Abstract:

Based on the daily precipitation at 53 stations in Liaoning Province, monthly circulation indexes from National Climate Centre of China and daily reanalysis data from NCEP/NCAR, the large-scale circulation characteristics of anomalous less rainfall in Liaoning Province in midsummer of 2014 were analyzed. The results show that the rainfall  in midsummer of 2014 was seriously less than the climatology mean in Liaoning Province, the precipitation anomaly in most days (87.1%) was negative, and the precipitation in most parts was 50% less than the normal, which was the most serious less rainfall event in the same period in the historically. The configuration of large-scale circulation in upper and lower levels wasn’t extremely beneficial to rainfall in Liaoning Province in midsummer of 2014. Liaoning Province was located in the north of the upper-level jet stream axis, which wasn’t conducive to the development of upward movement. The location of the west Pacific subtropical high and East Asian subtropical frontal zone were to the  west and the south compared with the normal, which caused the lack of warm and wet airflow transportation, so cold and warm air didn’t meet in Liaoning Province. The location of lower level jet stream was more eastward and southward than the normal, the westerly airflow controlled Liaoning Province, where warm and wet airflow transportation and convergence as well as ascending motion lacked. Abnormal sinking motion provided direct driving power for the serious less rainfall in Liaoning Province in midsummer of 2014. The lower level divergence and upper level convergence resulted in the abnormal sinking movement over Liaoning region. Meanwhile, there were two symmetrical abnormal circulations in the north and south sides of Liaoning respectively, which strengthened the sinking movement over Liaoning.

Key words: midsummer of 2014, anomalous less rainfall, large-scale circulation

摘要：

利用辽宁省53个站点逐日降水量、国家气候中心逐月环流指数和NCEP/NCAR逐日再分析资料，分析了2014年盛夏辽宁地区异常少雨的大尺度环流特征。结果表明：2014年盛夏，辽宁全省降水量严重偏少，大部地区偏少5成，为历史同期最严重少雨事件。高低空大尺度环流的异常配置是导致2014年盛夏辽宁降水严重偏少的环流成因，辽宁地区位于高空急流轴以北，不利于上升运动的发展；西太平洋副热带高压和东亚副热带锋区位置较常年偏西偏南，辽宁地区缺少暖湿气流输送及冷暖空气交绥；低空急流位置偏东偏南，辽宁地区主要受偏西气流控制，缺少偏南暖湿水汽输送及辐合上升运动。异常下沉运动是导致2014年盛夏辽宁地区降水严重偏少的直接动力，辽宁南北两侧存在两个对称的异常环流圈，异常下沉运动在辽宁地区叠加，使得下沉运动异常加强。

关键词: 2014年盛夏, 异常少雨, 大尺度环流