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Battalio JM, Lora JM, Rafkin S, Soto A. The interaction of deep convection with the general circulation in Titan's atmosphere. Part 2: Impacts on the climate. ICARUS 2022; 373:114623. [PMID: 34916707 PMCID: PMC8670386 DOI: 10.1016/j.icarus.2021.114623] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The impact of methane convection on the circulation of Titan is investigated in the Titan Atmospheric Model (TAM), using a simplified Betts-Miller (SBM) moist convection parameterization scheme. We vary the reference relative humidity (RHSBM ) and relaxation timescale of convection (τ) parameters of the SBM scheme. Titan's atmosphere is mostly insensitive to changes in τ, but convective instability and precipitation are highly impacted by changes in RHSBM . Convection changes behavior from occurring in infrequent (<1 per Titan year), intense events at summer solstice that quickly encompass the entire globe at low RHSBM to near-continuous precipitation at the poles during summer at high RHSBM (>85%). The intermediate regime (RHSBM =70-80%) consists of frequent events (~10 per Titan year) of moderate intensity that are limited in meridional extent to their respective hemisphere. Using results from the Titan Regional Atmospheric Modeling System (TRAMS) and observations, we tune the parameters of the SBM parameterization with optimum values of RH=80% and τ=28800 s. We present a simulated decadal climatology that qualitatively matches observations of Titan's humidity and cloud activity and generally resembles previous results with TAM. Comparing this simulation to one without moist convection demonstrates that convection strengthens the meridional circulation, warms the mid-levels and cools the surface at the poles, and magnifies zonal-mean global moisture anomalies.
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Affiliation(s)
- J Michael Battalio
- Department of Earth and Planetary Sciences, Yale University, 210 Whitney Ave., New Haven, CT 06511
| | - Juan M Lora
- Department of Earth and Planetary Sciences, Yale University, 210 Whitney Ave., New Haven, CT 06511
| | - Scot Rafkin
- Department of Space Studies, Southwest Research Institute, 1050 Walnut St, Suite 300, Boulder, Colorado, USA 80302
| | - Alejandro Soto
- Department of Space Studies, Southwest Research Institute, 1050 Walnut St, Suite 300, Boulder, Colorado, USA 80302
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Battalio JM, Lora JM. Global impacts from high-latitude storms on Titan. GEOPHYSICAL RESEARCH LETTERS 2021; 48:e2021GL094244. [PMID: 34776555 PMCID: PMC8588012 DOI: 10.1029/2021gl094244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Accepted: 09/03/2021] [Indexed: 06/13/2023]
Abstract
One of the first large cloud systems ever observed on Titan was a stationary event at the southern pole that lasted almost two full Titan days. Its stationary nature and large extent are puzzling given that low-level winds should transport clouds eastward, pointing to a mechanism such as atmospheric waves propagating against the mean flow. We use a composite of 47 large convective events across 15 Titan years of simulations from the Titan Atmospheric Model to show that Rossby waves trigger polar convection-which halts the waves and produces stationary precipitation-and then communicate its impact globally. In the aftermath of the convection, forced waves undergo a complicated evolution, including cross-equatorial propagation and tropical-extratropical interaction. The resulting global impact from convection implies its detectability anywhere on Titan, both via surface measurements of pressure and temperature and through remote observation of the outgoing longwave radiation, which increases by ~0.5% globally.
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Affiliation(s)
- J Michael Battalio
- Department of Earth and Planetary Sciences, Yale University, 210 Whitney Ave., New Haven, CT 06511
| | - Juan M Lora
- Department of Earth and Planetary Sciences, Yale University, 210 Whitney Ave., New Haven, CT 06511
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Radebaugh J, Ventra D, Lorenz RD, Farr T, Kirk R, Hayes A, Malaska MJ, Birch S, Liu ZYC, Lunine J, Barnes J, Le Gall A, Lopes R, Stofan E, Wall S, Paillou P. Alluvial and fluvial fans on Saturn's moon Titan reveal processes, materials and regional geology. ACTA ACUST UNITED AC 2016. [DOI: 10.1144/sp440.6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractFans, landforms that record the storage and transport of sediment from uplands to depositional basins, are found on Saturn's moon Titan, a body of significantly different process rates and material compositions from Earth. Images obtained by the Cassini spacecraft's synthetic aperture radar reveal morphologies, roughness, textural patterns and other properties consistent with fan analogues on Earth also viewed by synthetic aperture radar. The observed fan characteristics on Titan reveal some regions of high relative relief and others with gentle slopes over hundreds of kilometres, exposing topographic variations and influences on fan formation. There is evidence for a range of particle sizes across proximal to distal fan regions, from c. 2 cm or more to fine-grained, which can provide details on sedimentary processes. Some features are best described as alluvial fans, which implies their proximity to high-relief source areas, while others are more likely to be fluvial fans, drawing from larger catchment areas and frequently characterized by more prolonged runoff events. The presence of fans corroborates the vast liquid storage capacity of the atmosphere and the resultant episodic behaviour. Fans join the growing list of landforms on Titan derived from atmospheric and fluvial processes similar to those on Earth, strengthening comparisons between these two planetary bodies.
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Affiliation(s)
- Jani Radebaugh
- Brigham Young University, S-389 ESC, Provo, UT 84601, USA
| | | | - Ralph D. Lorenz
- Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA
| | - Tom Farr
- NASA Jet Propulsion Laboratory, Pasadena, CA 91109, USA
| | - Randy Kirk
- US Geological Survey, Astrogeology Division, Flagstaff AZ 86001, USA
| | - Alex Hayes
- Department of Astronomy, Cornell University, Ithaca, NY 14853, USA
| | | | - Sam Birch
- Department of Astronomy, Cornell University, Ithaca, NY 14853, USA
| | - Zac Yung-Chun Liu
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
| | - Jonathan Lunine
- Department of Astronomy, Cornell University, Ithaca, NY 14853, USA
| | - Jason Barnes
- Department of Physics, University of Idaho, Moscow, ID 83844, USA
| | - Alice Le Gall
- LATMOS Observatoire de Versailles Saint-Quentin-en-Yvelines (OVSQ), Paris, France
| | - Rosaly Lopes
- NASA Jet Propulsion Laboratory, Pasadena, CA 91109, USA
| | | | - Steve Wall
- NASA Jet Propulsion Laboratory, Pasadena, CA 91109, USA
| | - Philippe Paillou
- Observatoire Aquitain des Sciences de l'Univers, Universite de Bordeaux, Floirac, France
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Li L. Dimming titan revealed by the Cassini observations. Sci Rep 2015; 5:8239. [PMID: 25649341 PMCID: PMC4316193 DOI: 10.1038/srep08239] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 01/12/2015] [Indexed: 11/10/2022] Open
Abstract
Here we report the temporal variation of Titan's emitted energy with the Cassini/CIRS observations. In the northern hemisphere, the hemispheric-average emitted power decreased from 2007 to 2009 and increased from 2009 to 2012-13, which make the net change insignificant (0.1 ± 0.2%) during the period 2007-2013. The decrease from 2007 to 2009 is mainly due to the cooling around the stratospause, and the increase from 2009 to 2012-13 is probably related to temporal variation of atmospheric temperature around the tropopuase in the northern hemisphere. In the southern hemisphere, the emitted power continuously decreased by 5.0 ± 0.6% from 2.40 ± 0.01 W/m(2) in 2007 to 2.28 ± 0.01 in 2012-13, which is mainly related to Titan's seasonal variation. The asymmetry in the temporal variation between the two hemispheres results in the global-average emitted power decreasing by 2.5 ± 0.6% from 2.41 ± 0.01 W/m(2) in 2007 to 2.35 ± 0.01 W/m(2) in 2012-13. The solar constant at Titan decreased by ~13.0% in the same period 2007-2013, which is much stronger than the temporal variation of emitted power. The measurements of Titan's absorbed solar power are needed to determine the temporal variation of the global energy budget.
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Affiliation(s)
- Liming Li
- Department of Physics, University of Houston, Houston, TX 77204, USA
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Barnes JW, Buratti BJ, Turtle EP, Bow J, Dalba PA, Perry J, Brown RH, Rodriguez S, Mouélic SL, Baines KH, Sotin C, Lorenz RD, Malaska MJ, McCord TB, Clark RN, Jaumann R, Hayne PO, Nicholson PD, Soderblom JM, Soderblom LA. Precipitation-induced surface brightenings seen on Titan by Cassini VIMS and ISS. ACTA ACUST UNITED AC 2013. [DOI: 10.1186/2191-2521-2-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Schneider T, Graves SDB, Schaller EL, Brown ME. Polar methane accumulation and rainstorms on Titan from simulations of the methane cycle. Nature 2012; 481:58-61. [PMID: 22222747 DOI: 10.1038/nature10666] [Citation(s) in RCA: 103] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 10/20/2011] [Indexed: 11/09/2022]
Abstract
Titan has a methane cycle akin to Earth's water cycle. It has lakes in polar regions, preferentially in the north; dry low latitudes with fluvial features and occasional rainstorms; and tropospheric clouds mainly (so far) in southern middle latitudes and polar regions. Previous models have explained the low-latitude dryness as a result of atmospheric methane transport into middle and high latitudes. Hitherto, no model has explained why lakes are found only in polar regions and preferentially in the north; how low-latitude rainstorms arise; or why clouds cluster in southern middle and high latitudes. Here we report simulations with a three-dimensional atmospheric model coupled to a dynamic surface reservoir of methane. We find that methane is cold-trapped and accumulates in polar regions, preferentially in the north because the northern summer, at aphelion, is longer and has greater net precipitation than the southern summer. The net precipitation in polar regions is balanced in the annual mean by slow along-surface methane transport towards mid-latitudes, and subsequent evaporation. In low latitudes, rare but intense storms occur around the equinoxes, producing enough precipitation to carve surface features. Tropospheric clouds form primarily in middle and high latitudes of the summer hemisphere, which until recently has been the southern hemisphere. We predict that in the northern polar region, prominent clouds will form within about two (Earth) years and lake levels will rise over the next fifteen years.
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Affiliation(s)
- T Schneider
- California Institute of Technology, Pasadena, California 91125, USA.
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Clark RN, Curchin JM, Barnes JW, Jaumann R, Soderblom L, Cruikshank DP, Brown RH, Rodriguez S, Lunine J, Stephan K, Hoefen TM, Le Mouélic S, Sotin C, Baines KH, Buratti BJ, Nicholson PD. Detection and mapping of hydrocarbon deposits on Titan. ACTA ACUST UNITED AC 2010. [DOI: 10.1029/2009je003369] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
Methane clouds, lakes and most fluvial features on Saturn's moon Titan have been observed in the moist high latitudes, while the tropics have been nearly devoid of convective clouds and have shown an abundance of wind-carved surface features like dunes. The presence of small-scale channels and dry riverbeds near the equator observed by the Huygens probe at latitudes thought incapable of supporting convection (and thus strong rain) has been suggested to be due to geological seepage or other mechanisms not related to precipitation. Here we report the presence of bright, transient, tropospheric clouds in tropical latitudes. We find that the initial pulse of cloud activity generated planetary waves that instigated cloud activity at other latitudes across Titan that had been cloud-free for at least several years. These observations show that convective pulses at one latitude can trigger short-term convection at other latitudes, even those not generally considered capable of supporting convection, and may also explain the presence of methane-carved rivers and channels near the Huygens landing site.
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Global circulation as the main source of cloud activity on Titan. Nature 2009; 459:678-82. [DOI: 10.1038/nature08014] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Accepted: 03/23/2009] [Indexed: 11/08/2022]
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Tokano T. The dynamics of Titan's troposphere. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:633-648. [PMID: 19019782 DOI: 10.1098/rsta.2008.0163] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
While the Voyager mission could essentially not reveal the dynamics of Titan's troposphere, useful information was obtained by the Cassini spacecraft and, particularly, by the Huygens probe that landed on Titan's surface; this information can be interpreted by means of numerical models of atmospheric circulation. The meridional circulation is likely to consist of a large Hadley circulation asymmetric about the equator, but is susceptible to disruption by turbulence in clouds. The zonal wind in the troposphere is comparable to or even weaker than that in the terrestrial troposphere and contains zones of easterlies, much in contrast to the super-rotating stratosphere. Unique to Titan is the transition from a geostrophic to cyclostrophic wind balance in the upper troposphere. While Earth-like storm systems associated with baroclinic instability are absent, Saturn's gravitational tide introduces a planetary wave of wavenumber 2 and a periodical variation in the wind direction in the troposphere. Unlike on Earth, the wind over the equatorial surface is westerly. The seasonal reversal in the Hadley circulation sense and zonal wind direction is predicted to have a substantial influence on the formation of dunes as well as variation of Titan's rotation rate and length of day.
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Affiliation(s)
- Tetsuya Tokano
- Institut für Geophysik und Meteorologie, Universität zu Köln, Albertus-Magnus-Platz, 50923 Köln, Germany.
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Lebonnois S, Rannou P, Hourdin F. The coupling of winds, aerosols and chemistry in Titan's atmosphere. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:665-682. [PMID: 19073461 DOI: 10.1098/rsta.2008.0243] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
The atmosphere of Titan is a complex system, where thermal structure, radiative transfer, dynamics, microphysics and photochemistry are strongly coupled together. The global climate model developed over the past 15 years at the Pierre-Simon Laplace Institute has been exploring these different couplings, and has demonstrated how they can help to interpret the observed atmospheric structure of Titan's lower atmosphere (mainly in the stratosphere and troposphere). This review discusses these interactions, and our current understanding of their role in the context of this model, but also of other available works. The recent Cassini results, and the importance of the production mechanisms for Titan's haze, have put forward the need to explore the mesosphere and the couplings between upper and lower atmosphere, as well as the current limits of available models.
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Affiliation(s)
- Sebastien Lebonnois
- Laboratoire de Meteorologie Dynamique, IPSL, UPMC/CNRS, 4 place Jussieu, Box 99, 75252 Paris Cedex 05, France.
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13
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Griffith CA. Storms, polar deposits and the methane cycle in Titan's atmosphere. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:713-728. [PMID: 19073459 DOI: 10.1098/rsta.2008.0245] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
In Titan's atmosphere, the second most abundant constituent, methane, exists as a gas, liquid and solid, and cycles between the atmosphere and the surface. Similar to the Earth's hydrological cycle, Titan sports clouds, rain and lakes. Yet, Titan's cycle differs dramatically from its terrestrial counterpart, and reveals the workings of weather in an atmosphere that is 10 times thicker than the Earth's atmosphere, that is two orders of magnitude less illuminated, and that involves a different condensable. While ongoing measurements by the Cassini-Huygens mission are revealing the intricacies of the moon's weather, circulation, lake coverage and geology, knowledge is still limited by the paucity of observations. This review of Titan's methane cycle therefore focuses on measured characteristics of the lower atmosphere and surface that appear particularly perplexing or alien.
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Affiliation(s)
- Caitlin Ann Griffith
- Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721, USA.
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14
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Tobie G, Choukroun M, Grasset O, Le Mouélic S, Lunine JI, Sotin C, Bourgeois O, Gautier D, Hirtzig M, Lebonnois S, Le Corre L. Evolution of Titan and implications for its hydrocarbon cycle. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2009; 367:617-631. [PMID: 19073458 DOI: 10.1098/rsta.2008.0246] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Measurements of the carbon and nitrogen isotopic ratios as well as the detection of 40Ar and 36Ar by the gas chromatograph mass spectrometer (GCMS) instrument on board the Huygens probe have provided key constraints on the origin and evolution of Titan's atmosphere, and indirectly on the evolution of its interior. Those data combined with models of Titan's interior can be used to determine the story of volatile outgassing since Titan's formation. In the absence of an internal source, methane, which is irreversibly photodissociated in Titan's stratosphere, should be removed entirely from the atmosphere in a time-span of a few tens of millions of years. The episodic destabilization of methane clathrate reservoir stored within Titan's crust and subsequent methane outgassing could explain the present atmospheric abundance of methane, as well as the presence of argon in the atmosphere. The idea that methane is released from the interior through eruptive processes is also supported by the observations of several cryovolcanic-like features on Titan's surface by the mapping spectrometer (VIMS) and the radar on board Cassini. Thermal instabilities within the icy crust, possibly favoured by the presence of ammonia, may explain the observed features and provide the conditions for eruption of methane and other volatiles. Episodic resurfacing events associated with thermal and compositional instabilities in the icy crust can have major consequences on the hydrocarbon budget on Titan's surface and atmosphere.
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Affiliation(s)
- G Tobie
- Laboratoire de Planétologie et Géodynamique de Nantes, Université Nantes Atlantique, 2, rue de la Houssinière, 44322 Nantes Cedex 03, France CNRS, UMR-6112, 2, rue de la Houssinière, 44322 Nantes Cedex 03, France.
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15
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Mitchell JL. The drying of Titan's dunes: Titan's methane hydrology and its impact on atmospheric circulation. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2007je003017] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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16
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Abstract
Precipitation is expected in Titan's atmosphere, yet it has not been directly observed, and the geographical regions where rain occurs are unknown. Here we present near-infrared spectra from the Very Large Telescope and W. M. Keck Observatories that reveal an enhancement of opacity in Titan's troposphere on the morning side of the leading hemisphere. Retrieved extinction profiles are consistent with condensed methane in clouds at an altitude near 30 kilometers and concomitant methane drizzle below. The moisture encompasses the equatorial region over Titan's brightest continent, Xanadu. Diurnal temperature gradients that cause variations in methane relative humidity, winds, and topography may each be a contributing factor to the condensation mechanism. The clouds and precipitation are optically thin at 2.0 micrometers, and models of "subvisible" clouds suggest that the droplets are 0.1 millimeter or larger.
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Affiliation(s)
- Máté Adámkovics
- Department of Astronomy, University of California, Berkeley, CA 94611, USA.
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17
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Negrão A, Hirtzig M, Coustenis A, Gendron E, Drossart P, Rannou P, Combes M, Boudon V. The 2-μm spectroscopy of Huygens probe landing site on Titan with Very Large Telescope/Nasmyth Adaptive Optics System Near-Infrared Imager and Spectrograph. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2005je002651] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Hirtzig M, Coustenis A, Gendron E, Drossart P, Hartung M, Negrão A, Rannou P, Combes M. Titan: Atmospheric and surface features as observed with Nasmyth Adaptive Optics System Near-Infrared Imager and Spectrograph at the time of the Huygens mission. ACTA ACUST UNITED AC 2007. [DOI: 10.1029/2005je002650] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Mitchell JL, Pierrehumbert RT, Frierson DMW, Caballero R. The dynamics behind Titan's methane clouds. Proc Natl Acad Sci U S A 2006; 103:18421-6. [PMID: 17121992 PMCID: PMC1693680 DOI: 10.1073/pnas.0605074103] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We present results of an axisymmetric global circulation model of Titan with a simplified suite of atmospheric physics forced by seasonally varying insolation. The recent discovery of midlatitude tropospheric clouds on Titan has caused much excitement about the roles of surface sources of methane and the global circulation in forming clouds. Although localized surface sources, such as methane geysers or "cryovolcanoes," have been invoked to explain these clouds, we find in this work that clouds appear in regions of convergence by the mean meridional circulation and over the poles during solstices, where the solar forcing reaches its seasonal maximum. Other regions are inhibited from forming clouds because of dynamical transports of methane and strong subsidence. We find that for a variety of moist regimes, i.e., with the effect of methane thermodynamics included, the observed cloud features can be explained by the large-scale dynamics of the atmosphere. Clouds at the solsticial pole are found to be a robust feature of Titan's dynamics, whereas isolated midlatitude clouds are present exclusively in a variety of moist dynamical regimes. In all cases, even without including methane thermodynamics, our model ceases to produce polar clouds approximately 4-6 terrestrial years after solstices.
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Affiliation(s)
- Jonathan L Mitchell
- Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA.
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Perron JT, Lamb MP, Koven CD, Fung IY, Yager E, Ádámkovics M. Valley formation and methane precipitation rates on Titan. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005je002602] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Affiliation(s)
- F M Flasar
- Planetary Systems Laboratory, NASA Goddard Spaceflight Center, Greenbelt, MD 20771, USA.
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22
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Griffith CA, Penteado P, Rannou P, Brown R, Boudon V, Baines KH, Clark R, Drossart P, Buratti B, Nicholson P, McKay CP, Coustenis A, Negrao A, Jaumann R. Evidence for a Polar Ethane Cloud on Titan. Science 2006; 313:1620-2. [PMID: 16973876 DOI: 10.1126/science.1128245] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Spectra from Cassini's Visual and Infrared Mapping Spectrometer reveal the presence of a vast tropospheric cloud on Titan at latitudes 51 degrees to 68 degrees north and all longitudes observed (10 degrees to 190 degrees west). The derived characteristics indicate that this cloud is composed of ethane and forms as a result of stratospheric subsidence and the particularly cool conditions near the moon's north pole. Preferential condensation of ethane, perhaps as ice, at Titan's poles during the winters may partially explain the lack of liquid ethane oceans on Titan's surface at middle and lower latitudes.
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Affiliation(s)
- C A Griffith
- Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ, 85721 USA
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Hueso R, Sánchez-Lavega A. Methane storms on Saturn's moon Titan. Nature 2006; 442:428-31. [PMID: 16871212 DOI: 10.1038/nature04933] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Accepted: 05/23/2006] [Indexed: 11/09/2022]
Abstract
The presence of dry fluvial river channels and the intense cloud activity in the south pole of Titan over the past few years suggest the presence of methane rain. The nitrogen atmosphere of Titan therefore appears to support a methane meteorological cycle that sculptures the surface and controls its properties. Titan and Earth are the only worlds in the Solar System where rain reaches the surface, although the atmospheric cycles of water and methane are expected to be very different. Here we report three-dimensional dynamical calculations showing that severe methane convective storms accompanied by intense precipitation may occur in Titan under the right environmental conditions. The strongest storms grow when the methane relative humidity in the middle troposphere is above 80 per cent, producing updrafts with maximum velocities of 20 m s(-1), able to reach altitudes of 30 km before dissipating in 5-8 h. Raindrops of 1-5 mm in radius produce precipitation rainfalls on the surface as high as 110 kg m(-2) and are comparable to flash flood events on Earth.
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Affiliation(s)
- R Hueso
- Departamento de Física Aplicada I, ETS Ingenieros, Universidad del País Vasco, Alameda Urquijo s/n, 48013 Bilbao, Spain.
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Tokano T, McKay CP, Neubauer FM, Atreya SK, Ferri F, Fulchignoni M, Niemann HB. Methane drizzle on Titan. Nature 2006; 442:432-5. [PMID: 16871213 DOI: 10.1038/nature04948] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Accepted: 06/06/2006] [Indexed: 11/08/2022]
Abstract
Saturn's moon Titan shows landscapes with fluvial features suggestive of hydrology based on liquid methane. Recent efforts in understanding Titan's methane hydrological cycle have focused on occasional cloud outbursts near the south pole or cloud streaks at southern mid-latitudes and the mechanisms of their formation. It is not known, however, if the clouds produce rain or if there are also non-convective clouds, as predicted by several models. Here we show that the in situ data on the methane concentration and temperature profile in Titan's troposphere point to the presence of layered optically thin stratiform clouds. The data indicate an upper methane ice cloud and a lower, barely visible, liquid methane-nitrogen cloud, with a gap in between. The lower, liquid, cloud produces drizzle that reaches the surface. These non-convective methane clouds are quasi-permanent features supported by the global atmospheric circulation, indicating that methane precipitation occurs wherever there is slow upward motion. This drizzle is a persistent component of Titan's methane hydrological cycle and, by wetting the surface on a global scale, plays an active role in the surface geology of Titan.
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Affiliation(s)
- Tetsuya Tokano
- Institut für Geophysik und Meteorologie, Universität zu Köln, Albertus-Magnus-Platz, 50923 Köln, Germany.
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Rannou P, Montmessin F, Hourdin F, Lebonnois S. The latitudinal distribution of clouds on Titan. Science 2006; 311:201-5. [PMID: 16410519 DOI: 10.1126/science.1118424] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Clouds have been observed recently on Titan, through the thick haze, using near-infrared spectroscopy and images near the south pole and in temperate regions near 40 degrees S. Recent telescope and Cassini orbiter observations are now providing an insight into cloud climatology. To study clouds, we have developed a general circulation model of Titan that includes cloud microphysics. We identify and explain the formation of several types of ethane and methane clouds, including south polar clouds and sporadic clouds in temperate regions and especially at 40 degrees in the summer hemisphere. The locations, frequencies, and composition of these cloud types are essentially explained by the large-scale circulation.
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Affiliation(s)
- P Rannou
- Service d'Aéronomie, Institut Pierre Simon Laplace, Université de Versailles-St-Quentin, BP3, 91371 Verrières le Buisson, France.
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Lamb MP, Howard AD, Johnson J, Whipple KX, Dietrich WE, Perron JT. Can springs cut canyons into rock? ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005je002663] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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de Pater I, Ádámkovics M, Bouchez AH, Brown ME, Gibbard SG, Marchis F, Roe HG, Schaller EL, Young E. Titan imagery with Keck adaptive optics during and after probe entry. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2005je002620] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Tokano T, Ferri F, Colombatti G, Mäkinen T, Fulchignoni M. Titan's planetary boundary layer structure at the Huygens landing site. ACTA ACUST UNITED AC 2006. [DOI: 10.1029/2006je002704] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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