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

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

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  1. 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

  2. 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

  3. Pacific Cross-section: several cloud regimes • stratocumulus, shallow cumulus, deep convection… 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

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. Location on the cross-section ITCZ Sensitivity to the deep convection schemes

  11. 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

  12. 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

  13. Total tendency Advective tendency Physics tendency --- Control--- Neale +Richter--- Zhang--- Wu ITCZ regime, temperature equation terms

  14. Total physics Deep convection Shallow convection Prognostic cloud PBL Radiation --- Control--- Neale+Richter--- Zhang--- Wu ITCZ regime, physics tendency terms

  15. Neale+Richter Control Zhang Wu Deep convection tendency along cross-section

  16. - 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

  17. --- Obs--- Control--- Neale +Richter--- Zhang--- Wu ITCZ regime, omega at day 1, July 1998

  18. V250, RMS error V850, RMS error Tropics Tropics --- Control--- Neale+Richter--- Zhang--- Wu Skill scores, July 1998

  19. Z500, RMS error SLP, RMS error North hemisphere South hemisphere --- Control--- Neale+Richter--- Zhang--- Wu Skill scores, July 1998

  20. Location on the cross-section Stratocumulus Sensitivity to the UW scheme

  21. Control CAM-UW CAM-UW does not change much the error structure. Forecast temperature errors at day 5, JJA 1998

  22. 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

  23. TCAM-TERA40 qCAM-qERA40 Stratocumulus: timeseries of T and q error

  24. Advective tendency Physics tendency q Control CAM-UW Stratocumulus: q equation (single forecast)

  25. PBL tendency Shallow tendency Prognostics cloud water tendency Control CAM-UW Stratocumulus regime (Physics terms)

  26. 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.

  27. Extra slides

  28. --- 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

  29. Climate errors: eulerian versus finite volume FV T42

  30. ITCZ regime: Cloud fraction

  31. ITCZ regime, omega, July 1998 Control Neale+Richter Zhang Wu

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