RADAR OBSERVATIONS OF AN INERTIA-GRAVITY WAVE IN THE TROPOSPHERE AND LOWER STRATOSPHERE

Radar measurements at Aberystwyth (52.4-degrees-N, 4.1-degrees-W) during 25-27 June 1990 have been used to examine the characteristics of an inertia-gravity wave. Above the tropopause, hodographs of horizontal perturbation velocity derived for 2.4-h time intervals show clockwise rotation with increasing height, corresponding to upwards propagation of energy, and vertical wavelengths of 1.5-2.6 km. Below the tropopause, the results are not as distinct but the majority of hodographs show anticlockwise rotation. A complementary rotary spectral analysis carried out for the full 2-day observation period shows that clockwise circular components dominate over anticlockwise components above the tropopause for vertical wavelengths in the range 1-7 km. This analysis also shows the presence of saturation in this height range for vertical wavelengths up to about 1.5 km. Again, the results for heights below the tropopause are not as clear. From the spectral results, together with information on the direction of wave propagation inferred from the hodographs and from estimates of the vertical flux of horizontal momentum, the source of the wave is tentatively identified as a jet stream to the north.