Further Improvement to the Convection Scheme in CCSM
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Further Improvement to the Convection Scheme in CCSMFurther Improvement to the Convection Scheme in CCSM
Xiaoliang Song, Liping Deng, Sunwook Park and Ray Arritt Xiaoliang Song, Liping Deng, Sunwook Park and Ray Arritt (ISU) (ISU) Guang Jun ZhangGuang Jun Zhang ( (Scripps Institution of Oceanography)Scripps Institution of Oceanography)Guido Vettoretti and Richard Peltier (University of Toronto)Guido Vettoretti and Richard Peltier (University of Toronto)
Xiaoqing WuXiaoqing Wu
Department of Geological and Atmospheric SciencesDepartment of Geological and Atmospheric SciencesIowa State UniversityIowa State University
Partly by DOE CCPP and ARM
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1. The tropical biases
2. Improvement to convection and cloud schemes
3. Effects on global climate simulations
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Convection
Radiation
Clouds
1. The tropical biases
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Seasonal variation of precipitation
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Madden-Julian Oscillation (MJO)
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Double ITCZ problem in Coupled Models
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2. Improvement to convection and cloud schemes
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Revised ZM Closure assumption Quasi-equilibrium between convection and large-scale forcing
Zhang (2002, 2003 JGR)
Conv
LSb CAPE
CAPEm
ECAP CAPELS
Conv
LS: Large-scale advection and radiative heating/cooling
Conv: Convective processes
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Non-squall cluster Squall cluster Scattered convection
Wu and Moncrieff (1996)
Cloud-Resolving Model (CRM) simulations
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Activation of deep convection
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In-cloud water concentration derived from the CRM simulation (solid) compares with that used by the standard CCM3 (dashed). Circles are normalized CRM cloud (liquid and ice) water paths.
Wu and Liang (2005, GRL)
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Convective Momentum Transport (CMT)
Zhang and Cho (1991, JAS)Wu and Yanai (1994, JAS)Wu, Zhang and Liang (2003, GRL)
xp
zuMuuF c
ccx
)(
yp
zvMvvF c
ccy
)(
Cloud-scale pressure
Cloud mass fluxDetrainment of mass
In-cloud momentum
Convective momentum tendency:, yx FF:, cc vu
::cM
:cp
Fractional area of clouds:c
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3. Effects on global climate simulations
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Coupled GCM simulations
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SummarSummaryy
• Statistical analysis of CRM simulations together with Statistical analysis of CRM simulations together with the theoretical consideration of subgrid-scale the theoretical consideration of subgrid-scale processes offer a unique opportunity to reduce the processes offer a unique opportunity to reduce the uncertainties, especially tropical biases, in the climate uncertainties, especially tropical biases, in the climate simulations.simulations.
• The seasonal variation and global distribution of The seasonal variation and global distribution of precipitation and the MJO simulation are improved precipitation and the MJO simulation are improved and closer to observations. and closer to observations.
• Preliminary coupled simulations show strong effects Preliminary coupled simulations show strong effects of the modified convection and cloud schemes on the of the modified convection and cloud schemes on the double ITCZ problem. double ITCZ problem.