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How Deep Are Planetary-Scale Changes in Jupiter? Clues from Juno Microwave Radiometer Observations

Presentation #505.07 in the session Origin and Evolution of Giant Planet Systems I (Oral Presentation)

Published onOct 23, 2023
How Deep Are Planetary-Scale Changes in Jupiter? Clues from Juno Microwave Radiometer Observations

The Juno Microwave Radiometer (MWR) has extended our knowledge of the structure and composition of the atmosphere down to several hundred bars, revealing meridional variability to great depth (e.g. Li et al. 2017 Geophys. Res. Lett. 44, 5317; Fletcher et al. 2021. J. Geophys. Res. 126, E06858). The MWR has revealed that some cyclonic and anticyclonic vortices may have roots at depths of tens of bars of pressure (Bolton, et al. 2021. Science 374, 968.), but 5-µm hot spots and associated plumes appear to be restricted to shallow depths above the water cloud (Fletcher et al. 2020, J. Geophys. Res. 125, e06399). We have tracked the evolution of the microwave brightness of Jupiter’s axisymmetric bands over 2016-2023. The work reported here concentrates on judging the depth of microwave variability in regions with prominent changes in the visible cloud properties. Our first results show that microwave brightness variability from channels sensitive to depths corresponding to 9-50 bars of atmospheric pressure, below the depth of water condensation, are present but are generally much smaller in amplitude than those at pressures of 0.7-3 bars. A prominent exception to this is in the northern component of Jupiter’s Equatorial Zone (2°-6°Nc), whose measured variability at depth does not correspond to any visible or infrared feature in the upper atmosphere, although it might be considered a precursor to the short-lived 2018-2019 Equatorial Zone disturbance. At 0.7-3 bars, a decrease in the antenna temperature in the northern component of the North Equatorial Belt (12°-15°Nc) is coincident with its visible brightening and drop of 5.1-µm radiance, both consistent with increased cloud and NH3 opacity in 2021. However, when the visibly dark and 5.1-µm bright North Equatorial Belt expanded northward into latitudes more typically associated with visibly bright regions that are cold at 5.1 µm (16°-19°Nc, known as the North Tropical Zone – see Fletcher, et al. 2017. Geophys. Res. Lett. 44, 7140), we do not detect any corresponding increase of the MWR brightness. Even further north, there are substantial changes in the visible and 5.1-µm appearance of the northern component of the North Temperate Belt (24°-26°Nc); although there are also substantial changes of the MWR brightness, the two do not appear to be correlated with one another. An important part of our next steps in this research will be to examine which of the MWR variabilities in the zonal-mean microwave brightness are the result of zonally discrete features in the atmosphere, particularly the North Equatorial Belt (6°-15°Nc).

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