Each of the multiple choice questions was worth 2 points. There were 42
questions, which means that there were 84 points possible for this section. You
were required to do 5 out of the 8 short answer questions. Each was worth 7
points, for 35 possible points. Thus, the total number of points possible was
119.
To figure out your grade, add up the total number of points in both the
multiple choice and short answer section, divide by 1.19 (or divide by 119 and
multiply by 100), and then add 17.5. Because the grades were lower than
expected, a "curve" was developed to raise everyones grade by 17.5%.
3 points - A diagram with correct wind arrows. It is useful, but not
required, to draw the pressure gradient force, Coriolis force, and frictional
force. A diagram with the wrong wind arrows and no force arrows received no
partial credit.
2 points - This wind pattern results in divergence since the wind arrows are
pointing away from the high pressure.
1 points - The divergence implies that there is sinking air.
1 points - And therefore, there are clear skies.
3 points - Latent heat means energy associated with changing the phase of
water between gas, liquid and ice.
2 points - Energy is added to or removed to a substance to change its phase but
its temperature doesn't change.
2 points - In moist convection, water from the surface rises until the water
condenses. Latent heat energy is put into the air at the surface by
evaporation, and it is released in the mid-troposphere via condensation which yields
warmer mid-troposphere air temperatures.
2 points - There is a lower air pressure at higher altitude.
2 points - A lower air pressure means there will be a lower saturation vapor
pressure at boling point of water.
2 points - A lower saturation vapor pressure at the boiling point implies that
the boiling temperature of water will be lower.
1 points - A pressure cooker increases pressure to increase the boiling
temperature. This shortens cooking time and kill things that need to be killed
in cooking.
Correct values of Us, U, Us-U
1.5 points - City A: 31.16 -15.58 = 15.58
1.5 points - City B: 15.95 - 4.79 = 11.16
1.5 points - City C: 7.74 - 0.77 = 6.97
2.5 points - City A, with a temperature of 90F and 50% RH, is the largest Us-U
which represents the largest depletion or difference between in the amount of
water that air can "hold" versus the amount of water actually in the
air.
1 point - Body sweats and puts liquid water on the surface of the skin.
1.5 points - Liquid water evaporates into thin boundary layer of air next to
skin.
1.5 points - This evaporation (conversion of water from liquid to vapor) and
transfer of latent heat cools the skin.
1 point - Without wind, the boundary layer becomes saturated (high RH) and
reduces the rate of evaporation of sweat.
1 point - Breeze removes saturated layer and replaces it with a layer of lower
RH air.
1 point - Sweat evaporates more quickly into the new, lower RH air layer which
rapidly cools skin.
3 points - Correct force diagram of PGF, Coriolis and wind direction.
1 point - Air is accelerated or pushed from high pressure to low pressure.
1 point - Air is also accelerated (rotated or pushed) to the right by Coriolis
"force".
1 point - Geostrophic force balance: PGF + Coriolis ~ 0.
1 point - Direction of rotation: counterclockwise for low pressure storm in
Northern Hemisphere.
2 points - First, cool beer in refrigerator to some temperature measured
with the thermometer. Remove can to outside air.
2 points - If condensation forms then the dewpoint temperature of the outside
air is greater than the temperature of the can. Otherwise, the can is warmer
than the dewpoint temperature.
3 points - Now cool or warm refrigerator temperature and repeat above until the
dewpoint temperature outside the refigerator is exactly equal to the
temperature of the can. This step is important. If you just do the measurement
once, you have provided only an upper or lower bound to the dewpoint
temperature.
1 point - One thermometer measures the temperature of the air.
1 point - The other (wet one) measures the wet bulb temperature, which is
approximately the dewpoint temperature.
1.5 points - The sling motion causes enhanced evaporative cooling because of
the air molecules moving past the wet thermometer.
1.5 points - Read the wetbulb (or dewpoint) temperature and the air temperature
to get relative humidity from a table such as the one provided on the exam.
2 points - Estimate dewpoint temperature: Us(70F)=15.95 g/kg, 50% RH => U~8
g/kg => Td ~ 51F
2 points - In a cold core low, 500mb height in core will be low, height in
outer region high.
2 points - In a warm core low, 500mb height in core will be higher when
compared to a cold core low.
1.5 points - Thus, there is a higher pressure gradient aloft in cold core low.
1.5 points - Meaning there will be stronger winds aloft in a cold core low.