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