Synoptic and dynamic aspects of widespread snowstorm with dangerous blizzard conditions in the territory of Iran – 3 to 9 February, 1972

Blizzards are severe forms of snowstorms that occur in the middle and upper latitudes of the northern hemisphere in winter season. The devastating disaster of a snowstorm with dangerous blizzard conditions on February 3 to 9, 1972, with more than 4,000 dead in Iran, is one of the most destructive snowstorms in the world. In this study, aspects of the synoptic scale at the time of occurrence of this phenomenon have been investigated using the reanalysis data of NCEP/NCAR and ECMWF databases. The variables used include geopotential height, sea level pressure, air temperature, specific humidity, relative humidity and zonal and meridional velocity of wind. In addition, the parameters of omega, relative vorticity, and zonal jet index have been calculated to explain the performance of the atmospheric system. The results indicate the dominance of atmospheric block (Rex) system in two separate phases from 3 to 6 February and from 7 to 9 February. The role of the artic polar vortex in injecting cold air into low latitudes and a noticeable decrease in temperature before a snowstorm and blizzard in saturating the atmosphere and providing the moisture needed for snowfall is quite evident. The zonal index of Jetstream showed the significant jump of the core of subtropical jet stream at the time of the occurrence of this extreme phenomenon.The zonal index of Jetstream showed the significant jump of the core of subtropical jet stream at the time of the occurrence of this extreme phenomenon.The zonal index of Jetstream showed the significant jump of the core of subtropical jet stream at the time of the occurrence of this extreme phenomenon.