Rain-Induced Scintillations and Attenuation of Ku-Band Satellite Signals at a Tropical Location

The phenomenon of scintillations in relation to rain attenuation of Ku-band satellite signals has been studied at a tropical location. The standard deviation (σ) of scintillations increases with attenuation up to a value in the range of 6-7 dB, beyond which σ decreases with attenuation. A technique is proposed to obtain some effective values of structure constant (C_n²) of refractive-index variation from the experimental observations of σ and rain rate (R). The value of C_n² also increases with attenuation up to values in the 6-7-dB range and decreases beyond that value. The eddies in turbulent raining medium grow with rain rate, and consequently with attenuation, causing an increase in the outer scale (L_O) of turbulence and thus increasing σ until L_O reaches the size of the first Fresnel zone. In a further development, the contribution of LO toward C_n² decreases, resulting in the decrease of fast fluctuations with rain attenuation.