Mapping Rainfall Variability over Eastern and Southern Africa

Analysis on the CHIRPS-v2 gridded rainfall data revealed a high-resolution spatio-temporal pattern of rainfall variability in the region largely lacking weather stations.

Fig. 8 Monotonic trends for annual rainfall (mm year-1) in Eastern and Southern Africa (ESA) region for 1981–2017 period (a) and zones with significant (p < 0.1) increase or decrease (b)

Francis Kamau Muthoni (IITA) recently published a paper on the use of Climate Hazards Group Infrared Precipitation with Stations (CHIRPS-v2) gridded rainfall data. Following the validating its applicability in comparison with in situ rainfall gauge data over Eastern and Southern Africa region, Francis and colleagues analyzed the spatial-temporal trends and variability of rainfall over last 37 years (1981 to 2017).

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 37 years (1981 to 2017) was validated against gauge observations (N = 4243) and utilized to map zones experiencing significant monotonic rainfall trends. Standardized 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 (β = 0.99) and variability (γ = 0.8). Two contiguous zones with a significant increase in annual rainfall (3–15 mm year−1) occurred in Southwest Zambia and in Northern Lake Victoria Basin between Kenya and Uganda. The most significant decrease in annual rainfall (− 20 mm year−1) was recorded at Mount Kilimanjaro in Tanzania. Other significant decreases in annual rainfall ranging between − 4 and − 10 mm year−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 the amount of rainfall that can complement the sparse rain gauge network in rain-fed agricultural systems in the ESA region. The observed spatial-temporal trends and variability in rainfall are an important basis for guiding targeting of appropriate adaptive measures across multiple sectors.

Muthoni, Francis Kamau, Vincent Omondi Odongo, Justus Ochieng, Edward M. Mugalavai, Sixbert Kajumula Mourice, Irmgard Hoesche-Zeledon, Mulundu Mwila, and Mateete Bekunda. “Long-term spatial-temporal trends and variability of rainfall over Eastern and Southern Africa.” Theoretical and Applied Climatology (2018): 1-14.