This project conducts research on the circulation of the Antarctic stratospheric polar vortex based on data from super pressure balloons (SPBs). SPBs have a semi-rigid envelope which, under pressure from the gas inside, maintains constant volume and hence constant effective density regardless of heating and cooling, so that they move with the wind along a nearly horizontal surface of constant density. Data for this project comes from two field campaigns,VORCORE (27 SPBs in 2005) and CONCORDIASI (18 SPBs in 2010), both of which launched balloons from Antarctica which rose to levels between 70 and 50mb and circulated within the polar vortex for several months. Instruments carried by the SPBs included miniaturized dropsondes, GPS receivers for occultation soundings, ozone sensors, and cloud ice particle counters. Research conducted under this award studies inertia-gravity waves and large-scale transport across and within the polar vortex, with four specific objectives: 1) The accurate statistical descriptions of the inertial and gravity wave fields over the Antarctic in the spatial and spectral domains, 2) The formulation of constraints for gravity wave parameterizations based on calculation of gravity wave momentum flux, 3) The influence of gravity waves on the formation of polar stratospheric clouds (PSCs, which play an important role in ozone depletion), and 4) The fundamental dynamical process at work in air exchanges and transports in relation to the polar vortex, with an emphasis on the role of Rossby wave breaking. The work uses a combination of observational analysis and modeling, and uses novel methods motivated by dynamical systems theory to address air exchange and transport across and within the polar vortex.
The problems addressed in the proposal are of societal as well as scientific interest for two reasons. First, the processes examined here are all relevant to the formation of the ozone hole, as ozone depletion depends on transport and mixing of stratospheric air across and within the polar vortex, and gravity wave motions may play a role in the formation of PSCs. Second, gravity wave momentum fluxes are thought to play an important role in determining the strength of atmospheric circulation, and the effects of gravity waves are paremeterized in weather and climate models. Thus, observational analysis of gravity wave properties may be beneficial for weather and climate modeling and prediction. In addition, the work will support and train a graduate student, thereby providing for the next generation of scientists in this field.