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ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 1
Norm Phillips’ work in Data Assimilation A.Hollingsworth Seattle Jan 2004
A.Hollingsworth, A.Simmons, W. Zwieflhoefer,
M.Dragosavac, S.Uppala, J.Woollen*, D.Marbouty,
J-N Thepaut, R Engelen, A Dethof,
ECMWF
* NCEP
The Interplay of Computer Power, Computer
Architectureand Numerical Algorithms in the
progress of Numerical Weather Prediction
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 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
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 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.
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 4
9 September 2000 - 12 UTC D+6 forecast
AN TL511 D+6 TL319 D+6 AN TL511 D+6 TL319 D+6
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 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)
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 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
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 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.
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 8
1987 1992 1997 1998 20000
200
400
600
800
1000
1200
1400
1600F
orec
ast d
ays
per
com
pute
day
Eulerian scheme
Operational scheme
T106L19CRAY X-MP/4
T213L31CRAY C90/16
T213L31
Fujitsu VPP700/116
TL319L50
Fujitsu VPP700/116
Semi-Lagrangian algorithmic improvements - operational resolutions
TL511L60
Fujitsu VPP5000/100
Factors 1 4 12 72 150Reasons Semi-Lagrangian Reduced Gaussian Linear grid Higher resolutions
two-time levels stratosphere
x 4 x 12 x 72 x 150
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 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
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 10
Sustained forecast improvements in both hemispheres Convergence of skill
between the hemispheres
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 11
A look to the past
Let us now praise great men -
Day 6 June 1944
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 12
Observations for 12UTC 3 June 1944
423 pilot balloons
Observations supplied by Jack Woollen, NOAA/NWS/NCEP
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 13
Observations for 12UTC 3 June 1944
676 SYNOPS 112 SHIPS
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 14
10m wind and low cloud 00UTC 6 June 1944
T159 3D-Var analysis
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 15
10m wind and low cloud 06UTC 6 June 1944
T159 3D-Var analysis
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 16
10m wind and low cloud 12UTC 6 June 1944
T159 3D-Var analysis
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 17
10m wind and low cloud 18UTC 6 June 1944
T159 3D-Var analysis
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 18
The early morning of June 6 1944: Low cloud and westerly winds off the Normandy beaches
Pictures fromUS NavalHistorical Center
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 19
June 6 1944: Clear skies over the channel and later over the Normandy beaches
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 20
Comparison with contemporary charts
Reproduced from www.meteo.fr
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 21
10m wind and cloud T799 from 00UTC 3 June 1944
H+78H+54
H+84 H+90
06UTC 5 June
12UTC 6 June
06UTC 6 June
18UTC 6 June
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 22
10m wind & cloud with 25km (T799) from 12UTC 3 June
H+66H+42
H+72 H+78
06UTC 5 June
12UTC 6 June
06UTC 6 June
18UTC 6 June
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 23
http://www.ecmwf.int/newsevents/releases/030604.html
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 24
Historical perspective1994 (ten years ago):
Cray C90-16 installed in 1992
16 processors
Sustained performance: 6 gigaflops2004 (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)
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 25
Climate Monitoring and the Chemical Weather Forecast SystemLong-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.
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 26
Structure of an Earth-system model - all processes and interactions must be well represented
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 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.
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 28
CO2 – Troposphere – May 2003
CO2 tropospheric columns are assimilated from AIRS infrared observations. Monthly mean distribution for May 2003
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 29
Monitor & Forecast AEROSOL (& Fires)
Model and assimilate global aerosol informationHeritage: -Instruments: MERIS, MODIS x 2, MISR, SEAWIFS,
POLDERData Mgt tbdR/T “Modelling “Sources/ Sinks “Data Assim. “Validation “
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 30
Monitor & Forecast Reactive GasesOzone Hole 1 Oct 2003
Southern Hemisphere
1 Map of total column O3
2 Cross-section
3 Validation v. Neumayer ozonesonde
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 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 scienceon the political scienceon the operational systems to meet customer
needs
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 32
EndThank you for your attention!
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 33
7 September 2000 - 12 UTC D+4 forecast
ANALYSIS TL511 D+4 TL319 D+4
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 34
8 September 2000 - 12 UTC D+5 forecast
AN TL511 D+5 TL319 D+5 ANALYSIS TL511 D+5 TL319 D+5
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 35
ECMWFJNWP+50 Hollingsworth, Washington DC June 2004 Slide 36
Group Captain J.M. Stagg
Photograph fromwww.metoffice.com
Meteorological advisor to Eisenhower
Responsible for reconciling the forecasts of three teams:
The Met Office The Royal Navy The US Air Force