Global climate modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds

Abstract

Water ice clouds play a key role in the radiative transfer of the Martian atmosphere, impacting its thermal structure, its circulation, and, in turn, the water cycle. Recent studies including the radiative effects of clouds in global climate models (GCMs) have found that the corresponding feedbacks amplify the model defaults. In particular, it prevents models with simple microphysics from reproducing even the basic characteristics of the water cycle. Within that context, we propose a new implementation of the water cycle in GCMs, including a detailed cloud microphysics taking into account nucleation on dust particles, ice particle growth, and scavenging of dust particles due to the condensation of ice. We implement these new methods in the Laboratoire de Météorologie Dynamique GCM and find satisfying agreement with the Thermal Emission Spectrometer observations of both water vapor and cloud opacities, with a significant improvement when compared to GCMs taking into account radiative effects of water ice clouds without this implementation. However, a lack of water vapor in the tropics after Ls = 180° is persistent in simulations compared to observations, as a consequence of aphelion cloud radiative effects strengthening the Hadley cell. Our improvements also allow us to explore questions raised by recent observations of the Martian atmosphere. Supersaturation above the hygropause is predicted in line with Spectroscopy for Investigation of Characteristics of the Atmosphere of Mars observations. The model also suggests for the first time that the scavenging of dust by water ice clouds alone fails to fully account for the detached dust layers observed by the Mars Climate Sounder.

The physics of Martian weather and climate: a review

“…This combination allows improvements to be made in the calculations of nucleation, growth and sedimentation, while keeping the computing time low when calculating global transport. A combined scheme such as this has been used in a mesoscale model to study mountain-induced vertical transport of water (Michaels et al 2006), and in a GCM to study equatorial water ice deposits (Nelli et al 2009), clouds and fogs observed by Phoenix (Nelli et al 2010) and the complete hydrological cycle with radiatively active clouds (Navarro et al 2014). The results of such simulations match well with available spacecraft data.…”

Mars: a small terrestrial planet

“…Following analyses by Haberle et al (1999) and Colaprete et al (1999), new models (Hinson and Wilson 2004;Madeleine et al 2012) have considered the radiative effect of these clouds, which in some cases can generate temperature inversions. A further improved 3D GCM model has been developed by Navarro et al (2014), including the nucleation on dust particles, ice particle growth in a supersaturated atmosphere, and scavenging of dust particles due to ice condensation. This study illustrates the importance of microphysics in the modeling of the water cycle.…”

“…9). (Navarro et al 2014) and observed by the TES instrument aboard MGS. Top water vapor column density; bottom cloud opacity.…”

“…Top water vapor column density; bottom cloud opacity. The figure is taken from Navarro et al (2014) Detection and abundance of CO Among the minor atmospheric species (H 2 O apart), carbon monoxide, CO, was the only one to be unambiguously detected from the ground, first through its near-infrared transitions (Kaplan et al 1969), then in the millimeter range (Kakar et al 1977). Since its early ground-based detection in the millimeter range, CO has been used to infer and monitor the thermal structure of Mars; the (1-0) and (2-1) lines of 12 CO and 13 CO were used to simultaneously retrieve the thermal profile and the CO mixing ratio (Clancy et al 1996).…”

“…Indeed, CO and O are formed from the photo-dissociation of CO 2 (Maltagliati et al 2011). Bottom GCM predictions (from Navarro et al 2014) but the inverse reaction…”