RHS Wisley

Posted: September 25, 2012 by tchannon in Analysis, Surfacestation


RHS Wisley (Royal Horticultural Society, Wisley, no WMO ID)

BBC: Hottest July day ever in England (see text)

51.3107735694194,-0.4764187065843351 (Google)

Altitude 37 metres (Google)

Estimated Class 3 but arguably is Class 4. Fails Class 1 and 2 on “Ground covered with natural and low vegetation (<10 cm) representative of the region” within 10 metres and surrounded by open space.

UHI, local, orchards, vegetation, polytunnels, medium, 350m new artificial lake and then new visitor centre, 270m a 10 lane part of the Riply bypass (road), 550 metres end of Wisley airfield runway (disused), distance, 31km centres of London, just outside M25 orbital motorway.


© Copyright 2009 Basher Eyre and licensed for reuse under this Creative Commons Licence. http://www.geograph.org.uk/photo/1171175

Brick pillar with steps is probably for a sunshine recorder.

A Wisley site has weather records from 1904. Obviously there have been major site changes.


This site is widely quoted in relation to UHI. (a later article will mention this)

This is probably a good example of a man-made micro-climate.


Main question about Class 3 or 4 is I think whether there are >5% objectionable items in the annulus between 5 metres and 10 metres. I rather doubt the WMO guidelines had these kinds of problems in mind, such as cordon trained fruit trees or fences.

On a wider scale the polytunnels are encroaching, see Google time-line.

Essentially this site has poor exposure; radiately (shouldn’t need a raised sunshine recorder) and for wind.

“Quite often when we do have heatwaves, Wisley for some reason does become one of the hottest areas,” Tomkins said.

“Gardeners at the 240-acre site had started work before 6 a.m. to avoid the worst heat of the day, while the air-conditioned apple store at the garden proved irresistible for many staff.”

The nearest reasonable site but still surrounded by aerodrome runways is South Farnborough. Several more not far away but unfortunately Wisley is not part of the immediate data network so on. Only the Met Office could provide the detail data.

An initial look at nearby stations shows a widespread data disruption before and after the peak on 19th July 2006 (*). There is however a suggestion in the data there might have been an abrupt wind swing and given the massive area of concrete and asphalt close by >0.25 sq km this might be an explanation. Going on other stations 33C to 35C is more reasonable. (I might add more detail on this later, not ready to do this now)

When I looked at the available metadata there is no record of a thermometer check. Gravesend-broadness for example has such an entry.

* An explanation might be disruption of VHF radio propagation.

There seems to have been a spectacular event mid July 2006 and as usual this is weather related.

[I might have jumped too far for many readers:  weather information is broadcast by radio; some radio wave propagation is affected by atmospheric and ionospheric electrical conditions; this is related to weather and sometimes solar conditions, as well as day/night and season.

The following link is to a radio amateur site, where lower down the page there some exceptional conditions July 2006 are shown]

It looks like there were severe conditions



Camborne shows it similarly the day before.

Looks to me like several days of building heat which is about to collapse, as it did.

Disruptions to communications critical to air safety in the day and age is a matter of concern. Never mind, fuel here for anyone wanting a weather event candidate for close examination.

  1. caz says:

    Another geograph photo from later in the year here.Note the visitor information signs just inside the fence.


    A couple of photos of the sunshine recorder (attrbute reproduction) Is it still used or has an automatic sensor (see picture above) been fitted and it has been left to remain as it is quaint?


  2. tchannon says:

    Presumably it is, manual is entirely possible.

    Marked as non-standard AWS, has some stuff on monthly forms (I think). No mention of automatic rad values.

    The flickr image uses the word “was”, pic shows no paper in there so a question is begged.

  3. caz says:

    It’s a was. Gardeners’ Question Time went to the Wisley weather station in August. From minute 28. There’s also a photo of the sunshine recorder with a caption “This antiquated device would be used to measure sunlight intensity.”