Nowadays wind energy represents one of the most exploited renewable energy sources in the world for generating electricity. During the last two decades, its use and the number of installed wind farms has increased dramatically. This rapid growth, which is still ongoing, has led to an ever increasing search for new areas suitable to install WTs. So, in addition to the traditional wind energy sites, complex onshore ones have begun to be explored and at present, they are still being investigated. In these terrains, characterized by a more varied topography and roughness, modeling of the wind conditions comes out to be more challenging.