Studies of Waves and Circulation Features in the Antarctic Stratosphere using VORCORE Data

University Of California-Los Angeles, Los Angeles CA

Investigators

Abstract

Mechoso and his team will analyze data obtained by the VORCORE campaign of constant-density balloon observations over Antarctica. Twenty-seven such balloons were launched from McMurdo Station (77.5ºS) during the Austral spring of 2005. The pressure and position information from these balloons are unique data for studying waves in Antarctic atmosphere and its overall circulation. Of particular interest is the utility of these data for observing internal gravity waves. Gravity waves are ubiquitous in the atmosphere. Their vertical transport of momentum is important for the atmospheric circulation, especially in the middle atmosphere, and all modern climate models include gravity-wave parameterizations. These parameterizations are, however, only poorly constrained by observational data. In the Antarctic lower stratosphere, poorly represented gravity waves may be responsible for the persistent cold biases displayed by many climate models. To make optimal use of the VORCORE balloon data, a formalism for analyzing gravity wave fields and fluxes in isopycnal (log-density) coordinates has been developed, and will be applied in this project. Specific analyses will include: estimating gravity-wave momentum fluxes in order to constrain gravity-wave parameterizations, determining the effects of topographic waves on the large-scale circulation and their role in creating conditions in which polar stratospheric clouds can form, observing the wave field at near-inertial frequencies, where previous observations have indicated the wave spectrum is strongly enhanced, studying the final stratospheric warming of 2005, analyzing Lagrangian dispersion across the edge of the polar vortex, and validating global analyses of the Antarctic lower stratosphere and testing the impact of assimilating VORCORE data on these analyses. Data from the Concordiasi balloon campaign will also be analyzed as they become available. Concordiasi is a collaboration between the United States and France. The Concordiasi observations will be made during the austral spring of 2008 and comprise part of the U.S. and French contributions to the International Polar Year (IPY). The constant density balloons used in Concordiasi will deploy dropsondes, which measure vertical profiles of temperature, humidity, and pressure between the balloon and the surface. These data will provide valuable information about waves propagating to the balloon level from below. A limited set of data from a tropical balloon campaign conducted from Ecuador in 1998 will also be analyzed. The focus here will be on studying the spectra of waves generated over convectively active regions. Broader impacts of this research are in gaining a better understanding of the circulation and dynamics of this atmospheric region in which the ozone hole forms. This project is a contribution to the intense international observations of the Polar Regions during the IPY. A graduate student will be trained.