1. Application of an adaptive radiative transfer parameterisation in a mesoscale numerical weather prediction model DWD Extramural research Annika Schomburg 1), Victor Venema 1), Felix Ament 2), Clemens Simmer 1) 1) Department of Meteorology, University of Bonn, Germany 2) University of Hamburg

2. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #2 Outline The adaptive radiative transfer scheme –General idea –Implementation Results –3in1 runs –Single runs –Preliminary new result Outlook

3. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #3 Adaptive parameterizations Accurate parameterization –Process-based –Computationally expensive Fast parameterization –Less processes (statistical) –Typically: biased Adaptive scheme –Combine: accurate and fast parametrization –Accurate one corrects biases of fast one

4. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #4 Adaptive RT: Spatial scheme Uses spatial correlations Update every 2.5 minutes one out of 5x5 columns For other 24 columns: search for similar column in the vicinity (search region 5x5 pixels) Similarity index to be minimised:

5. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #5 Implemented in COSMO 4.0 Adaptive scheme –Called every 2.5 minutes Reference high-resolution –δ-two-stream approximation (Ritter & Geleyn) –Full field computed every 2.5 min Comparison –Coarse-scheme COSMO-DE (2x2 columns) –Called every 15 minutes

6. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #6 Diurnal cycle error net flux Bias SWLW RMSD

7. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #7 Diurnal cycle error heating rates Bias SWLW RMSD

8. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #8 Error height profile heating rates Bias SWLW RMSD

9. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #9 Scale dependent errors Surface net fluxAtmospheric heating rate

10. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #10 Errors net flux for COSMO-EU SWLW

11. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #11 Physical consistency: LWP SWLW

12. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #12 Consistency: diurnal cycle SWLW

13. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #13 Spread single runs Total precipitation2m-TemperatureSurface pressure

14. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #14 Selection column accurate computation Optimized pattern: as before in this talk Global difference: largest difference in full field Local difference: largest difference in 5x5 regions Spiral pattern: regular pattern, close together Preliminary new results

15. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #15 Conclusions Adaptive radiative transfer makes computations more accurate (or efficient) Employs spatial and temporal correlations in atmosphere  in error fields of simplified computations

16. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #16 Outlook Develop a temporal spatial adaptive scheme –Improve our results for heating rates Question: what is a good error measure? –Bias & RMSD –Scales (temporal, spatial) –Locations (layers, regions) –Heating rates, fluxes & PAR Other parameterizations –Surface module (looking for 2 PhD students) –Aerosols, etc.

17. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #17 References Schomburg, A., V. Venema, F. Ament, and C. Simmer. Application of an adaptive radiative transfer scheme in a mesoscale numerical weather prediction model. Quarterly Journal of the Royal Meteorological Society, accepted 2011. Venema, V.K.C., A. Schomburg, F. Ament, and C. Simmer. Two adaptive radiative transfer schemes for numerical weather prediction models. Atmospheric Chemistry and Physics, 7, 5659-5674, doi: 10.5194/acp-7-5659-2007, 2007. Download: http://www2.meteo.uni-bonn.de/venema/articles/

18. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #18

19. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #19 Errors in the solar heating rates (W m-2) in the LM at the surface for 12.30 h UTC. (a) The two-stream calculation of the solar surface flux is the reference field (b) Cloud cover of low clouds (c) Total cloud cover (d) the 1-h persistence assumption, (e) the adaptive perturbation scheme, (f) the adaptive search scheme. The corresponding errors are shown in the same order in the third row.

20. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #20 The Idea: Adaptive parameterisation calculate error- estimator based on a simple radiation scheme for each grid point Grid points where… …Δ ‘large‘ …Δ ‘ small‘ Apply „perturbation method“ for surface fluxes Recalculate radiation fluxes with exact scheme Perturbation method:

21. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #21 RMSE perturbation methods

22. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #22 Approach Simple radiation scheme: → Multivariate linear regression Predictands: – longwave: – shortwave: transmissivity: Distinction of 4 categories, with different sets of predictors: solar cloud free infrared cloud free solar cloudy infrared cloudy

23. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #23 Simple radiation scheme CloudfreeCloudy Cosine of solar zenith angleLWP IWVCLCL Surface pressureCLCT Continental aerosolsCosine of solar zenith angle Cloud thickness IWV Temperature at cloud base Predictors: SOLAR

24. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #24 Simple radiation scheme : CloudfreeCloudy IWV Surface temperatureTemperature at cloud base Cosine of zenith angleSurface temperature CLCT Cloud thickness CLCL Cosine of zenith angle LWP Predictors INFRARED

25. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #25 Approach Implementation of adaptive scheme into LM –First tests and configuration on PC (small model domain) –After successfull implementation: exemplary cases on LMK-domain on parallel machine at DWD Horizontal resolution: 2.8 km Frequency of call to adaptive scheme: 2.5 min

26. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #26 Approach Problem: Radiation of 3 separate model runs not comparable due to different evolution of cloud field → Development of a model version „3 in 1“: –Calculation of the radiation fluxes hourly adaptive frequently (every 2.5 min)... in the same model run –Dynamics only influenced by frequent radiation Test for 3 summer days characterised with much convection

27. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #27 Correlation lengths for error fields (15:30 UTC) The covariance functions of the errors in the solar (a) and infrared (b) fluxes at the surface. Hourly Adaptive Hourly Adaptive

28. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #28 Instantaneous RMSE with adaptive scheme smoother error curves 21June 2004

29. Victor Venema, Victor.Venema@uni-bonn.de, COSMO General meeting, Rome, 5th September 2011, #29 Smoother developing of model variables with time Adaptive approach prevents „wavy“ structure of developing of variables with time Surface temperature 21 June 2004