一次寒潮降温过程的等熵位涡和热力学分析

通过等熵位涡和热力学能量方程的各项诊断对2018年1月上旬我国东部一次寒潮天气过程进行分析，重点给出垂直运动在寒潮降温中的作用。结果表明：此次寒潮天气过程主要受蒙古国南部的横槽转竖影响，巴尔喀什湖东部和西伯利亚地区及其北部为引起这次寒潮的主要冷空气源地。欧亚大陆北部和极区对流层高层和平流层低层的高位涡强冷空气沿着等熵面向南向下平流，引导强冷空气侵袭我国东部。等熵位涡大值区的东侧对应上升运动区，有利于降水的产生。寒潮期间风场平流引起的850 hPa强降温区主要位于东南沿海地区，降温幅度最高可达6×10^-4 K·s^-1，而东北地区在整个寒潮期间冷平流强度较弱，最大降温幅度仅约为1×10^-4 K·s^-1。通过计算东南沿海和东北地区区域平均风场平流和垂直运动引起850 hPa温度变化，得出寒潮期间两地的温度总降幅约为1×10^-4 K·s^-1。东南沿海地区的寒潮主要由风场的冷平流引起，而东北地区则是由冷平流和垂直上升运动的共同作用引起。垂直方向上，东北地区冷空气能影响的高度要远高于东南沿海地区。

Isentropic vortex and thermodynamic analysis of a cold wave cooling process

A weather process of cold wave in eastern China in early January 2018 was analyzed, focusing on the role of vertical motion in cold wave cooling through the diagnosis of isentropic vortex and thermodynamic energy equation. The results show that due to influence of the horizontal trough transforming into vertical trough in south of Mongolia, cold-air outbreaks in eastern China. The eastern part of Lake Balkhash and the Siberian region and its northern region are the main sources of cold air that causes this cold wave. Strong cold air associated with high vortex in upper troposphere and lower stratosphere in the northern and polar regions of Eurasia moves south and down along the isentropic direction, leading to strong cold air invading eastern China. The east side of the isentropic vortex large value area corresponds to the rising motion zone, which is conducive to the generation of precipitation. The strong cooling zone is mainly located in the southeast coastal area at 850 hPa by the advection of wind field, and the cooling rate is up to 6×10^-4 K·s^-1 during the cold wave. The cold advection intensity is weak in the northeastern region, and the maximum cooling rate is only about 1×10^-4 K·s^-1 during the whole cold wave. By calculating the average 850 hPa temperature change caused by the wind field advection and vertical motion in the southeastern coastal and northeastern regions, it is concluded that the total temperature cooling rate of both places is about 1×10^-4 K·s^-1. The cooling in the southeastern coastal areas is mainly caused by the cold advection of the wind field, while the northeastern region is caused by the combined of the cold advection and the vertical ascending motion. The cold air in northeastern region can be affected much higher than that in the southeast coastal area in the vertical direction.