Using GERB and CERES data to evaluate NWP and Climate models

over the Africa/Atlantic region

Richard Allan, Tony Slingo, Ali Bharmal

Environmental Systems Science Centre, University of Reading

Sean Milton, Malcolm Brooks, Mark Ringer

Met Office, Exeter

Outline

• Use of GERB/CERES in model evaluation– Evaluation of cloud in NWP model– OLR anomaly over the W Sahara– Current activities at the Hadley Centre

• Combining surface ARM data and top of atmosphere radiation data to evaluate models

Time series (Global, 1200, Model-GERB)60S-60N clear ocean

ΔA

lbed

ocΔ

OLR

c

2003 2004 2005 2006 2007 2008

Time series (Global, 1200, Model-GERB)Δ

Alb

edoc

ΔO

LRc

Major model updatesMS7

Edition 1

SEV2;V004/5

60S-60N clear ocean

2003 2004 2005 2006 2007 2008

All-sky Clear-sky

Sh

ort

wav

eL

on

gw

ave

Biases 2006

Allan et al. (2007) QJRMS

All-sky Clear-sky

Sh

ort

wav

eL

on

gw

ave

Convective cloud

Surface albedo

Mineral dust aerosol

Marine stratocumulus

Cirrus outflow

Biases 2006

Allan et al. (2007) QJRMS

Model evaluation: near-real time

• Change in model minus GERB flux differences

• Relate to change in model physics implementation

13th March | 14th March 2006

Model SW albedo

2005 2006

• Modified convective parametrization

Increased convective cloud cover

Tropical land: model-GERB albedo difference

• Comparisons with GERB and CloudSat show improved simulation of tropical convective cloud

Allan et al. (2007) QJRMS

Time series (Global, 1200, Model-GERB)60S-60N land

ΔA

lbed

oΔ

OLR

Major model updatesMS7

Edition 1

SEV2;V004/5

Changes in boundary layer and convection schemeConvective decay time-scale parametrization

Diurnal cycle of convection

6.3um BT < 225 K

- Diagnosing convective cloud fraction: (OLRc-OLR)/cloud fraction

- Comparable to narrowband method from SEVIRI

- Model delay in convective cloud? Peak in SEVIRI total cloud at midday – spurious?

Gulf of Guinea

Model CloudSat

19th July 2006

5th July 2006

Allan et al. (2007) QJRMS

Namibian Stratocumulus

Namibian Stratocumulus

Cloud liquid water path

Bias: model minus GERB; SSM/I; SEVIRI

Albedo Liquid Water Path Cloud

Reduction in model bias from June to July 2006 - relates to cloud liquid water?

Allan et al. (2007) QJRMS

2004JJAJJA 12:00

2005JJAJJA 12:00

2006JJAJJA 12:00

2007JJAJJA 12:00

2008JJA 12:00

Time series (Global, 1200, Model-GERB)60S-60N clear land

ΔA

lbed

ocΔ

OLR

c

Major model updatesMS7

Edition 1

SEV2;V004/5

Increased Sahara albedo Improved Sahara albedo 2003 2004 2005 2006 2007 2008

Multi-model ensemble mean minus CERES EBAF 2000

LW difference SW difference

• Compare AMIP climate model ensemble– CCSM3, INMCM3, MIROC high/low, CGCM2.3, CNRM_CM3, HadGEM1

• Biases due to cloud and surface albedo• Also models overestimate OLR over W. Sahara

OLR bias

• OLR bias present for clear-sky also

• Smaller for EBAF (MODIS enhanced)

OLR bias

• OLR bias present for clear-sky also

• Smaller for EBAF (MODIS enhanced)

• Bias present for ERBE-like processing

Use of CERES/GERB at the Met Office/Hadley Centre (Mark Ringer)

• HadGEM1 was model used for IPCC AR4• HadGEM2 will be submitted to AR5

– Basic physics as HadGEM1 but will include many ‘Earth System’ processes such as C-cycle, chemistry, etc

• HadGEM3 is currently being developed– Focus on regional climate and decadal prediction– Includes completely new prognostic cloud scheme

• CERES data fully integrated into model development and evaluation– Evolving model versions and tests of parameterizations are

systematically evaluated using CERES products• GERB: Monthly mean and monthly mean diurnal cycle

would be of most use initially• Also note that these data are an important part of our work

on feedbacks and attempts to constrain climate sensitivity

EXPERIMENTEXPERIMENT

minus

CONTROL

CONTROL

minus

CERES

EXPERIMENT

minus

CERES

Development of HadGEM3:Use of CERES SW cloud forcing, impact of removing new cloud scheme.

Comparison of GERB with HadGEM1:Model forced with climatological SSTs

GERB

HadGEM1

OLR RSW

Liquid Water Content

TOA LW up

TOA SW up

Ice Water Content

retrieval

0 3 6 9 12 15 18 21 24 Time [Hours]

GERB

Lindenberg

Simulating radiative fluxes using ground-based retrievals Nicky Chalmers, Robin Hogan

LindenbergClearCloudyHigh cloud

SU

RF

AC

E

TO

A

CERES clear

-40°C

0°C

-40°C

0°C

Using methodology to evaluate NWP clouds

ClearCloudy

Cloud at all levels

ECMWF: surface LW comparison

Angular conversion factor for the Niamey GERB ARG pixel shows thataerosol alone cannot explain the discrepancy between ES96 & GERB.

Comparison of radiance and flux: Edwards/Slingo vs GERB

N. Ali Bharmal (ESSC)

Ali Bharmal in collaboration with Helen Brindley

Preliminary results comparing SBDART and ES96 RT radiances at TOAusing aerosol-free profiles suggests a disagreement in relation to thesurface/skin temperature difference.

Skin T > sfc T

Time of agreement

Conclusions• Continued near-real time comparisons between

GERB-1/SEV2 and Met Office forecast model• Large model biases have been reduced

– Surface albedo (MODIS bare soil and seasonal vegetation)– Convective cloud (convective decay time-scale)– Seasonal dust climatology likely

• Remaining problems– Marine stratocumulus too reflective

• Appears to relates to bulk water properties– Detrainment of cirrus cloud over Gulf of Guinea– Continued monitoring using GERB data

• www.nerc-essc.ac.uk/~rpa/GERB• Paper detailing previous Edition 1 comparisons published in QJRMS• www.nerc-essc.ac.uk/~rpa/PAPERS/allan_et_al07QJ.pdf• Initial comparisons between GERB/CERES and climate models• Combining surface and top of atmosphere radiation data to evaluate

models