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Register a new userMapping the zonal winds of Jupiters stratospheric equatorial oscillation
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Since the 1950s, quasi-periodic oscillations have been studied in the terrestrial equatorial stratosphere. Other planets of the solar system present (or are expected to present) such oscillations, like the Jupiter Equatorial Oscillation(JEO) and the Saturn Semi-Annual Oscillation (SSAO). In Jupiters stratosphere, the equatorial oscillation of its relative temperature structure about the equator, is characterized by a quasi-period of 4.4 years. The stratospheric wind field in Jupiters equatorial zone has never been directly observed. In this paper, we aim at mapping the absolute wind speeds in Jupiters equatorial stratosphere to quantify vertical and horizontal wind and temperature shear. Assuming geostrophic equilibrium, we apply the thermal wind balance using nearly simultaneous stratospheric temperature measurements between 0.1 and 30 mbar performed with Gemini/TEXES and direct zonal wind measurements derived at 1 mbar from ALMA observations, all carried out between March 14th and 22nd, 2017. We are thus able to calculate self-consistently the zonal wind field in Jupiters stratosphere where the JEO occurs. We obtain stratospheric map of the zonal wind speeds as a function of latitude and pressure about Jupiters equator for the first time. The winds are vertically layered with successive eastward and westward jets. We find a 200 m/s westward jet at 4 mbar at the equator, with a typical longitudinal variability on the order of ~50 m/s. By extending our wind calculations to the upper troposphere, we find a wind structure qualitatively close to the wind observed using cloud-tracking techniques. Nearly simultaneous temperature and wind measurements, both in the stratosphere, are a powerful tool for future investigations of the JEO (and other planetary equatorial oscillations) and its temporal evolution.
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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.
We present multi-wavelength measurements of the thermal, chemical, and cloud contrasts associated with the visibly dark formations (also known as 5-$mu$m hot spots) and intervening bright plumes on the boundary between Jupiters Equatorial Zone (EZ) and North Equatorial Belt (NEB). Observations made by the TEXES 5-20 $mu$m spectrometer at the Gemini North Telescope in March 2017 reveal the upper-tropospheric properties of 12 hot spots, which are directly compared to measurements by Juno using the Microwave Radiometer (MWR), JIRAM at 5 $mu$m, and JunoCam visible images. MWR and thermal-infrared spectroscopic results are consistent near 0.7 bar. Mid-infrared-derived aerosol opacity is consistent with that inferred from visible-albedo and 5-$mu$m opacity maps. Aerosol contrasts, the defining characteristics of the cloudy plumes and aerosol-depleted hot spots, are not a good proxy for microwave brightness. The hot spots are neither uniformly warmer nor ammonia-depleted compared to their surroundings at $p<1$ bar. At 0.7 bar, the microwave brightness at the edges of hot spots is comparable to other features within the NEB. Conversely, hot spots are brighter at 1.5 bar, signifying either warm temperatures and/or depleted NH$_3$ at depth. Temperatures and ammonia are spatially variable within the hot spots, so the precise location of the observations matters to their interpretation. Reflective plumes sometimes have enhanced NH$_3$, cold temperatures, and elevated aerosol opacity, but each plume appears different. Neither plumes nor hot spots had microwave signatures in channels sensing $p>10$ bars, suggesting that the hot-spot/plume wave is a relatively shallow feature.
The purpose of this HST white paper is to demonstrate that it is possible to monitor Jupiters polar haze with HST/STIS without breaking the ground screening limit for bright objects. This demonstration rests on a thorough simulation of STIS output from an existing image obtained with HST/WFPC2. It is shown that the STIS NUV-MAMA + F25CIII filter assembly provides a count rate per pixel ~11 times smaller than that obtained for one pixel of WFPC2 WF3 CCD + F218W corresponding filter. This ratio is sufficiently large to cope with the bright solar light scattered by Jupiters atmosphere, which was a lesser concern for WFPC2 CCD safety. These STIS images would provide unprecedented spatial and temporal resolution observations of small-scale stratospheric aerosol structures, possibly associated with Jupiters complex FUV aurora.
Observations of planets throughout our Solar System have revealed that the Earth is not alone in possessing natural, inter-annual atmospheric cycles. The equatorial middle atmospheres of the Earth, Jupiter and Saturn all exhibit a remarkably similar phenomenon - a vertical, cyclic pattern of alternating temperatures and zonal (east-west) wind regimes that propagate slowly downwards with a well-defined multi-Earth-year period. Earths Quasi-Biennial Oscillation (QBO, observed in the lower stratospheres with an average period of 28 months) is one of the most regular, repeatable cycles exhibited by our climate system, and yet recent work has shown that this regularity can be disrupted by events occurring far away from the equatorial region, an example of a phenomenon known as atmospheric teleconnection. Here we reveal that Saturns equatorial Quasi-Periodic Oscillation (QPO, with a ~15-year period) can also be dramatically perturbed. An intense springtime storm erupted at Saturns northern mid-latitudes in December 2010, spawning a gigantic hot vortex in the stratosphere at $40^circ$N that persisted for 3 years. Far from the storm, the Cassini temperature measurements showed a dramatic $sim10$-K cooling in the 0.5-5 mbar range across the entire equatorial region, disrupting the regular QPO pattern and significantly altering the middle-atmospheric wind structure, suggesting an injection of westward momentum into the equatorial wind system from waves generated by the northern storm. Hence, as on Earth, meteorological activity at mid-latitudes can have a profound effect on the regular atmospheric cycles in the tropics, demonstrating that waves can provide horizontal teleconnections between the phenomena shaping the middle atmospheres of giant planets.
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.
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