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Alpine Weather Forecasting

Alpine Weather Forecasting. Neil Stringfellow CSCS Swiss National Supercomputing Centre. CSCS – Swiss National Supercomputing Centre. National Supercomputing Centre since 1992 Provides compute facilities and scientific support to Swiss research community

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Alpine Weather Forecasting

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  1. Alpine Weather Forecasting Neil Stringfellow CSCS Swiss National Supercomputing Centre

  2. CSCS – Swiss National Supercomputing Centre • National Supercomputing Centre since 1992 • Provides compute facilities and scientific support to Swiss research community • Federal High Schools, Federal research institutes, Universities and University of Applied Sciences • Switzerland is currently planning its national strategy in HPC • CSCS also provides facilities to MeteoSwiss for operational weather forecasting HPC User Forum – Tucson - 9th Sept 2008

  3. CSCS User Base • Scientists drawn from a large number of disciplines • Climate research is a major research field HPC User Forum – Tucson - 9th Sept 2008

  4. Climate Modelling at CSCS • One of CSCS “ALPS” projects awarded to model hydrological cycle in Alpine Environment • Various software packages are run at CSCS • Echam5 & Echam5-HAM (Atmosphere & Aerosol) • CCSM & CSM with Carbon Cycle • COSMO climate model (regional and local) • No non-coupled ocean modelling HPC User Forum – Tucson - 9th Sept 2008

  5. Economic Importance of Climate Modelling • Tourism • Important to know long-term effects for planning where to locate ski resorts • Agriculture • Swiss agriculture is expected to benefit from modest temperature increases (up to 2°C) • Electricity generation • Hydro power requires precipitation • Nuclear power plants require cooling HPC User Forum – Tucson - 9th Sept 2008

  6. Water and Electricity Generation • Swiss electricity generation is carbon neutral! • Approx 60% from hydroelectric power plants • Most of the rest is Nuclear • Need to know precipitation levels for electricity generation • Cooling of nuclear power plants relies on water, and the temperature of that water • During the 2003 summer heatwave, electricity production from nuclear was reduced by 25% HPC User Forum – Tucson - 9th Sept 2008

  7. Future Climate Scenarios • Current prediction is for higher temperatures and lower precipitation • Glacial melt will increase in near future but water available for hydro-generation will reduce from present levels by 2050 • Warmer water will reduce cooling capacity for nuclear reactors • There is a need for research, and in particular numerical simulation HPC User Forum – Tucson - 9th Sept 2008

  8. MeteoSwiss and CSCS • MeteoSwiss is the Swiss federal weather office • MeteoSwiss run operational weather forecast model at CSCS • MeteoSwiss runs the COSMO model from the COSMO consortium • This is a local (not global) model • CSCS provides compute resources and technical and scientific services HPC User Forum – Tucson - 9th Sept 2008

  9. High Resolution Forecasting • European Windstorms Lothar and Martin caused destruction and loss of life in 1999 • Not detected by national weather services • Demands for improved forecasting • Additional requirements for accurate forecasting from Nuclear Power Plant operators Destruction in black forest due to Windstorm Lothar HPC User Forum – Tucson - 9th Sept 2008

  10. European Windstorms - background • Windstorms occur in Winter, typically December to February • Sometimes called “Winter storms” or Orkan • Naming system similar to hurricanes • Names issued by Free University of Berlin • Actually all high and low pressures are named • Historically have caused major loss of life • Mainly due to dyke breaches in Netherlands • Occasionally missed by national weather services • 1987 Storm in United Kingdom • “Lothar” in 1990 by Germany (and others inc. Switzerland) HPC User Forum – Tucson - 9th Sept 2008

  11. Features of European Windstorms • Don’t dissipate quickly over land • They sometimes intensify over land • Often occur in clusters of 2 or more • Daria & Herta (Jan 1990) • Vivan & Wiebke (Feb 1990) • Désirée, Esther, Fanny, Hetty (Jan 1998) • Lothar & Martin (Dec 1999) • Wind speeds, insurance losses and fatalities are similar to U.S. hurricanes • No massive loss of life in modern times to compare with Hurricanes Jeanne and Katrina HPC User Forum – Tucson - 9th Sept 2008

  12. Swiss Topography • High mountains and deep valleys lead to extreme winds during storms • 225 km/h on Aetsch Glacier for Kyrill • 285 km/h at Jungfraujoch for Wiebke HPC User Forum – Tucson - 9th Sept 2008

  13. Insurance Losses • European Windstorms are the second highest cause of insurance losses • Highest losses are caused by U.S. Hurricanes • Average annual loss is around $2 Billion • 5 of top 20 biggest ever insurance losses are due to European Windstorms HPC User Forum – Tucson - 9th Sept 2008

  14. Losses of Big Storms * affected Switzerland Combined Lothar/Martin (25th & 27th Dec. 1999) would be 8th largest loss Source: Swiss Re HPC User Forum – Tucson - 9th Sept 2008

  15. Lothar/Martin – December 1999 • Storm Lothar crossed France, Germany and Switzerland on 24th & 25th December 1999 • Storm Martin followed a similar path on 26th & 27th December • Many fatalities, billions of dollars of damage • Not predicted by National Weather Services HPC User Forum – Tucson - 9th Sept 2008

  16. Advances in Prediction • Study of prediction of Lothar/Martin (Walser et. al) looked at 3 aspects • Moist Singular Vectors • Different approach to calculate initial perturbations for ensemble forecasts • Increased Resolution • Ensembles • Showed great potential for improved forecasts HPC User Forum – Tucson - 9th Sept 2008

  17. opr SVs, x~80 km Forecast storm Lothar: max. wind gusts t+(42-66) (1) • Configuration: • opr SVs, 80 km • opr SVs, 10 km, 80 km topo • moist SVs, 10 km,80 km topo • moist SVs, 10 km • moist SVs, 10 km,10 members

  18. opr SVs, x~10 km, x topography ~ 80 km Forecast storm Lothar: max. wind gusts t+(42-66) (2) • Configuration: • opr SVs, 80 km • opr SVs, 10 km, 80 km topo • moist SVs, 10 km,80 km topo • moist SVs, 10 km • moist SVs, 10 km,10 members

  19. moist SVs, x~10 km, x topography ~ 80 km Forecast storm Lothar: max. wind gusts t+(42-66) (3) • Configuration: • opr SVs, 80 km • opr SVs, 10 km, 80 km topo • moist SVs, 10 km,80 km topo • moist SVs, 10 km • moist SVs, 10 km,10 members

  20. moist SVs, x~10 km Forecast storm Lothar: max. wind gusts t+(42-66) (4) • Configuration: • opr SVs, 80 km • opr SVs, 10 km, 80 km topo • moist SVs, 10 km,80 km topo • moist SVs, 10 km • moist SVs, 10 km,10 members

  21. moist SVs, x~10 km, 10 members Forecast storm Lothar: max. wind gusts t+(42-66) (5) • Configuration: • opr SVs, 80 km • opr SVs, 10 km, 80 km topo • moist SVs, 10 km,80 km topo • moist SVs, 10 km • moist SVs, 10 km,10 members

  22. Going from 80km to 10km ECMWF EPS (80 km) COSMO-LEPS (10 km) HPC User Forum – Tucson - 9th Sept 2008

  23. Current Situation of MeteoSwiss • Forecast runs on a 896 core Cray XT4 • Runs 8 times per day for ~ 30 mins HPC User Forum – Tucson - 9th Sept 2008

  24. Need for High Resolution • The forecast simulation resolves Switzerland using a two-grid refinement • coarse 6.6km spacing between grid points • 385 x 325 grid, 60 atmospheric levels over Western Europe, 72 second time step with numerical leapfrog scheme • fine simulation uses 2.2km spacing • 520 x 350 grid, 60 atmospheric levels over “Alpine Arc”, 20 second time step with Runge-Kutta numerical scheme • Many features in Switzerland were not resolved at the older 7km resolution • Few valleys are resolved at this resolution HPC User Forum – Tucson - 9th Sept 2008

  25. Resolution change 6.6km to 2.2km COSMO-7 (6.6 km) COSMO-2 (2.2 km) HPC User Forum – Tucson - 9th Sept 2008

  26. Example - Magadino Plain • Magadino Plain is the lowest part of Switzerland • Lowest point is on shore of Lago Maggiore • Plane is surrounded by mountains • At 6.6km resn it resolves to be a 1km high plateau • At 2.2km resn it has a valley floor at 200m height HPC User Forum – Tucson - 9th Sept 2008

  27. Parameterisation v Direct Simulation • At low resolution many features cannot be directly modelled - have to be parameterised • Higher resolutions allow more physics • 6.6km -> 2.2km deep convection is computed explicitly • Higher resolution also allows modelling of valley winds HPC User Forum – Tucson - 9th Sept 2008

  28. Full Suite • 7 components • Interpolation, assimilation and 24 hour forecast on coarse grid • Interpolation and assimilation on fine grid • Interpolation and 24 hour forecast on fine grid • All components have to complete in ~20 minutes • To allow for data post-processing to complete within 30 minutes of start • Suite runs every 3 hours • Twice per day a 72 hour coarse grid forecast is added HPC User Forum – Tucson - 9th Sept 2008

  29. ECMWF IFS • ECMWF IFS(global) • 25km, 91 levels • 2 x 240h per day+ 2 x 78h per day COSMO-7 • COSMO-7(regional) • 6.6km, 60 levels • 2 x 72h per day COSMO-2 • COSMO-2(local) • 2.2km, 60 levels • 8 x 24h per day Model Heirarchy HPC User Forum – Tucson - 9th Sept 2008

  30. 12 15 18 21 00 03 06 09 12 15 18 COSMO-7 COSMO-2 Full Suite Forecast .. +72h .. +72h Full Suite Timeline Time UTC HPC User Forum – Tucson - 9th Sept 2008

  31. Example of Improvement - Wind • South of Zurich Lake • Wind field at 6.6km and 2.2km resolution • Features only resolved at high resolution HPC User Forum – Tucson - 9th Sept 2008

  32. Other Extreme Events in Switzerland • Summer Flooding • Summer floods over central Europe in 2005 • 38th largest insurance loss 1970-2007 (Swiss Re) • Summer Heatwaves • European heatwave of 2003 responsible for 35,000 deaths • 8th largest number of deaths from natural catastrophe 1970-2007 • Others, e.g. hailstorms halted Tour de Suisse in 2007 HPC User Forum – Tucson - 9th Sept 2008

  33. HPC Issues in Climate/Weather • What is typical high-end Climate HPC work? • Future Modelling in Climate/Weather • Higher resolution • More physics • Ensembles • Very complex and large codes • Not likely to be an early adopter or new languages • No compact kernel for accelerators HPC User Forum – Tucson - 9th Sept 2008

  34. I/O Rate and Storage • Many codes use proprietary formats • Grib format in European codes • No widespread adoption of parallel I/O • often I/O is done on one or a few processes • Increasing amounts of data being generated • reluctance to delete data • two-thirds of CSCS archive is used for Climate and Weather data HPC User Forum – Tucson - 9th Sept 2008

  35. Acknowledgements • Great many thanks go to Andre Walser and Daniel Leuenberger of MeteoSwiss for providing slides and answering questions HPC User Forum – Tucson - 9th Sept 2008

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