Glossary of Terms and Acronyms - D - F

DATA SYNCHRONIZATION TIME

The start, end and duration of a vehicle's departure from the ground.

DEW POINT

The temperature to which a parcel of air must be cooled to produce condensation.

DEW POINT TEMPERATURE

The temperature to which a parcel of air must be cooled to produce condensation.

DEWPOINT

The temperature to which a sample of air must be cooled, with air pressure constant, in order to attain saturation.

DEWPOINT HYDROMETER

An instrument for determining the specific gravity of liquids at their dew-point.

DIAL

Differential Absorption Lidar - uses the backscatter of four simultaneous laser wavelengths through zenith and nadir quartz windows to measure the vertical profiles of O3 and aerosols/clouds.

DIODE LASER HYGROMETER

The Diode Laser Hygrometer (DLH), developed by NASA's Langley and Ames Research Centers, has flown on the NASA DC-8 during several field campaigns. The DLH is a near-infrared spectrometer operating near 1.4 microns, and was developed for in situ measurements of atmospheric water vapor (H 2O(v)) from aircraft platforms. It is based upon near-infrared tunable diode technology. This spectrometer provides true in situ monitoring of water vapor concentrations with precision levels exceeding those of existing Lyman alpha and frost point hygrometers.

DISCOVER

The primary objective of the Distributed Information Services for Climate and Ocean Products and Visualizations for Earth Research (DISCOVER) Project is to provide highly accurate, long-term ocean and climate products suitable for the most demanding Earth research applications via easy-to-use display and data access tools. These products are derived from a large network of satellite microwave sensors going back to 1979. Most of the products are produced in near real-time (3-12 hours) on a 24x7 basis and hence are also suitable for some weather applications. The products include sea-surface temperature and wind, air temperature, atmospheric water vapor, cloud water, and rain rate. A key element of DISCOVER is the merging of multiple sensors from multiple platforms into geophysical data sets consistent in both space and time. DISCOVER is a follow-on activity to the Passive Microwave ESIP and SSM/I-SSMIS Pathfinder projects and builds on user interface technology available through these programs. In addition, DISCOVER contains a Technology Development component that provides an extended set of user services and visualization tools to greatly enhance the utility of the products and increase online analysis of these data.

DMSP

Defense Meteorological Satellite Program. A series of meterological spacecraft controlled by the U.S. Air Force Space and Missiles System. The DMSP program designed, built, launched, and maintained several near polar orbiting, sun synchronous satellites monitoring the meteorological, oceanographic, and solar-terrestrial physics environments. Now declassified, data from DMSP is maintained at NCDC.

DMSP-5B-F3

A spacecraft controlled by the Defense Meteorological Satellite Program which originated as a long-term U.S. Air Force effort but is now declassified. DMSP-5B F3 was the third satellite launched of the Block 5B series. It was launched Nov. 9, 1972. It was in a noon-midnight sun-synchronous orbit with the altitude between 797 and 855 km, inclination of 98.8 degrees, and period of101.5 minutes.

DMSP-F1

DMSP F1 was the first satellite launched of the Block 5D series. It was launched Sept. 11, 1977 and mission ended Sept. 9, 1979. It was a noon-midnight sun-synchronous orbit with the altitude between 798 and 853 km, inclination of 99.0 degrees, and period of 101.4 minutes.

DMSP-F10

DMSP-F10 was the tenth block 5D satellite launched on December 1, 1990. The mission ended November 14,1997 when the bearings on the momentum flywheels seized and caused the spacecraft to tumble. F10 had a mid-morning /late evening (~10AM/PM) crossing time.

DMSP-F11

DMSP-F11 was the 11th block 5D satellite launched on November 28, 1991. F-11 has an approximate equator crossing time of 6:30 AM/PM.

DMSP-F12

DMSP -F12 was twelvth in the block 5D line. Launched on August 19, 1994 this sun synchronous satellite has an equator crossing time of 9:30 AM/PM. Launched: Aug. 19, 1994.

DMSP-F13

DMSP-F13 is the number 13 block 5D satellite with an approximate equator crossing time of 5:45 AM/PM. Launched Mar 24, 1995.

DMSP-F14

DMSP-F14 is the 14 of the block 5D satellites. It has an approximate equator crossing time of 8:28 AM/PM. Launched: Apr. 4, 1997.

DMSP-F15

A spacecraft controlled by the Defense Meteorological Satellite Program which orginated as a long-term U.S. Air Force effort but are now declassified. Satellite number F-15 has an approximate equator crossing time of 9:20 AM/PM. Launched: 27 Apr, 2000.

DMSP-F3

DMSP-F3 was the third satellite launched of the Block 5D series of DMSP satellites launched Nov. 9 1972. It was in a noon-midnight sun-synchronous orbit with the altitude between 797 and 855 km, inclination of 98.8 degrees, and period of 101.5 minutes.

DMSP-F7

A spacecraft controlled by the Defense Meteorological Satellite Program which originated as a long-term U.S. Air Force effort but are now declassified. DMSP F7 was the seventh launched of the Block 5D series. It was launched Nov. 18, 1983 and mission ended Oct. 17, 1987. It was a noon-midnight sun-synchronous orbit with the altitude between 815 and 832 km, inclination of 98.7 degrees, and period of 101.5 minutes.

DMSP-F8

A spacecraft controlled by the Defense Meteorological Satellite Program which originated as a long-term U.S. Air Force effort but are now declassified. Satellite number F8 has an approximate equator crossing time of 6:00 AM/PM. Launched: June 19, 1987.

DMSP-F9

A spacecraft controlled by the Defense Meteorological Satellite Program which originated as a long-term U.S. Air Force effort but is now declassified. DMSP F9 was the ninth launched of the Block 5D series. It was launched Feb. 3, 1988 and the mission ended March 1992. It was a noon-midnight sun-synchronous orbit with the altitude between 815 and 826 km, inclination of 98.7 degrees, and period of 101.4 minutes.

DOPPLER RADAR

A Doppler radar has the capability of measuring some information about winds (on top of the usual echo strength all radars measure) by using the Doppler effect.

DOPPLER VELOCITY

Radial velocity (velocity toward or away from the radar site) of radar illuminated objects.

DOPS

Two time resolved optical pulse sensors viewing at two different frequencies with a very wide FOV (50deg), an all sky detector, a video camera with VCR tape storage, and associated data acquisition systems for the optical pulse sensors.

DROPLET CONCENTRATION/SIZE

The physical size of water droplets and the number of water droplets recorded in a given area or volume within a cloud.

DROPLET SIZE

The physical size of water droplets and the number of water droplets recorded in a given area or volume.

DROPSONDE

An instrument package which contains a temperature sensor (thermistor), a moisture sensor (hygrometer) and a GPS receiver which determines the position of the package in time and 3 dimensional space. Upon release, the dropwindsonde transmits data to the releasing aircraft (DC-8, WC-130, WP-3) where the data is collected and saved. When subsequently analysed, the resultant sounding yields temperature, dewpoint and windspeed observed by the instrument.

DROPWINDSONDE

An instrument package which contains a temperature sensor (thermistor), a moisture sensor (hygrometer) and a GPS receiver which determines the position of the package in time and 3 dimensional space. Upon release, the dropwindsonde transmits data to the releasing aircraft (DC-8, WC-130, WP-3) where the data is collected and saved. When subsequently analysed, the resultant sounding yields temperature, dewpoint and windspeed observed by the instrument.

DROPWINDSONDE

An instrument package which contains a temperature sensor (thermistor), a moisture sensor (hygrometer) and a GPS receiver which determines the position of the package in time and 3 dimensional space. Upon release, the dropwindsonde transmits data to the releasing aircraft (DC-8, WC-130, WP-3) where the data is collected and saved. When subsequently analysed, the resultant sounding yields temperature, dewpoint and windspeed observed by the instrument.

DUAL OPTICAL PULSE SENSOR

Two time resolved optical pulse sensors viewing at two different frequencies with a very wide FOV (50deg), an all sky detector, a video camera with VCR tape storage, and associated data acquisition systems for the optical pulse sensors.

ECMWF

The European Centre for Medium-range Weather Forecasts (ECMWF) is an international agency supported by various European countries. The ECMWF began producing operational medium-range weather forecasts in 1979. The Centre objectives include the development of medium-range forecast models, the generation and distribution of that forecast information and research relating to improving forecasting techniques.

ECMWF FORECAST MODEL

European Center for Medium-range Weather Forecast Model: an operational analysis-forecasting system. One use of this model is for estimating global precipitation.

EDOP

The ER-2 Doppler radar (EDOP) is an X-band (9.6 GHz) Doppler radar mounted in the nose of ER-2. The instrument has two fixed antennas, one pointing at nadir and the second pointing approximately 33 degree ahead of nadir.

ELECTRIC FIELD

An abstract concept analogous to magnetic field. Useful in determining a force that a test charge (a point source of known electric charge) would experience in the vicinity of another point charge. A single positive (negative) point charge produces an electric field directed outward (inward). Measured in volts/meter.

ELECTRIC FIELD MILL

Electric field mills are used to measure the vertical component of the electric field as the aircraft flies in the vicinity of electrified clouds. The dynamic range of these instruments extends from the fair weather fields (a few tens of V/m) to large thunderstorm fields (thousands of V/m). Using these field mills, it is possible to detect both intracloud and cloud-to-ground lightning from the abrupt electric field changes in the data.

EMISSIVITY

The ratio of the radiation emitted by a surface to the radiation emitted by a perfect blackbody radiator at the same temperature.

EOS REGIONAL AMAZON MODEL

This project addresses the question of how extensive land use change or more subtle regional climate variations modify the natural functioning and structure of the Amazonian ecosystems, from routing of water and its chemical load through precipitation and drainage systems back to the atmosphere and the oceans. The primary area of interest is 20S-6N, 45W-80W.

FAO SOIL MAPS

Soil maps from the Food and Agriculture Organization at 1:5M scale. Includes major and associated soil units for each land cell; surface texture, surface slope, phase, and miscellaneous land units where available.

FAST ANTENNA

"Slow" and "Fast" antennas- This system acquires lightning waveforms and provided a measure of total lightning. The system consists of a flat plate antenna and a broadband charge amplifier with a selectable time constant (i.e., "slow antenna" or "fast antenna"), a filter for removing undesired signals (e.g., radio frequency interference), a transient waveform recorder, and a data acquisition system.

FIELD MILL

An instrument which detects and measures the electrostatic field strength within the instrument field of view using stainless steel plates (stators) which are alternatively shielded and exposed to the existing atmospheric electric field by a grounded rotor. By comparing the differences between the two measurements, a determination of the observed field strength is made.

FILM HYGROMETER

An instrument designed to measure absolute humidity of the atmosphere.

FIRE III ACE

FIRE, the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment, studied a variety of Arctic cloud systems under spring and summer conditions. A team of national and international scientists conducted the FIRE Arctic Cloud Experiment (ACE) in a two-phase field campaign-- the first phase of which began in April, 1998, with a second phase conducted during July, 1998. The scientific objectives of FIRE ACE were to study impact of Arctic clouds on radiation exchange between surface, atmosphere, and space, and the influence of surface characteristics of sea ice, leads, and ice melt ponds on these clouds. FIRE ACE attempted to document, understand, and predict the Arctic cloud-radiation feedbacks, including changes in cloud fraction and vertical distribution, water vapor cloud content, cloud particle concentration and size, and cloud phase as atmospheric temperature and chemical composition change. FIRE ACE data is used to focus on improving current climate model simulations of the Arctic climate, especially with respect to clouds and their effects on the surface energy budget. In addition, FIRE ACE investigated a number of scientific questions dealing with radiation, cloud microphysics, and atmospheric chemistry.

FLIGHT DATA LOGS

A record of instrument, flight and vehicle status.

FLIGHT LEVEL WINDS

Wind speed and direction observed by an aircraft at a specific location and time.

FLUXGATE MAGNETOMETER

Instrument that measures the Earth's magnetic field intensity and changes there-to.

FSSP

The ForwardScattering Spectrometer Probe, Model 300 (FSSP-300) Aerosol Spectrometer sizes particles by measuring the light intensity scattered forward from the angles of 4 degrees to 12 degrees by aerosol, and cloud particles that pass through a focussed laser beam.

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