Titan's Methane Weather

Abstract

Conditions in Titan's troposphere are near the triple point of methane, the second most abundant component of its atmosphere. Our understanding of Titan's lower atmosphere has shifted considerably in the past decade. Ground-based observations, Hubble Space Telescope images, and data returned from the Cassini and Huygens spacecraft show that Titan's troposphere hosts a methane-based meteorology in direct analogy to the waterbased meteorology of Earth. What once was thought to be a quiescent place, lacking in clouds or localized weather and changing only subtly on long seasonal timescales, is now understood to be a dynamic system with significant weather events regularly occurring against the backdrop of dramatic seasonal changes. Although the observational record of Titan's weather covers only a third of its 30-year seasonal cycle, Titan's atmospheric processes appear to be more closely analogous to those of Earth than to those of any other object in our solar system. 355 Annu. Rev. Earth Planet. Sci. 2012.40:355-382. Downloaded from www.annualreviews.org by NORTH CAROLINA STATE UNIVERSITY on 10/02/12. For personal use only.

Titan's atmosphere and climate

“…The level of free convection (LFC) is around 9 km and the level of neutral buoyancy (LNB) is around 24 km [ Griffith et al , ]. Many of the observed clouds that form and dissipate on short time scales are at altitudes near the LNB [ Griffith et al , , , ; Ádámkovics et al , ] indicating that they are convective [ Griffith et al , , ; Roe , ]. Interestingly, the clouds at higher latitudes also reach higher altitudes (up to 40 km), potentially indicating that the methane humidity profile varies latitudinally [ Griffith et al , , ; Ádámkovics et al , ; Griffith et al , ] as discussed in section 2.2.…”

“…Large cloud systems (covering up to ∼10% of the disk) seem to occur every 3 to 18 months [ Roe , ]. These large storms are capable of triggering Rossby waves, which result in formation of clouds elsewhere in the atmosphere [ Schaller et al , ].…”

Meridional variation in tropospheric methane on Titan observed with AO spectroscopy at Keck and VLT

“…Methane (CH 4 ) is the most abundant condensible species on Titan, dominates the energy transport through the atmosphere (Mitchell, 2012), and is part of a complex hydrological cycle (Atreya et al, 2006;Roe, 2012). Clouds of methane can indicate regions of convection (e.g., Griffith et al, 2005), polar subsidence , or evaporation from lakes (e.g., $ Accepted for publication on May 22, 2015 Email address: mate@berkeley.edu (MátéÁdámkovics) URL: http://astro.berkeley.edu/~madamkov (MátéÁdámkovics) Brown et al, 2009;Turtle et al, 2009), while the formation of large scale methane cloud systems are diagnostic of atmospheric dynamics via their morphology (Mitchell et al, 2011) and how they evolve with time (Ádámkovics et al, 2010;Turtle et al, 2011a).…”

Gas-phase broadband spectroscopy using active sources: progress, status, and applications [Invited]

“…The atmospheric composition and chemistry of solar system planets [69] and moons [70, 71] is of interest for understanding planetary formation and can be used to track planetary geophysical processes (e.g., see [72–75]). While it is possible to study these atmospheres using earth-based telescopes, more precise information can often be obtained with in situ measurements [76].…”