MJO Teleconnections over East Africa in General Circulation Models: A Study of the Recent Past and the Future

East Africa is a region highly vulnerable to disruptions caused by climate variability and change. Understanding drivers of climate variability ranging from intraseasonal to multidecadal timescales is crucial. Madden Julian Oscillation (MJO) is a dominant driver of subseasonal variability in the region. The goal of this study is to examine the fidelity of MJO teleconnections to East African rainfall in the Coupled Model Intercomparison Project (CMIP) suite of global climate models (GCMs). We employ CMIP5 and CMIP6 models that have a realistic MJO representation. This is done while considering the background mean ENSO states that are shown to interact with MJO and yield periods of high precipitation intensity during an El Nino. We test the hypothesis that the El Nino teleconnection to East African boreal fall rainfall can be mediated by MJO. We formulate MJO teleconnection diagnostics, including pattern correlation, intra-phase consistency, and persistence, in order to assess rainfall impacts and dynamical as well as thermodynamical mechanisms in the historical simulation of the models. Based on these results, future teleconnections under RCP 8.5 and SSP5-8.5 scenario of realistic MJO models are further examined. MJO wind circulation that is linked to MJO teleconnections has previously been shown to decrease in the future global warming scenarios. We examine the extent of this MJO teleconnection weakening under different ENSO states and its consequent effect on East African rainfall. We postulate that this could potentially decrease MJO modulation of El Nino impacts, hence leading to a decline in El Nino-related seasonal wetness in the future.