From AMS Glossary
- In the field of atmospheric turbulence and boundary layers, often used as a contraction for flux density; namely, the flow of a quantity per unit area per unit time. These fluxes can be defined in two forms: dynamic and kinematic. The dynamic flux of a quantity is the flow of that quantity per unit area per unit time, where often the word dynamic is assumed if it is not explicitly stated. The advantage of a kinematic flux is that it has units that are more easily measured by a conventional meteorological instrument. The units are usually a velocity (m s-1) times a temperature (K), specific humidity (kgwater/kgair), or wind speed (m s-1).