Variability inPropagation Medium

• Climate

  • temperature, pressure, water vapour
  • rain intensity
  • cloud cover

therefore:

• dependent on region and season

  e.g. temperate, tropical, equatorial
  

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• When discussing propagation, important to appreciate concept of natural variability – behaviour of propagation will not be the same everywhere because of natural variability of propagation medium.

• When the propagation medium is the neutral atmosphere, climate is all important
  • T, P, e govern refractive effects
  • precipitation and cloud cause attenuation and scattering

• Such climatic parameters display
  • significant temporal variability – one year is unlikely to be like the next
  • significant regional variability – great differences between temperate and low latitudes.

• Such differences are often reflected in statistical representation of propagation data, e.g. annual or worst month values for a particular region.