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Modeling Daily Intense Rainfall Events over Africa

Paper Reviewed
Cretat, J., Vizy, E.K. and Cook, K.H. 2014. How well are daily intense rainfall events captured by current climate models over Africa? Climate Dynamics 42: 2691-2711.

According to Cretat et al. (2014), "the capability of state-of-the-art climate models to capture the main observed characteristics of daily intense rainfall events has not been quantified over Africa," and they thus state that a clear evaluation of the models' "strengths and limitations to simulate them is necessary." And so, in an effort to provide this much-needed evaluation, Cretat et al. analyzed regional climate model (RCM) simulations at 90- and 30-km-long intervals, together with output from four atmospheric general circulation models (AGCMs) and coupled atmosphere-ocean general circulation models (AOGCMs) of the Climate Model Intercomparison Project 5 (CMIP5).

The three U.S. researchers determined from their analysis that both sets of RCM simulations "accurately capture the spatial and temporal characteristics of intense events," but they report that they also (1) "tend to overestimate their number" and (2) "underestimate their intensity." In addition, they found that (3) "the majority of the AGCMs and AOGCMs greatly overestimate the frequency of intense events, particularly in the tropics," that they (4) "generally fail at simulating the observed intensity," and that they (5) "systematically overestimate their spatial coverage."

These findings, in the words of Cretat et al., indicate that "state-of-the-art climate models still cannot realistically simulate daily intense rainfall events with high accuracy," suggesting that there are "physical parameterization deficiencies" for the ranges of horizontal resolution used in their study, while further stating that "the fact that both RCM and, to a greater extent, GCM simulations overestimate the frequency of intense daily rainfall events suggests that erroneous or, at least, overly simplified assumptions are used in the convective schemes of most climate models."

Reviewed 24 September 2014