True Color
Description:
True color images are derived by combining three solar wavelengths, all in the wavelength range of human vision. This makes for very realistic images, with colors that imitate how the human eye might see the scene.
Currently (as of 2013), only polar-orbiting satellites have the needed channels to produce true color images. The instruments include the MODIS imagers on board the EOS-Terra and Aqua satellites, the VIIRS imager on board the Suomi NPP satellite launched in October 2011, and the MERSI imagers on the Chinese FY-3 satellites. These satellites give us a preview for similar products from the upcoming U.S. JPSS polar-orbiting satellites and other planned international missions including the Japanese Himawari and EUMETSAT Meteosat Third Generation (MTG) geostationary satellites.
Coverage: Daytime only, requires solar reflectance information
Channels: Three solar wavelengths available on MODIS, Suomi NPP VIIRS, Chinese FY-3 MERSI; future JPSS VIIRS, Advanced Himawari Imager (AHI), and MTG (Meteosat Third Generation) FCI (Flexible Combined Imager)
- Red (0.640 µm on MODIS, 0.672 µm on Suomi NPP & future JPSS VIIRS)
- Green (0.555 µm on MODIS and VIIRS)
- Blue (0.488 µm on MODIS and VIIRS)
Color scheme:
- Vegetated areas are green
- Deserts are brown
- Clouds are white
- Water is blue
Advantages:
- Produces a result similar to color photography
- Easy to interpret
- Particularly useful for viewing land surfaces for geological and land-use analysis
- Provides compelling views of smoke and dust storms
Limitations:
- Daytime only
- No microphysical information for clouds
- At present (2013), only produced by two MODIS imagers and one VIIRS imager (on board Suomi NPP polar orbiter)
Live data links:
- NRL NexSat site, http://www.nrlmry.navy.mil/NEXSAT.html
- NRL VIIRS Project site, http://www.nrlmry.navy.mil/VIIRS.html
- SSSEC/CIMSS University of Wisconsin MODIS Today site, http://ge.ssec.wisc.edu/modis-today/index.php
- CIRA/RAMMB Colorado State University Suomi NPP VIIRS Online site, http://rammb.cira.colostate.edu/ramsdis/online/npp_viirs.asp
- CIRA/RAMMB Colorado State University Suomi NPP VIIRS Imagery and Visualization Team Blog site, http://rammb.cira.colostate.edu/projects/npp/blog/
- NASA Rapid Response, EOSDIS Earth Data Website, http://earthdata.nasa.gov/data/near-real-time-data/rapid-response
- NASA GSFC Direct Readout Laboratory (under Recent Data Products menu item): http://directreadout.sci.gsfc.nasa.gov/
- USDA Forest Service Fire Imagery (under Satellite Imagery menu item): http://activefiremaps.fs.fed.us/
References:
- Miller, S. D., J. D. Hawkins, J. Kent, F. J. Turk, T. F. Lee, A. P. Kuciauskas, K. Richardson, R. Wade, and C. Hoffman, 2006: NexSat: Previewing NPOESS/VIIRS imagery capabilities. Bull. Amer. Meteor. Soc, 87, 433-446.
- Hillger, D. H., T. Kopp, T. Lee, D. Lindsey, C. Seaman, S. Miller, J. Solbrig, S. Kidder, S. Bachmeier, T. Jasmin, and T. Rink, in press: First-light imagery from Suomi NPP VIIRS. Bull. Amer. Meteor. Soc.
Examples:
This MODIS true color product shows southern California in October 2007. Coastal regions, which are often green, are as brown as the deserts. The smoke from fires (bluish white) and the dust (brownish white) have been blown offshore by fierce offshore winds.
This true color image was produced during a relatively cool, wet summer over the Great Plains of the United States, with the green areas over Oklahoma, Kansas, and Nebraska representing dense crops. The 100th meridian traditionally marks a boundary, with greener, wetter conditions to the east, and browner, drier conditions to the west.