Climatic Analysis Of Observation From Multiple Sources And Modeling Study Of Atmospheric Environment In Central China

Based on the observational data of haze occurrences from 1962 to 2011 and MODIS aerosol products from 2005 to 2014, the climatology of regional haze pollution, aerosol optical depth (AOD), Angstrom exponent (a) and fine mode fraction (FMF) were analyzed. A regional air quality forecasting system was constructed based on WRF-Chem, which has been used to simulate the severe haze pollution happened in the city clusters over Central Yangtze river region during Nov 18th to 25th,2014. The effects of landuse change on meteorology and aerosol concentration in haze event has been studied. It was found:(1) Haze pollution occurred frequently in the areas of northern-central Henan, western-central Hubei and central Hunan, where the population was relatively dense with high aerosol concentrations. The station with the most frequent haze events was Xinxiang in Henan province, reaching 79.1d/a. The seasonal variations showed that the heaviest haze pollution happened in winter and the slightest haze occurred in summer. Haze pollution was a typical atmospheric environment incident in winter over Central China. These seasonal differences became obscure with the increases of haze frequency in spring, summer and fall. High haze pollution was spatially centered over the urban area. The increasing and decreasing trends in haze occurrences have been identified respectively in the polluted region and the relatively clean region over the recent 50 years, revealing the polarization in air environment change over Central China. Haze events in Central China were highly related to the increasing anthropogenic emissions and the decreasing East Asia monsoon over the region during the past 50 years.(2) The spatial distribution of AOD showed an eastern high and western low pattern, while a and FMF showed a distribution of western high and eastern low. High AOD, low a and FMF were found in the dense-populated region, while low AOD, high a and FMF were found in western Central China where the population was sparse. AOD has been found high in spring and summer, but low in fall and winter. Both a and FMF were high in summer and fall, but low in spring and winter. Central China showed a decreasing trend in AOD and an increasing trend in a and FMF during the 10 years. It was shown that AOD decreased significantly in spring and fall while a and FMF increased in spring and winter. The relative clean station showed a decreasing trend in AOD, but presented no clear trend in FMF.(3) Based on the air quality modeling system, it was found that the landuse change in urbanization could increase the concentration of aerosols in haze events happened in the city clusters over Central Yangtze River region. The expansion of cities led to the increase in roughness, weakening the near surface wind speed, which was not favorable to the transport of pollutants from source region in cities to the downwind region. After urbanization, the average temperature and boundary layer height increased in 14h, while they decreased in 2h. The landuse change contributed to a sharper decreasing of temperature during night. Moreover, the increase in aerosol concentrations happened mainly in the boundary layer below 500m.