Convective Hydration of the Upper Troposphere and Lower Stratosphere
Convective Hydration of the Upper Troposphere and Lower Stratosphere
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对流层上层和平流层下层的对流水合作用
DOI：
10.1029/2018jd028286
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
A. Dessler
中科院分区：
文献类型：
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作者：
M. Schoeberl;E. Jensen;L. Pfister;R. Ueyama;M. Avery;A. Dessler
我们使用前向域填充轨迹模型来探索热带对流对平流层水蒸气 (H2O) 和热带对流层顶层云分数 (TTLCF) 的影响。我们的模型结果与 2008/2009 年冬季 TTLCF 进行了比较，该 TTLCF 源自具有正交偏振的云气溶胶激光雷达以及微波临边探测器的低平流层 H2O 观测结果。对流通过驱动空气达到冰饱和相对湿度来改变原位水蒸气。如果空气是欠饱和的，那么对流会通过冰的蒸发使空气水合，但如果空气是过饱和的，那么对流冰晶就会生长并沉淀，使空气脱水。平均而言，对流层上层存在大量的水合和脱水对流事件，但水合事件多于脱水事件。在此分析期间，明确增加对流会使全球平流层水蒸气增加不到 2%。热带对流层顶温度是平流层水汽的主要控制因素，除非对流延伸到对流层顶之上，否则它几乎没有直接影响。不到 1% 的模型地块在分析的冷点对流层顶上方遇到对流。另一方面，对流对 TTLCF 有很大影响。当包含对流时，TTLCF 模型会加倍，考虑到热带对流频率和对流高度可能会发生变化，这种敏感性对未来气候相关的变化具有影响。
We use our forward domain filling trajectory model to explore the impact of tropical convection on stratospheric water vapor (H2O) and tropical tropopause layer cloud fraction (TTLCF). Our model results are compared to winter 2008/2009 TTLCF derived from Cloud‐Aerosol Lidar with Orthogonal Polarization and lower stratospheric H2O observations from the Microwave Limb Sounder. Convection alters the in situ water vapor by driving the air toward ice saturation relative humidity. If the air is subsaturated, then convection hydrates the air through the evaporation of ice, but if the air is supersaturated, then convective ice crystals grow and precipitate, dehydrating the air. On average, there are a large number of both hydrating and dehydrating convective events in the upper troposphere, but hydrating events exceed dehydrating events. Explicitly adding convection produces a less than 2% increase in global stratospheric water vapor during the period analyzed here. Tropical tropopause temperature is the primary control of stratospheric water vapor, and unless convection extends above the tropopause, it has little direct impact. Less than 1% of the model parcels encounter convection above the analyzed cold‐point tropopause. Convection, on the other hand, has a large impact on TTLCF. The model TTLCF doubles when convection is included, and this sensitivity has implications for the future climate‐related changes, given that tropical convective frequency and convective altitudes may change.