Mischschicht

Mischschicht (literally "mixed layer") is a term used in atmospheric science, oceanography and engineering to denote a near-surface zone whose physical properties are rendered relatively homogeneous by turbulent mixing. In each field it describes a transition region where momentum, heat, moisture or material constituents are rapidly redistributed, producing distinct dynamical and thermodynamic behavior compared with adjacent layers.

In meteorology the Mischschicht refers to the convective portion of the planetary boundary layer that is well mixed in potential temperature and moisture during daytime. Its depth varies with surface heating, wind shear and mesoscale forcings; it controls the vertical distribution of pollutants, cloud formation and the exchange of heat and momentum between the surface and free atmosphere. Typical observational methods include radiosondes, sodar/ lidar profilers and remote sensing.

In oceanography the mixed layer is the upper ocean layer with nearly uniform temperature and salinity produced by wind-driven turbulence and buoyancy fluxes. Mixed layer depth (MLD) is a key parameter for sea surface temperature variability, primary productivity and air-sea gas exchange; it undergoes seasonal and storm-driven changes and is limited below by an entrainment zone.

In engineering and materials science, Mischschicht denotes a mixing or transition zone formed during welding, coating or multilayer deposition where diffusion and mechanical mixing produce compositional gradients. Across disciplines the concept emphasizes the role of turbulence and transport in setting layer structure and exchanges.