Farnood Freidooni - Master student in Mechanical engineering, Imam Khomeini International University, Qazvin, Iran
Fatemeh shahryar - PhD candidate in Climatology,Islamic Azad University of Najafabad, Isfahan, Iran

Regarding the climate changes, global warming, forecasting the maximum temperature and a hot weather wave has been considered as one of the most important climatic parameters which affect the ecosystems. Studying and analyzing the maximum temperature is of great importance in managing the water and natural resources, agricultural products, spreading pests and diseases, Evaporation and transpiration and etc. In the present paper, the daily maximum temperature of five weather stations in northern hillside of Alborz which have been collected during 1980 to 2010 in order to determine the hot weather waves in these hillside in April to September, furthermore, a heat index was specified for each month according to the above mentioned data, and the maximum temperatures which were more than the defined index were determined as the heat wave and these waves were categorized into two classes of short term and long term and finally using the Markov Chain Model, the transition probability matrix and the reliability probability has been computed with multiple power. The duration period and the return of one to ten days for each month and in each weather forecast station was analyzed and studied and the process of temperature changes was discussed. The maximum short term heat wave in the stations belong terms to Gorgan, the long term heat wave belong terms to Qaem shahr. The probability of the days, without the heat waves, after which a heat wave occurs, varies between 2% in Ramsar to 4% in Gorgan in the stations. The results show that the frequency of 1 to 3 days is more than others in all the stations and also in all the seasons. Key words: Heat wave, Heat index, Markov Chain Models, Northern Hillside of Alborz

Heat wave, Heat index, Markov ChainModels, Northern Hillside of Alborz