Glossary: N

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  1. Point on Earth directly beneath a satellite, the opposite of zenith. Compare with subsatellite point. Source: NASA (
  2. National Disaster Management Organisation, Ghana
  3. One billionth of a meter. Nanometers are used to measure wavelengths in the electromagnetic spectrum. Source: NASA (
  4. A nautical mile is a unit of distance equal to 1,852 meters. The length of the nautical mile is very close to the mean value of the length of 1 minute of latitude, which varies from approximately 1,843 meters at the equator to 1,861.6 meters at the...
  5. Electromagnetic radiation with wavelengths from just longer than the visible (about 0.7 micrometers) to about two micrometers. See electromagnetic spectrum. Source: NASA (
  6. A gas consisting of one atom of nitrogen and two atoms of oxygen. Source: NASA (
  7. Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced in the emissions of vehicle exhausts and from power stations. In the atmosphere, nitrogen oxides can contribute to formation of...
  8. A powerful greenhouse gas with a global warming potential of 320. Major sources of nitrous oxide include soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and...
  9. National Oceanic and Atmospheric Administration
  10. US National Oceanic and Atmospheric Administration
  11. An index, or scale, of vegetation conditions based on differences in the amount of visible and near-infrared light reflected from plants on Earth's surface. A vegetation index is a gauge of plant health, productivity, and density. Plant leaves...