Environmental sensitivities of shallow-cumulus dilution – Part 2: Vertical wind profile

Abstract. This second part of a numerical study on shallow-cumulus dilution focuses the sensitivity cloud to changes in vertical wind profile. Insights are obtained through large-eddy simulations maritime and continental fields. In these simulations, speed initially uniform geostrophic strength shear subcloud layer varied. Increases cloud-layer (up 9 ms-1km-1) lead 40 %–50 % larger cloud-core rates compared their respective unsheared counterparts. When background speed, other hand, is enhanced by up 10 m s−1 subcloud-layer develops or prescribed, rate decreases 25 %. The sensitivities linked updraft properties entrained air. result lower velocities across all sets experiments with stronger reductions simulation (27 %–47 %). Weaker updrafts exposed mixing drier surrounding air for longer time period, allowing more entrainment occur (i.e., “core-exposure effect”). However, reduced velocities, concert increased turbulence, also assist widening humid shell cores, leading “core–shell shear, core-exposure effect dominates increases increasing shear. Conversely, when imposed, core–shell induce buffering effect. generally where weaker sensible heat fluxes narrower, tilted, and, therefore, suppressed cumuli imposed. Moreover, baseline turbulence case allows enhancement, resulting transition zones between cores environment,