False Color: Red = M11, Green = I2, Blue = I1

This combination is most useful for distinguishing burn scars from naturally low vegetation or bare soil and enhancing floods.

This combination can also be used to distinguish snow and ice from clouds. Snow and ice are very reflective in the visible part of the spectrum (Band I1), and absorbent in Bands I2 (near infrared) and M11 (short-wave infrared, or SWIR). Thick ice and snow appear vivid sky blue, while small ice crystals in high-level clouds will also appear blueish, and water clouds will appear white.

The Visible Infrared Imaging Radiometer Suite (VIIRS) Corrected Reflectance imagery is available only as near real-time imagery. The VIIRS instrument in on board the joint NASA/NOAA Suomi-National Polar orbiting Partnership (S-NPP) satellite. The imagery can be visualized in Worldview and the Global Imagery Browse Services (GIBS).The sensor resolution is 750 m and 375 m (M Bands are 750 m, I Bands are 375 m), imagery resolution is 250 m, and the temporal resolution is daily.

Vegetation and bare ground

Vegetation is very reflective in the near infrared (Band I2), and absorbent in Band I1 and Band M11. Assigning that band to green means even the smallest hint of vegetation will appear bright green in the image. Naturally bare soil, like a desert, is reflective in all bands used in this image, but more so in the SWIR (Band M11, red) and so soils will often have a pinkish tinge.

Burned areas

Burned areas or fire-affected areas are characterized by deposits of charcoal and ash, removal of vegetation and/or the alteration of vegetation structure. When bare soil becomes exposed, the brightness in Band I1 may increase, but that may be offset by the presence of black carbon residue; the near infrared (Band I2) will become darker, and Band M11 becomes more reflective. When assigned to red in the image, Band M11 will show burn scars as deep or bright red, depending on the type of vegetation burned, the amount of residue, or the completeness of the burn.

Water

Liquid water on the ground appears very dark since it absorbs in the red and the SWIR. Sediments in water appear dark blue. Ice and snow appear as bright turquoise. Clouds comprised of small water droplets scatter light equally in both the visible and the SWIR and will appear white. These clouds are usually lower to the ground and warmer. High and cold clouds are comprised of ice crystals and will appear turquoise.

References: Earthdata: VIIRS