Sensitivity of Aerosol Climate Forcing to the Existing Satellite Observations

Aerosol direct and indirect climate forcing have been extensively studied using numerical models and satellite and ground based observations. Due to their close connection to atmospheric radiative properties, and their high spatial and temporal coverage, satellite observations have been used for model evaluations and estimations of aerosol climate impacts. However, satellite observations, including column integrated parameters such as aerosol optical depth and vertical distributions such as aerosol and cloud profiles from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), are subject to uncertainties of their own. It is therefore necessary to study and propagate the sensitivity of climate studies from the known uncertainties in satellite aerosol retrievals.

In this study, sources of error in passive and active satellite observations that affect climate forcing studies are explored. Examples of such issues include cloud contamination, lower boundary conditions, and calibration. Major discrepancies among satellite aerosol products, such as the elevated high aerosol optical depth zone reported by Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi-angle Imaging SpectroRadiometer (MISR) but not seen in data from several other sensors, are studied. Finally, an ensemble method will be presented for studying aerosol climate forcing using a combination of passive and active sensor observations with a chemical transport model through coupled 2D/3DVAR data assimilation.