CFMIP-2 : Cloud Feedback Model Intercomparison Project Phase 2

Transcription

1 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 : Outline of this presentation : Clouds in climate modeling challenges Main aspects of the CFMIP-2 proposal Questions/requests to WGCM and CMIP

2 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?

3 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 ]

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

5 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).

6 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

7 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)

8 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: ]

9 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.

10 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

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

12 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

13 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?

14 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.

15 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

16 Thank you!

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

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

19 Low Level clouds fraction (Ptop > 680hPa) Sept-Oct-Nov CALIPSO data GCM + CALIPSO simulator ISCCP data GCM + ISCCP simulator

20 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

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