基于湿润指数的1960—2011年中国西南地区地表干湿变化特征

Characteristics of Southwestern China Dry-wet Condition Based on Wetness Index in 1960-2011

基于西南地区108个气象站点1960—2011年逐日气温、降水、风速、日照时数和相对湿度数据,应用Penman-Monteith模型计算出潜在蒸散量以及地表湿润指数,并结合气候倾向率、ArcGIS反距离加权插值、滑动t检验、Morlet小波周期分析等方法,分析了研究区地表干湿状况时空变化特征及空间差异。结果表明:近52 a来,西南地区湿润指数在波动中呈降低趋势,其变化倾向率为-0.005/10 a,趋于干旱,其中变湿增幅以1990年代最大,距平值为0.106,变干增幅却以21世纪最显著,为-0.052,特别是在2002年以后,湿润指数大幅下降,最低值出现在2009年,为1.41;年湿润指数存在明显的空间差异,表现为:自东南向西北、自南向北递减,川西高原和云贵高原西部为低值中心,高值中心在四川盆地西部;变干地区多于变湿地区,且各年代变干幅度大于变湿幅度。突变和Morlet小波功率谱分析表明,西南地区地表干湿状况在1990、2003年发生突变,且存在10.638 a的周期。

Based on the daily data from108 meteorological stations in Southwest China during1960 to 2011, as well as use of the monthly potential evapotranspiration and monthly precipitation data, the surface humidity index was calculated. The temporal and spatial variation characteristics of surface humidity index were analysized by using the methods of Inverse Distance Weighted interpolation in ArcGIS 9.3, moving t-test technique, climate tendency rate and Morlet wavelet. The results show that: in recent 52 years, the surface humidity index in Southwest China is decreasing in fluctuation and the decreasing rate is- 0.005/10 a, which showed the slightly trend to drought. The 1990s have the greatest increase in change to wet and the anomaly value is 0.106. The 21st century witnesses the most significant increase in desiccation and the anomaly value is-0.052. Especially after 2002, surface humidity index drops significantly,the minimum value appears in 2009 and the anomaly value is 1.41. Annual humidity index exists obvious differences in space. The surface humidity index not only decreases from southeast to northwest, but also from south to north. Western Sichuan Plateau and the Yunnan-Guizhou Plateau are the low center value while the high value center is in the western Sichuan Basin.The area turning to be dry is larger than to be wet in the study area, correspondingly, the process of turning to be dry is more obvious than that of wet. Abrupt change analysis and Morlet wavelet power spectrum analysis indicated that surface dry and wet conditions in Southwest China have abrupt change events in 1990 and 2003 with a period 10.638 years.