Abstract
Reliable aerosol optical depth (AOD) data with high spatial and temporal resolutions are needed for research on air pollution in China. AOD products from the Advanced Himawari Imager (AHI) onboard the geostationary Himawari-8 satellite and reanalysis datasets make it possible to capture diurnal variations of aerosol loadings. However, due to the different retrieval methods, their applicability may vary with different space and time. Thus, in this study, taking the measured AOD at the Aerosol Robotic NETwork (AERONET) stations as the gold standard, the performance of the latest AHI hourly AOD product (i.e., L3 AOD) was evaluated and then compared with that of two reanalysis AOD datasets offered by Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) and Copernicus Atmosphere Monitoring Service (CAMS), respectively, covering from July 2015 to December 2017 over China. For all the matchups, AHI AOD shows the highest robustness with a high correlation (R) of 0.82, low root-mean-square error (RMSE) of 0.23, and moderate mean absolute relative error (MARE) of 0.56. Although MERRA-2 and CAMS products both have lower R values (0.74, 0.72) and higher RMSE (0.28, 0.26), the former is slightly better than the latter. Accuracy of AOD products could be mainly affected by the pollution level and less affected by particle size distribution. Comparisons among these AOD products imply that AHI AOD is more reliable in regions with high pollution levels, such as central and eastern China, while in the northern and western part, MERRA-2 AOD seems more satisfying. The performance of all the three AOD products presents a significant diurnal variety, as indicated by the highest accuracy in the morning for AHI and at noon for reanalysis data. Moreover, due to various pollution distribution patterns and meteorological conditions, there are distinct seasonal characteristics in the performance of AOD products for different regions.
Highlights
Atmospheric aerosols play an important role in the climate system by scattering and absorbing solar radiation, and have a severely adverse influence on human health [1,2,3]
Considering AODmerged can give a maximum number of aerosol retrievals and better performance compared with AODpure and AODoriginal [19], we only focus on the AODmerged dataset and compare it with reanalysis datasets from MERRA-2 and Copernicus Atmosphere Monitoring Service (CAMS)
Collection 5 aerosol optical depth (AOD) products of Moderate Resolution Imaging Spectroradiometer (MODIS)/Terra and MODIS/Aqua retrieved by Dark Target (DT) algorithm are used in MERRA-2 aerosols
Summary
Atmospheric aerosols play an important role in the climate system by scattering and absorbing solar radiation, and have a severely adverse influence on human health [1,2,3]. Several institutes have produced and released reanalysis aerosol products, such as the Modern-Era Retrospective Analysis for Research and Applications Aerosol Reanalysis (MERRAero) covering the period from January 2002 to February 2012 provided by the National Aeronautics and Space Administration (NASA) Global Modeling and Assimilation Office [10], the Navy Aerosol Analysis and Prediction System aerosol reanalysis product covering the years of 2003–2015 developed by US Naval Research Laboratory [11], and the reanalysis of earlier Monitoring Atmospheric Composition and Climate (MACC) project covering the years of 2003–2012 [12]. Related results could provide guidance for better usage of various AOD products in China
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