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

Hallam, Samantha; Guishard, Mark; Josey, Simon A. ORCID: https://orcid.org/0000-0002-1683-8831; Hyder, Pat; Hirschi, Joel J.-M.. 2021 Increasing tropical cyclone intensity and potential intensity in the subtropical Atlantic around Bermuda from an ocean heat content perspective 1955- 2019. Environmental Research Letters, 16 (3), 034052. https://doi.org/10.1088/1748-9326/abe493

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Official URL: http://dx.doi.org/10.1088/1748-9326/abe493

Abstract/Summary

We investigate tropical cyclone (TC) activity and intensity within a 100km radius of Bermuda between 1955 and 2019. The 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 (r=0.94, p=0.02), together with significant increasing August, September, October (ASO) sea surface temperature (SST) of 1.1°C (0.17°C per decade) r= 0.4 (p<0.01) and increasing average ocean temperature between 0.5–0.7°C (0.08-0.1°C per decade) r=0.3(p<0.01) 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 as 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 (r=0.74, p<0.01) 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.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1088/1748-9326/abe493
ISSN:	1748-9326
Date made live:	01 Mar 2021 14:04 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/529771

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1088/1748-9326/abe493

ISSN:

1748-9326

Date made live:

01 Mar 2021 14:04 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/529771