Deforestation Impacts on Clouds and Precipitation Over Borneo Vary Across the Diurnal Cycle

Abstract The impact of tropical deforestation on clouds and precipitation remains uncertain due to complex interactions between land and atmospheric processes on convective and mesoscales. Here, we examine convective‐scale processes controlling the short‐term atmospheric response to deforestation over Borneo using multi‐day large eddy simulations. Replacing tropical forests with oil palm plantations reduces surface roughness, leading to less efficient surface–atmosphere exchange, warmer soils, and a cooler but moister near‐surface atmosphere. To examine how this impacts cloud formation, we identify and track thousands of clouds to quantify shifts in tropical convection across the diurnal cycle. Overall, deforestation suppresses shallow‐to‐deep convective development, though the shallow cumuli which do form start lightly raining earlier in the day due to increased low‐level moisture. However, this reduction in shallow cloud cover is not spatially uniform: in areas where the deforestation gradient is strong, midday cumuli are enhanced by mesoscale vegetation breezes. Deforestation also weakens sea breeze‐driven moisture convergence, leading to the relative enhancement of terminal congestus over deep convection and a shift in precipitation onset toward later in the evening. Our findings emphasize that deforestation impacts vary diurnally depending on cloud type and interactions with mesoscale phenomena, as well as spatially depending on the location relative to deforested regions. Although this work focuses on the transient convective response to deforestation, we suggest the multi‐scale variability of these responses should be considered when assessing longer‐term deforestation impacts on clouds, rain, and climate.