Shallow Water Model Simulations of the Lifecycle of Stratospheric Polar Vortices

There is large inter-annual variability in the lifecycle of stratospheric Arctic vortices, with the break up of the vortices occurring any time between February and May. Also, whereas there is a gradual decay for early breakups there is a rapid decay for late breakups. We examine here the processes controlling the vortex lifecycle by performing simulations using a shallow water model. These simulations include time-varying topographic forcing (to mimic upward propagating Rossby waves) and relaxation to a seasonally-varying state (to mimic the seasonal variation in radiative forcing). By varying the different parameters in the model we examine the relative roles of changes in the wave and radiative forcing in determining the timing and characteristics of the vortex breakup.