GLOBAL MOMENTUM FLUX DETERMINATION FROM GPS RADIO OCCULTATION DATA

A. FABER, P. LLAMEDO, T. SCHMIDT, A. DE LA TORRE, J. WICKERT

Buenos Aires

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

IAGA / ICMA / CAWSES

The GPS Radio Occultation technique (RO) is a well-established technique for obtaining global gravity wave (GW) information from temperature profiles. RO uses GPS signals received aboard low Earth orbiting satellites for atmospheric limb sounding. Temperature profiles are derived with high resolution and provide a global coverage under any weather conditions offering the possibility for global monitoring of the temperature structure and wave parameters. The six satellites constellation COSMIC/FORMOSAT-3 delivers approximately 1800 temperature profiles daily. In this study, we derive global distributions of vertical and horizontal wave numbers and wave potential energy, needed to compute the momentum flux. The horizontal wavenumber kh is derived by the ratio of the phase shift gij and the spatial distance gxij between the regarded profiles at a given altitude (kh=gij /gxij). To extract the horizontal wavelength along the wave propagation direction, a third measurement is needed. These triads must be close in time and space. The horizontal and vertical wavelength, the specific potential energy (Ep), the vertical flux of horizontal momentum (MF) is calculated and possible trends are discussed. Horizontal wavelengths around 700-1200 km dominate the entire globe, but three sharp minima can be found distributed along the equator region with values around 200-400 km. These minima relate to the maxima found in the momentum flux distribution and can be correlated to convection via tropical rainfall measurements. Global analysis including seasonal mean results of vertical wavelength and potential energy in an altitude range of 20 to 25 km are discussed, too.