Plain English Meaning
A tiny radio attached to a weather balloon that sends weather readings down to a station on the ground while the balloon climbs.
Full Definition
A small, low-power radio transmitter carried aloft by a weather balloon as part of a radiosonde, used to send temperature, humidity, and pressure measurements back to a ground receiving station as the balloon rises through the atmosphere.
Context Anchor
Seen in upper-air observation discussions, especially when describing weather balloons and the instruments they carry.