ERL." href="http://images.iop.org/objects/erw/news/11/12/20/pic1.jpg">Cyclone tracks
"Our motivation for the study was to better understand coastal high-water events and their relationship to the storms that cause these hazards," James Booth of the City University of New York, US, told environmentalresearchweb.
As the team – which also includes researchers from Columbia University and the University of Graz – considered the data (provided by NOAA) it became clear that there were many interesting similarities between surges associated with hurricanes and those associated with extratropical cyclones.
"After superstorm Sandy, there has been a lot of focus on storm surge related to hurricanes," said Booth. "This attention is warranted because these storms can be very dangerous, but extratropical cyclones can also cause surge, and – from the perspective of the sea level along the coast – the storm type does not create a significant difference."
If the strongest events in terms of surge amplitude and spatial extent are singled out, then hurricanes are most likely to create the hazards, the team’s results show. However, this situation shifts when slightly weaker events are added to the picture. For these cases, which still impact multiple areas during the storm life cycle, the relative importance of hurricanes shrinks as that of extratropical cyclones grows. In addition, the researchers found distinct paths for extratropical cyclones causing multi-site surge at individual segments of the US east coast.
"If you live near the coast and are wondering if hurricanes pose a particularly different threat than extratropical cyclones – the answer is no," said Booth. "We need to be prepared for surge associated with either storm type."
As well as providing food for thought for coastal areas, the researchers believe that their work will have a useful impact in the scientific community.
Booth points out that hurricanes and extratropical cyclones differ in their primary source of energy. Surface winds in hurricanes are driven by condensational heating within the storm, whereas surface winds in extratropical cyclones are linked with sharp temperature gradients and the synoptic-scale flow that’s associated with the atmosphere working to move energy poleward.
"These differences in energy sources for the storm winds also motivated our comparison of the surge associated with these two types of storms," Booth added. "We wanted to know if a clear demarcation in surge physics could be identified."
The group found that a separation in surge physics based on storm type is only evident when the very strongest events – typically, the top one or two storms per sea-level station – are considered, with these almost always being hurricanes.
Full details, including the method used by the team to rank the surge events, can be found in Environmental Research Letters (ERL).
Related links
- James Booth
- Comparing hurricane and extratropical storm surge for the Mid-Atlantic and Northeast Coast of the United States for 1979–2013 J F Booth et al 2016 Environ. Res. Lett. 11 094004
- ERL