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The aim of this research was the recognition of effective dynamic and synoptic factors of freezing in Iran in order to prevent and mitigate this phenomenon. The During the December-January 8-15th 2006-2007 cold wave, there were a larg number of human and animal casualties and decline of gas pressure on vast parts of the country. The intercity and urban traffic was hampered. Between 75 to 80 percent of the whole country was frozen due to penetration of an extensive cold wave. This research shows that the main system that leads to freeze follows the following synoptic conditions: At sea level and 850 h.p., which are similar in terms of synoptic conditions a cold wave is extended from the Pole to Mid- southern Iran, causing the Polar and sub- polar cold transfer to the southern Iran. On the 500 h.p level (meso-troposphere) on the day of starting cold wave, a cyclone center by a curve of 492 dca-meter geo-potential is closed over the north Siberian, which is a rather deep trough spreading with a north- South extension on the south Iran.On continuance, this cyclone center and trough gradually spread to the lower latitudes and at the end of the fourth day of cold way, this trend is continued. The Polar cold trough moves toward the east or west and causes the contionution of downfall polar cold air in the mid layers of the atmosphere over Iran. From the fourth day, Siberian trough begins movement toward the east and makes stable air on the zone till the end of the cold wave.The synoptic conditions on the levels of 300 h.p and 500 h.p. are similar. Thus the cold wave by the penetration from the north with the extention of northern and southern blockage of the system that is continued for 8 days and also by transmitting of the polar cold air brings a severe cold toward Iran.

Keywords: Synoptic, IRAN, Freeze, Cold ware

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