| Atmospheric aerosol is a composite system of fine solid particles and liquid droplets suspending in the air.Atmospheric aerosol is widely distributed and has complicated chemical and physical change,which exerts a negative impact on global climate and environment.In recent years,anthropogenic and natural emissions increase rapidly with the economic development and environment destruction.The aerosol pollution has been one of the most concerned environmental problems.Therefore,it is essential to timely and effectively obtain the aerosol information and analyze its variation characteristic,which can provide scientific basis and technical support for regional aerosol monitoring and pollution control.The main purpose of this dissertation is to investigate the potentiality and feasibility of obtaining the information and variation characteristic of aerosol using PARASOL polarization data and CALIPSO lidar data.The specific objectives of this study were:1)to analyze the variation characteristics of aerosol in three dimensional spaces using the aerosol optical depth(AOD)and the volume percentages of aerosol components estimated from PARASOL polarization data,and the aerosol parameters in the vertical direction extracted from CALIPSO lidar data;2)to investigate the influence of meteorological factors across different height,which are generated based on the AOD data and meteorological data obtained from the WRF model,on aerosol using random forest model;3)to analyze aerosol transmission path,potential distribution and the proportion of anthropogenic source in Yangtze River Delta using HYSPLIT trajectory data.The main research methodologies,results and finding are as follows:(1)The thesis proposed a new method for estimating the AOD using PARASOL polarization data.Compared with the original method for AOD estimation,the new proposed method not only improve the estimation accuracy of AOD,but also simultaneously obtains the volume percentages of aerosol components.Besides,we also employed the CALIPSO lidar data to extract the aerosol vertical parameters,and then analyzed the characteristics of aerosol vertical distribution in Yangtze River Delta.(2)The spatial and temporal variations of AOD were analyzed in Yangtze River Delta using the AOD derived from PARASOL data,and the results implied that the change of annual average AOD was not obvious in Yangtze River Delta region during the period 2008-2013.The largest AOD was observed in spring,followed by summer and autumn,and AOD in winter was minimal.The AODs in spring,summer and autumn have a downward trend,while the AOD has a rising trend in winter.Spatially,the largest AOD was observed in Shanghai and Jiangsu,followed by Anhui over Yangtze River Delta.The minimum AOD was located in Zhejiang.Additionally,the average aerosol composition data of Yangtze River Delta were obtained by analyzing the aerosol composition data.The volume percentages of dust,water-soluble,oceanic and soot particles are 0.482,0.323,0.006 and 0.189,respectively.The volume percentages of dust and soot particles rise yearly.The water-soluble particles declines year by year.The effect of oceanic particles is small and remains stable.The dust and soot particles showed increase trends in different seasons.On the contrary,water-soluble particles had a decrease trends.The aerosol vertical parameters were analyzed using laser radar data and the results indicated that there are obvious regulations in the vertical distribution of aerosols.The aerosols in spring are mainly located in the highest vertical height,have bigger particle size and more significant spherical particle characteristics,and are mainly composed by sand and dust particles.The aerosols in summer were spherical particles with small particle size and strong scattering ability,and mainly distributed in the air with low altitude.The aerosols tend to gather in the air with high altitude in autumn and winter.(3)The influence of meteorological factors on the change of aerosols was also analyzed using the meteorological data derived from WRF model and the inversed AOD.The results demonstrated that the relative humidity and wind speed had the greatest influence on the change of aerosols,and the effect of high altitude meteorological factors is higher than that of low altitude meteorological factors.Additionally,the results indicated that the main factor is quite different in different seasons.Wind speed has greater influence on AOD in spring,followed by relative humidity.In summer,the influence of wind speed on AOD showed decreasing trend while relative humidity showed increasing trend in summer,especially for near surface relative humidity.Relative humidity had more obvious influence on AOD compared with wind speed in upper air.However,the influence of relative humidity in the low altitude significantly decreased.The influence of wind speed on AOD was approximately equal to the relative humidity.(4)Both the backward trajectory and near-surface extinction coefficient of aerosols were firstly calculated to obtain the strength index of input source.Then the aerosol input path and influence area were determined by combining trajectory with near-surface extinction coefficient of aerosols.Finally,the ratio of external and internal input source strength index was calculated,and the output source of aerosols were obtained.The results indicated that the input source of aerosols reached the maximum in spring,followed by winter and autumn,and the least in summer.The external aerosol share was less than 15%in four seasons,which means that aerosols were primarily originated from internal emissions in Yangtze River Delta. |
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