Evidence of long-term correlation between clear-air attenuation and scintillation in microwave and millimeter-wave satellite links

Long-term correlation between microwave scintillation and path attenuation in clear-air troposphere is quantitatively evaluated carrying out a numerical and experimental analysis on a monthly basis. Amplitude scintillation variance is simulated by means of a weak-fluctuation propagation model, while path attenuation is obtained from ground-based brightness temperature data using a radiative transfer model. Both the scintillation and radiative transfer models are applied to a set of radiosounding observations, performed in Milan, Italy, during 1989. Regression formulas relating clear-air mean radiative temperature to meteorological quantities and slant-path attenuation to amplitude scintillation variance are derived from numerical simulations. Their validity should be restricted, in general, to mid-latitude subcontinental climates. Monthly predictions of radiometer-derived path attenuation and correlation between attenuation and scintillation are tested using both multichannel radiometric data and Italsat beacon measurements at 18.7, 39.6, and 49.5 GHz, acquired at Spine d´Adda, Italy, ground station in 1995. A fairly good agreement is found by performing a comparison between estimates and measurements