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Very high resolution numerical weather prediction of wind shear event in the complex terrain around Juneau Alaska. Don Morton 1 , Delia Arnold 2,3 , Irene Schicker 2 , Carl Dierking 4 , Kayla Harrison 1 1 Arctic Region Supercomputing Center, University of Alaska Fairbanks, Fairbanks, Alaska USA

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  1. Very high resolution numerical weather prediction of wind shear event in the complex terrain around Juneau Alaska Don Morton1, Delia Arnold2,3, Irene Schicker2, Carl Dierking4, Kayla Harrison11Arctic Region Supercomputing Center, University of Alaska Fairbanks, Fairbanks, Alaska USA 2Institute of Meteorology, University of Natural Resources and Life Sciences, Vienna, Austria 3Institute of Energy Technologies, Technical University of Catalonia, Barcelona, Spain 4Juneau Weather Forecast Office, National Oceanic and Atmospheric Administration / National Weather Service, Juneau, Alaska, USA

  2. Outline • Aviation operations at Juneau • Attempt to simulate past wind event • Problems • Future

  3. IFR Ops in Juneau, Alaska Runway 08

  4. IFR Ops in Juneau, Alaska Turn right as soon as practical Runway 08

  5. IFR Ops in Juneau, Alaska Under strong wind conditions characterized by post-frontal topographically enhanced wind shear, aircraft following these procedures may encounter turbulence or wind shear classified as severe.  In January 1993, a Boeing 737 aircraft at a 30-degree bank encountered extreme crosswinds resulting in departure from controlled flight, with successful recovery occurring within 50 meters of the ground. Turn right as soon as practical Runway 08

  6. Juneau Airport Wind System (JAWS) • Intended to warn of imminent wind shear conditions • Anemometers – Single point wind velocity and temperature, average over 1-minute intervals • Profilers – Vertical wind profile, average over 10-minute intervals Courtesy Research Applications Laboratory, NCAR

  7. A First Modeling Effort • Wind shear event, 18 Dec 2009 • Compared • AK-NAM and ECMWF initialisations • Different parameterisations • 9 / 3 / 1 / 0.333 km nests • NED2s terrain for high resolution

  8. Preliminary Results 1km • Signs of promise, with timing of wind shift improving with higher resolution 333m

  9. Preliminary Results 1km • Though not consistent, signs of promise, with Mount Roberts wind speed improving with higher resolution • Inspired by 333m success, tried to do this at 111m, but couldn’t replicate the previous case!! What happened?!?! 333m

  10. Moving Ahead • Runingthe simulation again at 9 / 3 / 1 / 0.333 and 0.111 km resolution (75 vertical levels) • Had hoped to try a 55.5 m resolution, Large Eddy Simulation • Topography • GTOPO (default WRF, terrain only goes down to 30s) • NED 2s • SRTM 3s • Namelist – Lin microphysics, rrtm/Dudhia radiation, MYNN sfclay_physics, Noah LSM, MYNN pbl. Also, used epssm time off-centering for vertical sound waves

  11. Topography in Nest 5 (111m) GTOPO 30s NED 2s SRTM 3s NED minus SRTM

  12. Topography in Nest 4 (333m) NED 2s NED minus SRTM

  13. 2D 10-meter wind (4h10m) Gtopo 30s NED 2s SRTM 3s

  14. 2D 10-meter wind (16h40m) Gtopo 30s NED 2s SRTM 3s

  15. Verification • For each station, use the lat/lon to extract WRF forecast winds at the nearest grid point • We focus on Mount Roberts and Runway Center. • Getting the lat/lon matching to the correct grid point proves to be problematic Courtesy Research Applications Laboratory, NCAR

  16. Mount Roberts 10m Wd Time Series Nest 5 Gtopo 30s NED 2s SRTM 3s

  17. Mount Roberts 10m Wv Time Series Nest 5 Gtopo 30s NED 2s SRTM 3s

  18. Runway Center 10m Wd Time Series Nest 5 Gtopo 30s NED 2s SRTM 3s

  19. Runway Center 10m Wv Time Series Nest 5 Gtopo 30s NED 2s SRTM 3s

  20. Mount Roberts ML0 versus 10m Wv Time Series Nest 5, NED2s 10m AGL Model level 0 - 26 m AGL

  21. Shifted Topographies? At 111m resolution, NED2s is shifted by about 300m when ingested to WPS Verified in several different ways Have not completely ruled out operator error! Graphic produced with WTOOLS

  22. Simpler case of shifted topography – Coghlan Island

  23. Simpler case of shifted topography – Coghlan Island

  24. Effects of Shifted Topography

  25. Station Elevations Mount Roberts actual elevation: 537m Runway Center actual elevation: 10m

  26. Effects of Shifted Topography on Mount Roberts • Mt. Roberts actual lat/lon 58.2965 / -134.3863, elev 537m • Nearest gridpoint at 58.29683 / - 134.3862, elev 348m (I,j =185,165) • Better point at 58.29669 / -134.3805, elev 524m (I,j = 188,166)

  27. Mount Roberts – point (188,166) versus (185,165)

  28. Summary • Trying to push into “unexplored terrain” • Need to understand our early “success” and why it’s now evasive • Verification in this kind of terrain, with high-res topos can be very difficult • Different, but related problems have been found in other areas, such as the Alps • Need to consider smoothing and interpolations effects • Need to compare against profiler data

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