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ice age |
A glacial epoch or time of extensive glacial activity |
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ice core |
A cylindrical section of ice removed from a glacier or an ice sheet in order to study climate patterns of the past. By performing chemical analyses on the air trapped in the ice, scientists can estimate the percentage of carbon dioxide and other trace gases in the atmosphere at that time. |
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ice sheet (continental glacier) |
A glacier of considerable thickness and more than 50,000 sq km in area. It forms a continuous cover of ice and snow over a land surface. An ice sheet is not confined by the underlying topography but spreads outward in all directions. During the Pleistocene Epoch, ice sheets covered large parts of North America and northern Europe but they are now confined to polar regions (e.g., Greenland and Antarctica). |
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ice shelf |
A thick mass of ice extending from a polar shore. The seaward edge is afloat and sometimes extends hundreds of miles into the sea. |
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imager |
A satellite instrument that measures and maps the Earth and its atmosphere. Imager data are converted by computer into pictures. |
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in situ |
Latin for 'in original place.' Refers to measurements made at the actual location of the object or material measured. Compare remote sensing. |
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inclination |
One of the six Keplerian elements, it indicates the angle of the orbit plane to the central body's equator. See Keplerian elements for diagram.
The elliptical path of a satellite orbit lies in a plane known as the orbital plane. The orbital plane always goes through the center of the Earth but may be tilted at any angle relative to the equator. Inclination is the angle between the equatorial plane and the orbital plane measured counter-clockwise at the ascending node.
A satellite in an orbit that exactly matches the equator has an inclination of 0 degree, whereas one whose orbit crosses the Earth's poles has an inclination of 90 degrees. Because the angle is measured in a counterclockwise direction, it is quite possible for a satellite to have an inclination of more than 90 degrees. An inclination of 180 degrees would mean the satellite is orbiting the equator, but in the opposite direction of the Earth's rotation. Some sun-synchronous satellites that maintain the same ground track throughout the year have inclinations of as much as 98 degrees. U.S. scientific satellites that study the sun are placed in orbits closer to the equator, frequently at 28 degrees inclination. Most weather satellites are placed in high-inclination orbits so they can oversee weather conditions worldwide. See orbital inclination. |
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information system |
All of the means and mechanisms for data receipt, processing, storage, retrieval, and analysis. Information Systems can be designed for storage and dissemination of a variety of data products--including primary data sets and both intermediate and final analyses--and for an interface providing connections to external computers, external data banks, and system users. To be effective, the design and operation of an information system must be carried out in close association with the primary producers of the data sets, as well as other groups producing integrated analyses or intermediate products. |
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infrared radiation (IR) |
Infrared is electromagnetic radiation whose wavelength spans the region from about 0.7 to 1000 micrometers (longer than visible radiation, shorter than microwave radiation). Remote sensing instruments work by sensing radiation that is naturally emitted or reflected by the Earth's surface or from the atmosphere, or by sensing signals transmitted from a satellite and reflected back to it. In the visible and near-infrared regions, surface chemical composition, vegetation cover, and biological properties of surface matter can be measured. In the mid-infrared region, geological formations can be detected due to the absorption properties related to the structure of silicates. In the far infrared, emissions from the Earth's atmosphere and surface offer information about atmospheric and surface temperatures and water vapor and other trace constituents in the atmosphere. Since IR data are based on temperatures rather than visible radiation, the data may be obtained day or night. |
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insolation |
Solar radiation incident upon a unit horizontal surface on or above the Earth's surface. |
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International Geosphere-Biosphere Programme (IGBP) |
The International Geosphere-Biosphere Programme (IGBP) is an interdisciplinary scientific activity established and sponsored by the International Council for Science (ICSU). The program was instituted by ICSU in 1986, and the IGBP Secretariat was established at the Royal Swedish Academy of Sciences in 1987 and is focused on acquiring basic scientific knowledge about the interactive processes of biology and chemistry of the earth as they relate to Global Change.
See IGBP web site |
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International System of Units (SI) |
The International System of Units prescribes the symbols and prefixes shown in the table to form decimal multiples and submultiples of SI units.
The following examples illustrate the use of these prefixes:
0.000,001 meters = 1 micrometer = 1жm
1000 meters = 1 kilometer = 1 km
1,000,000 cycles per second = 1,000,000 hertz = 1 megahertz =1 MHz |
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Intertropical Convergence Zone (ITCZ) |
A discontinuous belt of thunderstorms paralleling the equator and marking the convergence of the northern and southern hemisphere surface trade winds. See El Niño's Extended Family |
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ion |
Atom or molecule that has acquired an electric charge by the loss or gain of one or more electrons. |
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isobars |
Lines drawn on a weather map joining places of equal barometric pressure. |
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isothermal |
Of or indicating equality of temperature. |
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isotherms |
Lines connecting points of equal temperature on a weather map. |
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isthmus |
Narrow strip of land located between two bodies of water, connecting two larger land areas. |
