2013年7月2日东北强降水研究

Study on a Heavy Rainfall over Northeast China on 2 July 2013

为揭示2013年7月2日形成东北暴雨的降水原因,利用常规观测、加密站逐日降水资料以及NCEP/NCAR提供的FNL再分析资料等,使用天气动力学诊断方法,分析了影响2013年7月2日东北暴雨主要天气形势和影响系统。结果表明:对流层中高层稳定少变的"北低南高"形势是导致7.2东北暴雨的主要天气形势,"北低"就是从对流层中低层到对流层中高层都存在的深厚东北冷涡,此深厚的东北冷涡一方面使东北上空形成对流不稳定的大气层结结构;另一方面,使东北地区以南地区形成一个从地面延伸至对流层高层的高空锋区,伴随着高空锋区的存在,东北处于高空急流入口区的南侧,由于大气质量的调整,形成低空急流,高低空急流的耦合,使东北上空存在一支明显的次级环流,这可能是引起东北7.2日暴雨的主要动力强迫机制,暴雨主要发生在高空急流入口区右侧和低空急流出口处左前方的右侧;来自阿拉伯海和孟加拉湾、南海、西太平洋南部的偏南气流以及西风带偏西气流,为东北7.2暴雨提供了较好的水汽供应。四边水汽收支结果表明,西边界、南边界和东边界都是水汽输入边界,且南边界贡献最大,只有北边界是水汽输出边界,东北在水汽盈余的条件下,十分有利于7.2暴雨的产生。

Based on the data from the conventional meteorological observation,including the surface daily precipitation and the FNL reanalysis data provided by the NCEP / NCAR,using the weather diagnosis and analysis methods,the mainly synoptic situation and weather system affecting the heavy rainfall over Northeast China on 2 July 2013 are studied. The results are as follows： The main synoptic situation for heavy rainfall over Northeast China is the stable situation called＂Vortex in the north,high pressure in the south＂in the upper troposphere. ＂Vortex in the north＂indicates Northeast Cold Vortex exist from low troposphere to upper troposphere. On one hand,the Northeast Cold Vortex leads the Northeast China forming the atmospheric structure of convective instability; On the other hand,it also leads the south of Northeast China forming a upper frontal zone. Accompaning the existing of upper frontal zone,Northeast China is locating the south of the entrance to the upper jet. Due to the coupling of low-level jet and upper jet causing by adjustment of air mass,a obvious secondary circulation forms over Northeast China. Perhaps it is the mainly dynamic force mechanism generating the heavy rainfall over Northeast China on 2 July 2013. At the same time,the heavy rainfall is located both the right side of the entrance to the upper jet and the left side of the entrance to the low-level jet. Moisture from Arabian sea,the Bay of Bengal,the South China Sea and the south of western pacific by southerly airflow and westerlies by westerly airflow provid good condition for the heavy rainfall. The moisture budget result indicates the west,south and east sides are all positive moisture sides,especially for the south side which providing the most,and the north side is negative side. With positive moisture over Northeast China,it＇s in favour of the heavy rainfall over Northeast China on2 July.