Look up at the sky on a cloudy day, and you often see sets of parallel, equally spaced bands of clouds that are the signature of a type of wave known as an internal wave. Although visible under only the right conditions, internal waves are ubiquitous in both the atmosphere and the ocean. In many dynamical systems, waves release excess energy in a fluid that is displaced from its lowest-energy, balanced state. Internal waves extract and transport energy three-dimensionally before releasing it to large-scale circulation.
Historically, researchers thought that only mechanical forcing or direct thermal displacement of the system from its balanced state could generate internal waves. However, more recent work shows that a spontaneous imbalance of the fluid system can generate or amplify them without any direct forcing. The discovery has led to new perspectives on the role of waves in the circulation of the atmosphere and ocean. (For...
