甘肃河西走廊地区气候暖湿转型后的最新事实

The latest evidences of a warm-wet climatic shift in Hexi Corridor,Gansu

应用1981-2011年甘肃省河西走廊地区19台站逐日降水资料,研究了该区域年和四季降水量、雨日、降水强度的气候变化特征.结果表明:整个河西走廊秋季及酒泉市东部到张掖市冬季降水呈显著增加;夏季雨日显著减少,秋季雨日显著增加;秋季降水强度普遍增强.与1990年代相比,2000年代秋季、春季和冬季降水量占年降水量的比重分别提高了9.4%、3.9%和1.8%,仍有暖湿化倾向,其中,秋季暖湿化显著,而夏季降水比重却减少了15.3%,有暖干化趋势.2000年代降水量、雨日和降水强度极端气候事件明显增加:从季节看,秋季发生频率最高,约占同季全部极端事件的80%左右,其次是夏季和冬季,各占60%,春季和年各占50%;从要素看,雨日发生频率最高,占全部极端事件的近70%,降水量次之,占60%,雨强占50%.与1990年代相比,2000年代500 hPa、200 hPa和700 hPa高度场、相对湿度及比湿有明显的年代际变化,对秋季降水有利而对夏季降水不利.

Based on the daily precipitation data from 19 weather stations in Hexi Corridor of Gansu Province from 1981 to 2011,the change characteristics of precipitation,rain days and precipitation intensity were analyzed. It is found that autumn precipitation increases significantly in the corridor and winter precipitation has an increasing trend from the east of Jiuquan to Zhangye; rain days reduce significantly in summer,but increase in autumn; precipitation intensity increases dispersedly in autumn. The proportions of precipitation in autumn,spring and winter to annual precipitation rose by 9. 4%,3. 9% and 1. 8%,respectively,in the 2000 s as compared with that in the 1990 s. Thus it was still with a warm-wet tendency in these seasons,especially in autumn.However,the proportion of precipitation decreased by 15. 3% in summer,showing a warm-dry changing tendency. The extreme weather events of the three analyzed factors had increased markedly in the 2000s; from the aspect of season,the highest frequency had been in autumn,accounting for about 80% of the total extreme factors events,followed by that in summer and winter,accounting for 60% both. Viewing from the factors,rain day frequency,nearly 70%,was the highest,precipitation frequency,60%,was the second,and precipitation intensity frequency,50%,was the least. Compared with those in the 1990 s,the 200 hPa and 500 hPa height fields in the 2000 s had obvious decadal variation,so did the relative humidity and specific humidity at 700 hPa,which were beneficial to autumn precipitation and unbeneficial to summer precipitation in the 2000 s.