The hourly gale record from Valentia Observatory, SW Ireland 1874–2008 and some observations on extreme wave heights in the NE Atlantic

摘要

The sustained hourly gale record from Valentia Observatory, SW Ireland over the time period from 1874–2006 shows very significant variations including high values in the 1920s, 1940s, 1960s and 1980s but a decline since then down to the lowest recorded levels at present. Most gales occur in winter and in particular in December and January. An analysis of the wind duration and speed data shows that there has been increased variability in the duration of gales over the last 20 years and despite an overall decline in mean wind speed there is no indication that gale strengths have changed in any systematic way. This gale data is strongly in contrast to the outputs and predictions from the various scenarios in the ECHAM4 models which predict at worst no changes in cyclonicity of depressions below 1,000 hPa but significant increases in cyclonicity of severe depressions below 940 hPa. At present the actual data is running contrary to the model outcomes at Valentia and elsewhere in Ireland. The sustained gales have given rise to wave heights in excess of 30 m and this documentary evidence is verified by more recent satellite and marine buoy data.