Modeling the isotopic composition of precipitation
Modeling the isotopic composition of precipitation
复制标题
模拟降水的同位素组成
DOI：
10.1029/93jd03518
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发表时间：
1994
影响因子：
--
通讯作者：
R. Arnold
中科院分区：
文献类型：
--
作者：
S. Gedzelman;R. Arnold
水的稳定同位素物理学被纳入二维运动学云微物理模型中。该模型是运行几个理想化的，经典的层状和对流风暴的情况下，和由此产生的同位素比的降水和水蒸气进行诊断和观测比较。对于层状雪，该模型产生低同位素比，迅速减少极地的暖锋。最低的同位素比发生在大气寒冷时，垂直速度在对流层高处达到最大值时。对于层状降雨，该模型产生更高的同位素比没有显着的向极梯度作为一个结果之间的同位素交换的雨水和周围的蒸汽。当融化水平接近地面时，雨水的同位素比值最低，同位素交换最小。对于空气质量雷暴，同位素比率在暖空气中均匀地高，无论云的高度如何，除非冰雹接近或到达地面。该模型还产生了显着的降雨量效应，其中同位素比值随降雨量的增加而减少，总量。当雨水来自再循环过程时，同位素比特别低，在再循环过程中，先前被雨水中的蒸汽填充的空气随后上升。在这种情况下，模型有时会产生同位素比，从周边到降水屏蔽的核心减少。有人建议，这种再循环过程是负责在一些飓风和有组织的雷暴中观察到非常低的同位素比。云微物理过程的主导作用有时可以从降水的同位素比值中推断出来。该模型产生的冰球同位素比接近雨的颗粒时，产生的均匀冻结的雨和接近雪的颗粒时，产生的部分融化的雪的再冻结。同位素值的气候学的主要特征相匹配的观测到的全球数据集和七年的风暴记录在莫洪克湖，纽约是通过运行模型的广泛的条件。这包括南极雪的氘过量（d福尔斯），当δD下降到−300‰以下时，它会显著增加，而在温暖干燥的地区，雨水中观察到的氘不足。
The physics of the stable isotopes of water is incorporated into a two-dimensional, kinematic, bulk cloud microphysical model. The model is run for several idealized, classical stratiform and convective storm situations, and the resulting isotope ratios of precipitation and water vapor are diagnosed and compared to observations. For stratiform snow, the model produces low isotope ratios that decrease rapidly poleward of the warm front. The lowest isotope ratios occur when the atmosphere is cold and when the vertical velocity attains its maximum value high in the troposphere. For stratiform rains, the model produces much higher isotope ratios without a significant poleward gradient as a result of isotope exchange between the falling rain and the surrounding vapor. Isotope ratios of rain are lowest when the melting level is near the ground and isotope exchange is minimized. For air mass thunderstorms, isotope ratios are uniformly high in warm air, no matter what the cloud height, unless hail approaches or reaches the ground. The model also produces a significant amount effect for rain, in which isotope ratios decrease with increasing rainfall, totals. Isotope ratios are particularly low when the rain derives from a recirculation process in which air previously charged by vapor from falling rain subsequently rises. Under such conditions, the model sometimes produces isotope ratios that decrease from the periphery to the core of the precipitation shield. It is suggested that this recirculation process is responsible for extraordinarily low isotope ratios observed in some hurricanes and organized thunderstorms. The dominant cloud microphysical processes can sometimes be inferred from isotope ratios of precipitation. The model produces ice pellets with isotope ratios close to those of rain when the pellets are produced by homogeneous freezing of rain and close to those of snow when the pellets are produced by refreezing of partially melted snow. A climatology of isotope values that matches the main features of the observed global data set and of a seven-year record of storms at Mohonk Lake, New York is generated by running the model for a wide range of conditions. This includes the deuterium excess (d ≡ δD - 8*δ18O) for Antarctic snows that increases markedly as δD falls below −300‰ and the deuterium deficit observed for rain in warm, dry regions.