近50年三江源地表湿润指数变化特征及其影响因素

基于三江源区1959—2008年月平均气温、最高气温、最低气温、相对湿度、降水量、风速和日照百分率等气候要素资料,应用修订的Penman-Monteith（P-M）模型计算了最大潜在蒸散量和地表湿润指数,分析其空间分布、年际和年代际变化特征及其主要气象因子的影响。结果表明：1959—2008年间,研究区年降水量呈增加趋势,降水量变化曲线线性拟合倾向率为5.316~13.047 mm.（10a）-1,春夏季增幅较大;最大潜在蒸散量呈增加趋势,年最大潜在蒸散量变化曲线线性拟合倾向率在5.073~10.712 mm.（10a）-1,夏季增幅最大;地表湿润指数变化也呈增加趋势,年地表湿润指数变化曲线线性拟合倾向率0.011~0.026（10a）-1,冬季增幅最大,在15年周期附近,出现了3~5个干湿交替期,1984年之后为偏湿期,在中高频区,1998—2006年有偏干振荡;影响三江源区地表湿润指数的主要因子是降水量、相对湿度和平均最高气温。

Climatic change of terrestrial surface humid index and its impact factors over the source region of three rivers in recent 50 years

Based on climatic observational data of monthly average temperature,maximum temperature,minimum temperature,relative humidity,precipitation,wind speed and sunshine duration over the source region of three rivers in the year 1959—2008,the data of maximum potential evapotranspiration（ET0） and terrestrial surface humid index was computed by revised Penman-Monteith Model.The distribution,inter-annual change and the seasonal difference of ET0 and surface humid index were analyzed,and the climatic impact factors for the change trend of surface humid index were discussed.The main results were as follows： In 1959—2008,the annual precipitation in this region had an increased trend,the annual precipitation change curves’ linear fitting rate is 5.316-13.047 mm.（10a）-1,and the increasing rate mostly appeared bigger in spring and summer.The annual ET0 displayed an ascending trend as well,and the linear fitting rate of the annual ET0 change curves is 5.073-10.712 mm.（10a）-1,the biggest increasing rate appeared mostly in summer.The surface humid index displayed an ascending trend,with the linear fitting rate of its change curves being 0.011-0.026（10a）-1,the biggest increasing rate appeared mostly in winter.The climatic 3-5 periods of dry and wet alternation happened about every 15 a period of time and frequency,which was the light wet stages since 1984,while the light dry stages appeared at a higher frequency in 1998—2006.The main factors which could influence the surface humid index were the precipitation,the relative humidity and the average maximum temperature.