Mixed Croplands May Make Some Areas Cooler, Wetter in Summer

The variety of the vegetation and crops in the Great Plains and Rocky Mountain states has helped maintain a cooler, wetter climate, according to a NASA-funded study using a computer climate model.

Hydrometeorologists Jim Shuttleworth at the University of Arizona, Tucson, Ariz., and Lixin Lu at Colorado State University, Fort Collins, Colo., found that when they introduced satellite measurements of the real patterns of vegetation in Great Plains and Rocky Mountain states into a computer model, the results generated extra convection in the atmosphere to give a cooler, wetter climate.

The study appears in the June issue of the Journal of Hydrometeorology.

Mixed vegetation impacts the atmosphere, weather and climate through the proportion of sunlight that gets reflected from the land and leaves back out to space, the varying heights of trees and other plants exposed to the wind, and the effectiveness of different plant types when it comes to evaporating water.

For example, irrigated, lush crop lands with plenty of water in the soil, warm the air less because they use more of the sun's energy for evaporation, as compared to hot, dry bare soil. Along with differing temperatures, the varied heights of plants and trees in a region change the aerodynamics of the atmosphere, creating more circulation and rising air. When the rising air reaches the dewpoint in the cooler, upper atmosphere, it condenses into water droplets and forms clouds.

For the completer article, go to: http://www.gsfc.nasa.gov/topstory/20020618mixed_veg.html