Precipitation variability in the Meuse basin in relation to atmospheric circulation.

The distribution of precipitation events in the Meuse basin during the past century has been found to reflect the large-scale atmospheric circulation, as characterised by the Grosswetterlagen system. Statistical analysis of the long observation records (1911–2002) for the basin showed that although the annual (November to October) and winter half-year (November to April) frequencies of wet days (≥1 mm/day) were nearly stable, the associated precipitation amounts have significantly increased since 1980. From 1980 onwards, the very wet days (≥10 mm/day) in the winter half-year have become more frequent. No obvious change was identified for the summer half-year (May to October) very wet days. Both the precipitation amounts of wet and very wet days in the winter half-year and the occurrence of associated atmospheric circulation of the types/sub-types west cyclone, southwest cyclone and northwest cyclone showed a significant increase around 1980.