| Atmospheric aerosol refers to a system composed of various solid and liquid particulate matter suspended in the atmosphere.With the acceleration of global industrial development and urbanization,a large number of aerosols(such as PM2.5)emitted have a significant impact on the natural environment,human health and global climate change.Obtaining accurate spatial and temporal information of aerosol three-dimensional parameters is the basis for clarifying the aerosol environment,health,and climate effects and their physical processes.However,active and passive remote sensing satellites have many shortcomings when acquiring information on the spatial and temporal distribution of atmospheric aerosols,such as insufficient time resolution or lack of vertical information.MERRA-2（Modern-Era Retrospective Analysis for Research and Applications,version 2）is a global high-resolution aerosol assimilation and reanalysis data.It has high time resolution,wide spatial resolution and provides aerosol vertical information,which can fully supplement the deficiencies of active and passive satellites.However,the data accuracy of MERRA2 aerosol extinction coefficient has not been verified in detail,especially for heavily polluted areas.Therefore,to solve the above problems,based on the high-precision CALIPSO aerosol vertical information,the MERRA-2 aerosol extinction coefficient is obtained by inversion.And from a single profile case analysis,different seasons,different altitudes,and different aerosol types,a full comparison to verify the similarities and differences between them.The distribution and profile changes of MERRA-2 aerosol extinction coefficient in a typical heavily polluted area in China are discussed.The specific conclusions obtained are as follows:1)Based on the profile data of aerosol three-dimensional mass mixing ratio provided by MERRA-2,combined with the influence of aerosol moisture absorption growth law and refractive index,the MERRA-2 aerosol extinction coefficient profile is calculated by Mie scattering theory.The statistical comparison shows that the overall vertical trend of the extinction profiles of MERRA-2 and CALIPSO are in good agreement,and the correlation coefficients are both greater than 0.9.2)The overall performance of MERRA-2 and CALIPSO is relatively consistent in different seasons and at different heights.In different seasons,the relative root mean square error of the two fluctuates around 2.0%;at the same time,natural aerosol and anthropogenic aerosol has little effect on the consistency of the aerosol extinction coefficient of MERRA-2 and CALIPSO.3)In different levels.With the continuous increase in altitude,the relative root mean square error of MERRA-2 and CALIPSO increased from 0.8%to 1.6%.Therefore,the consistency of the two is better at low altitude where more aerosols are distributed（approximately below 6.0 km）,and the consistency will be slightly worse at clean high altitude（approximately more than 15 km）.4)Overall,the extinction coefficients of MERRA-2 and CALIPSO are similar,and the RRMSE is less than 2%.Especially for strong aerosols,both can better characterize the aerosol extinction information and change trend.This study achieved the verification and analysis of the accuracy of MERRA-2aerosol extinction coefficient by comparing it with CALIPSO aerosol extinction coefficient,and fully understood the aerosol distribution of MERRA-2 in polluted areas in China.This has a certain reference value for the observation of three-dimensional aerosol distribution,is conducive to promoting the research of climate effects in heavily polluted areas,and has important scientific value and practical needs. |
