The death of an altocumulus cloud

Abstract

What causes altocumulus clouds to decay? To address this question, the authors examine an observational case study of a mid-level cloud that was measured during the Complex Layered Cloud Experiments (CLEX). The budget of liquid water reveals that the cloud was not dissipated by fallout of precipitation. Rather, the largest contributor to decay of liquid water was subsidence drying. The strong link between subsidence and cloud lifetime is an important difference between altocumuli and boundary layer clouds. The net effect of radiative transfer on our cloud is unclear: liquid water was directly increased by radiative cooling, but this was offset by radiatively induced entrainment drying.