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| Titel |
Cooling of the mesosphere and lower thermosphere due to doubling of CO2 |
| VerfasserIn |
R. A. Akmaev, V. I. Fomichev |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 16, no. 11 ; Nr. 16, no. 11, S.1501-1512 |
| Datensatznummer |
250013546
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| Publikation (Nr.) |
 copernicus.org/angeo-16-1501-1998.pdf |
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| Zusammenfassung |
A new parameterization of infrared radiative
transfer in the 15-μm CO2 band has been incorporated into the Spectral
mesosphere/lower thermosphere model (SMLTM). The parameterization is applicable
to calculations of heating rates above approximately 15 km for arbitrary
vertical profiles of the CO2 concentration corresponding to the
surface mixing ratio in the range 150–720 ppm. The sensitivity of the mesosphere
and lower thermosphere (MLT) to doubling of CO2 has been studied. The
thermal response in the MLT is mostly negative (cooling) and much stronger than
in the lower atmosphere. An average cooling at the stratopause is about 14 K. It
gradually decreases to approximately 8 K in the upper mesosphere and again
increases to about 40–50 K in the thermosphere. The cooling and associated
thermal shrinking result in a substantial density reduction in the MLT that
reaches 40–45% in the thermosphere. Various radiative, chemical, and dynamical
feedbacks potentially important for the thermal response in the MLT are
discussed. It is noted that the results of simulations are strikingly similar to
observations of long-term trends in the MLT. This suggests that during the last
3–4 decades the thermal structure in the real upper atmosphere has undergone
substantial changes driven by forcing comparable with that due to doubling of CO2.
Key words. Meteorology and atmospheric dynamics
(Climatology · Middle atmosphere dynamics · Thermospheric dynamics) |
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