A novel retrieval of daytime atmospheric dust and volcanic ash heights through a synergy of AIRS infrared radiances and MODIS L2 optical depths

Abstract. We present a novel method to retrieve daytime atmospheric dust and ash plume heights using a synergy of infrared hyper-spectral radiances and retrieved visible optical depths. The method is developed using data from the Atmospheric Infrared Sounder (AIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS), both of which are on NASA's Aqua platform, and lends itself to also a χ² height derivation based on the smallest bias between observations and calculations in the thermal infrared window. The retrieval methodology is validated against almost 30 months of dust centroid heights obtained from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIOP) data, and against ash plume heights obtained from the Advanced Along-Track Scanning Radiometer (AATSR) after the Puyehue Cordon Caulle volcanic eruption of June 2011. Comparisons are also made against Goddard Chemistry Aerosol Radiation and Transport (GOCART) climatological aerosol heights. In general there is good agreement between the heights from the CALIPSO data and the AIRS/MODIS retrieval, especially over the Atlantic and Mediterranean regions; over land one there are more noticeable differences. The AIRS/MODIS derived heights are within typically 25% of the CALIOP centroid heights.