NAME: _________________________________________________ QUIZ SECTION: ____________
ATMS 101 Autumn 2008
Homework #2 (Due Wednesday, October 15)
Please show all work and write neatly in the space provided.
1. Circle the best answer for the following scenarios that refer to winds that are in geostrophic balance. a.
The winds will be (faster/ slower ) on a constant pressure map where the height contours are further apart. b.
A larger pressure gradient leads to a ( stronger /weaker) wind and a
( stronger /weaker) Coriolis force. c.
In the Southern Hemisphere, the Coriolis force acts to turn the winds to the
(right/ left ).
2. a. What two reasons did Professor Houze give in class for why upper level mid-latitude winds tend to be westerly?
1) pole-equator temperature contrast (poles are colder, so PGF points North at upper levels)
2) the rotation of the earth b.
Why are the winds westerly at upper levels in middle latitudes of both the Northern and
Southern hemispheres? (Hint: Think about your answers to 1c and 2a)
Northern hemisphere: PGF is north, therefore coriolis aims south; since coriolis is to the right of the wind, this means winds are westerly.
Southern hemisphere: PGF is south, therefore coriolis aims north; since coriolis is to the left of the wind, this means winds are westerly.
3. Pressure and Pressure Gradients a. On some random day, the height of the 500 mb surface over Moscow, Russia is 5280 meters, while over Shanghai, China it is 5520 meters. Is the pressure at a height of 5400 meters greater over Moscow or Shanghai ? b.
Based on your answer for part (a), which direction is the pressure gradient force directed
– from
Shanghai toward Moscow or from Moscow toward Shanghai? Explain why.
Pressure gradient force acts from high to low pressure. Since Shanghai has higher pressure
(at a height of 5400 m), PGF acts toward Moscow.
4. a. Which one of the following does the magnitude of the Coriolis force directly depend on? i.
Wind direction ii. Wind speed iii. Pressure gradient force iv. Friction b. What force causes the wind to blow (using the choices above)? ____ iii ______

c.
The Coriolis force is zero at the equator and increases toward the poles. When winds are in geostrophic balance, will the wind (corresponding to the same PGF) be stronger in
Florida or Maine? Explain your answer.
Since the coriolis force must balance the same PGF in both locations, it must be the same magnitude in both locations. A greater wind speed is needed in Florida than Maine to create the same coriolis force. (Remember, coriolis force magnitude increases with increased winds) .
5. a. On the figure below, draw a line along the large trough axis and label it with a “T”. Draw another line along the large ridge axis and label it with an “R”. b.
Mark a region where the winds are weak with a “W” and one where the winds are strong with an “S”. How could you predict these two regions if the winds were not labeled?
(Other locations of strong and weak winds were also accepted.)
Stronger winds are located in regions with close height contours (i.e. stronger PGF). Weaker winds are located in regions where the height contours are further apart (i.e.weaker PGF).
c.
In addition to the vectors for pressure gradient force, Coriolis force, and wind, do we need to include friction in the upper level force balance? Explain your answer.
No. Since friction comes from objects on Earth’s surface, winds at upper levels are not significantly affected by friction.