Abstract:

Using the visibility data on July 29 to 31, August 27 to 29 in Shenyang atmospheric composition monitoring station, the correlation of visibility with meteorological elements such as precipitation, mass concentrations of PM₁₀, PM _2.5 and PM _1.0, 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 different. 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 concentration of particle matter has a low value about 5 g﹒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 PM₁₀, PM _2.5 and PM _1.0 is negative in two processes. The high relative humidity is favorable to the increase of the particle matter mass concentration. The correlation of the visibility with the ratios of PM _2.5 and PM₁₀, PM _1.0 and PM₁₀ is also negative. The correlation between the particle matter and visibility is gradually increasing with the decreases of the particle size.

Key words: Visibility, Precipitation, Particle matter