Living in an Urban Heat Island

June 22, 2005 at 2:49 am | Posted in Uncategorized | Leave a comment

The last few days, our weather has really been quite pleasant, considering that it is now officially summer. The humidity has dropped into the 3o% range each afternoon. And that makes temperatures in the low 90’s a lot easier to deal with. With low humidity, perspiration on the human body evaporates quickly. And since evaporation is a cooling process, that cools the skin, which makes the heat much easier to take than when we have high humidity.

And those same low humidities mean that the air cools off more readily after the sun goes down. But not everyone gets the same amount of cooling. Early Tuesday morning, for instance, the official low at DFW was 71. And it was also 71 at Love Field. But in the surrounding countryside, it was much cooler. The temperature dropped to 61 in Mineral Wells and McKinney. And believe it or not, Bridgeport reported a low of 55! That would have been cool enough for a record low if it had occurred at DFW.

So why is there such a discrepancy in morning temperatures? It all comes down to the greater population and greater development of buildings and pavement that we have here in the Metroplex. This is what we call the Urban Heat Island effect. Every night, temperatures are typically warmer in the Metroplex than in the surrounding rural countryside. But that effect is especially noticeable when we have low humidity, as we do this week. If you want to learn more about what causes Urban Heat Islands, check out the following web site:
http://cimss.ssec.wisc.edu/wxwise/heatisl.html

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