The Role of Rain Drop Size Distribution on Specific Attenuation at Microwave Frequencies

Jamel . Al-Jumaily, Kais

	The Role of Rain Drop Size Distribution on Specific Attenuation at Microwave Frequencies
Al-Mustansiriyah Journal of Science
Article 1, Volume 19, Issue 1, 2008, Pages 76-86
Author
Kais Jamel . Al-Jumaily
Abstract
A fundamental quantity in the calculation of rain attenuation statistics is the specific attenuation (attenuation per unit distance). The power-law form of rain specific attenuation is very convenient and is commonly used . The aim of this research is to investigate the role of the rain drop size distribution on the computation of the rain specific attenuation. Calculations rain specific attenuation were carried out for the frequency range of 5 to 100 GHz and for horizontally, vertically and circularly polarized waves. These calculations were based on four commonly used rain distributions. The results showed that for all types of rainfall rate, the rain specific attenuation is almost independent of the rain drop size distribution when the frequency is less than about 30 GHz. As the frequency increases beyond this value, the rain specific attenuation becomes sensitive to the rain drop size distribution. The results also showed that Gamma and Marshall-Palmer distributions cause more attenuation than the other two distributions. It was found that in the case of light rain, Marshall-Palmer rain drop size distribution is the dominant distribution. Gamma distribution is the most effective distribution in heavy to very heavy rainfalls. The results demonstrated that, horizontal polarized waves are attenuated the most, vertical polarization shows the least attenuation while circular polarization is in the middle of these two

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