Originally Posted by
The Oberon
Langley, serious, but maybe dumb, question. It seems to me, a layman, that a lot of the places where 40deg.was exceeded are subject to non meteorological influences making it seem hotter. I am aware that thermometers are contained in louvered boxes but when these boxes are sited on a large concrete/tarmac area with hot jet exhaust coming from aircraft movements, Coningsby/Heathrow for example, this is going to make things seem hotter or is it my imagination?
In a very few words, yes, many a measurement is made in less than 100% correct exposure.
There is often some tension between where the S Met O would like his instruments, and the operational needs. The "old fashioned" but essential kit in a grassed enclosure must usually be attended every hour/ six hours/ 24 hours by the observer so has to be handy [I once lost an observer in fog but that is another story]. What has happened at many airfields is that the instrument enclosure, initially ideally situated from a purist point of view, has been encroached upon by essential operational priorities. Jet efflux fortunately is not a major villain as taxiways have to be minimum distances from obstructions. Acres of tarmac ............ even car parks are known to exaggerate temperature readings. For some known problems there are empirical adjustments that can be made, most cannot.
Once a year S Met O's boss is/ was supposed to visit and do a detailed inspection ....... often brings his/ her/ their own expert observer along. Many howlers over the years: anemometer on a dwarfish mast, anemometer too near disturbances to free flow due to a new-build hangar, louvred screen fitted back to front, screen not screwed in position.
And then there is the light-hearted Ho Ho Ho! of passing folk passing water into the rain gauge.
One thing you can be sure of: the quality control people at HQ put any new claims for records through the ringer before accepting them