Abstract:To well understand the long-term variation characteristics and influence factors of atmospheric visibility and extinction characteristics, data of extinction effect, visibility, relative humidity, and PM2.5 concentrations, had been analyzed in Beijing. It was found that the atmospheric extinction effect in Beijing showed a slow decreasing trend during 1954 to 1967, an increasing trend from the mid- 1960s to 1970s, and then especially since the 1990s a slow downward trend. The variation of visibility was opposite to that of extinction effect. Atmospheric extinction effect over the mountainous regions was lower than that over the plain. Within the plain area, the extinction coefficient in the south was higher than that in the north, but the gap was reduced in the last 10years. Summer was the season with the lowest visibility and winter with the highest in recent years. But it was the opposite before the 1980s. It might result from the change in pollution emission and aerosol chemical components. The visibility reached its peaks at 09:00and 21:00LT, and the valley value of visibility appeared at 06:00and 16:00LT. Atmospheric extinction was affected by both aerosol concentration and relative humidity. The strong atmospheric extinction was generally associated with high RH and high PM concentration, while small extinction effect occurred when RH and PM concentration were low. There was a linear relation between extinction coefficient and PM2.5 mass concentration when RH was lower than 70%. When RH was higher than 70%, the response of extinction coefficient to PM2.5 mass concentration was not observable.
王英, 李令军, 李成才. 北京大气能见度和消光特性变化规律及影响因素[J]. 中国环境科学, 2015, 35(5): 1310-1318.
WANG Ying, LI Ling-Jun, LI Cheng-Cai. The variation characteristics and influence factors of atmospheric visibility and extinction effect in Beijing. CHINA ENVIRONMENTAL SCIENCECE, 2015, 35(5): 1310-1318.