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Regional Modeling using MODIS SST composites Prepared for the Science Advisory Committee

Regional Modeling using MODIS SST composites Prepared for the Science Advisory Committee November 21, 2005 Kate LaCasse B. Lapenta, S. Dembek, S. Lazarus, M. Splitt. Motivation: Mesoscale features are often observed along SST gradients Current operational models use the coarse resolution

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Regional Modeling using MODIS SST composites Prepared for the Science Advisory Committee

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  1. Regional Modeling using MODIS SST composites Prepared for the Science Advisory Committee November 21, 2005 Kate LaCasse B. Lapenta, S. Dembek, S. Lazarus, M. Splitt

  2. Motivation: • Mesoscale features are often observed along SST gradients • Current operational models use the coarse resolution (~50 km) RTG SST product • Better specification of the SSTs, especially SST gradients, through the use of a high resolution (1 km) MODIS SST composite, should better resolve the forcing mechanisms which lead to some of the observed features Current Activities: • Operational forecasts over the southeastern US • Simulations in the vicinity of Florida from May 2004 • Hurricane forecasts All modeling is performed using the Weather Research and Forecasting (WRF) prediction system

  3. WRF Operational Forecasts • 12 km resolution with 37 vertical levels • 48h forecasts daily at 00 and 12 UTC • Dynamics and Physics • Eulerian mass core • Dudhia shortwave radiation • RRTM longwave radiation • YSU planetary boundary layer • Noah land surface model • Lin microphysics • Kain-Fritsch cumulus • Initialized with 40km NAM analyses • NAM 3h forecasts used for LBCs • SSTs are replaced with MODIS SSTs • Used by both the NWS Huntsville and Mobile offices within AWIPS

  4. Radar Reflectivity Improved Coastal and Marine Forecasts 3h accumulated precipitation (in) 24h forecast ending 00 UTC August 4, 2005 NAM WRF

  5. ADAS ADAS 24h WRF simulation 3h WRF simulation 21 00 00 • Impact of MODIS SSTs on Mesoscale Weather • Methodology: • 2 km resolution with 51 levels • Physics differences from operational WRF: • No cumulus parameterization • WSM 6-class microphysics scheme • 24h simulations run daily for May 2004 • Parallel runs for both the RTG SSTs and the MODIS SST composites MODIS SST- RTG SST (K) 14 May 2004

  6. Computing Capacity: Project Columbia

  7. METARs Buoys METARs Buoys Bulk Verification of 2m Temperature • Overall there is little difference between 2m temperature forecasts, as expected • Expect to see greater impact of MODIS SSTs locally Average of 15 days from May 2004 # of observations used METARs: ~50,000 Buoys: ~10,000

  8. Net Sensible Heat Flux (Wm-2*10) 1h forecast valid 01 UTC 14 May 2004 MODIS - RTG SST (K) 14 May 2004 MODIS RTG 10m Wind Divergence (s-1*10-4) 1h forecast valid 01 UTC 14 May 2004 MODIS RTG Impact over ocean

  9. Horizontal convective rolls 850 850 800 800 900 850 850 950 900 900 RTG MODIS 1000 950 950 Upward Vertical Motion (ms-1*10-2) 1000 1000 ~100 km 850 900 950 RTG MODIS 1000 ~100 km Wind Divergence (s-1*10-4) 1h forecast valid 01 UTC 14 May 2004 • SST differences of ~1.5 K have a significant impact on the boundary layer

  10. Visible Satellite Image MODIS Validation of MODIS forecast 01 UTC 14 May 2004 10m Wind Divergence (s-1*10-4) • Low level convergence from horizontal convective rolls provides forcing for clouds • Do the MODIS SSTs also impact precipitation?

  11. Convection Along SST Gradient Reflectivity (dBZ) 18h forecast valid at 18 UTC 01 May 2004 MODIS RTG SST Gradient Radar composite

  12. Hurricane Katrina 06 UTC August 29, 2005 • WRF Hurricane Forecasts • In collaboration with Goddard Space Flight Center, run test cases to determine if WRF forecasts are sensitive to SSTs • Domain configured like May 2004 runs • 24 – 48 h forecasts • Initialized with 40 km NAM analyses • NAM 3h forecasts used for LBCs • Parallel forecasts with either RTG SSTs or MODIS SST composite 42h forecast of 3h accumulated precip (in) New Orleans, LA Radar Reflectivity

  13. Initial cases indicate that WRF hurricane forecasts are sensitive to SSTs.

  14. Summary: • Use of MODIS SST composites is currently ongoing in operational WRF forecasts • May 2004 simulations and hurricane forecasts provide the opportunity to determine the impact of MODIS SSTs on regional forecasts • Preliminary work suggests that the WRF model appears to respond appropriately to high-resolution SST data • Greatest impact of MODIS SSTs is seen in the marine boundary layer

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