复杂大气条件对微波传播衰减的影响研究

摘要

为了进一步提高大气对微波传播衰减影响的描述精度,为微波链路遥感反演大气新应用提供理论基础,该文系统性研究了大气主要吸收气体和各种大气粒子对微波传播的衰减情况.利用ITU-R模型计算大气主要气体成分对微波的吸收衰减,然后在降水粒子、云雾粒子和沙尘粒子的介电模型、形状、相态和谱分布的基础上,计算得到群粒子对微波的衰减特性,系统讨论降水强度、相态、含水量、谱分布、气压和温度等因素对微波传播衰减的影响.数值模拟结果表明,大气主要气体成分在60 GHz,180 GHz和320 GHz附近存在强烈的吸收带,其衰减系数与水蒸气含量和气压呈正相关,与温度呈负相关;降水强度、谱分布、相态以及冰水比例对降水的微波衰减存在不同程度的影响,云雾的含水量和相态,沙尘的数密度、谱分布和含水量是影响微波衰减的主要因素,而温度的影响较小;大气各因素的衰减系数从大到小依次为爆炸沙尘、降水、气体吸收、水雾、冰雾和自然沙尘.%To describe the effect of atmospheric conditions on the microwave propagations precisely, establish the theoretical foundation for the new applications of the atmospheric inversion by microwave links, the propagation attenuation by the absorptive gas and various atmospheric particles are investigated systematically in this paper. The absorption of main gas component in atmosphere are calculated by ITU-R model, and then based on the physical characteristics and dielectric model of different types of precipitation particles, cloud and fog particles, and sand particles, the scattering characteristics of atmospheric particles cluster at the microwave band are calculated, the effect of particle size distribution, intensity, phase, and temperature on the microwave propagation at different waveband are discussed systematically. The numerical simulation results show that there are absorption band at 60 GHz, 180 GHz, and 320 GHz due to oxygen and vapor, and the attenuation is positively related to both the vapor content and air pressure, while it is negatively related to the temperature. The microwave propagation attenuation by precipitation are mainly influenced by the precipitation intensity, particles size distribution, phase and its component rate, the water content and phase of cloud and fog are the main factors that affect the microwave attenuation, the number density, size distribution and water content of dust are the main factors that affect the microwave attenuation, while the temperature is the least factor. In sum, in order of the attenuation coefficient, it goes:blast dust, precipitation, gas absorption, water fog, ice fog, and atmospheric dust.