Multispectral imaging observations of Neptune’s cloud structure with Gemini-North

Irwin, Patrick; Teanby, N. A.; Davis, G. R.; Fletcher, Leigh N.; Orton, Glenn S.; Tice, D.; Hurley, J.; Calcutt, S. B.

doi:10.1016/j.icarus.2011.08.005

Cited by 31 publications

(59 citation statements)

References 55 publications

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“…We immediately note that atmospheric features tend to be distributed preferentially along bands of constant latitude, with increased prevalence at mid-latitudes, in agreement with previous observations (e.g. Sromovsky et al 2001b;Max et al 2003;Irwin et al 2011;Martin et al 2012). In addition to clouds at roughly the same latitudes as Martin et al (2012), we observe clouds at ∼40 • N. In all images there is an absence of cloud features just south of the equator, in agreement with previous observations (e.g.…”

Section: Observations and Data Reductionsupporting

confidence: 92%

“…We expect these differences to be related to the limitations of our data (we only have broadband measurements, not spectra), differences in the sensitivity of our measurements to different altitudes (for example, Gibbard et al (2003) measures mostly in K'-band, which is not sensitive to altitudes as deep as those we probe in H-band), and the simplicity of our model -previous studies have favored models with a more complicated haze structure and which vary other model parameters (e.g. Baines & Smith 1990;Gibbard et al 2002;Irwin et al 2011;Karkoschka & Tomasko 2011;Luszcz-Cook 2012). Our finding that equatorial features are deepest, while the SPFs in the south are found above them (∼0.3 bar), is different from the results of Gibbard et al (2003), which suggest a trend of increasing altitude with latitude from south to north.…”

Section: Cloud Feature Pressures From Radiative Transfer Modelingmentioning

confidence: 99%

“…Irwin et al 2011). This particle size distribution is analogous to that found on Titan (Mitchell et al 2011).…”

Section: Cloud Feature Pressures From Radiative Transfer Modelingmentioning

confidence: 99%

“…The extinction cross section and Henyey-Greenstein asymmetry parameter of the scattering are calculated using Mie theory. We assume that the particles have a scale height that is 0.1 times the gas scale height, corresponding to physically thin cloud layers (Irwin et al 2011). The free parameters in the model are the number density of cloud particles at the bottom (maximum) pressure of the haze/cloud, and the altitude (pressure) of the cloud.…”

Section: Cloud Feature Pressures From Radiative Transfer Modelingmentioning

confidence: 99%

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Dispersion in Neptune’s zonal wind velocities from NIR Keck AO observations in July 2009

Fitzpatrick

Pater

Luszcz‐Cook

et al. 2013

Astrophys Space Sci

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We report observations of Neptune made in H-(1.4-1.8 µm) and K'-(2.0-2.4 µm) bands on 14 and 16 July 2009 from the 10-m W.M. Keck II Telescope using the near-infrared camera NIRC2 coupled to the Adaptive Optics (AO) system. We track the positions of 54 bright atmospheric features over a few hours to derive their zonal and latitudinal velocities, and perform radiative transfer modeling to measure the cloud-top pressures of 50 features seen simultaneously in both bands.We observe one South Polar Feature (SPF) on 14 July and three SPFs on 16 July at ∼65 • S. The SPFs observed on both nights are different features, consistent with the high variability of Neptune's storms.There is significant dispersion in Neptune's zonal wind velocities about the smooth Voyager wind profile fit of Sromovsky et al., Icarus 105, 140 (1993), much greater than the upper limit we expect from vertical wind shear, with the largest dispersion seen at equatorial and southern mid-latitudes. Comparison of feature pressures vs. residuals in zonal velocity from the smooth Voyager wind profile also directly reveals the dominance of mechanisms over vertical wind shear in causing dispersion in the zonal winds.Vertical wind shear is not the primary cause of the difference in dispersion and deviation in zonal veloc-

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Section: Observations and Data Reductionsupporting

confidence: 92%

Section: Cloud Feature Pressures From Radiative Transfer Modelingmentioning

confidence: 99%

“…Irwin et al 2011). This particle size distribution is analogous to that found on Titan (Mitchell et al 2011).…”

Section: Cloud Feature Pressures From Radiative Transfer Modelingmentioning

confidence: 99%

Section: Cloud Feature Pressures From Radiative Transfer Modelingmentioning

confidence: 99%

See 2 more Smart Citations

Dispersion in Neptune’s zonal wind velocities from NIR Keck AO observations in July 2009

Fitzpatrick

Pater

Luszcz‐Cook

et al. 2013

Astrophys Space Sci

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“…Neptune's Email address: fletcher@atm.ox.ac.uk (Leigh N. Fletcher) complex meteorology is driven by a balance between its intrinsic luminosity and absorption of sunlight by methane and aerosols in the upper troposphere. Visible and near-infrared imaging of Neptune from Voyager (Smith et al, 1989;Karkoschka, 2011), the Hubble Space Telescope (Sromovsky et al, 1995;Hammel et al, 1995;Sromovsky et al, 2001;Karkoschka and Tomasko, 2011), and ground-based observatories (Roddier et al, 1998;Max et al, 2003;Gibbard et al, 2002Gibbard et al, , 2003Luszcz-Cook et al, 2010;Irwin et al, 2011), have shown the planet to be dynamically active despite its large distance from the Sun. Unlike Uranus, with its unusual inclination and negligible internal heat source (e.g., Pearl and Conrath, 1991), Neptune's weather layer exhibits rapidly varying cloud activity, zonal banding, dark ovals and sporadic orographic clouds.…”

Section: Introductionmentioning

confidence: 99%

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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Dynamics and clouds in planetary atmospheres from telescopic observations

Sánchez-Lavega,

Irwin,

García Muñoz

2023

Astron Astrophys Rev

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This review presents an insight into our current knowledge of the atmospheres of the planets Venus, Mars, Jupiter, Saturn, Uranus and Neptune, the satellite Titan, and those of exoplanets. It deals with the thermal structure, aerosol properties (hazes and clouds, dust in the case of Mars), chemical composition, global winds, and selected dynamical phenomena in these objects. Our understanding of atmospheres is greatly benefitting from the discovery in the last 3 decades of thousands of exoplanets. The exoplanet properties span a broad range of conditions, and it is fair to expect as much variety for their atmospheres. This complexity is driving unprecedented investigations of the atmospheres, where those of the solar systems bodies are the obvious reference. We are witnessing a significant transfer of knowledge in both directions between the investigations dedicated to Solar System and exoplanet atmospheres, and there are reasons to think that this exchange will intensity in the future. We identify and select a list of research subjects that can be conducted at optical and infrared wavelengths with future and currently available ground-based and space-based telescopes, but excluding those from the space missions to solar system bodies.

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Multispectral imaging observations of Neptune’s cloud structure with Gemini-North

Cited by 31 publications

References 55 publications

Dispersion in Neptune’s zonal wind velocities from NIR Keck AO observations in July 2009

Dispersion in Neptune’s zonal wind velocities from NIR Keck AO observations in July 2009

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

Dynamics and clouds in planetary atmospheres from telescopic observations

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