The Effects Of Air Pollution On Radiation Budget And Meteorological Elements Over Beijing

In recent years, with the acceleration of economy and urbanization, pollution is getting more serious, the effect of air pollution on radiation budget and meteorological elements is becoming more significant. This paper used the radiation and automatic stations data(2012-2014) from the 325-m tower in IAP, the southern suburb of observatory, Miyun meteorological tower and Shangdianzi regional atmospheric background station to study the distribution of radiation components and the effects of air pollution on radiation budget over Beijing. By using Weather and Forecasting Model(WRF), adding the Aerosol Op tical Depth of MODIS and the Aerosol Optical Depth vertical profile of heavy pollution day, a winter cloudless day with serious air pollution is simulated, in order to study the effects of air pollution on radiation and meteorological elements.The results from observation data are as follows:(1) The maximum of annual incident short wave radiation appears in May because of the precipitation and cloudiness in Beijing. Contrast the urban and suburban areas, the incident short wave radiation of urban is lower, but the long wave radiation of urban is higher because of the urban heat island effect. The annual change of surface albedo of urban and suburban are small, the annual average surface albedo of urban station is lowest, which is 0.12, the Shangdianzi stat ion is highest, which is 0.21.(2) For the monthly average in winter, the incident short wave radiation of pollution days of all stations are less than clear days, the maximum attenuation is 55.8W/m~2, the maximum attenuation of direct radiation is 161.1 W/m~2; The long wave radiation of pollution days are higher than clear days, the maximum increase of upward and downward long wave radiation are 17.4 W/m~2 and 12.0 W/m~2, the attenuation of long wave radiation is related to the pollution and temperature; Net radiation of pollution days are less than the clear days in the daytime, which is opposite in the night.(3) For the comparison of all stations, the attenuation of incident radiation in the southern suburbs(13.2%) is higher than northern urban areas(7.4%) because of air pollution, which is similar to the distribution of pollutants in Beijing-"North and South are two different worlds”; From the urban area to the northern suburban area, the attenuation rate of pollution on the long and short wave radiation gradually decreases.The simulations and sensitivity tests from WRF for 23 December in 2013 show that:(1) The simulations of the distribution of radiation and meteorological factors in Beijing is better by adding the aerosol optical depth data into WRF.(2) The effect process of pollutions: At first, by changing the vertical net absorption of shortwave radiation, the vertical distribution of temperature is changed; And because of the prevention of air pollution on the short wave radiation, the temperature decreases, the stratification is more stable, the height of boundary layer reduces, the momentum transport of surface layer reduces, so that the wind speed of surface layer also reduces.(3) Because of the effects of air pollution, the attenuation of the short wave radiation in the north six-ring is lower than south, which is 23.7W/m~2, for the vertical direction, the absorption of net short wave radiation of surface layer is 12-13 W/m~2; For the sensible heat flux, the entire area decreases, the southern regi on decreases by 24 W/m~2, which is more than 11 W/m~2 of northern area; For the temperature, the surface is cooler, the reduction of temperature in the north six-ring is lower than south, which is 0.13℃, for the vertical direction, the cooling of southern region of surface layer is more significant than the northern area, which is same to the top heating; For the boundary layer height, the entire area decreases, the average of southern region is 184 m, much higher than the northern region; For the wind speed, it decreases in surface layer but increases in higher layers.(4)Double the concentration of pollutants, the effects of air pollution on the factors become more serious, compared to the northern region, the southern region is more significant. For the dist ribution of shortwave radiation, the attnenuation of southern site incident is biggest, which is 49.4 W / m~2, the northern site is least, which is 14.1 W / m~2; For the temperature, in the surface layer, the south of six-ring decreased 0.5℃, the north aerea decreased only 0.1℃, in the higher layer, the south area increased 0.56℃, the north area increases only half of the south; For the height of the boundary, the southern region decreases 111 m, the northern region only decreases 31 m.The study shows that the effect of the air pollution on radiation budget and meteorological elements over Beijing is significant, so the effect of air pollution must be considered in fine weather forecast. In addition, this research has a certain guiding significance on the gover nance of urban atmospheric environment and the construction of urban planning.