Background on Driftsondes
Eight driftsondes were
successfully launched from Zinder, Niger. Six moved across
Africa and the tropical Atlantic.
The driftsondes released a total of about
200 dropsondes between Niger and the tropical
The dropsondes gathered data from within
the circulations that became hurricanes
Florence and Gordon.
What is a driftsonde?
It’s a new type of observing system that shows great promise
in tracking weather above hard-to-reach parts of the globe, such as the
remote Pacific and Atlantic oceans. A driftsonde consists of a large
balloon (roughly 30 feet tall), a device that sends and receives radio
signals, and a gondola to hold instrument packages that descend by parachute.
This summer NCAR and the French space agency (CNES) collaborated to launch
the first driftsonde ever used in a weather research project. In this
partnership, CNES was responsible for the balloon system and NCAR developed
the gondola and instrument packages.
How does a driftsonde work?
The special type of balloon used in the driftsonde ascends to the lower
stratosphere, at heights of around 60,000 to 65,000 feet. It can remain
airborne for a week or longer, drifting with the winds that prevail
at these altitudes. Scientists at an operations center communicate
with the driftsonde through Iridium communications satellites. With
a remote command, they can release one of the instrument packages,
which is called a dropsonde. The dropsonde falls through the atmosphere,
collecting weather data twice per second and sending the data back
to the driftsonde gondola. Later, the information is relayed to the
operations center and then on to forecast centers.
Specs & stats
Each driftsonde gondola holds up to 40 dropsondes.
Each dropsonde weighs about 5 ounces and is
about the size of a small water bottle.
Each dropsonde takes about 20–30 minutes
to descend to Earth by parachute.
Why are driftsondes only now being used for weather research?
The idea for driftsondes was first conceived in the early 1970s, and
several tests were conducted in subsequent years. However, the power
communication technologies were insufficient at the
time, and the instruments were relatively bulky and
heavy, requiring expensive balloons to loft them. In
the last few years, miniaturized electronics have reduced the size, weight,
and power required for driftsonde instruments, and GPS-based communications
have become standard. The new technology is also more durable in the
stratosphere’s extreme cold.
What’s next for the driftsonde?
The use of driftsondes for hurricane genesis was made possible by
two major studies: THORPEX (The Observing System Research
and Predictability Experiment), a 10-year program under the World Meteorological
Organization designed to accelerate skill in predicting high-impact
weather events, and AMMA (the African Monsoon Multidisciplinary
Analysis), a multiyear program designed to advance understanding of
the West African monsoon. The next major deployment of driftsondes
in THORPEX will be for an Antarctic climate-change study in association
with the International Polar Year (2007-08) and a North Pacific
campaign in 2008 focused on predicting intense winter cyclones, floods,
severe thunderstorm outbreaks, and fire weather over North America.
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Office of Programs are operated by UCAR under the sponsorship of the
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or recommendations expressed in this publication do not necessarily reflect
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