On the Propagation of Convectively Coupled Kelvin Waves From Africa to the Indian Ocean

The composite evolution of Convectively Coupled Kelvin Waves (CCKWs) is studied as they move from Africa to the Equatorial Indian Ocean. Over Africa, the East African Highlands (EAH) weakens the convective coupling of CCKWs while steering the lower-tropospheric part of CCKWs northwards, which seems analogous to the trapping of Kelvin waves at an eastern boundary. Despite this disruption, the mid-to-upper-tropospheric part of CCKWs shows a coherent eastward propagation across EAH. This weakened upper part of CCKWs arrives over the Western Equatorial Indian Ocean (WEIO) after 2 days, inducing a mid-tropospheric ascent. Rainfall and the lower tropospheric westerlies are enhanced over the next day aloft a warm pool in the WEIO, although the CCKW signal from Africa starts losing its dynamic structure therein.