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Abstract

Global analyses of gravity wave activity in the stratosphere obtained from CHAMP GPS radio occultation (RO) data are presented. Monthly mean values of the potential energy Ep, are taken as a measure of gravity wave activity. From the global morphology of gravity wave activity, large Ep values are noticed even at midlatitudes during winter, besides at tropical latitudes. However, this is not the case during equinoxes. This suggests that wave activity at stratospheric heights is not only modulated due to orography but mainly depends on seasonal variations at the respective latitudes. At low latitudes, correlations are found between gravity wave activity and the outgoing long-wave radiation, being a proxy for tropical deep convection. Gravity wave activity is found to be high in the zones of deep convection confirming that convection is the major source of gravity wave generation in the Tropics. Latitudinal/vertical distribution of Ep further reveals: large values below 25 km and low values between 25 and 30 km near the Equator are found in all the seasons. During southern hemisphere (SH) winter, large values of Ep are noticed. Large values are also found during equinoxes, and these values are of the same order of magnitude at northern hemisphere (NH) and SH at midlatitudes. During solstices, the Ep distribution involves a larger hemispheric asymmetry at middle and higher latitudes. Large values of Ep are noticed at SH polar latitudes during September and October and the latitudinal range is wide (±30o latitude in both hemispheres) with large Ep values in all seasons.