http://arxiv.org/abs/1903.02883
The Venusian atmosphere is covered by clouds with super-rotating winds whose accelerating mechanism is still not well understood. The fastest winds, occurring at the cloud tops ($\sim$70 km height), have been studied for decades thanks to their visual contrast in dayside ultraviolet images. The middle clouds ($\sim$50-55 km) can be observed at near-infrared wavelengths (800-950 nm), although with very low contrast. Here we present the first extensive analysis of their morphology and motions at lower latitudes along 2016 with 900-nm images from the IR1 camera onboard Akatsuki. The middle clouds exhibit hemispherical asymmetries every 4-5 days, sharp discontinuities in elongated “hook-like” stripes, and large contrasts (3-21%) probably associated with large changes in the optical thickness. Zonal winds obtained with IR1 images and with ground-based observations reveal mean zonal winds peaking at the equator, while their combination with Venus Express unveils long-term variations of 20 m s$^{-1}$ along 10 years.
J. Peralta, N. Iwagami, S. Sánchez-Lavega, et. al.
Fri, 8 Mar 19
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Comments: 18 pages, 4 figures