Observational and Modeling Study of Stratospheric Gravity Waves Induced by a Typhoon

Typhoons are intense convective weather systems and a significant source of gravity waves. The gravity waves they excite can propagate upward into the middle atmosphere. This study primarily analyzes the characteristics of gravity waves generated by typhoons to understand their impact on the middle atmosphere. Analysis based on AIRS data reveals that a Typhoon also produced semi-circular arc-shaped disturbances at altitudes of 20–40 km, and these disturbances can propagate thousands of kilometers into the stratosphere. Analysis of atmospheric vertical wind from model simulation outputs indicates that while the typhoon possesses the energy to induce gravity waves in all directions within the troposphere, the wave disturbances at 20–40 km altitudes manifest as a semi-circular arc concentrated to the east of the typhoon center. The westward background wind field and wind shear at 20–40 km play a crucial modulating role in the vertical propagation of gravity waves, gradually filtering out westward-propagating waves during their upward journey. Consequently, at 20–40 km, the strongest energy propagation direction of the induced gravity waves is due east. The gravity wave parameters including horizontal wavelengths, vertical wavelengths and periods are estimated by wave spectrum analysis.