A scintillometer is a scientific device used to measure turbulent fluctuations of the refractive index of air caused by variations in temperature, humidity, and pressure. It consists of an optical or

radio wave Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (short ...

transmitter and a receiver at opposite ends of an

atmospheric An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

propagation path. The receiver detects and evaluates the intensity fluctuations of the transmitted signal, called

scintillation Scintillation can refer to: *Scintillation (astronomy), atmospheric effects which influence astronomical observations *Interplanetary scintillation, fluctuations of radio waves caused by the solar wind *Scintillation (physics), a flash of light pro ...

. The magnitude of the refractive index fluctuations is usually measured in terms of

C_n^2

, the

structure constant of refractive index fluctuations A structure is an arrangement and organization of interrelated elements in a material object or system, or the object or system so organized. Material structures include man-made objects such as buildings and machines and natural objects such as ...

, which is the spectral amplitude of refractive index fluctuations in the

inertial subrange of turbulence In classical physics and special relativity, an inertial frame of reference (also called inertial reference frame, inertial frame, inertial space, or Galilean reference frame) is a frame of reference that is not undergoing any acceleration. ...

. Some types of scintillometers, such as displaced-beam scintillometers, can also measure the

inner scale of refractive index fluctuations Interior may refer to: Arts and media * ''Interior'' (Degas) (also known as ''The Rape''), painting by Edgar Degas * ''Interior'' (play), 1895 play by Belgian playwright Maurice Maeterlinck * ''The Interior'' (novel), by Lisa See * Interior de ...

, 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 In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. In a dissipative process, energy ( internal, bulk flow kinetic, or system potential) transforms from an initial for ...

and the

momentum flux In engineering, physics, and chemistry, the study of transport phenomena concerns the exchange of mass, energy, charge, momentum and angular momentum between observed and studied systems. While it draws from fields as diverse as continuum mechan ...

References

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 Interferometry {{climate-stub

See also

References

External links