An Analysis of Gravity Wave Activity near to the Andes Mountains, from GPS Radio Occultation Long Term Data

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

Viena

Congreso; General Assembly of the European Geophysical Union; 2006

European Geophysical Union

A significant wave activity in the upper troposphere and lower stratosphere was detectedat midlatitudes (30-40S) above the Andes Mountains, from a global analysisof GPS radio occultation temperature data (CHAMP and SAC-C Low Earth Orbit -LEO- satellites). These profiles were obtained between May 2001 and November 2005(257,160 events). The possible main gravity wave sources in the region considered areexpected to be: i) orographic forcing, ii) geostrophic adjustement and iii) deep convection.From the capability and available resolution of GPS soundings, the observedwave activity local enhancements might be attributed to the generation of inertio gravitywaves (IGWs), with longer horizontal and perhaps shorter vertical wavelengthsthan those typically observed in mountain waves (MWs). IGWs could be generated,after a geostrophic adjustment process near to a permanent zonal jet situated abovethe Andes Mountains, starts. The wave activity intensity exhibits an association withthe zonal wind velocity strength at jet altitudes. In fact, IGWs are expected to be moreeasily detected from GPS profiles than MWs. Nevertheless, given the predominantGPS-LEO lines of sight in the region considered as well as its orographic morphology,it should not be disclosed that the GPS RO profiles could be suitable to detectMWs too.