# 221

221, also known as *AVHRR False Color*, is the most basic visible-light enhancement available for most of the polar-orbiting main radiometers.

The name 221 comes from the usage of AVHRR channel 2 (0.63 µm) in the red and green position, and 1 (0.862 µm) in the blue position.

### Appearance

Land appears yellow (vegetated areas) or gray (deserts), while sea appears deep blue or black. 
Snow and ice appear white, including sea ice.
Clouds appear white.
Fog appears violet-white, but is hard to see.

### Intended usage

General purpose imagery at daytime.

### Limitations

Hard to determine the cloud nature.
Hard to discriminate between cirrus clouds and fog.