Effects of Latent Heating on Atmospheres of Brown Dwarfs and Directly Imaged Planets
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Univ Arizona, Dept Planetary SciUniv Arizona, Lunar & Planetary Lab
Issue Date
2017-01-30Keywords
brown dwarfshydrodynamics
methods: numerical
planets and satellites: atmospheres planets
planets and satellites: gaseous planets
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IOP PUBLISHING LTDCitation
Effects of Latent Heating on Atmospheres of Brown Dwarfs and Directly Imaged Planets 2017, 835 (2):186 The Astrophysical JournalJournal
The Astrophysical JournalRights
© 2017. The American Astronomical Society. All rights reserved.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
The growing number of observations of brown dwarfs (BDs) has provided evidence for strong atmospheric circulation on these objects. Directly imaged planets share similar observations and can be viewed as low-gravity versions of BDs. Vigorous condensate cycles of chemical species in their atmospheres are inferred by observations and theoretical studies, and latent heating associated with condensation is expected to be important in shaping atmospheric circulation and influencing cloud patchiness. We present a qualitative description of the mechanisms by which condensational latent heating influences circulation, and then illustrate them using an idealized general circulation model that includes a condensation cycle of silicates with latent heating and molecular weight effect due to the rainout of the condensate. Simulations with conditions appropriate for typical T dwarfs exhibit the development of localized storms and east-west jets. The storms are spatially inhomogeneous, evolving on a timescale of hours to days and extending vertically from the condensation level to the tropopause. The fractional area of the BD covered by active storms is small. Based on a simple analytic model, we quantitatively explain the area fraction of moist plumes and show its dependence on the radiative timescale and convective available potential energy (CAPE). We predict that if latent heating dominates cloud formation processes, the fractional coverage area of clouds decreases as the spectral type goes through the L/T transition from high to lower effective temperature. This is a natural consequence of the variation of the radiative timescale and CAPE with the spectral type.ISSN
1538-4357Version
Final published versionSponsors
NASA Headquarters; NSF [AST 1313444]Additional Links
http://stacks.iop.org/0004-637X/835/i=2/a=186?key=crossref.f25d934647027d830dc12e90bf85b348ae974a485f413a2113503eed53cd6c53
10.3847/1538-4357/835/2/186
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