Long-term spatial-temporal trends and variability of rainfall over Eastern and Southern Africa

This study investigates the spatial-temporal trends and variability of rainfall within East and South Africa (ESA) region. The newly available Climate Hazards group Infrared Precipitation with Stations (CHIRPS-v2) gridded data spanning 37years (1981 to 2017) was validated against gauge observations (N=4243) and utilised to map zones experiencing significant monotonic rainfall trends. Standardised annual rainfall anomalies revealed the spatial-temporal distribution of below and above normal rains that are associated with droughts and floods respectively. Results showed that CHIRPS-v2 data had a satisfactory skill to estimate monthly rainfall with Kling-Gupta efficiency (KGE=0.68 and a high temporal agreement (r=0.73) while also preserving total amount (beta=0.99) and variability (gamma=0.8). Two contiguous zones with significant increase in annual rainfall (3-15mmyear(-1)) occurred in Southwest Zambia and in Northern Lake Victoria Basin between Kenya and Uganda. The most significant decrease in annual rainfall (-20mmyear(-1)) was recorded at Mount Kilimanjaro in Tanzania. Other significant decreases in annual rainfall ranging between -4 and -10mmyear(-1) were observed in Southwest Tanzania, Central-South Kenya, Central Uganda and Western Rwanda. CHIRPS-v2 rainfall product provides reliable high spatial resolution information on amount of rainfall that can complement sparse rain gauge network in rain-fed agricultural systems in ESA region. The observed spatial-temporal trends and variability in rainfall are important basis for guiding targeting of appropriate adaptive measures across multiple sectors.