Modeling the B Regional Dust Storm on Mars

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.