Meteorological Instrument Performance Characteristics

General Characteristics of Measurements » Homogeneity

Homogeneity refers to similarity of a particular characteristic over some interval in space or time. There can be considerable variability in underlying properties of a measured quantity, as in a turbulent field, but the field itself may be homogeneous if the characteristics of the turbulence are similar over some interval. There is a relationship between homogeneity and representativeness. It is easier to make representative measurements of a homogeneous characteristic; for example, one sounding may represent conditions over a large area away from particular weather features but may miss important structure if there are weather systems causing significant variations between sounding stations.

As an example of horizontal homogeneity, weather conditions will have the same characteristics regardless of from which direction they are advected within this field of view.

As an example of horizontal homogeneity, weather conditions will have the same characteristics regardless of from which direction they are advected within this field of view. Image from R. Clark.

Over a uniform surface and with constant wind, an atmospheric boundary layer develops that has homogeneous properties. However, if the wind then carries the air over land having different properties, the properties of the boundary layer change as it moves toward a different structure that would form over the new surface. The result is the formation of an "internal boundary layer" that increases in depth with distance downwind from the land-surface change.

Depiction of the downwind propagation of internal boundary layers affecting a measurement tower

Depiction of the downwind propagation of internal boundary layers affecting a measurement tower. Image from NCAR/EOL.