On the links between sub-seasonal clustering of extreme precipitation and high discharge in Switzerland and Europe

Abstract

Abstract. River discharge is impacted by the sub-seasonal (weekly to monthly) temporal structure of precipitation. One example is the successive occurrence of extreme precipitation events over sub-seasonal timescales, referred to as temporal clustering. Its potential effects on discharge have received little attention. Here, we address this question by analysing discharge observations following extreme precipitation events either clustered in time or occurring in isolation. We rely on two sets of precipitation and discharge data, one centered on Switzerland and the other over Europe. We identify "clustered" extreme precipitation events based on the previous occurrence of another extreme precipitation within a given time window. We find that clustered events are generally followed by a more prolonged discharge response with a larger amplitude. The probability of exceeding the 95th discharge percentile in the five days following an extreme precipitation event is in particular up to twice as high for situations where another extreme precipitation event occurred in the preceding week compared to isolated extreme precipitation events. The influence of temporal clustering decreases as the clustering window increases; beyond 6–8 weeks the difference with non-clustered events is negligible. Catchment area, streamflow regime and precipitation magnitude also modulate the response. The impact of clustering is generally smaller in snow-dominated and large catchments. Additionally, particularly persistent periods of high discharge tend to occur in conjunction with temporal clusters of precipitation extremes.

Budyko framework based analysis of the effect of climate change on watershed characteristics and their impact on discharge over Europe

“…Milly et al (2005) showed that streamflow trends world wide are and will continue to be significantly impacted by changes in climatic factors. Studies show the impact of distribution and concentration of rainfall events on peaks of discharge Q (Tuel et al, 2022). However rivers are also highly managed and human activities are a main driver of change in the functioning of watersheds.…”

Assessment of S2S ensemble extreme precipitation forecasts over Europe

“…the impact of storms and flood quantified in WMO, 2021). Additionally, if several extreme precipitation events occur in close succession (temporal clustering), flooding becomes more likely Tuel et al (2022). The successful mitigation of weather-related hazards depends on our ability to forecast them reliably.…”