The importance of dynamical feedbacks on doubled CO2‐induced changes in the thermal structure of the mesosphere

The Garcia-Solomon two-dimensional model was used to study the effect of doubled carbon-dioxide on the middle atmosphere. The model has been improved to include non-LTE CO2 cooling in the 15 micron band above 70 km and new chemical heating and heating efficiencies. The effect of doubling CO2 on the temperature is found to be large at the stratopause (about 10–12K cooling) and at the mesopause (about 6–12K cooling). In the stratosphere, dynamical feedbacks on the heating rate caused by the temperature changes are small compared to the radiative changes while in the mesosphere they can be large. In fact, calculations with the present dynamical heating rates used in the doubled CO2 energy equation indicate that the radiative forcing alone could cause a temperature increase of about 10K in the polar summer mesopause region. The dynamical feedbacks which oppose this positive radiative forcing are discussed.

[1]  M. Mlynczak,et al.  A detailed evaluation of the heating efficiency in the middle atmosphere , 1993 .

[2]  M. Dameris,et al.  Cooling of the Upper Atmosphere due to CO2 Increases: A Model Study , 1993 .

[3]  Richard H. Picard,et al.  Line‐by‐line radiative excitation model for the non‐equilibrium atmosphere: Application to CO2 15‐μm emission , 1992 .

[4]  Franz-Josef Lübken,et al.  Thermal structure of the mesopause region at polar latitudes , 1991 .

[5]  J. Kiehl,et al.  A new parameterization of the absorptance due to the 15‐μm band system of carbon dioxide , 1991 .

[6]  David Rind,et al.  Climate change and the middle atmosphere. I - The doubled CO2 climate , 1990 .

[7]  J. Barnett,et al.  Zonal mean temperature, pressure, zonal wind and geopotential height as functions of latitude , 1990 .

[8]  Raymond G. Roble,et al.  How will changes in carbon dioxide and methane modify the mean structure of the mesosphere and thermosphere , 1989 .

[9]  G. Brasseur,et al.  Stratospheric Response to Trace Gas Perturbations: Changes in Ozone and Temperature Distributions , 1988, Science.

[10]  R. Garcia,et al.  The role of molecular hydrogen and methane oxidation in the water vapour budget of the stratosphere , 1988 .

[11]  Rolando R. Garcia,et al.  The effect of breaking gravity waves on the dynamics and chemical composition of the mesosphere and lower thermosphere , 1985 .

[12]  R. Dickinson.  Infrared radiative cooling in the mesosphere and lower thermosphere , 1984 .

[13]  R. Garcia,et al.  A numerical model of the zonally averaged dynamical and chemical structure of the middle atmosphere , 1983 .

[14]  J. D. Mahlman,et al.  Stratospheric Sensitivity to Perturbations in Ozone and Carbon Dioxide: Radiative and Dynamical Response. , 1980 .