# Coherent structures

From AMS Glossary

## coherent structures

Three-dimensional regions in a turbulent flow with characteristic structures and lifetimes in terms of velocity, temperature, etc., that are significantly larger or longer-lived than the smallest local scales.

Much of the turbulent transport, conversion of mean flow energy into turbulent eddies, nonlinear transfer into smaller scales, and eventual dissipation is associated with coherent structures. Examples include gust microfronts and horseshoe vortices in the surface layer, convective plumes, and longitudinal roll vortices.

*See*longitudinal rolls, convective plume, Langmuir circulation.Etling, D., and R. A. Brown 1993. Roll vortices in the planetary boundary layer: a review. Bound.-Layer Meteor.. 65. 215–248.

Foster, R. C. 1997. Structure and energetics of optimal Ekman layer perturbations. J. Fluid Mech.. 333. 97– 123.

Gerz, T., J. Howell, and L. Mahrt 1994. Vortex structures and microfronts. Phys. Fluids. 6. 1242–1251.

Wilczak, J., and J. Tillman 1980. The three-dimensional structure of convection in the atmospheric surface layer. J. Atmos. Sci.. p. 2424.