Multiple scattering and attenuation for electromagnetic wave propagation in sand and dust atmosphere

Abstract

For an electronic system operation under the conditions of all-weather in arid and semiarid areas, the studies of the attenuation and multiple scattering are necessary for electromagnetic wave propagations in sand and dust atmosphere. Based on Mie theory, a method of calculating the attenuations for electromagnetic wave propagation through sand and dust atmosphere is presented in this paper, which relate to the particle size distributions and visibilities for sand and dust atmosphere. The attenuations at 37 GHz are given for various visibilities, and are compared with the results calculated from other formulas and the experimental data from the literature. The attenuations are closer to the experimental results. In order to investigate into electromagnetic wave propagations in lower visibility sand and dust atmosphere, the multiple scattering in sand and dust storms are necessarily analyzed. At 37 and 93 GHz, the extinction cross sections, albedos and asymmetry factors are calculated by Mie theory for various size sand and dust particles. By the Monte Carlo (MC) simulation method, the attenuations for including the multiple scattering effects are calculated under the conditions of dry and 5% water content in sand and dust particles, respectively, and are compared with the results from Mie theory. The results are shown that the difference between the attenuation obtained by Mie and that by MC is small at 37 GHz. The influence of the multiple scattering on attenuation is small and may be ignored at 37 GHz. At 93 GHz, the difference between the attenuation obtained by Mie and that by MC is clear, and the attenuation obtained by using Mc simulation is smaller than that based on Mie theory. The effect of the multiple scattering on attenuation is evident at 93 GHz. The lower the visibility, the more notable the effect on attenuation is. For different sand and dust storms, the particle refractive indexes and the particle size distributions are different. For the sand and dust storms in Tengger desert and the blowing sand and dust atmosphere in north China, the attenuations at 93 GHz are analysed. In Tengger desert, the attenuation and the multiple scattering are larger than in blowing sand and dust atmosphere. The results show that the more the large size particles in sand and dust storms, the stronger the effect multiple scattering on attenuation is. Hence, for stronger sand and dust storms, the attenuation and the effect of multiple scattering become important. With the increase of water content in particle, the imaginary part of refractive index increases, the attenuation greatly increases, and the effect of the multiple scattering on attenuation is weakly varied. The analyses show that the attenuations for electromagnetic wave propagation in arid sand and dust atmosphere are smaller than in moisture sand and dust atmosphere under the condition of the same visibility.