ESTIMATED VERTICAL FLUX OF HORIZONTAL MOMENTUM DUE TO MOUNTAIN WAVES FROM GPS RADIO OCCULTATION DATA ABOVE SOUTHERN ANDES AND THE ANTARTIC PENINSULA

A. DE LA TORRE, P. ALEXANDER, P. LLAMEDO, R. HIERRO, T. SCHMIDT, A. FABER, AND J. WICKERT

Buenos Aires

Workshop; 7th IAGA / ICMA / CAWSES Workshop on Long-Term Changes and Trends in the Atmosphere; 2012

IAGA / ICMA / CAWSES

Above the southern Andes range and its prolongation in the Antarctic Peninsula, largeamplitude mountain gravity waves with a relevant influence in the dynamics of the lower and middle atmosphere were systematically observed from mesoscale model simulations and different satellite techniques of observation. In particular, from GPS (Global Positioning System) and Low Earth Orbit (LEO) satellite radio occultations (RO), high resolution temperature profiles were retrieved for atmospheric limb soundings since 2001, under longterm stability conditions, all-weather capability and global coverage in the upper troposphere and lower stratosphere (UTLS) system. Ern et al (2004) developed a method to estimate the vertical flux of horizontal momentum (MF) due to gravity wave oscillations, from single temperature (T) profiles. In doing so, the prevailing wavelike component must be isolated after a proper subtraction of the additional temperature variations due solely to planetary waves. An important unknown required parameter, according to this calculation, is the horizontal wavenumber vector corresponding to the prevailing mode. In a recent paper, de la Torre et al (2012) noted from mesoscale simulations that one or at most two prevailing mountain modes of oscillation, with short horizontal wavelengths, are regularly observed in the region above considered and the corresponding typical horizontal directions of propagation were identified. From these results, we discuss here an estimation of lower and upper bounds to MF profiles, able to be computed from Ern´s method and available GPS RO T profiles in the region since 2001. We consider realistic horizontal wavelengths and known upwind wave propagation, as previously simulated. The hypotheses involving Ern´s method possibly affecting the estimations here presented are pointed out. A complementary presentation (Llamedo et al.) accounts for a global analysis in the UTLS system, also from GPS-LEO radio occultation data.