The atmospheric conditions over Europe and the Mediterranean, favoring snow events in Athens, Greece

摘要

The 3-dimensional structure and the evolution of atmospheric circulationfavoring snowfall in Athens are examined. The study refers to 61 snowevents, which occurred during the period 1958–2001. For each one of theevents, the patterns of MSL pressure, 850 hPa and 500 hPa air temperatures,500 hPa geopotential height and 1000–500 hPa thickness are constructed forthe European region, for the day before (D-1), the first day (D) and the dayafter the end of the event (END). A statistical methodology involving FactorAnalysis and Cluster Analysis is applied to the above data sets and the 61cases are finally classified into five clusters. These clusters aregenerally characterized by a north-easterly flow in the lower troposphereover the Athens area. This flow is associated with the presence of a lowpressure system around Cyprus and an anticyclone over Europe. The position,the intensity and the trajectories of the surface and the upper air systemsduring D-1, D and END days are generally different among the five clusters.