东北冷涡引起的对流输送过程个例分析和数值模拟

Case analyses and numerical simulation of transport process caused by convection associated with northeast cold vortex

平流层-对流层物质交换是影响全球大气成分收支的重要过程.过去的研究认为大尺度的交换过程在平流层-对流层物质交换中最为重要,但是近些年的研究表明,中小尺度过程对平流层-对流层物质交换也有重要贡献.本文利用OMI和MLS数据、ERA-Interim再分析资料,结合中尺度WRF模式综合分析了东北地区发生在冷涡前部和冷涡后部的两次强对流天气过程.结果表明:发生在冷涡前部暖锋云系中的强对流持续时间长,对流垂直尺度小,下平流层静力稳定度高;发生在冷涡后部的孤立强对流持续时间短,水平尺度较小,且在对流层顶附近,静力稳定度小,对流可穿出热力学对流层顶.从示踪物分布情况来看,两次强对流都可将示踪物输送到对流层顶附近,但是冷涡前部对流可将示踪物从边界层输送到整个对流层,而孤立对流是把示踪物输送到对流层顶,而不与自由对流层空气发生混合.

The stratosphere-troposphere exchange is a key process due to its effect on the global budget of chemical composition.Previous studies have shown that large-scale process is the most important in the stratosphere-troposphere exchange,but recent studies have shown that meso-and micro-scale processes also have important contributions to the stratosphere-troposphere exchange.The satellite data from MLS(the Aura Microwave Limb Sounder)and OMI(the Ozone Monitoring Instrument)and the ERA-Interim(European centre for medium-range weather forecasts Re-Analysis Interim)reanalysis data,combined with the Weather Research and Forecasting(WRF)model are used to test two convection events occurred on the western and eastern side of the cold vortex over northeastern China.The results show that the convection among the mesoscale cloud systems occurred on the eastern side of the cold vortex,would have a long lifetime,a small vertical scale,with the high static stability in the lower stratosphere.In contrast,the isolated convection occurred on the western side of the cold vortex,would have a short lifetime,a small horizontal scale,with low static stability in the lower stratosphere and overshooting the lapse-rate tropopause.Simulations show that the mesoscale cloud systems can transport the boundary layer tracer to the tropopause layer with mixing between the whole troposphere.In contrast,the isolated convection can directly transport the boundary layer tracer to the tropopause without mixing between the free troposphere.