On the Southern Gravity Wave Hot Spot: An Individual Waves Study with Cosmic GPS-RO

Abstract:

The mountainous Southern Andes and Antarctic Peninsula (SAAP) region is one of the most intense sources of Gravity Waves (GWs) on Earth. In austral winter, momentum deposition from orographic GWs into the lower stratosphere from this region can exert a strong drag effect on winds in the polar stratospheric jet. The exact nature of this drag effect is difficult to parameterise operationally in GCMs, and as a result such wave parameterisations are generally poorly constrained by observations.

Using COSMIC GPS-RO, we observe high Gravity Wave Potential Energy (GWPE) both directly over the SAAP region and downwind in a long leeward wake stretching more than half way around the globe, and comment on possible relationships between the two features. We also observe a vertical column of GWPE directly over the Southern Andes in both zonal and meridional cross-sections, the latter of which suggests a strong southward advection of orographic GWs into the polar stratospheric jet.

We investigate the observed difference in monthly GW climatologies when an approach using only COSMIC profiles in which GW signals have been clearly identified is applied in preference to the traditional all-measurement time-averaged approach, and use this to obtain an estimate of GW intermittency in the SAAP region.

Finally, we take advantage of the deployment phase of the COSMIC constellation to obtain an estimate of momentum flux in the SAAP region, using the phase difference between pairs of closely spaced profiles to estimate the horizontal wavelengths of resolved GWs. We demonstrate that during the deployment phase, momentum flux estimates derived from COSMIC GPS-RO are comparable to those derived from HIRDLS.