Kevin Harris, age 12, of Fredericton Junction, New Brunswick, Canada for his question:

What is the purpose of weather balloons

The circulation of the atmosphere occurs on two levels. For example, the trade winds arrow toward the equator where the warm air rises, cools and blows back toward the poles. This upstairs level affects the global weather picture in the downstairs level. Weather balloons are sent aloft to gather high altitude data and relay it back to meteorology stations on the ground. As they rise, their instruments measure temperatures, pressure and humidity. Usually they carry dangling radiosondes that transmit continuous data. They often ascend to 75,000 feet and even to 125,000 feet    and then burst.

Every year, at least 600,000 weather balloons are launched from upper air sounding stations, pinpointed around the world. This data is assembled at central stations and computed together with information from the downstairs level. The weather is a global affair and data is exchanged on an international basis. High altitude balloons help the meteorologists form a picture of the weather circulation in the Northern and Southern Hemispheres.