Sunny skies are certainly a favourite type of weather for many but how exactly is the amount of sunshine recorded?
These days sunshine duration is recorded using modern electronic sensors however until the instruments were recently digitalised, sunshine was recorded using something called a Campbell- Stokes recorder.
The Campbell-Stokes recorder was invented in 1853, and consists of a glass sphere mounted onto a frame, this originally was wood but adapted to metal in 1879.
The glass sphere concentrates the sun’s rays onto a card attached to the back of the instrument, creating a scorch mark on the card to mark a period of sunshine; the length of the burn mark reveals the duration of sunshine.
It is a self-recording traditional instrument that is still in use at many non-automatic weather stations today – nearly 170 years after it was first invented!
Not only is the Campbell-Stokes recorder used to measure sunshine duration but the width of the burn can estimate sky conditions also. Comparing data between a Campbell-Stokes recorder and an automatic device, a wide burn on the card corresponds to full sunshine and clear skies, and thinner burn lines equate to increasing amounts of cloud.
Unfortunately, this piece of instrumentation is known to overestimate sunshine duration but given the good spatial and temporal data spread over the years, these sunshine records can help with climate science research.
Over the coming days and through the weekend the Vale will see more glorious sunshine with the first few days of July currently looking warm, although with a chance of a few showers in between too.