Publication Abstracts

Diamante 1969

Diamante, J.M., 1969: The Structure and Circulation of the Lower Atmosphere of Venus. Ph.D. thesis. New York University.

Utilizing the available experimental data, an expression has been obtained for the microwave absorption coefficient in a planetary atmosphere composed principally of carbon dioxode, with some nitrogen and trace amounts of water vapor. This expression has been applied to a model of the atmosphere of Venus derived from the measurements of the Mariner 5 and Venera 4 spacecraft to determine the microwave brightness temperature and radar attenuation as functions of frequency. The results indicate that the final Venera 4 measurements at a distance of 6079 km from the planetary center do not represent the average conditions near the surface of Venus.

A simple numerical model of the general circulation of the lower atmosphere of Venus has been developed. Models with heating near the top or at the bottom of the atmosphere have been studied. The horizontal winds average from one to ten m/sec for all the models. If most of the heating takes place in the higher atmospheric layers, the model predicts a relatively gentle general circulation, with winds on the order of 1 m/sec, which may permit topographical decoupling of the circulation in the lower atmosphere. This suggests the possibility og substantially subadiabatic or even isothermal temperature lapse rates in these regions.

We have modified a computer program developed by E.J. Tindle, which intregrates the ideal gas law, the adiabatic condition, and the hydrostatic equation, to include the effects of compressibility in the calculation of the density and the temperature lapse rates. A lower isothermal layer has been included as an option. Various models of the atmosphere of Venus are then constructed by extrapolating the last Venera 4 measurements to the radar radius of 6053±3 km. The theoretical brightness temperatues and radar attenuations are then calculated and good agreement with the measure values is obtained.

The results indicate that the observations can be adequately explained on the basis of a dry atmosphere of carbon dioxide alone. However, the brightness temperatures for wet models including the effect of the 1.35 cm resonant line of water vapor have also been calculated. The inclusion of H2O in the theoretical models improve agreement with the measured brightness temperatures in the ranges 1 cm ≤ λ ≤ 3 cm.

The preiminary results of the Venera 5 measurements suggest a surface temperature of 803°K and a surface pressure of 140 atmospheres, while the corresponding measurements of Venera 6 are 673°K and 60 atmospheres. These values were obtained by adiabatic extrapolation of the lowest altitude measurements made by the capsules of these spacecraft. Our hydrostatic model predicts a temperature of 785.3°K and a pressure of 140.4 atmospheres at a distance of 6049.66 and 678.9°K and 60.21 atmospheres at 6063 km, for an adiabatic extrapolation.

The Venera 5 and Venera 6 measurements suggest that altitude variations of about 15 km exist on the surface of Venus. A 15 km isothermal layer will provide a drop of over 100°K in the brightness temperature at long wavelengths, improving the agreement between theoretical models and the direct radio observations at wavelengths greater than 10 cm.

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BibTeX Citation

  author={Diamante, J. M.},
  title={The Structure and Circulation of the Lower Atmosphere of Venus},
  school={New York University},
  address={New York, N.Y.},

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RIS Citation

ID  - di05000n
AU  - Diamante, J. M.
PY  - 1969
BT  - The Structure and Circulation of the Lower Atmosphere of Venus
PB  - New York University
CY  - New York, N.Y.
ER  -

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