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Moist Convection and the 2010-2011 Revival of Jupiter's South Equatorial Belt

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posted on 2017-01-04, 09:51 authored by Leigh N. Fletcher, G. S. Orton, J. H. Rogers, R. S. Giles, A. V. Payne, P. G. J. Irwin, M. Vedovato
The transformation of Jupiter’s South Equatorial Belt (SEB) from its faded, whitened state in 2009-2010 (Fletcher et al., 2011b) to its normal brown appearance is documented via comparisons of thermal-infrared (5-20 µm) and visible-light imaging between November 2010 and November 2011. The SEB revival consisted of convective eruptions triggered over ∼ 100 days, potentially powered by the latent heat released by the condensation of water. The plumes rise from the water cloud base and ultimately diverge and cool in the stably-stratified upper troposphere. Thermal-IR images from the Very Large Telescope (VLT) were acquired 2 days after the SEB disturbance was first detected as a small white spot by amateur observers on November 9th 2010. Subsequent images over several months revealed the cold, putatively anticyclonic and cloudy plume tops (area 2.5 × 106 km2 ) surrounded by warm, cloud-free conditions at their peripheries due to subsidence. The latent heating was not directly detectable in the 5-20 µm range. The majority of the plumes erupted from a single source near 140−160◦W, coincident with the remnant cyclonic circulation of a brown barge that had formed during the fade. The warm remnant of the cyclone could still be observed in IRTF imaging 5 days before the November 9th eruption. Additional plumes erupted from the leading edge of the central disturbance immediately east of the source, which propagated slowly eastwards to encounter the Great Red Spot. The tropospheric plumes were sufficiently vigorous to excite stratospheric thermal waves over the SEB with a 20−30◦ longitudinal wavelength and 5-6 K temperature contrasts at 5 mbar, showing a direct connection between moist convection and stratospheric wave activity. The subsidence and compressional heating of dry, unsaturated air warmed the troposphere (particularly to the northwest of the central branch of the revival) and removed the aerosols that had been responsible for the fade. Dark, cloud-free lanes west of the plumes were the first to show the colour change, and elongated due to the zonal windshear to form the characteristic ‘S-shape’ of the revival complex. The aerosol-free air was redistributed and mixed throughout the SEB by the zonal flow, following a westward-moving southern branch and an eastwardmoving northern branch that revived the brown colouration over ∼ 200 days. The transition from the cool conditions of the SEBZ during the fade to the revived SEB caused a 2-4 K rise in 500-mbar temperatures (leaving a particularly warm southern SEB) and a reduction of aerosol opacity by factors of 2-3. Newly-cleared gaps in the upper tropospheric aerosol layer appeared different in filters sensing the ∼ 700-mbar cloud deck and the 2-3 bar cloud deck, suggesting complex vertical structure in the downdrafts. The last stage of the revival was the re-establishment of normal convective activity northwest of the GRS in September 2011, ∼ 840 days after the last occurrence in June 2009. Moist convection may therefore play an important role in controlling the timescale and atmospheric variability during the SEB life cycle.

Funding

Fletcher was supported by a Royal Society Research Fellowship at the University of Leicester, Giles was supported by a Royal Society research grant at the University of Oxford. The UK authors acknowledge the support of the Science and Technology Facilities Council (STFC). A portion of this work was performed by Orton and Payne at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. This research used the ALICE High Performance Computing Facility at the University of Leicester. We are extremely grateful for the combined efforts of the numerous amateur observers (including those listed in the figure captions) for sharing their data, and for the JUPOS software developed by Grischa Hahn and Hans-Jorg Mettig to reproject the visible-light data. ¨ This investigation was partially based on thermal-infrared observations acquired at (i) the ESO Very Large Telescope Paranal UT3/Melipal Observatory using Directors Discretionary Time (program ID 286.C-5009) and regular service time (program ID 087.C-0024); (ii) the Subaru Telescope, which is 27 operated by the National Astronomical Observatory of Japan (program ID O11154); (iii) NASA’s Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration (program IDs 2010B010, 2011A010, 2011B027); and (iv) observations obtained at the Gemini Observatory (program IDs GN-2010B-DD-3, GS-2010B-Q-8 and GS-2011AQ-11), which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnolog´ıa e Innovacion Productiva (Argentina), and ´ Ministerio da Ci ´ encia, Tecnologia e Inovac¸ ˆ ao (Brazil). We wish ˜ to recognise and acknowledge the very signif

History

Citation

Icarus 2017, 286, pp. 94–117

Author affiliation

/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy

Version

  • VoR (Version of Record)

Published in

Icarus 2017

Publisher

Elsevier for Academic Press

issn

1090-2643

Acceptance date

2017-01-03

Copyright date

2017

Available date

2017-02-24

Publisher version

http://www.sciencedirect.com/science/article/pii/S0019103516303839

Language

en

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