COSMO Priority Project ’Tackle deficiencies in quantitative precipitation forecasts’
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Transcript of COSMO Priority Project ’Tackle deficiencies in quantitative precipitation forecasts’
Federal Department of Home Affairs FDHAFederal Office of Meteorology and Climatology MeteoSwiss
COSMO Priority Project ’Tackle deficiencies in quantitative
precipitation forecasts’
29th EWGLAM Meeting, 9 October 2007, Dubrovnic
S. Dierer1, M. Arpagaus1, U. Damrath2, A. Seifert2, J. Achimowicz8, E. Avgoustoglou7, M. Baldauf2, R. Dumitrache9, V. Fragkouli7, F. Grazzini3, P. Louka7, P. Mercogliano6, P. Mezzasalma3, M. Milelli4, D. Mironov2, A. Morgillo3, E. Oberto4, A. Parodi5, I.V. Pescaru9, U. Pflüger2, A. Sanna4, F. Schubiger1, K. Starosta8, M. S. Tesini3
1MeteoSwiss (CH), 2DWD (D), 3ARPA-ER (IT), 4ARPA-P (IT), 5Uni Genova
(IT), 6CIRA-CMCC (IT), 7HNMS (GR), 8IMGW (PO), 9NMA (RO)
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Aim of PP QPF
The aim of PP QPF is improved knowledge about • most suitable namelist settings or • parts of the model that need to be reformulated
to obtain a better QPF at 7 km horizontal grid size
Good quantitative precipitation forecast is a challenging task – also for the COSMO model:
The project has a focus on model deficiencies – not on errors from e.g. initial and large scale conditions
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Overview of PP QPF
• Task 1: Selection of test cases representative for „typical“ QPF deficiencies of COSMO model
• Task 2: Definition of sensitivity studies
• Task 3: Run sensitivity studies and draw conclusions
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List of test cases from all countries
DATE INSITUTION Overestimation (+)/underestimation (-)
Stratiform (strat)/convective(con)
06.12.2004 DWD + strat warm sector
18.03.2005 DWD + strat cold front+orography
03.05.2005 DWD + Strat+conv warm front
21.06.2005 DWD - conv cold front
02.02.2005 MeteoSwiss + strat occluded front+orogr.
22.03.2005 MeteoSwiss + strat warm front
12.07.2005 MeteoSwiss + conv -
17.12.2005 MeteoSwiss + strat orography
24.09.2004 ARPA-P - conv cold front+orography
10.04.2005 ARPA-ER + strat occluded front+orogr.
17.08.2006 CIRA-CMCC - conv cold front+orography
09.09.2005 CIRA-CMCC - conv -
01.12.2005 NMA - strat cold front
03.12.2005 NMA - strat cold front+orography
17.12.2005 NMA - Strat+conv cold front
15.09.2005 HNMS - conv -
23.11.2005 HNMS - Strat+conv warm front
26.11.2005 HNMS - strat orography
03.05.2005 IMGW - strat cold front
04.05.2005 IMGW 0 strat cold front
09.06.2005 IMGW + strat -
09.08.2005 IMGW + strat -
23.06.2005 NMA + strat+conv cold front
02.07.2005 NMA + strat cold front
12.07.2005 NMA - strat cold front
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Forecast errors
• 10 cases of stratiform overestimation (8 from D, CH and PO)• 4 cases of stratiform underestimation• 3 cases of convective overestimation• 7 cases of convective underestimation (6 from I and GR)
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Sensitivity studies
• 1. Changes of initial conditions• 2. Changes of numerical methods• 3.1 Changes of microphysics• 3.2 Changes of convection schemes• 3.3 Changes of PBL schemes
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Sensitivity studies: initial conditions
• Soil moisture increased/decreased by 20%• Initial humidity increased/decreased by 10%
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Sensitivity studies: numerical methods
• Halved time step• Leapfrog, tri-cubic semi-Lagrange advection of QR
and QS• Runge-Kutta, tri-cubic semi-Lagrange advection of
QV, QC, QI, QR and QS • Runge-Kutta, flux-form advection of QV, QC, QI, QR
and QS • Runge-Kutta, flux form advection and T’-p’ dynamics • increased orography filtering
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Sensitivity studies: physics 1 - microphysics
• New warm rain scheme (Seifert and Beheng; 2001)• Strong changes of ice microphysics and new warm
rain scheme • Moderate changes of ice microphysics and new warm
rain scheme
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Sensitivity studies: physics 2 –convection
• Modified Tiedtke scheme • Kain-Fritsch/Bechtold scheme • No parameterization of deep convection
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Sensitivity studies: physics 3 – PBL
• Decreased/increased scaling factor of height of laminar boundary layer for heat
• Decreased/increased stomatal resistance• Decreased/increased laminar scaling factor for heat
over sea
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Relative change of 24h area average precipitation, first forecast day (06 – 30)
Initial humidityRunge-Kutta Snow microphysicsConvection scheme
Vertical heat/moisture exchange
German{
Swiss{
Ital. (LAMI){Ital.(EuroLM){
Greek {
Polish{Romanian {
Cases
ws80
ws120qv
90
qv11
0dt20
LFsl RKsl
RKbottRKtp
orom
icro1
micro2
micro3
conm
od
kfbco
noffrlam01
rlam50st
o50
sto25
0sea0
1
sea4
0
Δrr > +30%+10% < Δrr <+30%0% < Δrr < +10%Δrr = 0%0% > Δrr > -10%-10% > Δrr > -30%Δrr < -30%
Δrel = (rrexp–rrref)/rrref
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Relative change of 24h area average precipitation
Δrel
| Δrel |
Δrel = (rrexp–rrref)/rrref
QV0 RK MP CON RLAM
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Change of bias between simulated and measured area average precipitation
stratiform
convective
overestimation underestimation
Initial humidity Runge-Kuttasnow microphysics convection
bias > 200%100% < bias <200%bias = 100%100% > bias > 50%bias < 50%
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Conclusions until now …• Strongest effect (5-40%) on area average precipitation by:
• Initial humidity • Runge-Kutta• microphysics • convection scheme
• Strong effect for Roman and Greek cases • Vertical heat/moisture exchange (extreme change of RLAM)
• Runge-Kutta • reduces mean precipitation in most of the cases• and has an overall positive effect on the results
• None of the studies completely solves a QPF problem, but some give a significant improvement for single cases like • changes of snow microphysics for a case with overestimation
of stratiform precipitation • Kain-Fritsch/Bechtold for underestimated convective
precipitation
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Cross experiments
No. Sensitivity study
23 COSMO 4.0
24 COSMO 4.0 + 90% initial humidity + Runge-Kutta
25 COSMO 4.0 + Kain-Fritsch/Bechtold
26 COSMO 4.0 + 90% initial humidity + Runge-Kutta + Kain-Fritsch/Bechtold
27 COSMO 4.0 + modified Tiedtke scheme
28 COSMO 4.0 + 90% initial humidity + Runge-Kutta + modified Tiedtke scheme
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Relative change of area average precipitation in cross experiments compared to control simulation
Δrr > +30%+10% < Δrr <+30%0% < Δrr < +10%Δrr = 0%0% > Δrr > -10%-10% > Δrr > -30%Δrr < -30%
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Bias of reference run and cross experimentsDWD M-Swiss Italy HNMS IMGW NMA
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Relative bias of cross experimentsDWD M-Swiss Italy HNMS IMGW NMA
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Improvement of area average precipitation in numbers…
• 17 cases improved by one of the studies: COSMO4.0+• KFB: 5 cases (3C- / 2S+)• QV90+RK+Tiedtkemod : 3 cases • QV90+RK+KFB : 3 cases• -/Tiedtkemod/RK+QV90: 2 cases
• 7 cases hardly affected or worse (5C-)
} 8S+/3S-
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Conclusions• COSMO4.0+
• reduced initial humidity• modified convection• Runge-Kutta
• has a positive impact on stratiform overestimation• little or negative impact on convective underestimation• Few cases are “solved”• COSMO Version 4.0 is a step forward!• Further improvements expected from Runge-Kutta.• We should have a closer look at the (initial) humidity fields. – Any
improvements in data assimilation expected?• Convection schemes are the next thing to look at.
• Draft of a final report has been written and will be revised based on the discussion of PP QPF sessions in Athens and will be available in the next weeks
• publication of results planned until end of the year