A global morphology of gravity wave activity in the stratosphere revealed by the GPS occultation data (GPS/MET)

Using temperature profiles obtained by the GPS/MET (GPS Meteorology) experi ment from April 1995 to February 1997, we have extracted mesoscale temperat ure perturbations with vertical wavelengths ranging from 2 to 10 km and bac kground Brunt-Vaisala frequency squared, N-2. For each occultation event, w e can evaluate a potential energy E-p which is assumed to be caused by atmo spheric gravity waves. The monthly mean values of E-p at 15-20 km around Ja pan showed an annual variation with an enhancement in winter, which is cons istent with the climatological behavior of the kinetic energy of gravity wa ves observed with the MU (middle and upper atmosphere) radar (34.9 degrees N, 136.0 degrees E) from 1985 to 1989. We have then derived the global dist ribution of E-p at 20-30 km during Northern Hemisphere winter (from Novembe r to February). Our analysis shows that the largest E-p values are generall y centered around the equator between 25 degrees N and 25 degrees S with co nsiderable longitude variations. Longitudinal variations of E-p at 20-30 km in a latitude range of 30 degrees-60 degrees N are also analyzed, resultin g in larger Ep values over the continents than over the Pacific Ocean. Usin g GPS/MET data without antispoofing, latitudinal variations of E-p are dete rmined in 15-45 km. Although large E-p values are concentrated near the equ ator at 20-30 km, E-p tends to become larger at midlatitudes at 30-40 km an d higher-altitude regions. At midlatitudes, E-p is found to be larger in wi nter months in both hemispheres. Height variations of indicate a decrease a t 25-30 km and a monotonic increase above 30 km.