PHYS/OCEA 4412/5412: Atmospheric Dynamics II

Ian Folkins, Dept. of Physics and Atmospheric Science, Ian.Folkins@dal.ca, room 131, Dunn Building, 902-494-1292

Grading:

Three quizzes (30 percent), Assignments (20 percent), and final exam (50 percent). The number to letter conversion is A+(90.0-100), A(85.0-89.9), A-(80.0-84.9), B+(75.0-79.9), B(70.0-74.9), B-(65.0-69.9), C+(62.0-64.9), C(58.0-61.9), C-(55.0-57.9), D(50.0-54.9), F(below 50.0). For graduate students, the weighting is quizzes (25 percent), assignments (15 percent), project (10 percent), and final exam (50 percent). The number to letter conversion is the same as for undergraduate students except that any mark below 70.0 is an F (see FGS calendar for implications on programme continuation).

Textbook:

Mid-Latitude Atmospheric Dynamics, Jonathan Martin

see BAMS article on occluded fronts summer 2011

Quiz Dates

Quiz 1: January 31 (class 8)

Quiz 2: March 1 (class 15)

Quiz 3: March 29 (class 23)

Formula Sheet

Previous Test Questions

Exam: 10:00 April 11 Room 221C

To Study for Quiz 3

Chapter 7: the last quiz was March 1. On March 6, we started with Figure 7.21 and QgSH (middle page 214). This is where you should start studying in the notes. I did not cover Chapter 7 after (7.30a).

Chapter 8: all

Chapter 9: up to but not including 9.5.3. However, I have skipped over most of the math. Just need to know definition of PV, and how diabatic heating affects it.

Assignment 1: due 5:00 January 12

(1) 5.11 from the text

(2) 5.12 (a) from the text. You would assume that the only factor affecting the relative vorticity is the divergence. As far as I know, the problem can't be solved exactly. Solved the problem by multiplying the divergence by f0, and by f0 plus the initial value of the vorticity. This is just linear change. Can anybody get the answer in the book?

Assignment 2: due 5:00 January 24

(1) 6.7 from the text. I think the most straightforward way to solve this question is to use (6.2b). Just go through the arguments as you would with the Northern Hemisphere. The warm equatorward side of the jet would now be toward the top of the page. Show a cross-section of the transverse vertical ageostrophic circulations you would expect at the jet entry and jet exit regions (as in the notes), and indicate whether direct or indirect.

(2) Suppose the geopotential height tendency at a particular location in the upper troposphere was positive, and a local maximum. Would you expect the isallobaric wind to be convergent or divergent? Explain.

Assignment 3: due 5:00 February 9

(1) 6.8 from the text. This is very difficult to mark. Maybe in the future ask to draw the geostrophic wind, the derivative of Vg along s, and the Q vector itself. It's mainly an exercise; difficult to know what the exact Q vector configuration should be, except in a few places. Maybe identify these more unambiguous locations and just do them.

(2) 6.9 from the text. Note that this is a somewhat unusual arrangement where the thermal wind is almost opposite to the geostrophic wind, so the geostrophic wind decreases with height from the surface.

The vorticity max would be in the center but above the low. I would argue for upward motion on the northeast side of the low, where you have strongest positive vorticity advection by the thermal wind. Downward motion on the northwest side where you have negative vorticity advection by the thermal wind.

Assignment 4: due 5:00 February 17

(1) 7.1(a) from the text

(2) 7.2 from the text (For part c should calculate F.)

Assignment 5: due 5:00 March 12

(1) 7.8 (a)

(2) 7.7(a)

(3) 7.10(a)

(4) 7.11

Assignment 6: due 5:00 March 20

(1) 8.5

(2) 8.11. In order to get the given answer you have to make several assumptions: (i) Assume that water vapor has no effect on density (i.e. use ideal gas law for dry air to get density), (ii) Assume that the winds are in geostrophic balance (obviously not a great assumption near the surface where friction is large, and near the center of a low, where the radius of curvature and centripetal acceleration are large), (iii) Assume that the pressure gradient force can be approximated as equal to the difference between the local pressure and the pressure minimum, divided by the distance from the low, (iv) Assume that the minimum pressure of the low is constant. Be very careful with signs. (a) Show a rough sketch of the buoy locations, the track of the low, the direction of the surface wind at each buoy, and the direction of the geostrophic wind at each buoy.

(b) Remember to make the correction when going from the actual wind speed to the geostrophic wind speed. Show the two densities at the two locations.