Improvement of stratospheric balloon GPS positioning and the impact on gravity wave parameter estimation for the Concordiasi campaign in Antarctica

Abstract

Gravity waves (GWs) play an important role in transferring energy and momentum from the troposphere to the middle atmosphere. However, shorter‐scale GWs are generally not explicitly resolved in general circulation models but need to be parameterized instead. Super pressure balloons provide 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 the 2010 Concordiasi campaign in the Antarctic is much higher compared to the previous campaigns and can cover the full range of the GW spectrum. Two among 19 balloons are also equipped with the dual‐frequency GPS receivers initially developed for GPS radio occultation research in addition to the single‐frequency receivers, which are expected to provide better positions for GW parameter estimations. Improvements of the positions are significant, from ~3–10 m horizontal and ~5 m vertical to ~0.1 and 0.2 m, respectively, which makes it possible to resolve the Eulerian pressure independently of altitude for the intrinsic phase speed estimation. The lower position accuracy in the previous analysis of campaign results from the single‐frequency GPS receiver was primarily due to a problem with the onboard clock that is not present in the new results. The impacts of the position improvements on the final GW parameters are highlighted, with larger difference in momentum flux for the shorter‐scale GWs than for the longer scale GWs and significant difference in the distribution of the intrinsic phase speed.

Equatorial waves resolved by balloon-borne Global Navigation Satellite System radio occultation in the Strateole-2 campaign

“…The precise position calculation was shown to be a significant improvement over the onboard real-time GPS solution. It has been used to improve the calculation of gravity wave momentum flux from balloon motion variations that treat the balloon as a quasi-Lagrangian tracer (Zhang et al, 2016).…”

“…This precise positioning provides better estimates of the winds and reliable vertical positions that are independent of the pressure measurement, which makes it possible to resolve the Eulerian pressure independently of altitude for the intrinsic phase speed estimation in the spectral analysis of the in situ data (Boccara et al, 2008;Vincent and Hertzog, 2014). This was illustrated in the high-precision positioning used in the gravity wave analysis of the stratospheric balloon data from the Antarctic Concordiasi campaign and led to better estimates of the momentum flux of high-frequency gravity waves (Zhang et al, 2016). A similar analysis is planned for future Strateole-2 observations.…”