عنوان مقاله [English]
In this research, temporal trends of maximum temperature values were investigated in various regions of Iran. For this purpose, the meteorological observations collected from 33 high quality meteorological sites for a 40-year period (1977-2016) were used and statistically significant Tmax trends in the monthly, seasonal and annual time basis were detected by the non- parametric Mann-Kendall and Spearman tests at confidence level of 95%. For eliminating the effect of serial correlation on test results, the Trend Free Pre-Whitening (TFPW) approach was applied. The results indicated that the Tmax trends for some sites were increasing (positive) but for some sites showed decreasing (negative) trends. The highest positive and negative trend on the annual time scale occurred at Kermanshah and Torbat heydarieh, respectively. The positive trend of Tmax on the monthly, seasonal and annual time scale was observed at Mashhad, Tabriz, Abadan, Ahvaz, Boshehr, Shiraz, Kermanshah and Yazd sites. In general, the performances and capabilities of Mann-Kendall and Spearman tests were consistence at verified confidence level.