THE INTERACTION OF RADIATIVE AND DYNAMICAL PROCESSES DURING A SIMULATED SUDDEN STRATOSPHERIC WARMING

An analysis ofa spontaneous sudden stratospheric warming that occurred during a 2-year integration of the Langley Research Center Atmospheri c Simulation Model is presented. The simulated warming resembles obser ved ''wave 1'' warmings in the Northern Hemisphere stratosphere and pr ovides an opportunity to investigate the radiative and dynamical proce sses occurring during the warming event. Isentropic analysis of potent ial vorticity sources and sinks indicates that dynamically induced dep artures from radiative equilibrium play an important role in the warmi ng event. Enhanced radiative cooling associated with a series of upper stratospheric warm pools leads to radiative dampening within the pola r vortex. Within the ''surf zone'' large-scale radiative cooling leads to diabatic advection of high potential vorticity air from aloft. Lag rangian area diagnostics of the simulated warming agree well with LIMS analyses. Dynamical mixing is shown to account for the majority of th e decrease in the size of the polar vortex during the simulated warmin g. An investigation of the nonlinear deformation of material lines tha t are initially coincident with diagnosed potential vorticity isopleth s is conducted to clarify the relationship between the Lagrangian area diagnostics and potential vorticity advection during wave breaking ev ents.