新疆北部汛期降水的变化特征

基于新疆北部1961-2007年43站逐日降水资料，分析汛期降水的变化特征。结果表明：小雨、中雨和大雨的降水日数和降水强度均呈增加和增强的趋势，大雨日数和强度变化显著，尤其在2000年以后。进一步的研究发现，湿时期（1987-2007年）相对干时期（1961-1986年），新疆北部汛期的总降水量均是增多的，北疆西北部降水量的增多主要是由于小雨和中雨的增加所致，而天山山区及其北麓，伊犁河谷地区降水量的增多是由大雨增加主导。极端干旱事件呈减少趋势，尤其在近10 a处在低发期，极端湿润事件呈增多趋势。

Analysis on Variation of Precipitation in Flood Season in North Xinjiang

It was pointed out by IPCC’s fourth assessment report in 2007 that precipitation in many regions between 30° N and 80° N was in an obvious increase trend.With global warming,the extreme climate events occurred frequently in recent 20 years.Xinjiang is famous by its arid and semiarid regions,and precipitation occurs mainly in rainy season.Many research achievements showed that it had become warmer and wetter since 1987,but it needs to be further studied.In this paper,the variation of precipitation in flood season was analyzed based on the daily precipitation data from 43 meteorological stations in north Xinjiang during the period of 1961-2007.The results showed that the occurring days and intensity of slight,moderate and heavy precipitation in north Xinjiang were all in an increase trend,especially that of heavy precipitation after 2000.The analyzed results indicated that the total precipitation in flood season in north Xinjiang increased during the rainy period(1987-2007) compared with that during the dry period(1961-1986),and the precipitation increase was mainly caused by the increase of slight and moderate precipitation in northwest Xinjiang,but by heavy precipitation in the Tianshan Mountain and its northern piedmont as well as the Yili Valley.The long dry events were in a decreasing trend,especially in recent 10 years,but the long rainy ones were in an increasing trend.