| Due to rapid development of industrialization and urbanization, and the growth of aerosol particles released into atmosphere, haze occurred frequently, which makes a great influence on human health, climate change, ecosystem and environment. Few studies focus on the characteristics of vertical direction of atmosphere when haze happens. Atmospheric mixed layer height (MLH) has a significant effect on haze and haze also can cause the change of MLH.The MLH in Xianghe, Hebei are continuous observed by laser radar in nearly a year. And the diurnal variation of MLH is discussed combined with meterological conditions. The results show that, the diurnal variation of MLH is closely related to the temperature and wind speed. The correlation coefficient is 0.968 and 0.580, respectively. MLH in spring is higher obviously. The development of MLH in autumn and winter are lower. The higher content of aerosol in haze days lead to the higher temperature. Wind speed influence on MLH in haze days greatly.Then, the monthly and seasonal variation of MLH were analyzed. MLH developed strongly during April and May. On the contrary, it was not well developed during October and February. Therefore, The spread of the aerosol vertical scope and diffusion velocity were faster in April and May and hardly lead to haze days. But from October and February, The spread of the aerosol vertical scope and diffusion velocity were week, which bad for aerosol to transfer in the vertical direction and would result in accumulation of aerosol particles near the ground.Lastly, the diurnal variation of MLH in different haze days an seasons are analyzed in case combined with meteorological conditions. The visibility differences on October 30 and November 8,2006 were mainly caused by wind speed. Temperature difference of May 26 and March 24,2007 lead to their visibility differences. Large emission of atmospheric pollution maybe result in the visibility difference between February 8 and February 23,2007. |
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