Weather Radar Fundamentals


Common Clear Air Phenomena » Non-Meteorological Returns » Smoke and Chaff


Smoke from wildfires or industrial sources can often show up on radar if it rises high enough into the troposphere. Often you can confirm that the echoes are from smoke plumes by looking at satellite data.

Usually, smoke has these characteristics on radar images:

  • Low reflectivity (<20 dBZ)
  • The echo elongates over time in the direction of the wind
  • The echo will persist in the location of the source
  • Radial velocity will indicate the prevailing wind direction and speed, as smoke particles act as tracers

A similar radar reflectivity return can occur when chaff has been released during nearby military exercises. Chaff is small, highly reflective particles that aircraft release to confuse other radar and targeting systems. These narrow echoes will travel in the same direction as the wind, and will not persist in a source location like smoke will. Chaff is most common near air bases and other military installations.