Weather balloons have been a very important part of the Global Observing System for decades, as they are the main source of above-ground data. They provide information to monitor the weather and predict atmospheric changes. All the world’s meteorologists use forecasting computer models that use data from weather balloons.
Millions of analyzes are collected worldwide every day: 50 satellites provide information from space, 1,650 buoys and 7,300 ships provide information from the ocean; 4,000 aircraft, 7,300 moored ships and 10,000 observation stations provide data on the ground. Added to this are almost 1000 weather balloons equipped with radiosondes.
Acting as stations in the atmosphere, radiosondes are attached to hot air balloons and released simultaneously from nearly 900 locations around the world. More than two-thirds of the stations make observations at midnight and noon Greenwich Meridian. Between 100 and 200 stations make observations once a day.
The balloon flights last about two hours and make measurements of pressure, wind speed, temperature and humidity from just above the ground to heights of up to 35 kilometers. They can travel many miles before the balloon bursts and parachutes to earth.
Proof of extreme conditions
Balloons are made from either natural rubber latex or a neoprene-based synthetic latex. Synthetic latex balloons have a much slower decomposition rate than natural rubber latex, so the latter is preferred. The balloons are filled with hydrogen or helium.
When released, the balloons are less than two meters wide. During the ascent, the air pressure around the balloon decreases, allowing the gas in the balloon to expand to about twenty feet in diameter.
The radiosondes attached to the balloons withstand temperatures of up to 95 degrees Celsius below zero, relative humidity of 0% to 100%, very low atmospheric pressures, ice, rain, storms and strong winds.
A transmitter on the radiosonde sends the data to tracking equipment on the ground every one to two seconds. By following the position of the radiosonde, which is powered by a small battery, the speed and direction of the wind can also be calculated.
In ocean areas, radiosonde observations are made by ships equipped with automated atmospheric sounding facilities.
Stormy clouds form over the ocean at Port Macquarie, Australia. (Photo: WMO/Will Eades)
Continuous data flow, key to accurate forecasts
Experts are constantly doing research to improve radiosondes to ensure that they can make accurate and consistent measurements. Obtaining stable and consistent measurements is vital for recording weather conditions. Furthermore, it is essential that there are no data interruptions and that the data itself is not adversely affected by a change in technology.
There is a constant effort to produce environmentally friendly radiosondes and balloons, identifying materials that meet functional requirements and are biodegradable.
To further strengthen the network of weather balloons and the surface observation network, and provide even more data to weather forecast models, the World Meteorological Organization established the Global Basic Observing Network, supported by the Funding Facility for Systematic Observations. (Source: UN News)