CALIPSO lidar level 3 aerosol profile product: version 3 algorithmdesign

The Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) level 3 aerosol profile product reports globally-gridded, quality-screened monthly mean aerosol extinction profiles retrieved by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). This paper describes the quality screening and averaging methods used to generate the version 3 product. The fundamental input data are CALIOP level 2 aerosol extinction profiles and layer classification information (aerosol, cloud, and clear-air). Prior to aggregation, the extinction profiles are quality-screened by a series of filters to reduce the impact of layer detection errors, layer classification errors, extinction retrieval errors, and biases due to an intermittent signal anomaly at the surface. The relative influence of these filters are compared in terms of sample rejection frequency, mean extinction, and mean AOD. The extinction QC flag filter is the most influential in preventing high-biases in level 3 mean extinction, while the misclassified cirrus fringe filter is most aggressive at rejecting cirrus misclassified as aerosol. The impact of quality screening on monthly mean aerosol extinction is investigated globally and regionally. After applying quality filters, monthly mean AOD is reduced by −24 and −31 % for global ocean and global land, respectively, thus indicating the importance of quality screening.