Exploring geometrical stereoscopic aerosol top height retrieval from geostationary satellite imagery in East Asia

Abstract. Despite the importance of aerosol height information for events such as volcanic eruptions and long-range aerosol transport, spatial coverage of its retrieval is often limited because of a lack of appropriate instruments and algorithms. Especially, geostationary satellite observations provide constant monitoring for such events. This study assessed the application of different viewing geometries for a pair of geostationary imagers to retrieve aerosol top height (ATH) information. The stereoscopic algorithm converts the lofted aerosol layer parallax, calculated using image-matching of two visible images, to ATH. The sensitivity study prospects a reliable result using a pair of Advanced Himawari Imager (AHI) and Advanced Geostationary Radiation Imager (AGRI) images at 40° longitudinal separation. The pair resolved aerosol layers above 1 km altitude over East Asia. In comparison, aerosol layers must be above 3 km to be resolved by paired AHI and Advanced Meteorological Imager (AMI) images at 12.5° longitudinal separation. Case studies indicate that the stereoscopic ATH retrieval results are consistent with aerosol heights determined using extinction profiles from the Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP). Comparisons between the stereoscopic ATH and the CALIOP height, defined by extinction coefficient data, indicated that 71.3 % of ATH estimates from the AHI and AGRI are within 2 km of CALIOP heights, compared with 49.3 % from the AHI and AMI. The ability of the stereoscopic algorithm to monitor hourly aerosol height variations is demonstrated by comparison with a Korea Aerosol Lidar Observation Network dataset.