Abstract: When spreading abroad in the troposphere, it is hard to avoid that electromagnetic wave is reduced because of the influence of atmosphere mote, in which precipitation is the most familiar and the major element is rain. Some research is done on the physical character of dielectric constant of water. Using the Matlab, Mie theory and the Laws-Parsons model of rain distribution are used to analyze the relationship of electromagnetic wave attenuation with rainfall change. The infection on absorption and dispersion of electromagnetic wave is considered. The attenuation of rainfall is educed by the calculation of signal-to-noise.

Key words: electromagnetic wave attenuation, Mie theory, rainfall absorption