Answer to Question 1
Answer: Any two of these:
- The development of basic instrumentation in the 16th-18th centuries allowed at least some of the characteristics of the atmosphere to be measured.
- The Smithsonian Institution began a network of weather observers in the middle of the 19th century and this allowed for record keeping and the ability to see a few patterns of weather.
- Invention of the telegraph at about the same time enabled rapid communication and collection of information to become centralized.
- In 1891 the U.S. Weather Bureau was established. The name changed to the National Weather Service in 1970. This allowed for an effort of national scope in the collection, analysis, and dissemination of weather information.
- World War II brought weather radar to fruition.
- In 1960 the satellite era began with TIROS-I and gave scientists a view of the planet never seen before.
- The explosion of technology continues into the 21st century.
Answer to Question 2
Answer: Elevation affects air pressure greatly so readings are corrected to sea level values. If not corrected, important meteorological variations would be masked. In short, it's a way to get every reading on the same page.