representation of subgrid cloud-radiation interaction and its impact on global climate simulations...
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Representation of Subgrid Cloud-Radiation Interaction and Representation of Subgrid Cloud-Radiation Interaction and its Impact on Global Climate Simulationsits Impact on Global Climate Simulations
Xinzhong Liang (Xinzhong Liang (Illinois State Water Survey, UIUC Illinois State Water Survey, UIUC ))Sunwook Park and Liping Deng (ISU)Sunwook Park and Liping Deng (ISU)
Xiaoqing WuXiaoqing Wu
Department of Geological and Atmospheric SciencesDepartment of Geological and Atmospheric Sciences
Iowa State UniversityIowa State University
Partly by DOE CCPP and ARM
1. The problem
2. Parameterization of subgrid cloud-radiation interaction by mosaic approach
3. Impacts on global climate simulations
CCSM31. The problem
Radiation Parameterization Scheme in General Circulation Model (GCM)
• Radiative transfer equations for shortwave and longwave fluxes and heating rates
• Representation of cloud optical properties such as cloud emissivity and optical depth using cloud liquid and ice water paths
• Treatment of cloud horizontal inhomogeneity and vertical overlap
Cloud Geometry and Inhomogeneity
General Circulation Model
2. Parameterization of subgrid cloud-radiation interaction by mosaic approach and evaluation against CRM simulations
Liang and Wang (1997, JGR)Wu and Moncrieff (2001, JAS)Liang and Wu (2005, GRL)
C
1-CGCMMOS
Mosaic approach (MOS) of treatingsubgrid cloud variability (Liang and Wang 1997, JGR)
Convection
Radiation
CloudsCRM
Cloud liquid/ice water mixing ratio (g/kg)
CRM approachGCM approach
Wu and Moncrieff (2001, JAS)
Quantifying cloud variability effects
Shortwave Flux
TOA
Surface
CRM
GC
MCRM
MO
SCRM
GC
M
CRMM
OS
Liang and Wu (2005, GRL)
Longwave Flux
TOA
CRM
GC
MCRM
MO
SCRM
GC
M
CRMM
OS
Surface
Liang and Wu (2005, GRL)
SW LW Total
Domain average shortwave (SW), longwave (LW) and total heating rate (K/day) profiles as simulated by the CRM and calculated by the GCM and mosaic (MOS) approaches.
Liang and Wu (2005, GRL)
Radiative Heating Rate
3. Impacts on global climate simulations
Wu and Liang (2005, GRL)
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)
High-level Cloud (%) Total Cloud Liquid Water Path (g/m2)
GCM
MOS
ISCCP
GCM
MOS
SSM/I
Wu and Liang (2005, GRL)
210
215
220
225
230
235
240
LW (TOA)
OBS
GCM
MOS
210
215
220
225
230
235
240
SW (TOA)
10
20
30
40
50
60
70
LW (SRF)
OBS
GCM
MOS
145
150
155
160
165
170
175
SW (SRF)
5-year (79-83) global averages of radiative fluxes (W/m2) from observations (OBS), CCM3 (GCM) and mosaic run (MOS)
TOA
SRF
Temperature (K)
GCM GCM-NCEP MOS-GCM
Wu and Liang (2005, GRL)
SummarSummaryy
• The inclusion of subgrid cloud-radiation interaction The inclusion of subgrid cloud-radiation interaction through mosaic approach in the radiation scheme of through mosaic approach in the radiation scheme of GCM enables the use of more realistic cloud amounts GCM enables the use of more realistic cloud amounts and cloud water contents while producing net and cloud water contents while producing net radiative fluxes closer to observations. radiative fluxes closer to observations.
• Consequently, not only the representation of cloud-Consequently, not only the representation of cloud-radiation interactions is more physically consistent radiation interactions is more physically consistent and accurate, but also climate simulations are affected and accurate, but also climate simulations are affected and improved.and improved.
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)
Flux(Wm-2)
OBS MOS/oc CTL/mc
FLW(TOA) 233.9 245.6 225.7
FLW(SRF) 49.4 71.2 52.2
FSW(TOA) 234.0 251.2 213.1
FSW(SRF) 165.9 186.8 145.8