Emeis, S.

Foreman, R.J.

English

Foreman, R. J.

KITopen

Enhancing the prediction of turbulent kineticenergy in the marine atmospheric boundary layerRichard Foreman, Stefan Emeis-EMS 2010, ZürichInstitute for Meteorology and Climate Research.Karlsruhe Institute of Technology (KIT).Garmisch-Partenkirchen, GermanyOverview• Our work focuses on improving the calculation of turbulentquantities, e.g. turbulent kinetic energy (TKE), over watersurfaces by numerical weather prediction models.• We will show model updates that improve the calculation ofTKE over water• Also valid over land.• Enhancement of knowledge of offshore turbulence associatedwith the growth of offshore wind energy.FINO1 - Offshore research platform• FINO1 - North Sea, 45 kmNorth of Borkum Island.• Cup anemometers 30-100m every 10 m.• Sonic anemometers 40, 60& 80 m.Initial Model Results - WRF (Weather Research andForecasting) model setup• Use Weather Research and Forecast(WRF) model(http://www.mmm.ucar.edu/wrf/users/)• Planetary boundary layer scheme:Mellor-Yamada-Janjic (MYJ)• Differential equation for TKE:12q2 = 12(u′2 + v ′2 + w ′2)• Exchange coefficients solved algebraically.• These outputs will be shown below.• Single domain: 151 x 151 x 10 kmresolution, 51 model levelsInitial Model Results - FINO 1• January 01-10, 2005 - High wind speeds, steady winddirection (Westerly).• Wind speed captured well.• Turbulent kinetic energy underpredicted.Initial Model Results• Investigate reasons for the underprediction of TKE.• Could turbulence be higher at FINO 1 due to the presence ofwaves?• But experimental and field data is as yet inconclusive.• Considerable variance in particularly field results.• Some suggesting higher turbulence over water compared withland (and vice versa).Why then is the turbulence at FINO1 so poorly predicted?• Difficult to distinguish a clear difference between themagnitude of turbulence over water and land with currentlyavailable dataRecent experimental boundary layer data• MY closure constants determined from laboratory databetween 1950-1975.• Closure constants determined from turbulent statistics inrange where production = dissipation and Reynolds numberindependence (close to the wall).• Have measurement techniques advanced sufficiently sincethen?• In MY model, closure constant B1 =(qu∗)3.• MY82: qu∗= 2.55 (B1 = 16.58)• Current WRF model: qu∗= 2.28 (B1 = 11.85)• More recent data suggests this should be higher:Recalibrated MYJ scheme in WRF - FINO1Table: Summary of statistics from recent high Reynolds numberboundary layer experiments.Author Re (x 104) u′u∗v′u∗w′u∗qu∗B1 =“qu∗”3Österland (1999) 2.25 2.3 1.55 1.05 2.97 26.2Carlier & Stanislas (2005) 2.06 2.31 1.52 1.06 2.96 25.9Mellor-Yamada Models:Mellor & Yamada (1982) - 1.9 1.2 1.2 2.55 16.6Current WRF - 1.70 1.07 1.07 2.28 11.9Updated here - 1.97 1.57 1.57 2.96 26.0• Update MYJ coefficients based on B1 = 26.0 (see Mellor &Yamada, 1982)• Modify master length scale based on Nakanishi (2001).• Obtain dimensionless wind and temperature gradientsmatching Businger (1971).Results - FINO1• Mean velocity essentially unchanged (slightly higher).• Turbulent kinetic energy improved by roughly 40% (RMS)Results - FINO1• Km reduced and improved by roughly 20%• Higher velocity shear.Results over land - Hamburg Weather Mast• Hamburg Weather Mast.• Data here from cup andsonic at 50 m.Recalibrated MYJ scheme in WRF- Hamburg weather mast -• Test to see if constants work over landSome conclusions and currently ongoing work• Updates to the MYJ boundary-layer model improvecalculation of turbulent quantities both over land and sea.• Further conditions are being tested at FINO1 (differentatmospheric stabilities).• Much more testing needed over land.• Looking for things specific over water to be included in theWRF model (coupling of WRF with a wave model?).Acknowledgements• Work funded by German Federal Ministry of the Environmentvia the PTJ under No. 0327696 (WP5 of OWEA).• FINO1 and Hamburg weather mast data was kindly providedby DEWI and Ingo Lange (Hamburg University), respectively.• WRF model provided by UCAR/NCAR/MMM.

Enhancing the prediction of turbulent kinetic energy in the marine atmospheric bondary layer

https://publikationen.bibliothek.kit.edu/230081619/3815790

Enhancing the prediction of turbulent kinetic energy in the marine atmospheric bondary layer

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