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Warm Rain Processes Over the Tropical Oceans and Implications on Climate ChangeIn this talk, we will first show results from TRMM regarding the characteristics of warm rains over the tropical oceans, and the dependence of rate of warm rain production on sea surface temperature. Results lead to the hypothesis that warm rain production efficiency, i.e., autoconversion, may be increased in a warm climate. We use the GEOS-II GCM to test this hypothesis. Our modeling results show that in a climate with increased rate of autoconversion, the total rain amount is increased, with warm rain contributing to a larger portion of the increase. The abundant rainout of warm precipitation at middle to low levels causes a reduction of high cloud cover due to the depletion of water available for ice-phase rain production. As a result, more isolated, but more intense penetrative convection develops. Results also show that increased autoconversion reduces the convective adjustment time scale tends, implying a faster recycling of atmospheric water. Most interestingly, the increased low level heating associated with warm rain leads to more energetic Madden and Julian oscillations in the tropics, with well-defined eastward propagation. While reducing the autoconversion leads to an abundant mix of westward and eastward tropical disturbance on daily to weekly time scales. The causes of the sensitivity of the dynamical regimes to the microphysics parameterization in the GCM will be discussed.
Document ID
20040171266
Document Type
Preprint (Draft being sent to journal)
Authors
Lau, William K. M. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Wu, H. T. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 22, 2013
Publication Date
January 1, 2004
Subject Category
Meteorology and Climatology
Meeting Information
ICCP 2004(Bologna)
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.