Northeast Atlantic Storm Activity and Its Uncertainty from the Late Nineteenth to the Twenty-First Century

Abstract

Geostrophic wind speeds calculated from mean sea level pressure readings are used to derive time series of northeast Atlantic storminess. The technique of geostrophic wind speed triangles provides relatively homogeneous long-term storm activity data and is thus suited for statistical analyses. This study makes use of historical air pressure data available from the International Surface Pressure Databank (ISPD) complemented with data from the Danish and Norwegian Meteorological Institutes. For the first time the time series of northeast Atlantic storminess is extended until the most recent year available, i. e. 2016. A multi-decadal increasing trend in storm activity starting in the mid-1960s until the 1990s, whose high storminess levels are comparable to those found in the late 19th century, initiated debate whether this would already be a sign of climate change. This study confirms that long-term storminess levels have returned to average values in recent years and that the multidecadal increase is part of an extended interdecadal oscillation. In addition, new storm activity uncertainty estimates were developed and novel insights into the connection with the North Atlantic Oscillation (NAO) are provided.