Simply watching clouds grow and change during any time interval brings home the idea that weather is not just limited to conditions measured at the earth's surface. To fully understand weather systems we must make measurements of various weather elements up through the atmosphere as well as over widely separated distances at the surface. Balloons carrying instruments and a radio transmitter are released twice each day (00Z and 12Z) at about 70 stations across the continental US. These instruments measure the atmospheric temperature, humidity, and pressure as the balloon ascends, until finally bursting at an altitude of about 20 kilometers or higher. The balloons are also tracked by ground based direction finding equipment to infer winds at various levels. These instruments radio their observations of the vertical patterns ("soundings") back to the launch site as they travel, hence the name radiosondes, or when tracked for winds, rawinsondes.
On the local scale, atmospheric conditions aloft may determine if the air were "unstable", resulting in vertical motions that could lead to thunderstorms or even tornadoes, or "stable", a condition that would suppress vertical cloud formation. On the larger scale, the moisture supply for major storm systems can be judged, or circulation patterns for continued fair weather or even forecasts of hurricane movements can be made. To fully know the weather now and for the near future, the total atmospheric picture must be seen. And long-range forecasts can only be attempted with knowledge of the complete three-dimensional structure of the global atmosphere.
For an explanation of how the sounding information retrieved from a radiosonde or rawinsonde is displayed on a specially prepared chart, call up the Thursday's optional Supplemental Information.
To be submitted on the lines for Thursday on the Study Guide, Part B, Applications', Week 2 Chapter Progress Response Form, under section B. Daily Summary.