HR: 09:45h
AN: A51C-06    [Abstracts]
TI: A Modeling study of the Ultragiant CCN Effect on Precipitation
AU: * Cheng, C
EM: ctcheng@climate.cestm.albany.edu
AF: Atmospheric Sciences Research Center, State University of New York at Albany, 251 Fuller Rd., CESTM, Albany, NY 12203 United States
AU: Wang, W
EM: wang@climate.cestm.albany.edu
AF: Atmospheric Sciences Research Center, State University of New York at Albany, 251 Fuller Rd., CESTM, Albany, NY 12203 United States
AU: Chen, J
EM: jpchen@webmail.as.ntu.edu.tw
AF: Department of Atmospheric Sciences, National Taiwan University, No. 1, Roosevelt Road, Section 4, Taipei, TWN 10673 Taiwan
AB: In a recent study, Cheng et al. (2005) used the two-moment warm cloud parameterization of Chen and Liu (2004) to study the impacts of aerosol concentration on cloud radiative properties and precipitation. It is found that more aerosols increase the cloud condensate nucleus (CCNs), leading to an increase in cloud albedo and a decrease in precipitation. However, the study does not consider adequately the effects of giant (radius >5 mm) and ultragiant CCNs (radius >10 mm), which has been suggested to enhance precipitation because these giant CCNs can form larger condensate drops, producing rains more efficiently, especially in an environment with high aerosol concentration (Feingold et al., 1999). Here we conduct model simulations to study the effects of ultragiant CCNs by altering aerosol size spectrum to increase the amount of larger size CCNs which are directly activated as raindrops to collect and remove cloud drops when their radiuses are larger than 10 mm. Similar to Cheng et al. (2005), the model simulations were conducted for the case when a front passed through the northern Taiwan during May 16-17, 2003, triggering deep convection and precipitation. Reference Chen, J.-P., and S.-T. Liu, 2004: Physically based two-moment bulk water parameterization for Warm Cloud Microphysics. Quart. J. Roy. Meteor. Soc., 130, 51V78. Cheng, C.-T., W.-C. Wang, and J.-P. Chen, 2005: A Modeling Study of Aerosol Impacts on Cloud Radiative Properties and Precipitation. (submitted to Geophys. Res. Lett. February 2005) Feingold, G., W. R. Cotton, S. M. Kreidenweis, and J. T. Davis, 1999: The impact of giant cloud condensation nuclei on drizzle formation in stratocumulus: Implication for cloud radiative properties. J. Atmos. Sci., 56, 4100-4117.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly