HR: 11:20h
AN: A22B-05    [Abstracts]
TI: Aerosol-Cloud Interactions Over the North Pacific Ocean: an Integrated Assessment Using Aircraft, Satellites and a Global Model
AU: * Wilcox, E M
EM: ewilcox@princeton.edu
AF: Princeton University Program in Atmospheric and Oceanic Sciences, NOAA/GFDL P.O. Box 308, Princeton, NJ 08540 United States
AU: Mauger, G
EM: gmauger@ucsd.edu
AF: Center for Atmospheric Sciences, Scripps Institution of Oceanography, 9500 Gilman Dr. Mail Code 0221, La Jolla, CA 92093 United States
AU: Lariviere, O
EM: odelle@fiji.ucsd.edu
AF: Center for Atmospheric Sciences, Scripps Institution of Oceanography, 9500 Gilman Dr. Mail Code 0221, La Jolla, CA 92093 United States
AU: Roberts, G
EM: greg@fiji.ucsd.edu
AF: Center for Atmospheric Sciences, Scripps Institution of Oceanography, 9500 Gilman Dr. Mail Code 0221, La Jolla, CA 92093 United States
AU: Ramanathan, V
EM: vramanathan@ucsd.edu
AF: Center for Atmospheric Sciences, Scripps Institution of Oceanography, 9500 Gilman Dr. Mail Code 0221, La Jolla, CA 92093 United States
AU: Ming, Y
EM: yi.ming@noaa.gov
AF: Princeton University Program in Atmospheric and Oceanic Sciences, NOAA/GFDL P.O. Box 308, Princeton, NJ 08540 United States
AB: Interactions between aerosols and the cloud systems of the North Pacific Ocean were observed by aircraft during the Cloud Indirect Forcing Experiment (CIFEX) in April 2004. The CIFEX project seeks to determine the impact of aerosol indirect effects on the radiative forcing of highly reflective North Pacific clouds under the influence of aerosols traveling across the ocean basin from Asia. Toward this end, CIFEX aircraft observations from the Northeast Pacific of aerosol and cloud microphysics are blended with coincident satellite observations of cloud properties from MODIS and cloud radiative forcing from CERES. The satellite observations are then compared with global model simulations of aerosol indirect forcing over the entire North Pacific basin. During April 2004 the U. Wyoming King Air research aircraft sampled aerosol and cloud microphysical parameters including aerosol and cloud particle sizes and concentrations, cloud liquid water amounts, and cloud structure using the Wyoming Cloud Radar. A range of clean and polluted conditions were observed by the aircraft during the period, in addition to two major Asian dust storm events. CN concentrations below stratus clouds varied from 25 to 300 cm-3. A variety of cloud systems were sampled as well, ranging from shallow stratus and stratocumulus clouds to mixed-phase precipitating cumulus. Under pristine conditions, many shallow clouds were observed to be drizzling, suggesting that Northern Pacific Ocean cloud systems may be highly susceptible to the influence of aerosols. Clouds in this region are responsible for a large cooling of the ocean surface. The magnitude of shortwave cloud radiative cooling exceeded -80 W m-2 over much of the North Pacific during the experiment. Stratus cloud drop concentrations varied from 25 to 150 cm-3 and are correlated with the concentration of accumulation mode aerosols below cloud base. Mean cloud albedos vary from 0.3 to 0.5 for these same clouds, and MODIS observations of cloud drop effective radius compare well with the in-situ measurements. To facilitate the integrated interpretation of these observations and test modern parameterizations of aerosol-cloud interactions in global models, simulations are performed with the NOAA/GFDL AM2 global atmospheric model under the conditions observed during CIFEX. The variability of observed radiative forcing of North Pacific cloud systems are compared with a simulation using a new parameterization based on a prognostic equation for cloud drop number concentration, and a separate simulation using a common diagnostic parameterization based on an empirical relationship between sulfate concentration and cloud drop number concentration.
DE: 3337 Numerical modeling and data assimilation
DE: 3359 Radiative processes
DE: 1640 Remote sensing
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting