Strathallan Airfield WMO 03144 – So Close and Yet so Far

56.326418 -3.728807 Met Office CIMO Assessed Class 4 Installed 1/1/1989 archived temperature from 1994.

The CIMO classification of this site as Class 4 confused me no end. The above circle delineates a 100 metre circle in which there is effectively nothing to cause any shade or unnatural effects on the screen. I consulted Tim Channon’s original review of this WMO site (written prior to the release of the Met Office’s official classifications list) and he also judged Class 4. Given my own view was why was this not a Class 1 site warranted serious investigation.

Tim’s review and reader’s contributions revealed the probable reason being the nature of the ground cover.

Such ground cover is always a tricky one to judge, what may be perfectly okay as seen in one image such as the headline current pastureland can be very concerning if cropped differently. As Tim pointed out a tall maize crop is entirely different to a ploughed field or a cereal crop. This comparison took me back to my teenage days walking through wheat fields that were well over waist high whereas now such crops have been modified to grow very much shorter with higher yields. Ground-cover should be <25 cm and typical of the region.

Trawling through google historic imagery revealed the cause of Tim’s concern as evidenced in this image from 1/9/2021

 

Such dramatic changes from being surrounded by a cereal crop to a ploughed field in a day will inevitably cause a major swing in surrounding conditions and have an effect on temperature readings. Additionally with all modern agriculture being mechanised and the now universal use of rapidly reacting PRT instrumentation (this has always been an automatic reporting site) the regular passing of tractors, combine harvesters et alia is likely to be picked up thus unnaturally elevating occasional readings.

Another issue, though one I doubt the CIMO guidelines would reflect, is the nature of the topography. This is an airfield so it is flat (confirmed from the Ordnance Survey contour map) but does sit at the bottom of the shallow valley (at this point) of Machany Water. This could genuinely be an area prone to collecting cooler down flowing air from the valley sides but I have not been able to confirm that. I did find a land assessment report from Angus council but it is 610 pages long – if anyone cares to find out from it they are free to try! https://www.angus.gov.uk/sites/default/files/2017-07/115%20Part4.pdf I would welcome any comments from those with local knowledge of the effects in the area.

One thing that is known is that this site is quite inland and typically records over a wider temperature range than many of the Scottish coastal sites that dominate the nations’ weather stations. It is often the regions warmest or coldest or even both in the same day and seems to vie with Tyndrum for both honours.

In summary, this could very nearly be a perfect site or it may be rather a poor one. On the balance of probabilities it is not the former but I find it hard to write off such an open site unaffected by artificial influences other than agriculture. Detailed study of the readings may reveal more and if treated with caution could well be suitable for inclusion in a new historic temperature record reconstruction.

Codicil: In investigating this site I came across an amazing Youtube newsreel clip regarding the airfield and the crash of a De Havilland Comet being delivered to the (now closed) aircraft museum in 1974. The undercarriage collapsed on landing – mercifully nobody was hurt. Dramatic stuff and well worth watching.

https://www.youtube.com/watch?v=vroy6y03lWQ

Source: https://tallbloke.wordpress.com/2025/03/20/strathallan-airfield-wmo-03144-so-close-and-yet-so-far/