Glossary of Terms and Acronyms - J - L

JACKSONVILLE 90

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JPL LASER HYGROMETER

The Laser Hygrometer measures in situ water vapor content using a tuneable laser emitting at 1.37 microns. Absorption at that wavelength is a function of water vapor content. Measuring the amount of absorption in an open path beyond the aircraft boundary layer, a value of water vapor pressure is made. The maximum sampling rate is 8 Hz, but the instrument is normally configured through the software for a 1Hz sampling rate.

KSC FIELD MILL NETWORK

The KSC (Kennedy Space Center) Field Mill Network (also known as the Advanced Ground Based Field Mill (AGBFM) Network) is a system of instruments called field mills. Each field mill detects the overhead electrostatic field strength using stainless steel plates (stators) which are alternatively shielded and exposed to the existing atmospheric electric field by a grounded rotor. The data are recorded at a rate of 50 Hz at a 4V/m sensitivity. Fields of up to +-32kV/m can be recorded with the higher readings corresponding to an intense thunderstorm overhead. The sign convention corresponds to atmospheric potential gradient where the fair weather field is positive.

KWAJEX

The purpose of the KWAJalein EXperiment was to provide TRMM underflight observations with a variety of instrumentation on board the NASA DC-8. These observations, made with both active and passive instrumentation, will provide verification and calibration data for the instruments on the TRMM spacecraft.

LAND CLASSIFICATION

The characterization of land by specific surface types such as desert, dense vegetation, and arable soil.

LAND SURFACE TEMPERATURE

The temperature in Kelvin of the air approximately 10 meters above the earth's surface.

LASE

LASE is an airborne DIAL (Differential Absorption Lidar) system used to measure water vapor, aerosols, Lidar) system used to measure water vapor, aerosols, and clouds throughout the troposphere. LASE operates by locking to a strong water vapor line and electronically tuning to any spectral position on the absorption line to choose the suitable absorption cross-section for optimum measurements over a range of water vapor concentrations in the atmosphere.

LASER ABSORPTION SPECTROMETER

The Laser Absorption Spectrometer (LAS) is an autonomous instrument based on off-axis integrated cavity output spectroscopy used to measure in-situ carbon monoxide mixing ratios and to derive mixing ratio profiles.

LASER HYGROMETER

The Laser Hygrometer measures in situ water vapor content using a tuneable laser emitting at 1.37 microns. Absorption at that wavelength is a function of water vapor content. Measuring the amount of absorption in an open path beyond the aircraft boundary layer, a value of water vapor pressure is made. The maximum sampling rate is 8 Hz, but the instrument is normally configured through the software for a 1Hz sampling rate.

LIGHTNING

The large spark produced by an abrupt discontinuous discharge of electricity through the air, resulting most often from the creation and separation of electric charge in cumulonimbus clouds.

LIGHTNING DETECTION AND RANGING

Lightning Detection and Ranging (LDAR) is a system of antennas which calculates, upon receiving a lightning generated radio frequency signal, the location in three dimensional space and the amplitude of the signal. With reference to the GHRC data sets, LDAR specifically refers to the system in place at the Kennedy Space Center used for basic research and support of Space Shuttle operations.

LIGHTNING FLASH

The total observed luminous phenomenon accompanying a lightning discharge.

LIGHTNING FLASH RATE

The rate of observed luminous phenomenon accompanying a lightning discharge.

LIP

Lightning Instrument Package measures the electric field above, below, and around the aircraft on which it is mounted. LIP consists of eight electric field mills, a conductivity probe, and the associated data system.

LIQUID WATER EQUIVALENT

The equivalent amount of liquid water contained in water vapor per unit volume of air.

LIQUID WATER PATH

The liquid water in any region, cloud or no cloud, based upon the physically based method of Greenwald et al.(1993) for ocean areas only. Usually measured in milligrams per square centimeter.

LIS

The Lightning Imaging Sensor (LIS) is an optical staring telescope on the Tropical Rainfall Measuring Mission (TRMM) satellite designed as an on orbit lightning detector functioning in day or night conditions. With a field of view of 600x600 kilometers, a resolution of 10 kilometers and imaging every 2 milliseconds (500 images per second) at 777 microns, the on board software compares successive images. Brightness changes between successive images satisfying specified criteria are located both temporally and spatially, and reported to the LIS Science Computing Facility at the Marshall Space Flight Center (MSFC).

LIS VALIDATION

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LONGWAVE RADIATION

Energy radiated or transmitted in the wavelengths longer than 4 micrometers portion of the spectrum.

LOWER STRATOSPHERE TEMPERATURE

Atmospheric temperature from 150 hPa to 30 hPa (rather than from the tropopause to an altitude of 20 km).

LOWER TROPOSPHERE TEMPERATURE

Atmospheric temperature from the earth's surface to 500 hPa (rather than to 10km).

LYMAN-ALPHA HYGROMETER

A device which uses light at 121.6 nm (also known as Lyman-alpha light) to photodissociate water in a sample chamber to produce excited OH radicals. The fluorescence from these radicals at 309 nm is detected with a phototube and counting system yielding the total water amount in the sample.

NASA Information Contact: Michael Goodman, Global Hydrology and Climate Center GHRC Web Curator: GHRC Web Team Last update: Friday, 13-Sep-02 09:37:01 CDT If you have trouble viewing or navigating this page, please contact GHRC User Services. U.S. Government Compliance report.