Progress on new dynamical core of COSMO PP "COSMO-EULAG operationalization (CELO) Bogdan Rosa, Damian K. Wójcik, Michał Z. Ziemiański Institute of Meteorology and Water Management National Research Institute Warsaw, Poland Podleśna, 61 Email: bogdan.rosa@imgw.pl COSMO General Meeting, 11 – 14 September 2017, Jerusalem, Israel

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Overview of project tasks Task 1: Integration of EULAG DC with COSMO framework The EULAG model has been successfully coupled to the COSMO framework from technical point of view. Coupling of the EULAG DC code with fully implemented ICON physics parameterizations will be performed in the framework of Task 5 of the project (postponed - due to unavailability of the official implementation of COSMO with ICON parameterizations). The task aimed at investigation and implementation of the strategy regarding lowest level of EULAG dynamical core on the surface will be carried out within COSMO Priority Project EX-CELO (In current implementation there is no additional surface layer). Task 2: Consolidation and optimization of the EULAG DC formulation This task has been completed. Task 3: Eulag DC code restructuring and engineering The remaining task, namely, implementation of a basic restart subroutine in the CE has been postponed for the next COSMO year (11.2017 - 03.2018). 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 2

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Overview of project tasks Task 4: Optimization and testing of COSMO with EULAG DC Efforts aimed at tuning of the current COSMO-EULAG model have been already initiated. Once the COSMO-EULAG with fully implemented ICON physics is available (Task 5) optimization and testing of the model will be performed. Task 5: Integration and consolidation of the EULAG compressible DC with COSMO framework Implementation of ICON physics parameterizations to COSMO-EULAG (currently postponed). Our recent efforts have been focused on removing an observed pressure bias (successful). 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 3

Diagnosis of problem related to the pressure bias development Semi-realistic simulations using COSMO Runge-Kutta (RK) and compressible COSMO-EULAG (CE) were performed to diagnose for the problem of pressure bias development. Configuration: Turbulence parameterization is turned on Moist microphysics and saturation adjustment are turned off Soil (sea) processes are turned off Water vapour enters buoyancy and there are no sources / sinks of water vapour dt = 15 s Computational domain: Bay of Biscay (flat) dx = 2.2 km Test case: 15 November 2013 (Azoren High) Figures in following slides show time evolution of horizontally averaged pressure perturbations. The perturbations are calculated with respect to the time-evolving pressure from the driving COSMO-7 simulation. 4

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Semi-realistic simulations: results without absorber for pressure CE RK Disabling the pressure absorber in RK results in the development of a pressure bias similar to that observed in CE results. Semi-realistic simulations: results with absorber for pressure CE RK Pressure bias is tremendously reduced in simulations with pressure absorber Pa Pa 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 5

Verification of CE forecasts computed for Nov 2013 (24h forecast) Verification of the CE forecast concerns the whole month – November 2013 Realistic simulations were performed for each day separately (24h forecast) Horizontal step of the computational mesh is 2.2 km Domain corresponds to the standard operational COSMO-2 domain of Meteo-Swiss. The simulations were performed using both CE and RK – for comparison Sensitivity of the results to different values of mixing length (150m and 500m), vertical smoothing factor for explicit vertical diffusion (wichfakt) and diffusion coefficient for momentum (tkmmin) is also analyzed Topographical map of the domain Station network for surface verification 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 6

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Experiment settings Dynamics: In Cosmo Runge-Kutta setup moist quantities are advected using the „Bott2Strang” scheme In Cosmo-Eulag setup moist quantities are advected using the MPDATA A scheme For Cosmo Runge-Kutta irunge_kutta=1 and itype_fast_waves=2 dt = 10 s (RK), dt = 10 s (CE) Numerical and Smagorinsky diffusion are turned off for Cosmo-Eulag and on for Cosmo Runge-Kutta Microphysics: Standard one-moment COSMO microphysics parameterization including ice, rain, snow and graupel precipitation (igsp=4) Radiation: Calculated every 6 minutes Topographical corrections to radiation are turned off (lradtopo=F) Turbulence and convection scheme : Default turbulence setup for high-resolution NWP (itype_turb=3, limpltkediff=T) Shallow convection parameterization is turned off (lconv=F) Soil model: Multi-layer soil model is used (lsoil= T, lmulti_layer=T, lforest=T) 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 7

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Pressure (hPa) – forecast verification with pressure absorber CE wichfakt = 0.5 tkmmin = 0 RK <|RMSE|> = 1.122 <|ME|> = 0.160 <|RMSE|> = 1.123 <|ME|> = 0.164 CE wichfakt = 0 tkmmin = 0.4 RK <|RMSE|> = 1.112 <|ME|> = 0.155 <|RMSE|> = 1.122 <|ME|> = 0.162 Mean error is relatively small for both CE and RK. Before 18:00 simulations performed with RK are slightly more in line with observations than those performed with CE. After 18:00, the forecast computed using CE is in better agreement with observations. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 8

Before pressure correction With pressure absorber Horizontal wind (m/s) at 10 m (with pressure absorber) Before pressure correction With pressure absorber CE wichfakt = 0.5 tkmmin = 0 CE RK <|RMSE|> = 2.226 <|ME|> = 0.213 <|RMSE|> = 2.225 <|ME|> = 0.212 <|RMSE|> = 2.192 <|ME|> = 0.158 CE wichfakt = 0 tkmmin = 0.4 CE RK <|RMSE|> = 2.222 <|ME|> = 0.214 <|RMSE|> = 2.223 <|ME|> = 0.210 <|RMSE|> = 2.186 <|ME|> = 0.158 Little effect of pressure absorber on horizontal wind. Pressure absorber makes CE results more closer to both RK results and observations. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 9

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Temperature at 2 m – forecast verification with pressure absorber CE wichfakt = 0.5 tkmmin = 0 RK <|RMSE|> = 2.174 <|ME|> = 0.656 <|RMSE|> = 2.238 <|ME|> = 0.902 CE wichfakt = 0 tkmmin = 0.4 RK <|RMSE|> = 2.165 <|ME|> = 0.643 <|RMSE|> = 2.213 <|ME|> = 0.875 Results computed using CE are closer to observations than those computed with RK. No effect resulting from different values of parameters wichfakt and tkmmin. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 10

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Dew point temperature at 2 m – verification with pressure absorber CE wichfakt = 0.5 tkmmin = 0 RK <|RMSE|> = 2.664 <|ME|> = 0.856 <|RMSE|> = 2.639 <|ME|> = 0.884 CE wichfakt = 0 tkmmin = 0.4 RK <|RMSE|> = 2.644 <|ME|> = 0.850 <|RMSE|> = 2.628 <|ME|> = 0.875 Results from both models are in good quantitative agreement. Low sensitivity to different settings of vertical smoothing factor and minimal diffusion coefficients. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 11

Precipitation – forecast verification (wichfakt = 0.5, tkmmin = 0) CE RK Probability of Detection Probability of Detection CE RK Probability of Detection Probability of Detection Success Ratio Success Ratio Numerical results computed using CE and RK (with pressure absorber) are in good quantitative agreement. The differences are in the range of statistical uncertainty. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 12

Precipitation cntd. – forecast verification (wichfakt = 0 Precipitation cntd. – forecast verification (wichfakt = 0.5, tkmmin = 0) CE RK Probability of Detection Probability of Detection CE RK Probability of Detection Probability of Detection Success Ratio Success Ratio Also for larger precipitation the differences are in the range of statistical uncertainty. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 13

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Conclusions Problem related to pressure bias development has been diagnosed and solved by employing linear absorber at the lateral boundary condition Verification of 24h forecast for the whole month (Nov. 2013) was performed. We compared horizontal wind, temperature, dew point temperature, pressure and precipitation both with observations and numerical results obtained from simulations performed with RK dynamical core There is overestimation of surface wind in CE. It may be related to different implicit diffusion of CE dynamical core and may need a dedicated tuning. Temperature at (2m) computed using CE is closer to observations than temperature computed with RK DC. Dew point temperature and precipitation computed using both models are in good quantitative agreement and weakly sensitive to different settings of vertical smoothing factor and minimal diffusion coefficients. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 14

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Modeling of Alpine convection from the 19 July 2013 Here we present results of simulations of Alpine convection performed with the new CE model (the most recent version with pressure absorber) The simulations have been performed using four one-way nested domains having the horizontal grid size of 2.2, 1.1, 0.55 and 0.28 km The simulations are compared with benchmark simulations of COSMO-Runge-Kutta with grid sizes of 2.2 and 1.1 km and satellite data 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 15

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Realistic prognostic simulations of convective Alpine weather Computational domains employed in this study. The left panel shows domain corresponding to 2.2 km grid resolution. Analogously, the right panel - domain with finer grid resolution i.e. 0.55 km. The four black markers (dots) in the right panel indicate corners of the averaging area for statistics. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 16

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Cloud cover Cloud cover (grayscale) derived from the albedo product of the HRV channel of Meteosat and underlying topographic map (brown to copper colors). Distribution of cloud cover (grayscale) from numerical simulations with 2 different models RK (top) and CE (bottom) at grid resolution 2.2 km. The cloud cover was evaluated based on the total liquid and ice water products of the COSMO framework. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 17

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Cloud cover – results from numerical simulations Cloud cover (grayscale) at 15 UTC derived from simulation results of RK and CE. Different panels correspond to different grid resolution i.e. 1.1, 0.55 and 0.28 km. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 18

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Cross-section through vertical velocity The vertical cross sections at 15:00 showing instantaneous vertical velocity and liquid water content (contours every 0.25 g / kg starting from 0.25 g / kg). 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 19

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Horizontally averaged cloud cover and precipitation Time series of horizontally averaged total cloud cover for different model setups. Data dumped every 15 min. Time series of horizontally averaged precipitation rates for different model setups 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 20

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Documentation Extended abstract - 34th International Conference on Alpine Meteorology, Reykjavík, Iceland, 18-23 June 2017: Compressible EULAG solver for limited-area numerical Alpine weather prediction in the COSMO consortium Damian K. Wójcik, Bogdan Rosa, Michał Z. Ziemiański 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 21

19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel Final conclusions and future work From technical point of view EULAG model has been successfully coupled to the COSMO framework Performed verification leads to conclusion that the CE results are close to observations A robustness of CE numerics allows to perform simulations with horizontal grid sizes below 1km (0.28 km) CE simulations indicate significant influence of orographic forcing on the model solutions so that no general grid convergence is obtained. CE results indicate a dependence of the evolution of model representation of precipitation on the grid size. Request to extend PP CELO until 8.2018 has been submitted The additional time is needed to complete Tasks 3, 4 and 5 The project will be finalized with delivery of fully operational weather prediction package without data assimilation. 19th COSMO General Meeting, 11-14 September 2017, Jerusalem, Israel 22

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