Prediction of the Starting and Ending of Freezing Periods of Ardabil Province by Using HADCM3 Climatic Model

Introduction and Background: One of the causes of the widespread damages caused by frost is the fact that its dimensions and nature are unknown. The prediction of frosts is one of the issues that, if implemented, can be a very great help in reducing the adverse effects of this phenomenon. Aims: In this research, daily minimum temperature is predicted for analyzing the start and end of freezing period in Parsabad, Ardabil and Khalkhal stations for next three periods 2011- 2030, 2046-2065 and 2080 – 2099. Used data was data related to meteorological models, daily rainfall data, max and min temperature and sunny hours from 1996 to 2016. First, to choose the efficient model of general circulation of atmosphere, the results of nine climatic models were compared, and HADCM3 model was selected as the best model. This model’s output was down scaled by LARS-WG downscaling method. This method is very effective in downscaling of applied model’s output. After simulation of daily minimum temperature for future periods; with regard to being correct of real data from 2011 to 2016; simulated data was compared with real data. Results showed that simulated data don’t have significant difference with station’s real data. Therefore, meteorological model of HADCM3 has acceptable capability in this simulation. According to the results obtained from this research, minimum mean temperature of stations in future years will be increasing. Date of freezing starting is delayed eventually in future periods and starting and ending date of them is closed together over the time and freezing period duration is more shortened. Date of freezing starting in Khalkhal station was the first day of October through 7th of October, in Ardabil station between 9th of October through 30th October and in Parsabad station between 10th of November through 8th of December. Date of freezing ending in Khalkhal station was estimated 13th of April through 18th of May, in Ardabil station between 17th of April through 18th May and in Parsabad station between 26th April through 28th of March.