An Analysis of Gravity Wave Activity near to the Andes Mountains, from CHAMP and SAC-C GPS Radio Occultation Long Term Data

A. DE LA TORRE (1), P. ALEXANDER, P. LLAMEDO SORIA, C. MENÉNDEZ, T. SCHMIDT, J. WICKERT

Viena, Austria

Congreso; EGU 2006; 2006

  A significant wave activity (WA) in the upper troposphere and lower stratosphere, was detected from a global analysis of GPS radio occultation temperature data (CHAMP and SAC-C Low Earth Orbit -LEO- satellites) between May 2001 and February 2006 at midlatitudes (30-40S), above the Andes Mountains (Mendoza, Argentina). The possible main gravity wave sources in the region considered are expected to be: i) orographic forcing, ii) geostrophic adjustement and iii) deep convection. From the capability and available resolution of GPS soundings, the observed wave activity local enhancements may be attributed to any of the three sources mentioned above. In particular, inertio gravity waves (IGWs), with longer horizontal wavelengths and typically shorter vertical wavelengths than those observed in mountain waves (MWs) could be generated, following a geostrophic adjustment process near to a permanent zonal jet situated above the Andes Mountains. The monthly WA intensity follows the zonal wind velocity strength at jet altitudes and exhibit systematic enhancements during winter.  IGWs are expected to be more easily detected from GPS profiles than MWs. Nevertheless, given the predominant GPS-LEO lines of sight and the orographic morphology in the region considered, the GPS RO profiles should be suitable to detect MWs too.