A multi-decadal analysis of westerly moisture transport events (WMTEs) in Equatorial East Africa

Understanding precipitation variability and extremes in Equatorial East Africa is vital for ensuring water and food security and mitigating the socioeconomic consequences of extreme events. Previous research has shown that sub-seasonal precipitation variability in this region is closely related to the wind direction, with precipitation more probable on days where the wind blows anomalously from the west, advecting moisture from the Congo basin. However, the exact nature of the westerly circulation and the conditions under which it forms are not fully understood. Here, we present a multi-decadal analysis of East African westerly winds. We use methods developed from studies of atmospheric rivers to objectively identify “westerly moisture transport events” (WMTEs), facilitating new insights into the seasonal distribution and importance of these westerlies, the regions within Eastern Africa where they occur, and the role of both the Madden-Julian Oscillation and tropical cyclones in their development. Finally, we also investigate the role of WMTEs as drivers of regional sub-seasonal precipitation variability.