92nd American Meteorological Society Annual Meeting (January 22-26, 2012)

Wednesday, 25 January 2012: 10:30 AM
Is Heavy Rain More Realistic in a Very High Resolution Climate Model?
Room 354 (New Orleans Convention Center )
Elizabeth J. Kendon, United Kingdom Meteorological Office, Exeter, Devon, United Kingdom; and N. Roberts, M. J. Roberts, and C. Senior

The realistic representation of rainfall on the local scale in climate models remains a key challenge. Realism encompasses the full spatial and temporal structure of rainfall, and is a key indicator of model skill in representing the underlying processes.

This study examines whether rainfall is more realistic in a very high resolution (1.5km) climate model compared to a coarser resolution (12km) regional climate model. This is the first time a convection-resolving model has been run for a 10-year period over a region of the UK, allowing the characteristics of rainfall to be evaluated in a climatological sense.

We find that rainfall over the UK is much more realistic in the 1.5km model compared to the 12km model. Although the 1.5km model has a tendency for heavy rain to be too intense, it gives a much better representation of its duration and spatial extent. It also gives a better representation of the occurrence of dry spells and the diurnal cycle of convection, which are poorly represented in coarser resolution climate models. This suggests that the 1.5km model is giving a better representation of the underlying processes, and hence gives us more confidence in its projections of future change.

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