HOPKINS GLOSSARY OF WEATHER TERMS R
radar (radio detection and ranging)
- An electronic instrument that broadcasts a microwave electromagnetic
radiation signal and receives the reflected portion of
this signal from a target. In meteorology, the signal from a
weather radar unit is reflected and scattered from precipitation
particles (rain, hail, snow) to determine the location, height
and intensity of precipitation areas; comparison of multiple radar
echoes permits determination of changes in intensity and the speed
and direction of the areal movement. See also Doppler radar
- An instrument that intercepts and uses electromagnetic radiation
in the radio portion of the spectrum to determine the direction
of the radio transmitter.
- Any instrument or device that senses and measures the radiant
energy in electromagnetic radiation.
- A small, expendable, balloon-borne instrument package with
a radio transmitter used to measure the air temperature, pressure
and humidity of the atmosphere above the earth's surface to approximately
30 km; the wind direction and wind speed aloft are determined
from ground based tracking of the radiosonde; see also rawinsonde
. The weather data are electronically transmitted to the launch
station, where they are decoded and plotted as a sounding.
rain gauge- Any instrument used to measure the total
amount of precipitation that falls upon a given unit area
during a specified time interval. Gauges can be adapted to collect
snow for the determination of liquid water equivalent of snowfall.
Recording rain gauges measure precipitation rates over
fixed time intervals to provide an indication of rainfall intensity
. Essentially all gauges are calibrated in units of depth
of accumulation, e.g., millimeters or inches.
range - (1) The distance between two objects, usually
an observation point and an object under observation, see also
slant range and horizontal range. (2) A maximum
distance attributable to some process, as in visual range, radar
range or the "range'' of an aircraft.
Range Height Indicator (RHI)
rawinsonde - An upper-air weather observation
system (from the surface to approximately 30 km altitude) made
by balloon-borne instrument package (radiosonde)
that provides direct measurement of ambient air temperature, pressure,
and humidity as well as the evaluation of the wind speed and direction
aloft by means of tracking the position change of the radiosonde
by directional radio techniques.
- At a given ambient air temperature, the dimensionless ratio
between the actual vapor pressure of air to the saturation
vapor pressure. Corresponding ratios of mixing ratio can be
substituted. Relative humidity is usually expressed as a percentage.
- An electrical-type thermometer that utilzes a thermal
element consisting of a material whose electrical resistance varies
with temperature. A thermistor is a variety of resistance
therometer commonly used onboard radiosondes.
- Acronym for ROcket Balloon INstrument.
- An instrument package carried aloft by a meteorological
rocket to make a measure one or more weather elements in a
sounding of the upper atmosphere, at altitudes usually higher
than can be obtained by radiosonde or aircraft.
- A probe of the upper atmosphere with a meteorological
rocket to produce a record of the vertical variation
of a weather element such as air temperature, density, composition
Last update 6 June 1996
Edward J. Hopkins, Ph.D.
Department of Atmospheric and Oceanic Sciences
University of Wisconsin-Madison