CEH / Met Office Hadley Centre: Input into an impacts model

Objectives: To estimate river flow changes across the river network of the UK.

• How they used UKCP09 dummy data

Regional Climate Model (RCM) data for baseline and future time periods and for all the ensemble members, were downscaled to a
1 km resolution (the required resolution) and input into the Grid–to-Grid hydrological model. The downscaling procedure used high resolution information from a standard average annual rainfall dataset.

A change in river flow from baseline to future was calculated on a
1 km grid across the UK for each ensemble member.

A map showing estimated changes in peak annual average flow across the UK was developed for each ensemble member projection.

• What could they do next?

• The next step would be to decide how to present the data. It could be presented as graphs for a particular location showing the projected change in river flow associated with each ensemble member, or as a map of UK rivers showing the percentage change in peak river flow derived from averaging across all the ensemble members.
• They could compare the regional climate model changes in the context of the full IPCC AR4 range of changes.
• The results could be communicated through reports, publications and refereed scientific journals.

• What they learnt about UKCP09

• The RCM data were the only UKCP09 output that provided information that was transient and at the required temporal resolution while being spatially consistent across the grid cells.
• Use of direct RCM output encouraged a critical assessment of the applicability of the resulting flow changes. The lack of probabilities associated with these projections avoided the possibility of unquestioning application of probabilities to determine absolute risks.
• When RCM data are used in preference to the probabilistic data a simple analytical framework for assessing the likelihood of the various outcomes is not available. Expert judgment is therefore required to assess the applicability of the results.
• There is only one emission scenario available through the RCM data (medium).
• The sheer volume of RCM data makes the information hard to handle.
• The RCM data are not available in what would typically be thought of as a user-friendly format. For this exercise it was only available in binary, post-launch it should also be available in .csv.
• It was noted that the RCM models a 360-day year with 30 days in each month so it is hard to compare to observations.
• 11 plausible results of river flow makes analysis more complex.

• Contact details: Vicky Bell, Centre for Ecology and Hydrology; Richard Jones, Met Office Hadley Centre (Reading Unit).

• Downoad the full report (pdf, 210 KB)
• LINK on the BADC website
• Bell, V.A., Kay, A.L., Jones, R.G., Moore, R.J. (2007) Use of a grid-based hydrological model and regional climate model outputs to assess changing flood risk. International Journal of Climatology, 27, 1657-1671. doi:10.1002/joc.1539.