过去60年中国秦岭地区云量变化及原因分析

Analysis on Cloudiness Change in Qinling Mountain Region and Its Possible Reason in Past 60 Years

利用近50年秦岭地区高山站及邻近2个地面站的气象资料、季风指数及海温资料,初步分析了云量的变化特征和原因,结果表明:(1)秦岭地区云量变化呈减少趋势,其中华山站(高山)、华县和西安站(平原)夜间的低云量分别为-1.74%·(10a)-1,-1.56%·(10a)-1和-4.23%·(10a)-1,白天的分别为-0.73%·(10a)-1,-1.94%·(10a)-1和-4.62%·(10a)-1;(2)夜间高山站总云量比平原站减少的多(-1%·(10a)-1),白天减少的少(<-0.6%·(10a)-1);(3)高山站和平原站四季的低云量都是减少的,除了平原站夏季总云量是增加的外,其他季节均减少。云量变化的主要原因是:(1)局地气溶胶冷却作用,导致地面接收太阳辐射减少,使局地对流减弱,造成低云量减少;(2)由于西太平洋副热带高压面积增大,使秦岭地区总云量减少。

Using the different meteorological element data between mountain and plain weather stations,monsoon index and sea surface temperature（SST）,the changing characteristic of cloudiness in Qinling mountain region and its reasons have been investigated.The main conclusions can be summarized as follows：（1） The trends of low and total cloudinesses in Qinling mountain region are decreasing,for low cloudiness,decreasing rate of mountain station（Hua mountain station） and plain stations（Huaxian and Xi′an stations） are-1.74%·（10 a）-1,-1.56%·（10 a）-1,-4.23%·（10 a）-1,respectively at nighttime,and-0.73%·（10 a）-1,-1.94%·（10 a）-1,-4.62%·（10 a）-1 in daytime.（2） For total cloudiness,decreasing rate mountain station is more than that at plain station.（3） For different seasons,low and total cloudinesses at mountain and plain stations are all decreasing,except for summer at plain station.（4） The change reasons for cloudiness in Qinling mountain region are： Firstly,because of the cooling effect of aerosol,the absorbed solar radiation from surface redues,the local convection become weaken and the low cloudiness in Qinling mountain region decrease;Secondly,the strengthening of the Western Pacific Subtropical High,has negative correlation with the total cloudiness in Hua mountain.