Global climate: stratospheric hints

Over the course of the last decade, under European projects the high-altitude aircraft M-55 “Geophysica”, reequipped to become a flying laboratory, has gathered an enormous volume of information. It has studied the stratosphere of the Arctic and the Antarctic, it rose into the stratosphere over South America, Australia and soared over the Indian Ocean. As a result, the scientists, who are staff at the Central Upper-Air Observatory, have obtained a unique mass of data on the composition of the atmosphere at different altitudes. Analyzing these data, it is possible in the end to significantly raise the reliability of model calculations of both the current and future climates of Earth. The scientists are helped in their work by the International Science and Technology Centre.

Devices operating in automatic mode on board the aircraft enable data to be obtained on the composition of the stratosphere in different regions of the globe. Among them there are two devices, designed and built at the Central Upper-Air Observatory. One of them helps to determine the concentration of water vapours, even at a temperature of minus 90 degrees, when its content in the air is determined in millionths of shares of mass. The other helps to capture incredibly small concentrations of ozone, using a special, high-sensitive chemical reaction.

Project Manager Vladimir Yushkov, a Candidate of Physics and Mathematics agreed to explain why this information is necessary. “Global climate is that very instance where, without the present we can learn nothing at all about the future. And what is the “present” from the point of view of climate science? It is primarily precise knowledge of the condition of the environment. The more precise and voluminous the information on the condition of the atmosphere and the ocean, on the mechanisms of the formation of their temperature and dynamic regime and on solar activity, the more reliable the model calculations will be of future climatic changes”.

Unfortunately, it is rather difficult to capture climate change in accordance with data from observations conducted on the Earth’s surface. However, there are altitudes in the Earth’s atmosphere where even slight changes in the temperature of the Earth’s surface can bring about considerable temperature responses that can be measured to a fair degree of reliability. These are the stratospheric altitudes. But it is not enough to just know the temperatures of different layers of the stratosphere. One also has to know the composition of the stratospheric gases that influence the temperature regime. Primarily these are natural greenhouse gases, ozone and water vapour, the content of which is subjected to natural and anthropogenic changes. It is their concentration that was measured by the devices on board the high-altitude aircraft M-55 “Geophysica”.

However, it is not enough to have simply obtained these data. You also have to analyze them as it represents considerable interest for the study of exchange processes between the troposphere and the stratosphere, for identifying the mechanism of the chemical transfer of chemically active pollution to the ozone layer that reacts sensitively to them. The project of the Central Upper-Air Observatory, “The study of stratosphere-troposphere exchange” is devoted namely to this problem.

This problem really is interesting as, put very simply, in the troposphere, that is at altitudes of up to about 12km above the surface of the Earth, the temperature falls with a rise in altitude; the higher you go, the colder it becomes. And further still from the Earth, in the Stratosphere, everything is the reverse: the temperature rises the higher you go. The responsible party for this is the so-called ozone layer, the thickness of which depends on many things, including anthropogenic factors, of which one of the most important are chlorine- and bromide-containing compounds, the particularly woeful, well-known freons and certain other coolants. But how do they enter the altitude of the stratosphere from the surface, if we know that the troposphere and the stratosphere barely mix and exchange of chemical compounds between them is difficult?

The survey work of the Central Upper-Air Observatory will help to find an answer to this question. On the basis of data on the concentration of water vapours and ozone at different altitudes of the stratosphere over different sectors of the globe (in the Tropics and the polar latitudes), the researchers are developing models with which it will be possible, figuratively speaking, to “find the flow”. In other words, receiving new data on the mechanism of the distribution of greenhouse gases, their vertical and horizontal transfer. The scientists are confident that this research will significantly improve the model of the Earth’s climate and will produce predictions on its change that are more reliable.


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