Local Time Variability of Gravity Wave Activity Revealed by SABER Temperature Observations

The global characteristics of gravity wave potential energy variation depending on local time are analyzed using satellite observations covering a broad range of local times. A clear diurnal variation is observed in the equatorial region between 15°S and 15°N. At midlatitudes (15°N–60°N and 15°S–60°S), a semidiurnal variation is observed at higher altitudes above 90 km, in addition to the diurnal variation at lower altitudes below 90 km. These results are consistent with previous studies of ground-based observations, though quantitative comparisons are difficult. The potential energy variation corresponds to the variation in static stability, which is also obtained from the same satellite observations. The local time variation of temperature is consistent with the variation in static stability, while the zonal wind variation is not always consistent. These results suggest the importance of temperature structures associated with tides, in the interaction between gravity waves and tides.