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Federal Department of Home Affairs FDHA Federal Office of Meteorology and Climatology Meteo. Swiss

Federal Department of Home Affairs FDHA Federal Office of Meteorology and Climatology Meteo. Swiss COSMO Priority Project ’Tackle deficiencies in quantitative precipitation forecasts’ S. Dierer 1, M. Arpagaus 1, U. Damrath 2, A. Seifert 2, J. Achimowicz 8, E. Avgoustoglou 7, M. Baldauf 2, R. Dumitrache 9, V. Fragkouli 7, F. Grazzini 3, P. Louka 7, P. Mercogliano 6, P. Mezzasalma 3, M. Milelli 4, D. Mironov 2, A. Morgillo 3, E. Oberto 4, A. Parodi 5, I. V. Pescaru 9, U. Pflüger 2, A. Sanna 4, F. Schubiger 1, K. Starosta 8, M. S. Tesini 3 1 Meteo. Swiss (CH), 2 DWD (D), 3 ARPA-ER (IT), 4 ARPA-P (IT), 5 Uni Genova (IT), 6 CIRA-CMCC (IT), 7 HNMS (GR), 8 IMGW (PO), 9 NMA (RO) COSMO General Meeting, 19 September 2007, Athens

Aim of PP QPF Good quantitative precipitation forecast is a challenging task – also

Aim of PP QPF Good quantitative precipitation forecast is a challenging task – also for the COSMO model: 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 The project has a focus on model deficiencies – not on errors from e. g. initial and large scale conditions PP QPF 2

Overview of PP QPF • Task 1: Selection of test cases representative for „typical“

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 PP QPF 3

List of test cases from all countries PP QPF DATE INSITUTION Overestimation (+)/underestimation (-)

List of test cases from all countries PP QPF 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. 2005 Meteo. Swiss + strat occluded front+orogr. 22. 03. 2005 Meteo. Swiss + strat warm front 12. 07. 2005 Meteo. Swiss + conv - 17. 12. 2005 Meteo. Swiss + 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. 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 4

Forecast errors • • 10 cases of stratiform overestimation (8 from D, CH and

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) PP QPF 5

Sensitivity studies • • • PP QPF 1. Changes of initial conditions 2. Changes

Sensitivity studies • • • PP QPF 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 6

Sensitivity studies: initial conditions • Soil moisture increased/decreased by 20% • Initial humidity increased/decreased

Sensitivity studies: initial conditions • Soil moisture increased/decreased by 20% • Initial humidity increased/decreased by 10% PP QPF 7

Sensitivity studies: numerical methods • Halved time step • Leapfrog, tri-cubic semi-Lagrange advection of

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 PP QPF 8

Sensitivity studies: physics 1 microphysics • New warm rain scheme (Seifert and Beheng; 2001)

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 PP QPF 9

Sensitivity studies: physics 2 – convection • Modified Tiedtke scheme • Kain-Fritsch/Bechtold scheme •

Sensitivity studies: physics 2 – convection • Modified Tiedtke scheme • Kain-Fritsch/Bechtold scheme • No parameterization of deep convection PP QPF 10

Sensitivity studies: physics 3 – PBL • Decreased/increased scaling factor of height of laminar

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 PP QPF 11

Relative change of 24 h area average precipitation, first forecast day (06 – 30)

Relative change of 24 h area average precipitation, first forecast day (06 – 30) Δrel = (rrexp–rrref. Runge-Kutta )/rrref Initial humidity Cases Romanian { Polish { Convection scheme Snow microphysics Vertical heat/moisture exchange Greek { Ital. (Euro. LM){ Ital. (LAMI) { { German{ w w s 80 s 1 20 qv qv 9 11 0 dt 0 LF 20 s RK Rl K bo sl RKtt or tp om i m cro m icr 1 i o cocro 2 nm 3 o kf d cob n rla rolfafm m 0 5 s 0 1 sto to 5 25 0 se a 01 a 4 0 Swiss PP QPF Δrr > +30% +10% < Δrr <+30% 0% < Δrr < +10% Δrr = 0% 0% > Δrr > -10% > Δrr > -30% Δrr < -30% 12

Change of bias between simulated and measured area average precipitation overestimation underestimation stratiform bias

Change of bias between simulated and measured area average precipitation overestimation underestimation stratiform bias > 200% 100% < bias <200% bias = 100% > bias > 50% bias < 50% convective Initial humidity PP QPF Runge-Kutta snow microphysics convection 14

Conclusions until now … • • Strongest effect (5 -40%) on area average precipitation

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 PP QPF 15

Cross experiments No. Sensitivity study 23 COSMO 4. 0 24 COSMO 4. 0 +

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 PP QPF 16

Relative change of area average precipitation in cross experiments compared to control simulation Δrr

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% > Δrr > -30% Δrr < -30% PP QPF 19

Bias of reference run and cross experiments DWD PP QPF M-Swiss Italy HNMS IMGW

Bias of reference run and cross experiments DWD PP QPF M-Swiss Italy HNMS IMGW NMA 20

Relative bias of cross experiments DWD PP QPF M-Swiss Italy HNMS IMGW NMA 21

Relative bias of cross experiments DWD PP QPF M-Swiss Italy HNMS IMGW NMA 21

Improvement of area average precipitation in numbers… • 17 cases improved by one of

Improvement of area average precipitation in numbers… • 17 cases improved by one of the studies: COSMO 4. 0+ • KFB: 5 cases (3 C- / 2 S+) • QV 90+RK+Tiedtkemod : 3 cases • QV 90+RK+KFB : 3 cases 8 S+/3 S • -/Tiedtkemod/RK+QV 90: 2 cases • 7 cases hardly affected or worse (5 C-) } PP QPF 22

Conclusions • • • COSMO 4. 0+ • reduced initial humidity • modified convection

Conclusions • • • COSMO 4. 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 PP QPF 23