Tocarry outthis research, interpolated dataofdaily rainfall fromIran’sAsfazari databaseduring 1/1/1979–31/12/2013 is used. The day along with pervasive rainfall considered a day that at least50%ofIran’sterritoryhasreceivedmorethan 1mmforatleasttwoconsecutive days.Based on mentioned thresholds, 224 days selected for statistical analysis. The sea level pressure data, zonal and meridional wind components and specific humidity with spatial resolution of 0.25*0.25 Gaussian degree in spatial domain of 10°N to 60°N and 15°E to 75°E obtained from the European Center for Medium range Weather Forecasting (ECMWF) ERA-Interim for selected days. Then on the data matrix of sea level pressure, the cluster analysis by Ward linkage method done and 4 sea level pressure patterns with different configuration of synoptic systems were identified. The findings showed that in the sea level, the interaction between southern thermal low pressure systems (Arabia low pressure) with Europe and Siberia cold immigrant high pressurebothbyindividual andintegrationandanticyclone circulationofArabseafromthelowlevel of 1000–500hPa of troposphere have the most role on occurrence of durable and pervasive rainfall of Iran. The most Vertically Integrated Moisture Flux Convergence in the first layer of troposphere (1000–850hPa) observed in low height regions, in the second layer of troposphere (775–700hPa) on Zagros Mountains and in third layer of troposphere (600–500hPa) is seen in mountains leeward of Iran. Also the results showed that the maximum rainfall cores has the most coordination with Vertically Integrated Moisture Flux Convergence (VIMFC) in the second layer of troposphere (775–700hPa) on the Zagros heights in the southwest of Iran.
