Glossary of Terms and Acronyms - P - S

PACIFIC OCEAN

Relating to the islands in the Pacific Ocean

PARTICLE SPECTROMETER

A device that records the two dimensional shadows of particles as they pass through a focussed laser beam.

PARTICLE SPECTROMETER

none provided

PHOTOMETER

An instrument used to measure luminous intensity, illumination, and other photometric quantities.

PIP

The Precipitation Imaging Probe (PIP) is an optical spectrometer that measures the size and shape of particles from 100 micrometers to 6200 micrometers. It is the classic airborne 2-Dimensional imaging probe, with the expanded capability of the 64-element diode array and fast Digital Signal Processing electronics.

PITOT-STATIC SYSTEM

Pitot-Static system is a device consisting of two parts, a pitot tube and a static port. The pitot tube is an open tube aimed into the direction of flight which allows air to flow into it thus measuring total pressure. The static port is aligned so that air flows across, not into, the port. This measures static pressure of the air. The arithmetic difference of the two measured pressures (Pt-Ps) is used to determine indicated airspeed.

PITOT_STATIC SYSTEM

A device consisting of two parts, a pitot tube and a static port. The pitot tube is an open tube aimed into the direction of flight which allows air to flow into it thus measuring total pressure. The static port is aligned so that air flows across, not into, the port. This measures static pressure of the air. The arithmetic difference of the two measured pressures (Pt-Ps) is used to determine airspeed.

PLANETARY BOUNDARY LAYER HEIGHT

The height of the atmospheric layer from the Earth's surface up to an altitude of about 1 kilometer in which wind speed and direction are affected by frictional interaction with objects on the Earth's surface.

PM-ESIP

The PM-ESIP will provide science researchers and users with the capability to interactively customize and receive hydrologic data sets for use in process studies and regional and global climate studies. It will provide a framework and a process for creating, supporting, and distributing both producer and customer defined data sets for the broader Earth Observing System (EOS) science community, incorporating emerging technologies such as data content based search (data mining) and data production, gridding, and formatting on demand. PM-ESIP datasets will be important for researching long term natural and human induced climate change ("global warming"), seasonal and interannual climate variability, regional assessments, and atmospheric process studies.

PMS 2D-C PROBE

The Particle Measuring System Two Dimentional Cloud and Precipitation (2D-c) Probe records the two dimensional shadows of cloud hydrometeors as they pass through a focussed He-Ne laser beam in the size range 25-800 micrometers.

PMS 2D-P PROBE

The Particle Measuring System (PMS) Two Dimensional Cloud and Precipitation (2D-P) Probe records the two dimensional shadows of hydrometeors as they pass through a focussed He-Ne laser beam.

PMS 2D-S PROBE

An aircraft mounted Particle Measuring System (PMS) 2D-Stereo probe is a probe that measures radiation and microphysical properties of the cloud layers in two dimensions where laser beams overlap.

PR-2

The Second Generation Precipitation Radar (PR-2) is a dual-frequency, Doppler, dual-polarization radar system that includes digital, real-time pulse compression, extremely compact RF electronics, and a large deployable dual-frequency cylindrical parabolic antenna subsystem.

PRECIPITABLE WATER

The total atmospheric water vapor contained in a vertical column of unit cross-sectional area extending between any two specified levels. Usually measured in milligrams per square centimeter.

PRECIPITATION

Any or all of the forms of water particles, whether liquid or solid, that fall from the atmosphere. Measured in either millimeters per hour or inches per hour.

PRECIPITATION AMOUNT

The total measured precipitation collected over a specified period of time, usually one day.

PRECIPITATION RATE

Any or all of the forms of water particles, whether liquid or solid, that fall from the atmosphere. Measured in either millimeters per hour or inches per hour.

PSR

The Polarimetric Scanning Radiometer (PSR) is a versatile airborne microwave imaging radiometer developed by the Georgia Institute of Technology and the NOAA Environmental Technology Laboratoryfor the purpose of obtaining polarimetric microwave emission imagery of the Earth's oceans, land, ice, clouds, and precipitation.

PYRANOMETER

An instrument that measures shortwave radiation over the whole hemisphere.

PYRHELIOMETER

Any of various devices that measure all the intensity of solar radiation received at the Earth.

RADAR BACKSCATTER

The scattering of radiation in a direction opposite to that of the incident radiation due to reflection of the transmitted radar signal back towards the instrument.

RADAR REFLECTIVITY

The measure of the efficiency of a radar target in intercepting and returning radio energy. It depends upon the size, shape, aspect and the dielectric properties of the surface of the target.

RADIANCE

The radiant power per unit area per solid angle in a given direction within a given wavelength interval. (watts/m squared - steradian).

RADIO WAVE FLUX

The time rate of change of radio waveforms.

RADIOSONDE

A lightweight package of weather instruments fitted with a radio transmitter and carried aloft by a balloon. Radiosondes carry temperature, pressure and relative humidity sensors and report up to six variables: pressure, geopotential height, temperature, dewpoint depression, wind direction and wind speed.

RADIOSONDE NETWORK

A network of well-distributed radiosonde stations from which variables such as pressure, geopotential height, temperature, dewpoint depression, wind direction and wind speed are obtained.

RAIN

Precipitation in the form of liquid water droplets greater than 0.5 mm condensed from vapor in the atmosphere. If widely scattered, the drop size may be smaller.

RAIN GAUGE

An instrument that collects and measures the amount of rainfall, expressed in inches or centimeters of depth.

RAWINSONDE

A device for upper-air observation that analyzes wind speed and direction, temperature, atmospheric pressure, and relative humidity by means of a balloon-borne adiosonde. A rawinsonde has on board GPS, LORAN, or OMEGA navigation to derive windspeeds and directions.

RESEARCH VESSEL

A vessel designed to float on or in the water (including ships, submarines, boats, and barges) used for scientific research.

RF ANTENNA

Radio Frequency Antenna: An instrument receiving directional radiowaves. Can be used to identify cloud-to-ground lightning locations by applying multiple station triangulation on the electromagnetic radiation released by the lightning and detected by the antenna.

ROTATING DIPOLE 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.

SATELLITE

A man-made vehicle orbiting the earth or other celestial body

SCANNING RAMAN LIDAR

The Scanning Raman Lidar (Light Detection and Ranging) is an instrument designed to determine the composition and vertical distribution of several atmospheric constituents, specifically water vapor and aerosols. The SRL was located on Andros Island during the CAMEX3 campaign, and operated nearly every night (exceptions noted) throughout the period 6 August -20 September 98.

SCATTERING

The interaction between radiation in the atmosphere and air molecules or suspended particles, resulting in the diffusion of the radiation in all directions but involving no loss of radiant energy.

SEA SURFACE TEMPERATURE

A measure of the thermal energy at or near the air/water interface of the sea or ocean. The depth of the surface layer depends on the method of measurement. Units are typically in degrees Fahrenheit (F) or Celsius (C) or in Kelvins (K).

SEARCHCOIL MAGNETOMETER

Variations in magnetic fields are measured along three orthogonal components with respect to the aircraft.

SENSOR COUNTS

Raw sensor and calibration satellite data that can be processed into Antenna Temperatures.

SFERICS DETECTOR

The sferics detector detects the impulsive radio noise emitted by a lightning strike in the Very Low Frequency (VLF) spectrum between 7 and 15 kHz. In the VLF portion of the radio spectrum sferics propagate thousands of kilometers through the earth-ionosphere waveguide.

SHIP

A large seagoing vessel propelled by power or sail

SHORTWAVE RADIATION

The radiant energy emitted from the sun, in the visible and near ultraviolet wavelengths of the electromagnetic spectrum.

SLOW 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.

SMART

The Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) is a portable 5 cm Doppler radar. All equipment- antenna, power generator, processors and readout computers are truck mounted to provide maximum transportability.

SMART-COMMIT

The SMART-COMMIT system consists of a suite of insitu and remote sensing instruments that measures parameters which characterize constituents of the atmosphere at a given location. Some of the included instrumentation are the AERI, a micropulse lidar, radiosonde, microwave radiometer, nephlometers and total sky imager.

SMMR

Scanning Multichannel Microwave Radiometer: a ten channel passive microwave instrument using six conventional Dicke-type radiometers. It delivered orthogonally polarized antenna temperature data at five frequencies (6.6, 10.69, 18.0, 21.0, and 37.0 GHz).

SODAR

The Doppler sodar operates near 2000 Hz frequency (tunable between 1800-2200 Hz) and measures wind components along three beams, including a vertical beam. The backscattered power is proportional to the temperature structure function, CT2, and provides information on ABL stability and turbulence characteristics. Returned values include horizontal winds, vertical velocity, and virtual temperature profiles when in Radio Acoustic Sounding System or RASS mode.

SOLAR IRRADIANCE

The total solar radiant energy flowing across a unit area normal to the direction of propagation and located at the mean distance of the Earth from the Sun.

SOLAR RADIATION

A measure of the electromagnetic energy that comes from the sun only.

SPECTROMETER

Any of various optical instruments, for measuring wave length, index of refraction, etc.

SSM/I

Special Sensor Microwave/Imager: a passive microwave radiometric system that receives both horizontally and vertically linearly polarized radiation at 19.3,37.0, and 85.5 GHz and vertical only at 22.2 GHz.

SSM/T1

The Special Sensor Microwave Atmospheric Temperature Sounder consists of seven microwave channels with atmospheric sensitivity in the oxygen absorption band, at frequencies ranging from 50.5 to 59.4 GHz, with one channel acting as a surface window channel.

SSM/T2

The Special Sensor Microwave Water Vapor Sounder is a scanning, five channel, passive and total power microwave radiometer system consisting of five channels: three water vapor channels centered around the 183.31 GHz water vapor line, a 91 GHz channel, a 150 GHz channel.

STATIC PRESSURE

The pressure of undisturbed (static) air

STREAM FLOW

The rate of water flowing in a channel, usually measured in cubic feet per second.

STREAM GAUGE

A device for measuring the elevation of the water surface in a stream.

STREAMFLOW

The rate of water flowing in a channel, usually measured in cubic feet per second.

STREAMFLOW STATION

A data collection site for streamflow discharge, where streamflow is defined as the rate of water flowing in a channel, usually measured in cubic feet per second.

SURFACE

The land or oceanic interface with the atmosphere

SURFACE ACOUSTIC WAVE HYGROMETER

The Surface Acoustic Wave (SAW) device is a quartz crystal designed to support high-frequency acoustic oscillations. Because these oscillations are quite sensitive to surface effects, condensation produces a measurable shift in the resonand frequency of the SAW device. A two-stage thermo-electric cooler electronically heats or cools the SAW device maintaining it at the dewpoint, while a platinum resistor is used to monitor the dewpoint temperature.

SURFACE AIR TEMPERATURE

The temperature of the air near the surface of the earth.

SURFACE HUMIDITY

The amount of water vapor in the air near the surface of the earth.

SURFACE LEVEL WINDS

The wind measured at a surface observing station or recorded at an observing site at the ocean surface.

SURFACE PRESSURE

The atmospheric pressure at a given location on the surface of the Earth.

SURFACE WINDS

The speed and direction of wind (measured directly or calculated from remotely sensed data) near the earth's land (or water) surface. Usually varies from 2 to 10 meters above the surface.

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.