Climatology of the winter extratropical antiyclones over Eurasia

This study presents the climatology of anticyclones in Eurasia during the winter based on the sea level pressure and 10 m winds extracted from the NCEP/NCAR reanalysis data for the period of 1948-2013. Results show that the main sources of anticyclones are:The Mongolian Plateau,Iran and its neighboring regions, the Mediterranean coast, central Siberia, north and west of the Baltic Sea and northeastern Russia. The Mongolian Plateau and Iran regions are the main sources of strong anticyclone events. Areas of large frequency of anticyclone occurrence also correspond to centers of high anticyclogenesis. Major areas of active anticyclones correspond to areas of large meridional gradients of temperature in the lower troposphere (850 hPa) and in the front of the upper-level ridge. There is a close relationship between the intensity and displacement of the anticyclones except for those originating from Mongolian Plateau and northeastern Russia. 44.2% of the total anticyclone events last 1-2 d, and only 3.2% last for more than 7 d. Strong anticyclone events are more likely to last longer than the weak ones.