Figure 2.3: Annual average precipitation and temperature, averaged over the region for (a) temperature, (b) precipitation (NCEP) and (c) precipitation (JapRe)
There is considerable interannual variability in the East African climate, with greater interannual variability being associated with the short OND rains than the long MAM rainy season (Camberlin and Philippon 2002). There are two key modes of interannual variability in the region. ENSO is the first. The documented teleconnection with ENSO is both direct (atmospheric teleconnections) and indirect (through the response of the Indian and Atlantic Ocean basins) (Giannini et al. 2008). The strength of this interannual relationship is strongest in the short OND rains, when there is a positive relationship between South Pacific circulation variability and East African precipitation that is statistically significant at the 99% confidence level. However, there is also statistically significant (at the 98% level) relationship with the long MAM rains; in this case the relationship exhibits a negative correlation with the long rains over East Africa decreased during El Nino events (McHugh, 2006). McHugh (2006) demonstrates that during El Nino events outbreaks of moist South Atlantic westerly flows over East Africa are increased. These anomalous westerlies during El Nino episodes prevent
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