1995-11					RELEASE:  May 30, 1995

Contact:  Joan Vandiver Frisch
NCAR Media Relations
(303) 497-8607; Fax 303-497-8610
E-mail:  jfrisch@ucar.edu


ATMOSPHERIC PHYSICS ENTERING THE 21ST CENTURY

BOULDER--As atmospheric physicists stand at the door to 
the next century, what do they see?  William Cooper, a 
scientist at the National Center for Atmospheric Research 
in Boulder, Colorado, will give a preview on Tuesday, May 
30, at the American Geophysical Union's spring meeting in 
Baltimore.  

Whether predicting climate change over the next century, 
forecasting the week's weather, or warning an airplane of 
icing ahead, atmospheric scientists are eager to improve 
their computer models.  To do so, they first must solve 
key problems of atmospheric physics.

"Even when the underlying physics is clear," explains 
Cooper, "it's the complex interaction between these key 
problem areas that will make predictions difficult and 
create the greatest challenges in the years ahead."  
Following is his list of the main problems facing 
atmospheric physicists in the coming years.


Key Problem Areas

-- Radiation:  As scientists study to what extent solar 
energy is reflected off or absorbed by water, chemicals, 
dust, and other components in the earth's atmosphere, 
they are still finding surprises.  A particular goal of 
current research is to find ways of representing in 
computer models the effects of clouds and aerosols on the 
earth's radiation budget.

-- Clouds:  Cloud physicists are trying to understand how 
ice forms in the atmosphere and to determine what factors 
control the coverage and radiative properties of clouds.  

-- Electricity:   Recent research has shown that 
collisions involving ice particles in thunderstorms are 
responsible for the electrical charge separation that 
leads to lightning and to the global electrical circuit.  
However, the details of the charge transfer are still not 
understood.  New observations have shown that there are 
other discharges, in addition to the familiar lightning 
events, that occur high above thunderstorm tops.  The 
nature of these newly discovered discharges is still a 
mystery.

-- Boundary-layer meteorology:  The low clouds that cover 
large portions of the midlatitude oceans reflect solar 
radiation and cool the earth, but scientists cannot yet 
predict the factors responsible for their maintenance or 
dissipation.  Scientists are also actively working to 
represent accurately how heat, water, and trace gases are 
exchanged at the surface of the earth.

-- Small-scale dynamics:   Two particular problems are to 
represent in computer models the collective effects of 
cumulus clouds on global air motions and to better 
predict hurricane formation.


Where to Go from Here

--  Scientists must develop a way to predict the 
influences of small-scale processes on large-scale 
phenomena.  Currently, computer models of the earth's 
weather and climate do not show the collective effects of 
processes that occur on a scale smaller than that 
represented in the modelÑfor example, how certain air 
motions dissipate layers of stratocumulus cloud or how 
gravity waves affect atmospheric circulation patterns.

--  Water is the most important greenhouse gas and a 
driving force behind weather.  Yet scientists are 
currently unable to describe mathematically the processes 
determining the distribution of water in the atmosphere.  
This obstacle affects all disciplines in atmospheric 
scienceÑand many beyond.  A high priority for the future 
is to develop such a description of the water cycle.

--  Instruments must be developed that can make the 
accurate, comprehensive measurements required for 
scientific efficiency.  In many areas of atmospheric 
research, technology has not kept pace with research 
needs.  Scientists studying atmospheric radiation are 
hampered by the lack of definitive measurements that 
could test current theories.  Instruments to measure and 
classify particles and to determine their composition or 
their potential activity in clouds have not been 
developed or are not suited for use on research aircraft.

NCAR is sponsored by the National Science Foundation and 
managed by the University Corporation for Atmospheric 
Research.

-The End-

Writer:  David Hosansky
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