An object oriented climatology of statospheric polar vortices and anticyclones

United Kingdom Meteorological Office analyses from 1991 to 2001 are used to create a global climatology of stratospheric polar vortices and anticyclones. New methodologies are developed that identify vortices in terms of evolving three dimensional (3-D) air masses. Seasonal frequency distributions of polar vortices and anticyclones illustrate their climatological location and persistence A counterpart to the Northern hemisphere Aleutian High (AH) is documented in the Southern Hemisphere: the “Australian High” (AUH). The temporal evolution of the area occupied by polar vortices and anticyclones is shown as a function of potential temperature in both hemispheres. Large polar vortex area leads to anticyclone area increasing, which in turn, results in polar vortex area decreasing. During Northern winter and Southern spring, daily isentropic movement of anticyclones is shown in the 400–2000 K layer. Preferred locations of anticyclogenesis are colocated with cross-equatorial flow and weak inertial stability. Mid-high latitude anticyclones are largely quasi-stationary. However, subtropical anticyclones are observed to move poleward and eastward.; The evolution of the AH and AUH vertical tilt is shown over the 10 year record. From this time series, 42 distinct AH life cycles are identified. On average there are 4 AH life cycles per winter. Phase diagrams show that in ≈85% of AH life cycles the anticyclone initially tilts westward with altitude and as the anticyclone matures it becomes more zonally upright and tilts further poleward. Of the 36 life cycles where this transition is particularly robust, 18 cases are identified and composited. This AH “life cycle composite” acts as a representative case study with which to examine the evolution of the Eulerian structure and the Lagrangian flow. In the mid-lower stratosphere trajectories remain inside the AH more than 1 month, the life of the trajectory. Overall, trajectories that remain inside the AH descend less rapidly than those that exit the anticyclone.