David E. Steitz
Headquarters, Washington, DC                       May 14, 1997
(Phone:  202/358-1730)

Dave Drachlis
Marshall Space Flight Center, Huntsville, AL
(Phone:  205/544-0034)


RELEASE:  97-96

NASA STUDYING HOW TO USE MOTHER NATURE'S 
AIR CONDITIONERS TO KEEP OUR CITIES COOL 

     Using space-age technology, NASA researchers are studying 
how "urban forests" may allow cities to continuously grow while 
maintaining air quality and the environment, as well as lower 
cooling costs during sweltering summer months.

     Collaborating with ten Atlanta schools, the Atlanta 
Regional Commission and the Environmental Protection Agency, 
two NASA researchers from the Global Hydrology and Climate 
Center at the Marshall Space Flight Center, Huntsville, AL, 
began a study in Atlanta this week to learn how rapid 
urbanization affects temperature and air quality, and what can 
be done to lessen the impact.

     The researchers, Dr. Jeff Luvall and Dr. Dale Quattrochi, 
are studying bubble-like accumulations of hot air, called urban 
heat islands, that have developed as Atlanta has grown during 
the past 20 years.  "Urban heat islands result when naturally 
vegetated surfaces are replaced with asphalt, concrete, 
rooftops and other man-made materials," said Quattrochi.

     According to Quattrochi, the temperatures of artificial 
surfaces can be 20- 40 degrees higher than those of vegetated 
surfaces.  "Materials, such as asphalt, store much of the Sun's 
energy and remain hot long after sunset," said Quattrochi.  
"This produces a dome over the city of temperatures 5-10 
degrees higher than air temperatures over adjacent rural 
areas."

     "The more a city grows -- replacing trees and grass with 
buildings and roads -- the warmer it becomes, increasing peak 
power demands.  To meet these demands, power plants must 
utilize fossil fuels to a greater extent, which ultimately have 
a negative impact on air quality," said Luvall.  In findings 
from similar studies, the two researchers found that city parks 
and other urban areas with trees and grass were cooler than 
parking lots and areas with a high concentration of buildings.  
"These 'green areas' are cooler because they dissipate solar 
energy by absorbing surrounding heat and using it to evaporate 
water from leaves, thereby cooling the air," said Luvall.  
Urban forests also help cool cities by shading surfaces like 
asphalt, roofs and concrete parking lots, preventing the 
initial heating and storage of heat.  

     To determine where Atlanta's hot spots are, a Lear Jet 
equipped with thermal imaging equipment flew over the 
metropolitan area on May 11 and 12 taking heat images at mid-
day -- the period of maximum heating -- and again 12 hours 
later when surfaces began to cool.

     On the ground, some Atlanta elementary students took part 
in the experiment by taking temperature and moisture readings 
of different surfaces at their schools in conjunction with the 
mid-day flight.  The students will compare and verify their 
measurements with those recorded by instruments on the jet. 

     Information collected from the air study will allow 
researchers to understand the effect of tree cover -- or lack 
thereof -- on Atlanta's temperature and air quality.  These 
findings also will provide Atlanta's urban planners a 
foundation to determine the benefits of developing and 
maintaining urban forests.  Additional benefits may come from 
building plans that incorporate trees to shade roofs and reduce 
the heat load on houses and buildings, thus reducing power 
requirements.

                         -end-