Rainfall Trend Analysis using Innovative-Şen Method and Comparison with Traditional Methods (Case Study: Khorasan Razavi Province)

Rainfall variations is one of the most important factors in climate change which can be analysed using different methods. This research aims to investigate the application of the innovative-Sen method for monthly, seasonal, and annual trend analysis of precipitation in Khorasan Razavi province. A series of 30 years of rainfall data from 39 rain stations of the province have been used. For the comparison purpose, Mann-Kendall, Spearman, and linear regression methods have also been considered. For quantitative evaluation of graphical results of the Sen method, a statistical analysis has been proposed. The results of traditional methods indicated that the rainfall of Aban month )October( has a significant increasing trend in confidence interval of 95%, and the rainfall of other months, seasons, and years do not show any significant trend, except for the regression method. Rainfalls of Aban )October(, Khordad )May(, and Tir )June( months, as well as autumn and summer seasons, have an increasing trend and other considered periods have a decreasing trend. The results of innovative-Sen method analysis in low, medium, and high values indicated that the maximum and minimum variations are related to the rainfall of winter and Mehr )September( month, respectively. Also, the statistical analysis showed a significant trend similar to the regression method only exist in the winter season of the province.