1961—2014年我国西南地区干湿季变化特征

摘要

利用中国1961—2014年逐日降水观测等资料,分析了西南地区的干湿季变化特征.结果表明:西南地区东部和西北部最早进入湿季;干季由四川盆地、贵州南部开始.西南中东部以及南部等地的湿季长度较长,干季则与之相反.干湿季开始日期以及干湿季长度均具有明显的年代际变化特征,在1970年代中期到1980年代发生了气候突变,呈现湿季长度变短,干季变长的趋势.湿季降水呈现东南多、西北少的特征,并表现出中东部减少,西部增加的趋势;干季降水则表现为东多西少的特点,在东部呈增加,在四川等地呈减少趋势.进一步分析表明:湿季异常偏湿(干)年,开始日期易偏早(晚),结束易偏晚(早),长度偏长(短);干季开始异常偏早(晚)年,干季长度长(短),干季略偏湿(干);太平洋、印度洋海温异常影响东亚大气环流的异常是造成西南地区干湿季出现异常的主要原因.%By utilizing daily precipitation dataset from 1961 to 2014 in China, the characteristics of wet and dry seasons in Southwest China were analyzed. The results indicated that the wet season started from the eastern and northwestern part of this region, and the dry season started from the Sichuan Basin, southern Guizhou. The climatological wet season was longer in the mid-east and south of Southwest China, and vice versa the dry season. The onset date and length of wet and dry seasons exhibited abrupt shift in the mid-1970s to the 1980s, and it is very significant that the length of wet (dry) season became shorter (longer). There were large differences in the spatial and temporal features of the precipitation between the wet and dry season. There was more precipitation in southeastern part than in northwestern area in wet season, and the decreasing trend was observed in eastern part while increasing trend in the western part. For the dry season, there was more precipitation in the eastern Southwest China than in the western part, the precipitation in Chongqing and Guizhou showed an increasing trend, while a decreasing trend was found in Sichuan. In the anomalous wet (dry) years of wet season, the onset date was earlier (later), the end date tended to be later (earlier), the length of wet season was longer (shorter). In the anomalous earlier (later) onset years of dry season, the length of dry season was longer (shorter), and more (less) precipitation was observed in the season. The main reason of the abnormalities of wet and dry seasons in Southwest China was that the East Asia atmospheric circulation anomalies were influenced by the Pacific and Indian SST anomalies.