Energy Flux from Traveling Hurricanes to the Oceanic Internal Wave Field

Abstract

The generation of long interval waves by traveling hurricanes on an f plane is studied within the context of linear theory. The emphasis of the present work is on the interval wave power, that is, the fraction of the energy input from the hurricane that is absorbed by the internal wave field in the ocean. Particular attention is paid to the dependence of the interval wave power on the hurricane speed, the oceanic stratification, and the Coriolis parameter. A formula for the wave power, expressed in terms of the wind-forcing spectrum, is derived. The wave power can be divided in two parts: one part generated by the divergence of the wind stress and one part generated by the curl of the wind stress. The latter part, which is dominating for hurricanes, is always decreased when the strength of the stratification is increased, while the former part may either increase or decrease depending on the speed of the hurricane. It is shown that, for a specified stratification and a fixed latitude, the wave power exhibits a maximum for a certain speed of the hurricane. The maximum occurs when the forcing is optimally tuned with the internal waves. When the strength of the stratification is increased, the maximum is found at a higher hurricane velocity, and the wave power is generally reduced. An estimate, based on the derived results, of the global energy flux from hurricanes to the internal wave field is presented. An average energy flux of the order 1010 watts is suggested by this calculation.