Previous: Ext. Abst. Next: Determination of potential energy (Ep) from GPS/MET profiles Up: Ext. Abst

1. GPS/MET experiment

The GPS/MET (Global Positioning System/Meteorology) experiment has been initiated by the University Corporation for Atmospheric Research (UCAR), successfully providing the international scientific community with a new global high resolution data set of temperature, pressure and refractivity profiles in the 1-60 km height range. These profiles are obtained from the active limb sounding occultation technique as described by Ware et al. [1996] and Rocken et al. [1997]. In this experiment, a GPS receiver aboard Microlab-1 was launched on April 3, 1995, into a low earth orbit (LEO) to observe occulted radio signals from the GPS satellites. Height profiles of atmospheric refractive index were derived from these observations. By assuming the hydrostatic relation for a dry atmosphere, temperature profiles can further be inferred. Rocken et al. [1997] showed 1 K mean temperature agreement with the best correlative data between 5-40 km. The GPS/MET profiles are found to be very unique in revealing detailed temperature structure, including sharp inversions and step-wise increase of temperature gradient near the tropical tropopause, which has not been achieved by a conventional satellite measurement [Nishida et al., 2000].

In this study we have analyzed meso-scale temperature perturbations caused by gravity waves using all published GPS/MET temperature profiles between April 1995 and February 1997, available at the GPS/MET office of UCAR. Then, we have defined the potential energy Ep, from the temperature variance, and studied the energy distribution of gravity waves in the stratosphere as a function of latitude, longitude, season and altitude. We have also retrieved temperature profiles with a better height resolution (about 200 m) from Level-2 GPS/MET data collected during prime times, and analyzed vertical wavenumber spectrum of the normalized temperature fluctuations.