新疆夜雨和昼雨的空间分布和长期变化

 用新疆98个气象站1960—2001年的昼夜降水量资料,分析了冷季（10月到翌年3月）和暖季（4—9月）昼夜降水频率和强度的差异和空间分布。结果表明：新疆暖季分别有两个频率≥55％的夜雨区和昼雨区。夜雨区分别位于西天山北坡和西昆仑山北坡;昼雨区位于阿尔泰山南坡和天山南坡等地。而到了冷季,暖季夜雨和昼雨的条状带相间的格局消失。除了海拔较高的西天山山区和海拔较低的塔里木盆地西部、吐善托盆地分别有小范围的夜雨区和昼雨区外,新疆其他地区的夜雨和昼雨的比例均在45％~55％之间,基本趋于平衡,夜雨和昼雨之差较暖季已明显减弱。对于暖季的大降水事件（一个夜间或白天降水>15 mm）,伊犁河谷、中东天山及天山北坡,昆仑山北坡60％以上发生在夜间,阿尔泰山和塔尔巴哈台南坡、天山东南部盆地地区60％以上发生在白天。另外,还对暖季夜雨区夏季降水的长期变化进行了分析,结果显示,这两个以夜间降水为主的区域,其夜间降水的增加率略大于白天,并不是很明显大于白天降水的增加率。

Spatial Distribution and Long-term Variation of Nocturnal and Daytime Rainfall in Xinjiang

Daily precipitation data from 1960 to 2001 of 98 weather stations in Xinjiang were used to analyze the differences and spatial distributions of daytime and nighttime precipitation frequencies and intensities in cold season (Oct. to next Mar.) and warm season (Apr. to Sep.). Results show that, in warm season, there were two high nighttime precipitation frequencies areas and two high daytime precipitation frequencies areas where the percentages of nighttime and daytime precipitation frequency respectively were ≥55％. The two nighttime precipitation areas were northern slope areas of Tianshan Mountains and Kunlun Mountains. Two high daytime precipitation areas were southern slopes of Artai Mountains and Tianshan Mountains. But in cold season, the daytime and nighttime precipitation distribution was disappeared. Except for west Tianshan mountains in higher elevation and west Tarim basin and Tu-shan-tuo basin in lower where there were some nighttime precipitation and daytime precipitation respectively, the percentages of daytime and nighttime precipitation in other Xinjiang areas were between 45% and 55%, which were basically equivalent. The differences of daytime and nighttime precipitation became unconspicuous compared with warm season. As for warm season heavy rainfall events (12 hour precipitation >15mm), more than 60％ events occurred in nighttime in Ily valley, middle and east Tianshan Mountains, northern slope areas of Kunlun Mountains, whereas more than 60％ events occurred in daytime in southern slopes of Artai Mountains and Tarbarhtai Mountains, and basin area in northeast Tianshan Mountains. Secular trends in the diurnal cycle of precipitation in warm season showed that the nighttime precipitation increasing rate was little more than the daytime increasing rate in regions with high frequency of nighttime precipitation.