辽宁省干旱大尺度环流及2020年夏旱成因分析

Large Scale Circulations of Drought in Liaoning Province and the Causes of Summer Drought in 2020

摘要: 2020年夏季(2020年6月1日至8月10日)，辽宁省降水量为163.1毫米，较常年同期偏少48.7%，出现干旱灾害。本文基于辽宁省61个国家级气象观测站逐日降水量数据和美国国家环境预测中心/美国国家大气研究中心(NCEP/NCAR)再分析数据，分析了2020年辽宁省夏季降水实况，研究了历史降水异常年份的大尺度环流特征，并从大气环流异常的角度分析了造成该年夏季干旱的原因。结果表明：夏季干旱年辽宁上空200 hPa西风急流偏强，副热带高压位置偏东偏南，辽宁地区低层为偏北气流控制，动力和水汽条件差，这种高低层环流配置易导致辽宁地区降水偏少。2020年夏季环流与历史干旱年典型环流一致，辽宁省受高压脊控制，西太平洋副热带高压偏强且脊线位置偏南，偏南水汽条件差，同时，初夏影响辽宁省的东北冷涡不活跃，且位置异常偏北，以上大气环流异常是造成2020年夏季辽宁省干旱灾害的主要原因。

Abstract: The summer drought disaster has a significant impact on crop growth. In the summer of 2020 (June 1 to August 10, 2020), the precipitation in Liaoning Province was 163.1 millimeters, which was 48.7% lower than the same period in normal years, resulting in drought disasters. Based on the daily precipitation data of 61 meteorological observation stations in Liaoning Province and the reanalysis data of NCEP/NCAR atmospheric circulation, the characteristics of summer precipitation is analyzed, the large-scale circulation characteristics of historical abnormal precipitation years is studied, then, the cause of summer drought in Liaoning in 2020 is explained. The results show that, in the drought years, the 200 hPa westerly jet over Liaoning is relatively strong, and the subtropical high pressure is located to the east and south. Meanwhile, Liaoning is controlled by low-level northward winds, so the power and water vapor conditions are poor. This high-low level circulation configuration can lead to less precipitation in Liaoning region. The summer circulation of 2020 is consistent with the typical circulation of historical drought years. In summer 2020, Liaoning Province is controlled by a high-pressure ridge, and the subtropical high pressure in the western Pacific is stronger and the ridge line is located southward, resulting in poor water vapor conditions towards the south. In early summer, the northeast cold vortex affecting Liaoning Province is inactive and abnormally located northward. The above atmospheric circulation anomalies were the main cause of drought disasters in Liaoning Province in the summer of 2020.