Atmospheric Rivers over Europe: Hydrological Impacts and Predictability

Damage from flooding in the winter and fall seasons has been widespread in the United Kingdom (UK) and Western Europe over the last two decades. In recent years the role of atmospheric rivers (ARs), narrow regions of intense water vapor transport in the lower troposphere, in mid-latitude flooding has been highlighted. The aim of this study is to (1) show the connection between ARs and extreme European precipitation and floods, and (2) discuss future changes to ARs under projected climate change.

The research presented uses satellite and atmospheric reanalysis data, daily observed precipitation and river flows, and climate change projections from five models in the Coupled Model Intercomparison Project Phase 5 (CMIP5) archive. The results presented will show the strong link between ARs and heavy precipitation and floods in Europe, and will highlight how ARs are projected to change in the future. In particular the five CMIP5 models assessed show an approximate doubling of winter ARs affecting the UK in the period 2073-2099 compared to 1979-2005; this is likely to result in an increased risk of flooding in the future. Finally, an assessment of the predictability of an AR-type diagnostic using output from the European Centre for Medium-Range Weather Forecasts ensemble prediction system will be covered.