A woman holding a weather ballon at a balloon releasing facility.

An everettpost.com and KRKO Radio listener recently found a strange box labeled radiosonde in his Arlington backyard and asked what is it? The overall answer is a weather balloon and the instrument package called a radiosonde can be reused by mailing it back using the attached mailing bag to a rehabilitation center in Kansas City, saving tax dollars. About one in five radiosondes are reused.

Weather balloons are launched simultaneously twice a day at midnight and noon Greenwich Mean Time (GMT) or 5 AM and PM Pacific Daylight Time from 900 locations around the world. The radiosonde from this weather balloon likely was launched from Quillayute on the North Washington coast, one of 92 launch sites in North America and the Pacific Islands. Other nearby weather balloon launch sites include Salem, Oregon; Spokane, Washington; Boise, Idaho; and Port Hardy on Vancouver Island.

These weather balloons collect information on temperature, humidity, pressure and wind direction and speed at various heights as the balloon rises in the atmosphere. The worldwide weather balloon launch provides a snapshot of Earth’s atmosphere from the surface to well above where jets fly.

The balloons themselves are made of latex. The balloon sides are about 0.051 millimeters (mm) thick or about 1/64th inch prior to launch and will be only about 0.0025 mm thick at a typical bursting altitude. The balloons are inflated with either helium or hydrogen and measure about 6 feet wide before release. As they rise, air pressure decreases and the balloon expands, often to about 20 feet in diameter before it bursts. The balloons can rise as high as 100,000 feet before they burst, but most burst between 40,000 and 80,000 feet.

The battery-powered radiosonde instrument package is attached below the balloon, collecting and transmitting data back to the launch site every few seconds as it rises. Ground sensors at the launch point also follow the balloon to measure wind direction and speed as the balloon rises. Once the balloon bursts, a parachute on the instrument package deploys and the radiosonde slowly falls back to the ground. In the case of our Arlington listener, the radiosonde found his backyard.

Weather balloons have been used to gather a vertical profile of the Earth’s atmosphere since the 1930s. Prior to that, brave open cockpit pilots would fly to as high as 18,000 feet to collect weather data. These pilots would use pigeons in a cage to gage when it was time to descend. When the pigeon fell asleep from a lack of oxygen at that high altitude, pilots would then descend to avoid also falling victim to the lack of oxygen. Prior to the use of aircraft to collect weather data aloft, kites were also used yet could not go very high in altitude.

A battery-powered radiosonde instrument package that is attached below a weather balloon, collecting and transmitting data back to the launch site every few seconds as it rises in the air.

Weather balloon data is one of the key initial weather data resources for meteorological models of how the atmosphere will behave in the future. Other data in these models include Doppler weather radar, surface observations on land and at sea, weather satellite data and more. Sometimes during significant weather events, as many as four weather balloons will be launched in and near the threatened region to help better forecast the impending adverse weather.

All these weather data sources are used to initiate the computer model runs with a current state of the atmosphere. These meteorological models of the atmosphere are what meteorologists use to help predict the weather including short-fused weather warnings like tornados and flash floods, as well as longer-term significant weather events like wind storms, hurricanes, and winter storms. Over the years with ever enhancing computer power and resolution, these computer models have continued to improve, providing meteorologists with more accurate weather prediction information.

Yet, near century-old weather balloon technology still plays a key role in today’s weather observation and prediction process around the world. If you ever find a radiosonde that floated into your backyard or perhaps while away from your home, be sure to mail it back so it can be reused again.

North Sound Meteorologist Ted Buehner worked more than 40 years for the National Weather Service (NWS) from 1977 to 2018. He is now an Everett Post Media team member. Together with Everett Post Weather Minute Podcasts, he provides morning and afternoon commute traffic and weather updates on both KRKO and KXA Radio, and sports reporting on KRKO.