干旱区生态环境知识资源中心

The subject of the work is the role of synoptic conditions in a change in the original polarisation of an electromagnetic field. The depolarisation may be provoked by any inhomogeneities in the structure of the medium. More or less dense volumes are randomly formed by the large number of solid nuclei suspended in humid air and attracting water vapour; especially in the ground atmosphere of the Northern Negev desert, where high levels of coal-se aerosol concentration and humidity are typical. The electrical features of such irregularities are characterised by the permittivity of the suspended grains <(epsilon)over tilde>, which depends on the rate of nuclear moistening. Since <(epsilon)over tilde> differs strongly from the permittivity of clear air, displacement of the incoming wave from its original orientation takes place. The dependence on <(epsilon)over tilde> of the amount of reradiated power (received as an additional field component orthogonal to the primary transmitted signal) is assessed according to the theory of depolarisation and the Rayleigh approximation. After the removal of the less influential meteorological factors (from six recorded parameters), relative humidity is found to be a main parameter influencing depolarisation rate; the rate is observed to be proportional to humidity level.