Rainforest-initiated wet season onset over the southern Amazon
Abstract
This analysis provides compelling observational evidence that rainforest transpiration during the late dry season plays a central role in initiating the dry-to-wet season transition over the southern Amazon. Transpiration first activates shallow convection that preconditions the atmosphere for regional-scale deep convection, rather than directly activating deep convection as previously proposed. Isotopic fingerprints in atmospheric moisture unequivocally identify rainforest transpiration as the primary moisture source for shallow convection during the transition. This "shallow convection moisture pump" thus depends on high transpiration rates during the late dry season, affirming the potential for climate and land use changes to alter or disrupt wet season onset in this region.