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The Global Wind Oscillation April-May 2007 Edward Berry NOAA/NWS Dodge City, Kansas Klaus Weickmann...
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Transcript of The Global Wind Oscillation April-May 2007 Edward Berry NOAA/NWS Dodge City, Kansas Klaus Weickmann...
The Global Wind Oscillation April-May 2007
Edward Berry NOAA/NWS Dodge City, Kansas
Klaus Weickmann NOAA/ESRL/PSD, Boulder, Colorado
High Plains Conference Hastings, NE
August 16th, 2007
> WB(2007) proposed a Global Synoptic Dynamic Model of subseasonal atmospheric variabilty (GSDM)
> GSDM considers the interaction of 3-4 different time scales including the MJO recurrence time
> Purpose of GSDM is to extend current thinking beyond the MJO
> The Global Wind Oscillation (GWO) objectively represents a non-oscillatory component of the GSDM
Background
Outline of Talk
* Review the GSDM
* Introduce the GWO * Case Study
* Summary
* Risk Assessment Plots
There is no Cookbook!!!
• Subseasonal Forecasting Tools– Numerical Models
• ensembles (multi-model)• ocean coupled
– Statistical Models• composites• regressions
– Statistical-Dynamical• linear inverse models• analogues of forecasts
– Global Synoptic-Dynamic Model (GSDM)
• Weather Climate Linkage– Regime transitions– Extreme events
eddies
convection
mountains
What is the GSDM?
Evolutionary framework for weather- climate diagnosis and forecasting
Core subseasonal time scales - fast, slow and “quasi-o”; also ENSO, etc.
Physical Processes – Tropical Convection (tropical OLR modes)– Momentum Transports (eddy vs. HC/FC)– Torques (Mountain and friction)
New way to evaluate model predictions Used to keep pulse on evolving climate
state: from synoptic storms to decadal shifts
GLOBAL SYNOPTIC DYNAMIC MODEL (GSDM)Each stage shows spatial structure of 3-4 time scales
Wave energy dispersion favors high impact weather across USA Plains
Below normal temperatures possible across central and eastern USA
High Impact weather event possible along USA west coast
Heavy precipitation event possibleSouthwest USA
What is the GWO?
• Quasi-phase space plot of normalized AAM against normalized AAM tendency
• Similar to MJO phase space plots such as WH(2004)• Objectively represents portion of GSDM most closely
linked with AAM variations – Tropical Convection (tropical OLR modes) implicitly– Momentum Transports (eddy vs. HC/FC)– Torques (Mountain and friction)
• Captures behaviors such as poleward propagation of zonal mean wind anomalies
• Provides considerable independent information on variations of the global circulation
Stage 1
Stage 2
Stage 3
Stage 4
Relative AAM Tendency
Relative AAM
4/35/11
4/9 5/164/26
5/26
4/16
5/22
Case Study: Week-2 Forecast for 18-25 May 2007
Western USA Trough when models forecasted a ridge
Severe storms across the Plains
GWO provided additional predictive insight
MAY 11
#1
#2
EE
E
E
E
E
EE
WW
W
W
W
E#1 #2
4/95/16
4/3 5/114/26 5/264/16 5/22
H
HH
H
H
H
L LL
LL LH
L
H
H
LHH LH
L H
LL
H
H
HL H
H
H
H
H
L
May 7
May 11
250mb Daily Mean Vector Wind Anomalies
L
L LL
H
HH
H
H
H
H
H
L HHL
L
L
May 15
May 19
H
H
250mb Daily Mean Vector Wind Anomalies
H
H
H
L
L
HL L L H
L
H
H
HL
May 23
250mb Daily Mean Vector Wind Anomalies
PDF for AMJ GSDM Stage 2 vs. 4 Western USA 850 Ta
Probs ordinate
Std dev abscissa
Stage 2
Stage 4
-4.25 +4.25-1.75
• GSDM provides link between weather and climate
• GWO is objective representing a portion of the GSDM
• Risk assessment maps based on the GSDM are being developed
• Present efforts include HydroMet Testbed for west coast floods and CPC Global Tropical HA
• Subseasonal forecasts (weeks 1-4) must be probabilistic and verified accordingly
Summary and Conclusions
QUESTIONS?
Summary and ConclusionsSummary and Conclusions
GSDM provides link between weather GSDM provides link between weather and climate and climate
GWO is objective representing a portion GWO is objective representing a portion of the GSDMof the GSDM
Risk assessment maps based on the Risk assessment maps based on the GSDM are being developed GSDM are being developed
Present efforts include HydroMet Present efforts include HydroMet Testbed for west coast floods and CPC Testbed for west coast floods and CPC Global Tropical HAGlobal Tropical HA
Subseasonal forecasts (weeks 1-4) must Subseasonal forecasts (weeks 1-4) must be probabilistic and verified accordinglybe probabilistic and verified accordingly
.
11May
11May
.
W
W
E
W
W EW WE
#1 #2
4/3 5/114/9 5/164/26 5/264/16 5/22
#1 #2
4/3 4/9 5/115/164/26 5/264/16 5/22
#1
#2
4/3 4/9 5/115/164/26
5/264/165/22