Jul 7, 2008 10:53 pm US/Central
Good Question: Where Does Humidity Come From?
(WCCO)
Here's what most of us know about humidity: it's uncomfortable and it makes our hair frizzy. Here's what most of us don't know: where does Minnesota's humidity come from?
"It's not a simple answer," said Mark Seeley, climatologist and meteorologist with the University of Minnesota's Extension Service. According to Seeley, humidity is tiny water vapor droplets in the air.
"It's in every breath of air we take. And that goes up into the atmosphere quite high," he added.
The main source of humidity for Minnesota is the Gulf of Mexico. The water is warm and moist, and flows along the Mississippi River basin north to the Twin Cities. When the southerly flow prevails, Minnesota tends to be humid. When air masses blow in from the north and Canada, the air tends to be dry.
But that's not the only source.
"We also have what we call landscape feedback. This time as we get into July, our millions and millions of acres of cropland in Minnesota is transpiring an awful lot of water," explained Seeley.
This weekend air blew from the south, right over all the flooded cities around the Mississippi River.
"All of that surface moisture is being taken up by the atmosphere and it found its way up to Minnesota. And the dew point over that period went from about 50 up to 70," said Seeley.
Seeley said there are also local sources of humidity like the larger lakes. Lake Superior and Lake Mille Lacs both provide water vapor to the atmosphere, although it's a constant level of humidity so it doesn't change from day to day.
Humidity is the "ultimate greenhouse gas" according to Seeley, as it makes it hard for the body to perspire and regulate its temperature.
(© MMIX, CBS Broadcasting Inc. All Rights Reserved.)
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