Effect of large-scale atmospheric circulation and wind on storm surge occurrence

Large scale atmospheric circulation is an important component of wind forcing which in turn control strom surge generation. The study aim is to evaluate the impact of large-scale atmospheric flow and wind on the occurrence of storm surges causing significant morphological impacts along the Belgian coast. An objective classification scheme of the atmospheric circulation affecting the North Sea basin is used for almost 150-years (1871-2014). The observed storm surge events associated with erosion are examined with respect to the circulation weather types (CWTs) and the winter North Atlantic Oscillation (NAO) phases under which they occur. It is shown that although the Anticyclonic (A) type being the most frequent in winter (27%) and also over the entire year (28%) gives less than 1- 10% of contribution to the occurrence of observed storm surges. However, the Cyclonic (C), Northerly (N), Northwesterly (NW), Westerly (W) and Southwesterly (SW) types happen less often, they account together for more than 82% of the observed storm surges. Also, the observed storm surges primarily occurred during a moderately positive winter NAO index while strong winter NAO index rarely accounted for the storm surge events. Results highlight the inter-connections between the occurrence of observed storm surges, interannual variability of CWTs and winter NAO index. These data are also investigated to examine their evolutionary trends in order to detect any ongoing trends of climate change. Identify any link and trend between storminess and atmospheric circulation pattern could help to better prepare coastal communities and coastal managers for future storm surges.