53.00560 -1.25124 Met Office CIMO Assessed Class 4 Archived temperature records from 1/1/1957
This is an update on Tim Channon’s original 2012 review of this site with some important additional revelations. There are three other reviews that need to be taken into consideration with this site, my recent Pembrey Sands and Winterbourne ones, and more importantly Tim’s excellent appraisal of Met Office enclosures, paving and their relevant effects. The latter is a long technical read but very worthwhile.
Nottingham:Watnall is an important manned Met office site with a full range of instrumentation including Radiosonde launch and tracking facilities. Originally just a rain gauge site installed in 1941 the full facilities were added from 1957 onwards.
Watnall lies to the north west of the very substantial Urban Heat island of Nottingham – population 340,000. Any gentle south easterlies emanating from north or even Saharan Africa will often have tracked over mainland Europe with an almost negligible sea crossing of the English Channel, pass over London and via Nottingham itself onto the site. A good location to record naturally hotter air streams subsequently picking up artificially warmed factors. Readings will no doubt be accurate but unrepresentative of the wider surroundings.
The area immediately under Met Office control has also been physically altered by the Met Office itself with additional structures hemming the screen in. This image below from 2001 predates the Radiosonde portacabins with launch facilities on their roofs installed by the road way to the north east. The entire site is now bordered by buildings and hedges further forming a distinct micro-climate.
With all these compromises the site only meets the quoted “Class 4 (additional estimated uncertainty added by siting up to 2 °C)”. So what is the relevance of Pembrey Sands, Winterbourne and Tim’s work on enclosures to Watnall?
Firstly, the Pembrey screen was shown to be unacceptably located over a fully concreted enclosure. Now consider these recent archived notes for Watnall.
The Met Office do not give any consideration to screen’s proximity to electricity sub stations but agonise over the waste heat from low voltage junction boxes and duly removed some in Watnall in the interests of removing “the number of heat sources” and to improve data integrity! And possibly after having taken note of Tim’s astute calculations decided to lift and remove all the enclosure paving and (it would appear) even the immediate enclosure screening itself. It should be applauded that the Met Office is taking such steps in improving the immediate screen locality. The problem I have is their unwillingness to recognise all the other major detrimental influences – removing a few paving slabs at Watnall whilst simultaneously taking readings over 144 square metres of concrete at Pembrey seems doublespeak to me. They are also seemingly ignoring all the other detrimental factors. I confidently expect the Met Office will shortly reassess this as a Class 3 site quoting the reason as these improvements. So one final look in close up.
The screen is the one to the right in pre-slab removal days…….just don’t ask what the screen on the left in front of the Radiosonde portacabin is – surely not?! It is probably quite innocent but worth noting it is a relatively recent addition – one to keep an eye on.
via Tallbloke’s Talkshop
February 14, 2025 at 04:19AM
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