Microphysics Dominates Sub‐Cloud Rain Evaporation in Trade Cumuli Over Barbados

Abstract This study investigates the microphysical and thermodynamic influences on North Atlantic trade‐cumulus rain evaporation in the sub‐cloud layer over Barbados from January to November 2020. Using radar observations and a 1‐D model, the results reveal that microphysical properties, namely geometric mean diameter (D g ) and raindrop concentration, primarily control evaporation processes under conditions of limited thermodynamic variability. Thermodynamic factors like cloud base height and relative humidity exert a smaller influence due to their narrow observed ranges. Small D g leads to rapid increases in rain evaporation fraction (REF), as small drops evaporate completely, while larger D g yields slower, more gradual REF changes. Frequent weak‐rain cases reduce the mean evaporation flux, whereas infrequent intense‐rain events substantially enhance it. These findings highlight the pivotal role of microphysical variability in shaping sub‐cloud evaporation in this trade cumulus regime, while thermodynamic effects may be more important in other environments.