How is Data Collected From the Upper Air?

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Weather balloons are released twice-daily 0z/12z (Zulu, Coordinated Universal Time or Greenwich Mean Time) for coordination across the globe. A radiosonde is a small expendable instrument package attached to the weather balloon to make observations of the atmosphere. Measurements of pressure, temperature and humidity data are collected.

Wind speed and direction are calculated by tracking the position of the instrument package with GPS.