Royal Netherlands Meteorological Institute

 
Research
Climate change in East Africa
Rwanda and Burundi (Region 8)
24 August 2007
Long-term fluctuations
Short-rains (October-December)
The time series plot for this area's precipitation anomalies show huge (≥ 1σ) positive anomalies, in common with the anomalies found in other regions around Lake Victoria's proximity. While the early 20th century observations are less reliable, the huge anomalies reported after the turn of the century are more realistic. The models give an indication for continued wet conditions in this area during the 21st century.
Region 8 short-rains precipitation differences from the 1901-1950 mean [σ] with a ten-year running mean in observations (black bars) and selected climate models. The blue line shows the multi-model ensemble mean. The darker (lighter) shading show 1σ (2σ) from the mean.

Region 8 precipitation differences (σ) from the 1901-1950 mean in twelve GCM simulations.
Long-rains (March-May)
The time series plots show that the long-rains fell in abundance during much of the 20th century. The models project a continuation of wetter conditions (regular upward trend) in this area throughout the 21st century. However, the signal-to-noise ratio in the model projections for this season's precipitation is relatively low.
Same as the above figure but for long-rains season.

Region 8 precipitation differences (σ) from the 1901-1950 mean in twelve GCM simulations.
Annual cycle
The annual cycle show a clear link between this region and areas further south. Atypical of near-equatorial regions, substantial rainfall amounts (> 4mm/day) are received in this area from January to March. The models are able to capture the annual march of precipitation in this area, albeit with clear wet biases. The models agree in projecting an increase in mean monthly precipitation almost throughout the year. However, from September to December, the HadGEM1 chooses a different path from the rest of the models (it projects drier conditions instead).
Region 8 annual cycle. The observations are shown by bars. Model simulated annual cycle is shown by the dotted line (open diamond) for the 20th century (around 2100). For each model, the line segment displays the simulated deviation (from 20th century) in mean monthly rainfall. Positive (negative) deviations are indicated by line segments pointing upwards (downwards) from the dotted line.

Region 8 annual cycle.