Simply Science: Our urban heat island

SAINT PAUL, Minn. - Although not the tropical picture that immediately comes to mind... the cities of Minneapolis and Saint Paul are on an island.

"The Twin Cities metro area has a strong urban heat island," declares University of Minnesota Professor, Dr. Tracy Twine.

What that means is that the urban concrete of Minneapolis and Saint Paul makes for warmer days and nights for city dwellers.

She further says, "This is observed mostly at night, so the urban areas will tend to stay warmer overnight, and they also tend to stay warmer during winter."

Because the building materials within the urban core absorb more of the sun's radiation and hold on to that heat longer, a downtown temperature can differ by more than 10 degrees when compared with rural areas. Two University of Minnesota professors are studying that premise in a project called "Islands in the Sun"

Peter Snyder, the second researcher on the project, says, "Over a monthly average, downtown will betwo tothree degrees warmer than say Hugo or the northeast suburbs."

Urban Heat Island research in the past has focused on southern cities like Atlanta and Los Angeles.

But because the Twin Cities receives snow in the winter, this project is unique.

Summer heat islands are associated with negative consequences like hyperthermia and poor air quality, but winter heat islands can make bitter cold days more bearable.

Snyder adds, "It's very important that we design cities and maintain cities so that it's a healthy environment for the citizens."

Two sensors atop the Science Museum of Minnesota are gauging the difference between a white and a black rooftop.

Over the next four to five years, the study will look at how building materials, landscaping and proximity to water affect the strength of our landlocked, Midwestern island.

Students working on the project gather the temperature data from volunteers across the metro, who choose to host a temperature sensor on their properties. Some volunteers in select areas are still needed.


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