Validation of Aerosol Optical Depth Retrieved From CALIPSO Lidar Ocean Surface Backscatter

Abstract

Aerosol optical depth (AOD) from the new Ocean Derived Column Optical Depth (ODCOD) data product derived from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) spacecraft is validated using the ground-based Aerosol Robotic Network (AERONET). Relative to AERONET, ODCOD is shown to provide an unbiased AOD and a root mean squared error (RMSE) of 60%. This is in contrast to the performance of the “standard” CALIPSO AOD retrievals (which first detect/identify aerosol layers, retrieve their extinction profile, and then integrate to obtain AOD) that show a larger RMSE (93%) and a significant negative bias (−20%). ODCOD is also shown to provide a higher-fidelity uncertainty estimate than the standard retrievals with the estimated uncertainties providing a good prediction of the true errors as diagnosed with AERONET. A perturbation analysis is performed to assess ODCOD as a retrieval constraint to improve the profiling capability of CALIOP. This analysis indicates that ODCOD has the potential to improve up to 40% of CALIOP retrievals globally.