Trends analysis in rainfall data series in Duhok city, Kurdistan region, Iraq

The effect of climate change on human life has led the scientific community to observe the behaviour of meteorological and climatic variables on various spatial and temporal scales. However, analysing precipitation trends is important for studying the impact of climate change on water resource planning and management. This study examines changes in rainfall data at-site location in Duhok city, Kurdistan Region, Iraq using rainfall data for 42 years covering the period of 1976-2017. The quality control test was performed for rainfall data series using Mandel's k method. The non-parametric tests (Mann-Kendall and Modified Mann-Kendall) with the Innovative Trend Analysis method have been used to assess the change in monthly, seasonal, and annual rainfall series. Also, the homogeneity in rainfall data series has been investigated using Van Bell and Hughes homogeneity, Runs, Pettit, Standard Normal Homogeneity, Buishand Range, and Von Neumann Rate tests. The results of Mandel's k method showed that no outlier was detected in the study area. The trend test results revealed an increasing trend in some rainfall data series and a decreasing trend in some other data series in the study area. The maximum increasing significant trend has been observed in January and Winter series at a 5% significance level. In addition, the set cases of monthly and seasonal data series were found to be nonhomogeneous, while according to each separate case of time series, it has been found that the most of data series appears to be homogeneous.