Spatial And Temporal Distribution Characteristics Of Fog Days And Haze Days And Connecting Factors In Yangtze River Delta And Beijing-Tianjin-Hebei

With the rapid development of economy,the expansion of urbanization and industrization of CHINA leads to increasing environment pollution, atmospheric visibility are deteriorating.The spatiotemporal characteristics of haze days and fogdays and connecting factors have been analysed by applying meteorological data from 642 surface weather stations in CHINA from 1960 to 2013.(1)Results show that:the major haze values are distributed in the North China Plain, Sichuan Basin, shanxi, henan, the middle and lower reaches of the Yangtze River; the major fog values are mainly distributed in sichuan basin and chongqing, the north China plain and the shandong area eastern coastal city such as fujian province and Hangzhou. The spatial distribution of first mode of haze in the east of china showed "+-"pattern from north to south. The first modal time sequence was bounded by the mid of 1980s,showing a decreasing variability, the spatial distribution of first mode of fogdays was consistent with the regions, The first modal time sequence was bounded by the mid of 1980s,showing a decreasing variability. The numbers of fog days and haze days in autumn and winter are larger than those in spring and summer.(2)Results show that:In terms of spatial distribution,the major fog values are distributed in east coastal area of Yancheng city, Huangshan mountain and east coastal area of Zhejiang, while the major haze values are distributed in Nanjing, Hangzhou, Hefei, Quzhou, together with other surrounding cities. In terms of temporal distribution, the annual fog days in large cities has increased since the 1960s but discreased in 1980s; the fog days at small cities has a time lag compared to the evolution at the large cities. Monthly variation of fog days for the large cities appeared with high frequency in winter and spring while less and least in autumn and summer, Monthly variation of fog days for the small cities displayed bimodal trend, with more fog days in spring and winter. Average number of haze days at large cities and small cities depicted a increasing trend, and the differences in the number of haze days for large and small cities had been widening after 1990s. The rising temperature caused by regional climate change and urbanization and the high aerosol abundanee caused by heavy air pollution led to the major reason of the different variation characteristics of haze days and fog days in Yangtze River Delta region. However, due to the complicated interaction between each influencing factors, intensive investigation is still required for further study.(3)Results show that:In terms of spatial distribution,the major haze values are distributed in Beijing,Tianjin,hebei,xingti and surrounding arera,while the fog days show a decreasing trend from southwest to northeast in BTH aera. T he annual haze days in large cities has increased since the 1970s but discreas ed in 1990s,the differences in the number of haze days for large and small cities had been narrowing after 1990s the haze days at small cities has depicted a increasing trend. The annual fog days in large cities and small cities has depicted a steady trend of fluctuations since the 1970s but discreased in 19 90s. Monthly variation of haze days for the small cities and big cities display ed bimodal trend, with more haze days in spring and winter. Monthly variation of fog days for the large cities and small cities appeared with high frequency in winter and spring while less and least in autumn and summer.the wind speed in the range of 0-3m/s, wind direction in the range of SSW-SSW,relative humidity in the range of 40-50%are favorable condition for the occurrence of haze in BTH area.