The location of Costa Rica on the Central American Isthmus creates unique microclimate systems that receive moisture inputs directly from the Caribbean Sea and the Pacific Ocean. In Costa Rica, stable isotope monitori...The location of Costa Rica on the Central American Isthmus creates unique microclimate systems that receive moisture inputs directly from the Caribbean Sea and the Pacific Ocean. In Costa Rica, stable isotope monitoring was conducted by the International Atomic Energy Agency and the World Meteorological Association as part of the worldwide effort entitled Global Network of Isotopes in Precipitation. Sampling campaigns were mainly comprised of monthly-integrated samples during intermittent years from 1990 to 2005. The main goal of this study was to determine spatial and temporal isotopic variations of meteoric waters in Costa Rica using historic records. Samples were grouped in four main regions: Nicoya Peninsula (d2H = 6.65d18O -0.13;r2 = 0.86);Pacific Coast (d2H = 7.60d18O + 7.95;r2 = 0.99);Caribbean Slope (d2H = 6.97d18O + 4.97;r2 = 0.97);and Central Valley (d2H = 7.94d18O + 10.38;r2 = 0.98). The water meteoric line for Costa Rica can be defined as d2H = 7.61d18O + 7.40 (r2 = 0.98). The regression of precipitation amount and annual arithmetic means yields a slope of ﹣1.6‰ d18O per 100 mm of rain (r2 = 0.57) which corresponds with a temperature effect of ﹣0.37‰ d18O/°C. A strong correlation (r2 = 0.77) of ﹣2.0‰ d18O per km of elevation was found. Samples within the Nicoya Peninsula and Caribbean lowlands appear to be dominated by evaporation enrichment as shown in d-excess interpolation, especially during the dry months, likely resulting from small precipitation amounts. In the inter-mountainous region of the Central Valley and Pacific slope, complex moisture recycling processes may dominate isotopic variations. Generally, isotopic values tend to be more depleted as the rainy season progresses over the year. Air parcel back trajectories indicate that enriched isotopic compositions both in Turrialba and Monteverde are related to central Caribbean parental moisture and low rainfall intensities. Depleted events appear to be related to high rainfall amounts despite the parental origin of the moisture.展开更多
In this paper, we examine the performance of four isotope incorporated GCMs, i.e., ECHAM4 （Univer- sity of Hamburg）, HadCM3 （Hadley Centre）, GISS E （Goddard Institute of Space Sciences）, and MUGCM （Melbourne Un...In this paper, we examine the performance of four isotope incorporated GCMs, i.e., ECHAM4 （Univer- sity of Hamburg）, HadCM3 （Hadley Centre）, GISS E （Goddard Institute of Space Sciences）, and MUGCM （Melbourne University）, by comparing the model results with GNIP （Global Network of Isotopes in Precip- itation） observations. The spatial distributions of mean annual δD and mean annual deuterium excess d in precipitation, and the relationship between δ18O and δD in precipitation, are compared between GCMs and GNIP data over East Asia. Overall, the four GCMs reproduce major characteristics of δD in precipitation as observed by GNIP. Among the four models, the results of ECHAM4 and GISS E are more consistent with GNIP observed precipitation δD distribution. The simulated d distributions are less consistent with the GNIP results. This may indicate that kinetic fractionation processes are not appropriately represented in the isotopic schemes of GCMs. The GCM modeled MWL （meteoric water line） slopes are close to the GNIP derived MWL, but the simulated MWL intercepts are significantly overestimated. This supports that the four isotope incorporated GCMs may not represent the kinetic fractionation processes well. In term of LMWLs （local meteoric water lines）, the simulated LMWL slopes are similar to those from GNIP observa- tions, but slightly overestimated for most locations. Overall, ECHAM4 has better capability in simulating MWL and LMWLs, followed by GISS E. Some isotopic functions （especially those related to kinetic frac- tionation） and their parameterizations in GCMs may have caused the discrepancy between the simulated and GNIP observed results. Future work is recommended to improve isotopic function parameterization on the basis of the high-resolution isotope observations.展开更多
利用引入水稳定同位素循环的ECHAM4、GISS E、HadCM3、MUGCM以及iAWBM的模拟数据，分析了全球降水中稳定同位素效应的空间分布特征，对不同模式的模拟结果之间以及模拟结果与GNIP（Global Network of Isotopes in Precipitation）的实...利用引入水稳定同位素循环的ECHAM4、GISS E、HadCM3、MUGCM以及iAWBM的模拟数据，分析了全球降水中稳定同位素效应的空间分布特征，对不同模式的模拟结果之间以及模拟结果与GNIP（Global Network of Isotopes in Precipitation）的实际监测结果之间进行了比较，旨在对稳定同位素大气环流模式的模拟有效性进行评价，改善对水循环中水稳定同位素效应的理解和认识。结果显示，5个模式均很好地再现了全球降水中平均δ18O和平均δ18O季节差的空间分布特征，降水中稳定同位素的温度效应、降水量效应的分布特点以及全球大气水线GMWL（Global Meteoric Water Line）均被很好地模拟出。比较而言，ECHAM4模拟的降水中的平均δ18O以及δ18O平均季节差的空间分布与GNIP的实际分布最接近，拟合水平也最高；ECHAM4、GISS E、MUGCM和iAWBM再现全球温度效应空间分布的能力较强，拟合水平大致相当；由iAWBM模拟的降水量效应空间分布与实际分布之间的相关性最强，5个模式模拟的与实测的δ18O/P相关系数符号相同的站点数大致位于同一水平；GISS E和iAWBM模拟的全球大气水线与实测的GMWL最接近。展开更多
文摘The location of Costa Rica on the Central American Isthmus creates unique microclimate systems that receive moisture inputs directly from the Caribbean Sea and the Pacific Ocean. In Costa Rica, stable isotope monitoring was conducted by the International Atomic Energy Agency and the World Meteorological Association as part of the worldwide effort entitled Global Network of Isotopes in Precipitation. Sampling campaigns were mainly comprised of monthly-integrated samples during intermittent years from 1990 to 2005. The main goal of this study was to determine spatial and temporal isotopic variations of meteoric waters in Costa Rica using historic records. Samples were grouped in four main regions: Nicoya Peninsula (d2H = 6.65d18O -0.13;r2 = 0.86);Pacific Coast (d2H = 7.60d18O + 7.95;r2 = 0.99);Caribbean Slope (d2H = 6.97d18O + 4.97;r2 = 0.97);and Central Valley (d2H = 7.94d18O + 10.38;r2 = 0.98). The water meteoric line for Costa Rica can be defined as d2H = 7.61d18O + 7.40 (r2 = 0.98). The regression of precipitation amount and annual arithmetic means yields a slope of ﹣1.6‰ d18O per 100 mm of rain (r2 = 0.57) which corresponds with a temperature effect of ﹣0.37‰ d18O/°C. A strong correlation (r2 = 0.77) of ﹣2.0‰ d18O per km of elevation was found. Samples within the Nicoya Peninsula and Caribbean lowlands appear to be dominated by evaporation enrichment as shown in d-excess interpolation, especially during the dry months, likely resulting from small precipitation amounts. In the inter-mountainous region of the Central Valley and Pacific slope, complex moisture recycling processes may dominate isotopic variations. Generally, isotopic values tend to be more depleted as the rainy season progresses over the year. Air parcel back trajectories indicate that enriched isotopic compositions both in Turrialba and Monteverde are related to central Caribbean parental moisture and low rainfall intensities. Depleted events appear to be related to high rainfall amounts despite the parental origin of the moisture.
基金Supported by the National Natural Science Foundation of China(40871094 and 41171035)Construct Program of the Key Discipline in Hunan Province(2011001)+2 种基金Open Fund of Key Laboratory of Tibetan Environment Changes and Land Surface Processes of the Chinese Academy of Sciences(2011004)Special Research Fund for the Doctoral Program of Higher Education(20094306110006)Scientific Research Fund of Hunan Provincial Education Department(09A056)
文摘In this paper, we examine the performance of four isotope incorporated GCMs, i.e., ECHAM4 （Univer- sity of Hamburg）, HadCM3 （Hadley Centre）, GISS E （Goddard Institute of Space Sciences）, and MUGCM （Melbourne University）, by comparing the model results with GNIP （Global Network of Isotopes in Precip- itation） observations. The spatial distributions of mean annual δD and mean annual deuterium excess d in precipitation, and the relationship between δ18O and δD in precipitation, are compared between GCMs and GNIP data over East Asia. Overall, the four GCMs reproduce major characteristics of δD in precipitation as observed by GNIP. Among the four models, the results of ECHAM4 and GISS E are more consistent with GNIP observed precipitation δD distribution. The simulated d distributions are less consistent with the GNIP results. This may indicate that kinetic fractionation processes are not appropriately represented in the isotopic schemes of GCMs. The GCM modeled MWL （meteoric water line） slopes are close to the GNIP derived MWL, but the simulated MWL intercepts are significantly overestimated. This supports that the four isotope incorporated GCMs may not represent the kinetic fractionation processes well. In term of LMWLs （local meteoric water lines）, the simulated LMWL slopes are similar to those from GNIP observa- tions, but slightly overestimated for most locations. Overall, ECHAM4 has better capability in simulating MWL and LMWLs, followed by GISS E. Some isotopic functions （especially those related to kinetic frac- tionation） and their parameterizations in GCMs may have caused the discrepancy between the simulated and GNIP observed results. Future work is recommended to improve isotopic function parameterization on the basis of the high-resolution isotope observations.
文摘利用引入水稳定同位素循环的ECHAM4、GISS E、HadCM3、MUGCM以及iAWBM的模拟数据，分析了全球降水中稳定同位素效应的空间分布特征，对不同模式的模拟结果之间以及模拟结果与GNIP（Global Network of Isotopes in Precipitation）的实际监测结果之间进行了比较，旨在对稳定同位素大气环流模式的模拟有效性进行评价，改善对水循环中水稳定同位素效应的理解和认识。结果显示，5个模式均很好地再现了全球降水中平均δ18O和平均δ18O季节差的空间分布特征，降水中稳定同位素的温度效应、降水量效应的分布特点以及全球大气水线GMWL（Global Meteoric Water Line）均被很好地模拟出。比较而言，ECHAM4模拟的降水中的平均δ18O以及δ18O平均季节差的空间分布与GNIP的实际分布最接近，拟合水平也最高；ECHAM4、GISS E、MUGCM和iAWBM再现全球温度效应空间分布的能力较强，拟合水平大致相当；由iAWBM模拟的降水量效应空间分布与实际分布之间的相关性最强，5个模式模拟的与实测的δ18O/P相关系数符号相同的站点数大致位于同一水平；GISS E和iAWBM模拟的全球大气水线与实测的GMWL最接近。
