The turning of the wind in the atmospheric boundary layer

Here we use accurate observations of the wind speed vector to analyze the behavior with height of the wind direction. The observations are a combination of tall meteorological mast and long-range wind lidar measurements covering the entire atmospheric boundary layer. The observations were performed at the Hovsore site in Denmark, which is a flat farmland area with a nearly homogeneous easterly upstream sector. Therefore, within that sector, the turning of the wind is caused by a combination of atmospheric stability, Coriolis, roughness, horizontal pressure gradient and baroclinity effects. Atmospheric stability was measured using sonic anemometers placed at different heights on the mast. Horizontal pressure gradients and baroclinity are derived from outputs of a numerical weather prediction model and are used to estimate the geostrophic wind. It is found, for these specific and relatively short periods of analysis, that under both barotropic and baroclinic conditions, the model predicts the gradient and geostrophic wind well, explaining for a particular case an 'unusual' backing of the wind. The observed conditions at the surface, on the other hand, explain the differences in wind veering. The simulated winds underpredict the turning of the wind and the boundary-layer winds in general.

[1]  Alfredo Pena Diaz.  Sensing the wind profile , 2009 .

[2]  C. Draxl,et al.  Evaluating winds and vertical wind shear from Weather Research and Forecasting model forecasts using seven planetary boundary layer schemes , 2014 .

[3]  Alfredo Peña,et al.  The Høvsøre Tall Wind-Profile Experiment: A Description of Wind Profile Observations in the Atmospheric Boundary Layer , 2013, Boundary-Layer Meteorology.

[4]  Jeremy A. Gibbs,et al.  Evaluating Weather Research and Forecasting (WRF) Model Predictions of Turbulent Flow Parameters in a Dry Convective Boundary Layer , 2011 .

[5]  J. Dudhia,et al.  A New Vertical Diffusion Package with an Explicit Treatment of Entrainment Processes , 2006 .

[6]  Wouter Peters,et al.  Confronting the WRF and RAMS mesoscale models with innovative observations in the Netherlands: Evaluating the boundary layer heat budget , 2011 .

[7]  J. Holton.  An introduction to dynamic meteorology , 2004 .

[8]  Song-You Hong,et al.  Intercomparison of Planetary Boundary-Layer Parametrizations in the WRF Model for a Single Day from CASES-99 , 2011 .

[9]  R. Stull.  An Introduction to Boundary Layer Meteorology , 1988 .

[10]  Torben Mikkelsen,et al.  Long-Term Profiles of Wind and Weibull Distribution Parameters up to 600 m in a Rural Coastal and an Inland Suburban Area , 2014, Boundary-Layer Meteorology.

[11]  Alfredo Peña,et al.  Observations of the atmospheric boundary layer height under marine upstream flow conditions at a coastal site , 2013 .

[12]  Jakob Mann,et al.  On the length‐scale of the wind profile , 2010 .

[13]  Charlotte Bay Hasager,et al.  Comparing mixing-length models of the diabatic wind profile over homogeneous terrain , 2010 .

[14]  Albert A. M. Holtslag,et al.  Estimates of diabatic wind speed profiles from near-surface weather observations , 1984 .

[15]  J. van Beeck,et al.  Turbulent fluxes, stability and shear in the offshore environment: Mesoscale modelling and field observations at FINO1 , 2012 .

[16]  Alfredo Peña,et al.  The Wind Profile in the Coastal Boundary Layer: Wind Lidar Measurements and Numerical Modelling , 2013, Boundary-Layer Meteorology.

[17]  S. Larsen,et al.  On the extension of the wind profile over homogeneous terrain beyond the surface boundary layer , 2007 .