عنوان مقاله [English]
نویسندگان [English]چکیده [English]
In this study, frequency and location of frontogenesis related to heavy rainfall have been analyzed using environmental to circulation approach. Based on the threshold of upper 99 percent, we selected 125 days of the super and overall heavy rainfall from IRIMO data base (included 1437 synoptic, climatic and rain gage stations from 21/3/1961 up to 31/12/2004). Frontogenesis frequency and their locations have been detected from to E and to N in five levels (1000, 925, 850, 700, 600 and 500 hPa level) at 00:00, 06:00 and 12:00 UTC. The results of this study showed that frontogenesis at 500, 600 and 700 hPa levels and its subsequent instability do not affect Iran very much (with an exception of 18:00 UTC in 500 hPa Level). Frequency analysis of frontogenesis at 850 hPa level indicated that in comparison to surrounding areas, Iran is more active. Generally, frequency of frontogenesis is highest at 925 and 1000 hPa levels over Iran.