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Register a new userNear-Infrared atmospheric modelling of Jupiters South Equatorial Belt (SEB) observed with AAT/IRIS2
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Added by
Behrooz Karamiqucham
Publication date
2021
fields
Physics
and research's language is
English
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Near-Infrared spectra of Jupiters South Equatorial Belt (SEB) with AAT/IRIS2 in H and K bands at a resolving power of R~2400 have been obtained. By creating line-by-line radiative transfer models with the latest improved spectral line data for ammonia and methane (HITRAN2016), we derive best models of cloud/haze parameters in Jupiters South Equatorial Belt. The modelled spectra fit the observations well except for small, isolated discrepancies in the trough region of H2-H2 collision-induced-absorption around 2.08 {mu}m and the methane absorption level between 2.16 and 2.19 {mu}m in K band and at the high pressure methane window between 1.596 to 1.618 {mu}m in H band.
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Moist convective storms in Jupiter develop frequently and can trigger atmospheric activity of different scales, from localized storms to planetary-scale disturbances including convective activity confined inside a larger meteorological system. In February 2018 a series of convective storms erupted in Jupiters South Temperate Belt (STB) (planetocentric latitudes from -23$^{circ}$ to -29.5$^{circ}$). This occurred inside an elongated cyclonic region known popularly as the STB Ghost, close to the large anticyclone Oval BA, resulting in the clouds from the storms being confined to the cyclone. The initial storms lasted only a few days but they generated abundant enduring turbulence. They also produced dark features, possibly partially devoid of clouds, that circulated around the cyclone over the first week. The subsequent activity developed over months and resulted in two main structures, one of them closely interacting with Oval BA and the other one being expelled to the west. Here we present a study of this meteorological activity based on daily observations provided by the amateur community, complemented by observations obtained from PlanetCam UPV/EHU at Calar Alto Observatory, the Hubble Space Telescope and by JunoCam on the Juno spacecraft. We also perform numerical simulations with the EPIC General Circulation Model to reproduce the phenomenology observed. The successful simulations require a complex interplay between the Ghost, the convective eruptions and Oval BA, and they demonstrate that water moist convection was the source of the initial storms. A simple scale comparison with other moist convective storms that can be observed in the planet in visible and methane absorption band images strongly suggests that most of these storms are powered by water condensation instead of ammonia.
The dark colors of Jupiters North Equatorial Belt (NEB, $7-17^circ$N) appeared to expand northward into the neighboring zone in 2015, consistent with a 3-5 year cycle of activity in the NEB.
Mid-infrared 7-20 $mu$m imaging of Jupiter demonstrates that the increased albedo of Jupiters South Equatorial Belt (SEB) during the `fade (whitening) event of 2009-2010 was correlated with changes to atmospheric temperature and aerosol opacity. The opacity of the tropospheric condensation cloud deck at pressures less than 800 mbar increased by 80% between May 2008 and July 2010, making the SEB ($7-17^circ$ S) as opaque in the thermal infrared as the adjacent equatorial zone. After the cessation of discrete convective activity within the SEB in May 2009, a cool quiescent band of high aerosol opacity (the SEB zone at $11-15^circ$ S) was observed separating the cloud-free northern and southern SEB components. The cooling of the SEBZ (with peak-to-peak contrasts of $1.0pm0.5$ K), as well as the increased aerosol opacity at 4.8 and 8.6 $mu$m, preceded the visible whitening of the belt by several months. A chain of five warm, cloud-free `brown barges (subsiding airmasses) were observed regularly in the SEB between June 2009 and June 2010, by which time they too had been obscured by the enhanced aerosol opacity of the SEB, although the underlying warm circulation was still present in July 2010. The cool temperatures and enhanced aerosol opacity of the SEBZ after July 2009 are consistent with an upward flux of volatiles from deeper levels (e.g., ammonia-laden air) and enhanced condensation, obscuring the blue-absorbing chromophore and whitening the SEB by April 2010. Revival of the dark SEB coloration in the coming months will ultimately require sublimation of these ices by subsidence and warming of volatile-depleted air. [Abridged]
We present revised near-infrared albedo fits of 2835 Main Belt asteroids observed by WISE/NEOWISE over the course of its fully cryogenic survey in 2010. These fits are derived from reflected-light near-infrared images taken simultaneously with thermal emission measurements, allowing for more accurate measurements of the near-infrared albedos than is possible for visible albedo measurements. As our sample requires reflected light measurements, it undersamples small, low albedo asteroids, as well as those with blue spectral slopes across the wavelengths investigated. We find that the Main Belt separates into three distinct groups of 6%, 16%, and 40% reflectance at 3.4 um. Conversely, the 4.6 um albedo distribution spans the full range of possible values with no clear grouping. Asteroid families show a narrow distribution of 3.4 um albedos within each family that map to one of the three observed groupings, with the (221) Eos family being the sole family associated with the 16% reflectance 3.4 um albedo group. We show that near-infrared albedos derived from simultaneous thermal emission and reflected light measurements are an important indicator of asteroid taxonomy and can identify interesting targets for spectroscopic followup.
Oxygen is the most common element after hydrogen and helium in Jupiters atmosphere, and may have been the primary condensable (as water ice) in the protoplanetary disk. Prior to the Juno mission, in situ measurements of Jupiters water abundance were obtained from the Galileo Probe, which dropped into a meteorologically anomalous site. The findings of the Galileo Probe were inconclusive because the concentration of water was still increasing when the probe died. Here, we initially report on the water abundance in the equatorial region, from 0 to 4 degrees north latitude, based on 1.25 to 22 GHz data from Juno Microwave radiometer probing approximately 0.7 to 30 bars pressure. Because Juno discovered the deep atmosphere to be surprisingly variable as a function of latitude, it remains to confirm whether the equatorial abundance represents Jupiters global water abundance. The water abundance at the equatorial region is inferred to be $2.5_{-1.6}^{+2.2}times10^3$ ppm, or $2.7_{-1.7}^{+2.4}$ times the protosolar oxygen elemental ratio to H (1$sigma$ uncertainties). If reflective of the global water abundance, the result suggests that the planetesimals formed Jupiter are unlikely to be water-rich clathrate hydrates.
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