Analysing Changes in Rainfall Dynamics: Onset and Precipitation Probability in Tanzania

This study investigates the changes in rainfall dynamics in Tanzania, focusing specifically on the onset and precipitation probability of rainy seasons. The research stems from growing concerns about climate variability in East Africa, which has significant implications for agriculture, water resources, and food security. Despite Tanzania's heavy reliance on rain-fed agriculture, there is a lack of understanding regarding how rainfall patterns are shifting, impacting both local farmers and national policies. Utilizing time series analysis and the Instat Climatic tool for the assessment of rainfall onset dates, Mann-Kendall (MK) test, Sen’s slope estimator (Q ₂ ) for onset dates trend analysis and Markov chain model for precipitation probability, we analysed historical rainfall data from 27 weather stations (regions) across Tanzania. Our findings indicate a noticeable shift in the onset of the rainy seasons, with variability in the trends of rainfall onset across different regions. Furthermore, a consistent pattern wherein southern and central regions tend to witness prolonged waiting times for the start of the rainy season and increase in the probability of rain following a rainy day (rr), while the probability following a dry day (rd) remains relatively stable. These results highlight critical adaptations necessary for agriculture and water management strategies in Tanzania. Late rainfall onset could hinder crop growth, particularly for maize and other staple foods, leading to potential food shortages and economic instability if no adaptive measures are implemented. The findings underscore the need for interdisciplinary collaboration to develop robust frameworks that integrate climatic forecasts into agricultural planning. Understanding the shifting dynamics of rainfall is essential not only for Tanzania but also for other regions facing similar climate challenges, emphasizing the interconnectedness of climate change impacts on food systems and livelihoods around the world.