副热带东亚季风区一次穿透性对流过程影响下平流层成分变化的个例分析

穿透性对流是导致北半球夏季平流层低层南亚高压内水汽极值形成的重要机制之一，关于副热带东亚季风区穿透性对流是否对平流层低层水汽等物质分布存在影响目前尚不清楚。本文选取2016年的武汉暴雨事件，采用Cloudsat和Aura Microwave Limb Sounder（MLS）卫星数据，分析了东亚季风区的穿透性对流活动对上对流层/下平流层物质分布的影响。利用CloudSat卫星资料云分类产品和Aura MLS卫星数据联合分析武汉暴雨过程中捕捉到1次穿透性对流事件，该事件发生于2016年7月4日05时（协调世界时）的穿透性对流，中心位于海上梅雨带区域。分析表明，这次对流穿透事件对上对流层/下平流层物质分布有显著影响，穿透性对流活动影响到对流层顶以上的物质分布，具体表现是:首先，穿透性对流显著减少了局地对流层顶附近的臭氧含量，较之气候态对流层顶臭氧含量偏少32.53%；其次，穿透性对流能够增加局地对流层顶附近的水汽混合比含量，它通过更多的云冰粒子蒸发来增强局地平流层水汽含量，同时通过更强的垂直水汽输送来直接加湿平流层。此次穿透性对流事件对水汽变化影响较之对臭氧含量变化的影响更为显著，它使得对流层顶水汽混合比增加近乎一倍（98.15%）。因此，副热带东亚季风区的穿透性对流活动对于对流层向平流层的物质输送起着重要的作用。

Impacts of An Overshooting Deep Convection Process over Subtropical Asian Monsoon Region on the Variation of the Lower Stratospheric Atmospheric Composition

The rapid transport associated with overshooting deep convection is essential for the summertime water vapor maxima in the lower stratosphere over the Asian monsoon region. However, the impacts of overshooting deep convection over the subtropical Asian monsoon region on the distribution of the lower stratospheric atmospheric composition have not been fully addressed. In this study, the authors use CloudSat and Aura Microwave Limb Sounder satellite data to investigate the characteristics of overshooting deep convections in Wuhan rainstorm during 2016. The concentrations of water vapor (H₂O), ice water content (IWC), and ozone (O₃) in the upper troposphere/lower stratosphere during overshooting deep convections are analyzed. Overshooting deep convection case, which occurred at 0500 UTC on 4 July 2016, considerably reduced the ozone mixing ratio near the tropopause. Specifically, it led to a 32.53% decrease in the climatological mean ozone mixing ratio. The overshooting convection is also found to enhance the moisture content in the lower subtropical stratosphere, and this hydrating effect has two mechanisms: that induced by ice particle evaporation and that by the convective moisture flux itself. Overshooting convection results in a greater change in the moisture (about 98.15% increase of the climatology) than in the ozone. Our study results indicate that the local overshooting convections over the subtropical Asian monsoon region in boreal summer are important factors in the transport of water vapor from the troposphere into the low stratosphere.