Study On Characteristics Of Aerosol Optical Property And Spatio-Temporal Distribution Based On Multi-Source Datasets

Aerosols,as a major component of the Earth-atmosphere system,play an important role in many processes such as atmospheric physics,atmospheric optics and atmospheric radiation,.The climatic effects of aerosols include the direct effects of absorbing and scattering solar radiation,the indirect effects of changing the microphysical properties of clouds,cloud cover,and cloud lifetime by altering cloud condensation nuclei or ice nuclei,semi-direct effects of absorbing aerosols and invigoration effects.The climatic effects of aerosols are extremely complex.It is not only related to the chemical composition,the mixing state of aerosols,optical properties and spatial and temporal distribution of aerosols,but also related to land cover and the temporal and spatial distribution of clouds,and aerosols are highly variable in space and time,which is one of the most uncertain factors in the climate change and has become a research hotspot in the field of atmospheric science.Northwest China and Central Asia belong to arid and semi-arid regions.This region has a wide geographical coverage,low annual precipitation,sparse vegetation,fragile ecological environment and frequent sand and dust weather.In recent decades,as the intensity of human activity has increased,the climate effects of the above regions have become more complicated.The complex interaction between mineral dust aerosols and anthropogenic pollutants can cause significant changes in the chemical composition and the mixed state of the dust particles,which in turn has an important impact on the optical properties of the aerosol and its direct and indirect climatic effects.Therefore,the work has carried out the characteristics of aerosol optical property and spatio-temporal distribution.The optical properties and vertical distribution of dust aerosol during a dust process over northern China in the spring of 2018 was analyzed using satellite data.At the same time,the impact of dust weather on the concentration of particulate matter and air quality was analyzed by using ground station data.Finally,the mechanism of dust weather on the concentration of particulate matter was analyzed by using different levels(surface,500 hPa and 700 hPa)of geopotential height field and wind field data.The spatio-temporal distribution characteristics of the Beijing-Tianjin-Hebei region during the 2013 APEC meeting(APEC Leaders Meeting)were compared and analyzed using ozone monitor instrument(OMI)data.A method combining the ground L2S-SM-II dual-wavelength polarized laser radar,solar photometer,ground meteorological station observation data and HYSPLIT backward trajectory model to effectively distinguish pure dust and polluted aerosol is proposed and optical properties of two types of dust were compared.Using MERRA-2(2nd Edition Modern Research and Application Reanalysis Data)data,the temporal and spatial distribution characteristics of aerosol optical thicknesses of five types of sulfate,black carbon,organic carbon,sea salt and sand dust from 1980 to 2017 were analyzed.Based on the distinction between pure dust and anthropogenic dust,the spatial and temporal distribution characteristics of anthropogenic aerosols along the Silk Road Economic Belt were quantitatively combined with MERRA-2 data.The main conclusions are as follows:(1)The spatial and temporal distribution of AOD for sulfate,black carbon,organic carbon,sea salt and dust from 1980 to 2017 was analyzed using MERRA-2 reanalysis.The results show that five types of aerosols are unevenly distributed globally and have seasonal variations;the global total aerosol optical thickness is the largest in summer(0.137),followed by spring(0.130),and the smallest in winter(0.118);in North America,Eastern China and Central India,sulfate is the dominant aerosol type with the contribution of 66 %,63 % and 42 % to total AOD,respectively,in the Indian Ocean,South Africa and North Africa,sea salt,organic carbon and dust are the main types of aerosols,respectively,with the contribution of 65 %,51 % and 82 %,respectively.There is a clear growth trend for black carbon,sulfate and total aerosols in Eastern China and central India and the linear trend 0.007 /a and 0.0056 /a for total aerosol optical depth in Eastern China and central India,respectively.(2)The aerosol optical depth(AOD),absorbing aerosol optical depth(AAOD)and aerosol index(AI)were over 0.4,0.035 and 1 in northern China from March 27 to 30,2018,respectively.The dust aerosol was mainly distributed in the range of 8 km from the ground,and the volume depolarization ratio was mostly between 0.06 and 0.4,and the color ratio is between 0.6 and 1.2.The concentration of particulate matter in each city changes due to the influence of dust weather to some extent.The strengthening and southward of the Baikal high pressure in the low level was one of the most important weather systems for the dust emission in the southwestern part of Inner Mongolia and the Hexi Corridor;the surface cyclone and low-level shear in the Hetao area were the key factors for the dust emission in the western part of North China;The high-pressure ridge in the Okhotsk Sea area and the low-pressure system on the ground in the northeastern China were helpful to the dust emission in the northeast China.(3)The aerosol index(AI)during APEC in Jing-Jin-Ji region decreases by 6.9 % and 41.9 % respectively,the AOD at 500 nm decreases by 39.3 % and 27.2 %,the absorbable aerosol optical thickness(AAOD)at 500 nm decreases by 40.2 % and 41.7 % respectively,and the single scattering albedo(SSA)of aerosols basically remains unchanged compared with that before APEC,while the SSA at 500 nm after APEC increases by 5.5 %.The aerosol index(AI)during APEC in Beijing region decreases by 10 % and 21 % respectively,the AOD at 500 nm decreases by 49 % and 23 %,the AAOD at 500 nm decreases by 30 % and 50 % respectively,and the SSA of aerosols basically remains unchanged compared with that before APEC,while the SSA at 500 nm after APEC increases by 4 %.(4)Pure sand dust and polluted dust were distinguished by comprehensive use of ground L2S-SM-II dual-wavelength polarized lidar data,solar photometer data,ground weather station data and HYSPLIT model,and their optical properties were compared.The average value of VDR(Volume Depolarization Ratio)for pure dust is higher than the average of polluted dust,and the peaks of pure dust and polluted dust are 0.31 and 0.21,respectively,which indicates dust is non-sepherical.The average value of CR(Color Ratio)for pure dust is higher than the average value of polluted dust,and when the color ratio is greater than 0.8,pure dust dominates.The relationship between VDR and CR indicates that there is a positive correlation between VDR and CR of the two types of dust.A threshold of 0.25 was proposed to distinguish between pure dust and dust by using the frequency distribution of the VDR,and the misclassification rate of them is 20.7 % and 18.6 %,respectively.(5)In the area along the “Silk Road Economic Belt”,the annual precipitation is low,the NDVI is small,and the total AOD is generally large.The average value of natural aerosol AOD is 0.10,and it is larger in spring and summer.The average value of anthropogenic aerosol AOD is 0.14,and it is basically unchanged but greater than in winter.Overall,the average ratio of anthropogenic aerosols to total aerosol AOD varied from 62 % to 65 %.The proportion of anthropogenic aerosols in North Africa is the smallest,which is 32.8 %,and the proportion of anthropogenic aerosols in Eastern Europe is the highest,which is 73.5 %.As the population density increases,the AOD of anthropogenic aerosols also increases.