1 / 36

Norm Phillips’ work in Data Assimilation A.Hollingsworth Seattle Jan 2004

Norm Phillips’ work in Data Assimilation A.Hollingsworth Seattle Jan 2004. The Interplay of Computer Power, Computer Architecture and Numerical Algorithms in the progress of Numerical Weather Prediction. A.Hollingsworth, A.Simmons, W. Zwieflhoefer,

edith
Download Presentation

Norm Phillips’ work in Data Assimilation A.Hollingsworth Seattle Jan 2004

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Norm Phillips’ work in Data Assimilation A.Hollingsworth Seattle Jan 2004 The Interplay of Computer Power, Computer Architecture and Numerical Algorithms in the progress of Numerical Weather Prediction A.Hollingsworth, A.Simmons, W. Zwieflhoefer, M.Dragosavac, S.Uppala, J.Woollen*, D.Marbouty, J-N Thepaut, R Engelen, A Dethof, ECMWF * NCEP

  2. Scope of Talk • NWP requirements for resolution • Semi-Lagrangian time-schemes • Implementing efficient schemes on parallel machines • Operational and scientific implications of such economies • A look back to June 1944 • A look to the challenges of the future

  3. Significance of model and analysis resolution • Model resolution can control the success of forecasts for major rain systems. • The next few pictures illustrate the importance of resolution (40km v 65km) in one of a series of episodes of heavy rains in the Mediterranean • In the 40km model, the forecast successfully stretched, and then rolled up, the streamer of Potential Vorticity, while the 65 km model was a bust on these critical features.

  4. 9 September 2000 - 12 UTC D+6 forecast AN AN TL511 D+6 TL319 D+6 TL511 D+6 TL319 D+6

  5. Paying for Model Resolution • The change in 2000 at ECMWF from a 65km (T319) to a 40 km (T511) model had a big positive impact, as was expected from hundreds of days of pre-operational trials. • Dritschel et al. (1999) imply that 15km resolution is needed for a good 5-day forecast of the PV field – realisable about 2010. • Resolution is very costly (computer cost increases as ~cube of resolution). • Several approaches can meet the need • Increase the money stream (v.difficult) • Keep the money-stream constant and rely on Amdahl’s Law. • Keep the money-stream constant, rely on Amdahl’s Law, and use efficient time schemes (semi-implicit, semi-Lagrangian)

  6. The semi-Lagrangian scheme, integrates the equations of motion by • Calculating, for every point on the grid, the trajectory from the departure point (at t-1) • Interpolating the (t-1) values to the departure points • Advecting the values forward along the trajectories

  7. Parallellism & Communication on Distributed Memory Machines • Efficient time schemes require the solution of global equations. • One cannot get all the data into one processor, soA continuous complex shuffling / re-shuffling of the data is required to do a global calculation in many small steps • The figure illustrates the many data transpositions needed to pass from physical to Fourier to legendre space and back again • The implication is that the speed & capacity of the inter-processor communication is as crucial as the processor power.

  8. x 4 x 12 x 72 x 150

  9. Implications of numerical efficiency for productivity & vendor competition • Current semi-Lagrangian schemes offer very substantial gains in efficiency • Without those gains ECMWF could not afford • Deterministic model at 40 km (T511) • 51 member Ensemble system at 80km (T255) • Advanced 4D-Var assimilation system • Assimilation of millions of pieces of data from several dozen satellite instruments • Coupled seasonal forecast systems at 2 deg. (T95) • At best ECMWF could afford a 2-day forecast at T511 • We certainly could not plan a 25 km system (T799/L90) in 2005

  10. Sustained forecast improvements in both hemispheres Convergence of skill between the hemispheres

  11. A look to the pastLet us now praise great men -Day 6 June 1944

  12. Observations for 12UTC 3 June 1944 423 pilot balloons Observations supplied by Jack Woollen, NOAA/NWS/NCEP

  13. Observations for 12UTC 3 June 1944 676 SYNOPS 112 SHIPS

  14. 10m wind and low cloud 00UTC 6 June 1944 T159 3D-Var analysis

  15. 10m wind and low cloud 06UTC 6 June 1944 T159 3D-Var analysis

  16. 10m wind and low cloud 12UTC 6 June 1944 T159 3D-Var analysis

  17. 10m wind and low cloud 18UTC 6 June 1944 T159 3D-Var analysis

  18. The early morning of June 6 1944: Low cloud and westerly winds off the Normandy beaches Pictures from US Naval Historical Center

  19. June 6 1944: Clear skies over the channel and later over the Normandy beaches

  20. Comparison with contemporary charts Reproduced from www.meteo.fr

  21. 06UTC 5 June 06UTC 6 June H+54 H+78 12UTC 6 June 18UTC 6 June H+84 H+90 10m wind and cloud T799 from 00UTC 3 June 1944

  22. 06UTC 5 June 06UTC 6 June H+42 H+66 12UTC 6 June 18UTC 6 June H+72 H+78 10m wind & cloud with 25km (T799) from 12UTC 3 June

  23. http://www.ecmwf.int/newsevents/releases/030604.html

  24. Historical perspective • 1994 (ten years ago): • Cray C90-16 installed in 1992 • 16 processors • Sustained performance: 6 gigaflops • 2004 (one decade later): • IBM Phase 3 • ~4000 processors (250-fold increase) • Sustained performance: 2 teraflops (~120-fold increase per decade) • Distributed memory systems and a competitive HPC market • 2013 (almost another decade): • Preparation of 10 km system in the Strategy Review • Unknown number of processors • Sustained performance: 200 teraflops (100-fold increase)

  25. Climate Monitoring and the Chemical Weather Forecast System • Long-range transport of air pollutants is a well established fact:- ~ 40% of the material in Europe arrived from Asia, via N.America • Satellite data provide a vast amount of data on atmospheric composition: reactive gases, smog, aerosol, greenhouse gases. • Extraction of the information on composition requires as the pre-requisite the sophisticated NWP assimilation systems to provide temperature, humidity, cloud, … • The GEMS consortium (10 Science institutes, 10 regional air-quality labs, ECMWF) will provide an operational global composition monitoring capability and a global /regional air-quality operational forecast capability, built around ECMWF system (funding by EU). • A fully interactive chemistry module in the global ECMWF model will pose substantial computational challenges.

  26. Structure of an Earth-system model- all processes and interactions must be well represented

  27. Monitor Greenhouse Gases:- CO2, N2O, CH4, CO CO2 – Stratosphere – May 2003 First analysis of stratospheric CO2 shows Brewer-Dobson type of circulation. Variability is also much smaller than in troposphere.

  28. CO2 – Troposphere – May 2003 CO2 tropospheric columns are assimilated from AIRS infrared observations. Monthly mean distribution for May 2003

  29. Monitor & Forecast AEROSOL (& Fires) • Model and assimilate global aerosol information • Heritage: - • Instruments: MERIS, MODIS x 2, MISR, SEAWIFS, POLDER • Data Mgt tbd • R/T “ • Modelling “ • Sources/ Sinks “ • Data Assim. “ • Validation “

  30. Monitor & Forecast Reactive Gases Ozone Hole 1 Oct 2003 Southern Hemisphere 1 Map of total column O3 2 Cross-section 3 Validation v. Neumayer ozonesonde

  31. Closing words • Magna Laudatio to JNWP / NMC / NCEP • for 50 years of pioneering leadership • Good wishes from ECMWF for your continued success. • The future will be at least as challenging as the past, • on the science • on the political science • on the operational systems to meet customer needs

  32. End Thank you for your attention!

  33. 7 September 2000 - 12 UTC D+4 forecast ANALYSIS TL511 D+4 TL319 D+4

  34. 8 September 2000 - 12 UTC D+5 forecast ANALYSIS TL511 D+5 TL319 D+5 AN TL511 D+5 TL319 D+5

  35. Group Captain J.M. Stagg Meteorological advisor to Eisenhower Responsible for reconciling the forecasts of three teams: The Met Office The Royal Navy The US Air Force Photograph from www.metoffice.com

More Related