Warming of the northern tropical Atlantic intensifies aridity in southeastern Africa

October precipitation in southeastern Africa (SEA) is crucial as it marks the initiation of agricultural and hydrological activities. This study investigates the mechanism linking warming sea surface temperature (SST) in the northern tropical Atlantic (NTA) to the observed decrease in October precipitation over SEA from 1981 to 2010. We investigate the underlying mechanisms using a series of observational data and confirm our results through numerical experiments. The results reveal a significant negative correlation between SEA precipitation and NTA SST anomalies. During this period, the Atlantic Multidecadal Oscillation transitioned from a cold to a warm phase, marked by notable warming in the NTA. The presence of a tropical heat source, in accordance with the Matsuno–Gill response, led to the baroclinic response over the SEA with an anomalous anticyclone/cyclone in the lower/upper level and corresponding descending motion, and resulted in a reduction in precipitation over SEA.