Backward and forward scattering of microwaves by ice particles: A review

Abstract

Approximate and exact mathematical techniques for the calculation of the scattering properties of a single ice particle are first reviewed. Then, for dealing with practical applications such as radar meteorology or radio wave transmission along earth‐space links, the problem of the scattering by an assembly of particles is examined. This problem involves the knowledge of the particle size distribution and of the orienting mechanisms which can affect the ice crystals in the clouds. Although the T matrix formalism has been successfully used in a greater range of scattering problems than the other techniques, the Rayleigh approximation may be used with confidence for calculating the cross‐polarization properties of radio waves at frequencies up to at least 25 GHz. Alignment of ice particles is not expected to occur in high‐altitude cirrus clouds while alignment is observed in strong thunderstorms. Thus different models are to be used in order to predict the cross polarization along earth‐space links.

Time-varying ice crystal orientation in thunderstorms observed with multiparameter radar

“…Furthermore, it has been established that in the absence of electric fields in cumulonimbus clouds ice crystals, plates and columns, can be expected to fall with their semimajor axes narrowly distributed around the horizontal [25], [27]. There is a suggestion that alignment of crystals in the horizontal plane with semimajor axes parallel, what is described by Mon [28] as three-dimensional alignment, is even easier to achieve [25]. Turbulence does not significantly disrupt the crystal's general horizontal orientation arising from aerodynamical forces and the crystals will reassume a horizontal orientation in a time on the order of 10 ms after being released from any orientation [27].…”

“…Observations of Florida thunderstorms were collected by the upgraded CP-2 radar on six days in 1991: 25,28,and 29. Approximately 2 h of data were collected in the fixed dwell mode alone.…”

Calculation of ice depolarization on satellite radio paths

“…Several methods are available for calculating the scattering from individual ice particles [Mon, 1982;Yeh et al, 1982]. The flexibility introduced by using sophisticated computational methods is not required in most situations because of the lack of information on ice particle sizes and shapes.…”

Scattering by single ice needles and plates at 30 GHz

“…To understand the causes for the observed depolarized signals from ground-satellite communication links or to be able to predict the strength and the occurrence of the depolarization of such signals, a number of research efforts have been initiated, worldwide [Holt, 1982;Mon, 1982;Oguchi, 1981;Fang and Lee, 1978;Evans and Holt, 1977;Dissanayake et al, 1980;Bostian and Allnutt, 1979;Yeh et al, 1982;Bringi and Seliga, 1977]. Through these efforts a great many data have been generated, and certain interpretations given.…”

“…Through these efforts a great many data have been generated, and certain interpretations given. For example, in several recent review articles, Bostian and Allnutt [1979] and Mon [1982] summarized what was known and what was not yet understood about ice crystal depolarization, while Oguchi [1981], Holt [1982], and Yeh et al [1982] provided summaries of depolarization of the signal due to raindrops.…”