A pioneering study by the University of Sheffield has revealed the meteorological impact of the 2015 UK solar eclipse across three countries.
The analysis of high-frequency surface air temperature, mean sea-level pressure, wind speed and direction and cloud-cover data from the solar eclipse of 20 March 2015 from the UK, Faroe Islands and Iceland, published today (Monday 22 August 2016), sheds new light on the phenomenon.
The research, led by Professor Edward Hanna, of the University of Sheffield’s Department of Geography, used data from 76 UK Met Ofﬁce weather stations, 30 weather stations in the Faroe Islands and 148 stations in Iceland.
- There was a statistically signiﬁcant mean UK temperature drop of 0.83±0.63 degrees Celsius, which occurred over 39 minutes on average, and the minimum temperature lagged the peak of the eclipse by about ten minutes.
- For a subset of 14 relatively clear (cloudy) stations, the mean temperature drop was 0.91± 0.78 (0.31±0.40)degC, but the mean temperature drops for relatively calm and windy stations were almost identical, indicating that cloud cover has a much greater effect than wind on the air temperature’s response to an eclipse.
- The average wind speed dropped signiﬁcantly by 9 per cent on average during the ﬁrst half of the eclipse, in line with previous studies.
- There was no detectable effect of the eclipse on the wind-direction or barometric pressure time series, and therefore we can discount any localised change in air circulation over Britain (for example, the much-fabled ‘eclipse cyclone’) during this event.
- Similar changes in air temperature and wind speed were observed for Iceland, where conditions were generally clearer, but there is no evidence of the eclipse cyclone.
- In the Faroes, there was a much more muted meteorological signature.
The study represents a successful co-operation between the University of Sheffield, the UK Met Office, the Icelandic Met Office, the Danish Meteorological Institute and the Faroe Islands Met Service.