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.%部分气象要素在某些地区表现出明显的周循环特征,其位相和尺度因时因地而异.利用1980～2009年环北京地区地面常规观测气象要素资料、空气污染指数资料(简称API)及NCEP/DOE再分析资料,本文分析了环北京地区API、降水及多种气象要素的周变化特征,并对气溶胶影响降水的可能机制做了初步证明.分析表明:API表现出明显的周循环特征,周三最大,周日最小；降水频次尤其是小雨频次的周变化特征也较明显,且与API的周变化呈反位相分布；降水量受API影响较小,其周循环特征未通过置信度为95％的显著性检验；基于云量、温度、相对湿度、大气稳定度及风速的周变化特征分析,本文推断,大气气溶胶累积引起对流层低层非绝热加热,导致大气运动发生变化,进而对云和降水产生影响,这为气溶胶间接效应提供了一种可能的影响机制.
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