Seminar - Quantifying robust changes in extreme rainfall: recent advances in downscaling techniques for hydrological extremes

Although a large published literature exists on the strengths and weaknesses of downscaling methods for different climatic variables, in different regions and seasons, little attention is given to the choice of downscaling method when examining the impacts of climate change on hydrological systems and, in particular, extremes. There is a need to move away from comparison studies into the provision of decision-making tools for planning and management that are robust to future uncertainties; with examination and understanding of uncertainties within the modelling system. This talk will examine the downscaling concept, the limitations of downscaling and new downscaling methods for extreme rainfall.

Regional Climate Models (RCMs) simulate the magnitude and spatial pattern of observed daily extreme rainfall events more reliably than GCMs but still underestimate extreme rainfall in relation to observations. All RCMs have deficiencies in their representation of the magnitude and spatial variability of daily rainfall extremes. Though boundary forcing has the greatest impact on the magnitude of extremes in RCM simulations, changes in RCM specific formulations also lead to local-scale differences in biases and response to forcing. Recent research also shows that RCM simulation of extreme rainfall is better for long (e.g. 5 to 10 days) rather than short duration events and is best for the winter season when extreme rainfall is mostly associated with synoptic and mesoscale precipitation structures. Simulation of extreme rainfall is particularly poor in summer when convection dominates.

This presentation will evaluate the ability of RCMs to represent extreme precipitation processes and ask 'which projected changes to extreme rainfall are robust to 'the climate model and observational uncertainties?'. Results from a new NERC-funded project, CONVEX, which is investigating model deficiencies in the simulation of extreme rainfall will then be presented. This is, for the first time, running a high resolution (1.5km) RCM over the UK to investigate the effects of model resolution on the simulation of extreme precipitation and to produce new estimates of future change to convective extremes for pluvial flood risk.

Chair: Dr Alex Densmore

About Presenter

Dr Hayley Fowler is Professor of Climate Change Impacts, at the School of Civil Engineering and Geosciences, Newcastle University.

Please contact the Chair of this seminar if you are interested in meeting the speaker.

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