Venus wind and temperature structure: The Venera 8 data

Abstract

Our analysis of the Venera 8 measurements yields equatorial morning terminator horizontal and vertical winds that are similar in a number of respects to the winds we obtained from our analysis of the Venera 7 measurements. The lower boundary of the horizontal retrograde '4-day' wind is defined by a 50-60% decrease in wind speed in the vicinity of 44 km, and there exists a retrograde wind 'plateau' of 15to 40-m/s winds extending from 40 km down to the vicinity of 18 km, where the winds decrease rapidly to the order of 0.1 m/s near the surface. Updrafts of 2-5 m/s exist in the vicinity of 20-30 km and are apparently associated with a slightly superadiabatic lapse rate. The location of the descent of the Venera 8 probe [Marot) at al., 1973a, b] is shown in solar coordinates in Figure 1. Descent started on the light side of the planet approximately 600 km from the morning terminator and 1000 km south of the equator. At this location the geometric position of the sun was roughly 5.5 above the horizon, and the atmosphere had been in sunlight for approximately 18 earth hours, The direction of earth was N65E at 38 from the zenith. During descent the strong retrograde equatorial wind carried the probe approximately 80 km to the west toward the sun. The basic atmospheric data [Marot) at al., 1973a] that we have used comprise descent probe measurements of' (1) temperature versus time T(t), obtained by means of four gages having ranges of approximately 320-860, 280-710, 470-810, and 290-880 K, (2) pressure P(t), obtained by means of four gages having ranges of 0-77, 0-97, 0-145, and 0-193 atm, and (3) altitude h(t), obtained by means of a pulse radar. In addition we use the Doppler content f(t) of the descent probe telemetry signal received on earth.