Precipitation clusters in the tropics exhibit increases in extreme size and intensity under global warming in CMIP6 models

The intensification of extreme precipitation in the tropics is associated with an increase in organized convective systems. The quantitative details of this increase are examined using the occurrence frequencies of contiguous precipitating areas or precipitation clusters. In the tropics, large clusters are organized precipitating systems such as mesoscale convective systems or tropical cyclones. Precipitation clusters are characterized by size and cumulative precipitation (cluster power). This study analyzes the probability distributions of cluster size and power for ten CMIP6 models with three-hourly precipitation output from both historical and end-of-century SSP585 simulations. There is a universal agreement among models that the frequency of large and intense precipitation clusters increases with global warming. In the SSP585 simulations, the occurrence probability of the precipitation clusters with very large amounts of integrated precipitation increases by at least five times. The spatial distribution of cluster centroids (precipitation-weighted centers of mass) suggest that the biggest increases are found in the Western pacific, the Indian subcontinent, central and east pacific ITCZ as well as central South America. Much of this spatial pattern of increase is reproducible using a Clausius-Clapeyron scaling of the current climate distribution of precipitation clusters.