Materials of the International Conference
50th Anniversary of the International Geophysical Year
and Electronic Geophysical Year

16-19 September 2007 • Suzdal, Russia

Climate change and variations in composition of the middle and upper atmosphere of the Earth over the last century

G. S. Golitsyn and A. I. Semenov

Obukhov Institute of the physics of atmosphere, Russian Academy of Sciences, Moscow, Russia

Abstract

According to data of the World Meteorological Organization, air temperature in near-the-Earth layer raised by 0.6–0.7 K over the last 100 years. In relation to this problem, climate conditions of the middle and upper atmosphere become an issue of crucial importance. This is connected with possible irreversible after-effects of anthropogenic changes of chemical composition of the atmosphere, and also with the fact that according to theoretical models the global changes in a thermal regime of the upper layers of the atmosphere should be revealed to a greater extent than in near-the-Earth layer. Database on the thermal regime was needed for investigations of the climate changes in the upper layers of the atmosphere. Creation of such data base started in the period of the International Geophysical Year, when under the guidance of professor V. I. Krassovsky a network of spectrophotometric measurements of atmospheric temperature at the heights of mesosphere and thermosphere from emissions of their own radiation was created. Later the bank of temperature data was supplemented with data of rocket and ionospheric measurements. This allowed to obtain vertical temperature profiles on the basis of extended ranges of data (1955–2006). These profiles revealed cooling of the middle and upper atmosphere, occurring at various heights at a rate of –(0.2–0.7) K per year. Tendency of perennial change of temperature for the mesopause region was found to have a non-linear character. The trend values for the time intervals of 1955–1992 and 1992–2006 were –(0.7) K per year and –(0.2–0.3) K per year correspondingly. Another important result is the fact that obtained profiles witness a decrease of heights, with constant temperature value. It reveals the gradual subsidence of the middle and upper atmosphere over the period of study (rate of this subsidence was about –50 m per year and –120 m per year for the heights of 70 and 100 km correspondingly). This is also confirmed by data of ionospheric soundings from 1948 until 1990, which revealed that the height of maximum of ionospheric F2 layer was decreasing at a rate of –250 m per year. Perennial measurements of mesopause temperature allowed us to reveal important features of its changes for the winter and the summer seasons of the year. For winter conditions, cooling down of mesopause took place, with a trend of –0.8 K per year. For summer conditions, the value of temperature trend was close to zero. The observed decrease in temperature differences between the winter and summer hemispheres at these heights is consistent with the observed marked decrease of the amplitude of meridional component of the wind. Created temperature data bank was used for obtaining vertical profiles of a response of atmospheric temperature on the solar activity at medium and high latitudes.

Citation: G. S. Golitsyn and A. I. Semenov (2007), Climate change and variations in composition of the middle and upper atmosphere of the Earth over the last century, in: Materials of the International Conference '50th Anniversary of the International Geophysical Year and Electronic Geophysical Year', GC RAS, Moscow, doi:10.2205/2007-IGY50conf.

© 2007 Geophysical Center RAS and authors


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