Mixed Vegetation May Help Cool Climate
FORT COLLINS, Colorado, June 28, 2002 (ENS) - The mixture of crops planted in the Great Plains and Rocky Mountain states has helped keep their climate cooler and wetter than it would otherwise be, a new study suggests.
Hydrometeorologists Jim Shuttleworth at the University of Arizona in Tucson, and Lixin Lu at Colorado State University in Fort Collins, 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.
Mixed vegetation impacts the atmosphere, weather and climate by changing the amount of sunlight that reflects from land and leaves back out to space, and varying the heights of trees and other plants exposed to the wind. Different plant types also evaporate water at different rates.
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.
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.
"The mixed vegetation creates areas of different temperatures next to each other, some warmer and some colder, and this leads to mixing in the atmosphere that gives rise to clouds and, ultimately, rain," Shuttleworth said.
Over the last two decades, detailed maps of the amount and type of vegetation that covers the ground have become available through remote sensing. Based on that information, scientists can enter data to describe vegetation into computer models that simulate regional climate.
In this study, a climate version of the Regional Atmospheric Modeling System (ClimRAMS) was used to explore whether more of a mix of vegetation can alter climate in the United States. A U.S. Department of Agriculture soil database was used to define different soil types in the climate model, and vegetation was classified using an international land cover system.
The ClimRAMS assumes there is little difference between grasslands in northern Wyoming and southern Kansas, for instance, but the researchers found that when they introduced satellite measurements of leaf area index - a way of quantifying how much vegetation is present - the more realistic pattern of vegetation generated extra convection in the atmosphere to give a cooler, wetter climate.
Most current computer models that predict Earth's future climate do not account for the complex mix of vegetation and its atmospheric impacts, and may be producing forecasts that are too dry and too warm during growing seasons.
"In the future, it will be important to use remote sensing data to enter the fine details of plant cover into computer models to get more accurate weather and climate forecasts," Shuttleworth said.
More research is needed to determine if increasing variety of croplands would help reduce drought conditions. The study appears in the June issue of the "Journal of Hydrometeorology."
Environmental News Service
http://ens-news.com/
Mixed Vegetation May Help Cool Climate
Moderator: Super Moderators