Brandon, preparing to launch a balloon and radiosonde at night.

Radiosondes are tied to a large balloon and released twice daily: 11 A.M. and P.M. A Radiosonde's position is determined via GPS, and that data, along with pressure, temperature and humidity is transmitted back to Kwajalein via radio frequency. Data obtained from the radiosonde's flight include wind speed and direction, temperature, dew point temperature, relative humidity, air pressure and density. Based on the variations of wind speed and direction between altitudes, shear values are calculated. While flying to and from Kwajalein you've likely experienced shear of moderate value, otherwise known as turbulence.

Weather data collected from upper air soundings have an important role in the field of meteorology.

Forecasters use the latest soundings to determine the state of the local atmosphere. Based on the moisture content and how much the atmosphere cools with height, a forecaster can determine whether thunderstorms are likely to develop or not. While thunderstorms do not occur very often around Kwajalein, this information is very important in the Midwest when forecasting the potential for a severe weather outbreak in the spring or summer.

Computer weather models use the data from upper air soundings to supplement other weather data collected from airplanes, satellites, ships, sea buoys and ground observing stations. (The RTS weather station is also a 24-hour manned observing station.) All data is then used by computers to create forecast guidance models so it is important that data is collected in a consistent and timely manner.

Finally, upper air data is used by climatologists and researchers to measure atmospheric changes over the years to define trends within long-duration weather patterns. Of particular importance to the tropical Pacific are levels of wind shear (changing wind directions and speeds with height). Areas with strong shear are less likely to see the development of tropical cyclones. Further, upper air data helps better define global circulation patterns: what causes the trade winds and the doldrums, why do nor'easters develop in the winter and spring and drop feet of snow in New England?

Now that you know about the weather side of balloon launches, you may be wondering just what happens to the balloon and radiosonde. No, they don't go into orbit. A two-step process usually occurs about 100% of the time. First the balloon pops, then gravity pulls everything down. Balloon specialist, Kevin Butler says that many soundings reach altitudes of 90,000 feet (17 miles) before the balloon pops. In such high altitude and low pressure a 5 foot diameter balloon at the surface can expand to 25 feet in diameter!

Although all balloons and radiosondes do find their way back onto the planet, very few are ever found. Even more inconceivable is for one to be retrieved in the middle of the ocean. However, while 7^th Grader Keegan Gray was walking up toward North Point recently (April 19^th), he saw what he thought was a blanket hanging in a tree to dry. Upon closer inspection, he found that it was not a blanket but a radiosonde and balloon and soon called the weather office.

Keegan, with radiosonde and balloon.

Brandon Aydlett, the forecaster on shift who received Keegan's call, roughly estimated that the varying wind directions with height sent the balloon flying in a figure-8 pattern which allowed the balloon to reenter Kwajalein airspace and lodge itself in a tree.

Keegan's balloon lived a fairly typical life: it was launched that same morning at 11, rose to about 76,000 feet (14.5 miles), and endured temperatures as cold as -119°F before falling back down to Earth.

As data collection becomes ever more important to meteorologists, weather modeling and research, radiosondes and balloons will continue to play a pivotal role in upper air data gathering. Keep your eyes open, perhaps you will find a radiosonde and balloon one day!