Transcript Document
Changes at ECMWF
Walter Zwieflhofer
Head of Computer Division
CAS 2001, Annecy
Slide 1
ECMWF
Operational system (October 2001)
Data assimilation
4D-Var with a 12-hour data window
Horizontal resolution: 120 km for inner and 40 km for outer loops
Global atmospheric forecasts
Forecasts to 10 days from 12 UTC at 40 km resolution
Ensemble forecasts to 10 days with 51 members at 80 km resolution
Four forecasts per day to 3 days to provide boundary conditions for
some of the ECMWF Member States (40 km, 3D-Var)
Ocean wave forecasts
Global forecasts to 10 days at 40 km resolution
European waters forecasts to 5 days at 15 km resolution
Seasonal forecasts
Global forecasts to 6 months (ensemble with 30 members)
CAS 2001, Annecy
Slide 2
ECMWF
Forecasting-system changes since 1999
19r2 Increased resolution in stratosphere
22r3 New error variances (for Jb and Jo)
21r1 Assimilation of raw TOVS/ATOVS radiances
additional ATOVS data, improved land-surface,
21r4 New error statistics for 4D-Var Jb, SSMI wind data,
sea-ice and LW radiation
corrected use of humidity observations, increased
23r1 12-hourly 4D-Var
PBL resolution, improved cloud, convection and
23r3 T511/159 resolution, second ATOVS satellite,
orography.
increased angular resolution in wave model
22r1 Improved SSM/I QC and second SSM/I satellite
CAS 2001, Annecy
Slide 3
ECMWF
23r3
0.0
23r1
0.0
S Hem
22r3
0.5
22r1
0.5
21r4
1.0
23r3
1.0
23r1
1.5
22r3
1.5
21r4
2.0
21r1
2.0
19r2
2.5
21r1
Mean reduction in day-one error measured in pre-operational trials
19r2
N Hem
2.5
Evolution of forecast skill for northern
and southern hemispheres
CAS 2001, Annecy
Slide 4
ECMWF
Error distribution for Day 5 (Europe)
CAS 2001, Annecy
Slide 5
ECMWF
Annual-mean RMS errors against analyses
from WMO scores
CAS 2001, Annecy
Slide 6
ECMWF
Planned improvements
2002
Increase of the inner loop resolution of
4D-Var from 120 km to 80 km
2003-2004
Assimilation of cloud and rain in 4D-Var
Higher vertical resolution in free
troposphere and lower stratosphere
Assimilation of AIRS data
Operational running of a Severe Weather
forecasting system
2005-2006
CAS 2001, Annecy
Assimilation of IASI data
Slide 7
ECMWF
Computer configuration – October 2001
CAS 2001, Annecy
Slide 8
ECMWF
PrepIFS
ECMWF tool to prepare forecast and data assimilation
experiments
Uses the operational configuration of the forecasting
system and allows researcher to introduce
modifications to:
input data (including the selection of observations)
the model code
the resolution to be used and many other parameters
Written Java, with a client part that can be installed on
remote machines
Allows registered external users to configure and
submit experiments via the Internet
CAS 2001, Annecy
Slide 9
ECMWF
Major changes to the
computing environment
Desktop systems (procurement completed in 2000)
Decision was taken to replace all proprietary UNIX workstations
with PCs running LINUX over a period of three years
Data Handling System – DHS (procurement in progress)
A scalable system that will be able to support the expected
growth over 6+ years is required
Invitation to Tender for a new system was issued earlier this year
Supercomputer – HPC (procurement in progress)
Fujitsu systems are rented and the contract ends on 31 Dec 2002
Invitation to Tender for a replacement to cover the period
2003-2006 was issued in March this year
CAS 2001, Annecy
Slide 10
ECMWF
DHS procurement
Archive holds currently some 400 TB of data (primary
data) and has been growing by some 60% per annum
Two services need to be supported at ECMWF:
ECFS, a large-scale UNIX-like filesystem for general use
MARS, a customised meteorological archival and retrieval system
Vendors were asked to offer a scalable storage system and
were given the option to offer a replacement for the ECFS
and/or MARS software layer
DHS and HPC procurements were separated because:
Lifetime of the data handling systems tends to be considerably
longer than that of the HPC systems
Allows a simpler HPC procurement not affected by the complexities
associated with the replacement of the archive system
CAS 2001, Annecy
Slide 11
ECMWF
HPC procurement
ECMWF asked for a phased introduction of resources
covering the period 2003-2006, with a parallel run during
the second half of 2002
The specifications allowed for some flexibility, enabling
vendors to adapt their response to their product
development plans. This included the option to propose
a 3-month shift of the service period
The funds available were published
Vendors were required to commit to performance
increases, expressed as factors, over the performance of
the Fujitsu systems installed at ECMWF
Requirements for disk space, I/O and network bandwidth
were expressed as function of these factors
CAS 2001, Annecy
Slide 12
ECMWF
The Benchmark Suite
IFS tests (for the performance commitments)
4D-VAR (T511/255 L60; 2, 4 or 6 copies depending on PHASE)
DETERMINISTIC FORECAST (T799 L90; 2 or 4 copies)
EPS (T399 L60; 50 or 100 copies)
Burton Smith taxonomy:
Size * g >> 2 * O + L
Suitable for both T-type and C-type systems
IFS model runs well on all architectures
4D-Var is very sensitive to communication bandwidth and
has sections on which scalar machines do well
Resolutions representative for the workload planned for
2003-2006 were used
CAS 2001, Annecy
Slide 13
ECMWF
Observations
Vendors were allowed to optimize the codes
However, changes that would affect the readability or
portability were not permitted
Some vendors used a hybrid MPI / OpenMP approach
Some vendors found that such a hybrid approach did not
improve the results obtained by using MPI only
Percentages of peak:
4D-Var scaled not as well the deterministic forecast and the EPS
Scalar machines:
3% to 12%, depending on test/product
Vector machines:
14% to 38%, depending on test/product
Rule of thumb for ECMWF’s codes was confirmed:
~10% for scalar architectures and ~30% for vector architectures
CAS 2001, Annecy
Slide 14
ECMWF
Status of both procurements
The Tender Evaluation Boards have completed their work and
have made recommendations to the ECMWF Director
The Director has awarded both contracts, subject to approval by
ECMWF Council
Documents detailing the respective procurement process and
the proposed solutions have been sent to the technical and
financial committees of the ECMWF Council
These committees will meet in November to consider ECMWF’s
proposals and to make recommendations to Council
Council will meet in December and (hopefully) authorize the
Director to sign the appropriate contracts
CAS 2001, Annecy
Slide 15
ECMWF
Changes over the next 18 months
New
Servers
New
Network
New HPC
system
Linux PCs
New DHS
CAS 2001, Annecy
Slide 16
ECMWF