The role of atmospheric rivers in compound events consisting of heavy precipitation and high storm surges along the Dutch coast

Abstract

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 (CEs) between 1979 and 2015 have been accompanied by the presence of an AR over the Netherlands. In detail, we show that CEs have a 3 to 4 times higher chance of occurrence on days with an AR over the Netherlands compared to any random day (i.e. days without knowledge on presence of an AR). In contrast, the occurrence of a CE on a day without AR is 3 times less likely than on any random day. Additionally, by isolating and assessing the prevailing sea level pressure (SLP) and sea surface temperature (SST) conditions with and without AR involvement up to 7 days before the events, 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 cooling of the North Atlantic subpolar gyre and eastern boundary upwelling zone while warming the western boundary of the North Atlantic. These conditions are clearly distinguishable from those during compound events without the influence of an AR 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 shows that ARs are a useful tool for the early identification of possible harmful meteorological conditions over the Netherlands and supports an effort for the establishment of an early warning system.

Measuring compound flood potential from river discharge and storm surge extremes at the global scale

“…Atmospheric rivers landing on the West Coast of the US have caused recurrent major flood events (Gimeno et al, 2014). Composite analyses of these systems show that they can be accompanied by extreme skew surge (Ridder et al, 2018;Ward et al, 2018). The Iberian Peninsula and the Atlas Mountains contain major orographic features that can block prevailing wind flows and trigger orographic rainfall during low pressure systems, thereby causing high river discharge.…”

“…A consistent mathematical definition of compound flood events does not exist and multiple statistical methods have been suggested to study this phenomenon (Hao et al, 2018;Tilloy et al, 2019). These methods usually examine the number of joint extremes or the statistical dependence between proxy variables of different flood hazard types such as rainfall and storm surge, river flow and storm surge, and river flow and sea level (Bevacqua et al, 2019;Hendry et al, 2019;Kew et al, 2013;Paprotny et al, 2018a;Sadegh et al, 2018;Jones, 2002, 2004;Wahl et al, 2015;Wu et al, 2018;Zheng et al, 2013). Recent compound flooding studies carried out at the regional to global scale used copula theory to characterise the bivariate joint distribution and assess complex dependence structures, e.g.…”

The Impact of Meteorological and Hydrological Memory on Compound Peak Flows in the Rhine River Basin

“…This study primarily focuses on compound hydrometeorological events and their intensification by the memory of hydrological processes. For Dutch coastal areas, several studies describe CEs for storm surges in combination with wind [34], precipitation [33,34,38,40,41] and discharge [35,42]. These studies confirm a clear correlation structure among the compound occurrence of storm surges and discharge (precipitation).…”

“…These studies confirm a clear correlation structure among the compound occurrence of storm surges and discharge (precipitation). Further, they share some shortcomings emanating from using limited observation records, reanalysis products or model simulations, and/or focusing on a limited dynamic range of the lagged signals contributing to the CEs [33][34][35]40,41]. Moreover, these studies focused on a predefined timescale without explicitly exploring the role of process memory in the governing hydrometeorological systems.…”

Storm Surge and Extreme River Discharge: A Compound Event Analysis Using Ensemble Impact Modeling

“…Further, the slow melt from snow and glaciers would require an additional day or two to reach Basel. The storm surges along the Dutch coasts are driven by meteorological conditions (Ridder et al, 2018a). In general, the most extreme storm surges are associated with low pressure systems in the North Eastern Atlantic area, depression trajectories with a south-east direction, along the jet stream over the North Sea results in the development of persistent strong north-westerly winds and related surge conditions at the Dutch coast (van den Hurk et al, 2015).…”