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Science 6 July 1979:
Vol. 205. no. 4401, pp. 46 - 49
DOI: 10.1126/science.205.4401.46
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Articles

Thermal Contrast in the Atmosphere of Venus: Initial Appraisal from Pioneer Venus Probe Data

ALVIN SEIFF 1, DONN B. KIRK 1, RICHARD E. YOUNG 1, SIMON C. SOMMER 1, ROBERT C. BLANCHARD 2, JOHN T. FINDLAY 3, and G. M. KELLY 3

1 NASA Ames Research Center, Moffett Field, California 94035
2 NASA Langley Research Center, Hampton, Virginia 23665
3 Analytical Mechanics Associates, Hampton, Virginia 23666

The altitude profiles of temperature and pressure measured during the descent of the four Pioneer Venus probes show small contrast below the clouds but significant differences within the clouds at altitudes from 45 to 61 kilometers. At 60 kilometers, the probe which entered at 59.3° north latitude sensed temperatures 25 K below those of the lower latitude probes, and a sizable difference persisted down to and slightly below the cloud base. It also sensed pressure below those of the other probes by as much as 49 millibars at a mean pressure of 200 millibars. The measured pressure differences are consistent with cyclostrophic balance of zonal winds ranging from 130 ± 20 meters per second at 60 kilometers to 60 ± 17 meters per second at 40 kilometers, with evidence in addition of a nonaxisymmetric component of the winds. The clouds were found to be 10 to 20 K warmer than the extended profiles of the lower atmosphere, and the middle cloud is convectively unstable. Both phenomena are attributed to the absorption of thermal radiation from below. Above the clouds, in the lower stratosphere, the lapse rate decreases abruptly to 3.5 K per kilometer, and a superimposed wave is evident. At 100 kilometers, the temperature is minimum, with a mean value of about 170 K.

Submitted on May 15, 1979


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Venus: Chemical Weathering of Igneous Rocks and Buffering of Atmospheric Composition.
S. Nozette, S. NOZETTE, and J. S. LEWIS (1982)
Science 216, 181-183
   Abstract »    PDF »
Further Results of the Pioneer Venus Nephelometer Experiment.
J. BLAMONT and B. RAGENT (1979)
Science 205, 67-70
   Abstract »    PDF »
Venus Winds Are Zonal and Retrograde Below the Clouds.
C. C. COUNSELMAN III, S. A. GOUREVITCH, R. W. KING, G. B. LORIOT, and R. G. PRINN (1979)
Science 205, 85-87
   Abstract »    PDF »
Measurements of Turbulence in the Venus Atmosphere Deduced from Pioneer Venus Multiprobe Radio Scintillations.
R. WOO, J. W. ARMSTRONG, and W. B. KENDALL (1979)
Science 205, 87-89
   Abstract »    PDF »


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