The Global Ocean Data Assimilation System (GODAS) at NCEP: Introducing new data sets
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The Global Ocean Data Assimilation System (GODAS) at NCEP: Introducing new data sets David Behringer Environmental Modeling Center, NCEP/NOAA Yan Xue Climate Prediction Center, NCEP/NOAA Office of Climate Observation (OCO) Annual System Review Silver Spring, Maryland, April 25-27, 2005.

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The Global Ocean Data Assimilation System (GODAS) at NCEP: Introducing new data sets

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The global ocean data assimilation system godas at ncep introducing new data sets

The Global Ocean Data Assimilation System (GODAS) at NCEP: Introducing new data sets

David BehringerEnvironmental Modeling Center, NCEP/NOAAYan XueClimate Prediction Center, NCEP/NOAAOffice of Climate Observation (OCO) Annual System Review

Silver Spring, Maryland, April 25-27, 2005


The global ocean data assimilation system godas at ncep introducing new data sets

Outline

  • The standard operational GODAS

  • Assimilating satellite altimetry

  • Assimilating Argo salinity profiles

  • The effect of a changing ocean observing system on

  • CFS S/I forecasts


The global ocean data assimilation system godas at ncep introducing new data sets

Seasonal to Interannual Forecasting at NCEP

Ocean Initial Conditions

Altimeter

Argo

Seasonal Forecasts

for North America

with Climate

Atmosphere GCM

SST

XBT

TAO

Coupled Ocean

Atmosphere Forecast

System (CFS03)

CCA, OCN

MR, ENSO

Global Ocean

Data Assimilation

System (GODAS)

IRI

SST Anomaly

Surface Temperature

& Rainfall Anomalies

Stress

Heat Fluxes

CCA, CA

Markov

IRI

Forecasters

E-P

Official Probabilistic

Surface Temperature

& Rainfall Forecasts

Scatterometer

Official SST Forecast


The global ocean data assimilation system godas at ncep introducing new data sets

  • GODAS (MOM V.3)

  • Operational since September 2003

  • Grid:

    • Quasi-global, 40 vertical levels.

  • Physics:

    • KPP boundary layer mixing scheme,

    • free surface.

  • Forcing:

    • Wind stress, heat flux, E-P from

    • Reanalysis 2 (R2), surface salinity

    • relaxed to Levitus monthly SSS

    • climatology.

  • Assimilation method:

    • 3D VAR, analyzes temperature and

    • salinity, error covariance varies

    • geographically and temporally.

  • Assimilation data:

    • Temperature profile data from XBTs,

    • profiling floats (Argo), moorings

    • (TAO), synthetic salinity constructed

    • from temperature and local Levitus

    • T-S climatology.

  • CFS03

    Operational since August 2004

    Atmosphere:

    T62/64-layer version of the current

    NCEP atmospheric Global Forecast

    System (GFS) with the same

    configuration as used in R2

    Ocean:

    GFDL Modular Ocean Model

    (MOM V. 3) with the same

    configuration as used in GODAS

    Coupling:

    Direct coupling with no flux correction,

    accomplished daily


    The global ocean data assimilation system godas at ncep introducing new data sets

    GODAS

    • Assimilation data sets

      Standard temperature and synthetic salinity

      Satellite altimetry data

      Argo salinity


    The global ocean data assimilation system godas at ncep introducing new data sets

    Ocean Observations Used in NCEP S/I Forecasting


    The global ocean data assimilation system godas at ncep introducing new data sets

    GODAS

    • Assimilation data sets

      Standard temperature and synthetic salinity

      Satellite altimetry data

      Argo salinity


    The global ocean data assimilation system godas at ncep introducing new data sets

    Assimilation of altimetry data

    • 2 Data sets

      TOPEX / Jason-1, 10-day period

      ERS-2 / Envisat, 35-day period

      Both acquired from AVISO through John Lillibridge (NESDIS)

    • 4 Experiments

      GTSE - assimilates temperature, synthetic salinity

      and TOPEX / Jason-1, 1993-2003

      GTSEn - assimilates temperature, synthetic salinity

      and ERS-2 / Envisat, 1996-2003

      GTS - assimilates temperature and synthetic salinity

      GSIM - control, no assimilation


    The global ocean data assimilation system godas at ncep introducing new data sets

    12 / 28 / 1997 - 1 / 07 / 1998

    12 / 14 / 1997 - 1 / 18 / 1998


    The global ocean data assimilation system godas at ncep introducing new data sets

    RMS COR

    SIM 9.96 0.54

    GTS 4.88 0.88

    GTSE 3.27 0.93

    GTSEn 2.87 0.96

    SIM 6.65 0.54

    GTS 4.50 0.82

    GTSE 3.22 0.90

    GTSEn 3.42 0.90

    SIM 4.85 0.80

    GTS 2.94 0.93

    GTSE 2.22 0.96

    GTSEn 2.30 0.97


    The global ocean data assimilation system godas at ncep introducing new data sets

    RMS COR

    SIM 5.06 0.85

    GTS 5.30 0.81

    GTSE 4.38 0.88

    GTSEn 4.02 0.93

    SIM 5.35 0.81

    GTS 3.58 0.91

    GTSE 3.07 0.94

    GTSEn 3.17 0.96

    SIM 4.38 0.88

    GTS 2.73 0.96

    GTSE 2.10 0.97

    GTSEn 1.97 0.98


    The global ocean data assimilation system godas at ncep introducing new data sets

    GODAS

    • Assimilation data sets

      Standard temperature and synthetic salinity

      Satellite altimetry data

      Argo salinity


    The global ocean data assimilation system godas at ncep introducing new data sets

    Assimilation of Argo salinity

    • Each temperature profile (XBT, mooring, Argo) is paired with a salinity profile

    • XBT and mooring profiles are paired with synthetic salinity profiles

    • Most Argo profiles are paired with observed salinity profiles

    • Synthetic salinity profiles are assigned larger errors based on the statistics of the synthetic - observed profile differences

    • The experiment runs from the beginning of 2000 through the end of 2004


    The global ocean data assimilation system godas at ncep introducing new data sets

    Operational SI prediction

    • GODAS runs daily producing a daily mean file and a restart file that lag the current date by 8 days.

    • CFS runs 2x daily, initialized by the GODAS restart file and the R2 atmospheric analysis.

    • Each forecast extends out to 9 months.

    • The ensemble forecast is built from the forecasts run on 20 consecutive days for a total of 40 members.


    The global ocean data assimilation system godas at ncep introducing new data sets

    Courtesy of

    Dr Peitao Peng


    The global ocean data assimilation system godas at ncep introducing new data sets

    Courtesy of Dr Peitao Peng


    The global ocean data assimilation system godas at ncep introducing new data sets

    Summary

    • Assimilation of new data sets

    • Altimetry assimilation leads to general improvement

      in GODAS sea level. It’s impact on CFS

      predictions is to be determined.

    • Assimilation of Argo salinity leads to a general

      improvement in GODAS salinity. There is less

      improvement in western tropical Pacific and

      near river outflows.

    • S/I forecasting

    • The CFS S/I forecasts show higher skill in the 1990s

      than in the 1980s.

    • The likely cause is a shift in the GODAS climatology

      that in turn is due changes in the assimilation data set.


    The global ocean data assimilation system godas at ncep introducing new data sets

    Data Availability on the Internet

    • GODAS Analyses

    • Operational GODAS fields (5-day and monthly ave)

      sea surface height

      surface temperature and salinity

      surface isothermal and mixed layer depths

      heat content of upper 300 meters

      temperature, salinity and currents at 40 levels

      surface forcing (wind-stress, heat flux, E-P)

    • Reanalysis, 5-day averages, 1979-present

    • Operational, weekly, rotating archive,

      ftp://ftpprd.ncep.noaa.gov:cmb/Products/G3R2TSo


    The global ocean data assimilation system godas at ncep introducing new data sets

    The End


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