An improved algorithm for retrieving the fine-mode fraction of aerosol optical thickness, part 1: Algorithm development

• Published in: Remote sensing of environment Vol. 192; pp. 87 - 97
• Main Authors: Yan, Xing, Li, Zhanqing, Shi, Wenzhong, Luo, Nana, Wu, Taixia, Zhao, Wenji
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.04.2017
• Subjects: Aerosol fine-mode fraction; aerosols; algorithms; AOT; China; governmental programs and projects; Japan; moderate resolution imaging spectroradiometer; MODIS; particulates; PM2.5; pollution; remote sensing; satellites; China; Japan; Aerosol fine-mode fraction; AOT; MODIS; PM2.5
• ISSN: 0034-4257; 1879-0704; 1879-0704
• DOI: 10.1016/j.rse.2017.02.005

The fine-mode fraction (FMF) can be a useful tool to separate natural aerosols from man-made aerosols and to assist in estimating surface concentrations of particulate matter with a diameter<2.5μm. A LookUp Table-based Spectral Deconvolution Algorithm (LUT-SDA) was developed here for satellite-based applications using data such as MODerate resolution Imaging Spectroradiometer (MODIS) measurements. This method was validated against ground-based FMF retrievals from the Aerosol Robotic Network (AERONET). The LUT-SDA was then applied to two MODIS-retrieved aerosol optical thickness (AOT) products for the period of December 2013 to July 2015: the MODIS Collection 6 (C6) Dark Target (DT) AOT product and the simplified high-resolution MODIS Aerosol Retrieval Algorithm (SARA) AOT product. In comparison with the MODIS C6 FMF product in three study areas (Beijing, Hong Kong, and Osaka), FMFs estimated by the LUT-SDA agreed more closely with those retrieved from the AERONET with a very low bias. Eighty percent of the FMF values fell within the expected error range of ±0.4. The root mean square error (RMSE) was 0.168 with few anomalous values, whereas the RMSE for the MODIS FMF was 0.340 with more anomalous values. The LUT-SDA FMF estimated using SARA AOT data conveys more detailed information on urban pollution than that from MODIS C6 DT AOT data. As a demonstration, the seasonally-averaged spatial distribution of the FMF in Beijing was obtained from the LUT-SDA applied to SARA AOT data and compared with that of the AERONET-retrieved FMF. Their seasonal trends agreed well. •A satellite-based algorithm retrieving FMF by LUT and SDA is originally proposed.•This method is successfully applying to two MODIS AOT products, DT and SARA AOT.•The derived FMF has a worldwide spatial coverage and a good retrieval accuracy.•The seasonally averaged FMF in Beijing has a close agreement with AERONET FMF.