Laura Espinosa, age 11, of San Diego, California, for her question:
How useful are weather balloons?
Today, balloons were launched aloft from 100 or so widely separated weather stations across North America. In regions where the skies were clear, there were two, three or four launchings. Those high flying weather balloons gathered a lot of the necessary details to help your weatherman forecast tomorrow's events.
The first weather balloons had a hair raising history, but they proved to be far more useful than anybody expected. Nowadays we launch them with only their automatic instruments to detect and relay data back to the ground. But in the last century, they were launched with one or more persons abroad. In 1843, John Wise rode his balloon through a Pennsylvania thunderstorm. He was swept up and down and whirled around and his whiskers froze in the cold. But his reports from upstairs helped:.u§ understand the turbulent nature of a thunderhead. In 1821, William Redfield took a balloon flight over Connecticut after a hurricane. His survey from aloft showed that trees in different parts of the state were uprooted in different directions. This gave the first hint that a hurricane spins.
In the 1860's, an English scientist named James Glaisher made several balloon trips with a special instrument panel to observe the weather aloft. He had the use of two barometers, a pair of field glasses, a compass and several thermometers. On one trip he ascended 29,000 feet and fainted from cold and lack of oxygen. His pilot ,just managed to open the right valve with his teeth and the balloon came down with no lives lost.
These and other early experiments hinted that the weather upstairs is very different from the downstairs weather. However, the two levels apparently were related. As meteorologists investigated farther, it became plain that the thin, colder air aloft definitely is related to the weathery air above the ground. The temperature, pressure and humidity of the upper air tell meteorologists a lot about the weather conditions that are brewing down here. This is why our weather stations launch many thousands of balloons each year. The data they gather every day is added to the general weather picture.
The usual weather balloon carries automatic electronic instruments to check the temperature, humidity and barometric pressure of the air aloft. As a rule, it dangles a small electronic radiosonde that relays the findings back to the ground weather station. The balloon ascends at about 1,000 feet per minute and usually pops at about 70,000 feet. It may have a skin of metal foil that can be tracked by ground radar to show the direction of the upper level winds.
In the 1960's, a whopping balloon was launched from a carrier. This so called sky¬hook ascended 110,000 feet, stayed aloft for 33 1/2 hours and relayed some surprising information about wind patterns in the stratosphere. Ordinary weather balloons have proved so useful that better ones are planned for the future. One plan calls for launching 2,000 permanent balloons to drift on high. They could relay a global picture of temperature, pressure and humidity, plus continuous information about the upper winds.