EGU21-7803, updated on 21 Apr 2021
https://doi.org/10.5194/egusphere-egu21-7803
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Increasing tropical cyclone intensity and potential intensity in the subtropical Atlantic around Bermuda from an ocean heat content perspective 1955- 2019

Samantha Hallam1,2,3, Mark Guishard4,5, Simon Josey3, Pat Hyder6, and Joel Hirschi3
Samantha Hallam et al.
  • 1University of Southampton, National Oceanography Centre, Southampton, United Kingdom of Great Britain – England, Scotland, Wales (s.hallam@noc.soton.ac.uk)
  • 2Irish Climate Analysis and Research Units, Maynooth University, County Kildare, Ireland
  • 3National Oceanography Centre, European Way, Southampton, SO14 3ZH
  • 4Bermuda Institute of Ocean Sciences, 17 Biological Station, St. George’s GE 01, Bermuda
  • 5Bermuda Weather Service, Bermuda Airport Authority, St. George’s DD03, Bermuda
  • 6Met Office, Fitzroy Road, Exeter, EX1 3PB

Here we investigate tropical cyclone (TC) activity and intensity within a 100km radius of Bermuda between 1955 and 2019. Our results show a more easterly genesis over time and significant increasing trends in tropical cyclone intensity (maximum wind speed (Vmax)) with a decadal Vmax median value increase of 30kts from 33 to 63kts, together with significant increasing August, September, October (ASO) sea surface temperature (SST) of 1.1°C (0.17 °C per decade)  and ocean temperature between 0.5–0.7°C (0.08-0.1°C per decade)  in the depth range 0-300m. The strongest correlation is found between TC intensity and ocean temperature averaged through the top 50m ocean layer (T50m) r=0.37 (p<0.01). 

We show how tropical cyclone potential intensity estimates are closer to actual intensity by using T50m opposed to SST using the Bermuda Atlantic Timeseries Hydrostation S dataset. We modify the widely used sea surface temperature potential intensity index by using T50m to provide a closer estimate of the observed minimum sea level pressure (MSLP), and associated Vmax than by using SST, creating a T50m potential intensity (T50m_PI) index. The average MSLP difference is reduced by 12mb and proportional to the SST/ T50m temperature difference. We also suggest the index could be used over a wider area of the subtropical/tropical Atlantic where there is a shallow mixed layer depth. Finally, we outline the TC wind-pressure relationship observed for the subtropical Atlantic around Bermuda, explaining 77% of the variance, which may prove useful for future prediction.

(Environmental Research Letters, 2020, in revision)

 

 

How to cite: Hallam, S., Guishard, M., Josey, S., Hyder, P., and Hirschi, J.: Increasing tropical cyclone intensity and potential intensity in the subtropical Atlantic around Bermuda from an ocean heat content perspective 1955- 2019, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7803, https://doi.org/10.5194/egusphere-egu21-7803, 2021.

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