Why do we measure heat at airports and in greenhouses?
Posted by FewAnybody2739@reddit | AskUK | View on Reddit | 47 comments
Apparently Kew Gardens and Heathrow are setting temperature records, and this is reported as if it's representative of the wider country for some reason. I would expect a place famous for greenhouses to be very hot, and it's only really indicative of cloud cover. Similarly an airport covered in tarmac with loads of planes burning tons of jet fuel is also going to be very hot.
Surely it would be better to pick several more typical places around the UK and average them? If you want landmarks then go for the town hall, should be easy to get a measurement there.
JuanitaMerkin@reddit
They aren’t measuring from inside the greenhouse.
That there is some tarmac on the ground in Heathrow likely makes little to no difference on the temperature in the exposed air.
FewAnybody2739@reddit (OP)
When it's sunny I can feel the extra heat radiating out of tarmac.
JuanitaMerkin@reddit
it’s not “extra” heat
ResponsibilityOk4298@reddit
It’s an odd hill to die on here. Air temps above tarmac are higher than the air temps above grass in the same conditions. This isn’t debatable, it’s a fact.
Alamata626@reddit
Weather stations at airports aren't situated above tarmac. They're normally found in the safety areas surrounding the runways.
Which-World-6533@reddit
Yes, this is a well known effect.
Heathrow is usually hotter than than surrounding city. London itself benefits from the heat-island effect which means it's warmer than the surrounding country.
Sad_Interaction_2933@reddit
Benefits is a slightly contentious choice of word at times like this though :-D
Sad_Interaction_2933@reddit
Yes air is mostly heated up by conduction from the warm ground that the sun has heated up (through radiation). The local air will certainly be warmer above hot surfaces like tarmac
ResponsibilityOk4298@reddit
Tarmac gets extremely hot (relatively) and retains heat too. Concrete is not so bad but also heats up and retains heat. So tarmac does heat up the “exposed air” around it as it can be significantly warmer than the air as that is how thermal dynamics works.
In another country that gets very hot (50C), a friend went on holiday and left his aircon off. Upon return, it took 3 days to get the house cool again as the walls radiated heat as the aircon hadn’t been keeping them cool.
TLDR: yes, tarmac heated by the sun then heats the air around it.
Far_Palpitation_6133@reddit
Tarmac does heat the air around it. Meteorological stations at airports have an international standard for their distance away from tarmac for this said reason.
Timely_Egg_6827@reddit
Generally because they have a reason to be measuring heat anyway. Kew needs to know for plants' sake. Airports monitor a lot of weather elements so temperature just one. So cheap for media to piggyback on them.
Met does have a lot of measuring stations across country.
OrangeTractorMan@reddit
I've seen people denying the changing climate with "but they're at airports!"
I mean, some are yeah but.. they've been there for bloody decades lol. Historically, Airports have needed the most accurate readings and have always had these sensors.
Systems at airports are showing the same pattern, people seem to think they have a gotcha.
Evening-Tomatillo-47@reddit
Tell them to listen to the shipping forecast then, there are some in the sea
CrazyCake69@reddit
Shipping forecast can be very therapeutic. Do i understand what most of it means nope but does a good job at putting you to sleep.
ARobertNotABob@reddit
Low, Rockall Hebredes, Malin, 987, deepening rapidly, expected Fair Isle 964 by 0700 tomorrow, Force 6, easing Force 5, rain, possible sleet later, visibilty 2 miles.
...and he's gone, bless him.
Timely_Egg_6827@reddit
Also Met take time to report - mutiple locations and error checking. A single point of data much easier tor report on.
GlitchingGecko@reddit
They've already got the technology for other reasons, so they're the most accurate.
My outside thermometer is currently saying 39.2c, which is probably not that accurate, unless it's significant hotter in the Midlands than in London.
LilacScentedStoat@reddit
If it's in the sunshine, it will be much hotter than the temps Met office etc report. I believe, but could be wrong, that the gauges they use are in special boxes so are shaded and measure air temperatures not direct sunlight.iyswim
GlitchingGecko@reddit
It's under the awning of the garage and in 100% shade all the time.
It's not in anything protective though, it's just stuck to the fascia with M3 tape.
Beartato4772@reddit
Yeah what you're measuring there is the temperature of the fascia.
GlitchingGecko@reddit
I've got an old fashioned mercury one on the fence next to it (also in complete shade) and it's reading the same, so 🤷🏻♂️
Physical-Bear2156@reddit
Airports have nice expensive and calibrated met stations. The larger ones probably publish the data online in real time.
It wouldn't surprise me to find Kew has a nice set up too.
HauntingCicada2630@reddit
O Jesus, they really don't teach anything in schools these days!
WDW1997@reddit
That's a bit like me asking why we're recording the temperature in the centre of London when I'd expect it to be hotter there than in the Cairngorm mountains.
We have known hot spots, and known cold spots. Death Valley still records temperatures even though it's just the middle of a desert
srogijogi@reddit
The temperature is being measured in various places. It's media who pick all the time the same sources of measurement.
WeezyNetwork@reddit
And the temperature record is as recorded at that location, in the shade
Which I only just learnt today.
BarNo3385@reddit
Its a real problem with the temperature data series. The original measurement points were selected to be a representative mix of urban, suburban and rural locations.
But that was a long time ago (I forget whether it was mid 20th century or all the way back to the 1800s). In the meantime the geography of the country has changed, in particular some rural areas are now urban.
You can probably somewhat account for it statistically, but you still get a confounding effect that urban areas tend to be warmer for a variety of heat island effects, so, is increasing urbanisation showing up as higher temperatures?
Routine_Ad1823@reddit
Because that's where the weather forecasters are employed.
EUskeptik@reddit
These weather stations are scientifically rigorous, built, maintained and calibrated to a high standard and are representative of wide areas, not just their immediate surroundings.
Why are you questioning these locations? What is your agenda here? Climate denial?
-##-
Ok-Constant-2683@reddit
Do you think they are measuring temperature inside the greenhouse?
limach1@reddit
i don’t think they’re measuring the weather from inside the greenhouse
Street-Persimmon8492@reddit
They are the places with the best technology to measure most likely
Mendel247@reddit
This is it. Kew is a scientific institute, and airports invest heavily in meteorological equipment
Substantial-Sell8913@reddit
I mean, a record breaking temperature at Heathrow is still a record...
DukeSunday@reddit
I mean it is representative. These spots don't randomly shoot up to records while the rest of country trundles along at 15 degrees.
As part of their news articles about "wow, it's really hot today" they mention that there's been a new record set and where it was set, because it's vaguely interesting and fills out the article. We measure the record wherever the record happens to have been set, and shocker; it's usually set in these kind of places.
It is probably also true that Oxford and Bristol and Leeds and wherever else are also hotter than they have previously been in May, but in a national article you're not going to mention every single one of those places.
FaxOnFaxOff@reddit
Temperature for weather monitoring is measured in a Stevenson Screen which is 1 m above the ground and away from buildings. Not everywhere has one so that limits where you can measure and quote. Evidently Kew and Heathrow have one each. Kew's is not within a greenhouse - they of course measure the temperature of their greenhouses but that's not what's being quoted.
I agree that a large expanse of tarmac is going to affect things, much like London is a thermal island but that doesn't mean it's not the actual temperature in the shade. They aren't measuring the exhaust gases of a 747 or placing the Stevenson Screen in the middle of Runway A.
champair79@reddit
Remember this is the temperature in the shade. The Heathrow weather station is surrounded by grass as well so using tarmac and emissions doesn't really affect the data. It's just the hottest part of the country in general hence why Heathrow and Kew are often in the headlines.
Impossible-Tip9707@reddit
Wherever they measure it I think we can all agree it is abnormally hot
GlitchingGecko@reddit
Especially for MAY. This was the 'heatwave' temperature last year in July.
We're gonna break the 40.3c record if we have another July heatwave this year.
Impossible-Tip9707@reddit
It's truly terrifying but yeh, let's focus on exactly where the temperature gauge is as the problem 🫠
mckjerral@reddit
They're not measuring IN the greenhouses, and actually being around trees significantly reduces the ambient temperature, so Kew while being accurate and standardised (in that it has a history of recordings), is probably underreporting for the locality.
ChickenPijja@reddit
These are where the records are set is because these places need accurate weather forecasts for their day jobs. It doesn’t really matter what the temperature of centre of a city is, it’ll function whether it’s 10c and 50mph winds, or 30c and no wind. For airports that makes a huge difference, and Kew Gardens will be the same sort of thing.
Now whether those locations are a fair reflection on the country, being surrounded by greenhouses or tarmac will increase the temperature near them.
Dissidant@reddit
By the amount of pressure required to use a spatula to peel parts of yourself from other parts of yourself 😀
jumpy_finale@reddit
The other key reason for reporting purposes is that major airports and scientific sites like botanic gardens will have long established weather records available.
Beautiful_Path_3519@reddit
Why do they always seem to build airports in the places with the most extreme weather?
the_gwyd@reddit
These are places that care about the weather, so they already have weather stations installed. They may be setting records, but they're not new weather stations, they've each had them for decades, so they are beating like-for-like records. We do record weather data at plenty of other weather stations but they just don't beat the records. London as a whole will have a bit of a "heat dome" effect due to the general pollution and heat generated by such a hub of human activity.
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