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The Role of Atmospheric Rivers in compound events consisting of
heavy precipitation and high storm surges along the Dutch coast

Abstract. Atmospheric river (AR) systems play a significant role in the simultaneous occurrence of high coastal water levels and heavy precipitation in the Netherlands. Based on observed precipitation values (E-OBS) and the output of a numerical storm surge model (WAQUA/DSCMv5) forced with ERA-Interim sea level pressure and wind fields, we find that the majority of compound events between 1979–2015 has been accompanied by the presence of an AR over the Netherlands. By isolating and assessing the prevailing sea level pressure (SLP) and sea surface temperature (SST) conditions up to seven days before the events with and without AR involvement, we show that the presence of ARs constitutes a specific type of forcing conditions that (i) resemble the SLP anomaly patterns during the positive phase of the North Atlantic Oscillation (NAO+) with a North-South pressure dipole over the North Atlantic and (ii) cause a warming of the western boundary of the North Atlantic. These conditions are clearly distinguishable from those conditions during compound events without the influence of local ARs which occur under SLP conditions resembling the East Atlantic (EA) pattern with a West-East pressure dipole over Northern Europe and are accompanied by a cooling of the West Atlantic. Thus, this study provides a useful tool for the early identification of possible harmful meteorological conditions over the Netherlands and supports effort for the establishment of an early warning system.
