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How do weather balloons collect information about the upper atmosphere?

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Weather forecasting Doppler radars, such as this one operated by the U.S. National Weather Service at New Underwood, South Dakota, extract the Doppler frequency shift of the echo produced by a moving target by noting how much the frequency of the received signal differs from the frequency of the signal that was transmitted.

Weather balloons collect data about the upper atmosphere by carrying an instrument package called a radiosonde into the sky. These balloons, typically made of high-quality rubber or latex, ascend at a predetermined rate to altitudes of 30,000 meters or more.123

As the radiosonde ascends, it measures key atmospheric variables, including:

Temperature and Humidity: These are measured using sensors such as bimetallic strips, wires, or specialized hygrometers.13
Pressure: An aneroid capsule or mechanical bellows detects changes in atmospheric pressure, which also helps trigger the transmission of other data.1

This information is radioed back to a ground station in real time. To determine wind speed and direction, the balloon’s position is tracked as it drifts. Historically, this was done using a theodolite or radar, but modern systems primarily utilize GPS technology. These twice-daily launches provide the essential data used to benchmark numerical weather prediction models and create synoptic maps of the upper atmosphere.134