Characterization of temperatures, clouds and aerosols in Jupiter from the troposphere to the stratosphere for a full Jovian year with IRTF-TEXES.

Long-term observations of Jupiter in the thermal IR have shown that the equatorial stratospheric temperatures oscillate on multi-year time-scales [1-2]. This oscillation affects not only the temperatures, but also the winds between the North and South Equatorial Belts at pressure levels of 0.1-40 mbar. This Jupiter Equatorial Stratospheric Oscillation (JESO) is apparently unrelated to seasons as Jupiter’s rotation axis is tilted by only 3.1°, and the equatorial stratosphere shifts from warm to cool temperature patterns with a variable period of 3.9-5.7 years, significantly different from to Jupiter’s orbital period of 11.9 Earth years. Previous studies based on analyses of infrared observations have shown that the JESO experiences major disruptions of its periodicity, principally related to tropospheric “Global Upheavals” [3] and large convective outbreaks developing in the troposphere away from the equator [4]. Numerical simulations reveal that vertically propagating gravity waves play a vital role in the nature of the oscillation depositing additional momentum from the troposphere up to the stratosphere [5-6]. The vertical extension of the oscillation is not well determined, since retrieving temperatures above or below the 1-20 mbar pressure range becomes more difficult. However, recent works that gather four decades of ground-based infrared observations reveal that the upper-tropospheric temperatures could also be affected by the JESO phenomena, thus coupling the tropospheric and stratospheric activity [7-8].

The first Jupiter observations made with the James Webb Space Telescope discovered an intense narrow equatorial jet located in the lower stratosphere (50-200 mbar), and it has been suggested to be a deep counterpart of JESO [9]. Additionally, a recent study of the variability of the equatorial winds and haze reflectivity in the upper troposphere suggest that the stratospheric jet could be detectable with methane images that probe the elevated hazes at 200-400 mbar [10]. Furthermore, changes in haze reflectivity from 2019 to 2022 suggest that a change in the hazes’ altitude could be the reason to detect the jet with images that sense deeper than the lower stratosphere.

In this work, we analyse mid-infrared IRTF-TEXES observations from 5 to 20 microns obtained over a full Jovian year to characterize the thermal state of Jupiter’s equatorial atmosphere. These multi-wavelength spectral cubes probe different altitudes, allowing the retrieval of temperatures from the stratosphere to the mid-troposphere, chemical distributions and aerosol opacity at the ammonia cloud level. We will show derived atmospheric properties through retrievals of the vertical structure of the atmosphere with the NEMESIS radiative-transfer and retrievals codes [11-12]. The spectroscopic inversions provide high resolution 3D profiles of temperatures, composition and aerosols that enable the study of a possible extension of the stratospheric oscillation to deeper levels, as well as to delve into the nature of brightness changes in the observed hazes. These results extend previous long-term studies [4,7-8] and will be essential to unveil the relation between stratospheric and tropospheric phenomena at the equator, and, therefore, the potential links between the JESO, the equatorial jet, and convective tropospheric activity.

 

References

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