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WRF and the coastal marine environment

WRF and the coastal marine environment. Kate LaCasse SOO/SPoRT Workshop 11 July 2006. 36 km domain. 12 km domain. Operational SPoRT WRF. 12 km SE US nest 48 h forecasts initialized at 00 and 12 UTC Complements NAM output because of different dynamics, physics, and observations

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WRF and the coastal marine environment

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  1. WRF and the coastalmarine environment Kate LaCasse SOO/SPoRT Workshop 11 July 2006

  2. 36 km domain 12 km domain Operational SPoRT WRF • 12 km SE US nest • 48 h forecasts initialized at 00 and 12 UTC • Complements NAM output because of different dynamics, physics, and observations • Available within AWIPS at Huntsville, Mobile, and Morristown WFOs

  3. cool SSTs warm SSTs SPoRT Center coastal modeling • Determine the impact of NASA observations • Conduct case studies based on feedback from the NWS offices about the operational SPoRT WRF • Focus on the marine boundary layer, sea breeze circulation, and associated clouds and precipitation

  4. MODIS SST RTG SST SST products used operationally Real-Time Global SST: 0.5 degree spatial resolution Used in NAM, GFS, and RUC MODIS SST composite: 1 km resolution Used in SPoRT WRF • MODIS SST composite has more structure, especially east of Florida

  5. Experiment design • 2 km horizontal resolution with 51 levels • 24 h simulations run daily for May 2004 • Parallel runs with either the RTG SSTs or the MODIS SST composite SST (K) MODIS RTG 40 km Expect that differences between the simulations will be greatest near the SST gradient

  6. Results • Compared to the control run, the simulations with MODIS SST composites over the Gulf Stream: • Increased sensible and latent heat fluxes • Higher PBL height • Increased up to 10% the 10 m wind speed • Changes in wind speed led to regions of enhanced convergence/divergence 10 m wind speed difference (MODIS – RTG; 10-1ms-1) Nighttime, westerly cases

  7. Case Study: 25 March 2006 • Mobile WFO provided feedback about a poor forecast by the SPoRT WRF as well as the NAM and GFS • Case synopsis: • Runoff from heavy precipitation earlier in the week cooled SSTs near the Alabama coast • Models forecasted cool temperatures with northerly flow for the daytime on 25 March 2006 • Warmer temperatures with southerly flow was observed, in conjunction with a sea breeze circulation

  8. 61ºF 69ºF SST’s up to 4.5K (8.1ºF) colder than on March 22 Review of SPoRT WRF and MODIS SSTs • On this day, SPoRT WRF ran with the RTG SSTs instead of the MODIS SSTs • Cool MODIS SSTs were not adequately captured with the current compositing technique 22 March 2006 MODIS SST Composite 25 March 2006 Enhanced Composite

  9. OPERATIONAL WRF RESOLUTION TEST MODIS INITIALIZATION Determine sensitivity to model resolution and SSTs • Possible ways to improve forecast: • Include a higher resolution (2.4 km) nest • Make an improved MODIS SST composite, which retains more recent MODIS SST data • Re-run forecasts initialized at both 00 and 12 UTC 25 March 2006 SSTs valid 25 March 2006

  10. OPERATIONAL WRF RESOLUTION TEST MODIS INITIALIZATION Results • Higher resolution runs forecasted a slightly further inland progression of the sea breeze • Addition of MODIS SSTs improved forecast in northern Mobile Bay 10 m wind (ms-1) 9 h forecast valid 21 UTC 25 March 2006

  11. Summary • The SPoRT Center transitions new products, such as the MODIS SST composite, into the SPoRT WRF • Are more accurate initial conditions, through the use of additional observations, required to improve local modeling? • What resolution does WRF need to adequately resolve coastal processes?

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