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NCEP’s Global Forecasting System (GFS) and other Recent

Developments at the NCEP Environmental Modeling Center

Stephen Lord (Director)

and

EMC Staff

2Currently being upgraded again - major changes to allow easier upgrades in future

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Overview

• 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

GFSSpectralSigma

T382/L64 (0-180 h)

T190/L64 (180-364 h)

Global

GFS

Simple CloudModified Arakawa/

Schubert

GFSChou (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– 3 D-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

– 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%

Consistentday-to-dayperformance

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Performance Results – Summer

AC +3%RMS - 8%

Consistentday-to-dayperformance

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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

Black-opr

Red-exp

DeterministicRuns

EnsembleRuns

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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)

Without relocation

With relocation

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Track errors and spreads2004 Atlantic Basin (8/23-10/1)

0

50

100

150

200

250

300

350

400

24h 48h 72h 96h 120h

opr-errors exp-errors opr-spread exp-spread

From Timothy Marchok (GFDL)

Reduced mean track errors and spreads

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Overview

• 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-TB

obs AMSU-A1&A2 NOAA15

A3A5

A2A1

A2A1

currentcurrent

NewNew

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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 dataRO locations

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Input

Data

CDAAC

NESDIS

GTS

NCEP

ECMWF

CWB

UKMO

Canada Met.

JMA

BUFR FilesWMO standard1 file / sounding

Getting COSMIC data to Weather Centers

This system is currently under development by UCAR, NESDIS, & UKMO

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• 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)

New JCSDA SATELLITE SST Retrieval Method:

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Smoother anomalies (less noise)

Smoother anomalies (less noise)

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Daily Analysis Difference

Operational

RTG_SST-HR

Reduced daily noise

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Data Assimilation Status• 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

• Global weather

• NASA-NOAA-DOD JCSDA

• Climate

• Mesoscale weather

• Ocean

• Hurricanes

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Raw Nino3.4 SST Correlation SkillAnnual Mean 1981-2001

0

20

40

60

80

100

1 2 3 4 5

Forecast Lead [ months ]

An

om

aly

Co

rre

lati

on

[ %

]

CFS

ECM

MFR

MPI

UKM

ING

LOD

CER

CA

wrt OIv2 1971-2000 climatology

DE

ME

TE

RNCEP Performance Comparison

Seasonal Forecasts

NCEP CFS

CA (Statistical)

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Overview

• Global weather

• NASA-NOAA-DOD JCSDA

• Climate

• Mesoscale weather

• Ocean

• Hurricanes

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Katrina

Multi-model Consensus

CONU:GFS

UKMONGPSGFDLGFDN

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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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GFS

{

Ensembles

Human forecaster

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Precipitation Forecast Comparisons (Threat & Bias)

Model groups Period Forecast

International (1)* 10/2004 – 9/2005 f24-f48

North American+ 10/2004 – 9/2005 f24-f48

North American 10/2004 – 9/2005 f24

International (2)* 10/2004 – 6/2005 f24-f72

International (2)* 7/2005 – 9/2005 f24-f72

North American 7/2005 – 9/2005 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 season1 October 2004 – 30 June 2005

24 – 72 h Forecasts

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Global Models – Warm season1 July 2005 – 30 September 2005

24 – 72 h Forecasts

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North American Models - Annual1 October 2004 – 30 September 2005

24 – 48 h Forecasts

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North American Models – Warm season1 July 2005 – 30 September 2005

24 -48 h Forecasts

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All operational data available on web without any restrictions for use