Increased Large-Scale Convective Aggregation in CMIP5 Projections: Implications for Tropical Precipitation Extremes

Convective aggregation refers to the clustering of convective events and occurs on a wide range of spatial scales. It has been suggested that the behavior of convective aggregation may change under global warming, with potential implications for future changes in precipitation extremes. Here, convective regions of the tropics are defined from a percentile threshold on gridded daily precipitation data and used to quantify large-scale convective aggregation in an ensemble of global climate models. Applying three separate indices for aggregation, it is found that large-scale convective aggregation increases in 17 of the 19 analyzed models under future warming. However, aggregation is found not to be correlated with tropical-mean precipitation extremes, either climatologically or with respect to the sensitivity to warming. The large model spread in aggregation indices across the ensemble suggests the possible utility of large-scale convective aggregation as a target for model evaluation.