沈阳两次降水过程中能见度的变化特征

利用2011年7月29-31日，8月27-29日沈阳大气成分观测站的能见度资料，统计分析了能见度与降水强度、PM₁₀、PM _2.5、PM _1.0质量浓度、风速、相对湿度等气象要素的相关性。结果表明: 7月29-31日降水过程特点为个别时间内降水量较大，8月27-29日降水过程特点为持续几个小时都有较大降水量；7月29-31日和8月27-29日降水过程中，初期降水对PM的湿清除效果较好，后期随着降水强度的增加，能见度有所降低；7月29日0时-31日23时期间内，PM质量浓度在降水过程中出现5 μg?m^-3左右的低值是因为降水和较大风速的双重作用，而8月27日0时-29日23时期间内的降水过程中，风速较稳定，PM质量浓度的改变量相对较小；7月29日-31日和8月27日-29日降水过程中，平均风速与PM₁₀、PM _2.5、PM _1.0的变化趋势均呈反相关，较高的相对湿度有利于PM质量浓度的上升；7月29-31日和8月27-29日降水过程中，能见度与PM _2.5/PM₁₀、PM _1.0/PM₁₀的比值变化趋势均呈明显的反相关。随着颗粒物粒径的减小，其与能见度的相关性逐渐增加。

Characteristics of visibility during two precipitation processes in Shenyang

Using the visibility data on July 29 to 31, August 27 to 29,2011 in Shenyang atmospheric composition monitoring station, the correlation of visibility with meteorological elements such as precipitation, mass concentra- tions of PM10 ,PM2.5 and PM1.0 ,wind speed,relative humidity were analyzed. The results show that the features of two precipitation processes on July 29 to 31 （ the first process） and August 27 to 29 （ the second process） are dif- ferent. The rainfall amount is greater in a certain time for the former, while it is greater in few continuous hours for the latter. The wet cleaning effect is better to particle matter during the early precipitation for two processes, while the visibility decreases during the later precipitation with the increasing precipitation intensity. The mass concentra- tion of particle matter has a low value about 5 μg·m- 3 because of the action of precipitation and large wind speed together in the first process, while it changes insignificantly because of the stable wind speed in the second process. The correlation of the mean wind speed with mass concentrations of PMlo, PM2. 5 and PM1.0 is negative in two processes. The high relative humidity is favorable to the increase of the particle matter mass concentration. The cor- relation of the visibility with the ratios of PM2.5 and PM10, PM1.0 and PM10 is also negative. The correlation be- tween the particle matter and visibility is gradually increasing with the decreases of the particle size.