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How do atmosphere and rain attenuate signals?

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Above a few GHz, signals are attenuated by atmospheric gases and hydrometeors. Water vapor absorbs near 22.2 GHz and 183 GHz; oxygen absorbs strongly around 60 GHz (roughly 15 dB/km at sea level) and at 119 GHz; these are modeled by ITU-R P.676.[1] Rain attenuation is modeled as specific attenuation γ = kRα dB/km, where R is rain rate in mm/h and k, α depend on frequency and polarization, per ITU-R P.838.[2]

How significant is rain at different frequencies?

Below about 5 GHz rain attenuation is minor for most links; at Ku-band it can be several dB during heavy rain; at Ka-band and above it dominates availability planning, with fades of 10–20 dB or more at high availability targets in rainy climates. ITU-R P.618 combines these models for Earth–space paths and P.530 for terrestrial links.[3][2]

How do antennas cope?

Higher-gain antennas, adaptive coding and modulation, uplink power control, site diversity, and choosing lower bands for high-availability services. Wet radomes and reflector surfaces also add loss; see radomes.[4][5]

Why use 60 GHz at all?

Oxygen absorption limits interference range, allowing dense frequency reuse for short links and indoor systems, and wide spectrum is available.[1][6]

Frequently asked questions

Does fog attenuate microwaves?

Cloud and fog add attenuation at mmWave, modeled by ITU-R P.840, but less than heavy rain.

Is horizontal polarization affected more by rain?

Yes; oblate raindrops attenuate horizontal polarization slightly more.

What is rain fade?

Temporary signal loss caused by rain along the path.

References

Online sources accessed October 21, 2026; printed works cited by edition. See all sources.

  1. “Recommendation ITU-R P.676: Attenuation by atmospheric gases and related effects”. ITU-R. current edition.
  2. “Recommendation ITU-R P.838: Specific attenuation model for rain for use in prediction methods”. ITU-R. current edition.
  3. “Recommendation ITU-R P.618: Propagation data and prediction methods required for the design of Earth-space telecommunication systems”. ITU-R. current edition.
  4. “Satellite Communications Systems, 5th ed.”. G. Maral and M. Bousquet, Wiley. 2009.
  5. “Analysis of Radome-Enclosed Antennas, 2nd ed.”. D. J. Kozakoff, Artech House. 2010.
  6. “Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!”. T. S. Rappaport et al., IEEE Access, vol. 1, pp. 335-349. 2013.
Categories: Propagation