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The Role of Atmospheric Aerosol Concentration on Deep Convective Precipitation: Cloud-resolving Model SimulationsAerosols and especially their effect on clouds are one of the key components of the climate system and the hydrological cycle [Ramanathan et al., 20011. Yet, the aerosol effect on clouds remains largely unknown and the processes involved not well understood. A recent report published by the National Academy of Science states "The greatest uncertainty about the aerosol climate forcing - indeed, the largest of all the uncertainties about global climate forcing - is probably the indirect effect of aerosols on clouds NRC [2001]." The aerosol effect on clouds is often categorized into the traditional "first indirect (i.e., Twomey)" effect on the cloud droplet sizes for a constant liquid water path and the "semi-direct" effect on cloud coverage. The aerosol effect on precipitation processes, also known as the second type of aerosol indirect effect, is even more complex, especially for mixed-phase convective clouds. ln this paper, a cloud-resolving model (CRM) with detailed spectral-bin microphysics was used to examine the effect of aerosols on three different deep convective cloud systems that developed in different geographic locations: South Florida, Oklahoma and the Central Pacific. In all three cases, rain reaches the ground earlier for the low CCN (clean) case. Rain suppression is also evident in all three cases with high CCN (dirty) case. However, this suppression only occurs during the first hour of the simulations. During the mature stages of the simulations, the effects of increasing aerosol concentration range from rain suppression in the Oklahoma case, to almost no effect in the Florida case, to rain enhancement in the Pacific case. These results show the complexity of aerosol interactions with convection.
Document ID
20070034884
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Tao, W.-K. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Li, X. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Khain, A. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Mastsui, T. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Lang, S. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Simpson, J. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 24, 2013
Publication Date
January 1, 2007
Subject Category
Meteorology And Climatology
Distribution Limits
Public
Copyright
Public Use Permitted.

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