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

• Published in: Journal of geophysical research. Planets 2014-07, Vol.119 (7), p.1479-1495
• Main Authors: Navarro, T., Madeleine, J.-B, Forget, F., Spiga, A., Millour, E., Montmessin, F., Määttänen, A.
• Format: Article
• Language: English
• Subjects: Amplification; Astrophysics; Atmosphere; Atmospheric and Oceanic Physics; Atmospheric circulation; Atmospheric models; Atmospheric water; Atmospheric water vapor; climate; Climate models; Cloud microphysics; Clouds; Computer simulation; Condensation; Detaching; Dust; Dust particles; Earth and Planetary Astrophysics; Emission spectroscopy; Geophysics; Global climate; global climate model; Global climate models; Hydrologic cycle; Hygropause; Ice; Ice clouds; Mars; Mars atmosphere; Mars climate; Mathematical models; Microphysics; Nucleation; Physics; Radiative transfer; Scavenging; Sciences of the Universe; Spectroscopy; Supersaturation; Thermal emission; Tropical environments; water; Water ice; Water vapor
• ISSN: 2169-9097; 2169-9100
• DOI: 10.1002/2013JE004550

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. Key Points Radiatively active clouds impact atmospheric water vapor and ice in a GCMCloud microphysics with dynamic nuclei is needed in GCMs