Observations made in Gale Crater by instruments on the MSL Curiosity Rover show that the diurnal amplitude of the surface pressure is increased and the depth of the Convective Boundary Layer (CBL) is decreased relative to other lander locations on flatter regions of Mars (Haberle et al., 2014; Moores et al., 2015). Mesoscale modeling studies of Gale Crater suggest that crater circulations produce these effects. Tyler & Barnes (2013) show that local upslope/downslope flows along the crater rim and Mt. Sharp amplify the diurnal pressure cycle. These same flows are thought to be at least partly responsible for the suppression of the CBL because upward air flow at the rim and in the center (due to Mt. Sharp) forces subsidence over the lowest regions of the crater during the day. Regional flows, largely due to the location of Gale near the dichotomy boundary, may also play a role in shaping the circulation internal to the crater. Whether the behavior of the CBL and the amplified diurnal pressure cycle are phenomena observed in craters morphologically different from Gale (i.e. bowl-shaped, irregular, degraded) is not yet understood. We will explore these questions by characterizing the behavior of these processes as they are shaped by the morphology of craters greater than 100 km in diameter. We use the NASA Ames Mars Global Circulation Model (GCM) that now utilizes the NOAA/GFDL cubed-sphere finite-volume dynamical core to examine ~100 craters of varying size and shape from a database of known Martian craters (Robbins & Hynek, 2014). Run at 7.5 km resolution, the GCM is capable of resolving surface winds, temperature, and pressure inside craters of this size allowing for the analysis of dozens of craters simulated at various seasons and within the context of synoptic and global-scale phenomena.

The B storm is an annually recurring, regional-scale dust storm that occurs over the south pole of Mars during southern summer solstice season during years lacking a global dust storm [1]. The B storm begins just after perihelion (Ls = 251°), reaches peak strength around southern summer solstice (Ls = 270°), and decays through ~Ls = 290° [2]. The B storm is associated with mid-level atmospheric warming in which 50 Pa (2.5 scale heights) temperatures increase to over 200 K. Mid-level dust concentrations more than triple during the B storm, exceeding 4 ppm throughout the duration of the storm and exceeding 10 ppm at peak strength (Ls = 270°) [1,2]. Our observational analysis, which was presented at AGU in 2020, shows that elevated dust concentrations (> 4 ppm) and associated warming (> 200 K) are observable as high as 25 Pa during peak intensity, and that the B storm is a southwestward-propagating storm that develops over 60° S and strengthens as it travels poleward [2,3]. We have since carried out simulations of B storms using the NASA Ames Mars Global Climate Model (MGCM), which is based on the NOAA/GFDL cubed-sphere finite volume dynamical core, at high spatial (1x1°, 60x60 km) resolution. We find that B storm dust is lofted upwards of 50 Pa by episodic pluming events somewhat resembling the rocket dust storms described in Spiga et al. (2013) [4]. Detached dust layers sometimes form from these plumes at altitudes between 25-3 Pa (3-5 scale heights). These detached layers maintain altitude for ~1 sol before the sedimentation rate of the dust exceeds the upward vertical velocity generated by the radiative heating of the suspended dust [5]. We will present results from the MGCM-simulated B storm using three-dimensional animations to illustrate the hourly evolution of the dust that is lofted during the storm. 1. Kass D. M. et al. (2016). Geophs. Res. Letters, 43, 6111–6118. 2. Batterson, C.M.L. et al. (2021). Scholarworks, SJSU Master’s Theses, 5174. 3. Batterson, C.M.L. et al. (2020). Martian B Storm Evolution: Modeling Dust Activity over the Receding South Polar CO2 Ice Cap at Southern Hemisphere Summer Solstice, Abstract (P080-0002) presented at 2020 AGU Fall Meeting, 1-17 Dec. 4. Spiga, A. et al. (2013). JGR: Planets, 118(4), 746-767. 5. Daerden, F. et al. (2015). Geophs. Res. Letters, 42, 7319-7326.