祁连山地区云量的影响因子分析

Analysis of Influencing Factors of Cloud Cover over Qilian Mountain

利用祁连山区4个测站1961-2000年1-12月平均总云量资料，采用合成分析、相关分析和功率谱分析等方法，分析了40年来祁连山区云量与大环流变化的关系。结果表明：祁连山区云量主要受副热带高压、中纬度经（纬）向环流、高原季风和太阳变动影响。当副高面积增大，向北扩展，中纬度纬向环流增强，促使副热带高空锋区北移，冷暖空气在祁连山区交绥次数减少，造成祁连山区云量减少，反之云量增多；高原夏季风强（弱），造成祁连山区云量偏多（少）；当太阳活动强烈时，高原近地面大气层易出现热低压，祁连山湿润下垫面和热低压结合，促使对流云增多。

The relationship between cloud cover variation and atmospheric circulation is analyzed with the January-to-December mean cloud cover data of four stations from 1961 to 2000 over the Qilian Mountain area by composite, correlation and spectral analysis methods. The results show that the cloud cover over the Qilian Mountain area is affected by the Western Pacific subtropical high, Qinghai-Xizang Plateau monsoon, zonal circulation, and solar activities. When the subtropical high area enlarges, moves northwards and intensifies the zonal circulation in mid-latitudes, it thus induces the subtropical front to move northwards, decreases the times of the cold and warm air meeting over the Qilian Mountain area, and eventually causes the decreased cloud cover; and vice versa. The stronger （weaker） the plateau monsoon, the more （little） cloud cover over the Qilian Mountain.