Comprehensive empirical analysis of ERA-40 surface wind speed distribution over Europe

As a first step of an exhaustive assessment of wind energy potential over Europe, here, we provide a unified description of the wind speed probability distribution both over sea and land. We evaluated surface wind velocity records of the ERA-40 data base covering 44 years with a temporal resolution of 6 hours. We tested the well known distribution functions (Rayleigh, binormal, Weibull, lognormal etc.) and observed that the popular Weibull function performs supremely, however, it fails at many locations over land. We found that the generalized gamma distribution, which has independent shape parameters for both tails, provides an adequate and unified description almost everywhere. The geographical distribution of the fitted parameters reveals the possible climatological origin of different wind speed distributions.