Abstract:

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.

Key words: Southwest China, wet season, dry season, climatic characteristics