V1003 Science & Society
Due Oct. 13, 2010 in class
Homework #2
As with all homework assignments, the work must be your own.
1. Seasons
a. why are there seasons?
Because the Earth is tilted (23.5° relative to the ecliptic)
b. How would seasons be different if the Earth orbital tilt increased from 23.5° to , say,
45°?
Summers would be warmer and longer, and the winters would be colder and shorter.
Stronger seasonality.
c. How would the northern and southern hemisphere seasons differ if the Earth was a
rotating cylinder instead of a sphere (with the same axial tilt as today)?
All latitudes would have the same seasonality as at the equator, because in effect the
cylinder planet is a “tube” of “equators”. There would be no change with seasonality with
latitude as we have today. The main seasonality would arise from the minor earth-sun
distance changes of the orbit.
2. Coriolis Effect
a. In your own words, describe what the Coriolis effect is.
An apparent force that results from conservation of angular momentum (answer must
have something like this in it).
b. If the Earth rotated very slowly (say 1/10th of its present rate) discuss how you think the
northern subtropical trade winds would be altered in their sped and direction. Sketch
what they look like today, and then what they’d look like under this different scenario.
If the Earth rotated very slowly the Coriolis force would be very weak and so the winds
would be more parallel to the direct pressure gradient force (instead of being deflected to
the right in the NH). So, the northern (southern) trade winds would blow more directly to
the south (to the north) instead of the east.
c. This is a pressure map of Australia. The lines are isobars with the pressure values labeled
(in millibars). Sketch the surface winds for positions A, B C, and D.
C
A
B
D
A. from the S to SE
B. from the N to NE
C. from the E
D. from the W
3. General Atmospheric Circulation
a. In your own words, identify the two main factors that cause the atmosphere to circulate?
(2 sentences or less)
Earth rotation and uneven solar heating
b. Heating and water vapor drive the Hadley circulation, how? (2 sentences or less)?
Solar heating heats the air makes it lower pressure, less dense. (hot air can also hold more
water vapor through the C-C equation).
As air ascends, water vapor condenses releasing latent heat of condensation and this makes
the air warm up and rise more.
Thermally-direct cell.
c. Discuss how general atmospheric circulation is responsible for the following:
i. Location of rainforests (under the ascending limbs of Hadley, ITCZ)
ii. Location of deserts (under the descending limbs of Hadley, dry air)
iii. The seasonal north-south migration of the ITCZ (near equatorial band of
maximum solar heating changes with seasons, in NH is boreal summer, SH in
boreal winter. Also, they could mention monsoons which draw the ITCZ off the
equator)
iv. The Asian Monsoon rains in India/China (summer season solar radiation max
heats up the land more than the ocean due to lower thermal interia of land. This
establishes a large ‘sea breeze’ bringing moist maritime air into S. Asia and
China. Air ascends mountains and rains out – monsoon rain)
d. Why is this figure below important? (2-3 sentences)
Shows the LOCAL imbalances between incoming (shortwave) solar radiation and outgoing
(lonwave) radiation. Globally in = out, locally there are imbalances due to atmosphere and
ocean heat transport. (should have all this in there).
e. Sketch how you think would this figure look if the Earth rotated only very slowly (say
1/10th its rotational rate today) but had its same axial tilt and orbital path around the sun.
Discuss.
The red line would look like the blue line because weak rotation = weak coriolis – weak atm
and ocean heat transport.