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Alternative Representations of Convective Processes in the NASA GEOS-5 AGCMThe gap in explicit resolution of phenomena between global climate models and cloud resolving models is shrinking at a steady pace with global integrations of several km in resolution now practical for at least some time scales. In moving toward finer resolution the long standing problem of convective parameterization is being examined along with the assumption of convective quasi-equilibrium and how this can be reconciled with the stochastic and intermittent nature of convection. In this context we examine the nature of parameterized convection in the NASA Goddard Earth Observing System (GEOS-5) Atmospheric General Circulation Model. Our analysis uses both coarse (2.5 degree) and fine scale 0.25 degree spatial resolution integrations. Two basic formulations are compared: the default option is the Relaxed Arakawa-Schubert (RAS) scheme which invokes a sequence of linearly entraining plumes and quasi-equilibrium closure. An optional modification of this method (the "Stochastic Tokioka" constraint) places a random lower limit on plume entrainment. An alternative representation is the Kain-Fritsch parameterization which was originally developed for mesoscale numerical modeling strategies. Here entrainment is determined by a crude buoyancy sorting approach that allows the plume spectrum to be more responsive to ambient vertical stratification of moisture. Diagnostics of the model behavior are referenced to recent observational evidence of continuous phase transition behavior. In particular we examine the relationship between column water vapor and probablility of convective presence and intensity. Sensitivity of the statistics of convective behavior to parcel mixing/entrainment formulations and parcel initial thermodynamics are considered. Observational statistics from A-Train and TRMM sensors provide validation of the model integrations.
Document ID
20100003331
Acquisition Source
Marshall Space Flight Center
Document Type
Conference Paper
Authors
Robertson, Franklin
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Cohen, Charles
(Universities Space Research Association Huntsville, AL, United States)
Miller, Timothy
(NASA Marshall Space Flight Center Huntsville, AL, United States)
Date Acquired
August 25, 2013
Publication Date
December 14, 2009
Subject Category
Meteorology And Climatology
Report/Patent Number
M10-0110
Meeting Information
Meeting: 2009 American Geophysical Union (AGU) 2009 Fall Meeting
Location: San Francisco, CA
Country: United States
Start Date: December 14, 2009
End Date: December 18, 2009
Distribution Limits
Public
Copyright
Other

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