Spatial variability of trends in hydrological extremes induced by orographically enhanced rainfall events due to westerly atmospheric circulations.
Since the mid 1970s, the number of days with westerly atmospheric circulations has strongly increased during winter months. As a consequence, rainfall totals, rainfall event duration and intensity have been subject to significant positive trends throughout the Mosel river basin. However, the trends identified through the non-parametrical test named Kendall's tau have shown to be spatially varying. The intensity of the trends appears to be directly linked to orographic obstacles that are well known to have a strong influence on average rainfall totals. A direct consequence of the changes having affected winter rainfall under westerly atmospheric circulations on the one hand and the spatial variability of these changes on the other hand, is a spatially varying positive trend in maximum winter streamflow. Thus, even though a clear large-scale change has affected winter rainfall over the past decades, its intensity is either strongly moderated or enhanced by orographic obstacles. The related changes in streamflow are directly dependent on the spatial variability of the changed rainfall characteristics.
Pfister
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Public Research Center - Gabriel Lippmann, 162a avenue de la Faïencerie, L-1511 Luxembourg, Grand-Duchy of Luxembourg. pfister@crpgl.lu
Drogue
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Poirier
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Hoffmann
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D000392:Air Movements; D001272:Atmosphere; D002980:Climate; D004784:Environmental Monitoring; D005060:Europe; D011891:Rain; D045483:Rivers; D012621:Seasons; D014872:Water Movements