EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
117-10 October, 20027-10 October, 2002
3D-VAR data assimilation experiments 3D-VAR data assimilation experiments for the double-nested limited area model for the double-nested limited area model
ALADIN/HungaryALADIN/Hungary
Steluta Alexandru
Supervisor: Andras Horanyi
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
227-10 October, 20027-10 October, 2002
Introduction
• The aim: to get an idea about the best strategy of the 3D-VAR data assimilation scheme for a double nested-limited area model.
• Variational assimilation consists in minimizing a cost function J(x).
• The adjoint operator is used to compute the gradient of the cost function J(x).
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
337-10 October, 20027-10 October, 2002
What does it mean a double-nested model?What does it mean a double-nested model?
ARPEGE
ALADIN/LACE
ALADIN/Hungary
boundary
conditions
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
447-10 October, 20027-10 October, 2002
What does it mean a double-nested model?What does it mean a double-nested model?
12 km resolution
8 km resolution
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
557-10 October, 20027-10 October, 2002
The experiments performed (I)The experiments performed (I)
Different lateral boundary techniques:
Time-consistency
Space-consistency
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
667-10 October, 20027-10 October, 2002
ResultsResults
• Statistical measures• RMSE
• BIAS
• Diagnostic measures• Time evolution of the fields
• Spectral energy on ellipses
• Subjective evaluation• Maps with increments
• Maps with meteorological fields
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
777-10 October, 20027-10 October, 2002
Verification of the analysisVerification of the analysis
RMSE RMSE ssppaceace
RMSE RMSE timetime
RMSE operRMSE oper
Period
25.02 - 02.03.2002
00 UTC
The fields are closer to the observations using 3D-VAR scheme.
The fields are closer to the observations using 3D-VAR scheme.
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
887-10 October, 20027-10 October, 2002
Verification of 6h forecastVerification of 6h forecast
RMSE RMSE ssppaceace
RMSE RMSE timetime
RMSE operRMSE oper
• The fields with 3D-VAR are keeping the initial improvement, but not for all levels.
• The time-consistency is a better technique for the double-nested limited area model.
• The fields with 3D-VAR are keeping the initial improvement, but not for all levels.
• The time-consistency is a better technique for the double-nested limited area model.
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
997-10 October, 20027-10 October, 2002
The experiments performed (II)The experiments performed (II)
Different initialization methods:
Digital FiIter Initialization
Incremental Digital FiIter Initialization
no initialization
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
10107-10 October, 20027-10 October, 2002
Time evolution of the pressure in cyclingTime evolution of the pressure in cycling
time IDFItime IDFI
time no DFItime no DFI
time DFItime DFI
In 3D-VAR cycling, digital filter initialization has to be applied.
In 3D-VAR cycling, digital filter initialization has to be applied.
02.03.2002
00 UTC
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
11117-10 October, 20027-10 October, 2002
Time evolution of the pressure in productionTime evolution of the pressure in production
time DFI cycling;time DFI cycling;
DFI productionDFI production
time no DFI cycling;time no DFI cycling;
no DFI productionno DFI production
time IDFI cycling;time IDFI cycling;
DFI productionDFI production
In production, digital filter initialization is need.
In production, digital filter initialization is need.
operoper
02.03.2002
00 UTC
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
12127-10 October, 20027-10 October, 2002
The experiments performed (III)The experiments performed (III)
Different lateral boundary conditions files:
ALADIN/LACE
ARPEGE
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
13137-10 October, 20027-10 October, 2002
Verification of the analysisVerification of the analysis
RMSE RMSE LACELACE
RMSE RMSE ARPEGEARPEGE
RMSE operRMSE oper
Period
25.02 - 25.03.2002
00 UTC
• The fields are closer to the observations using 3D-VAR scheme.
• There is no signifficant difference for the analyses with 3D-VAR, when different LBC files were used.
• The fields are closer to the observations using 3D-VAR scheme.
• There is no signifficant difference for the analyses with 3D-VAR, when different LBC files were used.
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
14147-10 October, 20027-10 October, 2002
Verification of 6h forecastVerification of 6h forecast
RMSE RMSE LACELACE
RMSE RMSE ARPEGEARPEGE
RMSE operRMSE oper
• The fields with 3D-VAR are keeping the initial improvement, but not for all levels.
• The choice of the LBC files is not so important.
• The fields with 3D-VAR are keeping the initial improvement, but not for all levels.
• The choice of the LBC files is not so important.
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
15157-10 October, 20027-10 October, 2002
ConclusionsConclusions
• The forecast with 3D-VAR keeps the improvement of the analysis.
• Using time-consistency, a better forecast is obtained.
• In 3D-VAR cycling and in production, digital filter initialization method is need.
• The choice of the lateral boundary conditions files is not so important.
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
16167-10 October, 20027-10 October, 2002
Future plansFuture plans
• Case studies
• More data to be used.
• Tests with lagged statistics.
• Use of the spectral blending procedure.
EWGLAM meetingEWGLAM meeting
3D-VAR data assimilation experiments for the double-nested limited area model3D-VAR data assimilation experiments for the double-nested limited area modelALADIN/HungaryALADIN/Hungary
17177-10 October, 20027-10 October, 2002
THANK YOU FOR YOUR ATTENTION!
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