Observation of the lateral fluctuation of the laser beam passing through the atmosphere

Abstract

Lateral fluctuation of the laser spot formed after passing through a distance of 2.26 km above the sea surface was observed together with the air, the surface water temperatures, and the relative humidity. Our main phenomenalistic findings were as follows: (1) a maximum value of the vertical displacement of the beam spot and that of its time rate were 2.1 m and 0.5 m/min, respectively; (2) the ‘large fluctuation,’ the displacement larger than 10 cm, was likely to occur just before the sunrise and, more remarkably, just after the sunset; (3) in each run of observation the frequency of such a large fluctuation seemed to be correlated with the changes in the air temperature and the relative humidity, and (4) an increment of the temperature gradient corresponding to the maximum displacement of 2.1 m was estimated to be 0.77 deg/m.

Energetics of grid turbulence in a stably stratified fluid

“…The velocity fluctuations measured by the optical method may be caused predominantly by the optical distortion induced by the fluctuation of the refractive index in the turbulent, density-stratified water, especially long after the turbulent motion of the fluid particles is damped significantly by stratification. In fact, this has been studied to estimate the 'jitter' of stellar images observed through telescopes (Monin & Yaglom 1975) and to determine the displacement fluctuation of a laser spot (Yokoi 1982) in the lower atmosphere.…”