While NCDC’s Dr. Thomas Peterson tries to ignore UHI, from Hans Von Storch at Die Klimazwiebel (h/t to Jos de Laat) we learn that many other people are actively measuring it. WUWT reader may remember my “do it yourself UHI kit” for vehicles…now there’s one for a bike:
Studying urban heat island effect on a bike
It is long known that in cities there may be a significant climatic effect due to urbanization – thus in cities we have the interesting and challenging task of determining at least three significant drivers for change, if not more, namely the effect of the local modification of the environment as well as the local manifestation of global change due to greenhouse gases (plus, possibly other global factors). Unfortunately, systematic studies about the determination and separation of these effects – in principle a detection and attribution task – have not been done often. At least, I am not aware of such efforts; indeed even studies only on the size and distribution of the urban heat island effect (UHI) are not done often; in Hamburg, a first study was only published in the last few years – before that one could hear that in a maritime climatic environment as Hamburg, the effect would be negligible. It is not.
Now, an innovative study is about to be published – see the manuscript here: Measurement and statistical modeling of the urban heat island of the city of Utrecht (the Netherlands) by Theo Brandsm and Dirk Wolters from KNMI. The trick was, to do the year long observations by bike, as described in this abstract:
Mobile temperature and humidity measurements have been performed along a 14 km transect through the city of Utrecht (311,000 inhabitants) in the period March 2006 – January 2009. The measurements took place on a bicycle during commuter tra c and resulted in 106 nighttime profiles (before sunrise) and 77 daytime (afternoon) profiles. It is shown how the intensity of the urban heat island depends on wind direction, cloudiness and wind speed. Statistical models are constructed that relate the mean and maximum nighttime urban heat island intensity profiles to area-averaged sky-view factors and land use combined at both the micro and local scale. Sky-view factors are estimated from a 0:5 x 0:5 m surface elevation database and land use is obtained from a 25 x 25 m land use database. The models are calibrated using the mobile measurements and provide estimates of the spatial distribution of the mean and maximum nighttime urban heat island intensity in Utrecht. Both models explain more than 75% of the variance. A separate non-linear model is introduced that relates the temperature differences between the warmest and coolest part of the transects to wind speed and cloudiness.
The paper:
Brandsma, T. and D. Wolters, Measurement and statistical modeling of
the urban heat island of the city of Utrecht (the Netherlands)
Journal of Applied Meteorology and Climatology, 2012, 51, 1046-1060.
available here:
http://www.knmi.nl/publications/fulltexts/uhi_manuscript_brandsmawolters.pdf
I put a couple of the figures side by side to give you an idea of what was discovered:
I used to be in the asphalt business and within that industry is COMMON KNOWLEDGE that asphalt road surface temperatures can COMMONLY be 20F to 30F HIGHER than ambient air temperatures, even on cloudy days. On hot sunny days, the asphalt can easily attain temperatures greater than 30F warmer than ambient.
It is no secret that asphalt is a very good “storer” of heat as is, of course, roofing tar.
Of course, concrete and steel exhibit similar properties, though to a lesser extent.
It may be that it had not attracted my attention previously, but I have noticed of late that the MET Office in the UK in the guise of their TV weathermen now often openly talk about overnight rural temperatures being 3 or 4 degrees or even 5 degrees C cooler than overnight urban temperatures. Is this perhaps because they can now get away with the statement without it being tied to UHI measurement bias because they are the authority and they have the media tied around their little fingers, or are they just p**d off with their alarmist superiors in the Climate department?
What Hans is saying suggests to me that studies on the powerful effects of UHI have not been done because what they learn might dilute the impact of the CAGW narrative.
Biking in Holland, who would have ever thunk it?
I stumbled on this at Weather.com today:
http://www.weather.com/news/record-warm-year-us-september-20121009
The UHI effect continues to be exploited fully by the governmental institutions depending on congressional funding.
Well, we do need to “pedal” the UHI Effect whenever possible.
🙂
Research is confirming what common sense clearly suggests.
The good thing is it’s telling us that in an average Northern European urban environment the effect is responsible for up to 2°C.
How much will it be in Phoenix AZ or LA or Dallas TX, and how much under airport conditions?
Probably the most underestimated factor in measuring temperatures.
So AGW has always been an engineering issue (how to measure temperatures) and activist-scientist have been jumping on wrong data to promote their cause. For more than 2 decades now.
What a desaster.
Anthony, surfacestations.org has been right on the money, from the beginning.
That is a massive amount of work over a long period to come up with something that substantiates common sense. If I put ten 100 watt light bulbs in my living room, turn them all on, it will soon become the warmest room in the house; my own self-made UHI. Now all we need to do is apply the model to all the UHI temps as an adjustment. Raw compared to the model.
Is climateaudit.org down for anyone else?
The main cause of the daytime UHI is restriction of convection. Because convection and radiation are coupled, the local temperature increases to maintain, at equilibrium, constant convection + radiation. Try it on the beach with a wind break to demonstrate the principle to yourself. This experiment also proves the earth cannot emit IR as if it were a black body because otherwise the temperature would not rise to generate the extra radiative heat loss!
A secondary cause is there is less evapo-transpiration so less of the convection is via the generation of latent heat in the atmosphere by increasing its humidity. The third reason is that the heat capacity of dense structural materials is higher than less dense soil, so there is more sensible heat storage.
It would be interesting to attach one of the do it yourself devices or use existing temperature data from the airlines data recorders to map temperatures in and around UHIs as well as any other long term data on temperature trends globally. Who needs a balloon, when we already have thousands of air-penetrating devices zooming about the heavens.
Fantastic !!!
I don’t know about the accuracy of their model but can tell you that on a motorcycle the changes in temperature are very apparent when riding in the city or in rural areas, for that matter, and are significant. Lower elevations in rural areas, in particular, collect cold air and in Phoenix, in particular, when one enters irrigated highly built areas the humidity amplifies the heat SUBSTANTIALLY when riding through in 100+ F temps. Concrete and asphalt pavement, roof tops, AC exhaust, overhead haze from sewer exhaust on every roof (methane), etc.
Elimination of significant portions of the human population would go a long way to mitigating what little insignificant portion of heating is man made on this planet, though it would do nothing to alter whatever direction the historical, continuous climate change is taking. And warm is better than cold, in any event.
Just look at this as a UHI example!;
http://ceo.decc.gov.uk/nationalheatmap/
Click on ‘layers’ – ‘total heat’
Next question: Where on this view are the stations whose temperatures are used by GISS, etc?
UHI? Oh I remember, that’s the thing that the UK Wet Office said doesn’t exist, doesn’t affect their temperature records, it does exist but it’s been allowed for, oh & it’s going to kill us all by 2100AD because of Global Warming! Dr Vicky Pope rocks, doesn’t she just! Curiously, she & Dr Julia Slingo seem to have been particularly quiet of late, something’s afoot me thinks!
I have long noticed that the trees in the city and suburbs turn color later in the fall than do trees out in the country, because of the nearby streets and buildings holding in the warmth of the day overnight.
Jim G says:
October 10, 2012 at 9:23 am
“Elimination of significant portions of the human population would go a long way to mitigating what little insignificant portion of heating is man made on this planet”
Don’t worry Jim that is the game plan that the cultists plan on following.
Charlie H says:
October 10, 2012 at 9:00 am
“Is climateaudit.org down for anyone else?”
OK at 7:45 and 9:50 PDT.
Jim G says:
October 10, 2012 at 9:23 am
“I don’t know about the accuracy of their model but can tell you that on a motorcycle the changes in temperature are very apparent when riding in the city or in rural areas, for that matter, and are significant.”
I’ve noticed the same thing here in Ohio, there’s even a big difference in sunny areas vs areas where the sun is blocked.
But I’ve also got thermometers at the house, the one that’s blocked from the wind, but in direct sun over brick can easily get over 120F on warm sunny days. And while it drops quickly when the sun goes away (and sets), the bricks are still warmer than air temps after cooling all night.
What I don’t understand is how scientist who say there’s no apparent UHIE come to that conclusion, do they never go out after dark, never leave/visit a city? It boggles my mind.
Colin Porter says:
October 10, 2012 at 8:37 am
It may be that it had not attracted my attention previously, but I have noticed of late that the MET Office in the UK in the guise of their TV weathermen now often openly talk about overnight rural temperatures being 3 or 4 degrees or even 5 degrees C cooler than overnight urban temperatures. Is this perhaps because they can now get away with the statement without it being tied to UHI measurement bias because they are the authority and they have the media tied around their little fingers, or are they just p**d off with their alarmist superiors in the Climate department?
__________________
The most likely reason that you’ve only just noticed it is that it’s most pronounced when rural areas experience a frost but urban areas stay above freezing. During summer the differences don’t get commented on.
Other minor problem of urban settlements is they are often in uncharacteristically warm spots anyway (at least in temperate areas). If you look at the siting of any old (pre-1000) church site in Scotland, it is likely to be notable warmer than surrounding areas. I suspect the same is true for successful early North American settlements.
So in those areas which get cold, it may be the least cold places are where people built important settlements, which are often still the largest settlements…
The problem with discerning UHI in the temperature record is that it has built up slowly, over decades, as the cities grew. If each city had instantly appeared over night, the UHI for that city would be obvious in the temperature record and near impossible to argue about.
Which brings up an interesting question.
It is my understanding that China is building entire cities from scratch, often evicting families from multi-generation farms to do so. Any chance that they are making before and after temperature records?
I hate to rain on the parade, but if UHI now is no worse than it was 20 years ago, then the temperature trend has not been affected. I suspect that since major urban centers continue to be survivable that UHI is a limited phenomenon, detectable while a city is growing from a cow pasture, but insignificant past a certain level of development. So only cities smaller than a certain size will experience a temperature trend affected by UHI. The New York Central Park temperature record supports this.
http://icecap.us/index.php/go/new-and-cool/central_park_temperatures_still_a_mystery/
@pochas,
UHI affect on trend is dependent on population growth in the urban centers. You are correct that if a city isn’t growing, it won’t affect the trend.
However, the measured trend is < 1 degree C over the last century.
How many US Cities have experienced no poplulation growth over the last 100 years?
The correct answer is 0.
How many cities world wide have experienced no growth in population in the last 100 years?
The aswer is very likely still 0.