Profiles of aerosol optical properties derived from retrieval algorithms that combine airborne lidar multiwavelength backscatter and MODIS measurements are presented. These retrievals include techniques that employ a combination of measured radiances and aerosol optical thickness and particle size measurements from MODIS along with multiwavelength lidar backscatter measurements to derive profiles of aerosol fine mode fraction and effective radius. Multiwavelength lidar profiles of aerosol backscattering acquired by the NASA Langley airborne DIAL system over the Pacific Ocean during the TRAnsport and Chemical Evolution over the Pacific (TRACE-P, 2001) campaign and over eastern U.S. coastal region during the Intercontinental Chemical Transport Experiment-North America (INTEX-NA, 2004) campaign are used in the retrievals. Results from these retrievals are evaluated using airborne in situ and remote sensing measurements. During INTEX-NA, bias differences between the aerosol extinction values retrieved from the combined lidar+MODIS retrievals (588 nm) and the in situ measurements were about 0.007 km-1 (13%). Profiles of aerosol effective radius and fine mode fraction derived from the combined lidar+MODIS retrievals are also examined using airborne in situ measurements.

Aerosol extinction profiles simulated by the Goddard Chemistry Aerosol Radiation and Transport (GOCART) global aerosol transport model for these campaigns are evaluated using the lidar retrieval results. During TRACE-P, which occurred over the western Pacific Ocean during March-April 2001, the GOCART aerosol extinction profiles were generally 10-40% lower than profiles derived from the airborne DIAL system; greatest relative differences were near the top of the boundary layer (~1 km). During INTEX-NA, which occurred over the northeastern U.S. and western Atlantic Ocean during July-August 2004, the GOCART aerosol extinction profiles showed better agreement, with differences generally largest in the lowest 1 km.

Results from the combined lidar+MODIS retrievals, comparisons with in situ measurements, and evaluations of the GOCART simulations will be presented.