The characteristics and temporal variability of föhn winds at King Edward Point, South Georgia

Bannister, Daniel ORCID: https://orcid.org/0000-0002-2982-3751; King, John C. ORCID: https://orcid.org/0000-0003-3315-7568. 2020 The characteristics and temporal variability of föhn winds at King Edward Point, South Georgia. International Journal of Climatology, 40 (5). 2778-2794. https://doi.org/10.1002/joc.6366

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Text This is the peer reviewed version of the following article: Bannister, D. and King, J. C. (2019), The Characteristics and Temporal Variability of Föhn Winds at King Edward Point, South Georgia. Int J Climatol, which has been published in final form at doi:10.1002/joc.6366. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. JOC-18-0901.R1_revised.docx - Accepted Version Download (75kB)

Abstract/Summary

The mountainous subantarctic island of South Georgia lies within the belt of strong westerly winds that blow around the Southern Ocean. Interaction of the prevailing circumpolar westerly winds with the island’s central mountain chain, which rises to nearly 3000 m, generates warm, dry föhn winds on the downwind side of the island, which are a significant feature of the local climate. We make use of ten years of automatic weather station observations from King Edward Point (KEP), on the northeastern (climatologically downwind) coast of South Georgia, to develop a climatology of the occurrence and properties of föhn winds in this region. Using objective criteria to identify the onset and cessation of föhn, we find that KEP experiences föhn conditions for around 30% of the time. Föhn events last for about 30 hours on average and are associated with significant increases in temperature and wind speed, and decreases in relative humidity. On average, a föhn event is observed every four days, with little seasonal variation seen in the frequency of occurrence. However, föhn events observed during the austral summer season are, on average, both longer and more intense (as measured by changes in temperature, relative humidity and wind speed) than those occurring in other seasons. The fraction of the time for which föhn conditions are observed at KEP increases (decreases) during months when the prevailing westerlies are strengthened (weakened). Monthly mean temperatures at KEP are positively correlated with the föhn fraction but variations in the latter only explain 16% of the variance of monthly mean temperature. We conclude that, while föhn plays an important role in shaping the local climate of South Georgia, other processes may be of greater importance in controlling regional climate variability and change.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1002/joc.6366
ISSN:	0899-8418
Additional Keywords:	Föhn, South Georgia, Subantarctic, Southern Ocean, orography, climate change
Date made live:	25 Oct 2019 09:16 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/525554

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