Impact of typhoon-generated gravity waves in the typhoon development

As a first attempt to understand the impact of typhoon-generated gravity waves (TGWs) on typhoon development, Typhoon Saomai (2006) is simulated and effects of TGWs on background flows are examined by considering momentum flux. The momentum flux of TGWs and its vertical divergence/convergence are larger during the developing stage than during the mature and decaying stages of the typhoon. In the developing and mature (decaying) stages of the typhoon, TGWs act to decrease (increase) vertical wind shear, which is known to inhibit a typhoon's intensification. Thus, TGWs can help a typhoon intensify when the typhoon develops. Upper-level divergence increases notably before a typhoon enters both rapidly-developing and mature stages. A significant portion of upper-level divergence is found to be due to TGWs.