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Dave Thurlow, Host

 
Suburban sprawl has caused many problems - the loss of wildlife habitat, increased air pollution and traffic congestion - to name just a few. Now you can add changes in the weather to that list. Hi, I'm Dave Thurlow and this is The Weather Notebook.

Colorado

Over the past few decades in the cities of Boulder and Denver, watering lawns and irrigating farmland has changed the regions weather. Researchers at Colorado State University and the U.S. Geological Survey have noticed a cooling trend. On average, they say, the temperature drops about three and a half degrees a decade. Supporting their study, the researchers have measured a sixteen-degree difference between an undeveloped shortgrass prairie and an irrigated suburban landscape.

The reason for the temperature drop is simple. Putting more water on the land also adds a lot of moisture to the normally dry landscape, as that moisture evaporates it cools the air. And the local ecosystem is responding. Five kinds of trees, which thrive in the cooler, wetter high altitudes have been slowly migrating down the mountainside to locations that had been dry for thousands of years.

The extra moisture also acts as fuel for thunderstorms. Although the cooler temperatures make it harder for storms to develop, when they do form the added moisture means the thunderstorms pack a more powerful punch.

The scientists worry that increasingly unsettled weather could impact recreation and tourism in nearby Rocky Mountain National Park. They also fear that the cooler temperatures and increased moisture will lead to a build up of grasses and other vegetation which could fuel forest fires making matters even worse.

Thanks today to Weather Notebook contributing writer George Homsy. Our show is a production of the Mount Washington Observatory, funding is provided by Subaru, the beauty of all wheel drive and by the National Science Foundation.