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GLOSSARY

Our comprehensive earth science glossary is available to assist in your understanding of the MY NASA DATA microsets, lesson plans and computer tools. Please select the first letter of the word you wish to check for a definition and further information.

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All definitions
N
nadir:
the point on Earth directly below a satellite orbiting the Earth, that is, the down direction. Opposite of zenith.  
N
nanometer:
One billionth of a meter (10.e-9 or 0.000000001 m). There are a billion (1,000,000,000) nanometers in one meter.   The Metric System
N
NASA:
acronym for National Aeronautics and Space Administration.   The NASA Web site
N
NCDC:
acronym for the National Climatic Data Center.   The NCDC Web site
N
NDVI:
Normalized Difference Vegetation Index is a measurement of vegetation from satellite. NDVI is calculated by using the amount of visible light and near-infrared light reflected from Earth's surface. Healthy and dense vegetation will absorb most visible light and reflect near-infrared light, whereas unhealthy or sparse vegetation will reflect more visible light and less near-infrared. Low values of NDVI (0 - 0.1) indicate barren or snow-covered land. Middle values (0.2 - 0.5) indicate shrubs and grasslands, and high values (0.6 - 0.9) indicate temperate and dense tropical forests.   Measuring Vegetation Health
Image courtesy MISR Science Team
N
net radiation:
the amount of radiation that actually is added to a surface, taking into account all wavelengths and incoming as well as outgoing radiation.   Visualization of net radiation from the Earth Observatory Image of net radiation for March 2000
Image courtesy CERES Science Team
N
nitrogen oxide:
refers to a family of oxygen compounds of nitrogen (NOx) that are produced by combustion and result in harmful chemical reactions that produce smog, tropospheric ozone and acid rain.   More about NOx
N
NOAA:
acronym for National Oceanic and Atmospheric Administration. Two NOAA satellites (in addition to the ERBS satellite) that carried ERBE instruments were NOAA-9 and NOAA-10. NOAA satellites also provide the satellite imagery for weather forecasting.   The NOAA Web site
N
non-scanning instrument:
An instrument that is fixed with respect to the spacecraft on which it flies. This gives a broad field of view fixed around a point directly below the satellite. ERBE's non-scanning instruments contained 5 detectors which measured radiation reflected and emitted by the Earth-atmosphere system.   The ERBE non-scanning instrument The ERBE Non-Scanner
Image courtesy NASA
N
number density:
A unit often used in chemistry and physics. The number of something (particles, atoms, molecules, ...) in a given volume. The volume could be a cubic centimeter, cubic meter, or some other volume. This can be used in atmospheric science to describe the concentration of aerosols or trace gases. Because the number of atoms or molecules is usually large, scientific notation is used. For example: 3.e12 ozone molecules in a cubic centimeter inside the ozone layer (3,000,000,000,000 ozone molecules in a cubic centimeter).     Related MY NASA DATA Activity:  Parts Per Billion Activity (PowerPoint)

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