Abstract
The geostationary satellite Himawari-8, possessing the Advanced Himawari Imager (AHI), which features 16 spectral bands from the visible to infrared range, is suitable for aerosol observations. In this study, a new algorithm is introduced to retrieve aerosol optical depth (AOD) over land at a resolution of 2 km from the AHI level 1 data. Considering the anisotropic effects of complex surface structures over land, Moderate Resolution Imaging Spectroradiometer (MODIS) bidirectional reflectance distribution function (BRDF) model parameters product (MCD19A3) is used to calculate the surface reflectance for Himawari-8’s view angle and band. In addition, daily BRDF model parameters are calculated in areas with dense vegetation, considering the rapid variation of surface reflectance caused by vegetation growth. Moreover, aerosol models are constructed based on long duration Aerosol Robotic Network (AERONET) single scattering albedo (SSA) values to stand for aerosol types in the retrieval algorithm. The new algorithm is applied to AHI images over Bohai Rim region from 2018 and is evaluated using the newest AERONET version 3 AOD measurements and the latest MODIS collection 6.1 AOD products. The AOD retrievals from the new algorithm show good agreement with the AERONET AOD measurements, with a correlation coefficient of 0.93 and root mean square error (RMSE) of 0.12. In addition, the new algorithm increases AOD retrievals and retrieval accuracy compared to the Japan Aerospace Exploration Agency (JAXA) aerosol products. The algorithm shows stable performance during different seasons and times, which makes it possible for use in climate or diurnal aerosol variation studies.
Highlights
Atmospheric aerosols have profound impacts on the Earth’s radiative balance and the climate through their direct radiative effects, indirect effects, and other cloud-mediated climatic effects [1,2]
To reduce the effect of surface anisotropy on Aerosol optical depth (AOD) retrieval, a bidirectional reflectance distribution function (BRDF) parameter database was built using a minimum standard deviation synthesis method based on historical MCD19A3 data
A daily BRDF model parameter determination method was developed for areas with dense vegetation
Summary
Atmospheric aerosols have profound impacts on the Earth’s radiative balance and the climate through their direct radiative effects, indirect effects, and other cloud-mediated climatic effects [1,2]. To retrieve AOD over bright surfaces, Hsu et al (2004) proposed the deep blue algorithm (DB), based on a precalculated surface reflectance database [18]. Both the DT and DB methods have been applied to MODIS measurements to generate global AOD products [19]. Bilal et al (2013) developed a simplified aerosol retrieval algorithm (SARA) for AOD retrieval over Hong Kong based on MODIS data by combining the aerosol properties derived from an AERONET (Aerosol Robotic Network) station and surface reflectance from the MOD09GA L2 daily surface reflectance product [20]. Polar satellites are good in terms of their global coverage, but they cannot observe the diurnal variation of aerosol properties
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