Air Pollution Index and Precipitation Weekly Circulation Characteristics and Its Possible Influencing Mechanism Analysis over Beijing and Its Adjacent Regions
环北京地区空气污染指数与降水的周循环特征及其影响机制分析

Weekly cycles of some meteorological parameters have been found in many regions around the world; however, the phase and magnitude of these cycles vary greatly with regions and seasons. Based on the routine observational meteorological element data, the air pollution index (API) and NCEP/DOE reanalysis data during 1980-2009 over Beijing and its adjacent regions, the weekly circulation characteristics of API, precipitation, and several other meteorological elements have been analyzed, and a preliminary proof of the possible effects of aerosol on precipitation has been presented in this paper. The study indicates that API shows an evident weekly cycle, which reaches the minimum values on Sunday, and then increases to the maximum values on Wednesday. However, the precipitation frequencies, especially for the light rain frequency, demonstrate a significant weekly change with opposite phase distributions to that of API. As for the 24-hour accumulated precipitation amount, aerosols play a trivial effect on it, and the results are rejected at the 5% significance level. According to the weekly variation characteristics of cloud amount, temperature, relative humidity, atmospheric stability, and wind speed, the results have been concluded that the cycles may be triggered by the accumulation of aerosols which causes the nonadiabatic heating in the lower troposphere, and then results in the changes of cloud and precipitation. This conclusion provides a possible indirect effect mechanism of aerosols.