and isotopic data collected from groundwater, surface-water, and atmospheric precipitation sites in Upper Kittitas County, Washington, 2010-12

    USGS Publications Warehouse

    Hinkle, Stephen R.; Ely, D. Matthew

    2013-01-01

    As part of a multidisciplinary U.S. Geological Survey study of water resources in Upper Kittitas County, Washington, chemical and isotopic data were collected from groundwater, surface-water, and atmospheric precipitation sites from 2010 to 2012. These data are documented here so that interested parties can quickly and easily find those chemical and isotopic data related to this study. The locations of the samples are shown on an interactive map of the study area. This report is dynamic; additional data will be added to it as they become available.

  5. Spatial and temporal variation in isotopic composition of atmospheric lead in Norwegian moss

    SciTech Connect

    Rosman, K.J.R.; Ly, C.; Steinnes, E.

    1998-09-01

    Earlier studies using moss as a biomonitor of pollution have shown that long-range transport is a major source of pollution in Norway. Until now, the origin of these pollutants has been inferred from concentration measurements of various elements in moss and the climatology at each sampling site. Lead isotopes provide an opportunity to identify the sources and to quantify the contribution of each. This preliminary study reports measurements of lead isotopes in moss from selected sites along the full extent of Norway that reveal significant spatial and temporal variations. There are significant north-south trends that differ at coastal and inland sites and differ between sampling periods (1974--1994). These variations reflect the changing contributions from the different source regions as the regulation of pollution from automobiles and industry takes effect. Identifiable sources are the U.K. and possibly France, which is noticeable at coastal sites; western Europe at the southern end; and eastern Europe and Russia influencing the inland and northernmost sites.

  6. Spatial decorrelation stretch of annual (2003-2014) Daymet precipitation summaries on a 1-km grid for California, Nevada, Arizona, and Utah.

    PubMed

    Ch Miliaresis, George

    2016-06-01

    A method is presented for elevation (H) and spatial position (X, Y) decorrelation stretch of annual precipitation summaries on a 1-km grid for SW USA for the period 2003 to 2014. Multiple linear regression analysis of the first and second principal component (PC) quantifies the variance in the multi-temporal precipitation imagery that is explained by X, Y, and elevation (h). The multi-temporal dataset is reconstructed from the PC1 and PC2 residual images and the later PCs by taking into account the variance that is not related to X, Y, and h. Clustering of the reconstructed precipitation dataset allowed the definition of positive (for example, in Sierra Nevada, Salt Lake City) and negative (for example, in San Joaquin Valley, Nevada, Colorado Plateau) precipitation anomalies. The temporal and spatial patterns defined from the spatially standardized multi-temporal precipitation imagery provide a tool of comparison for regions in different geographic environments according to the deviation from the precipitation amount that they are expected to receive as function of X, Y, and h. Such a standardization allows the definition of less or more sensitive to climatic change regions and gives an insight in the spatial impact of atmospheric circulation that causes the annual precipitation. PMID:27220500

  7. Categorisation of northern California rainfall for periods with and without a radar brightband using stable isotopes and a novel automated precipitation collector

    USGS Publications Warehouse

    Coplen, Tyler B.; Paul J. Neiman; Allen B. White; Ralph, F. Martin

    2015-01-01

    During landfall of extratropical cyclones between 2005 and 2011, nearly 1400 precipitation samples were collected at intervals of 30-min time resolution with novel automated collectors at four NOAA sites in northern California [Alta (ATA), Bodega Bay (BBY), Cazadero (CZD) and Shasta Dam (STD)] during 43 events. Substantial decreases were commonly followed hours later by substantial increases in hydrogen isotopic composition (δ2HVSMOW where VSMOW is Vienna Standard Mean Ocean Water) and oxygen isotopic composition (δ18OVSMOW) of precipitation. These variations likely occur as pre-cold frontal precipitation generation transitions from marine vapour masses having low rainout to cold cloud layers having much higher rainout (with concomitant brightband signatures measured by an S-band profiling radar and lower δ2HVSMOW values of precipitation), and finally to shallower, warmer precipitating clouds having lower rainout (with non-brightband signatures and higher δ2HVSMOW values of precipitation), in accord with ‘seeder–feeder’ precipitation. Of 82 intervals identified, a remarkable 100.5 ‰ decrease in δ2HVSMOW value was observed for a 21 January 2010 event at BBY. Of the 61 intervals identified with increases in δ2HVSMOW values as precipitation transitioned to shallower, warmer clouds having substantially less rainout (the feeder part of the seeder–feeder mechanism), a remarkable increase in δ2HVSMOW value of precipitation of 82.3 ‰ was observed for a 10 February 2007 event at CZD. All CZD and ATA events having δ2HVSMOW values of precipitation below −105 ‰ were atmospheric rivers (ARs), and of the 13 events having δ2HVSMOWvalues of precipitation below −80 ‰, 77 % were ARs. Cloud echo-top heights (a proxy for atmospheric temperature) were available for 23 events. The mean echo-top height is greater for higher rainout periods than that for lower rainout periods in 22 of the 23 events. The lowest δ2HVSMOW of precipitation of 28

  8. Spatial characteristics of observed precipitation fields: A catalog of summer storms in Arizona, Volume 2

    NASA Technical Reports Server (NTRS)

    Fennessey, N. M.; Eagleson, P. S.; Qinliang, W.; Rodriguez-Iturbe, I.

    1986-01-01

    The parameters of the conceptual model are evaluated from the analysis of eight years of summer rainstorm data from the dense raingage network in the Walnut Gulch catchment near Tucson, Arizona. The occurrence of measurable rain at any one of the 93 gages during a noon to noon day defined a storm. The total rainfall at each of the gages during a storm day constituted the data set for a single storm. The data are interpolated onto a fine grid and analyzed to obtain: an isohyetal plot at 2 mm intervals, the first three moments of point storm depth, the spatial correlation function, the spatial variance function, and the spatial distribution of the total storm depth. The description of the data analysis and the computer programs necessary to read the associated data tapes are presented.

  9. Spatial characteristics of observed precipitation fields: A catalog of summer storms in Arizona, Volume 1

    NASA Technical Reports Server (NTRS)

    Fennessey, N. M.; Eagleson, P. S.; Qinliang, W.; Rodrigues-Iturbe, I.

    1986-01-01

    Eight years of summer raingage observations are analyzed for a dense, 93 gage, network operated by the U. S. Department of Agriculture, Agricultural Research Service, in their 150 sq km Walnut Gulch catchment near Tucson, Arizona. Storms are defined by the total depths collected at each raingage during the noon to noon period for which there was depth recorded at any of the gages. For each of the resulting 428 storms, the 93 gage depths are interpolated onto a dense grid and the resulting random field is anlyzed. Presented are: storm depth isohyets at 2 mm contour intervals, first three moments of point storm depth, spatial correlation function, spatial variance function, and the spatial distribution of total rainstorm depth.

  10. Carbon Dioxide and CO2 Isotopes at Three Spatial Scales Over the Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Bowling, D. R.; Schaeffer, S. M.; Miller, J. B.; Stephens, B. B.

    2006-12-01

    Recent studies highlight the importance of western mountain regions to the North American carbon sink, suggesting 25 to 50 percent of the U.S. sink can be attributed to montane ecosystems. Isotopes of CO2 provide insight into ecosystem carbon cycling, plant physiological processes, and atmospheric boundary-layer dynamics, and are useful in integration of processes over multiple scales. CO2 isotopes have played a central role in our understanding of the magnitude and inter-annual dynamics of the terrestrial carbon sink at a variety of spatial and temporal scales, and will be crucial to understanding the carbon balance and carbon accounting of the North American continent. In 2005, we began a long-term study examining biosphere- atmosphere exchange of CO2 and its stable isotopes over the Rocky Mountains in Colorado. Measurements are made at 3 sites representing 3 different spatial scales. These include a subalpine forest site (3050 m elevation, the Niwot Ridge AmeriFlux site), a tundra site 3 km away (3520 m, representing the overlying forest air), and an aircraft site 125 km to the northeast over the plains (vertical profiles from ground level at 1740 m to 8000 m, representing the regional convective boundary layer and the free troposphere). The tundra (NWR) and aircraft (CAR) sites have been part of NOAA/CCGG Cooperative Air Sampling Network for many years. Observed CO2 and δ13C showed seasonal variation (> 10 ppm and >0.5 permil) and strong local variation at all sites (>100 ppm and >5 permil at the forest site). The forest exerted a strong respiratory influence on the overlying air during the fall and winter. Measurements 10m above the top of the forest canopy in winter were always higher in CO2 (~ 3 ppm) and more negative in δ13C of CO2 ~ 0.3 permil) than those at the tundra site. Summer data are still being analyzed, but we expect this to shift in the other direction during the growing season. Substantial synoptic variation in CO2 and δ13C was observed at

  11. Spatial trend analysis and uncertainty estimates of acid precipitation data in Ontario

    SciTech Connect

    Tang, A.J.S.; Chan, W.H.

    1985-01-01

    The use of the Simple Kriging and Universal Kriging methods to estimate the spatial trend in the spatial data is examined. By following the approach of the Simple Kriging methods, a new Modified Kriging method has been developed for better presentation of the spatial pattern of spatial data and error estimation. Results of comparison indicate that the Modified Simple Kriging method can provide better interpolation and error estimation for the mathematical functions. Although the results of practical interpolation obtained by using the three methods are quite comparable, the error estimates by the Simple Kriging and Universal Kriging methods are greater than those of the modified Simple Kriging method and the one standard deviation confidence belts are overlapping each other. This may indicate that the error estimations from the Simple Kriging methods are too great.The Universal Kriging method provides the greatest error estimation among these three methods. Although those results indicate that there is no advantages of using the Universal Kriging method, further study on the proper formula for the generalized covariance function should be carried out. The heart of the Universal Kriging method is to find the correct covariance function, since the isopleths and the error of estimation are very sensitive to it.

  12. Numerical investigation into effects of complex terrain on spatial and temporal variability of precipitation

    SciTech Connect

    Stalker, J.R.; Bossert, J.E.; Reisner, J.M.

    1998-12-31

    This study is part of an ongoing research effort at Los Alamos to understand the hydrologic cycle at regional scales by coupling atmospheric, land surface, river channel, and groundwater models. In this study the authors examine how local variation of heights of the two mountain ranges representative of those that surround the Rio Grande Valley affects precipitation. The lack of observational data to adequately assess precipitation variability in complex terrain, and the lack of previous work has prompted this modeling study. Thus, it becomes imperative to understand how the local terrain affects snow accumulations and rainfall during winter and summer seasons respectively so as to manage this valuable resource in this semi-arid region. While terrain is three dimensional, simplifying the problem to two dimensions can provide some valuable insight into topographic effects that may exist at various transects across the Rio Grande Valley. The authors induce these topographic effects by introducing variations in heights of the mountains and the width of the valley using an analytical function for the topography. The Regional Atmospheric Modeling System (RAMS) is used to examine these effects.

  13. Spatially Resolved, In Situ Carbon Isotope Analysis of Archean Organic Matter

    NASA Technical Reports Server (NTRS)

    Williford, Kenneth H.; Ushikubo, Takayuki; Lepot, Kevin; Hallmann, Christian; Spicuzza, Michael J.; Eigenbrode, Jennifer L.; Summons, Roger E.; Valley, John W.

    2011-01-01

    Spatiotemporal variability in the carbon isotope composition of sedimentary organic matter (OM) preserves information about the evolution of the biosphere and of the exogenic carbon cycle as a whole. Primary compositions, and imprints of the post-depositional processes that obscure them, exist at the scale of individual sedimentary grains (mm to micron). Secondary ion mass spectrometry (SIMS) (1) enables analysis at these scales and in petrographic context, (2) permits morphological and compositional characterization of the analyte and associated minerals prior to isotopic analysis, and (3) reveals patterns of variability homogenized by bulk techniques. Here we present new methods for in situ organic carbon isotope analysis with sub-permil precision and spatial resolution to 1 micron using SIMS, as well as new data acquired from a suite of Archean rocks. Three analytical protocols were developed for the CAMECA ims1280 at WiscSIMS to analyze domains of varying size and carbon concentration. Average reproducibility (at 2SD) using a 6 micron spot size with two Faraday cup detectors was 0.4 %, and 0.8 % for analyses using 1 micron and 3 micron spot sizes with a Faraday cup (for C-12) and an electron multiplier (for C-13). Eight coals, two ambers, a shungite, and a graphite were evaluated for micron-scale isotopic heterogeneity, and LCNN anthracite (delta C-13 = -23.56 +/- 0.1 %, 2SD) was chosen as the working standard. Correlation between instrumental bias and H/C was observed and calibrated for each analytical session using organic materials with H/C between 0.1 and 1.5 (atomic), allowing a correction based upon a C-13H/C-13 measurement included in every analysis. Matrix effects of variable C/SiO2 were evaluated by measuring mm to sub-micron graphite domains in quartzite from Bogala mine, Sri Lanka. Apparent instrumental bias and C-12 count rate are correlated in this case, but this may be related to a crystal orientation effect in graphite. Analyses of amorphous

  14. Triple isotope (δD, δ17O, δ18O) study on precipitation, drip water and speleothem fluid inclusions for a Western Central European cave (NW Switzerland)

    NASA Astrophysics Data System (ADS)

    Affolter, Stéphane; Häuselmann, Anamaria D.; Fleitmann, Dominik; Häuselmann, Philipp; Leuenberger, Markus

    2015-11-01

    Deuterium (δD) and oxygen (δ18O) isotopes are powerful tracers of the hydrological cycle and have been extensively used for paleoclimate reconstructions as they can provide information on past precipitation, temperature and atmospheric circulation. More recently, the use of 17Oexcess derived from precise measurement of δ17O and δ18O gives new and additional insights in tracing the hydrological cycle whereas uncertainties surround this proxy. However, 17Oexcess could provide additional information on the atmospheric conditions at the moisture source as well as about fractionations associated with transport and site processes. In this paper we trace water stable isotopes (δD, δ17O and δ18O) along their path from precipitation to cave drip water and finally to speleothem fluid inclusions for Milandre cave in northwestern Switzerland. A two year-long daily resolved precipitation isotope record close to the cave site is compared to collected cave drip water (3 months average resolution) and fluid inclusions of modern and Holocene stalagmites. Amount weighted mean δD, δ18O and δ17O are -71.0‰, -9.9‰, -5.2‰ for precipitation, -60.3‰, -8.7‰, -4.6‰ for cave drip water and -61.3‰, -8.3‰, -4.7‰ for recent fluid inclusions respectively. Second order parameters have also been derived in precipitation and drip water and present similar values with 18 per meg for 17Oexcess whereas d-excess is 1.5‰ more negative in drip water. Furthermore, the atmospheric signal is shifted towards enriched values in the drip water and fluid inclusions (Δ of ˜ + 10‰ for δD). The isotopic composition of cave drip water exhibits a weak seasonal signal which is shifted by around 8-10 months (groundwater residence time) when compared to the precipitation. Moreover, we carried out the first δ17O measurement in speleothem fluid inclusions, as well as the first comparison of the δ17O behaviour from the meteoric water to the fluid inclusions entrapment in speleothems

  15. Stable isotope (2H, 17O, 18O) and hydro chemical patterns of precipitation collected in weekly resolution at Hannover, Germany

    NASA Astrophysics Data System (ADS)

    Koeniger, Paul; Himmelsbach, Thomas

    2016-04-01

    Long-term observations of stable isotopes (δ18O and δ2H) in precipitation were initiated in May 2008 at the Federal Institute of Geosciences and Natural Resources (BGR) in Hannover, Germany. In 2014 all precipitation samples were re-analyzed because a purchase of a new laser spectrometer (Picarro L2140-i) now allowed measurements of δ17O and a calculation of the 17O-excess parameter. Starting in October 2015 a routine analysis of hydro chemical parameters was added whenever enough sample aliquot was available (major ions, trace elements). A discussion of the stable isotope data of the seven year series of weekly precipitation samples (n = 370) will be presented. Beneath general patterns (seasonality and trends) we also focus on importance of amount weighing procedures, corrections for minor rain amounts, aspects of sample storage and re-analyzes, as well as impacts through changes in analytical equipment (IRMS, CRD spectroscopy) which is visible from the data. For stable isotopes a Thermo Fisher delta plus IRMS (Gasbench and H-Device) was used until 2011 and from 2012 on a Picarro L2120-i water vapor analyzer with long-term accuracies for quality check samples better than 0.2‰ and 0.8‰ for δ18O and δ2H, respectively.

  16. Stable isotope (δ18O and δ2H) data for precipitation, stream water, and groundwater in Puerto Rico

    USGS Publications Warehouse

    Scholl, Martha A.; Torres-Sanchez, Angel; Rosario-Torres, Manuel

    2014-01-01

    Puerto Rico is located in the northeastern Caribbean Sea (18.2 °N, 66.3 °W), with the Atlantic Ocean on its northern coast. The U.S. Geological Survey’s Water, Energy, and Biogeochemical Budgets (WEBB) program study area in which most of these data were collected comprises the El Yunque National Forest and surrounding area of eastern Puerto Rico. Samples were collected in two forested watersheds, the Rio Mameyes and the Rio Icacos/Rio Blanco, on opposite sides of a ridge in the Luquillo Mountains on the eastern end of the island (fig. 1). Elevation in both watersheds ranges from sea level to approximately 1,000 meters (m). Near sea level, land use is mixed pasture, moist forest, and residential, grading to completely forested within the boundaries of El Yunque National Forest. Forest type changes with elevation from tabonuco to palo colorado to sierra palm to cloud forest above approximately 950 m (Murphy and others, 2012). The Rio Mameyes watershed is oriented north-northeast, and the basin is underlain by volcaniclastic bedrock (basaltic to andesitic volcanic sandstone/mudstone/conglomerate/breccia). The Rio Icacos/Rio Blanco watershed is oriented south-southeast. The Rio Icacos is one of the headwaters of the Rio Blanco and is underlain by quartz diorite. The lower Rio Blanco basin is underlain by andesitic volcaniclastic bedrock. This report also contains a long-term rain isotope dataset from the San Agustin site, in north-central Puerto Rico (fig. 1). Puerto Rico has a tropical climate dominated by easterly trade winds, and seasonal climate patterns affect the hydrology of the study area. The summer wet season is characterized by convective precipitation from tropical easterly waves, troughs, and cyclonic low-pressure systems, including tropical storms and hurricanes; in contrast, the drier winter season is characterized by trade-wind showers and frontal systems. The highest single-event rainfall totals tend to be associated with tropical storms

  17. Revisiting Mt. Kilimanjaro: Do n-alkane biomarkers in soils reflect the δ2H isotopic composition of precipitation?

    NASA Astrophysics Data System (ADS)

    Zech, M.; Zech, R.; Rozanski, K.; Hemp, A.; Gleixner, G.; Zech, W.

    2014-06-01

    During the last decade compound-specific deuterium (δ2H) analysis of plant leaf wax-derived n-alkanes has become a promising and popular tool in paleoclimate research. This is based on the widely accepted assumption that n-alkanes in soils and sediments generally reflect δ2H of precipitation (δ2Hprec). Recently, several authors suggested that δ2H of n-alkanes (δ2H,sub>n-alkanes) can also be used as proxy in paleoaltimetry studies. Here we present results from a δ2H transect study (~1500 to 4000 m a.s.l.) carried out on precipitation and soil samples taken from the humid southern slopes of Mt. Kilimanjaro. Contrary to earlier suggestions, a distinct altitude effect in δ2Hprec is present above ~2000 m a.s.l., i.e. δ2Hprec values become more negative with increasing altitude. The compound-specific δ2H values of nC27 and nC29 do not confirm this altitudinal trend, but rather become more positive both in the O-layers (organic layers) and the Ah-horizons (mineral topsoils). Although our δ2Hn-alkane results are in agreement with previously published results from the southern slopes of Mt. Kilimanjaro (Peterse et al., 2009, BG, 6, 2799-2807), a major re-interpretation is required given that the δ2Hn-alkane results do not reflect the δ2Hprec results. The theoretical framework for this re-interpretation is based on the evaporative isotopic enrichment of leaf water associated with transpiration process. Modelling results show that relative humidity, decreasing considerably along the southern slopes of Mt. Kilimanjaro (from 78% at ~ 2000 m a.s.l. to 51% at 4000 m a.s.l.), strongly controls δ2Hleaf water. The modelled δ2H leaf water enrichment along the altitudinal transect matches well the measured 2H leaf water enrichment as assessed by using the δ2Hprec and δ2Hn-alkane results and biosynthetic fractionation during n-alkane biosynthesis in leaves. Given that our results clearly demonstrate that n-alkanes in soils do not simply reflect δ2Hprec but rather δ2

  18. A Spatially Explicit Dual-Isotope Approach to Map Regions of Plant-Plant Interaction after Exotic Plant Invasion.

    PubMed

    Hellmann, Christine; Werner, Christiane; Oldeland, Jens

    2016-01-01

    Understanding interactions between native and invasive plant species in field settings and quantifying the impact of invaders in heterogeneous native ecosystems requires resolving the spatial scale on which these processes take place. Therefore, functional tracers are needed that enable resolving the alterations induced by exotic plant invasion in contrast to natural variation in a spatially explicit way. 15N isoscapes, i.e., spatially referenced representations of stable nitrogen isotopic signatures, have recently provided such a tracer. However, different processes, e.g. water, nitrogen or carbon cycles, may be affected at different spatial scales. Thus multi-isotope studies, by using different functional tracers, can potentially return a more integrated picture of invader impact. This is particularly true when isoscapes are submitted to statistical methods suitable to find homogeneous subgroups in multivariate data such as cluster analysis. Here, we used model-based clustering of spatially explicit foliar δ15N and δ13C isoscapes together with N concentration of a native indicator species, Corema album, to map regions of influence in a Portuguese dune ecosystem invaded by the N2-fixing Acacia longifolia. Cluster analysis identified regions with pronounced alterations in N budget and water use efficiency in the native species, with a more than twofold increase in foliar N, and δ13C and δ15N enrichment of up to 2‰ and 8‰ closer to the invader, respectively. Furthermore, clusters of multiple functional tracers indicated a spatial shift from facilitation through N addition in the proximity of the invader to competition for resources other than N in close contact. Finding homogeneous subgroups in multi-isotope data by means of model-based cluster analysis provided an effective tool for detecting spatial structure in processes affecting plant physiology and performance. The proposed method can give an objective measure of the spatial extent of influence of

  19. A Spatially Explicit Dual-Isotope Approach to Map Regions of Plant-Plant Interaction after Exotic Plant Invasion

    PubMed Central

    Hellmann, Christine; Werner, Christiane; Oldeland, Jens

    2016-01-01

    Understanding interactions between native and invasive plant species in field settings and quantifying the impact of invaders in heterogeneous native ecosystems requires resolving the spatial scale on which these processes take place. Therefore, functional tracers are needed that enable resolving the alterations induced by exotic plant invasion in contrast to natural variation in a spatially explicit way. 15N isoscapes, i.e., spatially referenced representations of stable nitrogen isotopic signatures, have recently provided such a tracer. However, different processes, e.g. water, nitrogen or carbon cycles, may be affected at different spatial scales. Thus multi-isotope studies, by using different functional tracers, can potentially return a more integrated picture of invader impact. This is particularly true when isoscapes are submitted to statistical methods suitable to find homogeneous subgroups in multivariate data such as cluster analysis. Here, we used model-based clustering of spatially explicit foliar δ15N and δ13C isoscapes together with N concentration of a native indicator species, Corema album, to map regions of influence in a Portuguese dune ecosystem invaded by the N2-fixing Acacia longifolia. Cluster analysis identified regions with pronounced alterations in N budget and water use efficiency in the native species, with a more than twofold increase in foliar N, and δ13C and δ15N enrichment of up to 2‰ and 8‰ closer to the invader, respectively. Furthermore, clusters of multiple functional tracers indicated a spatial shift from facilitation through N addition in the proximity of the invader to competition for resources other than N in close contact. Finding homogeneous subgroups in multi-isotope data by means of model-based cluster analysis provided an effective tool for detecting spatial structure in processes affecting plant physiology and performance. The proposed method can give an objective measure of the spatial extent of influence of

  20. Spatial extremes modeling applied to extreme precipitation data in the state of Paraná

    NASA Astrophysics Data System (ADS)

    Olinda, R. A.; Blanchet, J.; dos Santos, C. A. C.; Ozaki, V. A.; Ribeiro, P. J., Jr.

    2014-11-01

    Most of the mathematical models developed for rare events are based on probabilistic models for extremes. Although the tools for statistical modeling of univariate and multivariate extremes are well developed, the extension of these tools to model spatial extremes includes an area of very active research nowadays. A natural approach to such a modeling is the theory of extreme spatial and the max-stable process, characterized by the extension of infinite dimensions of multivariate extreme value theory, and making it possible then to incorporate the existing correlation functions in geostatistics and therefore verify the extremal dependence by means of the extreme coefficient and the Madogram. This work describes the application of such processes in modeling the spatial maximum dependence of maximum monthly rainfall from the state of Paraná, based on historical series observed in weather stations. The proposed models consider the Euclidean space and a transformation referred to as space weather, which may explain the presence of directional effects resulting from synoptic weather patterns. This method is based on the theorem proposed for de Haan and on the models of Smith and Schlather. The isotropic and anisotropic behavior of these models is also verified via Monte Carlo simulation. Estimates are made through pairwise likelihood maximum and the models are compared using the Takeuchi Information Criterion. By modeling the dependence of spatial maxima, applied to maximum monthly rainfall data from the state of Paraná, it was possible to identify directional effects resulting from meteorological phenomena, which, in turn, are important for proper management of risks and environmental disasters in countries with its economy heavily dependent on agribusiness.

  1. Broad-spectrum monitoring strategies for predicting occult precipitation contribution to water balance in a coastal watershed in California: Ground-truthing, areal monitoring and isotopic analysis of fog in the San Francisco Bay region

    NASA Astrophysics Data System (ADS)

    Koohafkan, M.; Thompson, S. E.; Leonardson, R.; Dufour, A.

    2013-12-01

    We showcase a fog monitoring study designed to quantitatively estimate the contribution of summer fog events to the water balance of a coastal watershed managed by the San Francisco Public Utilities Commission. Two decades of research now clearly show that fog and occult precipitation can be major contributors to the water balance of watersheds worldwide. Monitoring, understanding and predicting occult precipitation is therefore as hydrologically compelling as forecasting precipitation or evaporation, particularly in the face of climate variability. We combine ground-based monitoring and collection strategies with remote sensing technologies, time-lapse imagery, and isotope analysis to trace the ';signature' of fog in physical and ecological processes. Spatial coverage and duration of fog events in the watershed is monitored using time-lapse cameras and leaf wetness sensors strategically positioned to provide estimates of the fog bank extent and cloud base elevation, and this fine-scale data is used to estimate transpiration suppression by fog and is examined in the context of regional climate through the use of satellite imagery. Soil moisture sensors, throughfall collectors and advective fog collectors deployed throughout the watershed provide quantitative estimates of fog drip contribution to soil moisture and plants. Fog incidence records and streamflow monitoring provide daily estimates of fog contribution to streamflow. Isotope analysis of soil water, fog drip, stream water and vegetation samples are used to probe for evidence of direct root and leaf uptake of fog drip by plants. Using this diversity of fog monitoring methods, we develop an empirical framework for the inclusion of fog processes in water balance models.

  2. Stable isotope compositions of carbonate and inclusion-hosted water 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; Shen, Chuan-Chou; Vennemann, Torsten

    2016-04-01

    Studies on the last interglacial (LIG) can provide information on how our environment behaved in a period of slightly higher global temperatures at about 120 ka compared to the current climate conditions. This paper presents complex stable H-C-O isotope records obtained for carbonate and fluid inclusion hosted water of U-Th dated stalagmites from the Baradla Cave system in Central Europe. Comparing 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 the well known 120 ka climate optimum and the subsequent cooling starting at about 118 ka, the δD values show a negative peak at about 124-125 ka that does not appear in the C-O isotope data. This negative peak fits well to temperature and humidity changes inferred from proxy records from the northern Atlantic to the eastern Mediterranean. Spatial distributions of these variables show, that while the northern Atlantic ocean experienced a cold phase (possibly also dry in NW Europe), the Mediterranean region was characterized by warm, humid conditions and enhanced seasonality, most probably related to a freshwater flux to the North Atlantic and consequent large-scale heat and moisture transport changes affecting the Mediterranean. The combined interpretation of H-C-O isotope data revealed that the Alpine and Mediterranean regions behaved differently again during Greenland Stadial 26 (GS26, ~119 to 115.5 ka). While the Alpine records fluctuated in close agreement with the Central Greenland ice core δ18O data, the BAR-II stalagmite and southern European records

  3. Spatial and Temporal Frequency of Shallow Landsliding Across a Steep Precipitation Gradient in the Hanalei River Basin

    NASA Astrophysics Data System (ADS)

    Huppert, K. L.; Ferrier, K.; Perron, T.

    2010-12-01

    Shallow landslides play a major role in the denudation of many steep, soil-mantled landscapes. The occurrence of shallow landsliding is thought to depend on precipitation, which saturates soil and reduces its frictional strength. The Hanalei River basin, on the northern side of Kauai, is an ideal location to study the effects of precipitation on shallow landsliding because it has one of the steepest rainfall gradients in the world. Mean annual precipitation rates range from 11 m yr-1 at Mt. Wai’ale’ale at the basin’s headwaters to less than 2 m yr-1 in subbasins near the coast, 15 km north of the headwaters. The topography of the Hanalei basin also varies considerably along the length of the basin, with mean hillslope gradients ranging from roughly 20 degrees in the coastal subcatchments to approximately 45 degrees in the headwater subcatchments. We aimed to measure variations in the spatial and temporal frequency of shallow landsliding along the rainfall gradient in the Hanalei basin by mapping shallow landslide scars in a series of satellite images, aerial photographs, and LiDAR topography. Using a 2005 Quickbird satellite mosaic of Hanalei basin, color-modified to accentuate regions of exposed soil, we identified 1022 shallow landslide scars in the basin. Mapped landslide scars in this inventory range in size from 22 m2 to 9265 m2 with a median of 225 m2, and scar areas are fit well by a lognormal distribution with a mean of 385 m2. The spatial density of landslide scars is suggestive of a threshold in landslide occurrence; the gentler, drier subcatchments closest to the coast contain no landslide scars, but the steeper, wetter subcatchments further upstream contain abundant scars with a density as high as 7300 m2 km-2. However, within the subcatchments that contain landslide scars, there appears to be no trend in the spatial density of landslide scars with mean hillslope gradient or with mean annual precipitation. To estimate the temporal frequency of

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

    PubMed Central

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

    2012-01-01

    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 δ18O correlates strongly with δ18O in precipitation from distant stations in the center and west of the basin, and with Andean ice core δ18O 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 δ18O over the 20th century consistent with increases in Andean δ18O 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. PMID:23027960

  5. Compound-specific isotopic analyses track changes in seasonal precipitation regimes in the Northeastern United States at ca 8200 cal yr BP

    NASA Astrophysics Data System (ADS)

    Shuman, Bryan; Huang, Yongsong; Newby, Paige; Wang, Yi

    2006-11-01

    We analyzed the hydrogen isotopic composition of sedimentary leaf wax (C 28n-acid) and palmitic acid (C 16n-acid) in cores from Berry and Crooked Ponds in Massachusetts. The results show a dramatic positive shift in leaf wax δD values around 8200 cal yr BP, when regional lake levels rose and plant communities shifted in favor of plants intolerant of dry conditions. To aid our interpretation, we studied modern lake sediment samples and found that the δD values of leaf wax and palmitic acid record the hydrogen isotopic composition of water available during the synthesis of these compounds. Palmitic acid δD values follow lake water values often derived from winter precipitation, and leaf wax δD values track the water available to terrestrial plants during the growing season. Based on these results, we interpret the downcore isotopic shift as an increase in the fraction of precipitation falling during the growing season. The increase coincides with evidence from pollen and palmitic acid δD values for a multi-century period of cold conditions at ca 8200 cal yr BP. The close timing of the brief cool period and a step-change in summer precipitation levels in the northeastern United States is consistent with the hypothesis that the collapse of the Laurentide ice sheet occurred in association with cold North Atlantic conditions from 8400 to 8000 cal yr BP. The location of the northeastern US downwind of the ice sheet and close to the North Atlantic makes it sensitive to both factors. Our results also provide insight into later changes in the northeastern US because they indicate a progressive decrease in summer precipitation levels after ca 8000 cal yr BP.

  6. Understanding Spatial and Temporal Variations of Arctic Circulation Using Oxygen Isotopes of Seawater

    NASA Astrophysics Data System (ADS)

    Yin, L.; Kopans-Johnson, C. R.; LeGrande, A. N.; Kelly, S.

    2015-12-01

    The isotopic ratio of 18O to 16O in seawater (2005ppm in ocean water is defined as 𝛿18Oseawater≡0 permil or 0‰) is a fundamental ocean tracer due to its distinct linear relationship with salinity(𝛿18O -S) from regional inland freshwater sources. As opposed to salinity alone, 𝛿18O distinguishes river runoff from sea-ice melt and traces ocean circulation pathways from coastal to open waters and surface to deep waters. Observations from the past 60 years of 𝛿18O seawater were compiled into a database by Schimdt et al. (1999), and subsequently used to calculate a 3-dimensional 1°x1° 𝛿18O global gridded dataset by LeGrande and Schmidt (2006). Although the Schmidt et al. (1999) Global Seawater Oxygen-18 Database (𝛿18Oobs) contains 25,514 measurements used to calculate the global gridded dataset, LeGrande and Schmidt (2006) point out that, "data coverage varies greatly from region to region," with seasonal variability creating biases in areas where sea ice is present. Python Pandas is used to automate the addition of 2,942 records to the Schmidt et al. (1999) Global Seawater Oxygen-18 Database (𝛿18Oobs), and examine the spatial and temporal distributions of 18O in the Arctic Ocean. 10 initial water masses are defined using spatial and temporal trends, clusters of observations, and Arctic surface circulation. Jackknife slope analysis of water mass 𝛿18O -S is used to determine anomalous data points and regional hydrology, resulting in 4 distinct Arctic water masses. These techniques are used to improve the gridded 𝛿18Oseawater dataset by distinguishing unique water masses, and accounting for seasonal variability of complex high latitude areas.

  7. Modeling the spatial impact of an invasive N2-fixing Acacia by means of isotopic and optical measurements

    NASA Astrophysics Data System (ADS)

    Hellmann, Christine; Große-Stoltenberg, André; Máguas, Cristina; Oldeland, Jens; Rascher, Katherine G.; Thiele, Jan; Werner, Christiane

    2014-05-01

    Invasions by exotic plant species are known to seriously alter biogeochemical cycles and ecosystem functioning of the systems they invade, with nitrogen fixing species being among the most problematic invaders. However, explicitly quantifying such alterations remains challenging, as methods are lacking to capture the spatial scale of impact. Here, we present a spatially explicit approach allowing to quantify the impact of an N2-fixing invasive species, Acacia longifolia, on a native Portuguese dune system by means of stable isotope analyses. 15N isotopic signatures (δ15N) differed strongly between the native system (δ15N c. -10 o) and atmospherically derived N in A. longifolia (δ15N c. 0 o). Thus, N sources for a native, non-fixing plant, Corema album, could be readily distinguished. Using georeferenced δ15N values of C. album, we could accurately map N introduced by A. longifolia on a spatial scale. N input exceeded the canopy of the N2 fixer by far and reached up to 8 m into the uninvaded vegetation. The area altered by invasion was c. 3.5 fold larger than the area covered by the invader's canopy. Our results highlight that spatially explicit measurements of sensitive ecological tracers like stable isotopic signatures, i.e. isoscapes, provide a valuable means to quantify alterations of biogeochemical cycles within plant communities. Moreover, linking stable isotopes with optical measurements and remote sensing can be a powerful tool to upscale such information from leaf- to larger spatial scales. Here we show that foliar δ15N signatures can be accurately modeled using leaf reflectance spectra. This approach opens promising future perspectives in ecosystem monitoring based on the potential use of hyperspectral aerial and satellite imagery.

  8. Silicon isotope fractionation during the precipitation of quartz and the adsorption of H4SiO4(aq) on Fe(Ⅲ)-oxyhydroxide surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Y.; He, H.; Zhang, S.

    2015-12-01

    Equilibrium Si isotope fractionation factors among orthosilicic acid (i.e.,H4SiO4(aq)), quartz and the adsorption complexes of H4SiO4(aq) on Fe (Ⅲ)-oxyhydroxide surface were calculated using the full-electron wave-function quantum chemistry methods (i.e., B3LYP/6-311G(2df,p)) with a new cluster-model-based treatment. Solvation effects were carefully included in our calculations via water-droplet method combined with implicit solvent models (e.g., PCM). The results revealed that, if it is under equilibrium conditions, heavy Si isotopes would be significantly enriched in quartz in comparison to H4SiO4(aq). However, most of the field observations suggested that quartz would have identical or even depleted d30Si values compared to that of H4SiO4(aq). To explain this discrepancy between the equilibrium calculation results and the field observations, the kinetic isotope effect (KIE) associated with the formation of amorphous silica, which usually is the precursor of crystalline quartz, was investigated using quantum chemistry methods. The KIE results showed that amorphous silica would be significantly enriched in light Si isotopes during its formation. Our equilibrium fractionation results, however, matched a special type of quartz (i.e., Herkimer "diamond") very well, due to its nearly equilibrated precipitation condition. Opposite to the case of precipitated quartz, a large equilibrium Si isotope fractionation (i.e., -3.0‰) was found between the absorbed bidentate Si surface complexes (i.e., 2C>Fe2O2Si(OH)2) and H4SiO4(aq). This calculated equilibrium Si isotope fractionation factor largely differed from a previous experimental result (ca. -1.08‰). We found that the formation of transient or temporary surface complexes (e.g., 1V>Fe2OSi(OH)3) may have accounted for the smaller net fractionation observed. With the equilibrium and kinetic Si isotope fractionation factors provided here, the distributions and changes of Si isotope compositions in the Earth's surface

  9. Temporal and Spatial Pattern of Changes of Extreme Precipitation in the Middle and Lower Yangtze River Basin (YRB) during 1960 to 2012

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Wu, S.; Wen, J.; Xu, M.; Tan, J.

    2013-12-01

    The Yangtze River is the longest river in China, with its river basin covering an area of 1.8 million sq km, encompassing about one fifth of China's total territory, one third of the nation's total population, and one quarter of its total arable land. Flooding resulted from extreme precipitation has always been a major problem for the middle and lower part of the YRB, particularly during the monsoon season of eastern China from May to August. Meanwhile, the relatively dense population and large cities in this region make the floods more deadly and costly. In this study we aim to establish the temporal and spatial patterns of changes in extreme precipitation in the middle and lower YRB using daily precipitation data from 71 stations in the area from 1960 to 2012. It is hoped that this study will provide useful information for better flood control. In this study, we defined and examined three major indices. Extreme precipitation frequency is defined as number of days per year with precipitation exceeding the 95th percentile for the base period of 1961 - 1990. Extreme precipitation amount is defined as the total amount of precipitation from these days. Extreme precipitation intensity is defined as the amount divided by frequency. We used non-parametric Thiel-Sen method to estimate the rate of change at each station, and Mann-Kendall test for the significance of the trend. Using Thiessen polygons, we also calculated the area-weighted mean of station trends to get the total trend for the entire study area. Abrupt changes in the time series was detected by using Mann-Kendall test and the Moving-t test methods. Our results show that there is an increasing trend of for the frequency, amount, and intensity of extreme precipitation in the study region. Of the three indicators, the extreme precipitation amount increased most, and its abrupt change point happened in1987. Between the period before and after 1987, the mean annual amount, intensity and frequency of extreme

  10. Determining Spatial and Temporal Variation in Sources of Nitrogen Deposition in the Rocky Mountains using Nitrogen Isotopes

    NASA Astrophysics Data System (ADS)

    Nanus, L.; Campbell, D. H.; Ingersoll, G.; Lehmann, C.; Kendall, C.; Elliott, E. M.; Bohlke, J. K.

    2009-12-01

    Variations in nitrogen (N) deposition sources to high-elevation ecosystems in the Rocky Mountains were evaluated using spatially and temporally distributed N isotope data for water years 1995-2006. This unique dataset links N in wet deposition and snowpack to source emissions, and enhances understanding of the impacts of anthropogenic activities and environmental policies that affect N cycling in the Rocky Mountains. At 50 U.S. Geological Survey-Rocky Mountain Snowpack(USGS-RMS) sites, d15N(NO3) ranged from -3.3 permil to +6.5 permil, with a mean value of +1.4 permil for 2006. At 15 National Atmospheric Deposition Program/National Trends Network(NADP/NTN) wet-deposition sites in the Rocky Mountains, d15N(NO3) values ranged from -7.6 permil to +5.5 permil with a mean value of +0.7 permil during the cool season. The wet deposition values generally had lower d15N(NO3) values than snowpack, possibly due to the influence of dry deposition in the snowpack samples. Spatial patterns in d15N(NO3) are similar for NADP/NTN wet-only deposition and USGS-RMS winter snowpack for water year 2006, with higher d15N(NO3) values and increased NO3 concentrations in the Southern Rockies, where there are larger anthropogenic N emission sources compared to the Northern Rockies. Temporal trends in annual snowpack d15N(NO3) from USGS-RMS for 1995-2006 indicate that source signatures changed over time. Regional-Kendall statistical tests for d15N(NO3) indicate a highly significant positive temporal trend in the Southern Rockies (p = 0.006, median d15N(NO3) = +2.3 permil), a moderately significant positive trend in the Central Rockies (p = 0.08, median d15N(NO3) = -1.1 permil), and no trend in Northern Rockies (p = 1, median d15N(NO3) = -4.0 permil). Quarterly, volume-weighted mean d15N(NO3) values of precipitation at NADP/NTN sites show a strong seasonal pattern due to variation in the proportion of N originating from source regions at different times of the year due to seasonal changes in

  11. The creation of future daily gridded datasets of precipitation and temperature with a spatial weather generator, Cyprus 2020-2050

    NASA Astrophysics Data System (ADS)

    Camera, Corrado; Bruggeman, Adriana; Hadjinicolaou, Panos; Pashiardis, Stelios; Lange, Manfred

    2014-05-01

    High-resolution gridded daily datasets are essential for natural resource management and the analysis of climate changes and their effects. This study aimed to create gridded datasets of daily precipitation and daily minimum and maximum temperature, for the future (2020-2050). The horizontal resolution of the developed datasets is 1 x 1 km2, covering the area under control of the Republic of Cyprus (5.760 km2). The study is divided into two parts. The first consists of the evaluation of the performance of different interpolation techniques for daily rainfall and temperature data (1980-2010) for the creation of the gridded datasets. Rainfall data recorded at 145 stations and temperature data from 34 stations were used. For precipitation, inverse distance weighting (IDW) performs best for local events, while a combination of step-wise geographically weighted regression and IDW proves to be the best method for large scale events. For minimum and maximum temperature, a combination of step-wise linear multiple regression and thin plate splines is recognized as the best method. Six Regional Climate Models (RCMs) for the A1B SRES emission scenario from the EU ENSEMBLE project database were selected as sources for future climate projections. The RCMs were evaluated for their capacity to simulate Cyprus climatology for the period 1980-2010. Data for the period 2020-2050 from the three best performing RCMs were downscaled, using the change factors approach, at the location of observational stations. Daily time series were created with a stochastic rainfall and temperature generator. The RainSim V3 software (Burton et al., 2008) was used to generate spatial-temporal coherent rainfall fields. The temperature generator was developed in R and modeled temperature as a weakly stationary process with the daily mean and standard deviation conditioned on the wet and dry state of the day (Richardson, 1981). Finally gridded datasets depicting projected future climate conditions were

  12. Stochastic spatial disaggregation of extreme precipitation to validate a regional climate model and to evaluate climate change impacts over a small watershed

    NASA Astrophysics Data System (ADS)

    Gagnon, P.; Rousseau, A. N.

    2014-05-01

    Regional climate models (RCMs) are valuable tools to evaluate impacts of climate change (CC) at regional scale. However, as the size of the area of interest decreases, the ability of a RCM to simulate extreme precipitation events decreases due to the spatial resolution. Thus, it is difficult to evaluate whether a RCM bias on localized extreme precipitation is caused by the spatial resolution or by a misrepresentation of the physical processes in the model. Thereby, it is difficult to trust the CC impact projections for localized extreme precipitation. Stochastic spatial disaggregation models can bring the RCM precipitation data at a finer scale and reduce the bias caused by spatial resolution. In addition, disaggregation models can generate an ensemble of outputs, producing an interval of possible values instead of a unique discrete value. The objective of this work is to evaluate whether a stochastic spatial disaggregation model applied on annual maximum daily precipitation (i) enables the validation of a RCM for a period of reference, and (ii) modifies the evaluation of CC impacts over a small area. Three simulations of the Canadian RCM (CRCM) covering the period 1961-2099 are used over a small watershed (130 km2) located in southern Québec, Canada. The disaggregation model applied is based on Gibbs sampling and accounts for physical properties of the event (wind speed, wind direction, and convective available potential energy - CAPE), leading to realistic spatial distributions of precipitation. The results indicate that disaggregation has a significant impact on the validation. However, it does not provide a precise estimate of the simulation bias because of the difference in resolution between disaggregated values (4 km) and observations, and because of the underestimation of the spatial variability by the disaggregation model for the most convective events. Nevertheless, disaggregation illustrates that the simulations used mostly overestimated annual maximum

  13. Stochastic spatial disaggregation of extreme precipitation to validate a Regional Climate Model and to evaluate climate change impacts over a small watershed

    NASA Astrophysics Data System (ADS)

    Gagnon, P.; Rousseau, A. N.

    2013-06-01

    Regional Climate Models (RCMs) are valuable tools to evaluate impacts of climate change (CC) at regional scale. However, as the size of the area of interest decreases, the ability of a RCM to simulate extreme precipitation events decreases due to the spatial resolution. Thus, it is difficult to evaluate whether a RCM bias on localized extreme precipitation is caused by the spatial resolution or by a misrepresentation of the physical processes in the model. Thereby, it is difficult to trust the CC impact projections for localized extreme precipitation. Stochastic spatial disaggregation models can bring the RCM precipitation data at a finer scale and reduce the bias caused by spatial resolution. In addition, disaggregation models can generate an ensemble of outputs, producing an interval of possible values instead of a unique discrete value. The objective of this work is to evaluate whether a stochastic spatial disaggregation model applied on annual maximum daily precipitation: (i) enables the validation of a RCM for a period of reference, and (ii) modifies the evaluation of CC impacts over a small area. Three simulations of the Canadian RCM (CRCM) covering the period 1961-2099 are used over a small watershed (130 km2) located in southern Québec, Canada. The disaggregation model applied is based on Gibbs sampling and accounts for physical properties of the event (wind speed, wind direction, and convective available potential energy (CAPE)), leading to realistic spatial distributions of precipitation. The results indicate that disaggregation has a significant impact on the validation. However it does not provide a precise estimate of the simulation bias because of the difference in resolution between disaggregated values (4 km) and observations, and because of the underestimation of the spatial variability by the disaggregation model for the most convective events. Nevertheless, disaggregation permits to determine that the simulations used mostly overestimated annual

  14. Precipitation induced stream flow: An event based chemical and isotopic study of a small stream in the Great Plains region of the USA

    USGS Publications Warehouse

    Machavaram, M.V.; Whittemore, D.O.; Conrad, M.E.; Miller, N.L.

    2006-01-01

    A small stream in the Great Plains of USA was sampled to understand the streamflow components following intense precipitation and the influence of water storage structures in the drainage basin. Precipitation, stream, ponds, ground-water and soil moisture were sampled for determination of isotopic (D, 18O) and chemical (Cl, SO4) composition before and after two intense rain events. Following the first storm event, flow at the downstream locations was generated primarily through shallow subsurface flow and runoff whereas in the headwaters region - where a pond is located in the stream channel - shallow ground-water and pond outflow contributed to the flow. The distinct isotopic signatures of precipitation and the evaporated pond water allowed separation of the event water from the other sources that contributed to the flow. Similarly, variations in the Cl and SO4 concentrations helped identify the relative contributions of ground-water and soil moisture to the streamflow. The relationship between deuterium excess and Cl or SO4 content reveals that the early contributions from a rain event to streamflow depend upon the antecedent climatic conditions and the position along the stream channel within the watershed. The design of this study, in which data from several locations within a watershed were collected, shows that in small streams changes in relative contributions from ground water and soil moisture complicate hydrograph separation, with surface-water bodies providing additional complexity. It also demonstrates the usefulness of combined chemical and isotopic methods in hydrologic investigations, especially the utility of the deuterium excess parameter in quantifying the relative contributions of various source components to the stream flow. ?? 2006 Elsevier B.V. All rights reserved.

  15. High Spatial Resolution Forecasting of Long-Term Monthly Precipitation and Mean Temperature Trends in Data Scarce Regions

    NASA Astrophysics Data System (ADS)

    Mosier, T. M.; Hill, D. F.; Sharp, K. V.

    2013-12-01

    High spatial resolution time-series data are critical for many hydrological and earth science studies. Multiple groups have developed historical and forecast datasets of high-resolution monthly time-series for regions of the world such as the United States (e.g. PRISM for hindcast data and MACA for long-term forecasts); however, analogous datasets have not been available for most data scarce regions. The current work fills this data need by producing and freely distributing hindcast and forecast time-series datasets of monthly precipitation and mean temperature for all global land surfaces, gridded at a 30 arc-second resolution. The hindcast data are constructed through a Delta downscaling method, using as inputs 0.5 degree monthly time-series and 30 arc-second climatology global weather datasets developed by Willmott & Matsuura and WorldClim, respectively. The forecast data are formulated using a similar downscaling method, but with an additional step to remove bias from the climate variable's probability distribution over each region of interest. The downscaling package is designed to be compatible with a number of general circulation models (GCM) (e.g. with GCMs developed for the IPCC AR4 report and CMIP5), and is presently implemented using time-series data from the NCAR CESM1 model in conjunction with 30 arc-second future decadal climatologies distributed by the Consultative Group on International Agricultural Research. The resulting downscaled datasets are 30 arc-second time-series forecasts of monthly precipitation and mean temperature available for all global land areas. As an example of these data, historical and forecast 30 arc-second monthly time-series from 1950 through 2070 are created and analyzed for the region encompassing Pakistan. For this case study, forecast datasets corresponding to the future representative concentration pathways 45 and 85 scenarios developed by the IPCC are presented and compared. This exercise highlights a range of potential

  16. Spatial downscaling and mapping of daily precipitation and air temperature using daily station data and monthly mean maps

    NASA Astrophysics Data System (ADS)

    Flint, A. L.; Flint, L. E.; Stern, M. A.

    2013-12-01

    Accurate maps of daily weather variables are an essential component of hydrologic and ecologic modeling. Here we present a four-step method that uses daily station data and transient monthly maps of precipitation and air temperature. This method uses the monthly maps to help interpolate between stations for more accurate production of daily maps at any spatial resolution. The first step analyzes the quality of the each station's data using a discrepancy analysis that compares statistics derived from a statistical jack-knifing approach with a time-series evaluation of discrepancies generated for each station. Although several methods could be used for the second step of producing initial maps, such as kriging, splines, etc., we used a gradient plus inverse distance squared method that was developed to produce accurate climate maps for sparse data regions with widely separated and few climate stations, far fewer than would be needed for techniques such as kriging. The gradient plus inverse distance squared method uses local gradients in the climate parameters, easting, northing, and elevation, to adjust the inverse distance squared estimates for local gradients such as lapse rates, inversions, or rain shadows at scales of 10's of meters to kilometers. The third step is to downscale World Wide Web (web) based transient monthly data, such as Precipitation-Elevation Regression on Independent Slope Method (PRISM) for the US (4 km or 800 m maps) or Climate Research Unit (CRU 3.1) data sets (40 km for global applications) to the scale of the daily data's digital elevation model. In the final step the downscaled transient monthly maps are used to adjust the daily time-series mapped data (~30 maps/month) for each month. These adjustments are used to scale daily maps so that summing them for precipitation or averaging them for temperature would more accurately reproduce the variability in selected monthly maps. This method allows for individual days to have maxima or minima

  17. Reconstructing lake evaporation history and the isotopic composition of precipitation by a coupled δ18O-δ2H biomarker approach

    NASA Astrophysics Data System (ADS)

    Hepp, Johannes; Tuthorn, Mario; Zech, Roland; Mügler, Ines; Schlütz, Frank; Zech, Wolfgang; Zech, Michael

    2015-10-01

    Over the past decades, δ18O and δ2H analyses of lacustrine sediments became an invaluable tool in paleohydrology and paleolimnology for reconstructing the isotopic composition of past lake water and precipitation. However, based on δ18O or δ2H records alone, it can be challenging to distinguish between changes of the precipitation signal and changes caused by evaporation. Here we propose a coupled δ18O-δ2H biomarker approach that provides the possibility to disentangle between these two factors. The isotopic composition of long chain n-alkanes (n-C25, n-C27, n-C29, n-C31) were analyzed in order to establish a 16 ka Late Glacial and Holocene δ2H record for the sediment archive of Lake Panch Pokhari in High Himalaya, Nepal. The δ2Hn-alkane record generally corroborates a previously established δ18Osugar record reporting on high values characterizing the deglaciation and the Older and the Younger Dryas, and low values characterizing the Bølling and the Allerød periods. Since the investigated n-alkane and sugar biomarkers are considered to be primarily of aquatic origin, they were used to reconstruct the isotopic composition of lake water. The reconstructed deuterium excess of lake water ranges from +57‰ to -85‰ and is shown to serve as proxy for the evaporation history of Lake Panch Pokhari. Lake desiccation during the deglaciation, the Older Dryas and the Younger Dryas is affirmed by a multi-proxy approach using the Hydrogen Index (HI) and the carbon to nitrogen ratio (C/N) as additional proxies for lake sediment organic matter mineralization. Furthermore, the coupled δ18O and δ2H approach allows disentangling the lake water isotopic enrichment from variations of the isotopic composition of precipitation. The reconstructed 16 ka δ18Oprecipitation record of Lake Panch Pokhari is well in agreement with the δ18O records of Chinese speleothems and presumably reflects the Indian Summer Monsoon variability.

  18. Carbon and hydrogen isotope composition of plant biomarkers from lake sediments as proxies for precipitation changes across Heinrich Events in the subtropics

    NASA Astrophysics Data System (ADS)

    Arnold, T. E.; Diefendorf, A. F.; Brenner, M.; Freeman, K. H.; Curtis, J. H.

    2015-12-01

    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

  19. Applying Two Binned Methods to the Simple Biosphere Model (SiB) for Improving the Representation of Spatially Varying Precipitation and Soil Wetness

    NASA Astrophysics Data System (ADS)

    Medina, I. D.; Denning, A.

    2011-12-01

    Representing subgrid-scale variability is a continuing challenge for modelers, but is crucial for accurately calculating the exchanges of energy, moisture, and momentum between the land surface and atmospheric boundary layer. Soil wetness is highly spatially variable and difficult to resolve at grid length scales (~100 km) used in General Circulation Models (GCMs). Currently, GCMs use an area average precipitation rate that results in a single soil wetness value for the entire grid area, and due to the highly nonlinear relationship between soil wetness and evapotranspiration, significant inaccuracies arise in the calculation of the grid area latent heat flux. Using a finer GCM resolution will not solve this problem completely, and other methods of modeling need to be considered. For this study, the binned and alternative binned method of Sellers et al. (2007) are applied to the Simple Biosphere Model (SiB) for improving the representation of spatially varying precipitation, soil wetness and surface-atmosphere fluxes. The methods are tested in a dry, semi-arid, and wet biome for two off-line precipitation distribution experiments, and results are compared to an explicit method, which is ideal for resolving subgrid-scale variability, and the bulk method (area averaged), which is currently in use with GCMs. Results indicate that the alternative binned method better captures the spatial variability in soil wetness 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.

  20. Post-processing ECMWF precipitation and temperature ensemble reforecasts for operational hydrologic forecasting at various spatial scales

    NASA Astrophysics Data System (ADS)

    Verkade, J. S.; Brown, J. D.; Reggiani, P.; Weerts, A. H.

    2013-09-01

    The ECMWF temperature and precipitation ensemble reforecasts are evaluated for biases in the mean, spread and forecast probabilities, and how these biases propagate to streamflow ensemble forecasts. The forcing ensembles are subsequently post-processed to reduce bias and increase skill, and to investigate whether this leads to improved streamflow ensemble forecasts. Multiple post-processing techniques are used: quantile-to-quantile transform, linear regression with an assumption of bivariate normality and logistic regression. Both the raw and post-processed ensembles are run through a hydrologic model of the river Rhine to create streamflow ensembles. The results are compared using multiple verification metrics and skill scores: relative mean error, Brier skill score and its decompositions, mean continuous ranked probability skill score and its decomposition, and the ROC score. Verification of the streamflow ensembles is performed at multiple spatial scales: relatively small headwater basins, large tributaries and the Rhine outlet at Lobith. The streamflow ensembles are verified against simulated streamflow, in order to isolate the effects of biases in the forcing ensembles and any improvements therein. The results indicate that the forcing ensembles contain significant biases, and that these cascade to the streamflow ensembles. Some of the bias in the forcing ensembles is unconditional in nature; this was resolved by a simple quantile-to-quantile transform. Improvements in conditional bias and skill of the forcing ensembles vary with forecast lead time, amount, and spatial scale, but are generally moderate. The translation to streamflow forecast skill is further muted, and several explanations are considered, including limitations in the modelling of the space-time covariability of the forcing ensembles and the presence of storages.

  1. A study on the intra-annual variation and the spatial distribution of precipitation amount and duration over Greece on a 10 day basis

    NASA Astrophysics Data System (ADS)

    Bartzokas, A.; Lolis, C. J.; Metaxas, D. A.

    2003-02-01

    The intra-annual variation of precipitation amount and duration and their spatial distribution during the year are studied on a 10 day basis for the Greek region, using S-mode and T-mode factor analysis. (i) For the intra-annual variation of precipitation amount, two modes were revealed: the first shows one broad maximum during the conventional winter in stations affected by the sea; the second presents two maxima, the first during late autumn-early winter and the second during late spring, corresponding to the northern mainland stations. (ii) For the spatial distribution of precipitation, three main patterns were revealed: the first one is the winter pattern, with the maximum over the west windward area; the second is the summer pattern, with a maximum over the north inland region; and the third is the autumn pattern, with the maximum over northwestern Greece. (iii) For precipitation duration, two types of intra-annual variation were revealed. The first one is similar to the first of the analysis for precipitation amount; the second presents two maxima, the first during the beginning of December and the second during the middle of February, corresponding to the areas of northwestern and northeastern Greece. (iv) For the spatial distribution of precipitation duration, three main patterns were revealed: the first is the summer pattern, which is similar to the second of the analysis for precipitation amount; the second is the winter pattern, with the spatial maximum located over the eastern mainland and western Crete; finally, the third one is the autumn pattern, with the maximum in northwestern Greece. During the third 10 day period of October and the second 10 day period of February, precipitation seems to present singularities, possibly due to fluctuations in atmospheric circulation. The above intra-annual variations and spatial distribution patterns are connected to the seasonal variations of the depression trajectories, the atmospheric instability, the influence

  2. Applying the Ramer-Douglas-Peucker algorithm to compress and characterize time-series and spatial fields of precipitation

    NASA Astrophysics Data System (ADS)

    Ehret, Uwe; Neuper, Malte

    2014-05-01

    Well known in image processing and computer graphics, the Ramer-Douglas-Peucker(RDP) algorithm (Ramer, 1972; Douglas and Peucker, 1973) is a procedure to approximate a polygon (lines or areas) by a subset of its nodes. Typically it is used to represent a polygonal feature on a larger scale, e.g. when zooming out of an image. The algorithm is simple but effective: Starting from the simplest possible approximation of the original polygon (for a line it is the start and end point), the simplified polygon is built by successively adding always the node of the original polygon farthest from the simplified polygon. This is repeated until a chosen agreement between the original and the simplified polygon is reached. Compared to other smoothing and compression algorithms like moving-average filters or block aggregation, the RDP algorithm has the advantages that i) the simplified polygon is built from the original points, i.e. extreme values are preserved and ii) that the variability of the original polygon is preserved in a scale-independent manner, i.e. the simplified polygon is high-resolution where necessary and low-resolution where possible. Applying the RDP algorithm to time series of precipitation or 2d spatial fields of radar rainfall often reveals a large degree of compressibility while losing almost no information. In general, this is the case for any auto-correlated polygon such as discharge time series etc. While the RDP algorithm is thus interesting as a very efficient tool for compression, it can also be used to characterize time series or spatial fields with respect to their temporal or spatial structure by relating, over successive steps of simplification, the compression achieved and information lost. We will present and discuss the characteristics of the RDP-based compression and characterization at various examples, both observed (rainfall and discharge time series, 2-d radar rainfall fields) and artificial (random noise fields, random fields with known

  3. Seasonal and Spatial Variation in Carbon and Nitrogen Isotope Values of Aquatic Macrophytes within the Indian River Lagoon, FL, USA

    NASA Astrophysics Data System (ADS)

    Clementz, M.; Tuross, N.

    2006-12-01

    The Indian River Lagoon (IRL) is a biologically diverse estuary located at the boundary between sub-tropical and warm-temperate marine waters on Florida`s Atlantic coast. Increased residential, agricultural and commercial development along the IRL has drastically changed the nutrient load of freshwater sources emptying into the lagoon, which has in turn impacted the local ecosystem. The degree of development is heterogeneously distributed along the length of the IRL, creating distinct zones of high and low nutrient loading. We examined the effect of these spatially distinct changes in nutrient content on the IRL ecosystem by collecting specimens of seagrass and marine algae from several sites spanning a north-south transect within the IRL and analyzing the carbon (δ13C) and nitrogen (δ15N) isotope composition of these marine macrophytes. Aquatic plant tissue stable isotope values are strongly influenced by the stable isotope composition of the dissolved inorganic carbon (DIC) and nitrogen (DIN) pools, which in turn show distinct differences between anthropogenic and natural sources. Thus, the δ13C and δ15N values of marine macrophytes can aid in monitoring the human impact on environmental quality by serving as proxies for the relative contribution and influence of anthropogenic, terrestrial and marine nutrients within the IRL. Large spatial and seasonal differences in stable isotope values were detected among both plant types. A north-south gradient in carbon and nitrogen isotope values was found in the IRL with δ13C values lowest and δ15N values highest towards the northern end of the lagoon. Comparison of this gradient with water quality data collected by the IRL monitoring program suggests that these isotope values are strongly correlated with salinity. To the north of the IRL, freshwater influx from natural rivers and man-made canals lower salinity levels and introduce large amounts of DIC and DIN from anthropogenic sources. In contrast, the southern

  4. A fully automated meltwater monitoring and collection system for spatially distributed isotope analysis in snowmelt-dominated catchments

    NASA Astrophysics Data System (ADS)

    Rücker, Andrea; Boss, Stefan; Von Freyberg, Jana; Zappa, Massimiliano; Kirchner, James

    2016-04-01

    In many mountainous catchments the seasonal snowpack stores a significant volume of water, which is released as streamflow during the melting period. The predicted change in future climate will bring new challenges in water resource management in snow-dominated headwater catchments and their receiving lowlands. To improve predictions of hydrologic extreme events, particularly summer droughts, it is important characterize the relationship between winter snowpack and summer (low) flows in such areas (e.g., Godsey et al., 2014). In this context, stable water isotopes (18O, 2H) are a powerful tool for fingerprinting the sources of streamflow and tracing water flow pathways. For this reason, we have established an isotope sampling network in the Alptal catchment (46.4 km2) in Central-Switzerland as part of the SREP-Drought project (Snow Resources and the Early Prediction of hydrological DROUGHT in mountainous streams). Samples of precipitation (daily), snow cores (weekly) and runoff (daily) are analyzed for their isotopic signature in a regular cycle. Precipitation is also sampled along a horizontal transect at the valley bottom, and along an elevational transect. Additionally, the analysis of snow meltwater is of importance. As the sample collection of snow meltwater in mountainous terrain is often impractical, we have developed a fully automatic snow lysimeter system, which measures meltwater volume and collects samples for isotope analysis at daily intervals. The system consists of three lysimeters built from Decagon-ECRN-100 High Resolution Rain Gauges as standard component that allows monitoring of meltwater flow. Each lysimeter leads the meltwater into a 10-liter container that is automatically sampled and then emptied daily. These water samples are replaced regularly and analyzed afterwards on their isotopic composition in the lab. Snow melt events as well as system status can be monitored in real time. In our presentation we describe the automatic snow lysimeter

  5. Regime shifts in the Arctic North Atlantic during the Neoglacial revealed by seabirds and precipitation isotopes on Bjørnøya, Svalbard

    NASA Astrophysics Data System (ADS)

    D'Andrea, William J.; Hormes, Anne; Bakke, Jostein; Nicolaisen, Line

    2016-04-01

    The northeastern North Atlantic Ocean, and the Norwegian and Greenland Seas are subject to large hydrographic changes. These variations can influence oceanic heat transport to the Arctic, meridional overturning circulation, and atmospheric circulation patterns and thereby impact global climate patterns. Marine records suggest that numerous large-scale changes in the hydrography of the northern North Atlantic took place during the middle to late Holocene. We report a record of nitrogen and hydrogen isotope measurements from a lake sediment core from Bjørnøya, Svalbard (74.38°N, 19.02°E) that documents major regime shifts in the climate of the northern North Atlantic during the past 6,000 years. Bjørnøya is the nesting ground for one of the largest seabird populations in the North Atlantic. As top predators in the marine ecosystem, seabirds (and their guano) are enriched in 15N; during spring and summer months they deliver isotopically enriched nitrogen to nesting areas. We developed a record of seabird population changes on Bjørnøya based on the nitrogen isotope composition of sediments in a core collected from lake Ellasjøen. The record reveals multiple multicentennial scale changes in δ15N values (varying between ~8-12‰) that track past changes in the size of seabird populations. From the same sediment core, we also developed a record of δD of precipitation, using δD values of sedimentary n-alkanes. Past intervals with the largest inferred bird populations correspond with the most enriched δD of precipitation, which we interpret to represent a more Atlantic climate. Periods with reduced seabird populations correspond with intervals with more negative δD of precipitation and representing a more Arctic climate. Together, the nitrogen and hydrogen isotope records signify regime shifts in the oceanography, marine ecosystem, and atmospheric circulation of the northern North Atlantic that are related to variations in the strength of the subpolar gyre.

  6. Increased Precipitation over the Yucatan Peninsula Inferred from the Spatial and Temporal Distribution of Late Holocene Foram Assemblages

    NASA Astrophysics Data System (ADS)

    Rachmallu, M.; Broach, K.; Paytan, A.; Street, J. H.

    2014-12-01

    As global climate warms, IPCC predictions suggest dry and seasonally dry regions will become dryer, increasing stress on water resources by growing urban populations (e.g. Southern California; Yucatan, Mexico). This study aims to reconstruct paleohydrologic trends during the late Holocene using foraminifera assemblages in Yucatan, Mexico to determine drought susceptibility in a region affected by migration of the Intertropical Convergence Zone (ITCZ). The ITCZ affects precipitation over the Yucatan Peninsula, potentially decreasing groundwater infiltration and thus reducing discharge in submarine springs at the peninsula margins. The field site Celestun Lagoon near Merida, Yucatan, Mexico, is dominated by spring and groundwater inputs at the northern terminus and opens to the Gulf of Mexico at the southern end resulting in a strong salinity gradient dependent on freshwater influx. We analyzed the foram assemblage in the top 6 cm of a set of 7 cores collected along a lagoonal transect (from the mouth to the head) and plotted the relative abundances of Ammonia beccarii, Elphidium sp., Quinqueloculina sp., and the ostracod Hemicyprideis cf. nichuptensis against site location. A. beccarii abundance increases from 40% near the head to 70% near the middle of the lagoon before dropping to <10% toward the saline lagoon mouth (high abundance in brackish salinity). Quinqueloculina sp. increases from 0% at the upper lagoon to nearly 40% near the mouth showing an opposite trend along the same transect. Elphidium sp. showed no clear trend (abundance range 10-28% throughout), and lowest H. nichuptensis abundance occurred at the middle of the lagoon (10%) increasing to the north and south (up to 60%). The inversely correlated spatial distribution between A. beccarii and Quinqueloculina sp. occurs vertically in an upper lagoon long core from 125-96 cm below sediment-water interface (14C age dates 3968-2820 ka), implying a decreasing salinity over ~1000 yrs and increased

  7. Spatial geochemical and isotopic characteristics associated with groundwater flow in the North China Plain

    NASA Astrophysics Data System (ADS)

    Chen, Jianyao; Tang, Changyuan; Sakura, Yasuo; Kondoh, Akihiko; Yu, Jingjie; Shimada, Jun; Tanaka, Tadashi

    2004-11-01

    The North China Plain (NCP) is an important agricultural area in China and has a high population density. Serious water shortages have occurred in this region over the last 20 years. Water transfer from the Yangtze River (the east route) was initiated in the year 2002 to provide water for the major cities of the NCP. This study was carried out before the implementation of the water transfer project, focusing on the spatial integration of the groundwater flow system and geochemical characteristics, which are mainly controlled by tectonics, geomorphology, and lithology. The field survey and the geochemical analyses of the groundwater samples indicated that the groundwater in the NCP has a two-layer structure, with a boundary at a depth of about 100-150 m. The two layers differ in pH, concentrations of SiO2 and major ions, and isotopes (18O, deuterium and tritium (T)). Chemical components in the upper layer showed a wider range and higher variability than those in the lower layer, indicating the impact of human activity. The flow direction of the groundwater in the upper layer was examined in detail in two profiles, showing that the upper layer flows east towards the Cangzhou-Daming fault, while the groundwater in the lower layer flows northeast towards Tianjin. Three hydrogeological zones are identified: recharge (Zone I), intermediate (Zone II), and discharge (Zone III). The recharge zone was found to be low in chloride (Cl-) but high in T. The discharge zone was found to be high in Cl- and low in T. This may be due to the difference in groundwater age. The discharge zone was subdivided into two sub-zones, Zone III1 and Zone III2, by considering the effects of human activities. Zone III2 was strongly affected by water diversions from the Yellow River. As groundwater flows from the recharge zone to the intermediate and discharge zones, chemical patterns evolve in the order: Ca-HCO3 > Mg-HCO3 > Na-Cl + SO4.

  8. Spatially resolved analysis of plutonium isotopic signatures in environmental particle samples by laser ablation-MC-ICP-MS.

    PubMed

    Konegger-Kappel, Stefanie; Prohaska, Thomas

    2016-01-01

    Laser ablation-multi-collector-inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) was optimized and investigated with respect to its performance for determining spatially resolved Pu isotopic signatures within radioactive fuel particle clusters. Fuel particles had been emitted from the Chernobyl nuclear power plant (ChNPP) where the 1986 accident occurred and were deposited in the surrounding soil, where weathering processes caused their transformation into radioactive clusters, so-called micro-samples. The size of the investigated micro-samples, which showed surface alpha activities below 40 mBq, ranged from about 200 to 1000 μm. Direct single static point ablations allowed to identify variations of Pu isotopic signatures not only between distinct fuel particle clusters but also within individual clusters. The resolution was limited to 100 to 120 μm as a result of the applied laser ablation spot sizes and the resolving power of the nuclear track radiography methodology that was applied for particle pre-selection. The determined (242)Pu/(239)Pu and (240)Pu/(239)Pu isotope ratios showed a variation from low to high Pu isotope ratios, ranging from 0.007(2) to 0.047(8) for (242)Pu/(239)Pu and from 0.183(13) to 0.577(40) for (240)Pu/(239)Pu. In contrast to other studies, the applied methodology allowed for the first time to display the Pu isotopic distribution in the Chernobyl fallout, which reflects the differences in the spent fuel composition over the reactor core. The measured Pu isotopic signatures are in good agreement with the expected Pu isotopic composition distribution that is typical for a RBMK-1000 reactor, indicating that the analyzed samples are originating from the ill-fated Chernobyl reactor. The average Pu isotope ratios [(240)Pu/(239)Pu = 0.388(86), (242)Pu/(239)Pu = 0.028(11)] that were calculated from all investigated samples (n = 48) correspond well to previously published results of Pu analyses in contaminated samples from

  9. Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought

    NASA Astrophysics Data System (ADS)

    Pervez, M. S.; Henebry, G. M.

    2014-02-01

    We evaluated the spatial and temporal responses of precipitation in the basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean (IO) dipole modes using observed precipitation records at 43 stations across the Ganges and Brahmaputra basins from 1982 to 2010. Daily observed precipitation records were extracted from Global Surface Summary of the Day dataset and spatial and monthly anomalies were computed. The anomalies were averaged for the years influenced by climate modes combinations. Occurrences of El Niño alone significantly reduced (60% and 88% of baseline in the Ganges and Brahmaputra basins, respectively) precipitation during the monsoon months in the northwestern and central Ganges basin and across the Brahmaputra basin. In contrast, co-occurrence of La Niña and a positive IO dipole mode significantly enhanced (135% and 160% of baseline, respectively) precipitation across both basins. During the co-occurrence of neutral phases in both climate modes (occurring 13 out of 28 yr), precipitation remained below average to average in the agriculturally extensive areas of Haryana, Uttar Pradesh, Bihar, eastern Nepal, and the Rajshahi district in Bangladesh in the Ganges basin and northern Bangladesh, Meghalaya, Assam, and Arunachal Pradesh in the Brahmaputra basin. This pattern implies that a regular water deficit is likely in these areas with implications for the agriculture sector due to its reliance on consistent rainfall for successful production. Major flooding and drought occurred as a consequence of the interactive effects of the ENSO and IO dipole modes, with the sole exception of extreme precipitation and flooding during El Niño events. This observational analysis will facilitate well informed decision making in minimizing natural hazard risks and climate impacts on agriculture, and supports development of strategies ensuring optimized use of water resources in best management practice under changing climate.

  10. Diffusive fractionation of BTEX and chlorinated ethenes in aqueous solution: quantification of spatial isotope gradients.

    PubMed

    Jin, Biao; Rolle, Massimo; Li, Ting; Haderlein, Stefan B

    2014-06-01

    Laboratory experiments were performed to investigate and quantify the extent of diffusive isotope fractionation of organic contaminants in aqueous solution. We selected petroleum hydrocarbons (toluene and ethylbenzene, in 1:2 mixtures of labeled (perdeuterated) and nonlabeled isotopologues) and chlorinated solvents (trichloroethene, TCE, and cis-dichloroethene, cis-DCE, at their natural isotopic abundance) as model compounds. The experimental approach using gel diffusion tubes allowed us to resolve concentration and isotopic gradients induced by isotopologue-specific diffusion and to determine aqueous diffusion coefficients in agreement with the values calculated using published empirical correlations. The experimental results were quantitatively evaluated with numerical simulations to determine the aqueous diffusion coefficients, D, and the exponent of the inverse power-law relation between D and the molecular mass of the isotopologues. The results show remarkable diffusive isotope fractionation for all the investigated organic compounds; however, the extent of fractionation was found to be smaller for the chlorinated ethenes and remarkably deviating from an inverse square root relationship between the isotopologues diffusion coefficients and their molecular mass. The outcomes of this study are relevant for the interpretation of isotopic signatures of organic contaminants in environmental systems and for the quantitative application of compound specific isotope analysis (CSIA) that needs to take into account the fractionation effects of both physical and transformation processes. PMID:24811111

  11. Rapid, quantitative analysis of americium, curium and plutonium isotopes in Hanford samples using extraction chromatography and precipitation plating

    SciTech Connect

    Kaye, J.H.; Strebin, R.S.; Orr, R.D.

    1994-04-01

    Recently developed methods for the rapid, quantitative analysis of americium (Am), curium (Cm), and plutonium (Pu) isotopes in Hanford soil, sludge, and waste-tank samples are described. After dissolution, dilutions are made as necessary based on alpha-energy analysis of a small aliquot of the original solution. isotopic tracers are then added and Am-Cm and Pu are separated by extraction chromatography, coprecipitated with neodymium fluoride, and counted. Examples of alpha spectra are given, and results obtained for Hanford sludge samples are presented.

  12. Precipitation rates and atmospheric heat transport during the Cenomanian greenhouse warming in North America: Estimates from a stable isotope mass-balance model

    USGS Publications Warehouse

    Ufnar, David F.; Ludvigson, Greg A.; Gonzalez, L.; Grocke, D.R.

    2008-01-01

    Stable isotope mass-balance modeling results of meteoric ??18O values from the Cenomanian Stage of the Cretaceous Western Interior Basin (KWIB) suggest that precipitation and evaporation fluxes were greater than that of the present and significantly different from simulations of Albian KWIB paleohydrology. Sphaerosiderite meteoric ??18O values have been compiled from the Lower Tuscaloosa Formation of southwestern Mississippi (25??N paleolatitude), The Dakota Formation Rose Creek Pit, Fairbury Nebraska (35??N) and the Dunvegan Formation of eastern British Columbia (55??N paleolatitude). These paleosol siderite ??18O values define a paleolatitudinal gradient ranging from - 4.2??? VPDB at 25??N to - 12.5??? VPDB at 55??N. This trend is significantly steeper and more depleted than a modern theoretical siderite gradient (25??N: - 1.7???; 65??N: - 5.6??? VPDB ), and a Holocene meteoric calcite trend (27??N: - 3.6???; 67??N: - 7.4??? VPDB). The Cenomanian gradient is also comparatively steeper than the Albian trend determined for the KWIB in the mid- to high latitudes. The steep latitudinal trend in meteoric ??18O values may be the result of increased precipitation and evaporation fluxes (amount effects) under a more vigorous greenhouse-world hydrologic cycle. A stable-isotope mass-balance model has been used to generate estimates of precipitation and evaporation fluxes and precipitation rates. Estimates of Cenomanian precipitation rates based upon the mass-balance modeling of the KWIB range from 1400??mm/yr at 25??N paleolatitude to 3600??mm/yr at 45??N paleolatitude. The precipitation-evaporation (P-E) flux values were used to delineate zones of moisture surplus and moisture deficit. Comparisons between Cenomanian P-E and modern theoretical siderite, and Holocene calcite latitudinal trends shows an amplification of low-latitude moisture deficits between 5-25??N paleolatitude and moisture surpluses between 40-60??N paleolatitude. The low-latitude moisture deficits

  13. Non-parametric inferences on climate change of high-resolution spatial patterns of precipitation extremes in Iberia

    NASA Astrophysics Data System (ADS)

    Melo-Gonçalves, Paulo; Rocha, Alfredo; Pinto, Joaquim; Santos, João; Corte-Real, João

    2013-04-01

    Precipitation daily-total data, obtained a multi-model ensemble of Regional Climate Model (RCM) simulations provided by the EU FP6 Integrated Project ENSEMBLES, is analysed at a horizontal spatial resolution of 25 km in the Iberian Peninsula (IP). ENSEMBLES' RCMs were driven by boundary conditions imposed by General Circulation Models (GCMs) that ran under historic conditions from 1961 to 2000, and under the SRES A1B scenario from 2001 to 2100. Annual and seasonal indices of precipitation extremes, proposed by the CCI/CLIVAR/JCOMM Expert Team on Climate Change Detection and Indices (ETCCDI), were derived from the daily precipitation ensemble. The ensemble of ETCCDI indices is subjected to climate detection methods in order to identify Iberian regions projected to experience higher climate change. Non-parametric climate change detection methods are applied to each member of the ETCCDI multi-model ensemble (ETCCDI-MME) and to and to its median (ETCCDI-MMEM). The resulting statistics are used to infer climate change projections and associated uncertainties. Climate change projections are evaluated from the statistics obtained from the ETCCDI-MMEM, while the uncertainties of those projections are evaluated by a rank-based measure of the spread of these statistics across the ETCCDI-MME. All methods consist of an estimator whose realization, or estimate, is tested by a non-parametric hypothesis test: (i) Theil-Sen linear trend, from 1961 to 2100, tested by the Mann-Kendall test; (ii) differences between the climatologies, estimated by the time median, of a near-future (2021-2050) and a distant-future (2071-2100) climates from the climatology of a recent-past reference climate (1961-1990), tested by the Mann-Whiteney test; and (iii) difference between the Probability Distributions of the near and distant climates from that of the reference climate, tested by the Kolmogorov-Smirnov test. IP regions with statistically significant, at 0.05 level, projected climate change

  14. Spatial Distribution of Lead Isotope Ratios and Inorganic Element Concentrations in Epiphytic Lichens from the Athabasca Oil Sands Region

    NASA Astrophysics Data System (ADS)

    Graney, J. R.; Landis, M. S.; Puckett, K.; Edgerton, E.; Krupa, S.; Percy, K.

    2013-12-01

    Coupled studies of inorganic element concentrations and lead (Pb) isotope ratios have been conducted on Hypogymnia physodes samples collected in the Athabasca Oil Sands Region (AOSR) in Alberta, Canada in 2002, 2008, and 2011. To investigate the spatial extent of air emissions, the lichens were collected from sites as far as 160 km from the mining and processing operations. 30 milligram sub-samples of the lichens were microwave digested, and the extracts were analyzed using DRC-ICPMS to determine elemental concentrations, and sector field ICPMS to measure Pb isotope ratios. Concentrations of elements in the lichens were found to reflect proximity to mining and oil processing sites as well as topography, ecosystem differences, and the metabolic biogeochemistry of the lichens. An exponential decrease in concentration of metals associated with fugitive dust (aluminum and others) versus distance from the mining sites, suggests elevated coarse particle emissions associated with mining operations. Near source concentrations of metals with an oil signature (vanadium and others) are less enhanced and more homogeneous than the metals in the fugitive dust, reflecting emission and deposition of smaller diameter particles at greater distances from oil processing sources. The mining and oil processing signatures are superimposed over elemental concentrations that reflect the nutrient needs of the lichens. These findings are being confirmed through ongoing studies using dichot samplers to collect coarse and fine particulate aerosol samples. The lichen samples collected beyond 50 km from the mining and processing sites cluster into a Pb isotope grouping with a 207Pb / 206Pb ratio of 0.8650 and a 208Pb / 206Pb ratio near 2.095. This grouping likely reflects the regional background Pb isotope ratio signature. 207Pb / 206Pb and 208Pb / 206Pb ratios decrease as one nears the mining and processing operations. This indicates that other Pb source(s), (e.g. Pb in the bitumen from the oil

  15. Food-web inferences of stable isotope spatial patterns in copepods and yellowfin tuna in the pelagic eastern Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Olson, Robert J.; Popp, Brian N.; Graham, Brittany S.; López-Ibarra, Gladis A.; Galván-Magaña, Felipe; Lennert-Cody, Cleridy E.; Bocanegra-Castillo, Noemi; Wallsgrove, Natalie J.; Gier, Elizabeth; Alatorre-Ramírez, Vanessa; Ballance, Lisa T.; Fry, Brian

    2010-07-01

    Evaluating the impacts of climate and fishing on oceanic ecosystems requires an improved understanding of the trophodynamics of pelagic food webs. Our approach was to examine broad-scale spatial relationships among the stable N isotope values of copepods and yellowfin tuna ( Thunnus albacares), and to quantify yellowfin tuna trophic status in the food web based on stable-isotope and stomach-contents analyses. Using a generalized additive model fitted to abundance-weighted-average δ 15N values of several omnivorous copepod species, we examined isotopic spatial relationships among yellowfin tuna and copepods. We found a broad-scale, uniform gradient in δ 15N values of copepods increasing from south to north in a region encompassing the eastern Pacific warm pool and parts of several current systems. Over the same region, a similar trend was observed for the δ 15N values in the white muscle of yellowfin tuna caught by the purse-seine fishery, implying limited movement behavior. Assuming the omnivorous copepods represent a proxy for the δ 15N values at the base of the food web, the isotopic difference between these two taxa, “ ΔYFT-COP,” was interpreted as a trophic-position offset. Yellowfin tuna trophic-position estimates based on their bulk δ 15N values were not significantly different than independent estimates based on stomach contents, but are sensitive to errors in the trophic enrichment factor and the trophic position of copepods. An apparent inshore-offshore, east to west gradient in yellowfin tuna trophic position was corroborated using compound-specific isotope analysis of amino acids conducted on a subset of samples. The gradient was not explained by the distribution of yellowfin tuna of different sizes, by seasonal variability at the base of the food web, or by known ambit distances (i.e. movements). Yellowfin tuna stomach contents did not show a regular inshore-offshore gradient in trophic position during 2003-2005, but the trophic

  16. A spatially explicit multi-isotope approach to map influence regions of plant-plant interactions after exotic plant invasion

    NASA Astrophysics Data System (ADS)

    Hellmann, Christine; Oldeland, Jens; Werner, Christiane

    2015-04-01

    Exotic plant invasions impose profound alterations to native ecosystems, including changes of water, carbon and nutrient cycles. However, explicitly quantifying these impacts remains a challenge. Stable isotopes, by providing natural tracers of biogeochemical processes, can help to identify and measure such alterations in space and time. Recently, δ15N isoscapes, i.e. spatially continuous representations of isotopic values, derived from native plant foliage, enabled to accurately trace nitrogen introduced by the N2-fixing invasive Acacia longifolia into a native Portuguese dune system. It could be shown that the area of the system which was altered by the invasive species exceeded the area which was covered by the invader by far. But still, definition of clear regions of influence is to some extent ambiguous. Here, we present an approach using multiple isoscapes derived from measured foliar δ13C and δ15N values of a native, non-fixing species, Corema album. By clustering isotopic information, we obtained an objective classification of the study area. Properties and spatial position of clusters could be interpreted to distinguish areas that were or were not influenced by A. longifolia. Spatial clusters at locations where A. longifolia was present had δ15N values that were enriched, i.e. close to the atmospheric signal of 0 o compared to the depleted values of the uninvaded system (ca. -11 o). Furthermore, C. album individuals in these clusters were characterized by higher foliar N content and enriched δ13C. These results indicate that the N2-fixing A. longifolia added nitrogen to the system which originated from the atmosphere and was used by the native C. album, inducing functional changes, i.e. an increase in WUE. Additionally, clusters were identified that were presumably determined by inherent properties of the native system. Thus, combining isotope ecology with geostatistical methods is a promising approach for mapping regions of influence in multi-isotope

  17. Stable oxyten and carbon isotope study of recent sediments and cements, Lee Stocking island, Bahamas: Organic vs. inorganic precipitation

    SciTech Connect

    Falls, W.F.; Williams, D.F.; Kendall, C.G.St.C.; Dill, R.F. )

    1990-05-01

    Stable isotope analyses of modern carbonates from the tidal inlet along the north end of Lee Stocking Island indicate a strong correlation of both carbon and oxygen isotope values with grain size. Carbonate samples used in this study include the soft, recently formed outer surface of several large columnar stromatolites, bedded muds from within the tidal channel, and marine hardgrounds from the shallow shoals adjacent to the channel. All samples are predominantly aragonite and were divided into mud-, silt-, and sand-size particles and bleached of organics prior to isotopic analysis. The range in isotopic values for all carbonate samples is 3.3 to 4.6 {per thousand} for {delta}{sup 13}C and {minus}0.3 to {minus}1.4{per thousand} for {delta}{sup 18}O. The {delta}{sup 18}O and {delta}{sup 13}C values of the mud-size aragonite from all of these samples are depleted relative to the silt- and sand-size ooids and peloids and have isotope values lighter than 1.4{per thousand} for {delta}{sup 13}C and 0.8{per thousand} for {delta}{sup 18}O. The {delta}{sup 13}C values for green calcerous algae from the restricted platform behind Lee Stocking are similar to values for the stromatolite mud. {delta}{sup 13}C values for the hardground and channel-based muds are intermediate between the {delta}{sup 13}C values for the calcareous algae, and coarse-grained sediment. These data suggest that the green calcareous algae which fluorish in the restricted platform, are a significant source of aragonite mud in and around the channel but are not the only source.

  18. A 26-year Composite Stable Isotope Record of Precipitation, Humidity and El Niño in the Spines of Saguaro Cactus, Carnegiea gigantea.

    NASA Astrophysics Data System (ADS)

    English, N. B.; Dettman, D. L.; Williams, D. G.

    2008-12-01

    Seasonal cycles of rainfall and humidity are recorded by stable isotopes in the spines of columnar cactuses. Multi-decadal δ18O and δ13C records of spine series from five saguaro cactuses, dated using bomb radiocarbon and semi-annual variations in δ13C, demonstrate the reproducibility of a climate signal. For δ18O and δ13C, the expressed population signal between 1980 and 2006 is 0.68 and 0.66, respectively, but 0.76 and 0.59 between 1980 and 1997, suggesting that age/height related effects are present in isotopic spine series. Composite δ18O and δ13C records constructed from five spine series show significant relationships to external climate forcing. Once dating errors are corrected, mean annual spine δ18O is negatively correlated with total annual precipitation (TAP) from November through October (P < 0.001) and positively correlated with mean annual nighttime vapor pressure deficit (VPD) (P < 0.01). Year to year decreases (> 2‰) in the maximum annual spine δ18O are positively correlated with the Southern Oscillation Index (P < 0.01). We hypothesize these decreases are caused by El Niño enhanced winter rainfall. While less significant, minimum annual δ13C is negatively correlated with TAP (P < 0.05) and mean nighttime VPD (P < 0.05). These results bolster proposed mechanistic models of isotopic variation in the spines of columnar cactuses and demonstrate the use of isotopic spine series as climate proxies.

  19. Spatial and temporal variability of precipitation for selected regions of New York State and relationship to variability in sulfate deposition measurements

    SciTech Connect

    Pagnotti, V.; Rao, S.T.

    1986-04-01

    The preliminary results are presented of a study aimed at quantifying the variability in precipitation data and its role in the modeling of acidic deposition processes. The character of this variability for various regions of New York State is assessed over a 30-year period, with emphasis on the Adirondack region. Spatial and temporal means as well as coefficients of variation are presented. Of the five regions where precipitation data are investigated, the Adirondacks have the greatest overall variability, around 23 percent, while Long Island has the least, about 17 percent. A proportionality factor, based on the coefficient of variation, is suggested to account for the precipitation variability in achieving targeted wet deposition threshold values.

  20. Spatial patterns and temporal trends in mercury concentrations, precipitation depths, and mercury wet deposition in the North American Great Lakes region, 2002-2008

    USGS Publications Warehouse

    Risch, Martin R.; Gay, David A.; Fowler, Kathleen K.; Keeler, Gerard J.; Backus, Sean M.; Blanchard, Pierrette; Barres, James A.; Dvonch, J. Timothy

    2012-01-01

    Annual and weekly mercury (Hg) concentrations, precipitation depths, and Hg wet deposition in the Great Lakes region were analyzed by using data from 5 monitoring networks in the USA and Canada for a 2002-2008 study period. High-resolution maps of calculated annual data, 7-year mean data, and net interannual change for the study period were prepared to assess spatial patterns. Areas with 7-year mean annual Hg concentrations higher than the 12 ng per liter water-quality criterion were mapped in 4 states. Temporal trends in measured weekly data were determined statistically. Monitoring sites with significant 7-year trends in weekly Hg wet deposition were spatially separated and were not sites with trends in weekly Hg concentration. During 2002-2008, Hg wet deposition was found to be unchanged in the Great Lakes region and its subregions. Any small decreases in Hg concentration apparently were offset by increases in precipitation.

  1. Spatial and seasonal responses of precipitation in the Ganges and Brahmaputra river basins to ENSO and Indian Ocean dipole modes: implications for flooding and drought

    USGS Publications Warehouse

    Pervez, Md Shahriar; Henebry, Geoffry M.

    2015-01-01

    We evaluated the spatial and seasonal responses of precipitation in the Ganges and Brahmaputra basins as modulated by the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) modes using Global