2017年秋季河南罕见连阴雨天气特征及成因分析

2017年8月下旬至10月中旬河南发生了近14a来罕见秋季连阴雨过程。利用1961—2017年河南省地面气候整编资料和NCEP/NCAR再分析资料,采用相关分析法、T检验、小波分析及带通滤波等方法,对此次连阴雨过程的大气环流特点进行分析。结果表明:2017年秋季河南连阴雨期间,乌拉尔山高压脊、贝加尔湖低槽和西太平洋副热带高压较常年同期偏强且长时间维持;东欧和里海—巴尔喀什湖两个地区是此次连阴雨过程的上游关键区域,东欧地区大气环流具有准双周到30d的振荡周期,里海—巴尔喀什湖地区具有4—8d的振荡周期。东亚200hPa急流轴东西跨度和急流核的极大风速较常年同期偏大;急流区西南部的辐散区在河南上空有抽吸作用,有利于降水的发生;高空急流纬向风速有三次加强过程,与三次连阴雨过程相对应。在不同的连阴雨阶段水汽输送源地和输送通道不同,三个阶段的水汽来源分别为印度洋、中国南海和西太平洋。

Characteristics and causes of rare continuous rain weather event in He'nan province during autumn in 2017

An event of continuous rain weather occurred from late August to mid-October in 2017 in He'nan province;such weather occurred rarely in the past 14 years.The characteristics of atmospheric circulation during this event were analyzed based on meteorological data from 1961 to 2017 in He'nan province and the National Center for Environment Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data.Different analysis methods were used in this study,including the correlation analysis method,the T-test method,the wavelet analysis method,and the band-pass filter analysis method,etc.The results show that the Wular Ridge,the Bay Lake Trough,and the Western Pacific Subtropical High are abnormally strong and maintain for a long time during this event.Eastern Europe and Caspian-Bahu areas are the key upstream regions for the continuous rainy process.The atmospheric circulation in the Eastern Europe has an oscillation period from quasi two weeks to 30 days,while the oscillation period in the Caspian-Bahu is from 4 to 8 days.The east-west span of the 200-hPa jet axis and the maximum wind speed of the jet core are abnormally larger than that on average in the same period.The divergence zone in the southwestern part of the jet zone has the suction effect over He'nan province,which is conducive to the occurrence of precipitation.The zonal wind speeds of the upper jet enhance three times,corresponding to three continuous rainy processes.The water vapor transport sources and channels are different during different continuous rainy processes;water vapor in these three rainy processes originates from the Indian Ocean,the South China Sea,and the Western Pacific Ocean,respectively.