CURRICULUM VITAE Kent A. Kiehl, Ph.D. Associate Professor ...
Cécile Hannay, Dave Williamson, Jerry Olson, Jim Hack, Jeff Kiehl,
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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 *University of Washington, Seattle AMWG, NCAR, 29-31 January 2007
description
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 - PowerPoint PPT Presentation
Transcript of 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*University of Washington, Seattle
AMWG, NCAR, 29-31 January 2007
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
- EUROCS project JJA 1998
- GCSS intercomparisonJJA 1998/2003
- ObservationsISCCP data
SSM/I product TOVS atmosphere
GPCP precipitationAIRS data
- ReanalysesNCEP/ERA40
- Pacific Cross-section: several cloud regimesstratocumulus, shallow cumulus, deep convection…
Models: PBL and convective schemes
Finite volume 1.9x2.5 26 vertical levels
Eulerian T4230 vertical levels
Both resolution and dycore• Control
• Neale+Richter
• Wu
• Zhang
• CAM-UW
Observations along the cross-section, JJA 1998
SWCF LWCF LWP
Low cloud Mid/high cloud Precipitation
CERES
CERES SSM/I
ISCCP, D1 GPCPISCCP, D1
Climate runs versus observations, JJA 1998
SWCF LWCF LWP
Low cloud Mid/high cloud Precipitation
CERES
CERES SSM/I
ISCCP, D1
GPCP
ISCCP, D1
--- Obs--- Control --- Neale +Richter --- Zhang--- Wu
Climate runs versus observations
SWCF LWCF LWP
Low cloud Mid/high cloud Precipitation
CERES
CERES SSM/I
ISCCP, D1
GPCP
ISCCP, D1
--- Obs--- Control --- CAM-UW
Forecast run specification
• Strategy If the model is initialized realistically, we assume the error comes from the parameterizations deficiencies.
• Advantages Full feedback SCMDeterministic statistical Look at process level
• LimitationsAccuracy of the atmospheric state ?
Initialize realistically ERA40 reanalysis
CAM
5-day forecastStarting daily at 00 UT
Observations ERA40
Forecast errors and climate errors: Control-ERA40
• Cloud regimes => range of error structures• Climate bias appears very quickly in CAM• Climate error ~ Forecast error at day 5
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
ITCZ
Location on the cross-section
Sensitivity to the deep convection schemes
Forecast temperature errors at day 5, July 1998
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
Control
Wu
Neale+Richter
Zhang
ITCZ regime, forecast T error, July 1998
ITCZ region: forecast error is set within 1 day
Control
Warm bias
Neale+Richter
Zhang Wu
Cold bias
ITCZ regime, temperature equation terms--- Control --- Neale +Richter --- Zhang--- Wu
Total tendency Advective tendency Physics tendency
€
∂T∂t
= −V • ∇T −ω(∂T
∂p−RT
pc p)+Qphysics
ITCZ regime, physics tendency terms--- Control --- Neale+Richter --- Zhang--- Wu
Total physics Deep convection
PBL Radiation Prognostic cloud
Shallow convection
Deep convection tendency along cross-section
ControlNeale+Richter
Zhang Wu
ITCZ regime, Precipitation, July 1998--- GPCP--- Control --- Neale+Richter --- Zhang--- Wu
- GPCP DatasetDaily precipitation
- Control Loses water very quickly during day 1.
- Wu and Zhang Strong diurnal cycle.
Total precipitation
Omega
ITCZ regime, omega at day 1, July 1998
--- Obs--- Control --- Neale +Richter --- Zhang--- Wu
Skill scores, July 1998 --- Control --- Neale+Richter --- Zhang--- Wu
V250, RMS error V850, RMS error
Tropics Tropics
Skill scores, July 1998 --- Control --- Neale+Richter --- Zhang--- Wu
North hemisphere
Southhemisphere
SLP, RMS errorZ500, RMS error
Stratocumulus
Location on the cross-section
Sensitivity to the UW scheme
Forecast temperature errors at day 5, JJA 1998
CAM-UW does not change much the error structure.
Control CAM-UW
Stratocumulus, moisture and PBL, JJA 1998
PBL heightSpecific humidity
Control
CAM-UW
Stronger daily cyclePBL collapses
day 0day 1 day 2day 5
Stratocumulus: timeseries of T and q error
TCAM-TERA40
qCAM-qERA40
Stratocumulus: q equation (single forecast)
Control
CAM-UW
q Advective tendency
Physics tendency
Stratocumulus regime (Physics terms)
Control
CAM-UW
PBL tendency
Shallow tendency
Prognostics cloud water tendency
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.
