Geostrophic Adaptation Process and Excitement of Inertial-Gravity Waves in the Stratospheric Spherical Atmosphere
平流层球面大气地转适应过程和惯性重力波的激发

Abstract The observations showed that due to the upward propagation of" quasi-stationary planetu-ry waves, strong gcostrophic motion existed in the stratosphere, which caused strong divergence field and strong, large-amplitude gravity-wave actions during the stralospherif sudden warming in February, 1979. In order to simulate this process, the Hough function is used to structure a linear, harotropic spherical-spectral model. Taking the actual geostrophic deviations at 10 hPa in February 22, 1979 as the initial disturbances, the gcos trophic adaptation process of geoslrophic disturbances during I he stratospheric sudden warming is simulated by using this model. Moreover, the excitement and propagation of gravity waves during the stratospheric sudden warming are also discussed from the variations of divergence field. The simulated result shows that when (he sudden warming occurs in the stratosphere, the pressure field adjusts quickly with the velocity field each other (in the adaptation process, mainly the pressure field is adjusted to the velocity field), and through 2-*" 3 h. a geoslrophic relation between the pressure field and the velocity field is established. Moreover, (he divergence field occurs serious varia lions during the adaptation process, and this may explain that the meitial-gravity wave actions excited in the adaptation process arc serious.