Влияние кластеров на рассеяние микроволнового излучения в сухом снеге

Abstract

In this work, the frequency dependence of the scattering coefficient of microwave thermal radiation in freshly fallen, fine-grained and coarse-grained dry snow is studied. At frequencies of 22.2, 37.5, 60 and 94 GHz, the dependences of reflectivity and transmissivity of the snow layer on the layer thickness, size and volume density of the particles were measured. The experimental dependences of the reflectivity and transmissivity on the layer thickness were approximated by the relations of the two-flux Kubelka-Munch theory. From experimental results, it is followed that the frequency dependence of the scattering coefficient strongly depends on the range of frequencies considered. Calculations of the scattering coefficients of a snow-like medium were carried out using the Mie theory, taking into account that the complex dielectric constant of the medium is increased and the correlation size of particles is decreased with increasing medium density. From comparison of experimental data for freshly fallen and fine-grained snow with the results of calculations based on the Mie theory, it is followed that the exponent of the frequency dependence of the scattering coefficient is anomalously low in the frequency range 22.2...37.5 GHz, and at the frequency of 94 GHz the radiation is scattered in accordance with the Rayleigh equation. Using the Rayleigh equation, it was established that anomalous scattering at frequencies of 22.2...37.5 GHz is caused by clusters with scales that can exceed of freshly fallen snow scatterers at frequency of 94 GHz by more than 3 times, and the size of fine-grained snow scatterers at frequency of 94 GHz by more than 2 times. It is shown that the influence of clusters on radiation scattering decreases with increasing snow density.