Federal Department of Home Affairs FDHA Federal Office of Meteorology and Climatology MeteoSwiss COSMO Priority Project ’Tackle deficiencies in quantitative precipitation forecasts’ 29th EWGLAM Meeting, 9 October 2007, Dubrovnic 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 MeteoSwiss (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)

2 29th EWGLAM meeting | COSMO QPF project 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

3 29th EWGLAM meeting | COSMO QPF project 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

4 29th EWGLAM meeting | COSMO QPF project List of test cases from all countries DATEINSITUTIONOverestimation (+)/underestimation (-) Stratiform (strat)/convective(con) DWD+stratwarm sector DWD+stratcold front+orography DWD+Strat+convwarm front DWD-convcold front MeteoSwiss+stratoccluded front+orogr MeteoSwiss+stratwarm front MeteoSwiss+conv MeteoSwiss+stratorography ARPA-P-convcold front+orography ARPA-ER+stratoccluded front+orogr CIRA-CMCC-convcold front+orography CIRA-CMCC-conv NMA-stratcold front NMA-stratcold front+orography NMA-Strat+convcold front HNMS-conv HNMS-Strat+convwarm front HNMS-stratorography IMGW-stratcold front IMGW0stratcold front IMGW+strat IMGW+strat NMA+strat+convcold front NMA+stratcold front NMA-stratcold front

5 29th EWGLAM meeting | COSMO QPF project 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)

6 29th EWGLAM meeting | COSMO QPF project 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

7 29th EWGLAM meeting | COSMO QPF project Sensitivity studies: initial conditions Soil moisture increased/decreased by 20% Initial humidity increased/decreased by 10%

8 29th EWGLAM meeting | COSMO QPF project 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

9 29th EWGLAM meeting | COSMO QPF project 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

10 29th EWGLAM meeting | COSMO QPF project Sensitivity studies: physics 2 – convection Modified Tiedtke scheme Kain-Fritsch/Bechtold scheme No parameterization of deep convection

11 29th EWGLAM meeting | COSMO QPF project 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

12 29th EWGLAM meeting | COSMO QPF project Relative change of 24h area average precipitation, first forecast day (06 – 30) Initial humidity Runge-Kutta Snow microphysics Convection scheme Vertical heat/moisture exchange German { Swiss { Ital. (LAMI) { Ital.(EuroLM) { Greek { Polish { Romanian { Cases ws80 ws120 qv90 qv110 dt20 LFsl RKsl RKbott RKtp oro micro1micro2 micro3 conmod kfb conoff rlam01 rlam50 sto50 sto250 sea01 sea40 Δrr > +30% +10% < Δrr <+30% 0% < Δrr < +10% Δrr = 0% 0% > Δrr > -10% -10% > Δrr > -30% Δrr < -30% Δrel = (rr exp –rr ref )/rr ref

13 29th EWGLAM meeting | COSMO QPF project Relative change of 24h area average precipitation  Δrel  | Δrel | Δrel = (rr exp –rr ref )/rr ref QV0 RK MPCON RLAM

14 29th EWGLAM meeting | COSMO QPF project Change of bias between simulated and measured area average precipitation stratiform convective overestimationunderestimation Initial humidity Runge-Kuttasnow microphysics convection bias > 200% 100% < bias <200% bias = 100% 100% > bias > 50% bias < 50%

15 29th EWGLAM meeting | COSMO QPF project 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

16 29th EWGLAM meeting | COSMO QPF project Cross experiments No.Sensitivity study 23COSMO COSMO % initial humidity + Runge-Kutta 25COSMO Kain-Fritsch/Bechtold 26COSMO % initial humidity + Runge-Kutta + Kain-Fritsch/Bechtold 27COSMO modified Tiedtke scheme 28COSMO % initial humidity + Runge-Kutta + modified Tiedtke scheme

17 29th EWGLAM meeting | COSMO QPF project Overestimation of humidity? Monthly evaluation of mixing ratio for COSMO-EU within GOP Payerne, Switzerland Greifswald, Germany January July Greifswald Payerne

18 29th EWGLAM meeting | COSMO QPF project Precipitation bias of COSMO 3.19 vs much better 11 slightly better 4 no impact 8 slightly worse

19 29th EWGLAM meeting | COSMO QPF project 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%

20 29th EWGLAM meeting | COSMO QPF project Bias of reference run and cross experiments DWD M-SwissItalyHNMSIMGWNMA

21 29th EWGLAM meeting | COSMO QPF project Relative bias of cross experiments DWD M-SwissItalyHNMSIMGWNMA

22 29th EWGLAM meeting | COSMO QPF project 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-

23 29th EWGLAM meeting | COSMO QPF project 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

24 29th EWGLAM meeting | COSMO QPF project Precipitation bias of reference version

25 29th EWGLAM meeting | COSMO QPF project List of sensitivity studies by Axel Seifert, DWD

26 29th EWGLAM meeting | COSMO QPF project List of sensitivity studies by Axel Seifert, DWD

27 29th EWGLAM meeting | COSMO QPF project List of sensitivity studies by Axel Seifert, DWD

28 29th EWGLAM meeting | COSMO QPF project List of sensitivity studies by Axel Seifert, DWD

29 29th EWGLAM meeting | COSMO QPF project List of sensitivity studies by Axel Seifert, DWD

30 29th EWGLAM meeting | COSMO QPF project Summer case with underestimated precipitation - change of 24h area average precipitation sum with Kain-Fritsch/Bechtold by Axel Seifert

31 29th EWGLAM meeting | COSMO QPF project Sensitivity studies: better or worse agreement with measured area average precipitation (green: improved; red: worse)