| absorption | The process by which radiant energy
is absorbed and converted into other forms of energy. |
| absorption band | A range of wavelengths in the
electromagnetic spectrum within which radiation is absorbed by a substance. |
| albedo | Ratio of the amount of electromagnetic energy
reflected by a surface to the amount of energy incident upon it. |
| atmospheric windows | Portions of the spectrum that
transmit radiant energy effectively. |
| attenuation | Combined processes of scattering and
absorption which result in the loss of radiant energy. |
| bandpass | Interval of wavelengths. |
| BD enhancement curve | An infrared enhancement curve used in
hurricane analysis that highlights cloud top temperatures surrounding the eye of a hurricane. |
| Beer's Law | The linear relationship between absorbance
and concentration of an absorber of electromagnetic radiation. |
| bidirectional reflectance | The change in brightness of a
surface as the sensor viewing angle changes. |
| Bidirectional Reflectance Distribution Function (BRDF) | A
mathematical description of how reflectance varies for all combinations of illumination and
viewing angles at a given wavelength. |
| blackbody | A theoretical object that absorbs all the radiation that falls on it and radiates energy at the maximum possible rate per unit area at each wavelength for any given temperature. |
| channels | Specific bands of wavelengths sensed by a
satellite sensor. |
| contrast stretch | The process by which original input
brightness values are expanded to make use of the total range or sensitivity of the output
imaging device. |
| diffuse reflection | Occurs when the surface is
characterized by objects that are large relative to the wavelength of the incident
radiation. |
| electromagnetic radiation | An electromagnetic wave,
which travels through space at the speed of light, that is generated whenever an electrical
charge is accelerated. |
| electromagnetic (EM) spectrum | A continuum of all
types of electromagnetic radiation in which each type of radiation is ordered according to
its wavelength. |
| emission | The electromagnetic radiation exiting an object
due to the random motion and collision of molecular matter within the object. |
| emissivity | The ratio of the actual emitted radiance to
that of an ideal blackbody at the same temperature. |
| extinction | The loss or attenuation of radiant energy as
it passes through a medium and includes the combined processes of scattering and absorption. |
| hemispherical reflectance | A ratio of reflected radiant
flux from a surface to the incident radiant flux, or albedo of an object. |
| infrared (IR) | Region of the electromagnetic spectrum that
includes wavelengths from 0.7µ m to 14µ m. |
| Kirchoff's Law | States that in the infrared portion of the
electromagnetic spectrum, the spectral emmissivity of an object generally equals its spectral
absorptance. |
| Lambertian surface | One in which the radiant flux
leaving the surface is constant for any angle of reflectance to the surface. |
| MB enhancement curve | A type of infrared enhancement,
especially useful for thunderstorm analysis, that highlights cold cloud tops in order to
locate areas of intense convection. |
| microwave | Region of the electromagnetic spectrum in the
wavelength range of 1 mm to 1 m. |
| Mie scattering | Occurs when atmospheric particulates are
of roughly the same size as the wavelength of incident radiation. |
| Non-selective scattering | Occurs in the lowest portions
of the atmosphere where there are particles greater than 10 times the wavelength of the
incident electromagnetic radiation. |
| path length | The distance through the
atmosphere in which passing radiant energy is lost or attenuated. |
| Planck function | An expression that relates
emitted radiation at a particular wavelength to the temperature of an object. |
| radiant exitance | The amount of radiant flux
(radiant energy per unit time) leaving a surface per unit area. |
| Rayleigh scattering | Occurs when radiation interacts with
particles or molecules much smaller in diameter than the wavelength of the radiation. |
| reflection | The process by which a fraction of incident
radiation is immediately re-emitted, at the same wavelength, from a surface like a cloud top,
a water body, or the Earth's surface, and is not absorbed or transmitted. |
| remote sensing | Collection and interpretation of
information about an object without being in physical contact with the object. |
| scattering | Atmospheric scattering is accomplished
through absorption and re-emission of radiation by atoms or molecules. |
| specular reflection | Occurs when the surface from which
the radiation is reflected is essentially smooth: the average surface-profile height is
significantly smaller than the wavelength of incident radiation. |
| Stefan-Boltzmann Law | This law states that total
spectral radiant exitance (W) leaving a blackbody is proportional to the fourth power of its
temperature (T). |
| sunglint | A bright area seen on visible (vis) satellite
imagery where the satellite sensor records reflected solar radiation from water surfaces. |
| transmittance | The the fraction of electromagnetic
radiation that passes through a medium. |
| visible (vis) | Region of the electromagnetic spectrum
that includes wavelengths from 0.4µ m to 0.7µ m (400 to 700 nanometers). |
| wave frequency | The number of peaks passing a fixed point
in space per unit time. |
| wavelength | The distance from one wave peak to the
next. |
| weighting function | The change in transmissivity with
height. |
| Wiens Displacement Law | Describes the shift of the
radiant power peak to shorter wavelengths as temperature increases . |
| ZA enhancement curve | A general purpose infrared
enhancement curve that provides improved contrast between temperatures of meteorological
significance. |
