Remote Sounding

This is literally the measurement of something from afar.  Since you are reading this text and you are not in contact with the paper or the monitor screen, you are performing a measurement by remote sounding.

For the atmosphere we must measure things remotely because of the large size and the difficulty of getting a large enough number of measurements to be useful.  Thus we measure from the ground throughout the atmospheric column, from balloons across large horizontal distances, and look down from satellites at the atmosphere below. The key to all these measurements is the reflection, absorption, scattering and transmission of various wavelengths and the changes induced by the constituents of the atmosphere.  In effect we look for the “fingerprint” of specific compounds.

The reason for the interest in these compounds in the atmosphere, even though they are present in parts per billion, is that most of the chemical and radiative properties of the atmosphere are determined by these “minor constituents” rather than the major constituents, oxygen and nitrogen with act as “inert filler” to make up the atmospheric bulk.

These minor constituents influence the atmosphere in many ways, we concentrate on three issues.



I don’t need to re-iterate the concern over ozone depletion, increase in UV-flux and skin cancer.  However the atmosphere is a complex place and even though there is a treaty in place to limit the release of Chlorofluorocarbons (CFCs) we need to continue to work on our understanding of ozone and related chemicals in order to ensure first, that the controls that we have put in place are working and second that nothing else is going on (such as the increase in greenhouse gases) to interfere with the good work.

However there is a second aspect to ozone: whereas stratospheric ozone is good—we need more (or at least no less) in the 25-25km altitude range—we need less of it at ground level because it is a major pollutant and contributor to the complex chemistry of smog.  So, stratospheric ozone is good and tropospheric ozone is bad!

Measuring ozone and other chemicals in the troposphere is fairly easy if you want to sample locally but becomes a real challenge if you want to do it remotely, say from a satellite, to get a global view.  That is why we have instrumentation such as that carried on the SCISAT and MANTRA missions. Ozone also reacts with other chemicals in the troposphere and so we need to measure those as well and that is the objective of the MOPITT mission

Air Quality

Thinking about ozone in the lower atmosphere leads us to consider issues of air quality.  Whenever anyone asks me whether this is important I just ask them to take a couple of breaths and then answer their own question—of course we worry about the quality of the air we breathe.  With 6.5 billion humans on the planet consuming nearly 100 million barrels of oil a day, not to mention coal, gas and other fuels and industrial activity, the potential for degrading air quality is very real.

Over the last decade, instrumentation has been developed using satellite instruments like MOPITT to measure air quality over the globe and we have found that global transport of pollutants is very real.  It’s no good cleaning up your own production if the smog is coming over the fence from your neighbour!  Understanding the production, transport and destruction of pollutants is an important step in understanding how to manage them to keep air quality high.  The Measurements of Air Quality (MAQ) mission is a proposal to launch a full Canadian mission to study air quality with the objective of keeping it as good as possible over Canadian territory.

To launch such a mission requires a number of instruments operating in the ultra-violet, visible and infrared regions of the spectrum and using a variety of instrumental techniques.  This has to be backed up with sophisticated interpretation programs to untangle the complex electromagnetic signal that is received.

But satellites alone cannot solve all the problems and we need a serious ground-based effort to complement the satellites.  Since Canada has a serious interest in the Arctic, that is a good place to start and that is the role of the Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka.

Climate Change

Climate change is often in the news.  Scientifically, the debate over whether it is happening is pretty well over and the questions now being worked on are “how soon?” and “how much?”.  In order to do that, we need a great deal of data on the atmosphere gathered over along period of time over a large fraction of the planet.  A variety of instrumentation is required to gather that data and some of the required locations are extreme.  TOur Polar Environment Atmospheric Research Laboratory (PEARL) at Eureka, Nunavut is in an extreme environment which has all the properties of a “space station on the ground”:  limited access, tight quarters, sophisticated equipment to maintain with limited resources and a long supply line and, at some times of the year, difficulty with exterior activities.  Nonetheless the Arctic is one of the places where climate change is likely to be seen first and it is also likely to be profoundly affected in a comparatively short time.



Although it is pleasant and well-ordered to discuss these issues in isolation, they are not isolated.  Climate change affects ozone, which affects air quality, which affects climate which affects…. And so the scientist in this area has to be aware of multiple issues and synthesise many different aspects of the problem into a coherent whole.  This is what makes the subject so exciting, because the results actually matter and they are challenging to wrest from the data.  We find scope for developing instruments, taking data, developing analysis techniques and applying the results to real-world problems.

In times past I used to challenge students about talking to non-specialist audiences with the question “What can you tell a group of bankers about climate change that is relevant to them?”  The situation now is that much of what we do is relevant to that group and all the other groups in society.

The challenge now is to develop our understanding and increase our predictive capability to continue to contribute to the ongoing development of society.