Density gradient is a spatial variation in density over an area. The term is used in the natural sciences to describe varying density of matter, but can apply to any quantity whose density can be measured.
Aerodynamics
In the study of supersonic flight, Schlieren photography observes the density gradient of air as it interacts with aircraft.
Water
A steep density gradient in a body of water can have the effect of trapping energy and preventing convection, such a gradient is employed in solar ponds. In the case of salt water, sharp gradients can lead to stratification of different concentrations of salinity. This is called a Halocline.
The CsCl/EtBr gradient centrifugation method fractionates DNA and RNA molecules based on their density, where EtBr labels the nucleic acid bands.3 Scientists have used this technique to extract large ...