Titan atmosphere database

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Abstract

We have developed in the last decade a two-dimensional version of the Titan global circulation model LMDZ. This model accounts for multiple coupling occuring on Titan between dynamics, haze, chemistry and radiative transfer. It was successful at explaining many observed features related to atmosphere state (wind, temperature), haze structure and chemical species distributions, recently, an important step in our knowledge about Titan has been done with Cassini and Huygens visits to Titan. In this context, we want to make the results of our model available for the scientific community which is involved in the study of Titan. Such a tool should be useful to give a global frame (spatial and time behaviour of physical quantities) for interpreting ground based telescope observations.

Section snippets

Coupled haze-chemistry-circulation model

Up to the middle of the last decade, Titan was investigated through its different systems separately; circulation, haze, chemistry, aeronomy and so on. However, it became obvious that all these components of Titan climate were interacting together, and so was the conclusions of many papers at this time (e.g, Hourdin et al., 1995, Hutzell et al., 1993, Rannou et al., 1997). The first serious attempt to couple circulation and haze is to be credited to Hutzell et al. (1996). However, no feedback

Motivation for a database

The model was fixed to match several important results derived from observations, as temperature meridional profiles at 1 and 0.4 mbar retrieved from IRIS observation (Flasar and Conrath, 1990, Coustenis and Bézard, 1995), temperature vertical profile (Lellouch et al., 1989), zonal winds at 0.25 mbar (Hubbard et al., 1993), haze distribution at Voyager time (Smith et al., 1981, Smith et al., 1982, Rages and Pollack, 1983), related photometry (Sromovsky et al., 1981, Neff et al., 1984, Courtin et

The database on the web

We have chosen to write the codes of the database in Fortran 77. However, in principle, C routines are able to call Fortran 77 routine with minor adaptations. The “database” is composed of an ASCII file containing 49 × 55 × 32 values for each of the 31 fields. This database file is roughly 27 MB. Series of codes which read and make interpolations inside the database is also available. Finally two codes (interfaces) show how to call the database and display its results. A first code is a simple

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Cited by (36)

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    While most trace stratospheric gases in the north polar data generally show only a small decreasing trend until 2014, the southern polar results on the contrary point to a strong enhancement after 2012 (Coustenis et al., 2016, 2018). As argued also by other investigators (e.g. Vinatier et al., 2015; Teanby et al., 2017), this indicates a fast and strong buildup of the gases in the southern pole while it goes deeper into the shadow during the 2013–2014 southern autumn, as predicted by models (e.g. Hourdin et al., 2004; Rannou et al., 2005; Lebonnois et al., 2009, 2012). This was associated with temperature changes we have registered in our previous publications where from 2013 until 2016, the northern polar region has shown a temperature increase of 10 K, while the south has shown a more significant decrease (up to 25 K) in a similar period of time.

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    The model reproduces the thermal structure observed in the troposphere and stratosphere, the abundance and vertical profiles of most chemical compounds in the stratosphere, and their enrichment in the winter polar region. A reference simulation may be found on the web (Rannou et al., 2005), and a review of the interactions between haze, dynamics and composition may be found in Lebonnois et al. (2009). This 2-dimensional climate model uses a specific parametrization to take into account the horizontal mixing by barotropic waves, which were obtained in the 3-dimensional GCM of Hourdin et al. (1995) but could not be present in the 2-dimensional reduction of the model.

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