HR: 08:00h
AN: A41E-01 INVITED     [Abstracts]
TI: Rethinking the use of fine-mode optical depth in global-scale, observation-based assessments of anthropogenic aerosol
AU: * Anderson, T L
EM: tadand@u.washington.edu
AF: University of Washington, Department of Atmospheric Sciences Box 351640, Seattle, WA 98195-1640 United States
AB: In terms of both mass and light extinction, the atmospheric aerosol exhibits two dominant modes: a fine mode associated with combustion and/or secondary particles and a coarse mode associated with primary particles such as dust and sea salt. In-situ techniques can separate these modes by mechanical impaction. Remote techniques can estimate fine/coarse partitioning by examining the wavelength dependence of optical depth. Fine-mode aerosol optical depth, therefore, represents a logical point of intersection between global-scale satellite observations, on the one hand, and detailed optical/physical/chemical measurements using in-situ techniques, on the other. While this potential coupling between satellite and in-situ methodologies represents an outstanding opportunity for the in-situ measurement community, it represents a severe challenge as well. To frame the discussion, a reasonable target is to participate in developing a fine-mode satellite product that will provide firm observational constraints for chemical transport models. Currently available satellite fine-mode products are unsuitable because they are unvalidated - that is, their accuracy and uncertainty have not been established by an independent method. Only in-situ techniques can provide this independent measurement, but doing so requires overcoming four major obstacles: (i) efficient sampling of coarse-mode particles, (ii) accounting for the effects of relative humidity, (iii) characterizing aerosol throughout the atmospheric column, and (iv) achieving adequate collocation in time and space. A validation study using data from the ACE-Asia field campaign (Spring, 2001) will be used to illustrate these difficulties and to develop strategies for future progress.
UR: http://www.atmos.washington.edu/~cheeka/aafmf/aafmf.html
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0360 Radiation: transmission and scattering
DE: 0365 Troposphere: composition and chemistry
DE: 0394 Instruments and techniques
DE: 1640 Remote sensing (1855)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005