 Brunt–Väisälä frequency

The Brunt–Väisälä frequency, often denoted as \( N \), is a key concept in atmospheric and oceanic sciences that quantifies the stability of a stratified fluid, such as the atmosphere or the ocean. It measures the frequency at which a displaced parcel of fluid will oscillate if it is perturbed vertically. This frequency is dependent on the density stratification of the fluid and can be calculated from the vertical gradient of buoyancy or potential density.