Characterizing the variability and trend of rainfall in central highlands of Abbay Basin, Ethiopia: using IMERG-06 dataset

Abstract

ABSTRACT This study examines the spatiotemporal variability and trends of rainfall in the central highlands of Abbay Basin using the Integrated Multi-satellite Retrievals for GPM (IMERG-06) dataset. Parameters on onset and cessation dates, dry spells, Coefficient of Variation (CV%), and Standardized Rainfall Anomalies were utilized to evaluate rainfall variability and seasonality. Trend analysis was carried out using Mann-Kendall test and Sen’s slope estimator. The results highlighted a consistent pattern of late onset and early cessation of rainfall. The CV values for annual (10.7%), kiremt (11.7%), and belg (10.6%) seasons rainfall indicate moderate variability, while bega (22.6%) rainfall showed higher variability. SRA findings reveal episodic fluctuations between wet and dry years. The trend analysis demonstrates a statistically significant increasing trend in annual (9.14 mm/year) and belg seasons (6.94 mm/year) rainfall. However, kiremt season exhibited statistically non-significant (p > 0.05) decreasing trend. The temporal variability in rainfall onset, cessation dates and duration significantly impacts agricultural processes such as tillage and planting operations, affecting crop production. While the study area holds potential for agricultural activities, climate variability may reduce productivity. Therefore, the study findings are valuable for agricultural developers, planners and water resource managers. Including additional weather elements is crucial to enhance the precision and reliability of these findings for practical applications.