Tropospheric synoptic scale disturbances and the deformation of the Antarctic Polar Vortex

1. 90 1 90 1 120 60 120 60 0.8 0.8 0.6 0.6 150 30 150 30 0.4 0.4 0.2 0.2 180 0 180 0 200 150 210 330 210 330 90 100 1 240 300 50 120 60 270 240 300 0.8 270 90 90 1 1 120 60 120 60 0.8 0.8 0.6 0.6 0.6 150 30 150 30 150 30 0.4 0.4 90 90 1 1 0.4 0.2 0.2 120 60 120 60 0.8 0.8 180 0 180 0 0.2 0.6 0.6 150 30 150 30 0.4 0.4 210 330 210 330 0.2 0.2 180 0 100 240 300 180 0 180 0 50 240 300 270 270 90 90 1 1 200 120 60 120 60 0.8 0.8 150 0.6 0.6 210 330 210 330 150 30 150 30 0.4 0.4 210 330 300 100 0.2 0.2 240 300 240 300 250 50 180 0 180 0 270 270 200 240 300 150 210 330 210 330 270 100 240 300 270 240 300 50 270 Tropospheric synoptic scale disturbances and the deformation of the Antarctic Polar Vortex Pablo O. Canziani1,2, Walter E. Legnani3, and Rolando R. Garcia4 1 Programa de Estudios de Procesos Atmosféricos en el Cambio Global –Pontificia Universidad Católica Argentina/CONICET – Argentina 2 Departamento de Ciencias de la Atmosfera y los Océanos, Universidad de Buenos Aires/CONICET - Argentina 3 Instituto de Cálculo - Universidad de Buenos Aires - Argentina 4National Center for Atmospheric Research - U.S.A. The aim of this work is to demonstrate the influence of synoptic scale disturbances, on the evolution of the Antarctic polar vortex/ozone hole. The synoptic scale perturbations can propagate from the troposphere, and reach the lower stratosphere. A study was carried out to determine the presence and characterisation of synoptic perturbations at different heights so as to understand their vertical structure. Such an analysis required the use of spectral filters in space, separating the perturbations as a function of their spatial wave properties. Daily values were used so as to preserve the non-linear time relationships. The conditions for penetration/propagation of these systems into the lower stratosphere were evaluated. The impact of such synoptic systems upon the vortex and ozone hole dynamics was then analysed. Geopotential height dynamics was used to follow the ozone hole dynamics. A case study covering the months of October and November 1990 was chosen to study, and this was compared with independent data from NASA s Goddard Space Flight Center (potential vorticity) and NOAA (wind and temperatures). NCAR Vortex Shape Classfications 400 450 400 350 350 300 300 250 250 200 150 100 50 First set of events corresponding to a deformation type I Second set of events corresponding to a deformation type II Deformation Type I Deformation Type II Ellipsoid deformation Irregular deformation Penetration criteria October 12, 1990 October 13, 1990 October 14, 1990 October 6, 1990 October 7, 1990 October 8, 1990 Geopotential anomalies (High Pass) October 14, 1990 57º South. Geopotential anomalies (Low Pass) October 14, 1990 57º South. Geopotential anomalies (High Pass) October 7, 1990 57º South. Geopotential anomalies (Low Pass) October 7, 1990 57º South. Low Pass anomalies and circulation near the vortex Low Pass anomalies and circulation near the vortex High Pass anomalies and circulation near the vortex High Pass anomalies and circulation near the vortex Scarce rate of contribution of synoptic scale waves to the vortex shape Significant rate of contribution of synoptic scal waves to the vortex shape Summing up The polar vortex deformation in the first case responds solely to a strong planetary wave 2 event. In the second case the vortex deformation responds as well to synoptic wave packets reaching into the lower stratosphere. The confirmation of the role of synoptic scale perturbation contribution to the polar vortex deformation is a contribution towards the understanding of the processes involved in the vortex dynamics of this phenomenon. For a detailed analysis of wave propagation during these events cf. Canziani and Legnani, Quarterly Journal of the Royal Meteorological Society. Vol 129, July 2003