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Synoptic Analysis of Frost Days of Ardebil Province

In order to analyze the synoptic origin of frost days of Ardebil the daily temperatures of the four synoptic stations Ardebil, Pars- Abad, Khalkhal and Meshkin-Shahr of the province were obtained from the Meterological Organization of the Islamic Republic of Iran for the 1995-2004 period. From the frost periods only three frost periods were selected. These were the earliest, the longest, and the latest frost periods. These periods were analyzed thoroughly on the daily weather maps of surface and 500 hPa. The analysis showed that the pronounced factor in producing the synoptic frosts of the area are mainly moving western anticyclones and Siberian High. The westerly systems are the frequent factor, but the strong and widespread frost happened when a ridge from Siberian High was extended to the province. On the 500 hPa level the extension of a deep arctic through over the area brings very cold air to the region.