Brief history of atmospheric model development NCEP operational models ECPC (Scripps) model

1. Brief history of atmospheric model developmentNCEP operational modelsECPC (Scripps) model Masao Kanamitsu

2. Short history (1) • Early 1900. Richardson • Used most complicated form of hydro-dynamical and thermo-dynamical equations (primitive equation). • Spent several months to make 24 hour forecast • Failure!! • 1940’s. Charney, Phillips • Simplification of prediction equations • 2-D regional. • Limited success • General Circulation model • NWS started Numerical Weather Prediction • 1950’s – 1960’s • Gradual increase in the complexity of the equations. • Barotropic Vorticity equation • Quasi-geostrophic models • Balance equation models • General Circulation Model development • 1970’s • Successful use of primitive equations • Hemispheric to global • Development of sophisticated physical processes • Parameterization (convection) • Radiation, boundary layer, etc.

3. Short History (2) • 1980’s • Further development of numerics and physics • Global model • Long integrations became possible • Shallow convection, gravity wave drag…. • Development of data assimilation • 1990’s-2000’s • Development of variational data assimilation • Ensemble forecast • Further increase in resolution (Parallel computer) • Move towards non-hydrostatic equations

4. Three streams of modeling • For weather forecasting Global model Regional model • For general circulation study • GFDL, NCAR, UCLA, NASA, ….. Global model still not merged with weather forecasting model • For regional simulation study • NCAR, Navy, CSU, Penn State, …. Becoming merged with weather forecasting models

5. GCM developments in 1970’s • GFDL (Princeton) under Smagorinsky Manabe • UCLA under Yale Mintz Arakawa • NCAR Kasahara and Washington • NASA(Somerville), Wisconsin(Johnson)…

6. NCEP (NMC) model development • Research Modeling moved to Princeton (GFDL) in 1960’s. The model development has been done independently between NMC and GFDL, with very little collaboration (radiation). NMC – Shuman, Cressman, … GFDL – Miyakoda, Kurihara NMC was world leader until 1978.

7. Establishment of ECMWF • 1976 • UK, Germany, France, Italy, Spain, Sweden, Finland, Belgium, Austria, Yugoslavia, Turkey, Greece, Denmark, Holland, Ireland, Portugal • Headed by Winn Nielsen, Lennart Bengtsson.

8. NCEP operational models

9. NCEP Models • Global model • Aviation (also provide B.C. for regional) • Medium range • Seasonal range • Regional model • Short range • Hurricane model (on call) • Rapid update cycle • Very short range (order of hourly)

10. Global model • Global Forecast System (MRF/GFS). • Mother of all models. • Covers the entire globe. • Troposphere to upper stratosphere • Reasonably high horizontal and vertical resolution (T362 L64, about 35km) • Hydrostatic • Spectral

11. Resolution comparison • U.S. T362L64 • ECMWF T799L91 • UK ~40km L50 (~T360L50)

12. Regional model • NGM (Phillips)  Eta  WRF • Used to be eta model, but recently replaced with WRF model developed at NCAR. • 12 km resolution • Non-hydrostatic • Grid point

14. Ensemble forecasting • Uncertainties in the forecast due to uncertainties in the initial condition. • Generate better forecast with ensemble average • Start forecast from slightly different initial conditions. • How to perturb the initial condition • Use most unstable mode • Use perturbation breeding

17. Merit and demerit of ensemble forecasting • Merit • Better forecast (ensemble average) • Probabilistic information • Demerit • Ensemble spread is too small. The ensemble member does not distribute around the truth. • Future • Initial perturbation • Perturbation of the model physics • Super ensemble (use of multiple models)

19. NWP and weather forecast • Model Output Statistics (MOS) • Obtain weather element statistically from model output. • Include model error correction • Contrast to Perfect Prog. Method (PPM) • Considered as evil from modelers

20. Performance comparison

21. What determines model performance • Atmospheric model • Higher resolution • Better numerics and physics • Analysis • Complexity in variational analysis • Data quality control • Telecommunication lines, decoders • Stability of computer system

22. NCEP operational data • http://www.emc.ncep.noaa.gov/mmb/nomads/index.shtml

23. Atmospheric modeling at Scripps

24. Experimental Climate Prediction Center (ECPC) G-RSM (1) • Global to Regional Spectral Model • Originated from NCEP global and Regional Spectral Model • Improved significantly at Scripps • Global and regional models merged together. • User friendly interface, but with modeling research in mind.

25. Experimental Climate Prediction Center (ECPC) G-RSM (2) • Runs on a variety of computers, including laptop, workstation, linux cluster, Mac cluster to Earth Simulator. • Need Linux operating system with fortran compiler. • User can change physics packages, and other components of the model. • Good tool to understand the capability of the model.

26. Difference in simulation due to difference in convection

27. Experimental Climate Prediction Center (ECPC) G-RSM (3) • Model, detailed instructions available from: g-rsm.wikispaces.com

30. ECPC forecasts • Seasonal (7-month) ensemble forecast once a month. • Downscaling of the ensemble seasonal forecast over U.S. • Coupled single member forecast once a month. • Daily 3 month forecast and downscaling.