Optical Aerosol Properties Over the Asian Pacific Ocean during ACE-Asia

The effect of aerosol particles on the atmospheric radiative-energy balance at critical locations around the globe is an area or research that to be better characterized. This research has allowed shipboard measurements of climatically relevant ambient-aerosol optical properties between Hawaii and the coast of China to characterize "clean marine conditions" and then along the coast of China to characterize "polluted conditions" and "mineral dust conditions." Aerosol light scattering properties and in particular the increase in light scattering coefficient with increasing controlled relative humidity (f(RH)) during ACE-Asia showed a wider diversity of profiles than during ACE-1, ACE-2 or at a U.S. continental site. During the Pacific crossing, the signature was clearly marine-seasalt dominated (very hygroscopic with large magnitude growth with a clear deliquescent/crystallization hysteresis loop) and quite similar to the background marine conditions of Cape Grim during ACE-1. Other times when flow was off the Asian continent, the dependence of scattering on controlled RH was quite similar to results obtained in Sagres Portugal during outflow of European air masses (ACE-2, hygroscopic with smoother changes in scattering with increasing RH conditions though some deliquescent/crystallization features). When the aerosol consisted of a large part mineral dust species, the hygroscopic growth in light scattering was quite suppressed. Mineral dust dominated aerosols showed very little growth in light scattering as a function of RH and at times was nearly hygrophobic. However, along with the suppressed hygroscopic growth, deliquescent (step-change) features were often more pronounced than the cases of the more hygroscopic urban-industrial influenced aerosols. These results will also be integrated with laboratory light scattering measurements and field absorption measurements for comparison of light scattering and albedo measurements made by other independent techniques/researchers to evaluate closure of light scattering and albedo measurements. Such efforts to obtain closure is important to better understand how results from remote sensing techniques such as satellites agree with measurements made by other methods at the surface of the earth. Information gained from such research will provide valuable inputs to existing global-climate models, which in turn can provide better insights into how to develop better policies related to global climate change.