【摘要】 以华山站为影响站,其周围华阴、渭南、西安为对比站,通过对影响站与对比站降水之比—地形强化因子(R_o)的变化趋势以及R_o与能见度变化关系的分析,研究了气溶胶对秦岭地形云降水的影响。结果表明:有观测以来R_o逐年递减,1980年后R_o递减更快,减幅达20%;R_o的减小趋势与能见度递减、气溶胶递增相吻合,说明气溶胶的增加抑制了地形云降水;华山1980年后的年平均雨量比1980年前减少了15%,达132mm,而平原地区的减少量不超过3%(16mm)。分析气溶胶抑制地形云降水的物理过程发现,R_o的递减主要是减少了中小雨(日雨量小于30mm)的天数,而对大于30mm的降水影响较小,说明气溶胶对浅薄的生命期较短的地形云降水的抑制作用更明显;在以动力强迫抬升为主的春秋季,气溶胶对地形云降水的抑制作用明显强于平原地区,1980—2004年间降水减少了20%～30%;在热力作用下,气溶胶对地形云降水的抑制作用与平原地区相当。更多还原

【Abstract】 Based on the dataset of observations of precipitation and visibility range since 1954 at the top of Mountain Hua,the ratio between the precipitation at Mt.Hua and at the nearby plain stations,which is defined as the orographic enhancement factor Ro,and the relationship between Ro and visibility,were applied to quantitatively learn the ways that air pollution aerosols suppress orographic precipitation.Ro decreased gradually during the measurement period,and most of the decrease occurred after 1980,about 20%,matched with the decreasing visibility and increasing aerosol,which indicates that enhanced pollution aerosols suppress the orographic precipitation. The decrement of average annual precipitation at Mt.Hua after 1980 was 132mm,15%,com- pared with that before 1980,and while the decrease was about 16mm,3%,at the plain stations. The decrease in Ro is mainly caused by days of the light and moderate rain(daily precipitation of less than 30 mm),but not by days with more than 30 mm,which suggested that the thin short living orographic clouds are much more susceptible to precipitation suppression by air pollution aerosols.Under dynamical uplift,the suppression of aerosol to clouds on the mountain top is stronger than that to clouds at plains,and causes 20%-30% decrease of precipitation at Mt. Hua from 1980 to 2004.On the contrary,for the thermo-dynamically driven clouds,the sup- pression of aerosol is equivalent to clouds on the mountain top and at plains.更多还原