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Joseph S. Hogan and Kenneth Grossman

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Joseph S. Hogan and Richard W. Stewart

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Richard W. Stewart and Joseph S. Hogan

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C. Prabhakara and Joseph S. Hogan Jr.

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Recent high-resolution infrared spectroscopic investigations by Kaplan, Münch and Spinrad (1964) have resulted in estimates of the surface pressure and atmospheric composition of the planet Mars which differ considerably from those previously given. In the light of these findings, the radiative equilibrium temperature structure of the atmosphere of the planet has been re-examined. The absorption of solar energy in the ultraviolet (UV) and visible by O2 and O3 and in the near infrared (IR) by CO2 has been included in the calculation of atmospheric heating.

The transmission functions of CO2 were theoretically calculated making use of a “statistical” model for band absorption. These transmission functions were then used to evaluate the absorption of solar energy in the near IR and to investigate the radiative transfer in the far IR. The theoretical band parameters, involving the line intensity and the mean ratio of line half-width to line spacing, were derived using the transmittance tables of CO2 presented by Stull, Wyatt and Plass (1963).

The basic photochemical theory of O3 production was used to determine a vertical O3 distribution consistent with the radiative equilibrium temperature structure.

The equation of radiative transfer was numerically integrated avoiding the empirical relationships commonly involved in the pressure dependence of CO2 absorption. The IR flux transmittance was also calculated without any simplifying assumptions.

Our approach to the radiative transfer problem was not a time-marching one in which a final solution requires the rate of heating to become zero. Instead, we have treated it as a steady state problem in which we require, at each step, equality between absorbed and emitted energies for all levels.

We have calculated radiative equilibrium temperatures from the surface to the 100-km level. For surface temperatures ranging from 230 K to 270 K, surface pressures from 10 mb to 50 mb, and CO2 amounts from 40 m atm to 70 m atm, the “tropopause” is found at levels below 10 km. Within these limits of surface temperature and pressure and CO2 amounts, the temperature above the tropopause steadily decreases toward a value of ∼155 K in the upper layers. The results indicate definitely that no temperature maximum is produced by the absorption of solar energy in the UV by O3 or in the near IR by CO2 in the Martian atmosphere. The maximum O3 number density is found at the surface of Mars with a gradual decrease upward. The total amount of O3 present is about one-tenth of the amount found in the Earth's atmosphere (∼0.3 cm atm). The total UV energy absorbed in the Martian atmosphere by O2 and O3 is comparable to the near IR energy absorbed by CO2. However, the vertical distribution of absorbed energy shows that, below ∼30 km, O2 and O3 absorption is comparable to CO2 absorption, while above this level CO2 absorption becomes considerably larger.

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Joseph S. Hogan, S. I. Rasool, and Thérèse Encrenaz

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Thermal structure calculations have been carded out for the atmosphere of Jupiter above the level of the dense clouds, for boundary conditions suggested by recent observations. The resulting models are characterized by an extensive region of dynamical control above the cloud level, and a thermal inversion in the mesosphere, produced by absorption of solar IR energy in the 3020 cm−1 band of methane. The infrared and microwave spectra corresponding to the computed thermal models are found to be in generally good agreement with observed infrared and microwave brightness temperature of Jupiter. The effective temperatures of all of the thermal models are higher than the solar equilibrium value, and, thus, an internal heat source on Jupiter is suggested.

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