Stev F. Clifford

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Stellar scintillations, when appropriately analyzed, yield information about the turbulence throughout the atmosphere. We describe an instrument involving a 36-cm telescope and an on-line minicomputer that provides, after 20 min of observation, the refractive-turbulence profile of the atmosphere. The height resolution is sufficient to divide the atmosphere(More)
We report the successful construction and testing of an optical wind sensor that uses the motion of the scintillation pattern to measure the transverse component of wind blowing across a laser beam. As is done for measuring ionospheric and interplanetary winds, we use a correlation method. However, in our application, the slope at zero lag of the(More)
We demonstrate the feasibility of using a naturally illuminated scene, such as a hillside or forest, as a passive optical source to measure the path-averaged crosswind between the scene and the observer. The resultant path weighting function for the crosswind cannot be varied arbitrarily, but we can obtain a useful range of weighting functions by adjusting(More)
A new, rigorous approach is presented for the computation of the fluctuating field of a monopole source in a nonrefracting, turbulent atmosphere above a ground surface. The time-averaged sound pressure level is considered, as well as statistical distributions of the sound pressure level. The computation is based on the Rytov solution of the wave equation(More)
The theory of optical propagation through atmospheric turbulence demonstrates the sensitivity of such quantities as log-amplitude variance and covariance to strength of refractive turbulence and transverse wind. We exploit this sensitivity by using a crossed-path technique to derive path profiles of these quantities. The results are insensitive to changes(More)
We describe a technique for measuring path-averaged rain parameters by analyzing the rainfall-induced scintillations of a laser beam. From the time-lagged covariance function of two vertically spaced line detectors, we determine the average rainfall rate and drop-size distribution along the optical path. This technique requires no prior assumption of the(More)
The problem of light depolarization in a turbulent atmosphere is revisited by means of coupled-mode theory [D. Marcuse, Theory of Dielectric Optical Waveguides (Academic, New York, 1974)]. This allows, in particular, evaluation of the depolarization ratio for a plane wave and comparison of its expression with the one obtained in the frame of two distinct(More)
We have developed a physically based extension of the first-order perturbation theory of optical scintillation that accounts for the observed variance and covariance of the amplitude fluctuations in strong integrated turbulence. We use this model to analyze the experimentally observed changes in the operation of our laser wind sensor. The theory suggests a(More)
The interference of the direct wave from the point source to the receiver and the wave reflected from the impedance ground in a turbulent atmosphere is studied. A parabolic equation approach for calculating the sound pressure p at the receiver is formulated. Then, the parabolic equation is solved by the Rytov method yielding expressions for the complex(More)