Prevailing cloud types in Athens

Summary Prevailing cloud types and their daily, annual and interannual variation in the region of Athens were examined. These cloud types were grouped into five major classes: cumuliform, stratiform, cirriform, medium altitude clouds and no cloud class, referred to in the study as clear skies. The results are expressed as frequency of occurrence of different cloud classes.It is found that clear skies and prevailing cumuliform clouds both have summer maxima. Stratiform and medium altitude clouds have winter maxima, while cirriform clouds exhibit a semiannual variation, with maxima in May and October.In terms of interannual trends, the tendency of stratiform clouds to prevail decreases while the tendency of cumuliform clouds to prevail increases, probably due to urban expansion and the increase in urban activity.With 10 Figures