Is intense coastal rainfall in the Netherlands better simulated at a finer grid scale?

We will present a quantification of how the North Sea surface temperature (SST) may alter the spatial distribution of precipitation extremes within the Netherlands. Recent research has shown that the coastal area climate experiences a strong dependency to SST under specific atmospheric circulation conditions. With a model of intermediate resolution (in both time and space) results obtained for August 2006 showed already that the influence of a warm North Sea can be significant, even leading to an increase in coastal precipitation of 15 % per degree warming of the North Sea (Lenderink et al. 2008). However, these models of intermediate resolution have difficulties in simulating the right amount of precipitation. On a 25 km resolution, the precipitation is underestimated in summertime circumstances for coastal area in the Netherlands. The summertime precipitation is characterized by convective showers, which are difficult to capture at this resolution. A new generation of regional climate models, which use the non-hydrostatic approach, have the ability to simulate precipitation on a resolution as small as 1 km. This is achieved by actually resolving the microphysics of the atmosphere instead of parameterizing convection. It is also hypothesized that precipitation extremes are much better captured. With the results of the simulations presented extreme events of climate scenarios for the Netherlands will be improved in many aspects. This will provide better quantification of changes in variability at different time scales and a better representation of the uncertainty.