Marley, Mark

Contact Email: mmarley@mail.arc.nasa.gov
Institute: NASA Ames Research Center
First Coauthor: Andrew Ackerman
Institute: NASA Ames Research Center
Subject Area: Brown Dwarfs & Extrasolar Planets
Waveband: Infrared
Technique: Spectroscopy
Presentation: Oral Contribution: Tuesday
Title: Clouds, weather, and the L- to T-dwarf transition
Abstract: We will discuss the results of the application a new eddy sedimentation model for cloud formation in substellar atmospheres to the problem of the L- to T-dwarf transition. We find that a sinking cloud layer, as described by the new model, accounts for the variation in J-K color between the red L-dwarfs and the blue T-dwarfs. The rapidity of the color change may be explained by the appearance of clearings in the silicate cloud deck as it forms ever more deeply in the convective atmosphere with lower effective temperature. Like Jupiter's five-micron hot spots, relatively small holes in the cloud deck can substantially contribute to the disk-averaged flux. Such clearings are likely responsible for the variability obs erved in some late L-dwarfs. We will also discuss the spectral signatures of clouds, chemistry, and the brown dwarf effective temperature scale.