| 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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| LAI: |
| Leaf Area Index is a satellite measurement of vegetation density and greenness. It is generally aimed to analyze forested areas where trees create a canopy over the ground (agricultural areas can also be detected during the growing season). LAI is the ratio of the one-sided green broadleaf area (or needleleaf area) per unit ground area. LAI significantly varies seasonally for deciduous trees, but varies little for coniferous forests as expected. Values typically range from zero (no vegetation) to 5-7 (very dense forest).
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Image courtesy MISR Science Team |
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| land mask: |
| identifies the parts of Earth's surface that are land-covered for data analysis purposes. This allows other Earth science parameters, such as snow and cloud cover, to be averaged separately for land vs water areas. Typically, a resolution and land percentage are chosen based on the intended data use. For example, a 1 degree resolution gridbox area that contains greater than 90 percent land may be considered as land and analyzed as land even though water may be present in the form of rivers and lakes. Often, the number 1 is used for a land gridbox (white in the figure) and the number 0 is used for a water gridbox (blue in the figure). Coastal areas may be noted using the number 2 (black in the figure). These identify gridbox areas that are partially land, for example between 10 and 90 percent land. Note the areas of permanent sea ice around Antarctica that are denoted as land.
Related MY NASA DATA Activity: L
and Mask Detailed Explanation |
Image courtesy CERES Science Team |
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| La Nina: |
| the term used to identify opposite conditions from an El Nino when the Trade Winds strengthen and colder ocean surface water extends off the coast of Equador and Peru into the central Pacific Ocean.
NOAA El Nino Education Page
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| latent heat: |
| the energy required to change a substance to a higher state of matter (solid to liquid to gas). This same energy is released from the substance when the change of state is reversed (gas to liquid to solid).
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| latitude: |
| a measure which identifies the north - south location of a point on the Earth. It is the angle between the line connecting a point on the Earth and the Earth's center, and the equatorial plane of the Earth. There are three ways to express latitude. You may be most familiar with 0-90 North and 0-90 South. In the computer era this became -90 to +90, where -45 equivalent to 45 South. The third method is less familiar and is called the colatitude. Colatitude is 0 at the north pole, 90 at the equator, and 180 at the south pole. So, 45 South is equivalent to a colatitude of 135.
Related MY NASA DATA Activity: Latitude and longitude tool. |
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| limb scanning: |
| A technique used by some instruments in space which looks sideways through the atmosphere rather than down at the Earth. It can provide information about how certain components of the atmosphere change with altitude above the Earth's surface.
Orbit Visualization simulator tool
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Image courtesy The SOLAR project |
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| longitude: |
| a measure which identifies the east - west location of a point on the Earth. It is the angular distance along a line of latitude from the Greenwich Meridian - a reference longitude set to be zero degrees. There are three equivalent ways to express longitude, and scientists tend to use them interchangeably. You may be most familiar with longitude as 0-180 East, and 0-180 West. It can also be expressed as 0-360 East, or just 0-360. In that case, 270 East is equivalent to 90 West. The third system arose in the computer era, when carrying both a number (0-180) and a character (East or West) was inconvenient. The new convention of -180 to +180 was then developed. In this case,-90 is equivalent to 90 West.
Related MY NASA DATA Activity: Latitude and longitude tool. |
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| longwave radiation: |
| Electromagnetic radiation with a wavelength longer than about 5 microns. Bodies with temperatures in the range of the Earth System have a peak energy emission in this wavelength range.
Radiation Explanation
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| low cloud: |
| We define clouds using three broad altitude ranges, and the various cloud types are assigned to one of these ranges. For satellite observations, some measure of the cloud's altitude (often cloud top or effective cloud height) is used to place the cloud into an altitude range. The satellite does not have the qualitative information to pick a cloud type.
Information on cloud types and levels from the S'COOL Project.
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Image courtesy The S'COOL Project |
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