Radiation And Dynamics In Titan's Atmosphere: Investigations Of Titan's Present And Past Climate

Persistent Link:
http://hdl.handle.net/10150/332763
Title:
Radiation And Dynamics In Titan's Atmosphere: Investigations Of Titan's Present And Past Climate
Author:
Lora, Juan Manuel
Issue Date:
2014
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This dissertation explores the coupling between radiative and three-dimensional dynamical processes in the atmosphere of Titan, and their impact on the seasonal climate and recent paleoclimate. First, a simple calculation is used to demonstrate the atmospheric attenuation on the distribution of insolation. The maximum diurnal-mean surface insolation does not reach the polar regions in summertime, and this impacts both surface temperatures and their destabilizing effect on the atmosphere. Second, a detailed two-stream, fully non-gray radiative transfer model, written specifically for Titan but with high flexibility, is used to calculate radiative fluxes and the associated heating rates. This model reproduces Titan's temperature structure from the surface through the stratopause, over nearly six decades of pressure. Additionally, a physics parameterizations package is developed for Titan, in part based on similar methods from Earth atmospheric models, for use in a Titan general circulation model (GCM). Simulations with this model, including Titan's methane cycle, reproduce two important observational constraints---Titan's temperature profile and atmospheric superrotation---that have proven difficult to satisfy simultaneously for previous models. Simulations with the observed distribution of seas are used to examine the resulting distribution of cloud activity, atmospheric humidity, and temperatures, and show that these are consistent with dry mid- and low-latitudes, while the observed polar temperatures are reproduced as a consequence of evaporative cooling. Analysis of the surface energy budget shows that turbulent fluxes react to the surface insolation, confirming the importance of its distribution. Finally, the GCM is used to simulate Titan's climate during snapshots over the past 42 kyr that capture the amplitude range of variations in eccentricity and longitude of perihelion. The results show that the atmosphere is largely insensitive to orbital forcing, and that it invariably transports methane poleward, suggesting Titan's low-latitudes have been deserts for at least hundreds of thousands of years. In detail, seasonal asymmetries do affect the distribution of methane, moving methane to the pole with the weaker summer, though orbital variations do not imply a long-period asymmetry. If the timescale for the atmosphere to transport the surface liquid reservoir is sufficiently short, this explains the observed north-south dichotomy of lakes and seas.
Type:
text; Electronic Dissertation
Keywords:
Hydrological Cycle; Planetary Atmospheres; Planetary Science; Radiative Transfer; Titan; Planetary Sciences; Atmospheric Circulation
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Planetary Sciences
Degree Grantor:
University of Arizona
Advisor:
Russell, Joellen L.; Lunine, Jonathan I.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen
dc.titleRadiation And Dynamics In Titan's Atmosphere: Investigations Of Titan's Present And Past Climateen_US
dc.creatorLora, Juan Manuelen_US
dc.contributor.authorLora, Juan Manuelen_US
dc.date.issued2014-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis dissertation explores the coupling between radiative and three-dimensional dynamical processes in the atmosphere of Titan, and their impact on the seasonal climate and recent paleoclimate. First, a simple calculation is used to demonstrate the atmospheric attenuation on the distribution of insolation. The maximum diurnal-mean surface insolation does not reach the polar regions in summertime, and this impacts both surface temperatures and their destabilizing effect on the atmosphere. Second, a detailed two-stream, fully non-gray radiative transfer model, written specifically for Titan but with high flexibility, is used to calculate radiative fluxes and the associated heating rates. This model reproduces Titan's temperature structure from the surface through the stratopause, over nearly six decades of pressure. Additionally, a physics parameterizations package is developed for Titan, in part based on similar methods from Earth atmospheric models, for use in a Titan general circulation model (GCM). Simulations with this model, including Titan's methane cycle, reproduce two important observational constraints---Titan's temperature profile and atmospheric superrotation---that have proven difficult to satisfy simultaneously for previous models. Simulations with the observed distribution of seas are used to examine the resulting distribution of cloud activity, atmospheric humidity, and temperatures, and show that these are consistent with dry mid- and low-latitudes, while the observed polar temperatures are reproduced as a consequence of evaporative cooling. Analysis of the surface energy budget shows that turbulent fluxes react to the surface insolation, confirming the importance of its distribution. Finally, the GCM is used to simulate Titan's climate during snapshots over the past 42 kyr that capture the amplitude range of variations in eccentricity and longitude of perihelion. The results show that the atmosphere is largely insensitive to orbital forcing, and that it invariably transports methane poleward, suggesting Titan's low-latitudes have been deserts for at least hundreds of thousands of years. In detail, seasonal asymmetries do affect the distribution of methane, moving methane to the pole with the weaker summer, though orbital variations do not imply a long-period asymmetry. If the timescale for the atmosphere to transport the surface liquid reservoir is sufficiently short, this explains the observed north-south dichotomy of lakes and seas.en_US
dc.typetexten
dc.typeElectronic Dissertationen
dc.subjectHydrological Cycleen_US
dc.subjectPlanetary Atmospheresen_US
dc.subjectPlanetary Scienceen_US
dc.subjectRadiative Transferen_US
dc.subjectTitanen_US
dc.subjectPlanetary Sciencesen_US
dc.subjectAtmospheric Circulationen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePlanetary Sciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRussell, Joellen L.en_US
dc.contributor.advisorLunine, Jonathan I.en_US
dc.contributor.committeememberRussell, Joellen L.en_US
dc.contributor.committeememberLunine, Jonathan I.en_US
dc.contributor.committeememberGriffith, Caitlin A.en_US
dc.contributor.committeememberHubbard, William B.en_US
dc.contributor.committeememberShowman, Adam P.en_US
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