HR: 0800h
AN: A11C-0076    [Abstracts]
TI: Increasing Cloud Droplet Size with Aerosol: a missing piece towards solving aerosol indirect effect puzzles
AU: * Yuan, T
EM: yuan@atmos.umd.edu
AF: Department of Meteorology, 3417 computer & space sciences building, college park, md 20742
AU: Li, Z
EM: zli@atmos.umd.edu
AF: Department of Meteorology, 3417 computer & space sciences building, college park, md 20742
AB: Since the Twomey effect was proposed in 1977, it has been a common belief that cloud particle size only decreases with aerosol loading. Using NASA's MODIS products, an opposite trend is found, together with a general finding that cloud particle size may increase or decrease with aerosol loading depending on water vapor supply, cloud regime and atmospheric circulation. Convective clouds formed in moist regions show an overwhelmingly positive dependence, as opposed to the negative dependence for stratiform clouds in water-limited regions. The slope of the dependence is driven primarily by water vapor amount that explains 70% of the variance. A new mechanism is proposed to explain this new effect. Consideration of this effect in climate models could lower the estimation of aerosol indirect forcing to agree better with the estimations constrained by the global temperature records. The effect may also help reconcile controversial findings concerning if pollutants suppress or enhance precipitation: suppression in dry regions while enhancement in humid regions. This may offer another explanation for the "south flood and north drought" pattern in Asia.
UR: http://www.atmos.umd.edu/~zli/
DE: 1610 Atmosphere (0315, 0325)
DE: 1640 Remote sensing
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting