Evaluation of Landsat-8 and Sentinel-2A aerosol optical depth retrievals across Chinese cities and implications for medium spatial resolution urban aerosol monitoring

• Published in: Remote sensing (Basel, Switzerland) Vol. 11; no. 2; p. 122
• Main Authors: Li, Zhongbin, Roy, David P, Zhang, Hankui K, Vermote, Eric F, Huang, Haiyan
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 10.01.2019
• Subjects: aerosol optical depth (AOD); Aerosol Robotic Network; Aerosols; Air pollution; Algorithms; Cities; Control algorithms; Data acquisition; Environmental monitoring; Human population density; Human populations; Landsat; Landsat satellites; Landsat-8; Meteorological satellites; Monitoring; Optical analysis; Optical thickness; Population density; Quality assurance; Reflectance; Remote sensing; Sentinel-2; Spatial discrimination; Spatial resolution; urban; Urban environments; Beijing China; Hong Kong; Asia; United States > US; China
• ISSN: 2072-4292; 2072-4292
• DOI: 10.3390/rs11020122

In urban environments, aerosol distributions may change rapidly due to building and transport infrastructure and human population density variations. The recent availability of medium resolution Landsat-8 and Sentinel-2 satellite data provide the opportunity for aerosol optical depth (AOD) estimation at higher spatial resolution than provided by other satellites. A year of 30 m Landsat-8 and 10 m Sentinel-2A AOD data retrieved using the Land Surface Reflectance Code (LaSRC) were compared with coincident ground-based Aerosol Robotic Network (AERONET) Version 3 AOD data for 20 Chinese cities. Stringent selection criteria were used to select contemporaneous data - only satellite and AERONET data acquired within 10 minutes were considered. The average satellite retrieved AOD over a 1470 m × 1470 m window centered on each AERONET site was derived to capture fine scale urban AOD variations. AERONET Level 1.5 (cloud-screened) and Level 2.0 (cloud-screened and also quality assured) data were considered. For the 20 urban AERONET sites in 2016 there were 106 (Level 1.5) and 67 (Level 2.0) Landsat-8 AERONET AOD contemporaneous data pairs, and 118 (Level 1.5) and 89 (Level 2.0) Sentinel-2A AOD data pairs. The greatest AOD values (>1.5) occurred in Beijing, suggesting that the Chinese capital was one of the most polluted cities in China in 2016. The LaSRC Landsat-8 and Sentinel-2A AOD retrievals agreed well with the AERONET AOD data (linear regression slopes > 0.96; coefficient of determination r2 > 0.90; root mean square deviation < 0.175) and demonstrate that the LaSRC is an effective and applicable medium resolution AOD retrieval algorithm over urban environments. The Sentinel-2A AOD retrievals had better accuracy than the Landsat-8 AOD retrievals, which is consistent with previously published research. The implications of the research and the potential for urban aerosol monitoring by combining the freely available Landsat-8 and Sentinel-2 satellite data are discussed.