mountain wave study at wind farm site in eastern rocky ...€¦ · capturing the magnitude and...

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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


Introduction

SiteWindCoupled mesoscale‐microscale model

CFDRANS model

CFD: Computational Fluid DynamicsRANS: Reynolds‐average Navier‐Stokes

SM4

SM3

SM2

SM1


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?


Local Wind Rose

1 year: 2010‐2011 1 month: January 2011


Project Area: Eastern Rocky Mountains

Looking towards southwest


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)


NRG

)


Vector)


NRG

)

R2 = 0.79

R2 = 0.79

R2 = 0.78

R2 = 0.78


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)


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 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)


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: [email protected]

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.

mountain wave study at wind farm site in eastern rocky ...€¦ · capturing the magnitude and...

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