Statistics of liquid water path in cloud, and slant path propagation loss in cloud at V-band, based on measurements at Chilbolton

Communication systems that make use of slant path propagation to satellites or high altitude platform stations (HAPS) experience signal loss as a result of rain and cloud along the path. Propagation loss in rain is a well-researched area with the impact being felt at most microwave frequencies. Clouds typically consist of much smaller liquid and ice particles so that significant loss is not experienced by signals at frequencies lower than Ka-band. Microwave attenuation in cloud results from Rayleigh scattering so that it is possible to predict levels of attenuation if the integrated liquid water amount along the propagation path is known. (Cloud ice particles are not a significant cause of signal attenuation at microwave frequencies.) To assess, and possibly improve, the performance of existing prediction models of slant path loss at frequencies up to 100 GHz, measurements made at the Chilbolton observatory have been used to obtain an understanding of cloud related signal attenuation.