Analysis on the global morphology of stratospheric gravity wave activity deduced from the COSMIC GPS occultation profiles

Abstract

Monthly mean global morphologies of potential energy density Ep from stratospheric gravity waves are revealed by observations of COSMIC GPS radio occultation. The Ep is obtained from vertical wavelengths ranging from 2 to 10 km over cells of 1° × 2° in latitude and longitude. The computed values confirm previous results and obtain new ones. The large gravity wave Ep values found in the tropics between 25°N and 25°S could be mainly due to the strong tropical cumulus convection; July values are larger than those for January (2007). In mid and high latitudes, the most prominent features of the northern winter hemisphere are the enhanced densities above the Eurasian continent and the North Atlantic and the depressed Ep values above the North Pacific and North America for which topography, wind sources and wind filtering may be responsible. In southern winter hemisphere, large Ep values are found around 180° and 300° longitudes that are likely due to the topography of the Antarctic plateau, the Antarctic Peninsula and South America. Enhanced Ep values are found over Scandinavia. However, there is no clear evidence to show that gravity waves are localized over the Rocky Mountains, the Himalayas and the Andes. Topography and planetary wave modulations are proposed to interpret the large-scale longitudinal variations and inter-hemisphere asymmetry of the GW activity.