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Monitoring changes in precipitation
01-09-2008
Observed worldwide
In the temperate regions in the Northern Hemisphere - to which northwest Europe belongs - precipitation increased, on average, by 5 to 10% within the 20th century. This increase is caused partly by the fact that warmer air can contain more water vapour. The increase in the strength of the westerly circulation also has played a role. For Europe as a whole, the intensity of extreme precipitation has increased in the past 50 years. Just as in many other regions in the world, the number of extremely wet days increased in many
places in Europe (Figure 7).
Figure 7 Trends in number of days per year with at least 20 mm precipitation, measured at European weather stations between 1946 and 2004. Source:
ECA&D.
Observed in the Netherlands
In the Netherlands, the annual precipitation amount increased by 18% from 1906 on (Figure 8). This is especially caused by an increase in winter (+26%), spring (+21%) and autumn (+26%), while in the summer the precipitation amount has hardly changed (+3%). In winter, also the extreme multi-day precipitation amounts increased. The highest 10-day total precipitation per winter increased with 29% since 1906. In summer no clear trend in extreme precipitation has been found.
Figure 8 Total annual precipitation in the Netherlands (average of 13 stations) between 1906 and 2005. The thick black line represents the 30-year moving average.
