Rain Effects on Propagation

• Terrestrial LOS paths – Rec. P.530

• Earth-space paths – Rec. P.618

• Attenuation

  • concept of effective path through the rain
  • horizontal and vertical structure

• Depolarisation

  • function of co-polar attenuation

• Rain scatter as interference mode – Rec. P.452

• All use model of Rec. P.837

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Effects of rain must be taken into account in propagation prediction methods used in service planning. Two examples are given:

• Rec. P.530 for LOS microwave links

• Rec. P.618 for Earth-space paths

• Both contain well-known rain attenuation prediction method based on concept of deriving the effective length of the path through the rain – the effective path taking account of the spatial non-uniformity of rain, both horizontally and vertically, along the path.

• For XPD, model based on relation with co-polar attenuation.

• Recs also address frequency scaling of attenuation and depolarisation effects when measurement data are available at one frequency but required for another.

• Rec. P.452 gives a prediction method for signals scattered from rain cells. This mode must be taken into account in a detailed assessment of potential interference mechanisms between two points on Earth’s surface – i.e. along with modes such as super-refractivity and ducting.

• In all cases, prediction methods refer to Rec. P.837 as source of rain intensity data.