Microphysical Interpretation of Multiparameter Radar Measurements in Rain. Part III: Interpretation and Measurement of Propagation Differential Phase Shift between Orthogonal Linear Polarizations

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  • 1 Illinois State Water Survey, Champaign, IL 61820
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Abstract

As radar waves having different polarizations propagate through a collection of nonspherical oriented hydrometeors, a phase difference between the waves appears. In a collection of uniformly horizontally oriented quiescent water drops, the rate of change of the propagation differential phase shift with increasing distance from the radar is proportional to the product of the liquid water content and the departure from unity of the mass-weighted mean axis ratio of the drops provided the radar wavelength is much larger than the drops. The appropriateness however, of such a simple relation to natural rain 'in which some drops assume complex shapes and a variety of orientations through the processes of collision, coalescence, break-up and oscillation remains to be determined.

Abstract

As radar waves having different polarizations propagate through a collection of nonspherical oriented hydrometeors, a phase difference between the waves appears. In a collection of uniformly horizontally oriented quiescent water drops, the rate of change of the propagation differential phase shift with increasing distance from the radar is proportional to the product of the liquid water content and the departure from unity of the mass-weighted mean axis ratio of the drops provided the radar wavelength is much larger than the drops. The appropriateness however, of such a simple relation to natural rain 'in which some drops assume complex shapes and a variety of orientations through the processes of collision, coalescence, break-up and oscillation remains to be determined.

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