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Extreme Rain: Comparing Climate Models

Source: Bill Collins and Dan Hawkes

Bill-Collins-PortraitIt is difficult to quantify the cost of extreme-climatic-event impacts on human population, but it is certain that extreme events result in severe damage to property, destruction of environment, and loss of life. The occurrence of extreme rainfall that causes floods and landslides is underestimated in Global Climate Models (GCM), and this bias can affect decisions at both the individual and the community level.

ESD climate scientists Daniele Rosa and Bill Collins (ESD CCS co-head) recently analyzed subdaily precipitation data relative to the Southeastern U.S. from gridded-rain-gauge measurements, conventional global climate models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive, and a multiscale GCM. They found that GCMs overestimate the incidence of middle rainfall events and underestimate the incidence of no, little, and heavy rainfall events. Moreover, GCMs overestimate the persistence of heavy precipitation and underestimate the persistence of no and light precipitation. In general, GCMs with suppression mechanisms in the treatments of convective precipitation compare best with rain-gauge-derived data and should be trusted more than other models when assessing the risk from extreme precipitation events.

Figure 1. Observationally derived and simulated (top) fraction of total rainfall and (bottom) 90 v in relation to local time, calculated from data for latitudes (left) 30 to 34ıN and (right) 36 to 40ıN, and longitudes 265 to 280ıE, from May to August, 1996 to 2001

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Citation: Rosa, D., and W.D. Collins (2013), A case study of subdaily simulated and observed continental convective precipitation: CMIP5 and multiscale global climate models comparison. Geophys. Res. Letters, 40 (22), 5999-6003; DOI: 10.1002/2013GL057987.

Funding: NSF