A possible classification of GWs during SOUTHTRAC from a rotary analysis perspective

A. DE LA TORRE,; P. ALEXANDER; T. MARCOS; P. LLAMEDO; R. HIERRO; HORMAECHEA, J. L.; P. PREUSSE; M. GELDENHUYS ; L. KRASAUSKAS; A.GIEZ; B. KAIFLER; M. RAPP

Workshop; Virtual SOUTHTRAC-GW Workshop; 2021

The Southern Hemisphere Transport, Dynamics, and Chemistry–Gravity Waves(SOUTHTRAC-GW) mission was performed during September and November of 2019above the southern Andes, the Patagonia, the Antarctic Peninsula and the surroundingoceanic areas. In agreement with many previous papers, it put in evidence once morethe existing strong hotspot of GW activity during austral winter and early spring. Thecomplex structure inherent to the observed atmospheric GW activity, from multiplesimultaneous experimental platforms and diverse observational windows wasappreciated. As an approach to the understanding of main orographic and nonorographic GWs sources and their dominant vertical senses of propagation, we proposea spectral rotary analysis, based on previous developments. It is here illustrativelydeployed applying ECMWF IFS simulations. In doing so, we divided the atmosphericregion of interest in two altitude intervals, above and below the average coldest height(ACH)tropopause, where the lapse rate changes its sign and making use of themaximum attainable height. We first illustrate the spectral rotary analysis in a singlepixel, to then extend it over the entire region of interest. The simulations from IFS andthe regional WRF 4.2 models were previously compared with the measurementsretrieved from two of the platforms deployed during one of the SOUTHTRAC flights.We assume a scenario built up by a broad spectrum of linear GWs with differentsaturated and non saturated amplitudes, diverse frequencies and wavelengths. Based onthe degree of GWs polarization and the total GW energy, the net contribution of theoverall up- and downgoing wavepackets is illustratively described as a function of theGW vertical wavenumber. Some main collective features may be identified. In the Thelower height interval (LHI) includes the troposphere and the lower stratosphere. In it,there is a coexistence of alternating narrow sectors of stationary linearly polarized (LP)and up- and downgoing GWs very close to and above the southern Andes and AntarcticPeninsula. In the The upper height interval (UHI) includes the upper stratosphere andthe lower mesosphere., a A general enhanced wave activity respect to lowertroposphericlevels and an anticlockwise sectors with increasing height aligned with and to the eastof the Andes Mountains, alternating with narrow LP sectors and wider ellipticallypolarized downwards GWs are seen. At all altitudes, a smaller GW activity above thesea than above continental areas is observed. We stress that the analysis here proposedaims to illustrate its advantage, during one of the SOUTHTRAC flights, in theinterpretation of a complex ensemble made up of large amplitude waves. These aresupposed to be broadly distributed between buoyancy and Coriolis frequencies.