| 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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| accretion: |
| the growth of ice crystals or snowflakes by collision with supercooled cloud droplets that freeze upon contact.
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| aerosol: |
| small liquid or solid particles dispersed in the atmosphere. Large quantities are often regarded as pollutants in the form of haze and smoke.
NASA Fact Sheet on Aerosols
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| aggregation: |
| the process by which snowflakes clump together or collide as they fall, especially snowflakes in the shape of dendrites.
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| air mass: |
| a body of air that has relatively uniform temperature and humidity based on the surface characteristics of its source region.
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Image courtesy University of Illinois WW2010 Project |
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| air quality: |
| a measure of the degree to which air is free from harmful pollution. In the US, the Environmental Protection Agency identifies and regulates the harmful compounds in air, particularly those that harm human health, damage crops, or cause harm to building, roads, and other structures (for example, acid rain). Scientists study the sources of air pollutants, how pollution changes as air moves around the planet, and how the chemistry in the atmosphere removes air pollutants..
Clean Air Primer
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| albedo: |
| a measure of reflectivity; the planetary albedo of the Earth averages about 0.31, meaning that on average about 31 percent of the light from the Sun is reflected back to
space. The value at any given time is dependent on cloud cover and ground cover (snow, ice).
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| algorithm: |
| A precise rule (or set of rules) specifying how to solve some problem, or do a calculation.
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| altitude: |
| the vertical distance or height measured from sea level.
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| anomaly: |
| the difference from the average, or climatological, value. Anomalies are often used in climate science, as they make small changes in variables much easier to see.
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| Aqua: |
| The second spacecraft of NASA\'s Earth Observing System (EOS). Aqua is collecting global data sets for research on the Earth System, with a particular emphasis on the water cycle.
The Aqua website
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| ASDC: |
| acronym for Atmospheric Science Data Center. ASDC is located at NASA Langley Research Center in Hampton, Virginia. ASDC processes, archives and distributes NASA satellite data relating to clouds, aerosols, radiation budget and tropospheric chemistry.
The ASDC website
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| atmosphere: |
| the mixture of gases that surrounds the Earth and some other planets. The concentrations of the gaseous constituents of Earth's atmosphere are determined by biogeochemical processes, including manmade effects.
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| atmospheric column: |
| a vertical pillar defined by a unit area on Earth's surface and bounded by the top of the atmosphere that is used to quantify an atmospheric parameter such as pressure, ozone or precipitable water. See image illustrating atmospheric pressure.
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| atmospheric pressure: |
| the weight of the column of the atmosphere above a surface. On average, the atmospheric pressure at sea level is 1013.25 millibars (mb), but it can be relatively higher or lower than this value based on air temperature and humidity. Changes in atmospheric pressure at a given location often indicate changing weather.
More about atmospheric pressure
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Image courtesy University of Illinois WW2010 Project |
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