秦岭山区近50年降水差异及可能局地成因探讨

Analysis of Precipitation Differences and Their Local Causes in the Last 50 Years around the Qinling Mountains

利用秦岭山区54个气象站50年以上日降水资料,分析了复杂地形下小区域降水变化差异,探讨了可能的局地成因,结果表明:(1)年均降水量总体为南高北低、西高东低,反映出秦岭阻挡作用和山谷东风回流影响;(2)近50年来区域年降水以减为主,9个增加站位于东部,夏季降水以增加为主,减少站集中在秦岭山上和区域西部,降水向夏季集中倾向明显;(3)日雨量小于5mm的年雨量和雨日数减少趋势明显,雨量≥50mm的年雨量和雨日数增加趋势明显,即小雨减少大雨增多;(4)降水变化的多个方面及其与海拔高度和经度对应关系的分析结果,反映出气溶胶抑制地形降水以及成冰作用恢复被抑制降水的作用,说明局地成因中气溶胶起了不可忽视作用;(5)地形作用和区域能量平衡也是重要局地成因。

Using daily precipitation data for more than 50 years around the Qinling Mountains from 54 meteorological observation stations, precipitation differences in this area of complicated terrain are analyzed, and their local causes are discussed. The results showed that： （1） The annual rainfall is generally high in the south and low in the north, and also high in the west and low in the east, which reflects the barrier effect of the Qinling Mountains and the influence of a westward return current of valley wind. （2） A reduction in yearly precipitation dominates the last 50 years; only nine eastern stations among the 54 exhibited increased precipitation. Further, the summer precipitation increased in most stations and de- creased only in a few stations on the flat-topped ridge of the Qinling Mountains and in the western part. The precipitation obviously tends to be concentrated in the summer. （3） The yearly amounts and number of days with daily precipitation of less than 5 mm decreased obviously, and the number of days of daily precipitation greater than 50 mm clearly increased, suggesting an increase in heavy rain and a decrease in light rain. （4） All of these results in the precipitation variation, as well as the precipitation variation with latitude and longitude, reflect the facts that aerosols inhibit orographic precipitation and that ice formation may restore at least some of the inhibited precipitation, which suggests that aerosols play an essen- tial role in the local causes of precipitation differences. （5） The topographic effect and regional energy balance are alsoimportant factors in the precipitation differences.