西南地区春季及其各月降水的气候特征分析

利用1951～2017年我国西南地区26个台站的降水观测资料，本文研究了该地区春季及其各月降水的基本气候特征。结果表明:5月是春季我国西南地区降水最多的月份，其占春季总降水的55.3%，此外，5月降水年际变化强度最大；西南地区春季及其各月降水均具有显著的年代际变化特征，5月降水在春季降水的年代际变化特征中占据主导地位；在年代际突变特征方面，西南地区春季降水存在显著的年代际突变特征，其在1970年代后期发生了减少突变，而在1990年代中后期发生了增加突变；在变化趋势方面，春季西南区域平均降水的变化趋势不明显，但从空间上看，西南地区东部表现出显著增多的趋势，而西部则表现出显著减少的趋势；在周期方面，西南地区春季及其4～5月降水均具有显著的年际和年代际变化周期，需要说明的是，3月降水没有明显的年代际变化周期，总体上看，5月降水在春季降水周期变化中占据主导地位。

Climatic Characteristics of Rainfall over Southwest China during Spring and Spring Months

Using observed rainfall data from 26 stations in Southwest China for the period 1951–2017, in this study, we investigated the climatic characteristics of rainfall over Southwest China during spring (March–April–May) and each spring month. The rainfall in May was found to account for 55.3% of the total spring rainfall over Southwest China and to have the most significant interannual variations of the spring months. The spring rainfall over Southwest China also shows clear interdecadal variations, which are dominated by the interdecadal variations of the May rainfall. Significant abrupt interdecadal changes (AIDCs) also occur in the spring rainfall, with increased AIDCs having occurred in the middle and the later 1990s after a period of decreased IDACs in the later 1970s. Although the time series of spring rainfall over Southwest China exhibits an insignificant linear trend, the eastern part of Southwest China shows a clear decreasing trend in terms of area, and the western part of Southwest China shows a significant increasing trend. Lastly, the spring rainfall over Southwest China shows significant interannual and interdecadal periodicities, which are also present in the April and May rainfalls. We note that no interdecadal periodicity is evident for March rainfall. In general, the interannual and interdecadal periodicities of spring rainfall are dominated by the variations of May rainfall.