Precipitation Clusters | Neelin Group

Extreme Tropical Precipitation Clusters Show Strong Increases in Frequency Under Global Warming

Risk ratios for precipitation rate integrated over the cluster— the cluster power— for the probability of exceeding a given cluster power in high emission end-of-century global warming scenario (SSP5-8.5, 2091-2100) relative to the probability in historical (2005–2014) simulations. Different colors show different climate models. The top panel has a linear risk ratio scale for easy visualization of the rapid increase in probability for the most extreme clusters. The inset displays the same figure with a log risk-ratio scale, to show the increase is approximately exponential with a characteristic scale (slope of the approximately linear range on the bottom panel). From Dulguerov et al. (2021).

Precipitation clusters are spatially contiguous precipitating regions, including organized precipitating systems. Dulgerov et al (2021) assess the changes to probability distributions of tropical precipitation clusters in climate models from the Coupled Model Intercomparison Project Phase 6 ensemble. The frequency of large and heavily precipitating clusters increases significantly in the warmer climate, with the risk ratio increasing exponentially for the largest clusters. The spatial pattern of the projected changes in the ensemble mean is captured to a first approximation by Clausius-Clapeyron scaling of water vapor saturation with increased temperature. However, individual models can exhibit super-CC increases in scaling of large cluster probabilities.