Validation, comparison, and integration of GOCI, AHI, MODIS, MISR, and VIIRS aerosol optical depth over East Asia during the 2016 KORUS-AQ campaign
Abstract. Recently launched multi-channel geostationary-Earth-orbit (GEO) satellite sensors such as the Geostationary Ocean Color Imager (GOCI) and the Advanced Himawari Imager (AHI) provide aerosol products over East Asia with high accuracy, which enables the monitoring of rapid diurnal variations and the transboundary transport of aerosols. Most aerosol studies to date have used low-Earth-orbit (LEO) satellite sensors, such as the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging SpectroRadiometer (MISR) with a maximum of one or two overpass daylight times per day at mid- to low latitudes. Thus, the demand for new GEO observations with high temporal resolution and improved accuracy has been significant. In this study the aerosol optical depth (AOD) products from three LEO sensors – MODIS, MISR, and the Visible/Infrared Imager Radiometer Suite (VIIRS) – along with two GEO sensors – GOCI and AHI – are validated, compared and integrated for the period during the Korea–United Sates Air Quality Study (KORUS-AQ) field campaign from 1 May to 12 June 2016 over East Asia. The AOD products analyzed here generally have high accuracy, but their error characteristics differ according to the use of several different surface-reflectance estimation methods plus differences in cloud screening. High-accuracy near-real-time GOCI and AHI measurements facilitate the detection of rapid AOD changes, such as smoke aerosol transport from Russia to Japan on 18–21 May 2016, heavy pollution transport from China to Korea on 25 May 2016, and local emission transport from the Seoul Metropolitan Area to the Yellow Sea in Korea on 5 June 2016. These high-temporal-resolution GEO measurements result in more-representative daily AOD values and make a greater contribution to a combined daily AOD product assembled by median-value selection with a 0.5° × 0.5° grid resolution. The combined AOD is more spatially continuous and of higher accuracy than the individual products. This study characterizes aerosol measurements from LEO and GEO satellites currently in operation over East Asia, and results presented here can be used to evaluate satellite measurement bias and air-quality models.