|
|
|
| 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).
|
 |
| 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. |
 |
  
|
