An Eight-Year Climatology of the Martian Northern Polar Vortex

Understanding the behaviour of Mars’ polar vortices, and their modification under different dust loading conditions, is important for understanding its contemporary and ancient climate, including aerosol and chemical cycles. We present an eight martian year climatology of the northern polar vortex, via the assimilation of orbital temperature and dust observations into a global climate model. We show that the general seasonal behaviour and morphology of the vortex is highly interanually repeatable, with the important exception of dust storm effects. Previous work has focused on individual regional or global dust storm effects, specifically solstitial events for the latter; by investigating an eight-year period covering two global and multiple regional dust storms, we are able to investigate the potentially crucial impact of dust storm timing on vortex effects as suggested by previous work [10]. We find that the seasonal timing of atmospheric dust loading does indeed have a crucial role in determining the dynamical effects of a storm on the northern polar vortex. Storms later in the dusty perihelion season, such as solstitial global dust storms and C-type regional dust storms [11], have a signifi-cantly greater disruptive effect on both the morphology (including latitudinal extent) and intensity of the vortex than those early in the season, such as equinoctial global dust storms and A-type regional dust storms.