Linking regional changes in the intensity distribution of daily tropical precipitation to changes in large-scale circulation and convective inhibition

Global warming is expected to change the intensity distribution of daily tropical precipitation, with an increased frequency of heavy precipitation and reduced frequency of light precipitation. In general, this is likely to increase the risk of flooding, while also increasing the risk of long dry periods. However, on regional scales circulation change plays a major role in modulating this precipitation distribution change in climate model projections, so related climate change impacts will also be regionally dependent.

We propose a simple physical framework based on the dry static energy budget which explains regional daily precipitation distribution change in terms of changes in two physical drivers: large-scale circulation and time-mean convective inhibition (CIN). In this framework, increased CIN under global warming tends to reduce the frequency of convection, leading to a greater ‘recharge’ of instability between convective events, and consequently greater ‘discharge’ of latent heating (precipitation) during each event. Large-scale circulation regulates the speed of this recharge of instability via dry static energy flux convergence or divergence, and its change under warming is very regionally dependent. Changes in regional time-mean tropical precipitation are closely related to changes in large-scale circulation, so this framework also provides a physical link between changes in time-mean precipitation and changes in the daily intensity distribution of precipitation in each tropical region.