WMO03808, Camborne (a primary Met Office climate and research site)
50 13 06N 05 19 39W
Altitude 87 metres
Estimated Class 4. Fails Class 3 on 6.5% hardstanding within 10 metres, limit <=5%,. Note: this is the first site in this project where met enclosure hardstanding has been considered in detail.
Detailed reasoning for failing Class 1 and 2, and evidence within 10 metres is presented below.
UHI, close site, distance, none, coastal site. Note the site is about 300 metres from the recent dual carriageway A30 and single carriageway former A30, about 1km from the outskirts of Camborne town.
I have spent a week and more on detailed investigation in part as a precursor to reappraisal of already published articles.
The Camborne site can reasonably be expected to follow Met Office best practice although I suspect basic met data is not important at this site. I am mentioning details which might seem trivial, best read as using this site for working out more generally.
The patchwork enclosure lower left of the site is for specialist instrumentation. The radiosonde launch tower and hardstanding is obvious. Wind tower is in the far eastern corner of the site off the main image above.
Panorama from Google Streetview (click for larger)
Site is neat and tidy, wind tower off to the left, radiosonde hut and launch area in front of you, main offices centre (presumably gas heated, tank on the north side) . A chain link fence divides from the field, narrow field margin, in front of you is a very common plant on poor soil (Ulex europaeus, gorse, common gorse, furze) and other things. As near coastal substantial trees are rare, but in my experience of similar locations this is somewhat protected from severe winds which will produce a turbulent boundary layer even under severe storm.
Normal photo here, shows less but you can read the entrance sign
Class 1 problems
If the close site is ignored it might seem reasonable this is a Class 1 site but there are various poor features.
There are two fields. Google aerial reveal they are cropped which almost certainly fails on unnatural ground cover and height. However, Google Street view show they are bare ground some of the time.
Bare field, Stevenson screen visible, some scrub next to fence.
From the road along the western side of the field you can just see the Stevenson screen with the start of a tall scrub hedge.
Further down the road from the prevailing wind we cannot see the Stevenson screen, just the top of the tall instruments.
Here we can see the field to the south is bare earth at this phase of cropping and the south hedge.
It might pass but fails on close site.
The close site problem
The Met Office seem to have standard site designs which include concrete paving, many instruments some on concrete foundations and concrete foundations for a fence, of variable design, closeness and height. For temperature measurement it is supposed in general terms to be over short grass or similar. This is reflected in the WMO document.
I have no access to Met Office sites, too far away anyway so I am trying to figure things out from a distance.
The first breakthrough on deducing what paving existed at Camborne, clearly there in the Google aerial images (see over time), was three photographs..
Radiometer Physics GmbH, page of interest, right hand side, 3rd item.
“UK MetOffice, Camborne / UK
2 × RPG-HATPRO dual profiler
Delivery: March 2007
Various deployments in southern UK
Coastal environment around Camborne”
A browser or external editor can open these at their natural larger size.
Middle image shows the met site left background.
I have been working on a guess that paving was actually ducting covers for underground services, these being AWS. Paving as such tends to the standard sizes of 300mm or 600mm in the UK, 1ft or 2ft in old money, ducting tends to narrower.
I’ve concluded the paving in this special equipment enclosure is 240mm to 300mm wide and might be ducting covers, some of it is curved. A sometimes large Google aerial signature might come from disturbed margins making it seem wider.
A surprise was the fence, is using a strip concrete foundation all around the enclosure. I estimate this to be 300mm wide (1ft) (note the human shoes in the photos); is wider where the paving abuts such as near camera. The fence is a classic oldish English style, concrete posts containing rebar, three steel tension wires and 50mm (2 inch) chain link wired to that. The height seems to be 1 metre, a little strange because today the standard rolls are 900mm or 1200mm. This puts the fence top about level with the Stevenson screen stand, Met Office apparently use 910mm.
I concluded from various evidence including shadows the met enclosure has identical fencing. This later confirmed.
I now aside to the Loftus Met Office site which was quickly covered earlier, here. (opens in new window so that you can switch back and forth)
At the time I noticed the Google Streetview reveals what looks like a concrete paving slab leaning against the site cabin and is in the same photographic plane as the cabin. This seems to be 600mm x 600mm but there is nothing definitely known for a relative measure in the image, so I didn’t take this further. the cabin is about 2 metres long. Fence is probably 7′ 6″.
Camborne met enclosure
By a bizarre stroke of luck I discovered the Met Office have edited their Factsheet number 17. This has been mentioned on this site (here) and a search shows mention in a comment at chiefio’s (here); the photo in the document showing a Virgin 747 from the Heathrow Met Office Stevenson screen.
2010 the Met Office edited the document, to version 01 but undated (PDF metadata reveals the dates), filename changes factsheet17.pdf to Fact_sheet_No._17.pdf
The Heathrow photo has vanished, a photo of the Camborne met site has appeared, exactly what I need now.
National Meteorological Library and Archive Fact sheet No. 17
Observations – Weather and climate change – Met Office
www.metoffice.gov.uk/media/pdf/k/5/Fact_sheet_No._17.pdf Â· PDF file
National Meteorological Library and Archive . Fact sheet 17 — Weather observations over land (version 01) Observations
This photo proved critical. I tried a variety of methods of trying to get a measurement of the paving but I needed to be sufficiently satisfied I am correct before opening my mouth in public.
I still cannot be certain and so what follows is my best attempt which might be wrong.
Camborne site uses 600mm x 600mm paving slabs.
Image (c)Crown Copyright from Met Office Factsheet 17 version 01, last modification, 17th Nov 2011, “Figure 1. Land surface synoptic station
Image has been rotated slightly to make work easier (unneccesary as it turned out). The longest Google aerial image reference line I could manage is 10 metres, centre of fence to centre of paving corner, drawing scaled accordingly.
This forms a known reference line to which items can be scaled according to the discovered vanishing point. VP is neglegable vertically.
Some paving jointing is visible which was a help, some grass is growing over the edges, doesn’t help. Various check measurements have been made and one is left in place: centreline of rain gauge referred back along perspective to reference line and measured. You can check against at least two of the Google aerial dated images using Google Earth.
(If you want the drawing, ask)
Typically paving slabs are smooth surfaced cement, pale and darken with weathering. See the Heathrow photo, bottom right corner. Traditionally paving is bedded on sand. Is this ducting, ie. services underneath? I have no idea but I have seen plenty of site photos where cables seem to go into the soil.
In the photo notice the fence foundations. This seems sunken but according to the Google dated images it remains highly visible. I am assuming 300mm width. It is not low vegetation typical of the region and will be thermally active.
What the metal fencing does is undecidable. I have some evidence it does have thermal effects, as can be seen when ground frost is near fences or hedges. Radiately it might have effect too, as do the many other instruments. This will be minor.
There is a different problem with chain link: it is notorious as a plant support, they love it, all too easy to end up with a wall of vegetation. This should not be a problem at closely maintained sites: I don’t recall seeing this trouble at any of the other sites but few have photos, vegetation outside the enclosure seems to be an altogether different matter.
Those poses a problem for unattended sites and might explain the attempt at a hard surface at the base of the chainlink, stops plants colonising. Weedkiller poses problems over the need for a grass surface generally. Nevertheless weeds are trying to grow at the edge.
Also note the field hedge, confirming it is above the Stevenson screen and will reduce prevailing wind scour as well as be thermally “seen” and also will cast shadow during low evening sun.
Strictly the site is Class 5, air clarity instrument is sufficiently south side of the Stevenson screen to cast a strong if narrow shadow. Worth reminding the reader the WMO temperature error refers to peak error, means are much more subtle. I doubt this would be at all noticeable in even 10 minute data unless the larger heads cause a shadow.
Observation: the variable nature of aerial images at different times has been a mystery but this might be solved by noting the sunken paving and fence foundation. Long distance photography is best done under very clear air conditions, typical post rain frontal system. If the trenches water fill that explains major reflectivity difference.
If that is the case this has side effects on local humidity and entropy, although major effect would be rare: hot concrete, rain shower. WMO classification mentions water surfaces which need to be typical of the area. (but wouldn’t be puddles over concrete)
I conclude it is likely that all paved sites use 600×600.
How I estimated within 10 metres for Class 3 fail. Paving assumed 600mm within enclosure and 300mm for fence, plus areas for equipment exposed foundations. Calculation detail not shown, nor up to 9 other area calcs which might be done. 20metre measure is reference from Google image (measurements by Draftsight).
I have been quite hard on this site, which is stated synoptic yet Camborne is also marked climatic. I hope I have been fair given it is an important Met Office site. Disagree, please speak up.
A lot needs discussing.
Camborne monthly data is computed, 1978 onwards from Met Office
Site must have changed in this time.
Oddly, WMO 3808 Camborne is in GHCN V1 then vanishes, not in V2, Jones, MO. This old data does not match the current Met Office data as closely as I expected. (obviously for common dates)
A lot of information about upper air research exists on the web for the Camborne site. Too much to add here. Lot of it very interesting.
[update 24th Sep]
This is an attempt at presenting a month of data decoded from synop.
Wind is as ever ambiguous, arrow point up is wind around zero degrees, pointing right is around 90 degrees. This usually means 90 degrees as weather vane, from 90 degrees, east wind flowing westwards. Assuming I have things the right way around.
Short of serious coding in C or eg. PDF library I have no way of doing pretty plots, at least software which doesn’t keep kicking back.