Balanced Coupling Between Vertical Motion and Diabatic Forcing for Variational Data Assimilation
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Transcript of Balanced Coupling Between Vertical Motion and Diabatic Forcing for Variational Data Assimilation
Balanced Coupling Between Vertical Motion and Diabatic Forcing for Variational Data Assimilation
Luc FillionCollaborators:
Monique Tanguay, Nils Ek, Christian Page, Simon Pellerin, Michel Desgagne
Meteorological Service Canada
Dorval, Québec, Canada
Target Grid for Regional 48H Forecast at 10 km using GEM_LAM
Higher resolution nested grids on demand (ex: 2km)
VancouverMontreal
Development of a Limited Area VDAS(Main Focus: Precipitation)
Unified Global/LA Variational analysis code.
Main features (at the present time: 1st Sept 2005):
1. Extension of Meso3D-Var to 4D-Var (june 2005).
2. Coupling of Divergence and Mass fields using Moist
Diabatic Balance Operators directly in the Variational
Analysis.
hPa wind analysis increments: FGAT Versus 4D-Var
UU-Obs at 500 hPa at 0h
Meso 4DVar wind analysis increments at 500 hPaTime Assimilation window: 6h
)(*
)(**
2202
2202 T
p
Rf
p
f
p
fω
vv
OperatorsNonlinearAATAA TT ,;)()( Ω
TTT ;
OperatorsLinearTangentTT TT AAAAΩ ,;),(),(
Adiabatic Balance (Mike Fisher’s approach at ECMWF)
PHYT dt
dT
p
RTAA 2
*)()(
Ω
),,;,( vuqTKdt
dT
Conv
),()()( 2
*qTK
p
RTAA T
Ω
),(),(),( ,2
*qT
p
RTT qTT
KAAΩ
Diabatic Balance (Kasahara & Krishnamurti’s dream!)
Diabatic Balance Included
24 August 2004; 12 UTC
~ 500 hPa Wind Increments
Total μbs at 500 hPa
bs-1
hPa
850 hPa
Kain-Fritsch Temperature Tendency
esovar_L: 50 km; 58 Levels
RHS Convective Forcing of Equation
hPa Wind Increments due to Convective Forcing
hPa Wind Increments due to Convective Forcing
Summary: Benefits of the coupling
1. Better I.C. for NWP over diabatic regions.2. Spin-up effects should be reduced3. Can improve Precipitation Assimilation 4. Can potentially be extended down to Kilometric XD-Var Data Assimilation; i.e. See Christian Page ‘s talk at 12h45 !
Regionalmodel