September 14, 2012 Mountain Wave Study at a Wind Farm Site in the Eastern Rocky Mountains Dr. Philippe Beaucage Senior Research Scientist Dr. Jeff Freedman Lead Research Scientist Daniel W. Bernadett Chief Engineer Dan Michaud Meteorologist Dr. Michael C. Brower Chief Technical Officer
Introduction SiteWind Coupled mesoscale microscale model CFD RANS model SM1 SM3 SM4 SM2 CFD: Computational Fluid Dynamics RANS: Reynolds average Navier Stokes
Motivation Terrain Elevation Map Monthly Average Wind Speeds Is it real? If it is real: (a) Are the measurements reliable? (b) which atmospheric mechanism is responsible? (c) what is the periodicity of the responsible phenomenon?
Local Wind Rose 1 year: 2010 2011 1 month: January 2011
Project Area: Eastern Rocky Mountains Looking towards southwest
Inter Mast Correlations (Wind Speeds) SM9 wind speed (57.6m Risoe) R 2 = 0.79 SM5 wind speed (81m Vector) SM9 wind speed (57.6m Vector) R 2 = 0.78 SM5 wind speed (81m Vector) SM9 wind speed (57.6m NRG) SM5 wind speed (81m NRG) R 2 = 0.79 SM9 wind speed (57.6m NRG) R 2 = 0.78 SM5 wind speed (81m NRG)
Mountain Meteorology Possible meteorological phenomena causing downslope winds during the winter season: Katabatic Winds Mountain Waves Hydraulic Flows en.wikipedia.org/wiki/katabatic_wind meted.ucar.edu Whiteman (2000)
Advanced Regional Prediction System (ARPS) Numerical Weather Prediction (NWP) model (Xue et al. 2000, 2001) Fully compressible, non hydrostatic Navier Stokes equations Conservation of mass, momentum and energy Complete suite of physics parameterization schemes Initial and boundary conditions provided by the North American Mesoscale (NAM) model analyses
ARPS Mesoscale Model Simulations Four representative cases during winter 2011: Case 1: 01 Jan 2011, 0:00 LST to 03 Jan 2011, 12:00 LST Case 2: 20 Jan 2011, 0:00 LST to 24 Jan 2011, 0:00 LST Case 3: 06 Feb 2011, 12:00 LST to 08 Feb 2011, 0:00 LST Case 4: 09 Feb 2011, 0:00 LST to 14 Feb 2011 0:00 LST Dynamical downscaling: x = 12 km 4 km 1 km 400 m 34 vertical levels (6 in the first 200 m)
Horizontal Wind Speed Map at 80 m Height
Time Series of Wind Speeds at SM9 SM9 Observations and ARPS Simulations for January 20 to 23, 2011
Vertical Cross Section of Virtual Potential Temperature
Vertical Cross Sections
Geopotential Height Anomaly Maps Show a normal flow regime in January 2011 at upper levels (left) and near the surface (right) over the Eastern Rocky mountains (from NCEP/NCAR reanalysis data). Anomaly map at 250 mb Anomaly map at 925 mb
Conclusions The project area is well situated for the generation and persistence of mountain wave induced downslope winds. Sonic and cup anemometers were shown to have reliable measurements; Numerical simulations indicated that ARPS is very accurate in capturing the magnitude and phase of the downslope winds at hub height; ARPS simulations also showed that mountain waves were responsible for the increase in wind speeds on the lee side of the mountain (due to a stable boundary layer); The winter of 2010 2011 was a typical winter according to the surface and upper level anomaly maps (based on the NCEP/NCAR reanalysis).
Thank you Contact info Dr. Philippe Beaucage: pbeaucage@awstruepower.com Selected References Lilly, D.K. (1978). A severe downslope windstorm and aircraft turbulence event induced by a mountain wave. J. Atmos. Sci. vol. 33, pp. 59 77. Doyle, J.D. et al. (2000). An intercomparison of model predicted wave breaking for the 11 January 1972 Boulder windstorm. Mon. Wea. Rev., vol. 128, pp.901 914. Xue, M., K. K. Droegemeier, and V. Wong (2000). The Advanced Regional Prediction System (ARPS) A multiscale nonhydrostatic atmospheric simulation and prediction tool. Part I: Model dynamics and verification. Meteor. Atmos. Physics., vol. 75, pp. 161 193. Chow, F.K, R.L. Street (2009). Evaluation of Turbulence Closure Models for Large Eddy Simulation over Complex Terrain: Flow over Askervein Hill. J. Appl. Meteor. and Clim., vol. 48, pp. 1050 1065.