Observation and modeling of stable water isotopes as diagnostics of rainfall dynamics over southeastern Australia
Observation and modeling of stable water isotopes as diagnostics of rainfall dynamics over southeastern Australia
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DOI：
10.1029/2009jd012132
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发表时间：
2009-12
影响因子：
--
通讯作者：
V. Barras;I. Simmonds
中科院分区：
文献类型：
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作者：
V. Barras;I. Simmonds
[1]采用统一的观测和模拟方法，对澳大利亚东南部三种典型的降水环流类型进行了研究。从墨尔本大学同位素网收集了(1)混合锋面、(2)对流和(3)层状降水事件的18O和2H比值的高分辨率变化的观测数据。由于受降雨强度局部变化和大范围降水影响，降水的同位素含量在高频和低频上都有所不同。在事件时间尺度上，氢过量与降雨量的关系较弱，但在对流降水条件下，与降雨量的关系较强。作为对观测的补充，国家大气研究社区大气模式的一个版本运行着一个同位素水文学计划，通过再分析轻推来模拟混合锋面和层状事件。模拟结果很好地反映了~(18)O和过量氢的蒸气分布的演化。混合锋面的轨迹显示了水汽廓线的结构，揭示了来自不同源区的气团的汇聚。该模式对降水中过量的氚的描述不够准确，这表明在大气环流模式中对后凝结过程的参数化可能存在缺陷。通过以这种方式结合观测和建模，提供了事件的结构和历史的详细信息，这是仅通过对降水进行采样所不能获得的。
[1] A unified approach of observation and modeling was applied to the investigation of three circulation types that typically bring rain to southeastern Australia. Observations from the Melbourne University Network of Isotopes in Precipitation of high-resolution variations in the ratios of 18O and 2H were collected for (1) mixed frontal, (2) convective, and (3) stratiform precipitation events. Isotopic content of precipitation varied over both high and low frequencies because of influences from local variations in rain intensity and rainout by large-scale precipitation. Deuterium excess showed a weak relationship with rainfall amount on intraevent time scales but was stronger under convective rainfall conditions. As a supplement to the observations, a version of the National Center for Atmospheric Research Community Atmosphere Model running an isotope hydrology scheme simulated the mixed frontal and stratiform events by nudging with reanalyses. The simulations represented well the evolution of vapor profiles of 18O and deuterium excess. Trajectories for the mixed frontal case illustrated the structure of the vapor profiles, revealing a convergence of air masses from different source regions. Deuterium excess in precipitation was represented less accurately by the model, indicating a possible shortcoming in the parameterization of postcondensation processes in the general circulation model. By combining observations and modeling in this way, detail of the structure and history of the events was provided that would be unavailable from the sampling of precipitation alone.