Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle

Schneider, Tapio; Graves, S. D.; Schaller, E. L.; Brown, Michael E.

doi:10.1038/nature10666

Cited by 119 publications

(144 citation statements)

References 40 publications

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“…The tropical annual-mean precipitation minus evaporation (P − E) pattern exhibits net evaporation in the region around the equator and net precipitation in the subtropics. This pattern is reversed to modern conditions, while a similar pattern has been reported for Titan Schneider et al, 2012). The pattern robustly emerges in Snowball simulations (Abbot et al, 2013) and results from the rapid seasonal transitions of the Hadley circulation, which imply that the ascent region in which precipitation outweighs evaporation is almost always located several degrees off the equator.…”

Section: Impact Of the Hadley Circulation Strength On The Tropical Hymentioning

confidence: 51%

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

Voigt

2013

Earth Syst. Dynam.

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Abstract. I study the Hadley circulation of a completely icecovered Snowball Earth through simulations with a comprehensive atmosphere general circulation model. Because the Snowball Earth atmosphere is an example of a dry atmosphere, these simulations allow me to test to what extent dry theories and idealized models capture the dynamics of realistic dry Hadley circulations. Perpetual off-equatorial as well as seasonally varying insolation is used, extending a previous study for perpetual on-equatorial (equinox) insolation. Vertical diffusion of momentum, representing the momentum transport of dry convection, is fundamental to the momentum budgets of both the winter and summer cells. In the zonal budget, it is the primary process balancing the Coriolis force. In the meridional budget, it mixes meridional momentum between the upper and the lower branch and thereby decelerates the circulation. Because of the latter, the circulation intensifies by a factor of three when vertical diffusion of momentum is suppressed. For seasonally varying insolation, the circulation undergoes rapid transitions from the weak summer into the strong winter regime. Consistent with previous studies in idealized models, these transitions result from a mean-flow feedback, because of which they are insensitive to the treatment of vertical diffusion of momentum. Overall, the results corroborate previous findings for perpetual on-equatorial insolation. They demonstrate that descriptions of realistic dry Hadley circulations, in particular their strength, need to incorporate the vertical momentum transport by dry convection, a process that is neglected in most dry theories and idealized models. An improved estimate of the strength of the Snowball Earth Hadley circulation will also help to better constrain the climate of a possible Neoproterozoic Snowball Earth and its deglaciation threshold.

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Section: Impact Of the Hadley Circulation Strength On The Tropical Hymentioning

confidence: 51%

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

Voigt

2013

Earth Syst. Dynam.

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“…This range of precipitation rates encompasses the expected range on Titan (up to 1.2 -1.3 m/Eyr during the rainy season (Schneider et al, 2012)). It also covers the precipitation range between arid and tropical climates on Earth.…”

Section: Comparison Between Titan and The Earth Over Terrestrial Timementioning

confidence: 99%

“…It also covers the precipitation range between arid and tropical climates on Earth. This comparison is illustrated in Figures 3 (for hydrocarbons and carbon dioxide ice) and 4 (for nitriles and water ice), for which we fixed Titan's temperature to 91.5 K (the surface temperature during the rainy season according to Schneider et al (2012)) and Earth's temperature to 298.15 K (with a partial pressure of carbon dioxide equal to 0.33 matm).…”

Section: Comparison Between Titan and The Earth Over Terrestrial Timementioning

confidence: 99%

“…Section 5.1 is dedicated to the comparative study of denudation rates of pure solid organics in pure liquid methane, ethane and propane, and of common soluble minerals (halite, gypsum, anhydrite, calcite and dolomite), cornerstones of karstic landscapes development on Earth, in liquid water over terrestrial timescales. Section 5.2 describes the computation of denudation rates of pure solids and of mixed organic surface layers in liquid methane over Titan timescales by using the methane precipitation rates extracted from the GCM of Schneider et al (2012). Based on these denudation rates, we compute the timescales needed to develop the typical 100 m-deep topographic depressions observed in the polar regions of Titan (Section 6) and compare them to timescales estimated from other observations (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Dissolution on Titan and on Earth: Toward the age of Titan's karstic landscapes

et al. 2015

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Titan's polar surface is dotted with hundreds of lacustrine depressions. Based on the hypothesis that they are karstic in origin, we aim at determining the efficiency of surface dissolution as a landshaping process on Titan, in a comparative planetology perspective with the Earth as reference. Our approach is based on the calculation of solutional denudation rates and allow inference of formation timescales for topographic depressions developed by chemical erosion on both planetary bodies. The model depends on the solubility of solids in liquids, the density of solids and liquids, and the average annual net rainfall rates. We compute and compare the denudation rates of pure solid organics in liquid hydrocarbons and of minerals in liquid water over Titan and Earth timescales. We then investigate the denudation rates of a superficial organic layer in liquid methane over one Titan year. At this timescale, such a layer on Titan would behave like salts or carbonates on Earth depending on its composition, which means that dissolution processes would likely occur, but would be 30 times slower on Titan compared to the Earth due to the seasonality of precipitation. Assuming an average depth of 100 m for Titan's lacustrine depressions, these could have developed in a few tens of millions of years at polar latitudes higher than 70 • N and S, and a few hundreds of million years at lower polar latitudes. The ages determined are consistent with the youth of the surface (< 1 Gyr) and the repartition of dissolution-related landforms on Titan.

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“…Precipitation can return methane to the surface (Turtle et al, 2009 where fluid transport has some role in closing the hydrological cycle. Seasonal variations in the general circulation (Mitchell et al, 2009) as well as predictions of the locations and frequency of clouds Preprint submitted to Icarus September 30, 2015 (Schneider et al, 2012) depend on the distribution of methane near the surface, both in the regolith and the lower atmosphere. Lakes and seas of liquid hydrocarbons (Stofan et al, 2007) provide both sinks and sources of methane on the surface.…”

Section: Introductionmentioning

confidence: 99%

Meridional variation in tropospheric methane on Titan observed with AO spectroscopy at Keck and VLT

Ádámkovics

Mitchell

Hayes

et al. 2016

Icarus

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The spatial distribution of the tropospheric methane on Titan was measured using near-infrared spectroscopy. Ground-based observations at 1.5 µm (H-band) were performed during the same night using instruments with adaptive optics at both the W. M. Keck Observatory and at the Paranal Observatory on 17 July 2014 UT. The integral field observations with SINFONI on the VLT covered the entire H-band at moderate resolving power, R = λ/∆λ ≈ 1, 500, while the Keck observations were performed with NIRSPAO near 1.5525 µm at higher resolution, R ≈ 25, 000. The moderate resolution observations are used for flux calibration and for the determination of model parameters that can be degenerate in the interpretation of high resolution spectra. Line-by-line calculations of CH 4 and CH 3 D correlated k distributions from the HITRAN 2012 database were used, which incorporate revised line assignments near 1.5 µm. We fit the surface albedo and aerosol distributions in the VLT SINFONI observations that cover the entire H-band window and used these quantities to constrain the models of the high-resolution Keck NIRSPAO spectra when retrieving the methane abundances. Cassini VIMS images of the polar regions, acquired on 20 July 2014 UT, are used to validate the assumption that the opacity of tropospheric aerosol is relatively uniform below 10 km. We retrieved methane abundances at latitudes between 42 • S and 80 • N. The tropospheric methane in the Southern mid-latitudes was enhanced by a factor of ∼10-40% over the nominal profile that was measured using the GCMS on Huygens. The Northern hemisphere had ∼90% of the nominal methane abundance up to polar latitudes (80 • N). These measurements suggest that a source of saturated polar air is equilibrating with dryer conditions at lower latitudes.

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Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle

Cited by 119 publications

References 40 publications

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

The dynamics of the Snowball Earth Hadley circulation for off-equatorial and seasonally varying insolation

Dissolution on Titan and on Earth: Toward the age of Titan's karstic landscapes

Meridional variation in tropospheric methane on Titan observed with AO spectroscopy at Keck and VLT

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