Analyzing the Sequence Distribution Behavior and Frequency of extreme Events in the Selected Stations in the West of Iran

Human’s activities on the Earthchr('39')s atmosphere have changed significantly during the past century. Increasing the concentration of greenhouse gases leads to global warming and climate extremes which accordingly resulted the changes of the profiles. Therefore, studying the limit values in planning and policies in the agricultural sector and managing the water resources is very considered to be very critical.  Within this research, daily observations of precipitation, maximum and minimum temperature of 4 synoptic stations (located in West of Iran) were analyzed statistically during 2016-1960. For this goal,, modeling the distribution of temperature and precipitation in the region extreme was carried by extreme Generalized Extreme Value Distribution (GEV) in the base period  offrom1990 to1961. In the next step, frequency changes and extreme amounts from each station were compared in the recent observation period 2016-1991. Finally, the values of variables for different return periods were estimated. The results indicated that in the base period, the rainfall season series distribution, the hot and cold furnaces (except the Hamadan Station) are of the Gombel Type.  According to results, in the recent period, the distribution of cold temperatures except Kermanshah Station seems the base period as Gombel Type. however, the distribution of extreme temperatures in the recent period has changed from Gombel toWeibull type.. In relation to the extreme precipitation in the period of 2016-1991, the shape parameter has tended to be positive in all stations. While, its 95% confidence intervals include zero like the base period. Thus, its distribution follows the Gumbel Type like the base course. In the recent period, except Khorramabad Station, Ferrin precipitation amounts increased in the period of 5 and 10 years returns at the rest of the stations compared to the base period