Name:____________________________
SO441 Synoptic Meteorology: Homework 4
50 points
1. (5 pts) Define the vorticity vector, both mathematically and physically.
2. (5 pts) What is relative vorticity? What is Earth’s vorticity? What is absolute vorticity?
g 2
 z , why upper-level troughs in the northern
f
hemisphere are associated with positive relative vorticity and why ridges in the northern
hemisphere are associated with negative relative vorticity.
3. (5 pts) Explain, using the equation  g 
4. (5 pts) Why does the sign of the vorticity  g 
g 2
 z change for troughs and ridges the
f
southern hemisphere?
5. (10 pts) Calculate the relative vorticity at the following two center points. Show all work.
Each wind barb is 50 nm from the center point. Winds are given in kts. In the left plot, winds are exactly from the
east, north, west, and south, but in the right plot, winds are exactly from the SW, SE, NE, and NW (so use
trigonometry to find u and v components).
6. (5 pts) In the above problem, if the left panel corresponded to the flow inside a hurricane at
15°N, and the right panel with an extratropical cyclone at 65°N, calculate the absolute vorticity
for each.
7. (5 pts) Define “potential vorticity”, both mathematically and physically.
8. (10 pts) Using the concept of potential vorticity, explain how a surface low would develop in
western Argentina under zonal flow aloft. (Use a topographic map in case you’re unfamiliar with
the geography of South America).