A new climate index controlling winter wave activity along the Atlantic coast of Europe: The West Europe Pressure Anomaly. Issue 3 (2nd February 2017) - Castelle, Bruno
Abstract: A pioneering and replicable method based on a 66‐year numerical weather and wave hindcast is developed to optimize a climate index based on the sea level pressure (SLP) that best explains winter wave height variability along the coast of western Europe, from Portugal to UK (36–52°N). The resulting so‐called Western Europe Pressure Anomaly (WEPA) is based on the sea level pressure gradient between the stations Valentia (Ireland) and Santa Cruz de Tenerife (Canary Islands). The WEPA positive phase reflects an intensified and southward shifted SLP difference between the Icelandic low and the Azores high, driving severe storms that funnel high‐energy waves toward western Europe southward of 52°N. WEPA outscores by 25–150% the other leading atmospheric modes in explaining winter‐averaged significant wave height, and even by a largest amount the winter‐averaged extreme wave heights. WEPA is also the only index capturing the 2013/2014 extreme winter that caused widespread coastal erosion and flooding in western Europe. Key Points: A method is developed to objectively define an optimal climate index explaining winter wave activity variability along the west coast of Europe WEPA index is computed as the normalized difference in sea level pressure measured between Ireland and Canary Islands WEPA significantly outscores other leading atmospheric modes in explaining the winter wave variability along most of the west coast of Europe