Atmos. Chem. Phys. Discuss., 11, 4599-4630, 2011
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Deriving the effect of wind speed on clean maritime aerosol optical properties using the A-Train satellites
V. P. Kiliyanpilakkil and N. Meskhidze
Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC, USA

Abstract. Relationship between "clean marine" aerosol optical properties and ocean surface wind speed is explored using remotely sensed data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the CALIPSO satellite and the Advanced Microwave Scanning Radiometer (AMSR-E) on board the AQUA satellite. Detailed data analyses are carried out over 15 regions selected to be representative of different areas of the global ocean for the time period from June 2006 to June 2010. Based on remotely sensed optical properties the CALIPSO algorithm is capable of discriminating "clean marine" aerosols from other types often present over the ocean (such as urban/industrial pollution, desert dust and biomass burning). The global mean optical depth of "clean marine" aerosol at 532 nm (AOD532) is found to be 0.052 ± 0.038. The mean layer integrated volume depolarization ratio of marine aerosols is 0.016 ± 0.012, the value representative of sea salt crystals. Integrated attenuated backscatter and color ratio of marine aerosols at 532 nm were obtained to be 0.003 ± 0.002 sr−1 and 0.530 ± 0.149, respectively. A logistic regression between AOD532 and 10-meter surface wind speed (U10) revealed three distinct regions. For surface winds lower than 4 m s−1, the mean CALIPSO-derived AOD532 is found to be 0.02 ± 0.003 with little dependency on the surface wind speed. For surface winds from 4 m s−1 to 12 m s−1, representing the dominant fraction of all available data, marine aerosol optical depth is linearly correlated with the U10, with a slope of 0.0062 s m−1. In this intermediate wind speed region, the AOD532 vs. U10 regression derived here is comparable to previously reported relationships. At very high wind speed values (U10 > 18 m s−1), the AOD532-wind speed relationship showed a tendency toward leveling off, suggesting the existence of some maximum value for maritime AOD. Results of our calculations suggest that considerable improvements to both optical properties of marine aerosols and their production mechanisms can be achieved by discriminating "clean marine" aerosols (or sea salt particles) from all other types of aerosols present over the ocean.

Citation: Kiliyanpilakkil, V. P. and Meskhidze, N.: Deriving the effect of wind speed on clean maritime aerosol optical properties using the A-Train satellites, Atmos. Chem. Phys. Discuss., 11, 4599-4630, doi:10.5194/acpd-11-4599-2011, 2011.
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