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distribution within the Netherlands. Indeed, over the last 55
years already a trend in the difference between the coastal
zone and inland area is observed. The coastal area has
become wetter compared to the inland area (Figure 2). Also,
the period with the largest difference between coastal zone
and inland area has shifted from the autumn season to late
summer.
From daily observations the dependency of precipitation
intensity on the sea surface temperature can be derived
(Lenderink et al. 2009). Also high resolution model
simulations can be used to derive these dependencies on a
case basis. Both show that under specific circulation
conditions (mostly cold cyclonic conditions) the dependency
can be large. In the coastal area up to 10-15 % more
precipitation could fall per degree temperature rise of the
North Sea.
Lenderink, G., E. van Meijgaard & Selten F., Intense
coastal rainfall in the Netherlands in response to high
sea surface temperatures: analysis of the event of
August 2006 from the perspective of a changing
climate. Clim. Dyn., 32, 19-33, 2009.
Van Ulden, A. P. & van Oldenborgh, G., Large-scale
atmospheric circulation biases in global climate model
simulations and their importance for climate change in
central Europe. Atmos. Chem. Phys. 6, 863–881, 2006.
4. Relation to Clausius-Clapeyron
Increases of precipitation with temperature are generally
found to be equal or lower than the Clausius-Clapeyron
relation. However, we show that for the shorter time scales
(hourly) and the local scale (coastal zone, station)
dependencies can be much larger. These stronger
dependencies are likely due to positive feedbacks in the
intensity of updrafts in the convective clouds (Lenderink and
Van Meijgaard, 2008) and locally strong dependencies of
sea surface evaporation on temperature (Lenderink et al.
2009).
5. A plea for high resolution modeling
The resolution in present-day state of the art regional climate
simulations is order 25 km (ENSEMBLES, Hewitt and
Griggs 2004). In addition, regional modeling systems do not
generally contain an ocean component, but obtain sea
surface temperatures from global model simulation directly.
In particular, for coastal seas temperature responses to
changing atmospheric conditions could therefore be strongly
underestimated. Thus, our present models only partly
resolve the processes that may lead to strong extremes on
the local (here and now) level. Considering the societal
relevance of these extremes we therefore make a strong plea
for high resolution (< 10 km resolution) coupled regional
modeling systems.
References
Held, I. M. & Soden, B. J., Robust responses of the
hydrological cycle to global warming. J. Clim. 19,
5686–5699, 2006.
Hewitt, C. & Griggs, D. Ensembles-based predictions of
climate changes and their impacts (ENSEMBLES). Eos
85, 566, 2004.
Lenderink, G., van Ulden, A., van den Hurk, B. & Keller, F.
A study on combining global and regional climate model
results for generating climate scenarios of temperature
and precipitation for the Netherlands. Clim. Dyn. 29,
157–176, 2007.
Lenderink G. & Van Meijgaard E. Increase in hourly
precipitation extremes beyond expectations from
temperature changes, Nature Geoscience, 1, 8, 511-514,
2008.