THE THERMAL STRUCTURE AND DYNAMICS OF THE ATMOSPHERE OF VENUS BETWEEN70 AND 90 KM FROM THE GALILEO-NIMS SPECTRA

An analysis of thermal profiles and dynamics over a wide range of lati tudes for the venusian atmosphere between 70 and 90 km is presented ba sed on high spatial resolution infrared spectra of the night side obta ined by the near infrared mapping spectrometer (NIMS) experiment durin g the Galileo-Venus encounter in February 1990. Using the 4.3-mu m CO2 absorption band, the temperature profile is retrieved in the 75- to 9 1-km altitude region over a latitudinal range of -59 degrees to +64 de grees. Compared to earlier observations from the Pioneer Venus mission , the temperature at 91 km is about 10 K higher and between 74 and 83 km about 3.6 K colder. An equator to pole warming at constant pressure levels is found and implications for the zonal wind profiles are draw n under the assumption that the atmosphere is in cyclostrophic balance in the region of 70 to 90 km. The results are in correspondence with direct wind measurements from ground-based observations at 95 km and 1 05 km altitude. (C) 1995 Academic Press, Inc.