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4 Mar 2021

Come rain or shine – Inverewe’s weather station

Written by Cassie Cowie, Walled Gardener, Inverewe Garden
A close-up view of a sunlight recorder, which consists of a glass ball (rather like a crystal ball) mounted on a sundial-type frame. A metal structure half encircles it, with markings on it to chart the sun's progress.
A component of the weather station at Inverewe
Weather readings from Inverewe have been taken on a daily basis since 1965, with the data being used to improve the Met Office’s forecasting accuracy and climate modelling.

For most of these 50 years, the weather station has been sited to the south end of Inverewe Garden, away from public areas. However, there are now plans to move it to the foreshore in front of the walled garden, as the current location is considered too overgrown to give accurate readings.

The weather station itself consists of three parts – the white Stevenson box, which stands 1.25 metres off the ground; a small square of grass holding two alcohol thermometers and a rain gauge; and a sunlight recorder, sitting on top of a post. The Stevenson box is named after its inventor Thomas Stevenson, father of famous author Robert Louis. Another relative was David Allan Stevenson, an engineer for the Northern Lighthouse Board, who built the local lighthouse Rua Reidh in 1910.

Responsibility for the weather reading has traditionally sat with the propagator role at Inverewe Garden, but it now lies with the walled gardener simply because that is the closest work area to the weather station. Weekend readings were normally taken by the weekend duty gardeners on a rota system, but are now mainly taken by the two regular weekend duty gardeners: Maddie and Jim. Most members of staff, work experience students and apprentices are also trained to take readings if the main recorders are absent.

Every day the weather must be taken at a specific time (09:00 during British winter time and 09:45 during British summer time). This is done by opening up the weather station to take the average maximum and minimum air temperatures from the previous 24 hours, and the current air and water temperatures from a combination of electronic and alcohol thermometers.

Next, the person recording the weather moves on to the small patch of grass next to the station, where the grass and 30cm-depth temperatures are read from two alcohol thermometers. The grass one lies on the grass surface, and the 30cm-depth one is contained in a plastic tube buried vertically in the ground. Next to them is the rain gauge, which is a funnel of a prescribed circumference that catches the rain and empties it into a plastic bottle. The volume of water is taken from here, using a measuring cylinder.

The sunlight hours are burned into a sun card using a large glass ball that concentrates the sunlight onto the sun card, allowing the reader to calculate how much direct sunlight there has been in the last 24 hours. Further observations include cloud cover, wind speed and direction, visibility and current weather conditions – these are all logged using set codes provided by the Met Office.

Once all the data has been collected, it is recorded in the ‘register for climatological observations’, a booklet provided by the Met Office with the correct coding for the appropriate observations, before being copied out for the administrative assistant at Inverewe to enter the data into the Met Office website.

The weather readings are an important task at Inverewe. Very few readings are missed – not even the original coronavirus lockdown stopped the readings from being taken daily! We do have occasional technical malfunctions but these are rare and have never caused any serious loss of data. This winter, the main problem has been that the box for the batteries kept freezing solid, so it was a bit of a fight to charge the battery!

As the walled gardener, I find the weather readings to be very helpful in knowing when the best time will be for planting out new crops. I can see the daily changes in the soil temperatures, which can affect the growth rate of young plants. I also enjoy quantifying the weather that I have to work in, whether it’s enough to boil me alive or freeze me solid, and I like spotting any trends in the weather, like if spring is springing ... or winter is dragging!

2020 weather statistics

Sunniest day: 30 June – 13.8 hours

Wettest day: 14 September – 36.4mm

Hottest temperature: 1 August – 26.2⁰C

Coldest temperature: 13 February – -1.6⁰C*

*This may not seem that cold for a Highland place, but this is precisely why Inverewe is the amazing garden it is today! Inverewe is protected not only by the north-facing Loch Ewe but also by the effects of the Gulf Stream, which warms the incoming waters. Hence the success of all our exotic plants – and the skills of our gardeners, of course!

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