Analysis of monthly rainfall trend using innovative graphic and classical method in synoptic stations of Urmia Lake basin

Rainfall is one of the most important meteorological variables. Trend analysis is one of the most effective methods to observe the impacts of climate change on rainfall. Recently, new graphical methods have been proposed as an alternative to classical trend analysis. Innovative Polygon Trend Analysis (IPTA), which evolved from innovative trend analysis (ITA), is currently one of the proposed methods and there are no presuppositions in it. The purpose of this study is to compare IPTA and ITA with MMK and PETIT methods. To achieve this goal, the total monthly rainfall trend of six synoptic stations in the Lake Urmia Basin in 1988 to 2017 was examined. Based on the results of MMK test, it was observed that only in Tabriz, the rainfall trend was increasing, which was not significant at the 95% confidence level. In other stations, the rainfall trend was decreasing, which was significant in Maragheh and Mahabad. Also, the results obtained from ITA were consistent with the MMK. This indicates that the ITA method can be used to analyze the trend of meteorological variables. Using the IPTA, the slope of rainfall transfers from one month to the next can be calculated with the amount of trend length, which can not be calculated using classical methods such as MMK.