weather+balloons-laurel

Page 387 tells how weather balloons work. It explains that they have been used since World War 2 and there are 70 launching sites in the United States. Weather balloons are used to find temperature, pressure, relative humidity, and wind velocity in the upper atmosphere. They work by first being inflated with helium or hydrogen to a diameter of about 2 meters. They rise into the sky with an insturment package attached by a 15 meter cord. While n the air the instruments record and transmit temperature, relative humidity, and barometric pressure. As the pressure in the atmosphere decreases the balloon expands and the balloon rises higher. When it reaches 30 kilometers, the volume of the gas is so high that the balloon bursts. A parachute carries the package containing a radio transmitter and measuring instruments to the ground.

1.Weather balloons did not become obsolete because even though weather satellites obtain important scientific information, they do not record the direct temperature of the earth. Balloons are also cheaper to make therefore there are many more weather balloons sent up then satellites in space. Furthermore weather balloons gather information for a specific area everyday, and weather satellites orbit the earth so they do not record an area's daily climate. Weather balloons are important to the everyday person and weather satellites pertain more to scientists who are studing the earth.

2.So they know what gasses are less dense then the air, so the weather balloons would rise and what gasses are not so light that they rise too much.