2020年江淮地区夏季持续性强降水过程分析

Analysis of Persistent Heavy Rainfall Process in Jianghuai Region in 2020 Summer

2020年夏季,中国江淮流域发生持续性强降水,为研究持续性强降水的发生机理,采用美国国家环境预报中心(NCEP/NCAR)提供的逐日再分析资料以及1981-2010年平均的逐日再分析资料,对这次江淮强降水的降水过程和环流形势进行分析。结果表明:(1)本次持续性降水可以分为三个阶段。第一阶段6月18-24日,雨带分布上呈现带状,表现为无降水中心或多降水中心的特征,最大累计降水量为268 mm,位于安徽六安;第二阶段6月26-30日,雨带呈现分散的两条带状分布,最大累计降水量为220.7 mm,位于浙江衢州;第三阶段7月2-8日,雨带呈现纺锤形,最大累积降水量达到了606.8 mm,降水强度强于前两阶段,位于安徽六安。(2)冷空气来自东北路径。第一阶段江淮地区上空被暖气团控制不受冷空气影响,第二阶段和第三阶段冷空气均来自东西伯利亚低槽,且第三阶段冷空气更强。(3)南亚高压的强度上,三个阶段分别为强弱强,与西南水汽输送强度相对应。西太副高在第一阶段强度较弱,范围较大;在第二阶段强度较强,范围较小;第三阶段副高强度和范围都较大。南海的水汽输送强弱主要受副高强度控制。因此,受南亚高压和副高影响的不同,三个阶段来自孟加拉湾的西南水汽输送为强、弱、强;来自南海的水汽输送为弱、强、强,第三阶段水汽最为充沛。(4)第一阶段,日本南部低空急流较弱、存在索马里低空急流,高空急流在东北亚有中断;第二阶段,日本南部低空急流较强、无索马里急流,高空急流连续;第三阶段,日本南部低空急流较强、索马里急流较强,高空急流连续且在东北亚下凹。各阶段高低空急流配置与水汽和冷空气的输送情况相一致,对此次持续性强降水的发生发展起到推动作用。

In the summer of 2020,persistent heavy rainfall occurred in the Yangtze Huaihe River Basin in China.In order to study the mechanism of the persistent heavy rainfall,the daily reanalysis data and average daily reanalysis data from 1981 to 2010 provided by the National Environmental Prediction Center(NCEP/NCAR) were used to analyze the precipitation process and circulation situation of the heavy rainfall in the Yangtze Huaihe River Basin.The results show:(1) the persistent rainfall can be divided into three stages:The first stage is from June 18 to June 24,the distribution of rain belt is zonal,and it is characterized by no precipitation center or multi precipitation center.And the maximum accumulated precipitation is 268 mm,which occurred in Liuan,Anhui Province.The second stage is from June 26 to June30,the rain belt is distributed in two belts,and the maximum accumulated precipitation is 220.7 mm,which occurred in Quzhou,Zhejiang Province.The third stage is from July 2 to July 8,rain belt is spindle shaped,the maximum accumulated precipitation is 606.8 mm,and which is larger than the first and second stages.The maximum precipitation area is occurred in Liuan,Anhui Province.(2)The cold air come from the Northeast path.In the first stage,the upper part of Jianghuai area is controlled by warm air mass,and is not affected by cold air;The cold air in the second and third stages come from the East Siberian trough,and the cold air in the third stage was stronger than that in the first two stages.(3) In terms of the intensity of the South Asia high,the three stages are strong,weak and strong.It corresponds to the southwest water vapor transport intensity.In the first stage,the intensity of the West Pacific subtropical high is weak and the range is large;in the second stage,the intensity is strong and the range is small;in the third stage,the intensity and range of the Western Pacific subtropical high are large.The Western Pacific subtropical high,in the first stage,which is weak in intensity and large in scope;in the second stage,which is strong in intensity and small in scope;in the third stage,the intensity and range of the Western Pacific subtropical high are large.The water vapor transport in the South China Sea is mainly controlled by the Western Pacific subtropical high.Therefore,the influence of South Asia high and the Western Pacific subtropical high is different.In terms of the southwest water vapor transport from the Bay of Bengal,the three stages are strong,weak and strong.In terms of the southwest water vapor transport from the South China Sea,the three stages are weak,strong and strong.In the third stage,the water vapor condition is better than the first two stages.(4) In the first stage,the low-level jet in southern Japan is weak.Low-level jet found in Somalia and the Upper jet is interrupted in Northeast Asia.In the second stage,the low-level jet in southern Japan is strong,low-level jet was not found in Somalia,and the Upper jet is continuous.In the third stage,the low-level jet in southern Japan is strong,and the Somali jet is strong,and the Upper jet is continuous and concave in Northeast Asia.In each stage,the configuration of high and low level flow is consistent with the transportation of water vapor and cold air,which promotes the occurrence and development of the persistent heavy rainfall.