Albedo changes after fire as an explanation of fire-induced rainfall suppression

Abstract

Observational evidence of rainfall suppression by fire has recently been documented in African drylands, but the underlying mechanism remains poorly understood. Here we investigate the extent to which fire-induced changes in latent heat flux and albedo may inhibit boundary layer predisposition to convective rainfall. We use Modern-Era Retrospective analysis for Research and Applications, Version 2 reanalysis data from the Kalahari region of Southern Africa to drive a low-dimensional boundary layer growth model. We find that both increased albedo and, to a lesser extent, increased latent heat flux could result in less convective rainfall. The sensitivity to land surface feedbacks is higher earlier in the dry season and at drier sites. Finally, using Moderate Resolution Imaging Spectroradiometer fire and albedo data, we present novel evidence that increases in albedo after fire, or brightening, are common in regions receiving less than 850 mm of precipitation annually. This supports the idea that fire-induced surface brightening is responsible for observed rainfall deficits after fire.