From the UNIVERSITY OF MINNESOTA and the “any motorcycle or bicycle rider can tell you this” department comes this study on UHI in Minneapolis.
Results provide valuable insights into efforts to reduce heat-related harm in metro areas globally
Some parts of the Twin Cities can spike temperatures up to 9°F higher than surrounding communities thanks to the “urban heat island” effect, according to a new study from the University of Minnesota.
The study, which was funded by the Institute on the Environment and published in the Journal of Applied Meteorology and Climatology, used a network of 180 sensors deployed throughout the Twin Cities metropolitan area in residential backyards and city parks to paint the most detailed picture anywhere in the world of how temperature varies with time and place across pavement-filled metropolitan areas and surrounding communities.
Recording surface air temperatures every 15 minutes from August 2011 through August 2014 across nearly 2,000 square miles and using U.S. Geological Survey data to fine-tune differences at the neighborhood level, the study uncovered several surprises. Among them:
Temperatures in the urban core of Minneapolis, St. Paul and Bloomington average 2 °F higher in summer than in surrounding areas
The differential spiked as much as 9 °F higher during a heat wave in July 2012
Urban heat island effect is stronger at night in summer and during the day in winter
In urban areas during the winter when snow cover is less pervasive, temperatures are higher than rural areas in the daytime by an average of 2 °F.
“We’ve long known that heat radiated by buildings, roads, bridges and other structures keeps surface air temperature higher in cities than in surrounding areas. However, temperature is officially measured at just a few locations in most cities, so awareness of the extent and variability of urban heat island effects was limited,” said lead author Brian Smoliak. “Our study highlights the usefulness of dense sensor networks for urban weather and climate research with practical implications for human health, energy consumption, and environmental quality.” Smoliak began the project as a postdoctoral researcher in CFANS and is now an atmospheric scientist at the Climate Corporation in Seattle, Washington.
The more detailed understanding of urban heat islands provided by the study can help health professionals and others target efforts to protect people and infrastructure from heat-related problems, according to project co-leads Tracy Twine and Peter Snyder, associate professors in the College of Food, Agricultural and Natural Resource Sciences.
“This level of detail in real time can provide specific information to agencies tasked with protecting our citizenry during extreme heat events,” Snyder said. “It can also be used to identify persistently warm areas of the metro where green infrastructure projects could be implemented to offset some of the warming.”
###
The University of Minnesota’s Institute on the Environment seeks lasting solutions to Earth’s biggest challenges through research, partnerships and leadership development. For more information, visit environment.umn.edu.
Paper: Brian V. Smoliak et al. Dense Network Observations of the Twin Cities Canopy-Layer Urban Heat Island*, Journal of Applied Meteorology and Climatology (2015). DOI: 10.1175/JAMC-D-14-0239.1
| Abstract |
|---|
Data from a dense urban meteorological network (UMN) are analyzed, revealing the spatial heterogeneity and temporal variability of the Twin Cities (Minneapolis–St. Paul, Minnesota) canopy-layer urban heat island (UHI). Data from individual sensors represent surface air temperature (SAT) across a variety of local climate zones within a 5000-km2area and span the 3-yr period from 1 August 2011 to 1 August 2014. Irregularly spaced data are interpolated to a uniform 1 km × 1 km grid using two statistical methods: 1) kriging and 2) cokriging with impervious surface area data. The cokriged SAT field exhibits lower bias and lower RMSE than does the kriged SAT field when evaluated against an independent set of observations. Maps, time series, and statistics that are based on the cokriged field are presented to describe the spatial structure and magnitude of the Twin Cities metropolitan area (TCMA) UHI on hourly, daily, and seasonal time scales. The average diurnal variation of the TCMA UHI exhibits distinct seasonal modulation wherein the daily maximum occurs by night during summer and by day during winter. Daily variations in the UHI magnitude are linked to changes in weather patterns. Seasonal variations in the UHI magnitude are discussed in terms of land–atmosphere interactions. To the extent that they more fully resolve the spatial structure of the UHI, dense UMNs are advantageous relative to limited collections of existing urban meteorological observations. Dense UMNs are thus capable of providing valuable information for UHI monitoring and for implementing and evaluating UHI mitigation efforts.
The Turks have done a number of studies on the UHI effect on their cities.
They have the advantage that they have records from what were little more than large villages in the 1960’s which have grown to cities of a few hundred thousand on up over the last half a century as Turkey has both urbanised and industrialised.
The UHI effect found in the rapidly growing Turkish cities is in line with the American city’s based paper above.
[ Abstract selections quoted below ]
Quantification of the urban heat island under a changing climate over Anatolian Peninsula;
———–
The Anatolian Peninsula is located at the confluence of Europe, Asia, and Africa and houses 81 cities of which 79 of them have population over 100,000.
We employed some criteria to select the cities from the 81 cities.
After accomplishing all the criteria, eight cities were remaining for the study.
Nonparametric Mann–Kendall test procedure was employed for the urban and rural stations of these cities to detect the long-term change in temperature trends.
Statistical analysis of daily minimum temperatures for the period between 1965 and 2006 suggest that there is no statistically significant increase in rural areas.
In contrast to the findings of the previous studies, however, all the urban sites and difference between urban and rural pairs show significant increase in temperatures, a strong indication for the existence of urban heat island (UHI) affect over the region.
[ edit ; Climate modelling fantasy follows ]
Regional Climate Model was also utilized to assess the changes in temperature by the end of century for the region.
The findings suggest that an increase of up to 5°C is possible.
Climate change effects enforced with UHI have the potential to cause serious problems for the entire region and hence needs to be studied thoroughly.
—————-
PDF of the complete paper ;
http://cdn.intechopen.com/pdfs/40840/InTech-Quantification_of_the_urban_heat_island_under_a_changing_climate_over_anatolian_peninsula.pdf
I presented some examples under ecological changes section of my book [Climate Change: Myths & Realities, 2008] in which discussed urban heat-island effect. When I was in US I saw an article in San Jose Mercury news dated August 22, 2000 [reproduced from New York Times by Kenneth Chang]. It states that “Urbanites feel the heat when cities replace trees and greenary with buildings and blacktops”. Presented a satellite image of Summer in City [headding] — downtown Sacramento.
Surface temperature coincides the troposphere temperature near the inversion layer in night but during day time they are wide apart with upper layer showing lower temperature at urban centre which is opposite in the night.– urban to rural.
Dr. S. Jeevananda Reddy
There may be some peculiarities of Minneapolis that make the amount and patterns of UHI in that city not all that similar to other urban areas in the US, besides for the northern latitude.
Cities further south are likely to have many more buildings with air conditioning during the warmer months, and these air conditioners are pumping a lot of heat into the air in a city. This may tend to make the UHI greater in more southerly locations, where nearly every building has air conditioning.
And being in a place that is so extremely cold, i suspect that buildings and homes in Minneapolis are very well insulated. More insulated buildings will bleed less heat into the environment outside during cold periods.
So locations with less well insulated buildings may see a greater UHI in cold weather.
For new readers of WUWT:
The Urban Heat Island (UHI) is a big deal because weather stations have been encroached on by spreading cities etc. The result is that their temperature measurements have increased over time because of UHI. Where urban stations show a warming trend, rural stations do not. This means that the apparent warming trend in the continental US is an illusion caused by UHI.
Our host, Anthony Watts, has done excellent work documenting siting problems with weather stations here and here.
It seems to me that there used to be a link to the surface stations project near the top of the page. Did that get lost in a re-design? Am I imagining?
Pull down the ‘About’ tab, select’ Publications and Projects’ at the bottom of the menu.
reduce heat-related harm in metro areas globally
That(s a cracker for future alarmism and funding. Increased city deaths due to a UHI of 0.1°C as found and adjusted by UKMO
This looks like kriging done in the appropriate setting – reasonably dense data being interpolated over moderate distances without a requirement for great precision. Even better, a likely variable to correlate against in order to assess accuracy (cokriging). Not as in global temperature ‘constructions’.
A useful reminder has to hard it is the measure temperature across even relatively small area when that area has variations.
Now project that over a world wide scale , consider how ‘few’ measurements we have , and in some areas none, and now consider how you can come up with any ‘average’ temperature increase worth a scientific dam to support the claims of ‘settled science’
Experimental design 10, if you cannot measure something with accuracy you cannot know its value in a meaningful way, you can only guess it.
From the contents of test tube , to the planet , this problem remains the same .
Another motorcycle truism ….. the position of your measuring station is hugely important.
If you are riding along during a clear high pressure night, and ride down into a slight dip in the road, the temperature can decrease by 5 degrees centigrade. Literally, you ride into the dip and start to shiver, and ride back up again and feel the warmth. The difference is that pronounced.
So any measuring station down in a dip will record clear high pressure nights as being extremely cold, when they are not for most people.
R
If they did a survey in Adelaide they would find a big difference in temperature between the concrete jungle and the 700 Metre wide parkland that surround the city centre. I rode a bicycle through the parkland for years and this temperature difference was most notable on hot summer nights when I worked late. In fact Adelaide would be a great place to do a comparative study.
I ride through this area regularly and can anecdotally confirm these temp differences in Adelaide (I live on one side and work on the other so I get to experience it four times every work day and the differences are noticable)
Oh my g-gosh….it’s worser than we’s been told is!!!!! We need to find new places to live for all of the insects, rodents, birds and house pets that surely are fleeing the 9 degree F change in temp that wasn’t suppose ta happen for 85 years!
Civil unrest!!!!!!! Crime must be rampant!!!!!!!!
Heaven forfend, whatever will those poooooooooooooooooooooor Minnesotans do now that they are 2100?
My backyard weather station (~50 meters from the house at the edge of a field and ~20 meters from the pond – would have liked farther out but that was the edge of the radio’s range to my office.) runs from 1 to 8 degrees Fahrenheit cooler than the official weather station in the area (3 miles away) which is still in the countryside, but is about 15 meters from a convenience store parking lot. It doesn’t take much structure to create UHI.
“Our study highlights the usefulness of dense sensor networks ”
On the other hand, a few dozen sensors are supposedly adequate to measure the heat contents of the oceans to less than 1 hundredth of a degree.
Well the do have the ‘magic’ of smearing and models to make up for the lack of actually data , and if that fails that can always ‘adjust’ their way to the truth!
Why, its almost as accurate as a tree ring!
Hopefully they can keep up this data gathering for 30 years, so that we can see how it changes as the city grows and evolves.
“On the other hand, a few dozen sensors are supposedly adequate to measure the heat contents of the oceans to less than 1 hundredth of a degree.”
Hehe, tell that to anti-submarine forces around the world…
I have a AGW Urban Heat Island story from this morning. When I left work in Houston, TX at 6:00 AM my car outside temp was 59 F. Got home at 7:00 AM, 40 miles as the crow fly’s in the far flung suburbs, temp in my driveway was 49 F.
Add any driver of a 47 year old British roadster or any other rag top with the top down to your list of people who experience temperature differences as they drive through different local areas. (And spare me the British car jokes. I have heard them all.)
So, the average in-town temperature is about 2° F. higher than in the surrounding countryside.
Back on Sept. 18 there was a story about a study that mapped UHI for major US cities. It was based on models. It showed a range for Minneapolis between 0.52 and 0.91 ° C. (0.94 and 1.64° F). The city’s color on the Sept.18 map would go from orange to red. Not disastrously, ridiculously, wrong but still wrong.
The Sept. 18 story had some cities with negative values for UHI. It would be really nice if someone would do gridded measurements for one of those cities.
My first question is, how long will these guys be allowed to be funded?
My second question, probably out of order, is how did they ever get funded to begin with?
I got a letter asking if the sensor can stay in my yard longer. They are looking for funding to extend the data collection for another 3 to 4 years.
That’s not such a bad thing in winter. The most extreme example I remember was a calm, clear winter morning where the official low at MSP was -25. Just south of the metro, in Fairbault, it was -40.
Heat Islands are good things.
The major HVAC systems in non-residential and mass-high-density residential blasts out all sorts of thermal flux. It ain’t rocket science. Summer after sun down you’ll really see the footprint of it.
The airport is the black dot on the upper-bottom center of the map, right in the middle of the UHI.
I therefore conclude, through the authority given to me by the patron St. Gore and sayeth the unchallangeable climate dogma, that all rural stations be adjusted upward to match this station’s readings.
On a seriously cold windstill, clear night, I have seen -5F in the city and -20F at my front door.
Well, yeah, I consider UHI to be real. On the other hand, that is the wrong question. The right question is whether UHI has a significant effect on the rate of warming.
Our findings are inconclusive. Ungridded USHCN2 raw data for well sited urban stations shows even less Tmean trend than well sited non-urban stations. When you grid that data by climate region, the trend is somewhat higher for urban stations, but not to the point of statistical significance.
Microsite, on the other hand, has a large and significant effect on trend.
What is the X axis on the far right graphs? They are not labeled.
At first I didn’t understand why it’s only 2F warmer in the winter, I thought the lack of city snow (due to snow removal/salting, melt, etc) would be worth 2F and the UHI effect another 2F for a cumulative total of 4 to 5F. But due to very cold temperatures, snow and ice in Minneapolis may be more “pervasive” and tend to stick around longer than in other cities. In my opinion, cities a little further to the south would probably show much warmer winter temperatures.
Another thing, that 2013/14 winter was a doozy, extremely cold, snowy and windy, I wonder if there was much of a UHI effect during that winter. The concrete jungle was frozen solid and any UHI effect would have been blown away by the winds.