Central African moisture recycling and forests for resilience

Forests of Central Africa and the Congo Basin are a key component of the water security of local communities and economies. However, forests are mostly valued due to their mitigation potential and as part of net-zero discourse prioritised by global processes such as COP (WWF, 2025). Here we seek to demonstrate the important role regional forests can play through a water lens.

This comparative study explores the under-studied mechanism of evapotranspiration as a driver of rainfall onset in Central Africa and the Congo Basin. This is often assumed to be weak as evapotranspiration is relatively high throughout the year (Cook & Vizy, 2022). We test whether this is actually the case by following the rainforest-initiated shallow convection moisture pump for the onset of Amazon rainfall from (Wright et al., 2017). While both are key sites of tropical convection and moisture recycling there are indications that the rainfall dynamics in these two forested regions are quite different and have very different moisture recycling characteristics (Wunderling et al., 2022). Along with initiation we also investigate wet season maintenance and calculate moisture recycling through climatological and wet/dry composite seasons and examine three latitudinal bands spanning Central Africa and the Congo Basin with different vegetation characteristics.

We show that latitude bands in Central Africa have different moisture recycling climatologies by calculating precipitation moisture recycling using a bulk moisture recycling model driven by ERA5 reanalysis. While this partitions rainfall from local and remote moisture sources, to partition atmospheric moisture we use measurements of isotopologues in vapor from satellites including the Tropospheric Emission Spectrometer (TES), TRopospheric Ozone and its Precursors from Earth System Sounding (TROPESS) and the Tropospheric Monitoring Instrument (TROPOMI) to contextualise the seasonal recycling signal with changing levels of transpired moisture in the mid- to lower-troposphere. We use Moderate Resolution Imaging Spectroradiometer (MODIS) and Sentinel-3 to track evapotranspiration, and Sentinel-3 Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) and leaf area index (LAI) as measures of forest primary productivity and improved vegetation health. We also use atmospheric fields from ERA5 reanalysis that show evolving stability, convergence and moisture availability.  

This study supports a more holistic understanding of rainfall in Central Africa and how forests are linked with the local climate system by testing mechanisms linking vegetation and rainfall dynamics This is invaluable information for those wanting to protect the forest or understand how local rainfall and forest change might be linked in a changing climate.

This work is part of Forests For Resilience, an EO Science for Society project funded by the European Space Agency.