Channel 5 of the AVHRR is located within the part of the spectrum where Earth's emission dominates all the time. It is most sensitive to wavelengths between 11.5 um and 12.5 um.

You can use this imagery all times of the day to:

- Estimate brightness temperatures of land, sea and cloud tops.
- Detect cloud types (always compare with other channels to help determining cloud type.
- Channel 5 is slightly more sensitive to low-level watervapor than channel 4. You can use that aspect to do the following:
  - Use the differences to estimate the amount of low-level moisture in the atmosphere.
  - Take a linear combination of the two channels to remove the cooling effects of low-level moisture thereby retrieving more accurate sea surface temperatures. (e.g., 1.5(ch 5) - .5(ch 4)) = SST + adjustment factors
  - Clouds in temperature inversions (e.g., fog) have a different signal compared to clouds in other temperature profiles.
- Also use the differences to differentiate active convection from cirrus. Ch 5 is usually cooler than Ch 4 except above convective precipitating clouds where the differences are usually close to zero.
- Volcanic ash has a strong signal difference between Ch 4 and Ch 5.

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