GES DISC DAAC (GSFC DAAC)

 

  THUMB INDEX: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

ABSORPTIVITY

The capacity of a material to absorb incident radiant energy, measured as the ratio of the amount of radiant energy absorbed to the total amount incident on the material.

AEROSOLS

Dispersions in gas of particles of solid or liquid matter that are larger than single molecules yet small enough to remain dispersed for a significant length of time.

ALBEDO

The percentage of solar radiation reflected by an object.

BLACKBODY

An ideal emitter which radiates energy at the maximum possible rate per unit area at each wavelength for any given temperature. According to Kirchoff's Law, a blackbody also absorbs all the radiant energy incident on it; i.e., no energy is reflected or transmitted.

BRIGHT BAND

The enhanced radar echo of snow in the atmosphere as it melts to rain.

BRIGHTNESS TEMPERATURE

The temperature of a blackbody radiating the same amount of energy per unit area at the wavelengths under consideration as the observed body.

CHLORINE COMPOUNDS

Chemically decomposable substances containing chlorine, a very reactive element which combines directly with most other elements.

CLOUD ICE

The solid form of water substances in the cloud.

CLOUD LIQUID WATER

Liquid water particles formed and remaining suspended in clouds.

CLOUDS

Assemblies of tiny water and/or ice particles in the atmosphere above the earth's surface.

CSI

Coincidence Subsetted Intermediate products. The Satellite CSI products are those scans of data which correspond to the time when the sub-satellite point comes within a specified distance of indicated Ground Validation radar site or Experiment site. The GV CSI products consist of the single volume scan when the satellite is nearest or a gridded field associated with a VOS which is coincident with a satellite overpass.

DATA PRODUCT LEVEL

Raw Data

Data in their original packets, unprocessed, as received from the instrument on the satellite.

Level 0

Raw instrument data at original resolution, time ordered, with duplicate packets removed.

Level 1A

Reconstructed, unprocessed instrument data at full resolution, time referenced, and annotated with ancillary information, including radiometric and geometric calibration coefficients and georeferencing parameters (i.e., platform ephemeris), computed and appended, but not applied, to Level 0 data.

Level 1B

Radiometrically corrected and geolocated Level 1A data that have been processed to sensor units.

Level 2

Derived geophysical parameters at the same resolution and location as those of the Level 1 data.

Level 3

Geophysical parameters that have been spatially and/or temporally resampled from Level 1 or Level 2 data.

Level 4

Outputs or results from models using lower level data as inputs and, thus, not directly derived from the instruments.

DIFFERENTIAL REFLECTIVITY

Ratio of reflectivity at horizontal polarization to reflectivity at vertical polarization.

DROUGHT

A temporary negative deviation in environmental moisture status, long enough to cause moisture deficits in the soil and disrupt normal biological activities.

ENERGY DEPOSITION

The amount of energy absorbed by the earth at the top of the atmosphere. This transfer of energy is primarily due to the bombardment of earth by solar and interstellar winds.

EVAPORATION

The process whereby water at the earth's surface, either in liquid or solid form, is converted to vapor and transferred into the atmosphere.

EXTINCTION COEFFICIENT

A measure of the space rate of diminution, or attenuation, of any transmitted light, due to absorption and scattering.

FIELD OF VIEW

The solid angle through which an instrument is sensitive to radiation.

FREQUENCY

Number of oscillations per unit time or number of wavelengths that pass a point per unit time.

GEOPOTENTIAL HEIGHT

The height of a given point in the atmosphere in units proportional to the potential energy of unit mass (geopotential) at this height, relative to sea level.

GOES

Geostationary Operational Environmental Satellite.

GPROF

Goddard Profiling Algorithm.

GREENHOUSE GASES

Gases in the atmosphere which play an important role in the thermodynamics of the atmosphere by trapping long-wave terrestrial re-radiation and, thus, producing the greenhouse effect. These gases include carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons and, the major one, water vapor.

HEAT FLUX

The rate of flow of heat.

HUMIDITY

The water vapor content of air. Term is commonly used to mean "relative humidity," the dimensionless ratio of vapor that a given quantity of air can contain at a given temperature, expressed as a percentage. Perfectly dry air has a relative humidity of 0%; totally saturated air, 100%.

HYDROMETEOR

Any product of condensation or sublimation of water vapor, whether formed in the free atmosphere or at the earth's surface; also, any water particles blown by the wind from the earth's surface.

INTERTROPICAL CONVERGENCE ZONE

A low pressure trough and minimum east wind, lying between the trade regions of the two hemispheres, that are nearly continuous around the world on climatological charts.

INVERSION

An anomaly in the normal positive lapse rate of any atmospheric property, although, unqualified, usually implying a temperature inversion.

JET STREAM

A strong, narrow current, concentrated along a quasi-horizontal axis in the upper troposphere or in the stratosphere, characterized by strong vertical and lateral wind shears and featuring one or more velocity maxima.

KIRCHHOFF'S LAW

The radiation law which states that, at a given temperature, the ratio of the emissivity to the absorptivity for a given wavelength is the same for all bodies; this ratio is equal to the emissivity of an ideal blackbody at that temperature and wavelength. This law asserts that good absorbers of a given wavelength are also good emitters of the wavelength.

LAMBERTIAN SURFACE

An ideal, perfectly diffusing surface, which reflects energy equally in all directions.

LATENT HEAT

The heat released or absorbed per unit mass, at the same pressure and temperature, by a system in a reversible change of phase (e.g., water to water vapor by evaporation).

LBA

Large Scale Biosphere-Atmosphere Experiment in Amazonia LBA is an international field program designed to further understanding of the climatological, ecological, biogeochemical and hydrological processes in Amazonia, and the impact of land use change on these processes. The TRMM/LBA campaign took place in Brazil in the region 16S to 6 N and 76W to 49W (moving south to north and east to west) from January 1 through February 28, 1999. Data from the TRMM-LBA Field Experiment can be accessed from http://daac.gsfc.nasa.gov/precipitation/, and a link to the Brazilian LBA homepage is available there.

MEAN VELOCITY

For TRMM Ground Validation Doppler radars, this term refers to the mean radial velocity estimated by measuring Doppler shifts in the returned signal.

METEOSAT

The European Space Agency developed the Meteorological Satellite (Meteosat) as its contribution to the Global Atmospheric Research Program's World Weather Watch observing network. The satellite began as a French project named Meteosat and the name was retained when the European Space Agency took over the project.

METEOSAT-5 was launched in November, 11, 1991.

METEOSAT-7 was launched in September, 9, 1997.

MOISTURE FLUX

The rate of flow of moisture.

MOMENTUM

A property of a particle which is given by the product of its mass with its velocity.

NITROGEN COMPOUNDS

Chemically decomposable substances containing nitrogen, a colorless, tasteless, odorless gaseous element, and the most abundant constituent of the atmosphere.

OCEAN COMPOSITION

The chemical constituency of the ocean, such as salinity and calcium concentration.

OPTICAL THICKNESS

Or optical depth. The mass of a given absorbing or emitting material lying in a vertical column of unit cross-sectional area and extending between two specified levels.

OZONE

A nearly colorless, triatomic, gaseous form of oxygen, formed from diatomic oxygen by the addition of an extra oxygen atom.

PATH ATTENUATION

The reduction of radiation with increasing distance from the radiation source.

POWER

The rate of flow of radiant energy, generally expressed in watts. Because of the large range of power measured by radar systems, it is commonly expressed in decibels (dB).

PR

Precipitation Radar, a 13.8 GHz radar, one of three rain instruments carried on board the TRMM satellite.

PRECIPITABLE ICE

Ice, as precipitation, potentially available from atmospheric water vapor.

PRECIPITABLE WATER

Water, as precipitation, potentially available from atmospheric water vapor.

PRECIPITATION

Any form of water, liquid or solid, falling to the ground from the atmosphere.

PRESSURE

Or, in meteorology, atmospheric pressure or barometric pressure. A type of stress that is ideally uniform in all directions.

QUANTUM THEORY

The theory first stated by Max Planck that all electromagnetic radiation is emitted and absorbed in quanta, each of magnitude hv, h being the Planck constant and v the frequency of the radiation.

QUATERNARY

The youngest of geologic periods, subdivided into the Pleistocene and Recent epochs, the latter including the present. The term refers to geologic time and deposits.

RADIANCE

A measure, in power units, of the total radiant flux from a surface, in a given direction.

RADIATIVE PROCESSES

Those processes governing the transfer of radiant energy, such as reflection and absorption.

RAIN TYPE

The two basic rain types are convective and stratiform.

REFLECTIVITY

Ratio of the radiant energy reflected by an object to that incident on it. Reflectivity is described as a function of radiation wavelength and is determined by the physical composition of the object.

SATELLITE COINCIDENCE

The period of time during which the sub-satellite point is within a specified distance of a given TRMM Ground Validation radar site.

SOIL

In pedology, a dynamic natural body on the surface of the earth which supports plant growth and is composed of mineral and organic materials and living forms.

SOLAR IRRADIANCE

The measure, in power per area units, of solar radiant flux incident on a surface.

SSM/I

Special Sensor Microwave/Imager, a seven-channel, four-frequency, linearly polarized, passive microwave radiometer, carried on board the Defense Meteorological Satellite Program (DMSP) satellite.

STABILITY

Or hydrostatic stability. Tendency of the atmosphere to inhibit, be indifferent to, or enhance vertical motion. If a parcel of air tends to continue moving vertically in the direction of displacement, the atmosphere is unstable; if it tends to return to its initial level, the atmosphere is stable.

SURFACE CROSS SECTION

In radar meteorology, the energy returned to the antenna, used to characterize the radar reflectivity of precipitation and cloud targets.

SURFACE EMISSIVITY

The ratio of the radiation given off by a surface to the radiation given off by a blackbody at the same temperature. A blackbody has an emissivity of 1; other objects have values between 0 and 1.

SURFACE PROPERTIES

Those properties of the thin layer of air adjacent to the earth's surface (e.g., surface wind), or of the top or top layer of the ground (e.g., soil moisture).

TEMPERATURE

A term used to express the relative intensity of heat. It is identified with the kinetic energy of translation of molecules and has a value of absolute zero where all motion has ceased.

TMI

TRMM Microwave Imager, a nine-channel, five-frequency (dual polarization for 10.65, 19.35, 37, and 85.5 GHz, and vertical polarization for 21 GHz) microwave radiometer, one of three rain instruments carried on board the TRMM satellite.

TRACE GASES

Gases present in minor amount in the atmosphere.

TURBULENCE

A state of fluid flow in which the instantaneous velocities exhibit irregular and apparently random fluctuations so that, in practice, only statistical properties can be recognized and analyzed.

UPWELLING

The rising of water towards the surface from subsurface layers of a body of water, occurring most prominently near coasts.

VEGETATION

Plants collectively; the community of plants in a region.

VIRS

Visible/InfraRed Scanner, a five-channel (0.63, 1.6, 3.75, 10.8, and 12 um) visible and infrared radiometer, one of three rain instruments carried on board the TRMM satellite.

VOLUME SCAN (VOS)

A scan in space that is irradiated by a TRMM Ground Validation radar, consisting of 360-degree azimuthal sweeps at several elevation angles.

WATER VAPOR

Water substance in vapor form. It is the major greenhouse gas. Its amount varies widely in space and time due to the great variety of sources of evaporation and sinks of condensation.

WINDS

A stream of air flowing relative to the earth's surface, usually more or less parallel to the ground, caused by a pressure gradient.

X-RAY

Electromagnetic radiation of very short wavelength, between those of gamma rays and ultraviolet radiation.

YAW

The rotation of an aircraft or spacecraft about its vertical axis.

ZENITH ANGLE

The angular distance of any celestial object from a given observer's zenith, measured along the great circle of the celestial sphere from zenith to object.