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?

Maybe the Met office should add air conditioners to the list? The brick building and sidewalk leading up to the station make nice heat sinks don’t you think?

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: August 18, 2012 at 12:30 pm 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 3

Just 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: August 17, 2012 at 7:00 pm 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: August 17, 2012 at 8:46 pm 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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