NCEP’s Global Forecasting
System (GFS) and other Recent
Developments at the NCEP
Environmental Modeling Center
Stephen Lord (Director)
and
EMC Staff
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Currently being upgraded again - major changes to allow easier upgrades in future
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Overview
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Global weather
NASA-NOAA-DOD JCSDA
Climate
Mesoscale weather
Ocean
Hurricanes
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Global Weather
• Global Forecast System (GFS)
• Global Ensemble Forecast System (GEFS)
– Extended T126 horizontal resolution after 180 hours
– Initial perturbations (breeding cycle):
• Fixed bugs for calculating re-scaling factors
• Use 6-h breeding instead of 24-h breeding
• Adjust mask to tune initial perturbation
– Tropical storm relocation
• Add TS relocation scheme to ensemble initial perturbation
(5% of total storm size).
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Global Forecast System (GFS) model Configuration
GFS
Spectral
Sigma
T382/L64
(0-180 h)
T190/L64
(180-364 h)
Global
GFS
Simple Cloud
Modified Arakawa/
Schubert
GFS
Chou (SW), GFDL (LW)
Ferrier
JCSDA SST
NESDIS/USAF
NOAH Land Model
6-Layer Model
Burk and Thompson
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GFS - List of Upgrades
• Global Forecasgt System (GFS)
– Increase resolution from T254 (55 km) to T382 (35 km)
• Old: T254/L64 (0-84 h) T170/L42 (84-180h, T126/L28 to 384h
• New: T382/L64 (0-180 h) T190/L64 (180-364 h)
– Modified vertical diffusion
– Enhanced mountain blocking
– New sea ice model
• Fractional sea ice & leads
• Impacts surface fluxes
– New code structure
• Increased computational efficiency
• ESMF compatible superstructure
• “Hybrid (sigma-pressure) ready”
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GFS - List of Upgrades (cont)
• Model (cont)
– Upgrade to Noah Land Surface Model
• 2-4 soil layers
• Reduction of early bias in snow pack depletion
• Improved treatment of
– Frozen soil
– Ground heat flux
– Energy and water balance at surface
• Reformulated infiltration and runoff functions
• Upgraded vegetation fraction (NESDIS)
• Improved, plug-compatible, code structure
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GFS - List of Upgrades (cont)
• Analysis
– 3D-VAR
– Increase resolution to T382
– Surface emissivity model for snow and ice (JCSDA)
• 3 X data used in SH polar latitudes
• 1.3 X in NH polar latitudes
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AQUA AIRS and AMSU-A (new data)
AIRS (new data)
Upgraded thinning algorithm for radiances
QC algorithm for clouds
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Performance Results - Winter
AC +2%
RMS - 8%
Consistent
day-to-day
performance
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Performance Results –
Summer
AC +3%
RMS - 8%
Consistent
day-to-day
performance
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Global Weather
• Global Forecast System (GFS)
• Global Ensemble Forecast System (GEFS)
– Extended T126 horizontal resolution after 180 hours
– Initial perturbations (breeding cycle):
• Fixed bugs for calculating re-scaling factors
• Use 6-h breeding instead of 24-h breeding
• Adjust mask to tune initial perturbation
– Tropical storm relocation
• Add TS relocation scheme to ensemble initial perturbation
(5% of total storm size).
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Increasing spread for
week-two forecast
Deterministic
Runs
Ensemble
Runs
Black-opr
Red-exp
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SH RMS
and spread
Improved outlier
SH ROC
SH RPSS
Improved skill for short,
extended-range forecast
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Hurricane Track Plots (case 1)
Frances (08/28)
With relocation
Without relocation
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Track errors and spreads
2004 Atlantic Basin (8/23-10/1)
opr-errors
400
exp-errors
opr-spread
exp-spread
From Timothy Marchok (GFDL)
350
300
250
200
150
100
Reduced mean track
errors and spreads
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0
24h
48h
72h
96h
120h
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Overview
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Global weather
NASA-NOAA-DOD JCSDA
Climate
Mesoscale weather
Ocean
Hurricanes
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NCEP Data Assimilation system is moving form
Spectral Statistical Interpolation (SSI)
to
Grid-point Statistical Interpolation (GSI)
Continuing with 3D-VAR for now,
due to product delivery timetable constraints
NCEP Global Forecast System must begin delivering products
to users within
about 3 hours of radiosonde observations
Also doing tests with alternative forms of 4D-VAR
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Monthly Mean TBges-TBobs
AMSU-A1&A2 NOAA15
A1
A2
A3
A5
New
A1
A2
current
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GPSRO Data Assimilation Development (L. Cucurull)
• Current and short-term work:
– Implementation of the local Bending Angle Forward
Operator (BAFO) in the GSI.
– Examination of representativeness error.
• If realistic errors (for refractivity and bending angle
along the vertical) are not available in time for
impact studies, we will use simulated errors.
– Compare impact studies between BAFO and RFO
and select the Forward Operator for COSMIC.
– Develop (real-time) Monitoring System (O-B) for
calibrating/testing the RO
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Assimilation of RO + other data
RO locations
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Getting COSMIC data to Weather Centers
NCEP
I
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p
u
t
D
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D
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A
C
BUFR Files
WMO standard
1 file / sounding
N
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S
D
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ECMWF
GTS
CWB
UKMO
JMA
Canada Met.
This system is currently under development by UCAR, NESDIS, & UKMO
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New JCSDA SATELLITE SST Retrieval
Method:
• Developed as alternative SST retrieval method
– based on a physical retrieval (variational) algorithm which runs
within the structure of the GDAS (Derber and Xu Li).
– Cost function minimizes the increment between;
• Observed radiances and simulated radiances, and
• Analyzed SST and its first guess
• Requires radiative transfer model to simulate Brightness
Temperatures for each channel using
– SST first guess (previous analysis)
– Air Temperature (GDAS analysis)
– Water vapor mixing ratio (GDAS analysis)
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Smoother anomalies
(less noise)
Smoother anomalies
(less noise)
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Daily Analysis Difference
RTG_SST-HR
Operational
Reduced daily noise
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Data Assimilation Status
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Gridpoint Statistical Analysis (GSI)
– NCEP’s next generation system
• Evolutionary combination of the global SSI analysis system and the regional ETA
3DVAR
• Application to both global and regional analysis
• Strong heritage to satellite, radar, profiler, surface data
– Background error defined in grid space instead of spectral space
• Allows use of situation dependent background errors
• Will accept ensemble information
– Improved balance condition
• Adiabatic dynamics model
• Capable of simplified 4-D Var
– Improved and modernized code
• F90/95 structures and utilities
• Increased scalability of code
• Efficiency
– Redesigned data distribution
– Some OpenMP
• Better documentation
• Less dependency on IBM
– Community support intended but not resourced
• Currently 15 registered groups (46 users) using GSI code
• NASA/GMAO major group using code and to date they have provided the most
updates from external users
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Overview
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•
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•
Global weather
NASA-NOAA-DOD JCSDA
Climate
Mesoscale weather
Ocean
Hurricanes
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NCEP Performance Comparison
Seasonal Forecasts
Raw Nino3.4 SST Correlation Skill
Annual Mean 1981-2001
NCEP CFS
wrt OIv2 1971-2000 climatology
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CA (Statistical)
CFS
ECM
MFR
DEMETER
Anomaly Correlation [ % ]
80
60
MPI
UKM
ING
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LOD
CER
CA
20
0
1
2
3
Forecast Lead [ months ]
4
5
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Overview
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Global weather
NASA-NOAA-DOD JCSDA
Climate
Mesoscale weather
Ocean
Hurricanes
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Katrina
Multi-model Consensus
CONU:
GFS
UKMO
NGPS
GFDL
GFDN
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Examples of GFS performance
Compared with:
1 - Other Global models
2 - NCEP’s North American Mesoscale models
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Human forecaster
{
GFS
Ensembles
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Precipitation Forecast
Comparisons (Threat & Bias)
Model groups
International (1)*
Period
10/2004 – 9/2005
Forecast
f24-f48
North American+
10/2004 – 9/2005
f24-f48
North American
International (2)*
International (2)*
North American
10/2004 – 9/2005
10/2004 – 6/2005
7/2005 – 9/2005
7/2005 – 9/2005
f24
f24-f72
f24-f72
f24-f48
* International global (1): DWD, ECMWF, JMA, UK, USA
International global (2): CMC, DWD, ECMWF, JMA, USA
+ North American: USA (global), USA (NAM), CMC (global), CMC (regional)
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Precipitation Verification at NCEP/EMC
Precipitation forecasts from various operational and parallel (experimental)
models are verified over ConUS and its 14 sub-regions:
• Daily (12Z-12Z) verification against daily gauge analysis (7,000-8,000 gauges)
• 3-hourly verification against NCEP Stage II multi-sensor hourly analysis
• Verification for international models for 24 h accumulated amounts over
ConUS domain
Statistics on the number of
forecast/correctly forecast/observed
forecast points (FHO) are collected for
various precipitation thresholds. Dozens
of scores can be computed from the FHO
database, e.g. equitable threat, bias,
probability of detection, odds ratio.
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Global Models – Annual
1 October 2004 – 30 September 2005
24 – 48 h Forecasts
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Global Models – Cold season
1 October 2004 – 30 June 2005
24 – 72 h Forecasts
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Global Models – Warm season
1 July 2005 – 30 September 2005
24 – 72 h Forecasts
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North American Models - Annual
1 October 2004 – 30 September 2005
24 – 48 h Forecasts
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North American Models – Warm season
1 July 2005 – 30 September 2005
24 -48 h Forecasts
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All operational data available on web without any restrictions for use
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