Lab Ten Introduction to General Circulation and Angular Momentum

Transcription

1 Question 1 (15 points) Lab Ten Introduction to General Circulation and Angular Momentum a.) (5 points) Examining the diagram above, between which latitudes is there net heating and between which latitudes is there net cooling? Give one reason why the poles have net cooling and one reason the equator has net warming. b.) (5 points) Given the template provided below, draw two columns with one located over the equator and one located over the pole (hint: they should not have the same height due to temperature differences implied by your answer to part a). Then draw the circulation at the upper/ lower levels and between upper/lower levels (it helps to draw the upper/ lower level "Highs" and "Lows" first). Equator Pole

2 c.) (5 points) The circulation that you just drew is the "single cell convection model" for a nonrotating earth. Compare it to the more asthetically pleasing figure below. Does it look similar to your answer for part b)? Given your knowledge about Coriolis force, in which general direction would the NH wind blow at the surface IF the diagram you drew was for a rotating Earth? Question 2 (15 points) a.) (5 points) Now you'll investigate how the above model is unrealistic. The most obvious reason that it is unrealistic is because our Earth rotates! The best way of understanding this is looking at the concept of "angular momentum." Angular momentum = mass * velocity * distance from axis of rotation (m*v*r) Angular momentum is conserved. In other words m*v*r at the equator MUST equal m*v*r at the poles. Given a parcel of constant mass, if a parcel is displaced northward away from equator, what must happen to the parcel's velocity?

3 b.) (5 points) How does your answer above relate to Coriolis force? (Hint: think of the new velocity of the parcel relative to the rotation of Earth's surface) c.) (5 points) If a parcel were actually displaced all the way from the equator to the pole it would reach unrealistic speeds (trust us on the calculation). So, the "single cell convection model" cannot be accurate for a rotating earth. Instead our Earth looks like the diagram below. How many cells (in the Northern Hemisphere) do you see? Label the cells in the diagram.

4 Question 3 (40 points) a.) (10 points) Looking at the above figure given in Question 2c) is a bit confusing initally. So let's break this up a bit. First draw a profile of the Hadley Cell in the template given below. Does this look like your "single cell convection model?" Why are the Hadley cell and the single cell convection model so similar? (hint: the Hadley cell is considered "thermally direct") Equator 30 N b.) (5 points) At the surface, due to the Coriolis force, in which direction must the wind move? Show that on your diagram above. Draw an "x" if it's "into the page" or a circle if it's "out of the page." What is the name given to these surface winds? c.) (5 points) Okay, let's go back to the concept of momentum. As you've shown above, the equator the wind is easterly (from the east). However, at the equator, Earths' surface (the ground) is rotating much faster westerly (from the west). In other words, the surface has much greater momentum than the atmosphere. So, if there is a surplus of momentum in the ground, where must the momentum move?

5 c.) (10 points) The Ferrell Cell is located poleward of the Hadley Cell. Looking at the figure given in Question 2c) draw a profile of the Ferrell Cell in the template given below. Does it look like the single cell convection model? Why do you think the Ferrell Cell is considered "thermally indirect"? 40 N 60 N d) (5 points) At the surface, due to Coriolis force, in which direction must the wind move? Show it on the diagram above. What is the name given to these surface winds? e) (5 points) Back to momentum. Recall your answer for part 2a) if a parcel is displaced away from the equator. Because the ground is now rotating slower to the west than the air above, where must the momentum move?