| With the development of urbanization and industrialization, more and more pollutants aredischarged to the atmosphere. The changing concentration of pollutants, as a consequence,may alter atmospheric physical characteristics such as the radiation and energy balance,properties of cloud condensation nuclei, and cloud forming in the local or regional domain.Though there is no known meteorological cause for weekly cycling of environmentalvariables, weekly cycles have been discovered at local to global scales, particularly in areasaffected by human urbanization. In addition, weekly cycles of the concentration ofanthropogenic aerosols also have been observed in many regions around the world. Since thereis no known natural process that creates a periodicity of seven days that prevails for a longtime, the existence of such a periodicity is a strong indication of human influence on climate.Analysis of day-to-day aerosol-meteorology interactions can help to improve ourunderstanding of how weather and long-term climate respond to aerosol forcing. Based on theroutine observational meteorological element data, API and NCEP/DOE reanalysis data during1980-2009over Beijing and adjacent regions, the weekly circulation characteristics of API,precipitation and several other meteorological elements have been analyzed, and a preliminaryproof of the possible effects of aerosol on precipitation has been presented in this paper. Theconclusions are as follows:(1)API shows an evident weekly cycle, which reach the minimum values on Sunday, andthen increase to the maximum values on Wednesday. The differences between the maximumand the minimum is accepted at the5%confidence level, the period of4to8days aresignificant both in the spectrum analysis and the wavelet, its explained variance reaches27%.PM10has a good positive correlation with population in summer, the correlation coefficient is0.664. However it has a bad correlation withPM10. In the samples of high-ΛPM10stations,PM10shows a significant weekly cycle, while in the low-ΛPM10stations, the spectrum value of6-8day period is low and the periodogram vary little with the frequency. The weekly cycle ofPM10is objected at the5%confidence level.(2) The precipitation frequencies, especially for the light rain, demonstrate a significantweekly change with opposite phase distributions to that of API, the maximum appears on the weekend, and the minimum shows on Wednesday, at a confidence level of95%, the differenceof the max and min is significant in the chi-square test. The period about7days is significantin the spectrum analysis. In the high-ΛPM10stations, the characteristic of weekly cycle issignificant, and it has similar phase distribution with the sample of composite sample. As forthe24-hourly accumulated precipitation amount, aerosols play a trivial effect on it, and theresults are rejected at the5%confidence level.(3) Several meteorological parameters show a significant weekly cycle distribution, cloudamount anomaly, daily temperature anomaly in the lower troposphere, atmospheric stabilityanomaly, updraft frequency in the lower troposphere between925and850hPa levels andhorizontal velocity anomaly in the surface have a similar phase in the weekly change, with thelargest values around the midweek, and smallest values in the weekend. However, dailytemperature anomaly in the surface and vertical wind velocity anomaly show an oppositephase. Most of the differences of both the weekly max and min value and the weekend andmidweek mean value are significant at the5%confidence level.(4) According to the weekly variation characteristics of cloud amount, temperature,relative humidity, atmospheric stability and wind speed, the paper hypothesis that there is afeedback mechanism for aerosol-meteorology interaction:The changes in the atmospheric circulation may be triggered by the accumulation of APIthrough diabatic heating of lower troposphere. |
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