Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007
Imaging and spectroscopy of Neptune's thermal infrared emission is used to assess seasonal changes in Neptune's zonal mean temperatures between Voyager-2 observations (1989, heliocentric longitude Ls=236) and southern summer solstice (2005, Ls=270). Our aim was to analyse imaging and spect...
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ftdatacite:10.48550/arxiv.1311.7570 2023-05-15T18:23:12+02:00 Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007 Fletcher, Leigh N. de Pater, Imke Orton, Glenn S. Hammel, Heidi B. Sitko, Michael L. Irwin, Patrick G. J. 2013 https://dx.doi.org/10.48550/arxiv.1311.7570 https://arxiv.org/abs/1311.7570 unknown arXiv https://dx.doi.org/10.1016/j.icarus.2013.11.035 arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ Earth and Planetary Astrophysics astro-ph.EP FOS Physical sciences article-journal Article ScholarlyArticle Text 2013 ftdatacite https://doi.org/10.48550/arxiv.1311.7570 https://doi.org/10.1016/j.icarus.2013.11.035 2022-04-01T13:15:53Z Imaging and spectroscopy of Neptune's thermal infrared emission is used to assess seasonal changes in Neptune's zonal mean temperatures between Voyager-2 observations (1989, heliocentric longitude Ls=236) and southern summer solstice (2005, Ls=270). Our aim was to analyse imaging and spectroscopy from multiple different sources using a single self-consistent radiative-transfer model to assess the magnitude of seasonal variability. Globally-averaged stratospheric temperatures measured from methane emission tend towards a quasi-isothermal structure (158-164 K) above the 0.1-mbar level, and are found to be consistent with spacecraft observations of AKARI. This remarkable consistency, despite very different observing conditions, suggests that stratospheric temporal variability, if present, is $\pm$5 K at 1 mbar and $\pm$3 K at 0.1 mbar during this solstice period. Conversely, ethane emission is highly variable, with abundance determinations varying by more than a factor of two. The retrieved C2H6 abundances are extremely sensitive to the details of the T(p) derivation. Stratospheric temperatures and ethane are found to be latitudinally uniform away from the south pole (assuming a latitudinally-uniform distribution of stratospheric methane). At low and midlatitudes, comparisons of synthetic Voyager-era images with solstice-era observations suggest that tropospheric zonal temperatures are unchanged since the Voyager 2 encounter, with cool mid-latitudes and a warm equator and pole. A re-analysis of Voyager/IRIS 25-50 μm mapping of tropospheric temperatures and para-hydrogen disequilibrium suggests a symmetric meridional circulation with cold air rising at mid-latitudes (sub-equilibrium para-H2 conditions) and warm air sinking at the equator and poles (super-equilibrium para-H2 conditions). The most significant atmospheric changes are associated with the polar vortex (absent in 1989). : 35 pages, 19 figures. Accepted for publication in Icarus Text South pole DataCite Metadata Store (German National Library of Science and Technology) South Pole |
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Open Polar |
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DataCite Metadata Store (German National Library of Science and Technology) |
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ftdatacite |
language |
unknown |
topic |
Earth and Planetary Astrophysics astro-ph.EP FOS Physical sciences |
spellingShingle |
Earth and Planetary Astrophysics astro-ph.EP FOS Physical sciences Fletcher, Leigh N. de Pater, Imke Orton, Glenn S. Hammel, Heidi B. Sitko, Michael L. Irwin, Patrick G. J. Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007 |
topic_facet |
Earth and Planetary Astrophysics astro-ph.EP FOS Physical sciences |
description |
Imaging and spectroscopy of Neptune's thermal infrared emission is used to assess seasonal changes in Neptune's zonal mean temperatures between Voyager-2 observations (1989, heliocentric longitude Ls=236) and southern summer solstice (2005, Ls=270). Our aim was to analyse imaging and spectroscopy from multiple different sources using a single self-consistent radiative-transfer model to assess the magnitude of seasonal variability. Globally-averaged stratospheric temperatures measured from methane emission tend towards a quasi-isothermal structure (158-164 K) above the 0.1-mbar level, and are found to be consistent with spacecraft observations of AKARI. This remarkable consistency, despite very different observing conditions, suggests that stratospheric temporal variability, if present, is $\pm$5 K at 1 mbar and $\pm$3 K at 0.1 mbar during this solstice period. Conversely, ethane emission is highly variable, with abundance determinations varying by more than a factor of two. The retrieved C2H6 abundances are extremely sensitive to the details of the T(p) derivation. Stratospheric temperatures and ethane are found to be latitudinally uniform away from the south pole (assuming a latitudinally-uniform distribution of stratospheric methane). At low and midlatitudes, comparisons of synthetic Voyager-era images with solstice-era observations suggest that tropospheric zonal temperatures are unchanged since the Voyager 2 encounter, with cool mid-latitudes and a warm equator and pole. A re-analysis of Voyager/IRIS 25-50 μm mapping of tropospheric temperatures and para-hydrogen disequilibrium suggests a symmetric meridional circulation with cold air rising at mid-latitudes (sub-equilibrium para-H2 conditions) and warm air sinking at the equator and poles (super-equilibrium para-H2 conditions). The most significant atmospheric changes are associated with the polar vortex (absent in 1989). : 35 pages, 19 figures. Accepted for publication in Icarus |
format |
Text |
author |
Fletcher, Leigh N. de Pater, Imke Orton, Glenn S. Hammel, Heidi B. Sitko, Michael L. Irwin, Patrick G. J. |
author_facet |
Fletcher, Leigh N. de Pater, Imke Orton, Glenn S. Hammel, Heidi B. Sitko, Michael L. Irwin, Patrick G. J. |
author_sort |
Fletcher, Leigh N. |
title |
Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007 |
title_short |
Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007 |
title_full |
Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007 |
title_fullStr |
Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007 |
title_full_unstemmed |
Neptune at Summer Solstice: Zonal Mean Temperatures from Ground-Based Observations 2003-2007 |
title_sort |
neptune at summer solstice: zonal mean temperatures from ground-based observations 2003-2007 |
publisher |
arXiv |
publishDate |
2013 |
url |
https://dx.doi.org/10.48550/arxiv.1311.7570 https://arxiv.org/abs/1311.7570 |
geographic |
South Pole |
geographic_facet |
South Pole |
genre |
South pole |
genre_facet |
South pole |
op_relation |
https://dx.doi.org/10.1016/j.icarus.2013.11.035 |
op_rights |
arXiv.org perpetual, non-exclusive license http://arxiv.org/licenses/nonexclusive-distrib/1.0/ |
op_doi |
https://doi.org/10.48550/arxiv.1311.7570 https://doi.org/10.1016/j.icarus.2013.11.035 |
_version_ |
1766202737643487232 |