Abstract/Summary

We perform a climatological analysis of summer-time Arctic cyclone structure in reanalysis data using a phase space approach. A classification scheme for Arctic cyclones is proposed, dependent on whether vorticity structure during development is low-level-dominant (LLD) or upper-level-dominant (ULD). During growth, LLD cyclones (65.5%) exhibit warm-core asymmetric structures, whereas ULD cyclones (34.5%) have cold-core asymmetric structures. LLD cyclones typically have greater thermal asymmetry during growth. However, a transition to a persistent cold-core axisymmetric structure after maturity is characteristic of summer-time Arctic cyclones, regardless of structure during growth. LLD cyclones are typically stronger and preferentially track on the Russian coastline where there is high baroclinicity, whereas ULD cyclones tend to be longer-lived and preferentially track in the Pacific sector, where they can interact with tropopause polar vortices. This study provides a platform for further research into different classes of Arctic cyclones and associated hazardous weather, and ultimately for developing conceptual models.