Loch Glascarnoch WMO03031 – an example of two of the determinants of weather station locations.

57.72491 -4.89556 Met office CIMO Assessed Class 4 Temperature records from 1/1/1992

Loch Glascarnoch  is a 7.2 km-long (4.5 mi) reservoir in the Scottish Highlands between Ullapool and Inverness. The reservoir was built by the North of Scotland Hydro-Electric Boards  as part of the Conon Hydro Scheme, and is dammed on its eastern end. The weather station itself lies just over a kilometre north east of the extreme north western edge of the reservoir.

The determinants of weather station locations are frequently non meteorological in the purest sense and Loch Glascarnoch is a typical example of such factors.

This site was one of the many sophisticated and extensively equipped Synoptic sites developed in the 1980s to improve immediate weather forecasting. Forecasting is much more involved with changes of weather conditions such as wind speed and direction, air pressure, precipitation and visibility etc, with accurate historic recording of temperature being very much a secondary consideration. In fact temperature readings really were much more concerned with indicators of ice/frost formation than whether or not sunbathing was an option for the next day.

Although many differing institutions have weather monitoring points (Highways departments, hydrological units, aviation, coastguards and ports, agricultural research centres et alia) the Met Office is still the dominant authority and is charged with “Climate” recording. On this latter basis, such “Climate” sites should be located with accurate recording of temperature readings representing the widest possible areas. The determinants of siting should really be based on meteorology and not simply “convenience”. That was what the CIMO regulations were intended to codify.

So what has this to do with the Loch Glascarnoch site? The choices of location here are actually very simple and visible in the street-view image below.

The first and most obvious reason is the A835 road. Loch Glascarnoch was an automatic site from original installation so does not require daily observation visits. The essential point about such sites is that they can be remotely located as human visits are only limited. Nobody was likely to regularly trek to Aonach Mor for example.

Ease of access for occasional maintenance should not really override meteorological accuracy if accurate climate history reporting is the aim. For forecasting purposes it does not make a critical difference so for initially Synoptic sites it was not a concerning issue. This site is by the road for no other reason than convenience.

The road is, however, not the critical factor, the wires at the top of the image very much are. Remembering back to the 1980s, automation facilities required significant amounts of power. Whilst a modern solely climate reporting site can get by with a small solar photovoltaic panel and battery to run mobile data comms from a little box on the side of the screen stand, the Synoptic sites back then needed full blown mains power. Some sites had to run off separately sited generators (i.e. Manston) with all the attendant refuelling visits, servicing etc. Anywhere that happened to have a passing overhead electricity supply was clearly a very good candidate. The vicinity of electric power plants is always a good site for overhead cables (such as at Cassley) thus Synoptic weather stations appeared at easy to install and service sites rather than the best locations for climate purposes. This does rather explain the likes of Bingley No 2.

The Met Office themselves used to acknowledge the re-purposing of sites intended for different purposes into an alternative role and the attendant problems.

“It is unavoidable that some sites do not meet all these requirements, particularly where a station set up for one purpose gradually takes on a different role, for example an airport site originally established for aviation observing may become a key synoptic or climate station while suffering the effects of urbanisation. A few sites are in city centres and may be unsuitably located close to large obstacles or even on the roof of a building.”

Loch Glascarnoch is assessed by the Met office as “Class 4 (additional estimated uncertainty added by siting up to 2 °C)” – it is difficult to disagree with that appraisal either way. It was never intended to be a “climate reporting station” so analysing its approximate readings to the second decimal place over 30 year periods rather seems a fool’s errand.

I assert that the “Climate Science” section of the Met Office should “get a grip” on reality and start critically assessing the quality of its raw data before torturing numbers through computer programmes to produce absurd end results. Perhaps they could consult real world independent meteorologists with no ideological or political axe to grind – they might just find most of their sites are inappropriate for climate science purposes. A final reminder……….who feels this sort of synoptic site is really suitable for historic temperature records?

Source: https://tallbloke.wordpress.com/2025/12/18/loch-glascarnoch-wmo03031-an-example-of-two-of-the-determinants-of-weather-station-locations/