Modulation of the aerosol absorption and single-scattering albedo due to...

Remiszewska, J., P. J. Flatau, K. M. Markowicz, J. Reid, J. S. Reid, and M. L. Witek (2007), Modulation of the aerosol absorption and single-scattering albedo due to synoptic scale and sea breeze circulations: United Arab Emirates experiment perspective, J. Geophys. Res., 112, D05204, doi:10.1029/2006JD007139.

The spectral aerosol absorption properties in the Arabian Gulf region were observed during the United Arab Emirates Unified Aerosol Experiment (UAE2). Measurements were taken at a coastal region of the Arabian Gulf located 60 km northeast of Abu Dhabi, the capital of the United Arab Emirates, allowing characterization of pollution and dust absorption properties in a highly heterogeneous environment. A large observed change of the diurnal signal during the period under study (27 August through 30 September 2004) was due to (1) strong sea and land breeze and (2) changes in prevailing synoptic-scale flow. During the night, stagnating air resulted in gradual accumulation of pollution with maximum absorption in the early morning hours. The rising sun increased both the depth of the boundary layer and the temperature of the interior desert, resulting in strong and sudden sea breeze onset which ventilated the polluted air accumulated during the night. Our observations show that the onshore winds brought cleaner air resulting in decreasing values of the absorption coefficient and increasing values of the single-scattering albedo (SSA). The mean value of the absorption coefficient at 550 nm measured during the sea breeze was 10.2 ± 0.9 Mm1, while during the land breeze it was 13.8 ± 1.2 Mm1. Synoptic-scale transport also strongly influenced particle fine/coarse partition with ‘‘northern’’ flow bringing pollution particles and ‘‘southern’’ flow bringing more dust.

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Radiation Science Program (RSP)