Long-term variations of Venus' 365-nm albedo observed by Venus Express, Akatsuki, MESSENGER, and Hubble Space Telescope

Abstract

An unknown absorber near the cloud top level of Venus generates a broad absorption feature from the ultraviolet (UV) to visible, peaking around 360 nm, and therefore plays a critical role in the solar energy absorption. We present a quantitative study on the variability of the cloud albedo at 365 nm and its impact on Venus' solar heating rates based on an analysis of Venus Express and Akatsuki's UV images, and Hubble Space Telescope and MESSENGER's UV spectral data; in this analysis the calibration correction factor of the UV images of Venus Express (VMC) is updated relative to the Hubble and MESSENGER albedo measurements. Our results indicate that the 365-nm albedo varied by a factor of 2 from 2006 to 2017 over the entire planet, producing a 25-40% change in the low latitude solar heating rate according to our radiative transfer calculations. Thus, the cloud top level atmosphere should have experienced considerable solar heating variations over this period. Our global circulation model calculations show that this variable solar heating rate may explain the observed variations of zonal wind from 2006 to 2017. Overlaps in the timescale of the long-term UV albedo and the solar activity variations make it plausible that solar extreme UV intensity and cosmic-ray variations influenced the observed albedo trends. The albedo variations might also be linked with temporal variations of the upper cloud SO2 gas abundance, which affects the H2SO4-H2O aerosol formation.

22 pages, 16 figures, accepted

References in corpus (8)

• Cosmic Rays and Climate
• Predictability of the solar cycle over one cycle
• Six years of Venus winds at the upper cloud level from UV, visible and near infrared observations from VIRTIS on Venus Express
• Venus upper clouds and the UV-absorber from MESSENGER/MASCS observations
• Latitudinal Variation of Clouds' Structure Responsible for Venus' Cold Collar
• Glory revealed in disk-integrated photometry of Venus
• Return to Venus of the Japanese Venus Climate Orbiter AKATSUKI
• Titan brighter at twilight than in daylight

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• Investigation of UV absorbers on Venus using the 283 and 365 nm phase curves obtained from Akatsuki
• Venus Cloud Research: Progress and Perspectives
• A Recharge Oscillator Model for Interannual Variability in Venus' Clouds