CFMIP-2 : Cloud Feedback Model Intercomparison Project Phase 2

CFMIP-2 : Cloud Feedback Model Intercomparison Project Phase 2 Sandrine Bony on behalf of the CFMIP coordination committee From Victoria to Hamburg WGCM meetings : 2006 WGCM meeting: necessity to develop closer collaborations between CFMIP (focused on cloudclimate interactions) and GEWEX-GCSS (cloud processes and parameterizations). Jan 2007: the GEWEX SSG panel supports plans for GCSS-CFMIP collaboration. Apr 2007: international CFMIP workshop held in Paris to strengthen the links between CFMIP, GCSS, CMIP and US-CPT activities, and lay the foundations for a CFMIP-2 proposal. Jul 2007: CFMIP coordination committee extended: M. Webb, S. Bony, C. Bretherton, G. Tselioudis. Aug 2007: draft of CFMIP-2 proposal available at : http://www.cfmip.net Outline of this presentation : Clouds in climate modeling challenges Main aspects of the CFMIP-2 proposal Questions/requests to WGCM and CMIP

Climate sensitivity estimates from CMIP3 GCMs participating in the IPCC AR4 : Equilibrium Climate Sensitivity : (warming for sustained 2xCO2) Transient Climate Response : (1% CO2/yr, transient warming at 2xCO2) Climate sensitivity estimates depend on : radiative forcing climate feedbacks ocean heat uptake (transient only) How do these different components contribute to inter-model differences in climate sensitivity?

Decomposition of the Transient Climate Response (TCR) simulated by CMIP3/AR4 OAGCMs : Cloud Feedbacks! multi-model mean inter-model differences (standard deviation) [ Dufresne and Bony, 2007 ]

Where does the spread of cloud feedbacks come from? deep convective activity baroclinic activity & frontal clouds boundary-layer turbulence and clouds

Clouds vs Climate Modeling Challenges Cloud feedbacks remain the primary source of spread of Climate Sensitivity and TCR estimates amongst current OAGCMs (especially low-level cloud feedbacks). A concern for the assessment of climate extremes and impacts, for carbon-cycle feedbacks, etc... The development of ESMs will consume a lot of ressources... Still a need to improve the simulation of clouds (incl. their interaction w/ conv. and rad.) and the assessment of cloud feedbacks in coupled models! A major issue for climate sensitivity... and also for systematic errors in GCMs (e.g. tropical SST, precipitation patterns, diurnal cycle, tropical waves).

Clouds vs Climate Modeling Challenges How to make progress? Cloud Processes and Feedbacks Observational Constraints Model Parameterizations Thanks to : new A-Train observations (e.g. CloudSat, CALIPSO) CFMIP-GCSS collaborations available analysis methods progress is possible (and expected!) over the next few years... CALIPSO CloudSat

CALIPSO lidar measurements : Towards a near-global view of the 3D structure of clouds from space low-level cloud fraction derived from CALIPSO (Chepfer et al. 2007, submitted)

Cloud Feedback Model Intercomparison Project Phase 2 (CFMIP-2) GCM process diagnostics CRMs/LES/SCMs via GCSS A-Train/ISCCP & simulators Understanding of cloud feedbacks Evaluation of cloud fields Assessment of climate change cloud feedbacks [Full proposal available at: http://www.cfmip.net ]

GCM process diagnostics CRMs/LES/SCMs via GCSS A-Train/ISCCP & simulators Understanding of cloud feedbacks Evaluation of cloud fields CFMIP activities for an improved evaluation of modelled clouds using observations : Assessment of climate change cloud feedbacks Current developments : development of a CloudSat radar simulator (CSU, PNNL/UW, LLNL) development of a CALIPSO lidar simulator (LMD/IPSL) improved version of the ISCCP simulator (Hadley Centre) assemblage of these different modules into a combined CFMIP-ISCCP-CloudSat-CALIPSO Simulator named CICCS Plans : release of a beta version of CICCS : end-2007, pilot model intercomparison studies using this simulator : early 2008 production version for use in CMIP4/CFMIP2 and in CAPT: mid-2008.

GCM process diagnostics CRMs/LES/SCMs via GCSS A-Train/ISCCP & simulators Understanding of cloud feedbacks Evaluation of cloud fields CFMIP-GCSS activities for a better understanding & evaluation some key cloud-climate processes : Assessment of climate change cloud feedbacks Plans (to be finalized at the PAN-GCSS workshop on June 2008): process studies based on the analysis of grid-point high-frequency model outputs along transects (e.g. WGNE-GPCI, VOCALS) and over ARM sites CFMIP-GCSS CRM/LES/SCM case studies focused on the sensitivity of low-level clouds to changes in climate development of a cloud-climate metrics

CFMIP2-GCSS Idealized Sensitivity Experiment to be performed by LES/CRM/SCM models Zhang and Bretherton (in preparation)

GCM process diagnostics CRMs/LES/SCMs via GCSS A-Train/ISCCP & simulators Understanding of cloud feedbacks Evaluation of cloud fields CFMIP experiments for a better understanding of inter-model differences in cloud feedbacks : Assessment of climate change cloud feedbacks Lightweight experiments (short, uncoupled), to be run with CICCS and extended outputs, proposed to the modeling groups that wish to participate in CFMIP-2 : AMIP-like experiments forced by specified CO2 concentrations and specified SST & sea-ice patterns (2xCO2 with fixed SSTs, patterned SST forced experiments using a composite of coupled model SST responses from 1%/yr). process studies based on the analysis of grid-point high-frequency model outputs in regions where model cloud feedbacks differ the most. NB: these experiments may be run also by high-resolution global CRM and MMF models

CFMIP questions / requests to WGCM : [ Questions : ] - Does WGCM continue to endorse CFMIP-2 plans? - What plans for 1%/yr and slab experiments in CMIP4? [ Simulators : ] May WGCM request the use of a simulator (the ISCCP simulator or CICCS, the combined ISCCP-CloudSat-CALIPSO simulator) in some CMIP4 experiments? (e.g. in AMIP, 20C3M, 1%/yr CO2 plus control) [ Outputs : ] May the CMIP4 standard output include : - a larger number and frequency of cloud diagnostics - some high frequency model output at selected points (e.g. GPCI, ARM sites) - 3D model outputs stored on model levels [ Storage : ] May the CFMIP-2 experiments and diagnostics be hosted together with the CMIP4 archive?

We hope that many modeling groups will wish to participate in CFMIP-2, and that most of the GCMs participating in CMIP4 will use the CFMIP simulator.

We hope that many modeling groups will wish to participate in CFMIP-2, and that most of the GCMs participating in CMIP4 will use the CFMIP simulator. Cost : - implementation simulator - preparation outputs -storage Scientific benefits : - thorough model evaluation - assessment cloud-climate feedbacks - reduction systematic errors

Thank you!

Decomposition of the effective climate sensitivity simulated by CMIP3/AR4 OAGCMs : multi-model mean inter-model differences (standard deviation)

Low Level cloud fraction (Ptop > 680hPa) Sept-Oct-Nov GCM + CALIPSO simulator GCM GCM + ISCCP simulator 0 0.2 0.4 0.6 0.8 (Chepfer et al. 2007, submitted) 0 0.2 0.4 0.6 0.8

Low Level clouds fraction (Ptop > 680hPa) Sept-Oct-Nov CALIPSO data GCM + CALIPSO simulator ISCCP data GCM + ISCCP simulator 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8

GCM / CloudSat comparison of radar reflectivities Mid-latitude system in the North Atlantic (UK Met Office global forecast model, Jul 7th 2006) Alejandro Bodas-Salcedo

Sensitivity of the Tropical Cloud Radiative Forcing to Global Warming CRF SW SST High-sensitivity OAGCMs Low-sensitivity OAGCMs (Bony and Dufresne, GRL, 2005)