Diurnal surface wind variations over complex terrain

Abstract

The diurnal surface wind variability during the summer season (June, July and August) over a complex terrain region located in the Northeast of the Iberian Peninsula is investigated using observations and a numerical simulation. Two main modes of variation were identified (96.8 % of the variance) by means of principal component analysis. The first one contributes with a wind speed maximum in the afternoon and a wind speed minimum at the end of the night. The second mode of variation introduces a local behaviour that contributes with a wind speed maximum or minimum at central hours of the day. The specific contributions and relative importance of different physical mechanisms are investigated and discussed. The first mode is related to landand sea-breezes. The second mode seems to be associated with thermal circulations induced by horizontal temperature gradients generated by the orography, and the homogenization exerted by turbulent mixing within the planetary boundary layer.