Jimenez, Pedro A., Centre for Energy, Environment,
and Techonology (CIEMAT) and J. Dudhia, NCAR
The ability of the WRF
model to reproduce the surface wind direction over complex terrain is examined.
A simulation spanning a winter season is compared against wind direction
records from a mesoscale network located in a complex terrain region in the
Northeast of the Iberian Peninsula. A previous evaluation has shown the ability
of WRF to reproduce the wind speed over the region. Hence, the present
investigation complements the previous evaluation providing information of the
model's ability to reproduce the direction of the surface flow. The errors are
quantified in terms of scores explicitly designed to deal with the circular
nature of the wind direction. Results show that the errors depend on the wind
speed. The larger the wind speed the smaller the wind direction errors. Areas
with more complex terrain tend to show larger errors that can present even a
systematic behavior. The importance of the grid point selected for the
comparison with observations is also analyzed. The wind information from the
nearest grid point is not always the most adequate over areas of complex
terrain where nearby grid points can provide better comparison with
observations. These representativeness errors are less important over gentle terrain.
A statistical correction of the simulation based on simple linear regressions
is also explored. The correction suppresses the systematic errors that occur at
high wind speeds providing better estimations of the wind direction.