Your goal is to take off from the Salt Lake Valley (850 mb) and fly above the crest of the Wasatch (650 mb). The conditions are artificial so that you can visualize the situation a bit easier than the circumstances most paragliders would encounter.
1. Use the blank SkewT distributed in class. The current temperature at the surface (850 mb) is 20C. The temperature at crest level (650 mb) is 2C. Assume that the environment in between these levels varies linearly with log pressure. Draw carefully the environmental temperature profile from 850 to 650 mb.
- a. If a parcel of air was lifted from the surface up 50 mb, would it find itself (heavier/lighter), (warmer/colder) than the environment? Why?
- b. Is the environment stable, neutral, or unstable? Why?
2. You have the choice to lift off from the following surfaces in the Valley. All have the same exposure to solar radiation and wind patterns. Explain what might be the optimal surface(s) and which aren't. Use basic physical reasoning and concepts related to the surface energy budget for your explanations.
- a. A platform in the middle of a small lake.
- b. salt flat
- c. wet grass
- d. dry grass
- e. bare rock
- f. plowed field
3. You've found a thermal such that combined with your superduper paraglider you have a total buoyant force relative to the environment at the surface equivalent to a temperature excess of 1C.
- a. What is your initial temperature at 850 mb? Assuming that your paraglider in the thermal ascends dry adiabatically, at what pressure do you become neutrally buoyant? Show on the skewT and explain your reasoning.
- b. On the skewT diagram, the area between a parcel's (in your case the paraglider) path and the environment is proportional to the buoyancy excess or deficit. At what pressure will you stop ascending based on your loss of buoyancy above the level of neutral buoyancy? Show on the skewT and explain your reasoning.
- c. You madly scramble around when you are no longer ascending and find another thermal with a temperature excess of 1C. How high will you reach with this second thermal? How many thermals of this sort do you need before you reach 650 mb?
4. Discuss very briefly why this situation is artificial. What would have made it more realistic?