Scintillometer
Encyclopedia
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
of air caused by variations in temperature, humidity, and pressure. It consists of an optical or radio wave
Radio Wave
Radio Wave may refer to:*Radio frequency*Radio Wave 96.5, a radio station in Blackpool, UK...
transmitter and a receiver at both ends of an atmospheric propagation path. The receiver detects and evaluates the intensity fluctuations of the transmitted signal, called scintillation
Scintillation
Scintillation can refer to:*Scintillation , atmospheric effects which influence astronomical observations*Interplanetary scintillation, fluctuations of radio waves caused by the solar wind...
.
The magnitude of the refractive index fluctuations is usually measured in terms of Cn^2, the structure constant of refractive index fluctuations, which is the spectral amplitude of refractive index fluctuations in the inertial subrange of turbulence. Some types of scintillometers, such as displaced-beam scintillometers, can also measure the inner scale of refractive index fluctuations, which is the smallest size of eddies in the inertial subrange.
Scintillometers also allow measurements of the transfer of heat between the Earth's surface and the air above, called the sensible heat flux http://www.uwsp.edu/geo/faculty/lemke/geog101/miscellaneous/heat_fluxes.html. Inner-scale scintillometers can also measure the dissipation rate of turbulent kinetic energy and the momentum flux.
External links
- The scintillation method by W.M.L. Meijninger, Wageningen University, The Netherlands
- A review of the relationships describing the signal of a Large Aperture Scintillometer - by A.F. Moene, W.M.L. Meijninger, O.K. Hartogensis, W. Kohsiek, H.A.R. de Bruin, Wageningen University, The Netherlands