Analysis of rainfall and temperature trends and variability in semi-arid Tharaka South Subcounty, Kenya

Abstract

To better understand the impacts of climate variability, including spatiotemporal variations in mean rainfall, temperature, and other climatic elements, it is imperative to analyze the dynamics of these elements. Despite the high vulnerability of the Tharaka South Subcounty, Kenya, to the impacts of climate change and variability, no studies have analyzed the local climatic trends and variability to inform response strategies. In this study, we analyzed rainfall and temperature trends and variability in Tharaka South Subcounty using gridded rainfall and temperature data sourced from CHIRPS and CHIRTS. Variability analysis employed descriptive statistics, coefficients of variation, standardized anomalies, and the precipitation concentration index. Trends were analyzed using a Mann-Kendall test and Sen’s slope estimator. The study area is characterized by low rainfall that shows a decreasing trend. Local rainfall is generally marked by high and increasing variability, high and increasing concentration, and a high probability of extreme events. The area has also experienced increasingly severe and frequent droughts, with most years in the study period having below-average rainfall. Rainfall variability is thus characterized by a decrease in rainfall, high rainfall concentration, extreme rainfall events, and more frequent and severe droughts. Large-scale climate forcings also influence the local rainfall trends and variability. In addition, the study area has high temperatures that show an increasing trend, and the region experiences a fluctuating temperature regime. An increase in temperature is associated with a reduction in rainfall amount. Moreover, the area is marked by spatial variability of rainfall and temperature, both with positive and negative spatial trends. The findings of this study will improve understanding of climatic trends and variability, leading to a better understanding of their impacts and informing the development of effective response strategies in the study area.