UKCP18 Climate Projections: impacts on improved rainfall projections and extremes

Following our UK Climate Projections 2018 blog, below we consider an important aspect of the new UKCP18 projections: improved rainfall projections and extremes.

Rainfall intensity is of key importance to many: it affects urban drainage, sewerage design, surface water flooding, erosion risk and water resources, among a wide range of other aspects. It matters to those who own or manage assets, infrastructure, urban and rural environments.

Today’s design guidance for engineers, planners and environmental managers has been developed using historic rainfall intensity data. In the flood risk community, there has been guidance provided on how to ‘uplift’ rainfall amounts for climate change, but it has been developed from relatively coarse-scale climate models. So, this means we are not very certain how rainfall intensity over short durations might change in the future.

Excitingly, this is changing with the advent of new climate models that are now able to resolve the processes that cause the high-intensity rainfall over the UK. This is mainly due to:

  • Increased computing power which is able to run climate models at a much finer resolution
  • Some cutting-edge science in the Met Office Hadley Centre.

New 2.2km resolution

In UKCP18’s projections, there will soon be the opportunity to use data from a range of weather variables, including rainfall, that is from a model with 2.2km spatial resolution – previously projections were from a 25km resolution model.

JBA staff were involved in a water industry research project using an experimental version of this high-resolution model run at 1.5km resolution, giving us key insight into the application of its projections and data.

UKCP18 high-resolution data will be produced for 10 model runs, allowing a better estimation of uncertainty in the projections to be made. This presents many opportunities – we will for the first time be able to estimate the impact of future rainfall intensity on a whole host of systems and environments across the UK.

Higher resolution climate modelling and new climate modelling science also give us better estimates of changes in extremes. Often, when we’re trying to understand what the future weather will bring, we’re interested in whether droughts will get worse, heatwaves will increase, flooding will change or whether there will be changes in the seasonal patterns of weather events for example.

Improved model projections from UKCP18 will allow us to get better estimates of changes in extreme weather events, that might be a few hours, days or weeks long.

Want to know more?

Email Murray Dale for more information on rainfall projections and UKCP18. Find out more about our work in this area on our climate resilience web page.

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