Improvement of stratospheric balloon positioning and the impact on Antarctic gravity wave parameter estimation

Abstract:

Gravity waves (GWs) play an important role in transferring energy and momentum from the troposphere to the middle atmosphere. However, shorter period GWs are generally not explicitly resolved in general circulation models but need to be parameterized instead. Super pressure balloons, which float on the isopycnal surfaces, provide a direct access to measure GW characteristics as a function of wave intrinsic frequency that are needed for these parameterizations. The 30 s sampling rate of the GPS receivers carried on the balloons deployed in 2010 Concordiasi campaign in the Antarctic region is much higher compared to the previous campaigns and can cover the full range of the GW spectrum. Two among 19 balloons in the Concordiasi campaign are also equipped with the high-accuracy dual-frequency GPS receivers initially developed for GPS radio occultation research in addition to the regular single-frequency receivers, which enables us to expect a better accuracy of balloon positions for the purpose of GW momentum flux estimates. The positions are estimated using the Precise Point Positioning with Ambiguity Resolution (PPPAR) method based on the GPS data. Improvements of the positions are significant, from ~3-10 m to ~0.1-0.2 m in 3-D positions, which makes it possible to resolve the Eulerian pressure independently of height for the estimation of the intrinsic phase speed. The impacts of the position improvements on the final GW parameters (momentum flux and intrinsic phase speed) retrievals are highlighted, with ~0.54 mPa difference of the mean absolute momentum flux in Antarctic region and considerable difference in the distribution of the intrinsic phase speed.