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NCEP/EMC Data Assimilation Review

NCEP/EMC Data Assimilation Review. S. Lord, J. Derber, R. Treadon, J. Jung, X. Su. Overview. NCEP implementations Global Forecast System (GFS) North American Model (NAM) Current data assimilation development 4-D Var (GMAO). GFS 24 February 2009: Upgrades. Addition of METOP/IASI data

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NCEP/EMC Data Assimilation Review

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  1. NCEP/EMC Data Assimilation Review S. Lord, J. Derber, R. Treadon, J. Jung, X. Su

  2. Overview • NCEP implementations • Global Forecast System (GFS) • North American Model (NAM) • Current data assimilation development • 4-D Var (GMAO)

  3. GFS 24 February 2009: Upgrades • Addition of METOP/IASI data • Improved atmospheric analyses, especially in S.H. (J. Derber, J. Jung) • Variational Quality Control • Improved quality control of observations • Eliminate need for OIQC step • Change in land/snow/ice skin temperature variance • Improved use of near surface radiance observations • New Background error covariances • Consistency with current version of system. Improved upper atmosphere • Reduce number of AIRS water vapor channels • Improved convergence and improved analysis (J. Jung) JCSDA

  4. GFS Upgrades (cont) • New version and coefficients for CRTM • Improved simulation of radiance observations (Vandelst, Han, Liu, …) • Modification of height assignment for height based wind observations • Improved use of these observations • Modification of surface land use file • Removes a few permanent (~12) glacial points to improve surface temperature forecasts • Situation Dependent Background Variances • Improve fit to observations in areas of active weather

  5. IASI Data Coverage

  6. GFS Implementation Results NH AC NH RMS 95% Sig. SH AC SH RMS

  7. NAM 16 December 2008: Upgrades • Partial cycling • Use GDAS forecast for background at T-12 h for NAM data assimilation (W. Wu) • Upgrade to CRTM • Improved behavior at model top (2 hPa) • Includes METOP2 data (D. Keyser) • AMSU • HIRS JCSDA

  8. Development Projects • Improved CRTM (NESDIS-JCSDA) • Cloud observations (NESDIS-JCSDA) • Radar radial velocities and reflectivity (NSSL, FAA) • Hurricane analysis special obs (radial velocities, etc., HFIP) • Additional analysis variables (constituents, aerosols, etc., AQ Program, NASA) • Situation dependent anisotropic background errors (including hurricane) • 4D-var development (GMAO, GOES-R) • Obs sensitivity (GMAO)

  9. Next planned GFS Implementation Fall 2009 • Major components • Include • NOAA-19 AMSU-A/B, HIRS • RARS 1b data • NOAA-18 SBUV/2* and OMI • Use of Hurricane central pressure estimate • Improved use of GPS RO observations • Refractivity forward operator • Allow more observations, in particular in the tropical latitudes, due to better QC checks for COSMIC data • Re-tuned observation errors (better and smoother ratios) • Better QC procedures Metop/GRAS, GRACE-A and CHAMP • Merger with GMAO 4Dvar/sensitivity version * Possibly earlier

  10. GSI 4-D Var Status at NCEP/EMC • Infrastructure within GSI comes from collaboration with GMAO (merger completed) • Methodology follows Met Office strategy • Uses perturbation model • Can be used for GFS, NAM, RTMA and hurricane systems • Perturbation model developed and working • Tangent linear and adjoint models being developed • Completion anticipated within next 2 months • Extensive code and parallel testing over coming year • Pre-operational global testing over following ½ year • Inclusion of simplified physics will also be developed in parallel to dynamics • Goal is “hybrid” system (4-D Var with ensemble input) • Implementation dependent on operational computing resources

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