Superpressure balloons (SPB), which float on constant density (isopycnic) surfaces, provide a unique way of measuring the properties of atmospheric gravity waves (GW) as a function of wave intrinsic frequency. However, SPB start to depart from their isopycnic surface for wave periods less than about 15-20 min and the accuracy of momentum flux retrievals decreases for short period waves. A new approach is described that accounts for the balloon response function and improve flux retrievals for these waves. The methodology is tested using new high precision measurements of SPB locations made during the 2010 Concordiasi campaign over Antarctica. Two 12-m diameter balloons carried high-accuracy dual-frequency GPS receivers that allowed position measurements to be made to accuracies of about 0.1 m and 0.2 m in the horizontal and vertical, respectively. With this degree of accuracy it is possible to ‘deconvolve’ the effect of the balloon response function and determine the vertical displacement of the wave field, and hence vertical velocities, directly. This, in turn, leads to a more direct estimate of momentum fluxes than the method used currently in SPB GW studies. Fluxes can be determined to much smaller amplitudes than previously, thus extending the dynamic range over which GW fluxes can be determined using SPB techniques. Results are illustrated using the high-resolution Concordiasi data. The methodology has ramifications for future SPB flights in equatorial regions where tropical convection generates large amplitude, short period gravity waves.

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*email: robert.vincent@adelaide.edu.au
*Preference: Oral