Review of Ocean Data Assimilation and Forecasting at NCEP/EMC

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Review of Ocean Data Assimilation and Forecasting
at NCEP/EMC

• S. Lord, D. Behringer,
• H-L Pan, H. Tolman

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Overview

• GODAS and operational CFS
• CFS Reanalysis (and Reforecast) project
• Ocean observations for climate and real-time
  applications

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Seasonal to Interannual Prediction at
NCEP Operational System since August 2004
Ocean Model MOMv3 quasi-global 1ox1o (1/3o in
tropics) 40 levels
Climate Forecast System (CFS)
Atmospheric Model GFS (2003) T62 64 levels
GODAS (2003) 3DVAR XBT TAO Triton Pirata Argo Sali
nity (syn.) TOPEX/Jason-1
Reanalysis-2 3DVAR T62L28 OIv2 SST Levitas SSS
clim.
1. Ocean reanalysis (1980-present) provides
initial conditions for retrospective CFS
forecasts used for calibration and research
2. Stand-alone version with a 14-day lag updated
routinely
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Number of Temperature Observations per Month as a
Function of Depth
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GODAS access CPC site

• Pentad and Monthly data products
• 1979-present
• Access to current and archived Monthly Ocean
  Briefings

http//www.cpc.ncep.noaa.gov/products/GODAS/
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GODAS access - NOMADS

• Pentad and Monthly data
• Interactive plotting
• ftp, http full data file download
• ftp2u partial data download
• DODS

http//cfs.ncep.noaa.gov/ncep_data/
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NCEP CFSRR
Climate Forecast System Global Reanalysis and
Seasonal Reforecast Project(1979-2009)
Suru Saha and Hua-Lu Pan, EMC/NCEP With Input
from Stephen Lord, Mark Iredell, Shrinivas
Moorthi, David Behringer, Ken Mitchell, Bob
Kistler, Jack Woollen, Huug van den Dool,
Catherine Thiaw and others
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CFSRR Purpose

• Provide the best, consistent historical analysis
  for
• CFS reforecasts
• Upgraded CFS to be implemented in NCEP operations
  (2010)
• Provide state-of-the-science Reanalysis for the
  Satellite Era (1979-present)
• Address calibration and statistical applications
  for daily and monthly forecasts
• Provide basis for a future coupled
  atmosphere-ocean-seaice-land forecast system
  running operationally at NCEP (1 day to 1 year)

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CFSRR Components

• Reanalysis
• 31-year period (1979-2009 and continued in NCEP
  ops)
• Atmosphere
• Ocean
• Land
• Seaice
• Coupled system (A-O-L-S) provides background for
  analysis
• Produces consistent initial conditions for
  climate and weather forecasts
• Reforecast
• 28-year period (1982-2009 and continued in NCEP
  ops )
• Provides stable calibration and skill estimates
  for new operational seasonal system
• Includes upgrades for A-O-L-S developed since CFS
  originally implemented in 2004
• Upgrades developed and tested for both climate
  and weather prediction
• Unified weather-climate strategy (1 day to 1
  year)

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Component Upgrades
Component Ops CFS 2010 CFS
Atmosphere 1995 (R2) model 200 km/28 sigma levels 2008 model (upgrades to all physics) 38 km/64 sigma-pressure levels Enthalpy-based thermodynamics
R2 analysis Satellite retrievals GSI with simplified 4d-var (FOTO) Radiances with bias-corrected spinup
Ocean MOM-3 60N 65 S 1/3 x 1 deg. MOM-4 Global domain ¼ x ½ deg. Coupled sea ice forecast model
Ocean data assim. 750 m depth 2000 m
Land No separate land property analysis Global Land Data Assim. Sys (GLDAS) driven by observed precipitation
1995 land model (2 levels) 2008 Noah model
Sea ice Daily analysis Daily hires analysis
Coupling None Fully coupled background forecast (same as free forecast)
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• CFSRR Production Configuration
• Covers 31 years (1979-2009) 25 overlap months
• 6 Simultaneous Streams
• Jan 1979 Dec 1985 7 years
• Nov 1985 Feb 1989 3 years
• Jan 1989 Feb 1994 5 years
• Jan 1994 Dec 1998 5 years
• Apr 1998 Dec 2004 6 years
• Apr 2004 Dec 2009 5 years
• Overlap months are for ocean and land spin ups
• Satellite bias correction spinup for each
  instrument (3 months)

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CFSRR at NCEP
Climate Forecast System
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ONE DAY OF REANALYSIS
12Z GSI
18Z GSI
0Z GSI
6Z GSI
0Z GLDAS
12Z GODAS
18Z GODAS
0Z GODAS
6Z GODAS
9-hr coupled T382L64 forecast guess (GFS MOM4
Noah)
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Assimilating Argo Salinity
Comparison with independent ADCP currents.
ADCP GODAS GODAS-A/S
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2009 GODAS Activities

• Complete CFSRR
• Evaluate ODA results
• Add ARGO salinity
• Improve climatological T-S relationships and
  synthetic salinity formulation
• ENVISAT data?
• Improve use of surface observations
• Vertical correlations (mixed layer)
• Situation-dependent error covariances (recursive
  filter formulation)
• Investigate advanced ODA techniques
• Experimental Ensemble Data Assimilation system
  (with GFDL)
• Reduced Kalman filtering (with JPL)
• Improved observation representativeness errors
  (with OSU-JCSDA)

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Observations
NASA-NOAA-DOD JCSDA AMSR, GOES JASON,
WindSat, QuikSCAT, MODIS Advanced ODA Techniques
Satellite (AVHRR, JASON, QuikSCAT)
In situ (ARGO, Buoys, Ships)
Data Cutoff
CFS 2 week data cutoff
RTOFS 24 hour data cutoff
OCEAN DATA ASSIMILATION
RTOFS-GODAS
CFS-GODAS
Shared history, coding, and data processing
CLIMATE FORECAST
OCEAN FORECAST
OPNL OCEAN FORECASTS Climate Forecast
System Real-Time Ocean Forecast System
HYCOM
MOM-3 ? MOM-4
http//cfs.ncep.noaa.gov/
http//polar.ncep.noaa.gov/ofs/
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Real Time Ocean Forecast System (RTOFS) A high
resolution operational ocean forecast system for
the Atlantic
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Data assimilation Algorithms

• Overall employ 3DVar 2D (along model
  layers) x 1D (vertical).
• 2D assumes Gaussian isotropic, inhomogeneous
  covariance matrix, recursive filtering method
  (Jim Purser).
• 1D vertical covariance matrix
• Constructed from coarser resolution simulations
• SST extended to model defined mixed layer.
• SSH lifting/lowering main pycnocline.
• TS profile lifting/lowering below the last
  observed layer.

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Data assimilation Observations

• SST remotely sensed AVHRR, GOES
• (in situ for evaluation)
• Data collection window 48 hours
• SSH remotely sensed JASON, GFO, ENVISAT
• Data collection window 10 days
• TS profiles ARGO, CTD, XCTD, moorings.
• Data collection window 48 hours

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RTOFS(Atlantic)Daily Products

• Once daily (issued at 04Z)
• Nowcast 1day
• Forecast 5 days
• Grib files for nowcast and forecast
• Hourly surface T,S,U,V, SSH, barotropic velocity,
  mixed layer depth
• Hourly interpolated fields on a regular lat-lon
  grid.
• Daily T,S,U,V,W, SSH for 40 depths and for 26
  layers
• Product distribution
• NCO servers (ftpprd)
• NOMADS sub-setting (full data server functions)
• MMAB Web server (ftp, graphics)
• NODC deep archives

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Long Term Strategy

• Implement coupled CFS system for daily global
  weather prediction
• Diurnal SST prediction
• Coupled weather resolution forecasts to 35 days
• Expand RTOFS to global domain
• Navy collaboration
• Merge GODAS and RTOFS ODA capabilities (separate
  models)
• Merge CFS/GFS ocean and RTOFS ocean capabilities
  (multi-model ensemble based system)
• Gradually add ecosystem forecast capability

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ThanksQuestions?
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Dynamical Model HYCOM

• Primitive equation with free surface.
• State variables Temperature, Salinity, Velocity,
  Sea surface elevation.
• Vertical mixing and vertical viscosity GISS

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Dynamical Model configuration

• Horizontal grid orthogonal telescopic, dx/dy1
• Bathymetry ETOPO2 (NGDC)
• Coastal boundary blend of bathymetry and
  coastline datasets (NGDC)
• Surface forcing GDAS/GFS (NCEP)
• River outflow/runoff blend of observations (US
  rivers USGS) and climatology (RIVDIS)
• Initialization T,S from blended regional
  coastal climatologies (Gulf of Maine, Mid and
  South Atlantic Bights, Gulf of Mexico) and
  HYDROBASE
• Boundary data sea surface elevations and
  barotropic velocities from climatology (for low
  frequency) and tidal model (TPX06) (for high
  frequency)
• Body Tides eight tidal constituents