Joint modelling and mapping of the parent population and extreme value distributions of the mean wind velocity

The analysis of wind actions and effects on structures involves the knowledge of the parent population and extreme value distributions of the mean wind velocity. In spite of an impressive amount of measurements, refined probabilistic models and detailed applications to the study of specific sites, there is an equally disheartening lack of available probabilistic information at the territorial scale, and, therefore, of tools effectively applicable in the engineering and codification sectors. Almost all of the international standards and codes report sufficiently reliable maps of the mean wind velocity with 50-year return periods. On the other hand, there are still few regulations that provide the distribution of the yearly maximum value of the mean wind velocity or such value as a function of the return period. Furthermore, no regulations provide the distribution of the parent population of the mean wind velocity that may be very important for serviceability and fatigue analyses. This paper introduces a joint representation of the parent population and extreme value distributions of the mean wind velocity of synoptic extratropical cyclones; starting from this model, simple but reliable expressions are derived, directly applicable in the engineering and codification sectors, aimed at bridging the gap described. The obtained expressions are critically examined, pointing out their advantages but also some apparent critical issues. A preliminary application of these expressions is carried out with reference to the Italian territory.