Meteorological assessment of the surface temperatures on Titan: constraints on the surface type

Tokano, Tetsuya

doi:10.1016/j.icarus.2004.08.019

Cited by 89 publications

(87 citation statements)

References 53 publications

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“…Our measurements are compared in Figure 1 with predictions from Tokano (2005). That study used a three-dimensional general circulation model (GCM) of the surface and lower atmosphere to derive surface temperatures as a function of latitude over a Titan year.…”

Section: Resultsmentioning

confidence: 99%

Surface Temperatures on Titan During Northern Winter and Spring

Jennings

Cottini

Nixon

et al. 2016

ApJL

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Meridional brightness temperatures were measured on the surface of Titan during the 2004-2014 portion of the Cassini mission by the Composite Infrared Spectrometer. Temperatures mapped from pole to pole during five twoyear periods show a marked seasonal dependence. The surface temperature near the south pole over this time decreased by 2 K from 91.7±0.3 to 89.7±0.5 K while at the north pole the temperature increased by 1 K from 90.7±0.5 to 91.5±0.2 K. The latitude of maximum temperature moved from 19 S to 16 N, tracking the subsolar latitude. As the latitude changed, the maximum temperature remained constant at 93.65±0.15 K. In 2010 our temperatures repeated the north-south symmetry seen by Voyager one Titan year earlier in 1980. Early in the mission, temperatures at all latitudes had agreed with GCM predictions, but by 2014 temperatures in the north were lower than modeled by 1 K. The temperature rise in the north may be delayed by cooling of sea surfaces and moist ground brought on by seasonal methane precipitation and evaporation.

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Section: Resultsmentioning

confidence: 99%

Surface Temperatures on Titan During Northern Winter and Spring

Jennings

Cottini

Nixon

et al. 2016

ApJL

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“…While clouds may be more numerous (Mitchell et al 2006), we find that convection however is still very weak with a CAPE∼160 J kg Ϫ1 and LNB p 26 km, in agreement with Barth & Rafkin (2007) yet not (Tokano et al 2006b) as a result of differing lapse rates (Appendix B). An increase in the surface temperature by 2 K (larger than predicted by GCM models [Tokano 2005]) would also initiate surface convection, but again does not change the CAPE significantly from that of Titan's current atmosphere. Only variations in Titan's humidity below 9 km strongly affect its stability (Barth & Rafkin 2007;Hueso & Sánchez-Lavega 2006).…”

mentioning

confidence: 89%

Titan's Tropical Storms in an Evolving Atmosphere

Griffith

McKay

Ferri

2008

ApJ

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The Huygens probe landed in a damp lake bed fed by fluvial channels, indicative of past rainfall. Such washes, interspersed with vast dunes, are typical of Titan's tropical landscape. Yet, Cassini-Huygens measurements reveal a highly stable tropical atmosphere devoid of deep convective storms, and the formation of washes in dune fields is not understood. Here we examine the effects of seasonal variations in humidity, surface heating, and dynamical forcing on the stability of Titan's troposphere. We find that during the probe landing, the middle troposphere was weakly unstable to convection, consistent with the tenuous cloud detected at 21 km. Yet the tropical atmosphere, at any season, is too stable to produce deep convective storms. Convection in the tropics remains weak and confined to altitudes below ∼30 km, unless the humidity is increased below 9 km altitude. Solar heating is insufficient to significantly humidify the tropical atmosphere. The large polar lakes are seasonably stable, and the methane column abundance measured by Huygens typical of the tropical atmosphere. Our study indicates the presence of distinct polar and equatorial climates. It also suggests that fluvial features in the tropics do not result from recent seasonal rainstorms, and thereby supports other origins such as geological seepage, cryovolcanism, or a wetter climate in the past.

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“…The surface temperature evolves according to the surface energy balance of a homogenous slab with heat capacity 2.5 × 10 5 J m −2 K −1 (similar to that of a porous icy regolith 47 ) , with temperature tendencies balanced by insolation, thermal radiative fluxes, and the surface fluxes of sensible heat and latent heat (methane evaporation). The value of the slab heat capacity does not substantially affect our results, as long as it is much smaller than the heat capacity of the atmosphere (∼ 10 8 J m −2 K −1 ).…”

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confidence: 99%

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

Schneider

Graves

Schaller³

et al. 2012

Nature

125

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Supplementary InformationOur GCM is based on the Flexible Modeling System of the Geophysical Fluid Dynamics Laboratory (http://fms.gfdl.noaa.gov). It is similar to standard models for Earth's atmosphere, but with Titan's radius, planetary rotation rate, material properties, and seasonally varying insolation, and with a methane cycle instead of a water cycle. The GCM has similarities to the models in refs. 16, 17, but unlike those, it is 3D and eddy-resolving and has a different representation of radiative transfer and surface processes.Resolution. The GCM solves the hydrostatic primitive equations in vorticity-divergence form, using the spectral transform method in the horizontal and finite differences in the vertical 31 . The horizontal spectral resolution is T21 (corresponding to about 5 • × 5 • resolution of the transform grid). The vertical coordinate is σ = p/p s (pressure p normalized by surface pressure p s ); it is discretized with 18 unequally spaced levels 32 . The top of the model is at σ = 0; the uppermost full level has a mean pressure of 15 mbar (altitude ∼90 km). The time-stepping scheme is a semiimplicit leapfrog scheme (timestep 1600 s).

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Meteorological assessment of the surface temperatures on Titan: constraints on the surface type

Cited by 89 publications

References 53 publications

Surface Temperatures on Titan During Northern Winter and Spring

Surface Temperatures on Titan During Northern Winter and Spring

Titan's Tropical Storms in an Evolving Atmosphere

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

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