In this paper, at first an empirical formula for calculating the extinction cross section(ECS) by rain drops over a broad frequency range is derived based on extensive calculations made on a widely varying in mean radius of modified Pruppacher and Pitter rain drop models. This formula thus provides a simple and inextensive method for calculating the attenuation of rain drops, which otherwise requires complicated, tedious and extensive methods of calculations. Based on the study by isotropic or an isotropic spherical wave expansion, the specific rain attenuation equation was introduced.By implementing the empirical formula of ECS into the rain attenuation equation, a new numerically imperical formula for the calculation of specific rain attenuation is also established. The validity of the empirical formula for calculating the specific rain attenuation is also verified by comparing the obtained results of specific rain attenuation with those obtained by different researchers found in literature.
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