عنوان مقاله [English]
Tehran has in the South of Alborz Mountains and located, in one of the higher parts of the mountain. That's why during the cold period frequently affected by severe frosts and poorly placed. Tehran, with a population of over 8 million people and more than 3 million vehicles at the time of freezing disorders are plenty of daily transportation. for study the characteristics of ice in Tehran, by examining all the weather stations in Tehran during a period of (2011-1985), First, was investigated the same amount of thermal stations Tehran. Then light frost days Was extracted (minimum temperature between 0 to-1/1, Ice average between -1/1 to- 2/2, severe frosts less than -2/2). Then map the number of days of frost, frost season, and ice, mild, moderate, severe and associated with the likelihood of them is drawn. The results indicate that the probability of 50%, the probability first frost in northern Tehran stations Aminabad is December, and in Mehrabad, Doshantape and Geophysics stations, are January and Cheetgar station is February. It can be seen on the first severe frosts in January probability level of 50 percent in all stations, but the date of the last frost in the station can be seen in the months of February and March. In terms of the total number of frost days, over 50 days area the ice to the northern end in Tehran is limited, which includes the northern regions is 1, 2,5,14 and 22. The total number of frost days zone like sea waves as well corresponds with topographic contour line, to the south of Tehran is reduced. Only the South East of Tehran because of its proximity to the heights of this order is disturbed. Zoning in Tehran is generally along the north-south. While examining patterns of spatial and temporal variability of temperature parameters show that Ice Area, West-East is spread pattern. So, the snow and ice the advance and retreat. Along the contours.