ASTI Prototype at SGP/ARM
Atmospheric Physics at the University of Denver
Introduction
Welcome to my atmospheric research page! Atmospheric research is a very
large field. I can't begin to cover everything about atmospheric research
here. Instead, this page will (hopefully) serve as an introduction to the
research conducted at D.U. by the Department of Physics and Astronomy's
Atmospheric Research Group. This will primarilly be an overview of what we
do, and how we do it. This will, of necessity, be an on-going work which
will require a lot of my personal time and effort. Please keep this in mind,
and pardon any construction dust! Coments, complaints, suggestions and such
will, of course, be greatly appreciated!
What We Do
Most of our research is related to the chemistry of the atmosphere. While
our atmosphere is mostly made up of nitrogen and oxygen, there are an awful
lot of other compounds in our atmosphere. Although they only occur in small
amounts compared to the nitrogen and oxygen, they can have profound effects
on life here on Earth. For example ozone (which is actually a form of oxygen)
comprises a very small fraction of our atmosphere, but blocks out much of
the ultraviolet light we would otherwise receive from the sun. Exposure to
ultraviolet light is indicated in some forms of skin cancer, damage to
eyesight, and excessive amounts may damage plant life. It appears that
certain compounds such as cloroflourocarbons (CFC's) such as freon may
destroy ozone, thus reducing our protection from ultraviolet rays. I imagine
you've heard of the "ozone hole" in the news. It is believed that this
thinning of the ozone layer might be caused by use of freon compounds for
such purposes as refrigeration and manufacturing. Some types of fire
extinguishers also used similar compounds, but this use has largely been
discontinued. Carbon dioxide and
methane may trap heat from the sun, raising the average temperature of the
planet, resulting in wide-scale weather and environmental changes on Earth.
Some compounds react with the nitrogen in the atmosphere, creating nitric
acid, which results in acidic rain, which can kill plant and marine life.
Sulfer compounds can also form acid rain.
Our research is aimed at furthering our understanding of how these
compounds interact with each other, and under what conditions, what the
consequences of these interactions might be, and where these compounds come
from to start with. From this information, we may gain insight on how to
reduce or prevent damage to our ecosystem.
How We Do It
Most of our research is done using a technique called Infrared
Spectroscopy. Our primary instruments for doing this are the
Interferometer and the Grating Spectrometer. More on these
later.
Here's how it basically works:
Part of the energy that comes from our sun is infrared light. In case
you aren't familiar with the term, infrared light is light that has too
long of a wavelength for us to see. We feel it, instead, and call it
"heat". Just as visable light has a "spectrum", that is, a range of colors,
so does infrared light. Just as a specific wavelength of visible light
gives us a very precise color, so, in a way, does infrared light. What we
do is measure the wavelength and intensity of this infrared light.
Squiggly lines
The infrared radiation coming from the sun is fairly uniform with respect
to wavelength. That is, as you go out to longer and longer wavelengths,
you find that the intensity of the infrared light from the sun doesn't
change that much. However, once this radiation starts going through our
atmosphere, some of it gets absorbed by the gaseous compounds our atmosphere
is made of. This energy is stored in the bonds between molecules, and in
the orbits of the electrons of the atoms that make up those molecules.
Quantum physics shows that only certain exact amounts of energy can be stored
this way. Thus, each compound has it's own unique set of energy levels it
can store. And it can't keep them, either - just as you can't stay excited
all the time, this "excited" compound can't, either. After a while, it must
toss this energy off. These energy levels the compound stores and releases
are specific wavelengths of infrared radiation. The set of wavelengths of
infrared light the compound stores and releases also gives us a method of
identifying it - an infrared "fingerprint".
When we look at what wavelengths of light have been absorbed out of the
sunlight, we refer to it as (naturally!) absorbtion. When we look at the
radiation the compounds in the atmosphere are kicking back out, we call it
emission. To do absorbtion studies, our instruments use a solar
tracking telescope which locks onto and follows the sun, and pipes a beam
of light from the sun into the instrument. To do emission studies, we look
away from the sun.
Last modified: 20 July 1999
Created & copyright: 23 July 1997 by Kevin G. Murcray.
All rights reserved.