National Eclipse Weather Experiment – Frequently Asked Questions
WARNING – NEVER LOOK DIRECTLY AT THE SUN. Information on safe viewing of the eclipse can be
found at https://www.ras.org.uk/images/solar_eclipse_leaflet.pdf
The Eclipse
1. When is the solar eclipse and where does it cover?
It will occur on Friday 20th March 2015, and affect the UK, with the maximum eclipse at about
0930UT. The eclipse will be greater in the north of the UK than in the south, and will be total at the
Faroes. For details see http://eclipse.gsfc.nasa.gov/SEplot/SEplot2001/SE2015Mar20T.GIF
The Science
2. Why study the eclipse weather?
A solar eclipse is a natural experiment with the atmosphere, which is known about in advance
because the positions of the Sun and the Moon can be calculated very precisely. By studying the
responses in the atmosphere, theories about the way weather is generated can be investigated as
well as the representation of the atmosphere in weather models. A comparison between predicted
and observed effects can also be made, which is a major way in which science progresses.
3. What weather effects of the eclipse you are attempting to measure?
During the reduction in solar radiation, the energy entering the weather generating regions of the
atmosphere will lessen. In the lower atmosphere, this may lead to temperature, pressure and wind
changes. There is a discussion of these here:
http://www.met.reading.ac.uk/Data/CurrentWeather/wcd/blog/the-eclipse-wind-real-or-imagined/
4. What is the eclipse wind?
Cooling of the air can lead to changes in wind flow, as sometimes happen around the coast at
sunrise and sunset. There have been suggestions that something similar occurs during an eclipse,
see, for example http://news.bbc.co.uk/2/hi/science/nature/2515045.stm. This also discussed at
http://planetearth.nerc.ac.uk/news/story.aspx?id=1190&cookieConsent=A
The Method
5. Why are new observations needed?
The last major solar eclipse in the UK was in 1999, and, although there were some good
measurements, they were widely spaced across the UK and they weren’t obtained very frequently.
There is now the opportunity to obtain a very large number of measurements, with rapid sampling.
This gives the potential for the most extensively sampled eclipse weather data ever.
6. Why are you asking for people to make measurements rather than using automatic systems?
Cloud is one of the quantities we would like information about, and this is not well observed by
automatic systems, or indeed at all. Human observations therefore have a lot to offer. Some
information can also be provided by automatic systems, but because there are so many and they are
very different in how they operate, the information still needs to come via the webform. (See also 11
below.)
The Experiment
7. What instruments are needed to participate in the experiment?
You can start with just your (protected) eyes, as one thing which we would like to detect is any
change in cloud. Temperatures and wind speeds will also be highly useful. If you have an automatic
weather station, uploading some of its measurements before, during and after the eclipse will be
excellent. If you have a hand-held thermometer or anemometer (to measure wind speed), please
make sure the thermometer is kept in the shade throughout, and that you include measurements
made before and after the maximum eclipse, ideally and hour before and an hour after.
Remember that your eyes must be protected if you are looking at or near the sun. Look away from
the sun to observe cloud.
8. Why do you need my postcode?
The postcode is being used to locate where the observations were made, so that we can see
determine patterns in the weather changes across the eclipse zone. It is not being used to identify
you.
9. How do I upload the measurements I have?
Go to the webform at http://goo.gl/forms/FUfrfp3UBK , where there are more instructions.
10. The webform seems not to be available?
Samples of the webform will be available on the NEWex website from 48 hours beforehand, so that
you can plan what data to collect on the day and practice data entry. The data on the webform will
be collected from 0800UT on 20th March 2015, and entries can be made until the end of Stargazing
live that day (2100UT).
11. I have some automatic system data. Would you like it?
We would be pleased to include the data in the analysis if you can enter it via the webform at
http://goo.gl/forms/FUfrfp3UBK.
Alternatively, if you have a large data file not easily entered, Professor Edward Hanna at the
University of Sheffield made an appeal for data in the December 2014 edition of Weather, which is
partially reproduced below:
Weather readers are invited to contribute observations of surface-air temperature, relative
humidity, wind speed and direction, as well as (if available) any cloud-cover and cloud-type
observations for the whole of the relevant day. Ideally, observations of these data for 3 days
before and after the event should also be supplied, if available, to provide several ‘control’
days.
Any observations will be gratefully received and acknowledged, especially automaticweather-station data of the requested parameters, recording in UTC, at a time interval of no
greater than 10 min (1–5 min frequency would be ideal).
Please email observations, which should be in .dat, .csv or Excel file format, as soon as
possible after the event(ideally by 3 April) to [email protected] with ‘Eclipse met
obs: [STATION NAME]’ in the email subject header.