Model for estimating the refractive-index structure constant in clear-air intermittent turbulence.

We explain discrepancies in comparing estimations of the refractive-index structure constant C(n)(2) in clear air by means of different techniques by taking into account atmospheric intermittency effects. We formulate a model of C(n)(2) in intermittent turbulence on the basis of the Tatarskii theory, and we calculate the mean value of C(n)(2) through a probabilistic approach. We deduce a factor, which gives a measure of the statistical reduction of turbulence that is due to intermittency, within the model framework. A procedure for estimating the mean value of C(n)(2) from data of a specific radiosonde observation is illustrated.

Ground level refractivity and scintillation in space-earth links.

Slant-path scintillations are investigated by means of measurements at microwaves made in Rome and Beijing using the SIRIO satellite. Comparison with ground level temperature, humidity, and radio refractivity is performed, and close similarity is found with daily and seasonal behavior of the scintillations. An explanation of this similarity is proposed that leads to simple empirical relationships between the scintillation intensity and the ground level quantities. The intensity of scintillations has been also estimated using meteorological radiosonde measurements, and satisfactory agreement is found with simultaneous direct scintillation measurements.