Sunday, November 6, 2011

Urban Heat Island and Recent Snowfall

On Wednesday November 2, 2011 a frontal system moving through Nebraska produced rain and eventually several hours of light snowfall in Lincoln, NE. The temperature in the city center of Lincoln, NE, remained in the mid to upper 30's and the snow melted on contact with the surface. It was several degrees cooler in the suburban areas of Lincoln, NE and the snowfall accumulated on the grassy surfaces and roofs of the houses. The slush on the suburban streets was also evidence that the street surface was cool enough to start accumulating snowfall.

The main cause of the urban heat island is the modification of the natural land surface. Urban areas have a surface of concrete, asphalt and building all of which retain their heat. The urban environment also produces “waste heat” generated by the energy usage. All of this results in urban areas frequently being warmer than the surrounding suburban areas and especially the surrounding rural area.

The two attached photos were taken minutes apart and show the difference between the city center of Lincoln and the suburban edge. With a temperature of 37 F the snowfall was melting on contact with the surface in the city but with a temperature of 33 F the snowfall was accumulating on the surface in suburban Lincoln.

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