Understanding Drivers of Precipitation Variability in East Africa to Improve Climate Modeling and Predictions

Climate variability can have significant impacts on precipitation in East Africa, leading to disruptions in natural and agricultural systems, human health, food and water security, and affecting the lives of tens of millions of people. Interannual and subseasonal variabilities are critical components of total rainfall variability in the region. Understanding the dynamics of their influence on East African precipitation is vital for improvement of climate model projections and subseasonal-to-seasonal forecasts. Global Climate Models (GCMs) are highly valuable tools used to study past, present and future climate all over the world, yet the performance of these models is notoriously weak over much of tropical Africa, including East Africa. To improve this situation, a better understanding of rainfall teleconnections of important climate drivers of variability is coupled with a process-oriented investigation of East African rainfall dynamics in GCMs. This work is undertaken in three separate studies. The first study examines the El Niño Southern Oscillation, a crucial driver of interannual rainfall variability, and its teleconnections to summer East African rainfall in a process-based study of GCMs. Specifically, the role of the Tropical Easterly Jet (TEJ) is examined as it is found to explain a majority of the inter-model variability in the ENSO teleconnections in this season. The second study aimed to understand the modulation of East African boreal fall rainfall due to the combined effect of the Madden-Julian Oscillation (MJO), a major subseasonal variability mode, and ENSO. Daily rainfall responses were found to depend on MJO phase and its interaction with ENSO. On a seasonal scale, the MJO can mediate El Niño’s seasonal impact on rainfall. The third study assessed the fidelity of MJO teleconnections to boreal fall rains in GCMs, as well as the interacting influence of ENSO, a connection relevant for both forecasts and long-term climate projections