The VIIRS Corrected Reflectance imagery is only produced in near real-time. It provides continuity from the MODIS Corrected Reflectance imagery that was developed to provide natural-looking images by removing gross atmospheric effects such as Rayleigh scattering from the visible bands. By contrast, the Surface Reflectance product is available in near real-time and as a standard product. Surface Reflectance provides a more complete atmospheric correction algorithm that includes aerosol correction and is designed to derive land surface properties. In clear atmospheric conditions the corrected reflectance product is similar to the SR product, but they depart from each other in the presence of aerosols.
Band Combinations
VIIRS (Suomi NPP/NOAA-20) Corrected Reflectance True Color
True Color: Red = Band I1 (600-680 nm), Green = Band M4 (545-565 nm), Blue = Band M3 (478-498 nm)
These images are called true-color or natural color because this combination of wavelengths is similar to what the human eye would see. The images are natural-looking images of land surface, oceanic, and atmospheric features.
The VIIRS Corrected Reflectance imagery is available only as NRT imagery. The imagery can be visualized in NASA's Worldview and Global Imagery Browse Services (GIBS). The sensor resolution is 750m and 375m (M Bands are 750m, I Bands are 375m), imagery resolution is 250m, temporal resolution is daily, and temporal availability for viewing in GIBS/Worldview is November 24, 2015, to present. View True Color (I1, M4, M3) in Worldview.
VIIRS (Suomi NPP/NOAA-20) Corrected Reflectance (Bands M3, I3, M11)
False Color: Red = M3 (478-498 nm), Green = I3 (1580-1640 nm), Blue = M11 (2225-2275 nm)
This combination is used to map snow and ice. Snow and ice are very reflective in the visible part of the spectrum (Band M3), and very absorbent in Bands I3 and M11 (short-wave infrared, or SWIR). This band combination is good for distinguishing liquid water from frozen water, for example, clouds over snow, ice cloud versus water cloud; or floods from dense vegetation. This layer is similar to the MODIS Corrected Reflectance Bands 3, 6, 7 layer.
The VIIRS Corrected Reflectance imagery is available only as NRT imagery. The imagery can be visualized in Worldview and GIBS. The sensor resolution is 750m and 375m (M Bands are 750m, I Bands are 375m), imagery resolution is 250m, temporal resolution is daily, and temporal availability for viewing in GIBS/Worldview is November 24, 2015, to present. View False Color (M3, I3, M11) in Worldview.
Snow and Ice
Since the only visible light used in these images (Band M3) is assigned to red, snow and ice appear bright red. The more ice, the stronger the absorption in the SWIR bands, and the more red the color. Thick ice and snow appear vivid red (or dark pink), while small ice crystals in high-level clouds will appear pinkish.
Vegetation
Vegetation will appear green in this band combination, as vegetation is absorbent in Bands M3 and M11, but reflective in Band I3. Bare soil and deserts will appear bright cyan in the image since it is much more reflective in Band I3 and M11 than Band M3.
Water
Liquid water on the ground will appear very dark since it absorbs in the red and the SWIR, but small liquid water drops in clouds scatter light equally in both the visible and the SWIR, and will therefore appear white. Sediments in water appear dark red.
VIIRS (Suomi NPP/NOAA-20) Corrected Reflectance (Bands M11, I2, I1)
False Color: Red = M11 (2225-2275 nm), Green = I2 (846-885 nm), Blue = I1 (600-680 nm)
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. This layer is similar to the MODIS Corrected Reflectance Bands 7, 2, 1 layer.
VIIRS Corrected Reflectance imagery is available only as NRT imagery. The imagery can be visualized in Worldview, Worldview Snapshots, and GIBS. The sensor resolution is 750m and 375m (M Bands are 750m, I Bands are 375m), imagery resolution is 250m, temporal resolution is daily, and temporal availability for viewing in GIBS/Worldview is November 24, 2015, to present. View False Color (M11, I2, I1) in Worldview.
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 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.