Venus middle-atmosphere temperatures from Venera 15

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Venus middle-atmosphere temperatures from Venera 15

Spänkuch, D. / Matsygorin, I.A. / Dubois, R. / Zasova, L.V.

Abstract The temperature structure of the Venusian middle atmosphere derived from the Venera-15 Fourier spectrometer confirms in general previous investigations summarized in the Venus International Reference Atmosphere 1985. A detailed Fourier analysis of the temperature field in the solar fixed coordinate system shows generally a different behaviour for low (ϕ ≲ 50°) and high (ϕ ≳ 55°) latitudes, a predominance of wavenumber-2 with a full cl (360°) from the cloud top up to about 95 km at low latitudes and an anti-clockwise rotation of 180° at high latitudes. The amplitudes are, however, for both Fourier components less than 2 – 3 K. Larger amplitudes (> 4 K) are found at high latitudes in spectral intervals representing the upper cloud top, where wavenumber-1 is dominant. The maximum wavenumber-1 amplitude for the cloud top occurs at the morning terminator at high latitudes and around 2 p.m. at low latitudes. Temporary changes in the outgoing longwave flux at the North Pole (ϕ ≳ 85°) are closely related to the cloud top temperature, which indicates variation in the upper cloud top height by about 10 km. The accompanying temperature variations are different in different altitude ranges and reveal a complicated behaviour of the polar atmosphere.