Periodicity in monthly rainfall derived from wavelet analysis.

(A) Rainfall recordings in the Mara were derived from 15 gauges (Eq 3 in S1 Text) during the period 1965–2015. (B) Rainfall in Narok Town in Kenya was recorded during 1913–2015. The wavelet power spectrum (bias-corrected and normalized by the variance) for varying rainfall cycle periods is given for each month and year. Areas of high power are indicated in warm colours (red), whereas areas of low power are indicated in cold colours (blue). The semi-transparent area represents the cone of influence, where edge effects become important due to padding with zeros at the end of the time series. The power in this region is reduced. Significantly higher wavelet power spectra than expected under a red-noise process AR(1) (lag ‒ 1 = 0.05 for the Mara and lag ‒ 1 = 0.16 for Narok Town) are encircled by black lines.