Spatiotemporal trend analysis of rainfall for deeper understanding of the pattern and its implications over western Amhara, Ethiopia: innovative trend analysis method

Long-term changes in rainfall are a key factor influencing climatic variability. Therefore, analyzing the spatial and temporal patterns of rainfall is essential. The examination of the spatiotemporal patterns of seasonal and yearly rainfall through creative trend analysis, however, has not been covered in previous studies. The study examined the spatiotemporal patterns of annual and seasonal rainfall in western Amhara using the Mann–Kendall test and Sen's slope estimator. Additionally, the latest innovative trend analysis method was employed to assess the clusters of low, medium, and high rainfall. Thirty chosen grid points from the Enhancing National Climate Services daily rainfall dataset were obtained from the Ethiopian Meteorology Institute, covering the period from 1991 to 2020. The result indicated that, in total, of 120 annual and seasonal time series, the ITA approach revealed 95- time series with significant trends in all annual and seasonal timeframes. However, the Mann–Kendall test and Sen’s slope estimator found significant trends in only 14-time series across all timescales at a 5% significance level. Furthermore, the ITA method demonstrated that most rainfall grid points exhibited significant clusters and upward trends during the Kiremt and annual periods; however, the Bega season experienced reduced rainfall, suggesting downward trends. As a result, the comparative results showed that the innovative trend analysis method is more reliable and effective than the Mann–Kendall test because it can identify both monotonic and non-monotonic trends that the Mann–Kendall method cannot recognize. Hence, the rainfall trends during the Kiremt and Bega seasons are increasing and decreasing, respectively. Therefore, adapting to the risks of rainfall variability requires strategies such as climate advisory services, water conservation, supplemental and deficit irrigation, and planting drought-resistant and early-maturing crops.