采用1961—2010年全国753站逐日降水资料,给出了我国秋季连阴雨的定义,分析我国秋季连阴雨和不同级别(5~7 d、8~10 d和11 d及以上)秋季连阴雨的气候特征;将我国秋季连阴雨划分为华北、西南、江淮和华南地区4区,并分析华北地区秋季连阴雨期间和不同级别秋季连阴雨期间的大气环流特征。结果表明:1)我国秋季连阴雨及不同级别秋季连阴雨50 a累计频次在长江中上游地区较大,黄河以北地区较小;随着连阴雨级别的增加,连阴雨频次大值区由东南地区移向西南地区;频次标准差与频次的分布特征类似。2)华北地区连阴雨及不同级别连阴雨期间,巴尔喀什湖与贝加尔湖间的阻塞高压增强,850 h Pa上增强的偏北和偏南气流交汇于华北地区,500 h Pa上东亚大槽槽后偏北气流引导北方冷空气南下,副热带高压西侧偏南气流引导南方暖空气北上,冷、暖空气在华北地区交汇,易形成连阴雨天气。
Continuous autumn rain is long in duration, meaning it can easily cause crop mold and other adverse effects relating to daily life and industrial and agricultural production.In order to mitigate such losses caused by continuous autumn rain, it is important to study in depth the climate characteristics of continuous autumn rain and its causes.The present study does this based on the daily rainfall and sunshine data of 753 meteorological stations in China in autumn (September--November) from 1961 to 2010, along with NCEP/NCAR reanalysis data for the period 1948-2010.After defining continuous autumn rain in China,its climate characteristics for different levels (5-7 d,8-10 d, and 11 d and above) are analyzed.Based on a general survey of regions where continuous autumn rain was found to happen often during 1961--2010 ,China is divided into four regions of continuous autumn rain; namely, North China, Southwest China, the Changjiang--Huaihe basin, and South China, where representative stations are Xingtai ( Hebei Province), Wufeng ( Hubei Province), Gushi ( Henan Province) and Yongan (Fujian Province ) , respectively. The circulation characteristics of continuous autumn rain and continuous autumn rain of different levels in North China are also analyzed.The results show that: (1) The accumulated frequency of continuous autumn rain and continuous autumn rain of different levels mainly concentrates in the mid-upper reaches of the Yangtze River during 1961-2010, and is very small in the areas north to the Yellow River.With an increase in the level of rain,the high-frequency areas move from southeast to southwest.The frequency standard deviation is similar to the frequency of continuous autumn rain and continuous autumn rain of different levels. (2) During the continuous autumn rain and continuous autumn rain of different levels in North China, in the 500 hPa geopotential height field,the northern cold air is guided to the south by northerly flow after the East Asian trough, and southern