Modeling CO₂ ice clouds with a Mars Global Climate Model

Joachim Audouard (1) , Anni Määttänen (1) , Constantino Listowski (2) , Ehouarn Millour (3) , François Forget (3) , Aymeric Spiga (3)

1 PLANETO - LATMOS
2 BAS - British Antarctic Survey
3 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)

Since the first claimed detection of CO₂ ice clouds by the Mariner campaign (Herr and Pimentel, 1970), more recent observations and modelling works have put new constraints concerning their altitude, region, time and mechanisms of formation (Clancy and Sandor, 1998; Montmessin et al., 2007; Colaprete et al., 2008; Määttänen et al., 2010; Vincendon et al., 2011; Spiga et al. 2012; Listowski et al. 2014). CO₂ clouds are observed at the poles at low altitudes (< 20 km) during the winter and at high altitudes (60-110 km) in the equatorial regions during the first half of the year. However, Martian CO₂ clouds's variability and dynamics remain somehow elusive.Towards an understanding of Martian CO₂ clouds and especially of their precise radiative impact on the climate throughout the history of the planet, including their formation and evolution in a Global Climate Model (GCM) is necessary.Adapting the CO₂ clouds microphysics modeling work of Listowski et al. (2013; 2014), we aim at implementing a complete CO₂ clouds scheme in the GCM of the Laboratoire de Météorologie Dynamique (LMD, Forget et al., 1999). It covers CO₂ microphysics, growth, evolution and dynamics with a methodology inspired from the water ice clouds scheme recently included in the LMD GCM (Navarro et al., 2014).Two main factors control the formation and evolution of CO₂ clouds in the Martian atmosphere: sufficient supersaturation of CO₂ is needed and condensation nuclei must be available. Topography-induced gravity-waves (GW) are expected to propagate to the upper atmosphere where they produce cold pockets of supersaturated CO₂ (Spiga et al., 2012), thus allowing the formation of clouds provided enough condensation nuclei are present. Such supersaturations have been observed by various instruments, in situ (Schofield et al., 1997) and from orbit (Montmessin et al., 2006, 2011; Forget et al., 2009).Using a GW-induced temperature profile and the 1-D version of the GCM, we simulate the formation of CO₂ clouds in the mesosphere and investigate the sensitivity of our microphysics scheme. First results and steps towards the integration in the 3-D GCM will be presented and discussed at the conference.This work is funded by the Laboratory of Excellence ESEP.

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]

Joachim Audouard, Anni Määttänen, Constantino Listowski, Ehouarn Millour, François Forget, et al.. Modeling CO₂ ice clouds with a Mars Global Climate Model. DPS 48 / EPSC 11 (Division for Planetary Sciences and the European Planetary Science Congress), Oct 2016, Pasadena, United States. pp.id.#220.21. ⟨insu-01380332⟩