Abstract

To improve the representation of the mountain wave-induced PSC formation mechanism in the UM-UKCA chemistry-climate model, the temperature fluctuations due to unresolved (sub-grid) mountain waves are parameterised. For case studies of stratospheric mountain waves over the Antarctic Peninsula, it is demonstrated that the stratospheric temperature fluctuations computed by the parameterisation scheme are in excellent agreement with high-resolution simulations and satellite measurements. The parameterisation was subsequently used to compute the local mountain wave-induced cooling phases in UM-UKCA. The increased stratospheric cooling was passed to the PSC scheme of the model, and caused a 30-50% increase in PSC surface area density over the Antarctic Peninsula compared to a 30-year control simulation. The parameterisation offers a method for improving lower stratospheric temperatures that satisfy PSC thresholds, the failure of which has been suggested as one of the main reasons for the poor simulation of ozone depletion in models.