World Maps of Atmospheric Refractivity Statistics

Atmospheric refractivity and its vertical gradient affect electromagnetic wave propagation in the atmosphere. Consequently, their statistics are needed for propagation predictions. New world maps of refractivity and its vertical gradient statistics are derived from a global, long-term dataset of meteorological quantities as given by ERA-Interim reanalysis. The derived maps provide long-term statistics obtained from 33 years of meteorological data with a one-degree spatial resolution on a latitude/longitude mesh. A processing method is described and examples of the derived maps are shown. The consistency of the new maps is checked by comparing world maps provided by ITU-R. Accuracy is tested by comparing refractivity statistics obtained from high-quality local measurements using radiosonde and tower measurements. New global maps demonstrate enhanced statistical stability, spatial resolution, and accuracy.