Representation of mid-latitude North American coastal storm activity by six global reanalyses

Extratropical cyclones often produce extreme and hazardous weather conditions, such as high winds, heavy precipitation, blizzard conditions, and flooding, all of which have detrimental environmental/physical and socio-economic impacts. Furthermore, storm interaction with the ocean produces additional hazards, with major local impacts, including inundation and coastal erosion. The North American west coast is influenced by the North Pacific storm track and by atmospheric river' events while the east coast is particularly influenced by winter storms that track along two favoured routes: the St. Lawrence Valley and the Eastern Seaboard. Reanalysis provides an invaluable tool for studying the characteristics of storm events that are identified as causing the most severe impacts. However, reanalysis products differ substantially in spatial resolution, model physics, assimilation approach, and the data that are assimilated. This study evaluates the representation of storm activity along the mid-latitude North American coastlines by six global reanalyses: NCEP-1, NCEP-2, ERA-Interim, Modern-Era Retrospective analysis for Research and Applications (MERRA), Climate Forecast System Reanalysis (CFSR), and Twentieth Century Reanalysis Version 2 (20CR). Storm activity representation is evaluated at annual and seasonal timescales (JFM, AMJ, JAS, OND, and extended winter' ONDFM) during the 1979-2010 time period through comparison with selected meteorological stations using single-point surface pressure-based proxies of extratropical storm activity. Stations are selected on the basis of record length, reporting frequency, coastal proximity, and relatively uniform spatial distribution. Comparisons are made using data extracted from the reanalysis grid box centre that is closest to each selected station. All reanalyses are found to successfully represent most aspects of mid-latitude North American coastal strong storm activity, annually and seasonally, along both coasts. Nevertheless, ERA-Interim, MERRA, and CFSR provide the better representations of mid-latitude North American coastal strong storm activity, with ERA-Interim performing best overall.