Over at Tallbloke’s Talkshop, moderator Tim Channon wondered about this regularly hot station reported in the news:
An often appearing name in the BBC news as the hottest place in the country is Gravesend but the true location of the Met Office thermometer is a mystery. By chance I followed up today and discovered a new snippet of information.
From the BBC – 2003: Britain swelters in record heat
Britain has recorded its hottest day ever as the temperature soared to 38.1C (100.6F) in Gravesend, Kent.
The record has actually been broken twice today. The first place to beat the previous record of 37.1C (98.8F), set in Cheltenham in 1990, was Heathrow Airport where the temperature earlier today registered 37.9C (100.2F).
Then an even higher temperature was recorded in Kent, making today the hottest day since records began about 130 years ago in 1875.
Here’s another example: Gravesend sizzles in late September sun
It’s definitely time to get that sun screen out as Gravesend is officially one of the hottest places in the UK today.Temperatures reached 28.6C this afternoon, making it Kent’s warmest September 30 ever!
Clearly, it is a leading hot spot.
So what does the Met office say about how official weather stations should be sited? They have it right here:
http://www.metoffice.gov.uk/learning/science/first-steps/observations/weather-stations
And what does the officially hottest station in the UK at Gravesend look like?
The process of discovery of this station was a long one, aided by a global discussion at Tallbloke’s Talkshop. This Bing Maps aerial view I found and posted at TB’s confirmed to me that there was in fact a Stevenson Screen there:
Source: http://binged.it/RqV8Cv
And that lead commenter “Caz” to make the discovery of the photo:
Caz says:
The Bing Link cracked it for me. It was obvious looking at the shadows that the weather station, transmitter and radar tower were sat on a level depression protected on three sides by banking ie they had their own micro climate.
I then selected Ordnance survey mapping and confirmed that this was indeed a place with a micro climate as the banks are clearly marked on the OS map. But it gave one other vital piece information, the location is Broadness Salt Marsh.
Just a few steps later and a Google of Broadness Salt Marsh and I had the picture and all the information required to see that this weather station is a dud. Note the banking, brick power building with ventilation equipment and the weather station.
http://commons.wikimedia.org/wiki/File:Broadness_Radar_-_geograph.org.uk_-_48941.jpg
The Met Office should hang their heads in shame and also the BBC for reporting the temperatures recorded by this station. Well done chaps I hope you can get the message out to the wider world. If anyone lives in that area the site looks easily accessible.
Getting the message out to the wider world is what we do here at WUWT, happy to help.
Now here’s the interesting thing about this station, it has a trifecta of siting issues, and not just from the air conditioner and brick building. Look at the location located by Tim Channon:
That spit of land juts into the Thames. What is nearby? Channon writes:
This is east of London, is the tidal lower Thames close to the estuary. It is going to be permanently humid, including any effect from the elevation of the temperature of the Thames, heat from London.
Industrial activity is obvious as is close dense residential.
Go towards London (left) and within 5 km is the non-motorway section of the M25 London orbital “motorway”, blue on the map. This is 8 lanes all told with queues a lot of the time, is a toll road. Queen Elizabeth bridge southbound and the Dartford tunnel northbound. Both expel heat into the air, a bridge and ventilated tunnel. South side to the left of that see the bright circles? Heavy oil storage tanks, river pontoon for fuel delivery tankers. Next across is the RWE Littlebrook power station. Being oil is probably not run continuously, about 1.4GW output and has additional gas turbine generator sets. This will eject circa 2GW of waste heat, up prevailing wind. RWE web page on station, head photo is looking east toward bridge and weather station.
Next to the left is a wee and poo plant, also tends to be warm stuff. I expect the sludge is tankered into the outer estuary for disposal. (used to be the case)
Little Reach Sewage Treatment plant, run by Thames Water. Photo looking west, can see the edge of the power station.
Is that all?
Figure 3Just off the right of the previous image, north side of the river is… another power station. Top of image here is the electricity output site.
RWE Tilbury Power station, coal fired, hence the pontoon for delivery and black stuff but the RWE web page says the site is being converted. Looks like another 2 to 3GW of waste heat, east winter winds or blocking highs have this one upwind. I notice the RWE photo doesn’t want to show much.
Converting to biomass? I bet the conversion efficiency is lower than conventional fuels, therefore even more waste heat.
There are other power stations a little further away, at least two major ones to the east. (there because of the river, coal delivery)
All this sparkery, I’ve not reached the end yet.
Figure 4
So what is that? Met site is top right. Four piles at the base, is a large power grid pylon, can look bizarre from an aircraft (these are aerial photos, not satellite).
Electricity transmission is not 100% efficient, the lines get hot, are a compromise. Actual lines are aluminium with a steel core. The alignment, this is a river crossing.
Other side are several sites
I pointed out that:
It may be that the station is affected by heated water discharge from the power plant and the sewage plant into the river. Being on that spit of land it has water on three sides.
Only some water temperature measurements will tell for sure.
But another commenter pointed out:
Scute says:
Following up on Anthony’s comments, I have been digging a little, using Tim’s links. The Littlebrook power station just to the west of the QE Bridge does discharge warm water from its condenser into the Thames. The intake and outflow are the two circles in the Thames, visible in the Bing ariel view if you scroll left. The PDF document on the site that Tim linked says:
“The condensate is pumped back to the boiler for reuse and the cooling water [i.e. now warm water] is returned to the river.”
This must be several hundred megawatts at least, given the fact that it is cooling something approaching 800kg of condensate per second at full operating capacity. This would be in addition to the heat lost up the chimney during oil combustion which may or may not drift over the station in question. What is certain is that a large portion of the condenser outflow ends up bathing the station on three sides. Even if there is some convective/turbulent mixing, the mixed water will retain this heat energy quite well at or near the surface albeit as lower grade heat. Since water has a specific heat capacity four times that of air and the mass of air directly above the Thames is much less than the now-mixed surface layer, it means that the water surface can heat the air above it to the same temperature without dropping in temperature itself, or at least by a negligible amount. This amounts to a very reliable, permanently elevated heating source, one which is likely to be elevated further when the power station cranks up in the evening….I noticed that Thursdays temperature graph for Gravesend showed an anomalous rise at 6PM. I was waiting for today’s 6PM update to see if it happened again but as of starting this comment it hadn’t come through. It might warrant monitoring over the next few weeks or months- though tides will dull or enhance the effect I should think.
Speaking of tides:
tchannon says:
Scute,
Hundreds of MW, probably upper, however, oil is an unusual fuel so I suspect this is peak times only. They mention gas plant but seem to casually throw this in without detail. Presumably a similar power and the thermal efficiency is a little better.
More subtly, I mentioned this is lower reaches, the Thames is a small river with low flow: it is tidal.
For this reason any cooling outfall from the station nominally downstream will flow back upstream… and cooling upstream will stagnate in a pool of water.
Goodness knows the effect, for all I know, none.
So, I decided to have a look at that tidal issue. Again Bing aerial view is our friend:
Source: http://binged.it/NblzVn
Note the exposed dark mudflats. What sort of natural surface has the lowest albedo, and thus absorbs the greatest amount of solar radiation?
Dark and wet…like a mudflat on two sides of the station as seen in the Bing aerial view.
The new “hottest ever” record set in the UK was on August 1o, 2003.
I downloaded the tide data for the outlet of the Thames, Sheerness for that day from the UK National Oceanography center. Times are local to the station, +1 GMT.
21217) 2003/08/10 00:00:00 4.356 0.081
21218) 2003/08/10 00:15:00 4.101 0.063
21219) 2003/08/10 00:30:00 3.840 0.048
21220) 2003/08/10 00:45:00 3.581 0.038
21221) 2003/08/10 01:00:00 3.325 0.032
21222) 2003/08/10 01:15:00 3.065 0.018
21223) 2003/08/10 01:30:00 2.825 0.018
21224) 2003/08/10 01:45:00 2.592 0.015
21225) 2003/08/10 02:00:00 2.372 0.013
21226) 2003/08/10 02:15:00 2.168 0.013
21227) 2003/08/10 02:30:00 1.983 0.014
21228) 2003/08/10 02:45:00 1.824 0.022
21229) 2003/08/10 03:00:00 1.690 0.035
21230) 2003/08/10 03:15:00 1.567 0.040
21231) 2003/08/10 03:30:00 1.469 0.051
21232) 2003/08/10 03:45:00 1.385 0.057
21233) 2003/08/10 04:00:00 1.308 0.053
21234) 2003/08/10 04:15:00 1.245 0.044
21235) 2003/08/10 04:30:00 1.196 0.029
21236) 2003/08/10 04:45:00 1.173 0.016
21237) 2003/08/10 05:00:00 1.186 0.011
21238) 2003/08/10 05:15:00 1.235 0.010
21239) 2003/08/10 05:30:00 1.325 0.015
21240) 2003/08/10 05:45:00 1.458 0.028
21241) 2003/08/10 06:00:00 1.610 0.025
21242) 2003/08/10 06:15:00 1.805 0.037
21243) 2003/08/10 06:30:00 2.011 0.038
21244) 2003/08/10 06:45:00 2.228 0.037
21245) 2003/08/10 07:00:00 2.461 0.046
21246) 2003/08/10 07:15:00 2.686 0.046
21247) 2003/08/10 07:30:00 2.909 0.047
21248) 2003/08/10 07:45:00 3.134 0.053
21249) 2003/08/10 08:00:00 3.350 0.054
21250) 2003/08/10 08:15:00 3.577 0.067
21251) 2003/08/10 08:30:00 3.791 0.068
21252) 2003/08/10 08:45:00 4.011 0.075
21253) 2003/08/10 09:00:00 4.226 0.079
21254) 2003/08/10 09:15:00 4.436 0.082
21255) 2003/08/10 09:30:00 4.645 0.095
21256) 2003/08/10 09:45:00 4.842 0.110
21257) 2003/08/10 10:00:00 5.019 0.127
21258) 2003/08/10 10:15:00 5.171 0.149
21259) 2003/08/10 10:30:00 5.290 0.173
21260) 2003/08/10 10:45:00 5.365 0.196
21261) 2003/08/10 11:00:00 5.387 0.212
21262) 2003/08/10 11:15:00 5.358 0.226
21263) 2003/08/10 11:30:00 5.272 0.230
21264) 2003/08/10 11:45:00 5.125 0.218
21265) 2003/08/10 12:00:00 4.942 0.207
21266) 2003/08/10 12:15:00 4.718 0.187
21267) 2003/08/10 12:30:00 4.475 0.171
21268) 2003/08/10 12:45:00 4.213 0.153
21269) 2003/08/10 13:00:00 3.937 0.133
21270) 2003/08/10 13:15:00 3.670 0.128
21271) 2003/08/10 13:30:00 3.404 0.127
21272) 2003/08/10 13:45:00 3.140 0.126
21273) 2003/08/10 14:00:00 2.882 0.126
21274) 2003/08/10 14:15:00 2.630 0.122
21275) 2003/08/10 14:30:00 2.394 0.121
21276) 2003/08/10 14:45:00 2.172 0.116
21277) 2003/08/10 15:00:00 1.969 0.110
21278) 2003/08/10 15:15:00 1.791 0.107
21279) 2003/08/10 15:30:00 1.628 0.097
21280) 2003/08/10 15:45:00 1.508 0.109
21281) 2003/08/10 16:00:00 1.397 0.112
21282) 2003/08/10 16:15:00 1.302 0.114
21283) 2003/08/10 16:30:00 1.223 0.116
21284) 2003/08/10 16:45:00 1.156 0.113
21285) 2003/08/10 17:00:00 1.110 0.112
21286) 2003/08/10 17:15:00 1.084 0.108
21287) 2003/08/10 17:30:00 1.094 0.111
21288) 2003/08/10 17:45:00 1.141 0.116
21289) 2003/08/10 18:00:00 1.231 0.126
21290) 2003/08/10 18:15:00 1.360 0.135
21291) 2003/08/10 18:30:00 1.528 0.147
21292) 2003/08/10 18:45:00 1.720 0.151
21293) 2003/08/10 19:00:00 1.946 0.164
21294) 2003/08/10 19:15:00 2.187 0.177
21295) 2003/08/10 19:30:00 2.436 0.189
21296) 2003/08/10 19:45:00 2.684 0.197
21297) 2003/08/10 20:00:00 2.928 0.201
21298) 2003/08/10 20:15:00 3.180 0.213
21299) 2003/08/10 20:30:00 3.433 0.225
21300) 2003/08/10 20:45:00 3.685 0.235
21301) 2003/08/10 21:00:00 3.930 0.236
21302) 2003/08/10 21:15:00 4.178 0.237
21303) 2003/08/10 21:30:00 4.425 0.237
21304) 2003/08/10 21:45:00 4.670 0.238
21305) 2003/08/10 22:00:00 4.902 0.236
21306) 2003/08/10 22:15:00 5.133 0.250
21307) 2003/08/10 22:30:00 5.337 0.261
21308) 2003/08/10 22:45:00 5.507 0.273
21309) 2003/08/10 23:00:00 5.637 0.287
21310) 2003/08/10 23:15:00 5.715 0.299
21311) 2003/08/10 23:30:00 5.741 0.313
21312) 2003/08/10 23:45:00 5.695 0.310
As you can see from the data, the low tide was about 1.08 meter at 5:15PM local time.
I looked for historical data for Gravesend, which has a tide gauge according to the London Port authority, but I couldn’t find any actual data. So I had to rely on a tide prediction program. Given that Gravesend is well upstream from Sheerness. one would expect the tide to be lower, since it has an higher elevation difference, which is why the Thames flows east. I downloaded the wxtide32 program since it had a location for Tilbury dock, not too far away from Gravesend.
The tide prediction for Tilbury Dock for 8/10/2003:
Tilbury Dock, Thames Rvr
Sheerness, England - READ flaterco.com/pol.html
+ Corrections: High(+0:20 +1.50) Low(+0:20 -1.00)
Units are meters, initial timezone is CUT
August 2003 low is 0.2m, high is 6.2m, range is 6.0m.
Predicted historical low is -2.1m, high is 8.4m, range is 10.6m.
Sunday Monday Tuesday Wednesday Thursday Friday Saturday
07-27 07-28 New 07-29 07-30 07-31 08-01 08-02
L0523 1.0 H0001 5.7 H0043 5.9 H0123 6.0 H0203 6.1 H0245 6.2 H0327 6.2
H1140 5.6 L0606 0.9 L0646 0.8 L0726 0.7 L0808 0.7 L0852 0.6 L0934 0.7
L1753 0.9 H1220 5.8 H1258 5.9 H1335 6.0 H1413 6.1 H1453 6.2 H1533 6.2
L1837 0.7 L1918 0.5 L2000 0.4 L2043 0.3 L2126 0.3 L2207 0.3
08-03 08-04 FQtr 08-05 08-06 08-07 08-08 08-09
H0409 6.1 H0452 6.0 H0537 5.8 L0014 0.7 L0111 0.8 L0221 1.0 L0344 1.0
L1014 0.8 L1054 0.9 L1136 1.0 H0629 5.6 H0735 5.4 H0856 5.4 H1010 5.6
H1614 6.1 H1656 6.0 H1743 5.9 L1228 1.1 L1333 1.2 L1452 1.2 L1622 1.0
L2248 0.4 L2328 0.5 H1840 5.7 H1959 5.5 H2129 5.6 H2241 5.8
08-10 08-11 Full 08-12 08-13 08-14 08-15 08-16
L0500 0.9 L0600 0.8 H0034 6.2 H0121 6.2 H0204 6.2 H0244 6.1 H0321 6.0
H1112 5.8 H1206 6.0 L0648 0.7 L0730 0.7 L0809 0.8 L0844 0.8 L0918 0.8
L1734 0.7 L1830 0.4 H1253 6.1 H1336 6.1 H1415 6.1 H1451 6.1 H1524 6.0
H2341 6.0 L1918 0.3 L2001 0.2 L2041 0.2 L2119 0.3 L2153 0.4
The plot for Sunday 8-10-2003:
The low tide of 0.7m was reached late in the afternoon, about 5:34PM.
Here is what an aerial view of the station and the point looks like at low tide of similar magnitude:
As you can see (if you click image for the closeup) the boatyard to the SW is completely dry. Mudflats are around the station every direction except SE.
So, depending on wind direction that day, combined with the low tide, the station may have picked up some heated air from the mud flats. Unfortunately the station does not record wind data. Given the nearby stations (such as London City) show a shift of wind direction to northerly after about 5PM local time on that date, it is quite possible though:
All news reports I read said the high temperature in Gravesend occurred in late afternoon on Sunday August 10th. The historical data available from the Met Office is rather slim. So if somebody knows where to find the exact time the high temperature was recorded, that would help solve this mystery.
One final thing, this IR map shows that area of Kent near Gravesend to be one of the warmer places around London, warmer even than the cityscape of London itself:
So to summarize the surroundings of this station:
- City UHI nearby
- Industrial area surrounding it
- River with heated water from power plant and sewage plant dumped into it nearby
- Surrounded by water on three sides
- Surrounded by low albedo (high solar absorbing) mudflats nearby with low tide near time of Tmax
- Sited at a radar station with waste heat exhaust systems clearly visible
- Sited directly next to a sidewalk
No wonder it is consistently a high temperature record breaker! On that day August 10 2003, it was warmer than Heathrow Airport where the temperature earlier registered 37.9C (100.2F).
UK residents: Feel free to add any information you can find that will help. Still looking for the high temperature time on 8-10-2003 at Gravesend.
UPDATE: I’ve located this photo also. What looked to be a sidewalk turned out to be a big chunk of concrete. Heat sink anyone?
This photo is from a Royal Meteorological Society publication, they apparently didn’t want the world to see the other nearby issues related to the radar station.
More on that publication, and how I’ve caught the Met Office in a lie, coming soon.
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It’s not a question of being a warmist Anthony. It is a question of being rational and realistic.
Your story has made a mole hill into a mountain. Do you agree that the radar building isn’t a problem based on the documents you reference?
REPLY: No.
Here we have the Met Office explaining Gravesend’s record readings with a lack of measurement sites: http://www.gravesendreporter.co.uk/news/the_reason_behind_gravesend_s_record_breaking_temperatures_1_1466764
Wikipedia blames rail construction works: en.wikipedia.org/wiki/Gravesend,_Kent#Climate
As others have remarked, the low albedo mudflats capturing heat on a sunny day is probably the reason for the record highs at Gravesend.
Fairly easy to test. just measure the temperature adjacent to the recording station and out on the mudflats on a hot sunny day.
Would be a good high school science project. Although clearly beneath the dignity of a real climate scientist.
As someone who has actually spent a lot of time working with both weather and navigation radar the chances of it warming anything outside of 3 meters radius is slim to none. Not so for military land based radar which will brown your bacon much farther off. That radar scanner is just not capable of producing alarming heat. The PRF (google it) and peak power produce an average heat that will surely not boil water nor even harden an egg. The vertical beam width of that type of antenna is very large, reducing the focused beam intensity significantly. They were designed for pitching and rolling vessels at sea. And weather just doesn’t require a lot of energy to watch on radar. I’ve painted the moon with a 20 kw peak power S-band radar from Plainview, Texas. The pulse power, given the repetition rate, is very low. But you can watch the moon rise with those peanut whistles and a 20′ dish. It just isn’t the equivalent or even close to a microwave oven where the waves are bouncing around in a tuned box.
The building is on the NW corner of the site. The screen is in the SE corner.
The prevailing wind in Gravesend is from the SW. Most of the time the heat from the building will be blown away from the screen.
I note (as I have also done at TB’s TS) this story from The Gravesend Reporter, Wednesday, August 1, 2012: ‘The reason behind Gravesend’s record-breaking temperatures’.
Here’s the whole thing (since it’s so short):
[snip . . sorry but you will need to provide a link as there can be difficulties with copyright if articles are just clipped and pasted. Those are difficulties that Anthony can do without . . thanks . . kbmod]
So, to be fair, it’s reasonable to note that someone from the Met Office appears to be the main source for this little local news piece, and that he was happy to draw attention to the effect of siting… Congrats due to the reporter, one Joshua Fowler?
It’s also worth paying attention to Tallbloke’s important caveat, not repeated here, that the Gravesend site is /not/ a formal international climatic station — no doubt /because/ the Met Office are already onto the impact of UHI. If Gravesend regularly gets reported as being hotter than else where, might that not be due to the fact that it is actually often hotter there than elsewhere? (UHI from the Greater London conurbation being likely to surpass other local factors effecting temperature in the immediate vicinity). The burden of proof must be carried by those who want to demonstrate a different interpretation, mustn’t it?
The Gravesend Reporter explained all this a few weeks ago — linked by Omnilogos above. To be fair, the journalist’s main source was a guy from the Met Office’s: who was very happy indeed to point out that the high readings from the Gravesend stations are probably attributable to the London UHI. Surely this needs to be taken into account when considering the Met Office’s position on this site? After all, it’s not, as Tallbloke points out, an international station. So the real problem is not so much the existence of the station (why /not/ measure the temperature east of London?), but the use of the data by the BBC. On somedays Gravesend may well be the hottest place in England — because of its location. Records days of heat made headlines in the UK long before Climate Change. So this isn’t this really a story about the way journalists use data, rather than how meteorologists generate it?
A paper published by The RMetS concludes:
It is the considered opinion of the authors
that sufficient doubts remain with regard to
local site influences that the 38.1 °C maximum
reported from Gravesend on 10
August 2003 must be regarded as likely to
be slightly in excess (by perhaps 1 degC) of
a value more representative of the locality.
http://onlinelibrary.wiley.com/doi/10.1256/wea.10.04B/pdf
NO. And the reason is important. Human habitations are a tiny percentage of land area, not to mention total global area. So taking UHI contaminated data results in disproportionate weighting of it, since it must be “smeared” out to cover wide uninhabited areas. As for the actual emitted heat, it’s trivial in the global budget, which just emphasizes how important it is to expunge every trace possible of UHI influence from global estimates.
Fair enough. But reconceptualize the BBC as a policy pressure group/agency, and journalists as propagandists.
Now which aspect of the mis-reporting do you think is more important?
Here’s another picture of the Site. If you blow it up to 200% you can clearly see the Radar mast and brick building beneath it on the left and the large triangulation tower to the right. The Stevenson screen which of course is not visible is between the tower and the earth bunding behind. On a sunny day that must be a tremendous heat trap and influenced by the mud flats, old hulks and abandoned cars, Behind all that is a concrete factory.
http://www.geograph.org.uk/photo/1558134
Hi there I actually live in Gravesend and as your reasearchers have found it has UHI and many other factors as well to produce high temps ..its also a nice place ful of history and warmth..come and visit us ..soon to be renamed Gravesend – on – Thames !
Anthony.
some quotes from Leroy et al
Class 1:
· Flat, horizontal land, surrounded by an open space, slope less than 1/3 (19°).
· Ground covered with natural and low vegetation (< 10 cm) representative of the
region.
· Measurement point situated:
o at more than 100 m from heat sources or reflective surfaces (buildings,
concrete surfaces, car parks etc.)
o at more than 100 m from an expanse of water (unless significant of the
region)
o away from all projected shade when the Sun is higher than 5°.
A source of heat (or expanse of water) is considered to have an impact if it occupies more than 10 % of the surface within a circular area of 100 m surrounding the screen, makes up 5% of an annulus of 10m-30m, or covers 1% of a 10 m circle.
Class 2
· Flat, horizontal land, surrounded by an open space, slope inclination less than 1/3
(19°).
· Ground covered with natural and low vegetation (1 km). A method to judge if the relief is representative of the surrounding area is the
following: does a move of the station by 500 m change the class obtained? If the answer is no, the relief is a natural characteristic of the area and is not taken into account.”
I suggest this excludes motorways 4 Km away, Sewerage Treatment plant 5 km away, powerlines 100’s of meters away (it would be nice if you quantified the heat lost from those powerlines and converted that into watts/M^3 of the air volume between the powerlines and the station to highlight its impact (or lack of it) on the met station site.
These are characteristics of the site and at Class 1/Class 2 this station will do a good job of measuring the local temperature.
Certainly the surrounding industry, river etc may be adding a UHI impact for the site, but as TallBloke comments “…THIS SITE HAS EXISTED SINCE 1995…”. And the features you have highlighted would all be at least that age. So any more local aspects of UHI will not have changed in any significant way over that time and thus would have negligible impact when this site is included in calculations of temperature anomalies.
Thats the whole point of using anomaly based calculations. They allow us to not need to worry about site biases, only worrying any TIME-BASED CHANGES in the biases.
Gravesend is around 35 km from the centre of London, and lies outside the ring road – the M25 vivible on the left of your 3rd image. And as anyone who has been to London knows, the M25 does not run through dense suburbia. It mainly traverses semi-rural land. So a fair distance from London and its UHI effect.
Here is the Wikipedia entry for Climate at Gravesend
“On 10 August 2003, Gravesend recorded one of the highest temperatures since records began in the United Kingdom, with a reading of 38.1 degrees Celsius (100.6 degrees Fahrenheit),[9] only beaten by Brogdale, near Faversham, 26 miles (42 km) to the ESE.[10] Brogdale, which is run by a volunteer, only reports its data once a month; Gravesend which is a Met Office site reports its data each hour.[11]
One explanation for the phenomenon was the large amount of earthworks in connection with High Speed 1, which had exposed a great deal of the local sandy soil, which absorbed more sunshine, although with the geology being made up of mostly chalk in this area adds little weight to this explanation.[citation needed]
Gravesend as a rule inherits a more continental climate like the rest of Kent, Essex and East Anglia rather than the usual maritime oceanic climate the West of the UK experiences. It is therefore less cloudy, drier, and less prone to Atlantic depressions with their associated wind and rain than more westerly locations of the UK.
Gravesend and the surrounding area is relatively dry, especially in comparison to much of the UK, due to rainfall being light and patchy by the time it reaches the region. Heavy rain usually comes up from France.
In the winter, snow is not uncommon and like much of the area, it will inherit more of the continental winters, tempered slightly by the Jet Stream and the coastal location.
Gravesend continues to record high temperatures in summer, sometimes reaching country-wide records, recently including the warmest day of 2011, when temperatures reached 33.1 degrees.[12] Additionally, the town holds at least two records for the year in 2010 of 30.9 degrees[13] and 31.7 degrees.[14] Another record was set during the Autumn 2011 United Kingdom heat wave with 29.9 degrees, the highest temperature ever recorded in October in the country.[15]
The Kent Downs lie to the south of Gravesend, although it is not known if this causes Gravesend to experience the effects of Foehn Winds that occur as a result of adiabatic warming. This foehn effect seems most likely to occur during a southerly wind flow because of the location of the hills in relation to the town, and indeed it is during times of southerly winds that high temperatures would normally occur anyhow.
The weather station, coded 03784, is on the Broadness Salt Marsh at TQ 60657 76470 51°27′52″N 0°18′41″E. It is at the foot of a triangulation mast, on the river bank at St Clement’s Reach, 3m above mean sea level but actually not on the Gravesham District Council area but in that of Dartford.”
Perhaps local factors may have influenced the climate at Gravesend. But not the nature of the observation station. It is measuring what is happening there.
So what exactly was the point of this post again? I thought you were working on your paper, looking into TOBS factors etc.
REPLY: “These are characteristics of the site and at Class 1/Class 2 this station will do a good job of measuring the local temperature.”
LOL! Umm you missed the concrete pylon and the building nearby, Can’t just ignore those, unless of course you are part of the “skeptical science” crowd. The station is class 4 unacceptable, sorry.
And yes, we’ve solved the TOBS issue, but you’ll dismiss that too I’m afraid. This is your fate as an excluder. – Anthony
Anthony. For some reason my earlier post had a section missing from the centre of it where I did some simple calculations in support of my contention that this a Class 1/Class 2 site. Lets try again, with the 1st half of my comment:
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Some quotes from Leroy et al
Class 1:
· Flat, horizontal land, surrounded by an open space, slope less than 1/3 (19°).
· Ground covered with natural and low vegetation (< 10 cm) representative of the region.
· Measurement point situated:
o at more than 100 m from heat sources or reflective surfaces (buildings, concrete surfaces, car parks etc.)
o at more than 100 m from an expanse of water (unless significant of the region)
o away from all projected shade when the Sun is higher than 5°.
A source of heat (or expanse of water) is considered to have an impact if it occupies more than 10 % of the surface within a circular area of 100 m surrounding the screen, makes up 5% of an annulus of 10m-30m, or covers 1% of a 10 m circle.
Class 2
· Flat, horizontal land, surrounded by an open space, slope inclination less than 1/3 (19°).
· Ground covered with natural and low vegetation (1 km). A method to judge if the relief is representative of the surrounding area is the
following: does a move of the station by 500 m change the class obtained? If the answer is no, the relief is a natural characteristic of the area and is not taken into account.”
I suggest this excludes motorways 4 Km away, Sewerage Treatment plant 5 km away, powerlines 100’s of meters away (it would be nice if you quantified the heat lost from those powerlines and converted that into watts/M^3 of the air volume between the powerlines and the station to highlight its impact (or lack of it) on the met station site.
These are characteristics of the site and at Class 1/Class 2 this station will do a good job of measuring the local temperature.
=======================================================================
Many people will be looking forward to seeing how you have processed the TOBs bias. Particularly how your analysis compares to previous work on the subject.
Something strange going on here. The middle section is missing again.
Anthony.You seem to have an issue with text that includes less than/greater than symbols. Everything between them is being deleted. I have removed them from my comment and reposted it – see how we go.
Anthony. For some reason my earlier post had a section missing from the centre of it where I did some simple calculations in support of my contention that this a Class 1/Class 2 site. Lets try again, with the 1st half of my comment:
=======================================================================
Some quotes from Leroy et al
Class 1:
· Flat, horizontal land, surrounded by an open space, slope less than 1/3 (19°).
· Ground covered with natural and low vegetation (less than 10 cm) representative of the region.
· Measurement point situated:
o at more than 100 m from heat sources or reflective surfaces (buildings, concrete surfaces, car parks etc.)
o at more than 100 m from an expanse of water (unless significant of the region)
o away from all projected shade when the Sun is higher than 5°.
A source of heat (or expanse of water) is considered to have an impact if it occupies more than 10 % of the surface within a circular area of 100 m surrounding the screen, makes up 5% of an annulus of 10m-30m, or covers 1% of a 10 m circle.
Class 2
· Flat, horizontal land, surrounded by an open space, slope inclination less than 1/3 (19°).
· Ground covered with natural and low vegetation (less than 10 cm) representative of the region.
· Measurement point situated :
o At more than 30 m from artificial heat sources or reflective surfaces
(buildings, concrete surfaces, car parks etc.)
o At more than 30 m from an expanse of water (unless significant of the
region)
o Away from all projected shade when the Sun is higher than 7 °.
A source of heat (or expanse of water) is considered to have an impact if it occupies more than 10 % of the surface within a circular area of 30 m surrounding the screen, makes up 5% of an annulus of 5m-10m, or covers 1% of a 5 m circle.
I would put the building within the 30 metre radius. By eyeball, and comparing it to the cars in the photograph, the building apears roughly 4M * 8M Perhaps 5M * 10M so lets say 50m^s And it is a true heat source – air conditioners and all that.
A 30 M radius circle has an area of 2827 M^2. A 10M circle is 314 M^2 so the 10-30 Annulus is 2513 M^2
Ratio of these two numbers is 50/2513 = 1.99%
Allowable under Class 1 is 5%. So give that a tick.
Next the concrete block. It looks to be somewhat over 1 metre square. However the plinth is larger, maybe 2m by 2m, lets go with that. So an area of 4M^2 within the 10m radius circle is 1.27% Class 2 there but only if we use the plinth area; if we use the block area, Class 1. And It is not a heat source; ie, a generator of heat in the way the AC units on the more distant building is. If the block wasn’t there the ground beneath it would still absorb sunlight. So Class 2, Borderline Class 1
Nothing else is close enough to have an impact. The River/Mudflats are over 100 m away; beyond the boundary of what is considered significant for class 1, let alone the other classes. Note also that the Albedo figures you quote for wet soil (ie the mudflats) are quite similar to the albedo figures for low zenith angle water. Meaning that the albedo at high tide is very similar to the albedo at low tide. Thus fluctuation in tidal levels have minimal impact and constitute the basic thermodynamic backdrop for this area.
And as for all the other stuff – powerplants, motorways etc; I quote from the WMO paper
“The primary objective of this classification is to document the presence of obstacles close to the measurement site. Therefore, natural relief of the landscape may NOT be taken into account, if far away (i.e., greater than 1 km). A method to judge if the relief is representative of the surrounding area is the following: does a move of the station by 500 m change the class obtained? If the answer is no, the relief is a natural characteristic of the area and is not taken into account.”
I suggest this excludes motorways 4 Km away, Sewerage Treatment plant 5 km away, powerlines 100′s of meters away (it would be nice if you quantified the heat lost from those powerlines and converted that into watts/M^3 of the air volume between the powerlines and the station to highlight its impact (or lack of it) on the met station site.
These are characteristics of the site and at Class 1/Class 2 this station will do a good job of measuring the local temperature.
=======================================================================
Many people will be looking forward to seeing how you have processed the TOBs bias. Particularly how your analysis compares to previous work on the subject.
Thats better. I don’t know if the issue with greater than/less than is a bug or a feature but you might want to look into it.
Sometimes I get the feeling that some posts are designed to distract from other posts and swamp them with “noise”. I could be wrong though,
Living just 4 miles from the weather station and having followed and monitored weather for over 40 years, I think that some of the investigation has missed the point. A lot of work has been done to analyse the proximity to the M25, 8 lane Motorway and Littlebrook D Power Station, and the effect it may have on readings. However, Gravesend is only the warmest place in the UK when the wind is in the SE to SW quadrant. This is when the wind blows the FROM site of the weather station out across the river, so any river based warming would be felt on the Essex side. Also London is to the west and southerly winds do not come from London.
I am 4 miles to the east of Gravesend Broadness, just above the Chalk Marshes, and topography here is everything. When the wind is from the south air temps tend to be warmer than other directions to start with, but when coupled with descending air as the wind comes down from the North Downs to the river Thames, it slightly warms. Very often any cloud cover thins, or even breaks as it descends, and the resultant brightness or sunshine not experienced elsewhere in the region, can also raise temps. The same is true along the whole of the north Kent coast, and the record for 10th August 2003 was only held by Gravesend for 2 days. The new record of 38.5C being recorded by Brogdale near Faversham, 30 miles to the east. That has the same topographical set up at Gravesend with descending southerly airflows. North Kent has more sunshine than London, so that can lead to higher temperatures in Kent in warm airflows.
The situation on that day was very warm air wafted up across France, and warmed further descending into the Thames estuary. My personal reading was 39.2C but my thermometer is not certified as only for my own use.
The fact is, under the right wind conditions, this area IS the warmest in the UK, but a NE wind in winter or spring is more Siberia that anything else :(. My garden is more like the tropics (to look at) in summer, as we have one of the best summer climates in the UK.
Regards
Dave
Dave, thanks for your observations. Great to get some local knowledge. I’ll repost your comment over at my blog.
Cheers
Rog TB