Observations and Modeling of the Surface Aerosol Radiative Forcing during UAE2.

Aerosol radiative forcing in the Persian Gulf region is derived from data collected during the United Arab Emirates (UAE) Unified Aerosol Experiment (UAE²). This campaign took place in August and September of 2004. The land–sea-breeze circulation modulates the diurnal variability of the aerosol properties and aerosol radiative forcing at the surface. Larger aerosol radiative forcing is observed during the land breeze in comparison to the sea breeze. The aerosol optical properties change as the onshore wind brings slightly cleaner air. The mean diurnal value of the surface aerosol forcing during the UAE² campaign is about -20 W m^-2, which corresponds to large aerosol optical thickness (0.45 at 500 nm). The aerosol forcing efficiency [i.e., broadband shortwave forcing per unit optical depth at 550 nm, W m^-2 (τ₅₀₀)^-1] is -53 W m^-2 (τ₅₀₀)^-1 and the average single scattering albedo is 0.93 at 550 nm. [ABSTRACT FROM AUTHOR]