Impacts of Friday’s partial eclipse

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  • The path of the eclipse over Europe, with the percentage of totality and the time it will be seen.

    The forecast solar output for Germany, showing the dip in output expected at the time of the eclipse.

  • Impacts of Friday’s partial eclipse
    19.03.2015 17:25

    During the morning of Friday 20th March 2015, a total solar eclipse will occur between Scotland and Iceland and across the Norwegian Sea. The Faroe Islands and Norway’s Svalbard archipelago north of the mainland are the only land areas that will experience totality (100% of the sun's disc covered). However, portions of northern and western Scotland and western Norway will see approximately 95% covered for a few minutes. Only a partial solar eclipse will occur across the rest of mainland Europe, with less of the sun being obscured as you head south-east. Even so, observers in southeast England will still see 85% of the sun obscured.

     

    The longest duration of totality for this eclipse will be 2 minutes and 46 seconds as viewed off the coast of the Faroe Islands. This will mark the last total solar eclipse in Europe for over a decade, with the next not being until August 12, 2026.

     

    In regions of totality, previous studies have observed some quite strong effects on temperature and radiation, especially if there are clear skies prior to and during the eclipse. Much of Europe will lie away from this zone but there are still likely to be changes in temperature.

     

    During the eclipse of 11th August 1999, the area of totality in SW England had quite thick cloud and a few showers, so the temperature effect seems to have been quite small, although noticeable a drop of about 1 deg C.

     

    Farther north-east where it was brighter, the temperature drop was larger. For example, in Berkshire the temperature fell by up to 3.5 deg C at Reading, Bracknell and Farnham. The average drop for the UK was around 1.5 to 2 deg C.  The temperature drop would have been larger had it not occurred at a time when the diurnal trend was upwards – as it will also be on Friday 20th.

     

    Wind speeds decreased quite widely, although they were very light in general at other times so this was difficult to detect without quite sensitive anemometers.

     

    The revered amateur meteorologist Luke Howard – “the man who named the clouds” – also measured changes in temperature during the partial eclipse of 7th September 1820. He noted that the temperature fell from 68.5 deg F (about 20 deg C) to 62.5 deg F (17 deg C), and that the lowest temperature was about seven minutes after the maximum obscuration.

     

    Cloud cover is of course crucial to chances of viewing the eclipse, and MeteoGroup’s models show that much of Scotland could be unlucky, with the best cloud breaks probably in the east, most likely eastern Aberdeenshire. For Wales the best chances are away from the north, while in England the north, East Anglia and parts of the extreme southeast could have rather obscured skies. Elsewhere cloud should break at least partially and viewing possibilities are better. Probabilities lean towards South Wales and Southwest England as the most likely areas to have largely clear skies; but if we are lucky those conditions could spread farther east and north as the morning progresses.

    Details of the partial eclipse per country:

    Country

    Fraction of the sun covered

    Time of max solar eclipse (GMT) across each country

    Spain

    65-80%

    09:00-09:15

    France

    70-85%

    09:20-09:35

    UK

    85-95%

    09:25-09:40

    Italy

    55-70%

    09:30-09:40

    Belgium
     

    80-85%

    09:35-09:40

    Netherlands
     

    80-85%

    09:40 09:45

    Germany

    70-85%

    09:35-09:50

    Scandinavia

    80-100%

    09:35-10:15

     

    Energy companies have a lot of interest in this eclipse, especially in Germany where solar power provides a relatively large proportion of electricity to the grid. There will be a sharp drop in power during the event of about 12 GW, followed by a rapid surge as full sunshine reappears, which will need careful management. 

     

    In the UK, given less solar power the effects will be felt less. It could be that there will be a larger variation in demand than supply if the 1999 eclipse is any guide. So many people wandered outside for a look that demand plummeted by about 2GW over 30 minutes; then a huge surge in demand of 3 GW followed as they returned to their televisions and computers, and no doubt as millions of kettles were switched on for a post-eclipse cuppa. This was one of the largest shifts ever for the national grid.  

    By: Stephen Davenport