Potential vorticity and ozone in Martian polar regions

Introduction: Potential vorticity (hereafter PV) is a dynamical tracer which is a product of the absolute vorticity and static stability of the atmosphere. PV can be redistributed but neither created or destroyed on an isentropic surface in the absence of friction and diabatic processes [1]. The conservation principle explains why PV is used to study polar vortices on Earth. PV contains information on winds and temperature in a single scalar variable and the motion of air is generally parallel to contours of PV [2]. The invertibility of PV is also an important property, since given sufficient boundary conditions PV can be inverted to deduce the flow of the whole atmosphere. Changes in the PV distribution thus `induce' changes in the wind and temperature fields. On Earth, studies have found a significant positive PV-ozone correlation in both global maps of total ozone from satellite observations [3] and local profiles of ozone at multiple observatories [4,5], particularly at mid to high latitudes in the winter hemisphere (Figure 1). While the relationship of ozone and PV on Mars has never before been investigated, a strong correlation between PV, a dynamical tracer, and ozone suggests several applications such as using ozone observations to study the dynamical behaviour of the polar vortices and using PV as a proxy for ozone in polar winter.