Newton's
1st
law
of motion (15 pts).
Given a picture of an object's motion, you should be able
to determine whether a net force is acting on the object or not.
If a net force is present, you should have some idea what
direction it must point. Here
are some examples.
Forces that determine
horizontal wind (25 pts). Pressure
gradient force (PGF), Coriolis force (CF), and frictional force
(F) (surface winds only). Rules that determine the direction and
strength of these forces. Which force can start stationary air
moving? Which of these forces will only change the direction of
the wind and not the wind speed? Which one of these forces can
only change the speed of the wind? Which of these forces is
always perpendicular to the contours on a weather map, which is
always perpendicular to the wind? Upper level and surface winds
(45 pts).Upper level
winds blow parallel to the contours, surface winds blow across
the isobars toward low pressure. You should know the
directions that upper level winds blow around circular high
and low pressure centers in the northern and southern
hemisphere. In each case you should be able to
determine the directions of the PGF and CF. Here
are lots of examples to study.
How do surface winds blow around H and
L pressure centers in the northern and southern hemispheres? Where
do you find rising and sinking air motions? Here are
several examples.
The Coriolis, pressure gradient, and frictional forces are all
shown in the figure above. Can you determine which is
which? Is this a surface or upper level, a southern or
northern hemisphere chart? Would low pressure be found at
the top, bottom, right, or left side of the figure? Once you
think you have it figured out click here.
Thermal circulations and the 3-cell model
(15 pts). Land/sea breezes.
Horizontal temperature differences create upper level and surface
pressure gradients. Given a clue of some kind (a cloud for
example) or one part of the circulation, you should be able to
determine the directions of the surface and upper level winds and
where the warm and cold parts of the picture are.
You should know the locations of the following
features: ITCZ, equatorial low, horse latitudes, NE and SE trade
winds, doldrums, prevailing westerlies, subtropical highs.
You should find each of these features in this
figure (i.e. features between about 45 S and 45 N). With
which 3-cell model features might you expect to find abundant or
infrequent rainfall?
Thunderstorms (30 pts).Ordinary single cell
(air mass) and severe thunderstorms. How might you distinguish
between an air mass and a severe thunderstorm? Life cycle
of an air mass thunderstorm (3 easy to remember stages). How can
the dissipation of one storm lead to the formation of another?
Thunderstorm features and, in some cases, processes that produce
them: gust front, anvil cloud, shelf cloud, mammatus clouds,
microburst. Wind shear. Why can a storm with a tilted updraft
become stronger and last longer than a storm with a vertical
updraft? Mesocyclone, wall clouds, and hook echoes (on radar).
Tornadoes (20 pts).Average characteristics: low pressure core, duration,
length of path on the ground, diameter, speed of rotating winds,
speed and usual direction of the movement on the ground. Tornado season (when do the most tornadoes
occur, when do the strongest tornadoes occur). Life
cycle. What causes the tornado cloud? Fujita (and the
newer Enhanced Fujita) scale. Tornado winds and damage. Multiple
vortices, suction vortices.
Lightning (25 pts).What creates the
electricity in thunderstorms? Normal distribution of electrical
charge in a thunderstorm. Types of lightning discharges,
intracloud, negative and positive cloud-to-ground lightning, and
upward lightning. Sequence of events in a multi-stroke negative
cloud-to-ground lightning flash: stepped leader, upward
connecting discharge, first return stroke, dart leader(s) and
subsequent return stroke(s). Unusual types of lightning and
rocket-triggered lightning. Lightning hazards and safety. What
produces thunder? Determining the distance to a lightning
strike. How/why do lightning rods and cars offer
protection from lightning? Fulgurites.
