The impact of climate change on weather systems, extreme rainfall and flood episodes in the UK

Future extreme rainfall in the UK is expected to increase through anthropogenic climate change (Schaller et al. 2014) and flooding is considered the most significant climate-related risk to the UK. Flooding is often the direct response to high-intensity and/or long-lived rainfall episodes. The Pennine hills of northern England are particularly prone to flood events due to the relatively wet climate and steep sided valleys, which channel water very rapidly into the valley bottom, causing river levels to rise sharply. Severe flood events occurred in summertime 2012 through convective rainfall (i.e. thunderstorms) and wintertime 2015 through rainfall associated with Storm Desmond and Frank, resulting in many homes being flooded and more than £5 billion of damage.

Flooding is often the direct response to high-intensity and/or long-lived rainfall episodes. Traditional climate models struggle to simulate this type of rainfall because they cannot represent the processes controlling the triggering, organisation and maintenance of storms, particularly those associated with summertime convection (i.e. thunderstorms). Understanding these weather systems and predicting how they may change in the future remains a grand challenge in atmospheric science (Fowler and Ekstrom, 2009).

High-resolution regional climate models, where some of the key atmospheric processes such as convection are much better represented, offer a new solution to this long-standing problem (Prein et al. 2015). This type of model is currently used routinely for numerical weather prediction for the UK and recently we have gained the computational capacity to run these models for time periods useful for climate projections. A recent study by Kendon et al. (2014) illustrated that this new generation of climate model has a much improved representation of extreme rainfall events.

In this project the student will utilise state-of-the-art climate models to assess how the severity and frequency of extreme UK-wide weather events will change in the future and quantify changes in flood risk over the Pennine region. Specific objectives include:

• Assessing the mechanisms behind the changes in rainfall events. What type of weather causes severe rainfall events and how may the severity and frequency of these weather patterns change in the future?
• Evaluating the ability of the climate model to reproduce realistic flood-producing severe weather (intensity, duration, frequency and seasonality) using ground-based radar, surface meteorological and rain gauge observations
• Use existing hydrology and hydraulic models to assess how the extent, severity and probability of flood episodes in the Northern Pennines will change in response to future changes in extreme rainfall
• Utilisation of newly acquired river gauge measurements from the Calderdale river catchment to evaluate the hydrological and hydraulic models
• Working with industrial partners, specifically Environmental Consultant Thomas Mackay Ltd, to ensure the catchment and river processes are represented correctly in the hydrology models and identify how project outcomes could translate into the flood risk dialogue that is ongoing within the catchments.

The student will work under the main supervision of Dr Cathryn Birch, who is an Academic Research Fellow specialising in meteorology and climate modelling within the School of Earth and Environment. Dr Mark Trigg, an expert in hydrology, flood hazard and water related risk in the School of Civil Engineering, will co-supervise the project and provide flood models and links to project partners within the catchments. There is potential for travel to the United States to visit the National Centre for Atmospheric Research (NCAR), who are conducting parallel work on the changing patterns of rainfall in the US.


http://www.nercdtp.leeds.ac.uk/projects/index.php?id=560