利用河西地区15个气象站点1955~2009年日平均气温资料,采用5d滑动平均、气候倾向率、Mann-Kendall和滑动t检验,ArcGIS 中的反距离加权插值等方法分析河西地区四季开始日及其长短变化特征,以揭示气候季节变化对全球气候变暖的响应。结果表明:近55年来,河西地区四季开始日主要表现为春、夏和秋季提早,冬季推迟的变化趋势,其中以夏季变化最为明显,且以21世纪初最为显著。这种趋势在空间分布上存在差异,表现为东部春季开始日提早的趋势比中西部明显;而夏、秋季开始日提早趋势中部大于东西部;冬季开始日的推迟趋势是东部远大于中西部。平均四季长短顺序为:冬季>春季>秋季>夏季。平均四季开始日突变分析表明:春、夏季开始日突变年份一致,均在1997年发生突变,秋季开始日在1993年发生突变,而冬季发生突变的时间较春夏秋3季较早,为1975年。

Based on the daily average temperature data of the 15 weather stations in Hexi area in 1955—2009 and using the methods of climate trending rate, 5 days running mean temperature, Inverse Distance Weighted interpolation, Mann-Kendall abrupt change test and slide t detected method, the average beginning dates and length of four seasons have been analyzed in Hexi area of Gansu province in the same period. The main results are obtained as follows. (1) The season start dates of spring, summer and autumn become earlier, of winter become later, of summer have the most obvious change in recent 55 years. And this trend is the most evident in the beginning of the 21st century when the global warming is significant. (2) This trend has different spatial distribution in Hexi area. The season start dates of spring are more evident in advance in the east than in the middle and west, of summer and autumn are more evident in the middle than in the east and west and the delay of winter is more evident in the east than in the middle and west. (3) In the last 55 years, the averaged beginning dates of summer and autumn were advanced for 9 d and 1.6 d, respectively, and those of spring and winter were delayed for 7.1 d and 7.7 d respectively, and only that of the winter was changing significantly. The averaged lengths of four seasons are 68 d, 51 d, 53 d and 197 d, respectively. (4) The methods of T checking and Mann-Kendall were employed to analyze mutation of start dates. The abrupt change of start dates happened in 1997 in spring and summer while that of autumn appeared in 1993. The abrupt change of winter happened in 1977.