Radiosonde

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Radiosonde being prepared for launch

A radiosonde (Sonde is German for probe) is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required. A rawinsonde is a radiosonde that is designed to also measure wind speed and direction. Colloquially, rawinsondes are usually referred to as radiosondes.

Modern radiosondes measure or calculate the following variables:

Pressure
Altitude
Geographical position (Latitude/Longitude)
Temperature
Relative humidity
Wind speed and direction

Less commonly, radionsondes may also measure ozone concentration.

1 Ascent
2 Routine Radiosonde Launches
3 Uses of Upper Air Observations
4 External links

[edit] Ascent

A rubber or latex balloon filled with either helium or hydrogen lifts the device up through the atmosphere. The maximum altitude to which the balloon ascends is determined by the diameter and thickness of the balloon. Balloon sizes can range from 150 grams to 3000 grams. As the balloon ascends through the atmosphere, the pressure decreases, causing the balloon to expand. Eventually, the balloon will expand to the extent that its skin will break, terminating the ascent. An 800 gram balloon will burst at about 30,000 meters (about 100,000 feet). The modern radiosonde communicates via radio with a computer that stores all the variables in real-time. The first rawinsondes were observed from the ground with a theodolite, and gave only a wind estimation by the position. Modern radiosondes can use a variety of mechanisms for determining wind speed and direction, such as Loran, radio direction finder, GPS and (in Canada only) Very low frequency. The weight of a radiosonde is typically 250 grams.

[edit] Routine Radiosonde Launches

Worldwide there are more than 800 radiosonde launch sites. Most countries share data with the rest of the world through international agreements. Nearly all routine radiosonde launches occur at 0000 UTC and 1200 UTC to provide an instantaneous snapshot of the atmosphere. This is especially important for numerical modeling. In the United States the National Weather Service is tasked with providing timely upper-air observations for use in weather forecasting, severe weather watches and warnings, and atmospheric research. It launches radiosondes from 92 stations in North America and the Pacific Islands twice daily. It also supports the operation of 10 radionsonde sites in the Caribbean.

[edit] Uses of Upper Air Observations

Raw upper air data is routinely ingested by numerical models. Forecasters often view the data in a graphical format such as a Skew-T log-P diagram or a Stüve diagram, both useful for the interpretation of the atmosphere's vertical profile of temperature and moisture.

Radiosonde data is an important component of numerical weather prediction. Because a sonde may drift several hundred kilometers during the 90 to 120 minute flight, there may be concern that this could introduce problems into the model initialization. However, this appears not to be so except perhaps locally in jet stream regions in the stratosphere [1].

In 1985 the Soviet Venus probes Vega 1 and Vega 2 each dropped a radiosonde into the atmosphere of Venus. The sondes could be tracked for two days.