Measurements of Aerosol Optical Properties over North China and Its Surrounding Areas in Autumn by Satellite and Ground Based Remote Sensing

Aerosol optical properties over North China and its surrounding areas in autumn have been studied by using Ozone Monitoring Instrument(OMI)level 3 data during 2004-2009. The average aerosol optical depth (AOD) and ultraviolet aerosol index (UVAI) over the most regions are larger than 0.8 and 0.75. High frequency of large value of AOD (>0.4) event was observed in Beijing and its surrounding areas, and high frequency of large value of UVAI event was observed in the southern and middle parts of Hebei Province. Average AOD and UVAI over the cities of North China Plain were larger than 0.7 and 0.60, while the averaged AOD and UVAI values of Zhangjiakou, Chengde, and Yangquan were smaller than 0.6 and 0.65,respectively. Satellite and ground based observations were applied to a haze event on 30 October 2006. The result indicates the haze transported from the North China Plain to the Bohai Sea. EZLidar observation results indicate that most of the polluted aerosols were in the layer less than 1 km, and the peak value of extinction coefficient is 2.15 km^-1 within the altitude of 285 m. CALIOP and back trajectory results indicate that the dust aerosol mixed with polluted aerosols in higher layer, and became polluted dust aerosols. During the haze event, AOD increased from a background value(stardard deviation) of 0.08 (0.04) to 1.17 (0.14) from the measurement of CE-318 at Xianghe station, and the Ângström index increased from 0.90 (0.10) to 1.12 (0.09). The particle size distribution indicated that the ratio of fine particles increased while all of the columns of nuclei, accumulation, and coarse mode increased.