利用1961—2011 年中国西南5 省市113 个气象站的观测资料，基于Penman-Monteith 蒸散模型计算了各个站点逐月潜在蒸散和干湿指数，研究了近50 a 来西南地区气候干湿状况的时空变化特征。结果表明：西南地区气候整体较为湿润，但存在较大的区域差异，呈“东湿西干”的空间分布特征。近50 a 来西南区域的气候有“暖干化”的变化趋势，这种趋势在进入21 世纪以后有进一步加剧的迹象。西南地区干湿季特征鲜明，夏季最为湿润，冬季最干燥。近50 a 来，西南地区的气候干湿状况有两次显著的转变过程，第一次时间点在1992 年前后，此时气候开始湿润化，进入相对湿润期；另一次在2002 年前后，变化趋势由湿润化转为干旱化，进入相对干旱期。降水量是西南地区气候干湿状况的决定因素，日照时数与相对湿度等气象要素对干湿状况也产生较大影响。
Using the monthly measurements during 1961 to 2011 of 113 meteorological stations in Southwest China, the potential evapotranspiration and aridity index were calculated with the Penman-Monteith model and then the characteristics of spatial-temporal change of surface dry and wet conditions in Southwest China in recent 50 years are discussed. The results show that the dry and wet conditions in Southwest China are spatially uneven with a characteristic named "humid east and arid west" while they are moist as a whole. The climate dry and wet conditions tend to be hotter and drier in this area in recent 50 years and are growing more serious in the last 12 years. The climate dry and wet condition of summer is the moistest in four seasons while it is the driest in winter. There are two time points where the climate dry and wet conditions changed abruptly in Southwest China in the past 50 years. One is around 1992 when it tends to be moist and the other is around 2002 when it becomes dryer instead of moister. Precipitation plays a dominant role in the climate dry and wet conditions of Southwest China region meanwhile the factors such as sunshine duration and relative humidity also have a significant impact on them.
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