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Sensitivity to the CAM candidate schemes in climate and forecast runs along the Pacific Cross-section. Cécile Hannay, Dave Williamson, Jerry Olson, Jim Hack, Jeff Kiehl, Richard Neale and Chris Bretherton* National Center for Atmospheric Research, Boulder

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Presentation Transcript
Sensitivity to the CAM candidate schemes in climate and forecast runs along the Pacific Cross-section

Cécile Hannay, Dave Williamson, Jerry Olson, Jim Hack, Jeff Kiehl,

Richard Neale and Chris Bretherton*

National Center for Atmospheric Research, Boulder

*University of Washington, Seattle

AMWG, NCAR, 29-31 January 2007


Outline
Outline

  • The Pacific Cross Section

  • Models: PBL and convective schemes

  • Climate runs

    - Model versus observations along the cross-section

  • Forecast runs

    - Forecast runs settings

    - Forecast errors along the cross-section

    - Sensitivity to the 3 candidate deep convection schemes

    - Sensitivity to the UW shallow convection/PBL schemes

  • Conclusion


The pacific cross section

The Pacific Cross-section

  • EUROCS project

    • JJA 1998

  • GCSS intercomparison

    • JJA 1998/2003

  • Observations

    • ISCCP data

  • SSM/I product

  • TOVS atmosphere

    • GPCP precipitation

    • AIRS data

  • Reanalyses

    • NCEP/ERA40


Models pbl and convective schemes

Both resolution

and dycore

  • Control

  • Neale+Richter

  • Wu

  • Zhang

  • CAM-UW

Finite volume 1.9x2.5

26 vertical levels

Eulerian T42

30 vertical levels

Models: PBL and convective schemes


Observations along the cross section jja 1998

LWP

SWCF

LWCF

CERES

SSM/I

CERES

Low cloud

Precipitation

Mid/high cloud

ISCCP, D1

ISCCP, D1

GPCP

Observations along the cross-section, JJA 1998


Climate runs versus observations jja 1998

LWP

SWCF

LWCF

CERES

SSM/I

CERES

Low cloud

Precipitation

Mid/high cloud

ISCCP, D1

ISCCP, D1

GPCP

--- Obs--- Control--- Neale +Richter--- Zhang--- Wu

Climate runs versus observations, JJA 1998


Climate runs versus observations

LWP

SWCF

LWCF

CERES

SSM/I

CERES

Low cloud

Precipitation

Mid/high cloud

ISCCP, D1

ISCCP, D1

GPCP

--- Obs--- Control--- CAM-UW

Climate runs versus observations


Forecast run specification

CAM

Forecast run specification

Initialize realistically

ERA40 reanalysis

  • Strategy

    If the model is initialized realistically,

    we assume the error comes from the parameterizations deficiencies.

  • Advantages

    Full feedback SCM

    Deterministic  statistical

    Look at process level

  • Limitations

    Accuracy of the atmospheric state ?

5-day forecast

Starting daily at 00 UT

Observations ERA40


Forecast errors and climate errors control era40

Forecast T error (K), day 1

Forecast T error (K), day 5

Climate T error (K), JJA1998

Forecast q error (g/kg), day 1

Forecast q error (g/kg), day 5

Climate q error (g/kg), JJA1998

  • Cloud regimes => range of error structures

  • Climate bias appears very quickly in CAM

  • Climate error ~ Forecast error at day 5

Forecast errors and climate errors: Control-ERA40


Sensitivity to the deep convection schemes

Location on the cross-section

ITCZ

Sensitivity to the deep convection schemes


Forecast temperature errors at day 5 july 1998

Neale+Richter

Control

Wu

Zhang

  • All deep convection candidates

  • Reduces warm T bias near ITCZ

  • Error increases in the lower troposphere and above 300 mb.

  • Changes in regions where the deep convection is not active

Forecast temperature errors at day 5, July 1998


Itcz regime forecast t error july 1998

Neale+Richter

Control

Warm bias

Cold bias

Wu

Zhang

ITCZ region: forecast error is set within 1 day

ITCZ regime, forecast T error, July 1998


Itcz regime temperature equation terms

Total tendency

Advective tendency

Physics tendency

--- Control--- Neale +Richter--- Zhang--- Wu

ITCZ regime, temperature equation terms


Itcz regime physics tendency terms

Total physics

Deep convection

Shallow convection

Prognostic cloud

PBL

Radiation

--- Control--- Neale+Richter--- Zhang--- Wu

ITCZ regime, physics tendency terms


Deep convection tendency along cross section

Neale+Richter

Control

Zhang

Wu

Deep convection tendency along cross-section


Itcz regime precipitation july 1998

  • - GPCP DatasetDaily precipitation

  • Control Loses water very quickly during day 1.

  • Wu and Zhang Strong diurnal cycle.

Omega

--- GPCP--- Control--- Neale+Richter--- Zhang--- Wu

ITCZ regime, Precipitation, July 1998

Total precipitation


Itcz regime omega at day 1 july 1998

--- Obs--- Control--- Neale +Richter--- Zhang--- Wu

ITCZ regime, omega at day 1, July 1998


Skill scores july 1998

V250, RMS error

V850, RMS error

Tropics

Tropics

--- Control--- Neale+Richter--- Zhang--- Wu

Skill scores, July 1998


Skill scores july 19981

Z500, RMS error

SLP, RMS error

North

hemisphere

South

hemisphere

--- Control--- Neale+Richter--- Zhang--- Wu

Skill scores, July 1998


Sensitivity to the uw scheme

Location on the cross-section

Stratocumulus

Sensitivity to the UW scheme


Forecast temperature errors at day 5 jja 1998

Control

CAM-UW

CAM-UW does not change much the error structure.

Forecast temperature errors at day 5, JJA 1998


Stratocumulus moisture and pbl jja 1998

Specific humidity

PBL height

day 0

day 1

day 2

day 5

Control

PBL collapses

Stronger daily cycle

CAM-UW

Stratocumulus, moisture and PBL, JJA 1998


Stratocumulus timeseries of t and q error

TCAM-TERA40

qCAM-qERA40

Stratocumulus: timeseries of T and q error


Stratocumulus q equation single forecast

Advective tendency

Physics tendency

q

Control

CAM-UW

Stratocumulus: q equation (single forecast)


Stratocumulus regime physics terms

PBL tendency

Shallow

tendency

Prognostics cloud

water tendency

Control

CAM-UW

Stratocumulus regime (Physics terms)


Conclusion
Conclusion

  • CAM forecasts allows for diagnosing model errors in the different cloud regimes.

  • Climate bias appears very quickly

    • Where deep convection is active, error is set within 1 day

    • 5-day errors are comparable to the mean climate errors.

  • Sensitivity to candidate parameterizations

    • All deep convection schemes improve the warm bias in upper troposphere, but cold bias increases in lower troposphere and near top of the model. Change the error where the deep convection is not active.

    • CAM-UW: does not change the error structure but CAM-UW operates very differently than Control at the process level.



Climate runs versus observations jja 19981

--- Obs--- Control--- Neale--- Zhang--- Wu

Climate runs versus observations, JJA 1998

LWP

SWCF

LWCF

CERES

SSM/I

CERES

Low cloud

High cloud

Middle cloud

ISCCP, D1

ISCCP, D1

ISCCP, D1




Itcz regime omega july 1998
ITCZ regime, omega, July 1998

Control

Neale+Richter

Zhang

Wu


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