[Change of Atmospheric Pollution Diffusion Conditions in Beijing in Recent 35 Years].

ABSTRACT

In this paper, the monthly average of NCEP(National Center for Environmental Prediction)reanalysis data (2.5°×2.5°),the sounding data, and conventional observation data in Beijing (54511 station) were used to analyze the atmospheric pollution diffusion conditions in Beijing in recent 35 years. The main conclusions werein 1980~2015, the whole layer was warmer. After 1990, the temperature inversion phenomenon was obvious, and the whole air was stable. The cold air's less effect on the lower layer, lower frequency of great north wind speed and surface layer's convergence led to the rising of pollution concentration. The location of sink motion at the high level was lower and that of the ascending motion at the low level was higher. This led to the constriction of the ascending motion below the boundary layer, worsening the pollution diffusion condition. In 1980~1989, the atmospheric capacity index was steady, while in 1990-1999,it fluctuated obviously and after 2000,it declined. In general, the atmospheric capacity presented a gentle decline. In spring and winter of 1980-1989, as well as spring and summer of 1990-2015, the atmospheric capacity was better. After 2000, the atmospheric capacity was decreasing compared to the last 20 years no matter in which season, and the difference of atmospheric capacity in seasons diminished. The boundary layer was higher in spring and summer, and lower in fall and winter in recent 35 years.