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The information in this document has been derived from the National
Snow and Ice Data Center's Radiosonde Instrument Document.
Summary:
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.
A typical radiosonde configuration consists of a baroswitch
that implements a temperature-compensated aneroid capsule to move a
lever arm across a commutator plate, a lead-carbonate coated rod
thermistor about 0.7 mm in diameter and 1-2 cm long, and a carbon
humidity element that swells with a rise in humidity, made of a glass
or plastic substrate thinly coated with a fibrous material.
A radio
transmitter and ground-based radar, navagation aid, or other tracking
system complete the rawinsonde instrumentation.
Measurements are used in weather forecasting, and are of increasing
interest to those studying climate change.
Table of Contents:
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- Radiosonde
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- Upper air measurements began with temperature soundings made in Glasgow, 1749,
using a thermometer attached to a kite. Subsequent efforts in the 18th and
19th centuries progressed through the use of box kites, manned balloons, and
free balloons and expanded to include measurements of temperature, pressure,
electrical field and humidity.
Early devices were replaced by aircraft carrying first, meteorographs, and then
radiosondes. Today,
rawinsondes are flown on balloons made of natural or synthetic rubber, which,
expanding as they ascend, will eventually burst. Some balloon designs are
vented, such that the ballon descends and can be recovered, others are
tethered, and other, superpressure balloons are designed to fly anywhere
from three days to several months.
Given the limitations of the platform, rawinsondes must be expendable and
factor in their design considerations the possibility of being struck by jet
aircraft (Lally 1985).
Radiosonde systems comprise pressure, temperature and humidity sensors, c
omplemented by transmitting electronics. Winds are calculated based on ascent
velocity and air density. As concerns upper air practice, the World Meteorological
Organization sets accuracy requirements and performance limits for instruments
used to derive these parameters.
Pressure must be measured to an accuracy of +/- 1 mb (1 mb = 1 hPa), temperature
to an accuracy of +/-.5 degrees Celsius, and relative humidity to an accuracy
of +/- 5 percent.
1989 tests of several models of radiosondes used in the United States in the
1980's showed pressure measured to an accuracy of about +/- 2mb, temperature
measured to an accuracy of +/-0.3 degrees Celsius, and relative humidity to
an accuracy of +/- 2 percent.(Elliott and Gaffen 1991).
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- Soundings are used in synoptic meteorology and climatology.
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- Instrument performance is sometimes seen to degrade in cold,
dry regions, because the instrument responds to the number of water
molecules present in the atmosphere.
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- The number and variety of instruments in use (see section 4) make
it infeasible to describe the particulars of each; the following information,
provided courtesy of
Vaisala Inc.,
is representative and does not constitute a product endorsement by
GSFC.
The following description is reprinted with permission.
Please direct all questions to the manufacturer.
- The PTU (pressure, temperature, humidity) measuring system of
the Vaisala RS 80 radiosonde is based on a time multiplexing principle.
Each of the capacitive sensors controls the frequency of the AF
oscillator through an electronic commutator switch. The switch is
formed by solid state logic gates. The oscillator frequency is
fed through a modulator to the radio transmitter....
A water-activated battery provides power for the radiosonde.
Instrument Layout, Design, and Measurement Geometry
The frequency generated by the transducer is the measure of the meteorological parameters.
Relationship between the frequency and corresponding parameter value is established
in the calibration process
The set of solid state sensors consists of an aneroid capsule (BAROCAP) with capacitive
transducers in the inside vacuum, a ceramic temperature sensor (THERMOCAP) and
a thin film humidity sensor (HUMICAP) which is an improved version of the one produced earlier.
All the sensors are capacitive with compatible dynamic ranges which essentially
simplifies the transducer electronics.
In the radiosonde only one reference capacitor is needed to eliminate the
influence of drift of the transducer electronics. The basic capacitance of the
transducer oscillator circuit is used as the second reference.
Other viewpoints when selecting the sensing principle were the existence of the
capacitive humidity sensor, a simple stable and frictionless barometer
construction and small risk of self-heating problems in temperature and humidity
measurements.
The transducer circuit developed for the RS 80 radiosondes is capable of
measuring with a resolution of 1 fF. The electronic
circuit is insensitive to changes of stray capacitaces between sensor terminals
and electrical ground. This is of basic importance for the feasibility of the sensor design.
There is an additional temperature sensor to measure the temperature of the pressure
sensor for elimination of its temperature dependence.
from: RS 80 Radiosondes, Vaisala Inc. Upper Air Systems product information,
reference no. R0422-2, 26 May 1989.
Data collected in the Historic Arctic Rawinsonde Archive consists of land-based
soundings taken one to four times per day for all available Arctic stations
poleward of 65 degrees North. Most stations are located between 65 and 78 degrees north.
Long term (30) year records are available for about 50 stations, most
begin in 1958 and extend through 1987. Additional soundings obtained from the
National Center for Atmospheric Research extend the data base through 1991.
Soundings typically extend to at least 300 mb and contain a mixture of reports
at mandatory (that is, surface, 1000 mb, 850 mb, 700 mb, 500 mb, 400 mb, 300 mb)
and significant levels. Six variables, pressure, geopotential height, temperature,
dewpoint depression, wind direction and wind speed are reported with associated quality
codes at the 20 to 40 levels usually available per sounding.
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- This information is not available at this time.
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- Radiosondes carry pressure, temperature and humidity sensors.
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- This information is not available at this time.
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- This information is not available at this time.
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- This is not available at this time.
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- This information is not available at this time.
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- None other available at this time.
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Elliott, W. P., and D.J. Gaffen. 1991. On the utility of
radiosonde humidity archives for climate studies.
Bulletin American Meteorological Society.72(10):1507-1520.
Garand, L., C. Grassotti, J. Halle, and G. L. Klein. 1992.
On differences in radiosonde humidity - reporting practices
and their implications for
numerical weather prediction and remote sensing.
Bulletin American Meteorological Society.73(9):1417-1423.
Lally, V. E. 1985. Upper Air in situ Observing Systems.
Handbook of Applied Meteorology. David D. Houghton, editor.
John Wiley & Sons, Inc. 352 -360.
Vaisala Inc. 1989. RS 80 Radiosondes. Upper-Air Systems product
information. Reference No. R0422-2. Vaisala Inc., 100 Commerce Way, Woburn, MA 01801.
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- EOSDIS glossary
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- EOSDIS acronyms
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Change History
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