Modulation of East African Boreal Fall Rainfall: Combined Effects of the Madden–Julian Oscillation (MJO) and El Niño–Southern Oscillation (ENSO)

Abstract Climate variabilities can have significant impacts on rainfall in East Africa, leading to disruption natural and human systems affecting the lives of tens millions people. Subseasonal interannual are critical components total variability region. The goal this study is examine combined effects Madden–Julian oscillation (MJO), operating at a subseasonal time scale, El Niño–Southern Oscillation (ENSO), an modulation African boreal fall [October–December (OND)] rainfall, commonly called short rains. Composite analysis shows that daily responses depend MJO phase its interaction with ENSO state. In particular, generally stronger under Niño conditions relative neutral La Niña conditions, increased potential for precipitation excesses during wet phases Niño. There evidence both dynamic thermodynamic mechanisms associated these impacts, including increase westerly moisture transport easterly advection temperature moist static energy. Seasonal frequency intensity contribute notably seasonal anomaly. This suggests mediate Niño’s impact OND Africa.