Weekly Circulation Characteristics of Aerosol and Precipitation and the Possible Influencing Mechanism Analysis in Beijing and Surrounding Areas

Weekly cycles of meteorological parameters have been found in many regions around the world; however, the phase and magnitude of these cycles vary greatly from regions and seasons. Based on the NCEP/DOE reanalysis data and the daily surface station observation data from 1980 to 2009 in Beijing and surrounding areas, the weekend effect of aerosol concentration, precipitation and several other meteorological parameters are analyzed, and a preliminary proof of the possible effects of aerosol on precipitation is given. It is shown that a well-defined weekly cycle appears for the aerosol concentration anomalies, which increase from Sunday to Wednesday and decrease during the later part of the week. The precipitation frequency anomalies, especially for the light rain, also show a significant weekly change, but with an opposite phase distribution comparing with that of aerosol concentration. However, for the anomalies of 24hourly accumulated precipitation amount, the results are rejected at the 5% confidence level, and pollutant concentration plays a trivial effect on the precipitation amount. By analyzing the characters of weekly change of wind speed, cloud amount, relative humidity and atmospheric stability, it is deduced that the changes in the atmospheric circulation may be triggered by non-adiabatic heating of lower layer troposphere through the accumulation of aerosol, which leads to the change of cloud and precipitation. This provides a possible influencing mechanism of an indirect effect on cloud and precipitation by aerosols.