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Using MM5 to Hindcast Ocean Surface Forcing Fields over the Gulf of Maine and Georges Bank

Using MM5 to Hindcast Ocean Surface Forcing Fields over the Gulf of Maine and Georges Bank. Changsheng Chen – U Mass-Dartmouth Robert Beardsley – WHOI Song Hu – U Mass-Dartmouth Qichun Xu – U Mass-Dartmouth Huichan Lin – U Georgia GB GLOBEC Workshop, November 18, 2003. Outline of Talk.

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Using MM5 to Hindcast Ocean Surface Forcing Fields over the Gulf of Maine and Georges Bank

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  1. Using MM5 to Hindcast Ocean Surface Forcing Fields over the Gulf of Maine and Georges Bank Changsheng Chen – U Mass-Dartmouth Robert Beardsley – WHOI Song Hu – U Mass-Dartmouth Qichun Xu – U Mass-Dartmouth Huichan Lin – U Georgia GB GLOBEC Workshop, November 18, 2003

  2. Outline of Talk • Description of MM5 • MM5 Setup • 1995 Hindcasts • Summary • Next Steps

  3. MM5- 5th generation NCAR/Penn State mesoscale meteorological model • Features: non-hydrostatic, terrain-following, variable domain and spatial resolution, multiple grid nesting, nudging 4-D data assimilation, several PBL modules • Uses NCAR/NCEP or ETA weather model fields as initial and boundary conditions with two-way nesting capability • Integrated for 3 days with 12-hr spin-up • Model output fields used to construct 3-hr time series of surface wind, pressure, Ta, RH, wind stress and heat flux

  4. PBL Models • Models designed to represent turbulent mixing due to vertical eddy diffusion K and free and forced convection in unstable weather conditions. • We considered four: Blackadar, ETA, MRF, Gayno-Seaman

  5. The Gulf of Maine/Georges Bank MM5 Model System NCEP (2.5 degree) or ETA (30 km) Nested Air stations Buoy data Satellite data Land stations Assimilation Regional domain MM5 (resolution: 30 km) Nested Assimilation SST Local buoy data Local domain MM5 (resolution: 10 km) Surface winds, Ta, Pa, RH, wind stress, heat flux, water flux

  6. 80o W 70o W 50o W 60o W 50o N 50o N Local domain 40o N 40o N Regional domain 80o W 70o W 60o W Horizontal Resolution: Regional domain = 30 km; Local domain = 10 km Vertical Resolution: 31-sigma levels Numbers and Labels: Names of weather buoys

  7. 1995 Hindcasts

  8. Simulated Assimilated

  9. Simulated Assimilated

  10. Short-wave Long-wave Latent Sensible

  11. TOGA/COARE (TC2.5) heat flux algorithm (Fairall et al.,1996) • Computes wind stress, Qsen, Qlat using wind speed, Ta, RH, SST • Improved parameterization of surface roughness • Includes wind gustiness (most important at low wind speeds) • More realistic vertical profiles for stable and unstable weather conditions

  12. January 1995

  13. Summary • MM5 with assimilation of buoy wind data and daily SST and modified PBL model can provide a reasonable hindcast wind field and long-wave, sensible, and latent heat flux components in the Gulf of Maine/Georges Bank region (=> adequate for ocean modeling) • Method used to estimate short-wave radiation in MM5 needs improvement (=> need for in situ short-wave flux measurements or remote-sensing approach) • QuikSCAT wind data do not resolve the wind field during frontal passages due to precipitation (=> no substitute forin situ buoy measurements)

  14. Next Steps • Develop better insolation method for MM5 • Convert TC2.5 to new COARE2.6 heat flux algorithm in MM5 PBL module (increased stress, Qsen,Qlat at higher wind speeds, valid to 20 m/s) • Migrate to new NOAA/NCAR Weather Research and Forecasting (WRF) mesoscale model

  15. QuikSCAT Wind Velocity Vectors

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