Spatial And Temporal Distribution Characteristics Of Particulate Pollution On The Yunnan-Guizhou Plateau And Meteorological Influences

In this paper,the temporal and spatial variation characteristics of particulate pollutants and their influencing meteorological factors in the Yunnan-guizhou Plateau region from 2013 to 2018 are studied.Using the 2013 something 2018 China High resolution air pollution reanalysis(CAQRA)data set and the Merra-2 aerosol data as the particulate matter data,ERA5 re-analysis data,Global Data Assimilation System(GDAS)meteorological data as meteorological data.Firstly,the time scale changes of particulate matter from 2013 to 2018 are discussed,and the particulate matter pollution in Yunnan-guizhou Plateau occurs in March and April Secondly,according to the different sources of air mass,we divided the air mass into four types,and found that type 2 is pollution type,and then discussed in type 2,the influence of meteorological factors on the change of particulate matter concentration was studied,and then the pollution event was screened under Type 2,and the influence of typical weather system on the pollution was studied Finally,a typical pollution process is analyzed in detail to test the rationality of the weather type and weather influence factors.The main findings are as follows:From the year-to-year change point of view,PM2.5 and PM10 in Yunnan-guizhou Plateau are the overall decreasing trend from 2013 to 2018,but the concentration of PM2.5 decreases more obviously,while the concentration of PM10 in Yunnan decreases slightly,the concentration of PM10 in the western part of Yunnan province even increased slightly.March-april is the most polluted month in Yunnan province and december-january is the most polluted month in Guizhou province.In the diurnal variation,9-12 is the time of day when the concentration of PM2.5 is highest.Based on the spatial second mode of EOF analysis,it can be found that the spatial coefficients of Yunnan Province and Guizhou Province are opposite,so the main controlling factors of particulate matter pollution in the two provinces may be different,the most polluted areas in Yunnan are mainly along the western and southern borders,while the most polluted areas in Guizhou are mainly in the northeast near Sichuan Basin.The concentration of particulate matter in Yunnan Province in April is related to the foreign aerosol.,By using Hysplit backward trajectory model,the air mass paths of every 6 hours in March and April from 2013 to 2018 were analyzed by cluster analysis.The cluster number was 4,and the Type 1 was westward(short distance)accounting for 30%Type 2 was the southerly path,accounting for 26%;Type 3 was the westerly path,accounting for 21%;Type 4 was the northeast path,accounting for 2%,accounting for 33 occurrences.In type 2,the pollutant concentration is the highest,which can be considered as the pollution type.In this type,the indo-myanmar trough exists between 700 hpa and 500 hpa in the south coast of Indochina,mainly on 700 hpa,and the deepest part of the trough can reach 14°N,from the surface to 700hPa,there is a southerly wind,which forms a deep transport layer between Indochina and Yunnan,which is favorable for the transport of pollutants from Southeast Asia and surrounding areas to Yunnan.Selection of meteorological factors affecting the concentration of particulate matter between March and April 2013-2018 by stepwise regression analysis,it was found that four meteorological factors,namely surface temperature of 2M(t2m),surface longitudinal wind velocity of 10m(v10),boundary layer height(BLH)and surface relative humidity(rh),contributed significantly to PM2.5 and PM10 concentrations.When t2m is less than 282.7 k,the concentration of PM2.5 and PM10 reaches the maximum,and the concentration of t2m is within the range of 282.7K-287.8 K,the concentration of PM2.5 and PM10 in v10<0,that is to say,the average concentration of PM2.5 and PM10 is very small,and that of PM2.5 and PM10 is southerly when v10>0,the concentrations of PM2.5 and PM10 increased with the increase of wind speed When BLH>130.4 m,the concentration of PM2.5 and PM10 decreased with the increase of the height of the boundary layer.When BLH>1537.7 m,the concentration of PM2.5 and PM10 increased significantly with the increase of the height of the boundary layer.When rh<64.3%,the decrease rate of PM2.5 and PM10 was the fastest,while rh>79.1%,the change rate was not obvious.During the three days before and after the pollution event,t2m in central and western Yunnan province showed an upward trend and then a downward trend,while t2m in eastern Yunnan Province and Guizhou province continued to rise,while v10 in Yunnan-guizhou Plateau region showed an upward trend,BLH in central and western Yunnan province increased continuously,while BLH in eastern Yunnan province and Guizhou province increased firstly and then decreased.Rh in central and western Yunnan province will continue to rise while Rh in eastern Yunnan Province and Guizhou province shows a first-up and then-down trend.The presence or absence of the trough can not represent the strong pollution,and the different positions of the trough line have a great influence on the source and diffusion of the pollution,although the concentration of PM is high near the source,there is no good diffusion condition.At 91°E-93°E,PM can be diffused to Kunming in the northeast of Yunnan Province and Mengzi City in the southeast,the mean concentration of PM2.5 reached the maximum.