Revised ab initio models for H2–H2 collision-induced absorption at low temperatures

Orton, Glenn S.; Gustafsson, Magnus; Burgdorf, M.; Meadows, Victoria

doi:10.1016/j.icarus.2007.02.003

Cited by 49 publications

(84 citation statements)

References 16 publications

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“…The collision-induced continuum shaping Neptune's thermal-IR spectrum used H 2 -H 2 opacities from Orton et al (2007), who updated the calculations of Borysow et al (1985) for the low temperatures of the ice giants, plus additional H 2 -He, H 2 -CH 4 and CH 4 -CH 4 opacities from Borysow et al (1988); Frommhold (1986, 1987). Furthermore, M. Gustafsson (pers.…”

Section: Radiative Transfer Modellingmentioning

confidence: 99%

“…VLT/VISIR (2006): Thermal images were obtained by ESO's Very Large Telescope (VLT) UT-3 (Melipal) mid-infrared camera/spectrometer (VISIR, Lagage et al, 2004) in September 2006, and presented by Orton et al (2007). In this analysis we use an 18.7-µm image from 01:44-03:47 UT on September 2, 2006; and images at 17.6 µm (01:55-03:13 UT), 8.6 µm (06:53-07:40 UT) and 12.3 µm (03:16-03:36 UT) from September 3, 2006.…”

Section: Sources Of Imaging Datamentioning

confidence: 99%

“…In this analysis we use an 18.7-µm image from 01:44-03:47 UT on September 2, 2006; and images at 17.6 µm (01:55-03:13 UT), 8.6 µm (06:53-07:40 UT) and 12.3 µm (03:16-03:36 UT) from September 3, 2006. The data reduction and calibration are described in Orton et al (2007). Each image used a different standard star (Cohen et al, 1999).…”

Section: Sources Of Imaging Datamentioning

confidence: 99%

“…Each image used a different standard star (Cohen et al, 1999). Although Orton et al (2007) have already provided a detailed comparison of the VISIR results to the Voyager/IRIS temperature retrievals, we repeat the analysis here to ensure consistency between all available datasets.…”

Section: Sources Of Imaging Datamentioning

confidence: 99%

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Neptune at summer solstice: Zonal mean temperatures from ground-based observations, 2003–2007

Fletcher

Pater²,

Orton

et al. 2014

Icarus

108

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• ). 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 < ±5 K at 1 mbar and < ±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 (from 500 to 1200 ppb at 1 mbar). The retrieved C 2 H 6 abundances are extremely sensitive to the details of the T (p) derivation, although the underlying cause of the variable ethane emission remains unidentified. Stratospheric temperatures and ethane are found to be latitudinally uniform away from the south pole (assuming a latitudinally-uniform distribution of stratospheric methane), with no large seasonal hemispheric asymmetries evident at solstice. At low and mid-latitudes, 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 (a tracer for vertical motions) suggests a symmetric meridional circulation with cold air rising at mid-latitudes (sub-equilibrium para-H 2 conditions) and warm air sinking at the equator and poles (super-equilibrium para-H 2 conditions). The most significant atmospheric changes have occurred at high southern latitudes, where zonal temperatures retrieved from 2003 images suggest a polar enhancement of 7-8 K above the tropopause, and an increase of 5-6 K throughout the 70 − 90• S region between 0.1 and 200 mbar. Such a large perturbation, if present in 1989, would have been detectable by Voyager/IRIS in a single scan despite its long-wavelength sensitivity, and we conclude that Neptune's south polar cyclonic vortex increased in strength significantly from Voyager to solstice.

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Section: Radiative Transfer Modellingmentioning

confidence: 99%

Section: Sources Of Imaging Datamentioning

confidence: 99%

Section: Sources Of Imaging Datamentioning

confidence: 99%

Section: Sources Of Imaging Datamentioning

confidence: 99%

See 2 more Smart Citations

Neptune at summer solstice: Zonal mean temperatures from ground-based observations, 2003–2007

Fletcher

Pater²,

Orton

et al. 2014

Icarus

108

View full text Add to dashboard Cite

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“…The model includes atmospheric opacities of the three measured HD lines (see Table 2) and collision-induced absorption of H 2 -H 2 (Borysow et al 1985), H 2 -He (Borysow et al 1988), H 2 -CH 4 (Borysow & Frommhold 1986) and CH 4 -CH 4 (Borysow & Frommhold 1987). Orton et al (2007) updated the H 2 -H 2 coefficients of Borysow et al (1985), but the modifications to far-infrared absorption were insignificant.…”

Section: Analysis Of the D/h Ratiomentioning

confidence: 99%

The D/H ratio in the atmospheres of Uranus and Neptune fromHerschel-PACS observations

Feuchtgruber¹,

Lellouch²,

Orton³

et al. 2013

A&A

110

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Herschel-PACS measurements of the rotational R(0) and R(1) HD lines in the atmospheres of Uranus and Neptune are analyzed to derive a D/H ratio with improved precision for the two planets. The derivation of the D/H ratio also includes previous measurements of the R(2) line with the Short Wavelength Spectrometer on board the Infrared Space Observatory (ISO). The available spectroscopic line information of the three rotational transitions is discussed and applied in the radiative transfer calculations. The best simultaneous fit of all three lines requires only a minor departure from the Spitzer temperature profile of Uranus and a departure limited to 2K from the Voyager temperature profile of Neptune (each time around the tropopause). The resulting and remarkably similar D/H ratios for Uranus and Neptune are found to be (4.4 ± 0.4) × 10 −5 and (4.1 ± 0.4) × 10 −5 , respectively. Although the deuterium enrichment in the two atmospheres compared to the protosolar value is confirmed, it is found to be lower compared to previous analyses. Using interior models from the literature and assuming that complete mixing of the atmosphere and interior occured during the planets' history, we derive a D/H in protoplanetary ices between (5.75-7.0) × 10 −5 for Uranus and between (5.1-7.7) × 10 −5 for Neptune. Conversely, adopting a cometary D/H for the protoplanetary ices between (15-30) × 10 −5 , we constrain the interior models of the two planets to have an ice mass fraction of 14-32%, i.e., the two planets are rock-dominated.

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Ice Giant Circulation Patterns: Implications for Atmospheric Probes

et al. 2020

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Atmospheric circulation patterns derived from multi-spectral remote sensing can serve as a guide for choosing a suitable entry location for a future in situ probe mission to the Ice Giants. Since the Voyager-2 flybys in the 1980s, three decades of observations from ground- and space-based observatories have generated a picture of Ice Giant circulation that is complex, perplexing, and altogether unlike that seen on the Gas Giants. This review seeks to reconcile the various competing circulation patterns from an observational perspective, accounting for spatially-resolved measurements of: zonal albedo contrasts and banded appearances; cloud-tracked zonal winds; temperature and para-H2 measurements above the condensate clouds; and equator-to-pole contrasts in condensable volatiles (methane, ammonia, and hydrogen sulphide) in the deeper troposphere. These observations identify three distinct latitude domains: an equatorial domain of deep upwelling and upper-tropospheric subsidence, potentially bounded by peaks in the retrograde zonal jet and analogous to Jovian cyclonic belts; a mid-latitude transitional domain of upper-tropospheric upwelling, vigorous cloud activity, analogous to Jovian anticyclonic zones; and a polar domain of strong subsidence, volatile depletion, and small-scale (and potentially seasonally-variable) convective activity. Taken together, the multi-wavelength observations suggest a tiered structure of stacked circulation cells (at least two in the troposphere and one in the stratosphere), potentially separated in the vertical by (i) strong molecular weight gradients associated with cloud condensation, and by (ii) transitions from a thermally-direct circulation regime at depth to a wave- and radiative-driven circulation regime at high altitude. The inferred circulation can be tested in the coming decade by 3D numerical simulations of the atmosphere, and by observations from future world-class facilities. The carrier spacecraft for any probe entry mission must ultimately carry a suite of remote-sensing instruments capable of fully constraining the atmospheric motions at the probe descent location.

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Revised ab initio models for H2–H2 collision-induced absorption at low temperatures

Cited by 49 publications

References 16 publications

Neptune at summer solstice: Zonal mean temperatures from ground-based observations, 2003–2007

Neptune at summer solstice: Zonal mean temperatures from ground-based observations, 2003–2007

The D/H ratio in the atmospheres of Uranus and Neptune fromHerschel-PACS observations

Ice Giant Circulation Patterns: Implications for Atmospheric Probes

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