Homework for Chapter 9 - The Atmosphere in Motion: Air Pressure, Forces, and Winds
Questions 1 and 2 will be turned in for a grade. Questions 3-9 will be discussed by the discussion groups in class so please look them over before the discussion session.
SHOW ALL WORK , CIRCLE THE CORRECT ANSWER, PLEASE BE NEAT AND STAPLE YOUR HOMEWORK!
ALSO, PLEASE USE A SPREADSHEET FOR ALL GRAPHS
Follow the Problem solving steps discussed in class
1. On a given day, you observed that the wind is 75 kts here at LSC at 500 mb. Further, you also observe that the isobars are straight and that the flow is from west to east.
a. Assuming that the flow is geostrophic, what is the magnitude of the pressure gradient force producing the observed wind?
b. What are the directions of the pressure gradient and coriolis forces necessary to produce the observed flow?
c. If the flow on a given day at Montevideo, Uruguay is 75 kts at 500 mb, draw a diagram showing the direction of the pressure gradient and coriolis forces and the resultant wind direction assuming that the flow is geostrophic.
2. The flow within a tornado is due to the combination of the pressure gradient and centrifugal forces. In other words, for a tornado
pressure gradient force + centrifugal force = 0
Given wind speeds of 100 m/s within a tornado that is 500 meters in diameter, what is the pressure change from outside to the center of the tornado? You can assume that the air density is 1 kg m-3.
3. Given a 40 knot geostrophic northwesterly wind at 500 mb, draw a diagram showing the orientation of the height lines necessary to create this wind. Also draw in the directions and relative magnitudes of all forces acting on this air parcel.
4. Now consider a 20 knot southeasterly wind at the surface. Draw a diagram illustrating the orientation of the isobars necessary to create this wind and also draw in the direction and relative magnitudes of all forces acting on this parcel of air.
5. Why is it impossible for a hurricane to cross the equator?
6. Pilots often use the expression "high to low, look out below." In terms of upper-level temperature and pressure, explain what this can mean?
7. If the earth were not rotating, how would the wind blow with respect to centers of high and low pressure?
8. Why are surface winds that blow over the ocean closer to being geostophic than those that blow over the land?
9. In the southern hemisphere, in what direction do the upper-level winds move? Demonstrate your answer with the aid of a diagram by indicating the directions of the relevant forces involved.
10. With your present outside surface wind, determine where regions of surface high- and low- pressure areas are located. If clouds are moving overhead, locate the locations of high- and low- pressure aloft.
11. If you live in the Northern Hemisphere and a region of surface low pressure is directly west of you, what would probably be the surface wind direction at your home? If an upper-level low is also directly west of your location, describe the probable wind direction aloft and the direction in which middle-type clouds would move. How would the wind direction and speed change from the surface to where the middle clouds are located?
12. Consider wind blowing over a land surface that crosses a coastline and then blows over a lake. How will the wind speed and direction change as it moves from the land surface to the lake surface?
13. With the aid of a diagram, explain why winds flow counterclockwise around low pressure and clockwise around high pressure in the northern hemisphere. Indicate all relevant forces on your diagram. How does the flow direction around highs and lows change when in the southern hemisphere?
EXTRA CREDIT: With the aid of a diagram and using the concepts discussed in this chapter, explain why the jet stream is located over a frontal boundary.