Earth Science: Geology, the Environment, and the Universe

Chapter 12: Meteorology

Problem of the Week

Flight Height and the Jet Stream

If you have ever witnessed the flight of a hot air balloon, you know that it is an amazingly beautiful sight as it silently floats through the air. The only sound is from an occasional burst of the burners as a flame is lit to keep the air inside the balloon warm. As you learned in the last chapter, the top of the troposphere occurs roughly at 10 km. At these same altitudes, we find one of the most dynamic and influential wind systems on Earth—the jet streams. These wind systems are extensively studied by balloonists seeking to use them to their advantage in attempts at making trips around the world, and record setting balloon voyages.

As an amateur balloonist, for this problem, you need to take a crash course in "Jet Steam 101."

• blow from west to east around the world
  
  
• are a few hundred feet wide and often less than three feet thick
  
  
• reach average speeds of 120 mph
  
  
• usually stronger in the winter
  
  
• their changing nature can make them a "wild ride" rather than bringing smooth sailing
  
  
• jet streams are affected by surface conditions such that they sometimes take a sharp northerly route and then bend back toward the south in what are called ridges and troughs
  
  
• their altitude may change in varying degrees
  
  
• near the poles, they are generally found at lower altitudes (8 km)
  
  
• near the equator they can be found at higher latitudes, about 16 km
  
  
• the transition between altitudes is not always smooth, but can be abrupt
  
  

Problem:

Imagine that you are a balloonist in the planning stages of attempting a record setting, trans-USA balloon flight. You know that the jet stream is going to be the key to your success. Armed with a top of the line balloon that will get you to the altitudes that are required, basic knowledge of the jet streams given above, and a map of the jet steam on the day you are going to make your trip, plot a course for your trip.

Use the map at bottom of this Web page
http://ww2010.atmos.uiuc.edu/(Gh)/
guides/mtr/cyc/upa/jet.rxml

*Notice the wind speed key at the bottom of the map. Also notice that there are "two" jet streams over the U. S.

These are some of the things you will want to consider when planning the route:

• From what point will you launch (what city)?
  
  
• At what general speed will you travel?
  
  
• At what general altitude?
  
  
• Will you have to beware of any ridges or troughs in the jet stream that may take you out of the way, and lengthen your journey? Can they be avoided?
  
  
• What time of year will your flight take place?
  
  
• Where is your approximate landing point (what city)?