Constraining the Single Scatter Albedo of Asian Dust Using In-situ Measurements
Abstract
During the Spring of 2001, the optical properties of Asian aerosol were measured in-situ from the National Center for Atmospheric Research C-130 aircraft as part of the Aerosol Characterization Experiment (ACE-Asia). Measurements were made predominantly over the eastern Yellow Sea, east of Korea in the Sea of Japan, and to the north and west of Japan, in the Korean Strait. In most cases, aerosol in this region was found to be either a mix of fine- and coarse-mode aerosol (separated at an aerodynamic diameter of 1micron) or it was dominated by coarse-mode aerosol. The highest aerosol concentrations were nearly always dominated by coarse-mode aerosol, which had a significantly higher single scatter albedo (SSA=0.97) than did the fine-mode aerosol (SSA=0.86). In a first-order analysis, the coarse mode aerosol is assumed to be mineral dust when it is non-hygroscopic. Here we address the issue of how to use these optical measurements, combined with size distribution, chemical and morphological data to constrain the single scatter albedo of Asian dust. First we ask how accurately we were able to measure the single scatter albedo of both the total aerosol and - separately - the fine and coarse modes of the aerosol, given uncertainties in the aircraft inlet passing efficiency, plumbing losses, and instrument accuracy. Further, we question whether the coarse mode aerosol can properly be considered "dust". Electron micrograph images of the aerosol indicate that the Asian aerosol was generally a mixture of dust, soot and other components of a variety of morphologies. In many of these images, soot and other constituents appear to be attached to the larger dust particles. Assuming that the non-dust components of the aerosol are more light-absorbing than the dust itself, our measured value of SSA for the coarse mode aerosol only allows us to place a lower limit on the single scatter albedo of the dust alone. Aerosol microphysical (i.e. size distribution) and chemical data are also used to determine the accuracy of calling the sub-micron aerosol "pollution" and the super-micron aerosol "mineral dust". Finally, using a model, we address the question of whether the in-situ constraints on SSA for Asian dust result in improved estimates of radiative forcing for the ACE-Asia study region.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.A72E..05M
- Keywords:
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- 0305 Aerosols and particles (0345;
- 4801);
- 0360 Transmission and scattering of radiation;
- 0365 Troposphere: composition and chemistry;
- 0368 Troposphere: constituent transport and chemistry