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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 113, D04107, doi:10.1029/2007JD008938, 2008

Characteristics of atmospheric gravity wave activity in the polar regions revealed by GPS radio occultation data with CHAMP

Hayato Hei

Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Japan


Toshitaka Tsuda

Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Japan


Toshihiko Hirooka

Department of Earth Planetary Sciences, Kyushu University, Fukuoka, Japan


Abstract

Using GPS radio occultation data during 2001–2005, we studied the climatological behavior of atmospheric gravity waves in the polar stratosphere. We calculated temperature fluctuations with vertical wavelengths shorter than 7 km and then determined the wave potential energy, E p , every month in a longitude-latitude cell of 20° × 10° between 12 km and 33 km. In the Arctic region (50–90°N), E p shows an annual variation with maximum in winter, consistent with the zonal mean horizontal wind, V, and the Eliassen-Palm (E-P) flux, F z . The large F z values indicate higher planetary wave activity, resulting in distortion of the polar vortex. The unbalanced flow can then excite gravity waves through geostrophic adjustment. In the Antarctic region (50–90°S), E p gradually increases during winter and reaches its maximum in spring before decreasing rapidly. The time derivative of V coincides with the E p peak and the horizontal distribution of E p has a similar structure to V, suggesting that the E p enhancement is closely related to the decay of the polar vortex. During major warming events over the Arctic, the divergence of E-P flux, ΔF, was enhanced, coinciding with large E p . In the Antarctic, ΔF strongly correlates with E p in spring. Gravity waves seem to be effectively generated through planetary wave transience and/or breaking. Orographic generation of gravity waves seems to be important in limited areas only, such as Scandinavia and the Antarctic Peninsula, showing that it is less important than the polar night jet in determining the climatological behavior of gravity waves.

Received 10 May 2007; accepted 4 December 2007; published 27 February 2008.

Keywords: gravity waves; polar region; GPS radio occultation.

Index Terms: 3334 Atmospheric Processes: Middle atmosphere dynamics (0341, 0342); 3349 Atmospheric Processes: Polar meteorology; 3394 Atmospheric Processes: Instruments and techniques; 3384 Atmospheric Processes: Acoustic-gravity waves; 6969 Radio Science: Remote sensing.

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Citation: Hei, H., T. Tsuda, and T. Hirooka (2008), Characteristics of atmospheric gravity wave activity in the polar regions revealed by GPS radio occultation data with CHAMP, J. Geophys. Res., 113, D04107, doi:10.1029/2007JD008938.