The Radiosonde
Home Up The Radiosonde Uses of the  Data Maintenance Issues Frequency Issues

 

The term radiosonde is a contraction for radio-sounding device.  The instrument measures the ambient pressure, temperature, and moisture.   When attached to a weather balloon filled with a lighter-than-air gas, radiosondes can attain heights in excess of 30 kilometers.  Winds are determined from changes in the radiosonde position during the flight.  The thermodynamic and wind data information are formulated into a "rawinsonde" observation.  The National Weather Service currently uses Vaisala RS-80-57H, Sippican VIZ-B2, and Sippican Loran-Microsondes (RS-80-57H and VIZ-B2 radiosondes are shown to the right).

 

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The radiosonde transmits its data to a ground-based telemetry system (antenna and receiver).  This telemetry system receives the signals and forwards them to another module (signal processing system) to be decoded into meteorological units.  Data are then passed to a computer for collection of data for the entire sounding and formulation of the observation products for general distribution.   When the balloon reaches it elastic limit and bursts, a parachute slows the descent of the radiosonde to the ground.  Recovered radiosondes can be returned to the factory for reconditioning and re-flown, thus reducing the overall cost of operating the program.

 

A radiotheodolite (i.e., radio direction finder) is used today at most stations (see photograph to the right) to track the radiosonde as it ascends and receives the radiosonde signals.  These systems were purchased in the 1950s and are now obsolete.  Six of the stations use a Sippican W9000 Loran System and five use an ATIR radiotheodite.  The replacement system will use the Global Positioning System to track the position of radiosondes.        WBRT2.jpg (10988 bytes)

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Date Last Modified: December 6, 2001