Observation Analysis Of Aerosol Vertical Structures In Boundary Layer In Winter Based On Intensive Sounding Measurements In Chengdu

Atmospheric aerosol,as an important part of atmosphere,whose concentration and particle size distribution are essential physical parameters in the study that influence on atmospheric environment and climate by atmospheric aerosol.High concentrations of aerosols releasing into the atmosphere often generate the haze weather which not only reduces atmospheric visibility but also harms to human health.The atmospheric boundary layer,as the closest atmosphere to the underlying surface,is the main environmental atmosphere of human existence,and its changes in atmospheric boundary layer structure affects the diffusion ability of atmospheric pollutants.The study of the vertical distribution of aerosol particles in the boundary layer can provide scientific basis for the treatment of atmospheric environment.This essay is based on the high frequency vertical sounding monitoring data of the lower atmosphere meteorological elements and atmospheric particulates in Chengdu during January 1 st to 20th,2017,combining with the ground meteorological site real-time monitoring data,to explore the atmospheric boundary layer structure and the diurnal variation of the aerosol vertical distribution,and comprehensively analyze the meteorological elements and vertical distribution characteristics of aerosols on different pollution degree and a haze pollution process.Research results show that:(1)In the winter night of Chengdu city(including 20:00,23:00,02:00,05:00,08:00),the grounding inversion mostly occurred,average inversion layer thickness is 80 m,average inversion intensity is 2.3 ?/100 m,the average relative humidity under the inversion layer decreases with height,the average relative humidity in the near surface is over 90%,and the prevailing wind direction is northeast.At night,the weather is strong inversion,high humidity and low wind speed that leads to the accumulation of surface aerosol concentration and serious pollution.During the winter daytime(including11:00,14:00,17:00),the atmosphere stratification is unstable,the average temperature decreases with height and the average relative humidity increases with the height,and the aerosol particles have a serrated vertical distribution.(2)The vertical distribution characteristics of aerosol concentration in different pollution levels are obvious:The vertical distribution of aerosol concentration in light pollution day is mainly affected by relative humidity and wind direction;The vertical distribution range of aerosol particles in moderate pollution day is small,mainly affected by wind speed and wind direction;Vertical distribution of aerosol particles in severe pollution days is fluctuant;The concentration of aerosol particles on the ground in fearful pollution day is more than 8 times higher than that of light pollution day.(3)In heavy haze pollution,the characteristics of diurnal variation in the atmospheric boundary layer distinctly impair.The stable boundary layer structure appears 25 times and the convective boundary layer structure appears only 3 times,the boundary layer structure tended to be stable,and the boundary layer height is generally lower than 1000m.The aerosol vertical structure of atmospheric boundary layer is significantly different in the stage of haze pollution,maintenance and dissipation stage:In the stage of haze development,the atmospheric boundary layer aerosol particles are mainly concentrated below the 300m height,and the atmospheric aerosol particles in the surface layer accumulates to trigger haze pollution events;Haze maintenance stage,the particles number concentration in the atmosphere tends to be consistent,the atmospheric boundary layer stability structure had strong atmospheric vertical mixing;In the stage of haze dissipation,the concentration of aerosol particles in the higher altitude firstly decrease with the largest extent,that indicates the free atmosphere affects the dispersion of haze pollution.(4)The increase of wind speed in the atmospheric boundary layer,intensifying the diffusion of atmospheric transport,whose influence on the finer particles is more outstanding,The correlation between temperature and atmospheric particle concentration is negative in the near stratum and positive above the height of 100 meters.Cold lower atmospheric boundary layer,the stability of the high-rise warm atmosphere thermal stratification abates the vertical diffusion of atmospheric pollutants.The increase of relative humidity is conducive to aerosol particles hygroscopic growth and liquid phase chemical reactions,exacerbating the haze pollution.