Ozone trends in the upper troposphere-lower stratosphere using equivalent latitude-potential temperature

We analyze ozone trends in the upper troposphere and lower stratosphere (UTLS,∼300-50 hPa), using geographical (latitude-pressure and latitude-altitude) and, for thefirst time, dynamical (equivalent latitude-potential temperature, EqL-θ) coordinates. Trendsare determined using linear least-squares fits, multiple linear regression, and dynamicallinear modeling. Regardless of the method, EqL-θ improves consistency between trendsacross the UTLS, reduces large UT tropical uncertainties, alters the magnitude of mid latitude trends, and, most notably, in the Southern polar lower stratosphere, reveals statistically significant trends exceeding 8% per decade during Antarctic Spring. This provides further evidence of Antarctic ozone recovery. These robust trends are not capturedusing geographical coordinates. We argue that EqL-θ enables more physically groundedinterpretations of chemical ozone trends and their uncertainties, as EqL-θ accounts forthe adiabatic (reversible) transport of ozone.