中国西北干旱、半干旱区春季地气温差的年代际变化特征及其对华北夏季降水年代际变化的影响

Characteristics of Interdecadal Variability of the Difference Between Surface Temperature and Surface Air Temperature in Spring in Arid and Semi-Arid Region of Northwest China and Its Impact on Summer Precipitation in North China

利用我国1951-2000年夏季降水观测资料分析了我国夏季降水的年代际变化特征，表明了我国夏季降水在1976年前后发生了一次明显的气候跃变，在1976年之后华北地区和黄河流域夏季降水明显减少，出现了严重持续干旱，而西北地区从20世纪70年代后期开始，降水增多，且西北地区降水振荡位相要超前于华北地区降水振荡位相5～8年。并且，本文从1960-2000年我国西北干旱、半干旱区的地温、气温观测资料分析了我国西北干旱、半干旱地区的地气温差（Ts—Ta）的变化特征，其结果表明了在20世纪70年代后期以前，我国西北干旱、半干旱地区的地气温差大部分年份偏低，低于平均值，而从70年代后期之后到2000年，我国西北干旱、半干旱地区的地气温差偏高。此外，本文还分析了西北干旱区地气温差变化的最大地区新疆西部春季地气温差与我国夏季降水的相关关系，其正相关区分别位于西北地区、东北地区和长江流域，而负相关区分别位于华北地区东部和西南地区，这表明我国西北干旱、半干旱区春季地气温差可能是华北地区夏季降水年代际变化的原因之一。

The characteristics of interdecadal variability of summer precipitation and its possible cause are analyzed by using the observed data of summer precipitation for recent 50 years from 1951 to 2000 and the observed data of surface temperature （Ts） and surface air temperature （Ta） for forty one years from 1960 to 2000. The results analyzed from summer precipitation in China show that the interdecadal variability of climate in China is very obvious during recent 50 years. The abrupt change of climate in China occurred in 1976. From 1977 to 2000, summer precipitation obviously decreased and the persistent droughts occurred in North China and the Yellow River basin. Moreover, the analyzed results also show that evolution trend of summer precipitation anomalies in Northwest China is about 5-8 years earlier than that of in North China. In order to investigate cause of the interdecadal variability of climate in China, the difference between surface temperature （Ts） and surface air-temperature （Ta） , i.e. , Ts - Ta in the arid and semi-arid region of Northwest China are analyzed. The analyzed results show that the Ts - Ta, also appeared an obvious interdeeadal variability. Before the late 1970s, Ts-Ta, anomalies were negative, but its anomalies became largely positive from the late 1970s to 2000. the largest positive anomaly value are in the western of Xinjiang Province. The correlations between summer precipitation in whole China and the Ts- Ta in the western of Xinjiang Province in spring from 1960 to 2000 show that positive correlation regions is in Northwest China, Northeast China and the Yangtze River basin respectively, but negative correlation region is in east of North China and Southwest China respectively. Therefore, the interdecadal variability of Ts - Ta in arid and semi-arid region of Northwest China in spring may are one of some causes of interdecadal variability of summer precipitation in North China.