JP6.11 The climate and seasonal cycle on Titan: atmospheric dynamics and methane cycle

Thursday, 11 June 2009
Stowe Room (Stoweflake Resort and Confernce Center)
Sonja D.B. Graves, California Institute of Technology, Pasadena, CA; and T. Schneider and E. L. Schaller

Titan has a complex and largely unknown climate system. Methane, near its triple point on Titan as water is on Earth, can exist as liquid, gas, or solid on Titan's surface. There is evidence for methane clouds, lakes, and riverbeds, suggesting methane may cycle between Titan's atmosphere and surface in some fashion as water does on Earth. But what dynamic mechanisms maintain Titan's climate and cause its variability is largely unknown.  The Voyager and Cassini spacecrafts, as well as ground-based observations, have given us fascinating hints of what role methane plays in shaping Titan's surface and atmospheric dynamics.  Here we use a 3-dimensional global climate model (GCM) of Titan's atmosphere to elucidate the observed seasonal cycle on Titan. In the GCM, the atmosphere interacts with a variable surface reservoir of liquid methane.  We use this model to investigate how Titan's climate and methane cycle may be maintained, how they vary seasonally, and how they influence observed surface features. We show that Titan's atmosphere most likely contains eddy-driven circulation cells embedded in large-scale Hadley cells, a configuration unlike any other known planetary circulation. The circulation undergoes rapid seasonal transitions, which cause rapid dislocations of convection zones, consistent with the locations at which clouds have been observed on Titan.
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