Speaker: Anna Mackie (St Andrews)
Title: More frequent and more intense convective downdrafts with warming in km-scale simulations: what are potential implications for cloud feedback estimates?
Abstract: The response of clouds to a warming atmosphere is uncertain, in part due to the length scales of tropical motions – which influence cloud formation – being smaller than those typically resolved in global climate models (GCMs). In these models, small-scale upwards and downwards motions need to be inferred from resolved, larger-scale motions, introducing uncertainty. Here we use multi-year simulations of the west Pacific at convection-permitting resolution in present-day and warmer climates to show an increase in the frequency and intensity of downdrafts in convective cores. The explicit simulation of downdrafts leads to fundamental differences in cloud-circulation interactions compared to previous GCM studies. These changes may be sufficient to impact estimates of how clouds change with warming. In particular, we demonstrate that intensifying downdrafts may reduce the extent to which clouds cool the Earth system, with implications for future climate projections.