Mediterranean contemporary winter and summer air mass climatology with respect to temperature and moisture flux

Abstract

Large-scale moisture fluxes and backward air mass trajectories and frequencies were investigated to explain the mechanisms of synoptic-scale seasonal variability of air masses in the Mediterranean basin. For this aim, reanalysis data were used to calculate variations in moisture flux with respect to temperature and stability according to the 8 standard pressure levels between 1000 and 300 hPa. Investigating air mass characteristics changing with pressure levels provided new information in terms of air mass climatology for the Mediterranean basin. Results show that due to the influence of westerly flows, the Atlantic is the main source of moisture higher than 700 hPa. Turbulent transport of moisture from the Mediterranean Sea is the source of moisture close to the surface, which corresponds to levels lower than 700 hPa. According to the trajectory analysis, the continental Arctic (cA) air mass can reach the Mediterranean basin and provide very wet conditions over the Mediterranean basin during winter. In addition, during very dry conditions in summer, all air mass currents originate from surface pressure levels between 1000 and 850 hPa. These relatively warm and dominant air masses cause cloud-free conditions with very low precipitation over the Mediterranean basin. This study showed that air masses should be analyzed not only according to their source and path but also according to pressure levels. Therefore, more studies are needed investigating the contemporary air mass climatology of a specific region.