Spatial Distribution of blocking systems and its Coincidence to the Cold Seasons wet year in Iran

The purpose of this study was to investigate and identify the effect of blocking systems on Iran's poisoning during the period 1975-2015 using the Blocking numerical index. The results showed that in the cold seasons most of the blockades affecting the atmosphere of Iran were in the northern Atlas. Also, the study of the severity of effective blockades affecting Iran's climate showed that the strong blocking is moderate in terms of the highest number after the blocking, indicating that Iran was more affected by moderate blocking (74.6%) and then strong (21.1%). The number of weak blocking is very low (4.3%). Due to the frequency of occurrence of blocking also was found wet Iran in months. Cold, the core of the blocking in between longitude 30 ° west and 30 ° East over the Atlantic formed and as the warm season approaching, the core the land was transferred to the regions dominated by positive changes in parameters affect precipitation. Also, in Bandal's review in different seasons, it was revealed that in winter, with the retreat of the adjacent high pressure and the strength of the polar vertex, along with the occurrence of strong and long blockades, the average rainfall is more than the other seasons.