DE LA TORRE Alejandro
congresos y reuniones científicas
GW activity and horizontal propagation above Southern Andes, Drake Passage and Antarctic Peninsula UTLS with GPS radio occultations and mesoscale simulations
A. DE LA TORRE, P. ALEXANDER, P. LLAMEDO, R. HIERRO, A. ROLLA, T. SCHMIDT, J. WICKERT
Congreso; OPAC 2010; 2010
Universidad de Graz
The global distribution, generation and variability of horizontal and vertical gravity waves (GWs) propagation, their energy content and the vertical flux of horizontal momentum represent nowadays basic ingredients in the understanding of the lower and middle atmosphere dynamics. The UTLS region above the southern Andes Range, Drake Passage and Antarctic Peninsula constitute a natural laboratory where the effect of orographic and non-orographic GW sources compete between them in the total balance of wave energy. In this talk, we discuss recent results focused to this region, as a preliminary stage to the accomplishment of the SAANGRIA (Southern Andes-ANtarctic GRavity wave InitiAtive) Experiment. The objective of the SAANGRIA project is to study the dynamics of GW in the Southern Andes-Antarctic Peninsula region from the surface of the earth to the mesosphere and lower thermosphere. We first describe a long-term seasonal and geographical GW amplitudes, vertical wavelengths and activity from CHAMP and COSMIC GPS RO T data. The observed features complement observations in the same zone by other satellite passive remote sensing instruments able to detect different height regions and other spectral intervals of the wave spectrum, and by mesoscale WRF simulations. Topography is an important source and some strong wave activity is also found over open ocean. Critical level filtering is shown to have an attenuation effect, implying that a large fraction of the observed activity can be considered to be an outcome of mountain waves. The wavefronts, nearly aligned with the North-South direction, are easily detected by the nearly meridional line of sight characterizing most of the GPS RO observations. We adapt a previous method for the determination of horizontal propagation of large amplitude GWs by Ern et al (2004). We consider triads of profiles, instead of the usual subdivision in latitude-longitude cells, intending to optimize the available information provided by the highly inhomogeneous geographic distribution of GPS RO soundings. To remove the remaining -phase uncertainty in the horizontal wave propagation vectors we apply physical arguments. The geographic distribution of estimated uncertainties in the determination of mean specific potential energy is discussed.