| 秦岭地区气溶胶对地形云降水的抑制作用 |
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| 引用本文： | 戴进,余兴,Rosenfeld Daniel,等.秦岭地区气溶胶对地形云降水的抑制作用[J].大气科学,2008,32(6):1319-1332. |
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| 作者姓名： | 戴进 余兴 Rosenfeld Daniel 等 |
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| 作者单位： | 1.陕西省气象科学研究所, 西安 710015 |
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| 基金项目： | 国家自然科学基金资助项目40575004， 科技部公益项目2005DIB3J099 |
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| 摘 要： | 以华山站为影响站, 周围的西安、渭南和华阴作为对比站, 通过影响站与对比站降水之比——地形强化因子(Ro)的变化趋势以及Ro与能见度关系的分析, 定量研究了秦岭地区气溶胶对地形云降水的抑制作用。Ro的演变分析表明: 有观测以来Ro逐年递减, 减幅为14%～20%, 即影响站与对比站相比降水量减少了14%～20%; Ro的减少趋势与能见度递减、气溶胶递增相吻合, 说明气溶胶的增加抑制了地形云降水。Ro的递减主要是减少了中小雨 (日雨量小于30 mm) 的天数, 这种影响对浅薄的生命期较短的地形云降水作用更明显, 对于华山站, 30 mm以下的降水都会受到入云气溶胶的抑制作用, 而西安站为5 mm以下, 入云气溶胶浓度越高, 就有越厚的降水云受气溶胶影响而抑制降水; 在以动力强迫抬升为主的春秋季, 气溶胶抑制华山地形云降水20%左右, 最大可达25%; 在热对流条件下, 气溶胶对地形云和对平原地区云的抑制作用基本相当。不同风速风向下Ro的变化趋势表明, Ro递减随风速增大而加快, 迎风向 (240°～30°) 大风 (≥5 m/s) 时减少降水超过30%。由Ro与能见度关系的定量分析发现, 当能见度在14 km时Ro为1.8左右, 随着能见度的降低Ro逐渐减小, 当能见度小于8 km时，R0约为1.2, 减小了30%左右; 华山对于华阴的Ro与能见度呈线性关系, 相关系数达0.81。最后, 根据研究结果归纳出气溶胶抑制秦岭地区地形云降水的初步物理模型。
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| 关 键 词： | 气溶胶 地形云降水 地形强化因子(Ro) 能见度 抑制 |
The suppression of aerosols to the orographic precipitation in the Qinling Mountains |
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| Dai Jin,Yu Xing,Rosenfeld Daniel and et al.The suppression of aerosols to the orographic precipitation in the Qinling Mountains[J].Chinese Journal of Atmospheric Sciences,2008,32(6):1319-1332. |
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| Authors: | Dai Jin Yu Xing Rosenfeld Daniel and |
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| Institution: | 1.Meteorological Institute of Shaanxi Province, Xi’an 7100152.Institute of Earth Sciences, Hebrew University of Jerusalem, Israel |
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| Abstract: | Based on the dataset of observations of precipitation,visibility and winds since 1954 at the top of Huashan Mountain,the ratio between the precipitation at Huashan Mountain and at the nearby plain stations,which is defined as the orographic enhancement factor(Ro),and the relationship between Ro and visibility,were used to quantitively study the ways that air pollution aerosols suppress orographic precipitation.Ro decreased 14%-20% gradually during the measurement period,which means that the precipitation at the top of Huashan Mountain decreased 14%-20% compared with the precipitation at the plains stations.The indicated trend of Ro matched well with the decreasing visibility and increasing aerosol,which suggests that enhanced pollution aerosols suppress the orographic precipitation.The decreasing trend of Ro is mainly caused by days of the light and moderate rain(daily precipitation less than 30 mm),but not by days with precipitation more than 30 mm,which suggested that the thin short living orographic clouds are much more susceptible to precipitation suppression by air pollution aerosols.The precipitation less than 30 mm and 5 mm,respectively,can be affected by the aerosols entering the clouds for Huashan Mountain and Xi'an stations,which suggests that the more aerosols enter the clouds,the deeper precipitation clouds will be influenced by the aerosols to suppress the precipitation.In the spring and autumn when dynamical lifting plays the leading role,the suppression of aerosol to clouds at the mountain top is stronger than that in plains,and causes about 20% decrease with a maximum of 25% in precipitation at Huashan Mountain.In the summer for the thermodynamically driven clouds,the suppression of aerosol to the clouds at the mountain top and in plains is equivalent.The variations of Ro in different wind directions show that the decreasing trend of Ro increases with the wind speed,and the decrease of orographic precipitation exceeds 30% for 240-030 wind direction and wind speed greater than 5 m/s.The quantitative analyses of Ro and visibility show that Ro decreases from about 1.8 to 1.2 when the visibility changes from 14 to 8 km,and the decrement exceeds 30%.Ro at Huashan Mountain to Huayin stations is linearly correlated with the visibility,and the regression coefficient is 0.81.Finally,a brief physical model that aerosols suppress orographic precipitation is summarized based on the results. |
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| Keywords: | (Ro) |
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