Weather instruments come in all shapes and sizes. Some are in orbit while others are anchored to the ground.  They allow us to measure different parameters like air temperature, air pressure, humidity, wind speed and direction.  These instruments are often standalones, but can be clustered together. And every now and again, they fall from the sky.

Yesterday, Todd Veinot’s niece Madison found an intriguing little box outside his home in Upper Northfield, Lunenburg county, NS.  They were wondering if it was a weather balloon from Environment Canada.  Well Madison, it certainly was.

Government weather agencies release these balloons from weather stations in order to get a clearer picture of the air mass overhead. The Meteorological Service of Canada operates a network of 31 upper air observing stations.

The box you found is called a radiosonde.  The radiosonde is a small, instrument package suspended below a large balloon inflated with hydrogen or helium gas.  As the radiosonde rises at about 300 meters/minute, sensors on the radiosonde transmit pressure, temperature, relative humidity and GPS position data each second. These sensors are linked to a battery powered radio transmitter that sends the sensor measurements to a ground tracking antenna.  Wind speed and direction aloft are also obtained by tracking the position of the radiosonde in flight using GPS.

When released, the balloon is about 1.5 meters in diameter and gradually expands in size as it rises because of the decreasing air pressure.  When the balloon reaches a diameter of 6 to 8 meters, it bursts.   A small, orange colored parachute slows the descent of the radiosonde, minimizing the danger to anyone below.

Last week, highway maintenance workers with SNC LAVALIN found a National Weather Service (US) radiosonde near Woodstock NB.  It came with a self-addressed envelope – for return to Missouri!

Worldwide, there are over 800 upper-air observation stations and through international agreements,  data are exchanged between countries.   Most upper air stations are located in the Northern Hemisphere and all observations are usually taken at the same time each day -365 days a year.


Chief Meteorologist

Cindy Day