A statistical study of gravity waves in the polar regions based on operational radiosonde data

Gravity waves in the lower polar stratosphere are examined using operationa l radiosonde observations gathered from 33 stations over a period of 10 yea rs. Both the potential and kinetic energies of the gravity waves vary annua lly and reach maxima in winter in the Arctic and in spring in the Antarctic . In the Antarctic spring a region of large gravity wave energy propagates downward following the movement of a zone of high static stability associat ed with Southern Hemispheric warming. Moreover, the enhanced energy region and the high stability zone coincide in the horizontal plane and move gradu ally from 135 degrees E, 50 degrees S to 45 degrees W, 70 degrees S over th e South Pole. The vertical and horizontal directions of wave propagation ar e examined using hodograph analysis in the vertical. Most gravity waves tra nsfer energy upward in the Arctic, while the percentage of downward energy propagation is relatively high in winter and spring in the Antarctic. Horiz ontally, gravity waves propagate westward relative to the mean wind in the Arctic, while in the Antarctic the dominant direction varies from station t o station. The correlation between gravity wave energy in the lower stratos phere and the mean wind is also examined. In the Arctic, gravity wave energ y is highly correlated with the surface wind, though in the Antarctic it co rrelates with the stratospheric wind. These results suggest that gravity wa ves observed in the Arctic are forced by topography, whereas in Antarctica some sources may exist in the stratosphere. One such source candidate is li kely to be the polar night jet.