Scintillometers measure the intensity fluctuations of a continuously emitting light source. A receiver unit measures the intensity fluctuations caused by the turbulence between source and receiver. Thus it is possible to determine the integrated turbulence over the measuring distance. With the commercial measuring instruments available today, time resolutions of 1 minute are possible. For distances between 50 m and 250 m laser scintillometers are used. For larger distances up to 12 km so-called Boundary Layer Scintillometers (BLS) are used. The turbulence close to the ground is measured at a height of 1.2 m above the ground at a horizontal distance of 75 m at a wavelength of 670 nm.