Analysis of Iran’s thermal seasons and variation during last decades

In this study, we will be addressing Iran’s thermal seasons and its variance during 1/1/1370 to 29/12/1392 of the solar calendar. At first daily data from 49 stations were gathered all over Iran in the mentioned period of time. The difference between yearly standard deviation with deviation (Dev) for each station was calculated and therefore seasonal advancing and receding was detected. Finally, three matrices namely SWS (Start Warm season), EWS (End Warm season) and SWL (Season Warm Length) all with dimensions of 63 × 49 were developed. Afterwards, to understand homogeneous arena, cluster-analysis with merger method was executed on matrices. Ultimately, by using a non-parametric modified Mann Kendall test, meaningful variability, start variability rate, final and warm period in the studied period were measured. Findings indicate that thermal seasons in Iran aren’t conformed to official calendar in the country and the country’s arena ought to be divided into four homogeneous thermal seasons. Latitude, longitude, altitude, distance from water resources as well as atmospheric humidity have an important effect on the known arena. Iran’s thermal seasons have been significantly altered during the start and end of studied period. Overall, thermal period in most parts of Iran have increased. In the studied stations, the decreasing rate of warm period are significantly more than decreasing and increasing rate of the ending warm period. It seems that the findings of this study are strong evidences concerning the effects of dominant heat all over Iran and altering the seasons as well as thermal situation.