1

National Aeronautics and Space Administration

Jet Propulsion LaboratoryCalifornia Institute of TechnologyPasadena, California

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 LaboratoryCalifornia Institute of TechnologyPasadena, California

-1 2 5 8 11 14 17 20 23 26 29 32 35latitude (degrees)

AIRS relative humidity (%)

1000

900

800

700

600

500

400

300

200

100

pre

ssure

(hPa) J

JA

2003

01 02 03 04 05 06 07 08 09 0

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 LaboratoryCalifornia Institute of TechnologyPasadena, California

ECMWF fvMMF GEOS5

LWC

CloudSat liquid water content (LWC) forJJA 2006 along GPCI transect

LWC 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 LaboratoryCalifornia Institute of TechnologyPasadena, California

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 LaboratoryCalifornia Institute of TechnologyPasadena, California

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.html.

• 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