An Investigation of the Encirclement of Mars by Dust in the 2018 Global Dust Storm Using EMARS

Determining how global dust storms originate and develop is one of the major challenges of Martian meteorology. We model the 2018 global dust storm using the Ensemble Mars Atmosphere Reanalysis System (EMARS), combining satellite observations with a Mars global climate model via data assimilation. A reanalysis is a valuable data set for this investigation because it is anchored to the real Martian atmosphere by temperature and dust observations, and the model provides full 4D coverage of wind fields, which are not directly observed and are key to assessing advection. Dust was observed to encircle the northern hemisphere early on in the storm's development. This encirclement could be caused by either the formation of new lifting centers along the path of observed encirclement or the advection of dust from active lifting center(s) elsewhere. Results from EMARS, including particle advection from inferred EMARS winds, provide evidence that the aforementioned dust encircling Mars's northern hemisphere may come from the initial lifting center of the storm, near Chryse Planitia. We propose that dust from the initial lifting center of the storm was entrained into the Martian Hadley circulation, with the assistance of the thermal tides, and then entrained into the northern hemisphere westerly jet.