Article,

Extreme value modelling of daily areal rainfall over Mediterranean catchments in a changing climate

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Hydrological Processes, (2011)
DOI: 10.1002/hyp.8417

Abstract

Heavy rainfall events during the fall season are causing extended damages in Southern France catchments. A peaks-over-threshold model is developed for the extreme daily areal rainfall occurrence and magnitude in the fall over six Mediterranean catchments in Southern France. The main driver of the heavy rainfall events observed in this region is the humidity flux from the Mediterranean Sea. Reanalysis data are used to compute the daily humidity flux (FHUM) during the period 1958–2008, to be included as a covariate in the model parameters. Results indicate that the introduction of FHUM as a covariate in the model parameters can improve the modelling of extreme areal precipitation. The seasonal average of FHUM can improve the modelling of the seasonal occurrences of heavy rainfall events, while the daily FHUM values can improve the modelling of the events magnitudes. In addition, an ensemble of simulations produced by five different general circulation models are used to compute FHUM in future climate and hence to evaluate the impact of climate change on the heavy rainfall distribution in the selected catchments. This ensemble of climate models allows the evaluation of the uncertainties of climate projections. By comparison to the reference period 1960–1990, all models projects an amplification of mean seasonal FHUM from the Mediterranean Sea during the projection period 2070–2099, on average by +22%. This increase in the humidity flux leads to an increase in the number of heavy rainfall events, from an ensemble average of 2.55 events during the fall season in present climate to 3.57 events projected for the period 2070–2099. However, the projected changes have limited impacts on the magnitude of extreme events, with a 5% increase in the median of 100-year quantiles. Copyright © 2011 John Wiley & Sons, Ltd.

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