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Albany, New York | Barcelona, Spain | Bangalore, India | awstruepower.com | +1 877‐899‐3463©2012 AWS Truepower, LLC
September 14, 2012
Mountain Wave Study at a Wind Farm Site in the Eastern Rocky MountainsDr. Philippe Beaucage
Dr. Jeff Freedman
Senior Research Scientist
Lead Research Scientist
Daniel W. BernadettChief Engineer
Dan MichaudMeteorologist
Dr. Michael C. BrowerChief Technical Officer
Albany, New York | Barcelona, Spain | Bangalore, India | awstruepower.com | +1 877‐899‐3463©2012 AWS Truepower, LLC
Introduction
SiteWindCoupled mesoscale‐microscale model
CFDRANS model
CFD: Computational Fluid DynamicsRANS: Reynolds‐average Navier‐Stokes
SM4
SM3
SM2
SM1
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Motivation
Terrain Elevation Map
Monthly Average Wind Speeds
Is it real? (a) Are the measurements reliable? If it is real: (b) which atmospheric mechanism is responsible?
(c) what is the periodicity of the responsible phenomenon?
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Local Wind Rose
1 year: 2010‐2011 1 month: January 2011
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Project Area: Eastern Rocky Mountains
Looking towards southwest
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Inter‐Mast Correlations (Wind Speeds)
SM5 wind speed (81m Vector) SM5 wind speed (81m Vector)
SM5 wind speed (81m NRG) SM5 wind speed (81m NRG)
SM9 wind speed (57.6m
Riso
e)
SM9 wind speed (57.6m
NRG
)
SM9 wind speed (57.6m
Vector)
SM9 wind speed (57.6m
NRG
)
R2 = 0.79
R2 = 0.79
R2 = 0.78
R2 = 0.78
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Mountain Meteorology
Possible meteorological phenomena causing downslope winds during the winter season:
Katabatic Winds
en.wikipedia.org/wiki/Katabatic_wind
Mountain Waves
meted.ucar.edu
Hydraulic Flows
Whiteman (2000)
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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
Albany, New York | Barcelona, Spain | Bangalore, India | awstruepower.com | +1 877‐899‐3463©2012 AWS Truepower, LLC
ARPS Mesoscale Model Simulations
Four representative cases during winter 2011:
Case 1: 01 Jan 2011, 0:00 LSTto 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)
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Horizontal Wind Speed Map at 80‐m Height
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Time Series of Wind Speeds at SM9
SM9 Observations and ARPS Simulations for January 20 to 23, 2011
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Vertical Cross‐Section of Virtual Potential Temperature
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Vertical Cross Sections
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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
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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).
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Thank you
Contact info•Dr. Philippe Beaucage: pbeaucage@awstruepower.com
Selected ReferencesLilly, 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.