P087-04
Investigating changes in dust particles size in the Martian atmosphere during Global Dust Storms with the NASA Ames Mars Global Climate Model
Wednesday, 16 December 2020: 19:21
Virtual
Tanguy Bertrand1, Melinda A Kahre1, Robert John Wilson1, Michael J Wolff2, Robert Michael Haberle3, Franck Montmessin4, Richard A Urata1, Victoria Hartwick5, Alexandre Kling6, Amanda S Brecht1, Kathryn Steakley7 and Courtney Batterson8, (1)NASA Ames Research Center, Moffett Field, CA, United States, (2)Space Science Institute, Boulder, CO, United States, (3)NASA Ames Res Ctr, Moffett Field, CA, United States, (4)LATMOS Laboratoire Atmosphères, Observations Spatiales, UVSQ Université Paris-Saclay, Sorbonne université, CNRS, Paris, France, (5)University of Colorado, Boulder, CO, United States, (6)Universities Space Research Association Moffett Field, Moffett Field, CA, United States, (7)New Mexico State University Main Campus, Astronomy, Las Cruces, NM, United States, (8)NASA Ames Research Center, Mountain View, CA, United States
Abstract:
The 2018 Global Dust Storm (GDS) has been observed on Mars from the surface and from orbit. Here we focus on the surface temperatures measured locally by REMS/MSL in Gale crater and column dust IR opacities observed globally by Mars Climate Sounder on-board Mars Reconnaissance Orbiter (MCS/MRO) (e.g. Montabone et al., 2020). Recent modeling efforts of the 2018 GDS highlight that climate models do not simultaneously capture both the evolution of surface temperatures and the decay rate of global column dust opacities, which suggests that significant changes in dust particle sizes may occur during the dust storm (e.g. Bertrand et al., 2020, Montabone et al., 2020). These models typically assume a constant lifted dust particle size distribution—with size evolution occurring in the atmosphere but only because of gravitational sedimentation. For instance, simulations with sufficiently large particles sizes to yield reasonable decay/sedimentation rates also provide excessive radiation fluxes at the surface, with excessive surface temperatures during peak dust loading.
Here we use the NASA Ames Global Climate Model to investigate in 1D and in 3D possible processes leading to temporal and spatial changes of dust particle sizes during GDSs, in particular Brownian coagulation (production of large particles by the collisions induced by Brownian motions of the particles in the gas and subsequent sticking together of small particles), gravitational coagulation (accretion through sedimentation, Murphy et al., 1990, Jacobsen et al., 1999, Montmessin et al., 2002, Fedorova et al., 2014) and changes in the lifted particle size at the surface due to different active reservoirs or to depletion of small particles as the storm increases in intensity. We build our investigation upon the previous modeling of the GDS performed with a uniform lifted effective particle radius (Bertrand et al., 2020). We show how these mechanisms impact the particle size distribution during the GDSs, the surface temperature and the dust “greenhouse” effect, the evolution and the decay phase of the storm, and explore what possible scenarios could reconcile the different observations.
