5—8月东北冷涡降水过程统计特征及其降水特征对比研究

Statistical and Comparative Study on Precipitation Characteristics in NECV for May to August

作者：

崔景琳成都信息工程大学大气科学学院；沈阳市气象局成都 610225；110168
白爱娟成都信息工程大学大气科学学院成都 610225

中文摘要：

定义了东北冷涡降水过程，利用NCEP提供的FNL再分析资料和地面降水观测资料，识别了2010—2014年5—8月的40次冷涡降水过程，对这些过程的统计分析结果表明：东北地区5—8月约有1/4的天数受冷涡降水影响。其中，5月冷涡降水过程天数最多，但移速快、降水弱；7月次之，移速慢、降水强；6和8月冷涡降水过程相对较少，降水强度适中。40例冷涡降水过程中有20例为暴雨型冷涡，其余为非暴雨型；暴雨型冷涡在7月最多，非暴雨型冷涡5月最多。为探究冷涡强降水的形成条件，选择了2010年7月25日的冷涡暴雨和2013年5月28日的冷涡小雨过程，在二者的冷涡强度和环流形势相似的前提下，对比分析了两次过程中降水的形成机制。分析发现：两次过程降水初期的水汽条件相似。暴雨型冷涡大尺度背景下的上升条件更佳。暴雨型冷涡南部持续的垂直风切变，形成了持续的上升运动和强水汽辐合，是造成暴雨的原因；而非暴雨型冷涡过于强盛的偏北气流破坏了冷涡北部的水汽辐合中心，过程中仅产生弱降水。冷涡垂直方向上的温压结构和风场结构并不对称，冷涡降水中心位于南北气流交汇的一侧。

中文关键词：

东北冷涡，统计特征，强降水形成条件，对比分析

KeyWords：

NECV, statistical characteristics, formation conditions of rainstorm, comparative analysis

Abstract：

The northeast cold vortex (NECV) precipitation process is defined in this paper. Based on surface observational precipitation data and the FNL reanalysis data provided by NCEP, the NECV precipitation processes are identified for May to August in 2010－2014.Fourty cases of the identified NECV precipitation processes were analyzed, and two of them were compared for researching the characteristics of NECV precipitation. The results of statistical analysis are following: about 1/4 of days were controlled by NECV in China for May to August. In May, it is found that on the most number of NECV days, the NECV velocities were relatively fast while the precipitation were the smallest. It is noticed that the less NECV day, the slower NECV movement, while the heavier precipitation in July comparing to that in May. July is the month occurred the most rainstorms. The number of NECV precipitation processes was similarly relative less in June and August, yet the precipitation intensities were moderate in June and August. There are 20 rainstorm and 20 non-rainstorm processes. The rainstorm process on July 25, 2010 and the non-rainstorm process on May 28, 2013 were selected to compare and study the forming conditions of the cold vortex heavy precipitation. Under the premise of similarity of cold vortex intensity and circulation, the formation mechanism of precipitation in the two processes was compared and analyzed. The results show that the water vapor conditions are similar at the beginning in the two processes. The ascending condition of rainstorm type cold vortex is better at large scale background than that at small scales. The continuous vertical wind shear in the southern part of the NECV may form a continuous ascending motion and strong convergence of water vapor, which is the cause of the rainstorm, in the southern part of NECV. The strong northerly flow destroyed the convergence center in the NCEV with only weak precipitation. The vertical temperature and pressure structure and wind field structure in the NECV were not symmetrical. The cold vortex precipitation center was located in the confluence side of north-ward and south-ward airflow.