1. National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California 1 GCSS Pacific Cross-section Intercomparison (GPCI): status and progress Models and observations are analyzed along a transect from stratocumulus, across shallow cumulus, to deep convection ISCCP Low Cloud Cover (%) Courtesy C. Hannay GPCI is a working group of the GEWEX Cloud Systems Study (GCSS) Participation of 23 climate/weather prediction models

2. National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California 2 Satellite observations of cloud regime transitions along GPCI transect CloudSat cloud occurrence Model ensemble mean tracks MISR observations of cloud-top height... HOWEVER there is large variability among models Cloud top height

3. National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California 3 ECMWF fvMMF GEOS5 LWC CloudSat liquid water content (LWC) for JJA 2006 along GPCI transect LWC CloudSat LWC from models and CloudSat are similar in magnitude BUT very different in structure: PBL growth is not as clear in CloudSat; Large differences over ITCZ LWC (mg.m -3 ) Li et al., 2009

4. National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California 4 Boundary layer height from GPS RO observations ISCCP Low Cloud Cover (%) Boundary layer height (2001-2004) GPS RO ECMWF GPCI is being used for preliminary studies of future GPS RO missions Von Engeln et al, GRL, 2005

5. National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Pasadena, California 5 GPCI practical developments General GPCI paper is now circulating among co-authors Model results are assembled and organized at the DIME website at: http://gcss- dime.giss.nasa.gov/gpci/modsim_gpci.ht ml. LES experiments forced by ECMWF re- analysis are currently being carried out GPCI framework is being used for: (i) model intercomparison and evaluation (ii) Evaluation of satellite observations (iii) Preliminary studies of future missions Future of GPCI and connections to other initiatives (e.g. CFMIP, EUCLIPSE, YOTC) will be discussed later