Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996dps....28.1403b&link_type=abstract
American Astronomical Society, DPS meeting #28, #14.03; Bulletin of the American Astronomical Society, Vol. 28, p.1117
Astronomy and Astrophysics
Astronomy
Scientific paper
Large cellular features observed near the subsolar point of Venus' atmosphere in Mariner 10, Pioneer Venus, and Galileo UV images may be the manifestation of thermal convection. The cellular features are located at roughly 65 km altitude. However, the likely site of convection is a neutrally stable layer whose altitude in regions away from the subsolar point has been determined by Pioneer Venus and Vega-2 probes to be 48-55 km, 10 km below the cellular features. We present calculations suggesting that the convection layer may be much thicker in the subsolar region, possibly extending to the altitude of the observed cells. A two-dimensional, fully compressible, internally heated nonlinear convection model is used to investigate cloud-level convection in Venus' atmosphere from 40-60 km altitude. Two cases are presented for the subsolar point: a moderate Rayleigh number simulation (Ra = 6.8 x 10(6) ) and a high Rayleigh number simulation (Ra = 1.1 x 10(9) ). The stable layer overlying the convection region is substantially weakened by solar heating and convective entrainment for the moderate Ra case and is completely eroded away in the high Ra case. Downward convective penetration also weakens the underlying stable layer. Consequently, the neutrally stable layer extends from 47-56 km altitude for the moderate Ra case and from 46-60 km altitude for the high Ra case. Downflow plumes penetrate deeply into the underlying stable layer, with average penetration reaching altitudes of 42.7 km and 40.7 km for the moderate and high Rayleigh number cases, respectively. Thus, convection may dominate the dynamics within a 20 km thick layer (or larger) in the subsolar region.
Baker Don R.
Jones Peter W.
Schubert Gerald
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