Publications

Gao, L; Chen, L; Li, J; Li, CC; Zhu, L (2021). An improved dark target method for aerosol optical depth retrieval over China from Himawari-8. ATMOSPHERIC RESEARCH, 250, 105399.

Abstract
Himawari-8 (H8), the first of the new generation geostationary meteorological satellites, carries Advanced Himawari Imager (AHI) sensor with 16 spectral bands from visible to infrared bands. As the spectral bands of AHI in reflectance bands are similar with MODIS, the Dark Target (DT) aerosol retrieval algorithm could be used for obtaining AOD over land with high temporal resolution from AHI measurements. However, the normalized difference vegetation index (NDVI) which was used as a good indicator of surface spectral reflectance is obviously affected by the solar zenith angle and cannot be ignored for AOD retrieval with geostationary measurements. Collocated AHI Level 1b observations and AERONET AOD less than 0.2 have been input into Second Simulation of the Satellite Signal in the Solar Spectrum - Vector (6SV) to calculate the surface reflectance. It can be found that the regression relationships of surface reflectance between visible and shortwave infrared channel are obviously different over different observation sites, even the NDVI is the same. In this study, AHI/H8 AOD over land was retrieved through improving the estimation of surface reflectance relationship by taking into account the land cover, NDVI and scattering angle. This approach has been applied to the AHI/H8 observations in 2018; the global AErosol RObotic NETwork (AERONET) and China Aerosol Research Network (CARSNET) ground-based AOD observations were used to evaluate the quality of AOD retrievals. The comparison results have shown that H8 AODs have good agreement with the ground-based measurements with R larger than 0.8 (N > 1500), and it is even up to 0.95 at Xianghe site. Validation with CARSNET has shown that the performance of H8 AOD is better in the morning than that in the afternoon. The AOD retrieval deviations have been found at those sites located at barren and mixed pixels. When compared with JAXA H8 AOD, it is found that the performance of AOD of this work is better than JAXA H8 AOD at most ground observation sites. More importantly, the AOD product of this work can better depicts the diurnal variation, a unique feature that the new generation geostationary satellite measurements can provide.

DOI:
10.1016/j.atmosres.2020.105399

ISSN:
0169-8095