A scintillometer is a
scientific
Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. Modern science is typically divided into twoor threemajor branches: the natural sciences, which stu ...
device used to measure
turbulent
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between ...
fluctuations of the
refractive index
In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
of
air
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
caused by variations in temperature, humidity, and pressure. It consists of an
optical
Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...
or
radio wave
Radio waves (formerly called Hertzian waves) are a type of electromagnetic radiation with the lowest frequencies and the longest wavelengths in the electromagnetic spectrum, typically with frequencies below 300 gigahertz (GHz) and wavelengths g ...
transmitter and a receiver at opposite ends of an
atmospheric
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosphere ...
propagation path. The receiver detects and evaluates the intensity fluctuations of the transmitted signal, called
scintillation.
The magnitude of the refractive index fluctuations is usually measured in terms of
, 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.
Inner-scale scintillometers can also measure the
dissipation rate of turbulent kinetic energy and the
momentum flux.
See also
*
Transmissometer
*
Nephelometer
References
External links
The scintillation methodby 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
Interferometry
{{climate-stub