KEY to Homework Questions for Lecture 17
ES 1000
Use these questions to test your knowledge of Lecture 17 and related reading
on the atmosphere.
1. Winds flowing from high pressure to low are deflected to the right in
the Northern Hemisphere. Caution: not "East". The air is not necessarily headed north.
Think of an entire gyre. Look at your hands. Which side will it turn towards?
2. Air above a surface Low is less dense than above a surface High.
3. In the northern hemisphere, strong winds flowing from a high in the
north toward a low to the south are deflected by Coriolis to the
(choose one: left/right). Notice this is the same topic as question 1, just reworded.
4. Air in the center of a surface Low pressure area is (choose one:
rising/falling) and expanding.
5. Ninety-Nine percent (99%) of dry air is made of the gasses N2 and O2.
6. In wet air, water vapor can comprise up to 7 %. in really wet areas
such as the rainy season in the tropics.
7. The gasses CO2, CH4, NO2, and water vapor H2O also play an
important role by keeping the atmosphere warm, a process called the
greenhouse effect.
8. Temperature decreases with altitude until the Tropopause.
9. Ultraviolet radiation from the sun is absorbed by ozone in the
Stratosphere.
10. About 7 % of UV radiation reaches the Earth’s surface.
11.Water vapor is converted to liquid water during condensation. Heat is
released to the air as the vapor converts to the more-ordered liquid
form. Nearby air heats up, expands, and usually rises.
12.Condensation occurs when the air is saturated with moisture.
13.The dew point is the temperature at which air becomes saturated with
moisture.
14.Warm air overlying cooler water will warm the water.
15. Evaporation adds water molecules to the air, increasing the vapor
density, and thus the absolute humidity.
16. Fresh water freezes at 0 degrees Celsius which is 32 degrees
Fahrenheit.
17. Air above surface Low pressure is less dense than air above a surface
High. You must remember this
18. If air at ground level is saturated with moisture, a cloud we call fog
forms at [or near] the surface.
19. When two large air masses of contrasting density (temperature,
moisture content) meet, the boundary between the air masses is
termed a front.
20. At a warm front, the warm air rises above the cooler air while
displacing it.
21. At a cold front, the cold air wedges under the warmer air while
displacing it.
B. Matching.
1. Aurora e
a. opposite of condensation
2. Absolute Humidity d
b. air is saturated with moisture
3. Relative Humidity h
c. pressure difference/distance
4. Dew Point b
d. grams/m3 of water, or vapor density
5. Evaporation a
e. ionization in thermosphere
6. Ozone l
f. land heats, air rises, ocean air pulled in
7. Cold Front k
g. cloud names indicating flat, straight
8. Pressure Gradient c
h. vapor present/vapor possible at To
9. Sea breeze f
i. cloud names indicating “storm”
10.Nimbo, nimbus i
j. a cooling rate.
11. Strato, stratus g
k. wedges under displaced warm air
12. Lapse rate j
l. absorbs UV in stratosphere
C. True and False. Please CIRCLE the correct answer.
1. Water holds a lot of heat and cools very slowly. This is why currents
can transport hot tropical water to high latitudes, heating them. True
or False?
2. The Tropopause is higher near the equator than at the poles. True or
False? (If true why, if false why not?)
3. Land heats up more slowly than water. True or False?
4. The Sun’s radiation penetrates the land to 300 meters, but barely
penetrates the water. True or False?
5. Water must be constantly cycled through the atmosphere to maintain
precipitation volumes of 420 trillion m3 per year. True or False?
6. Raindrops each contain about 20 cloud droplets. True or False?
7. Latent heat is released to the atmosphere as water changes from a
less-ordered state (vapor) to a more-ordered state (liquid). This
process is called condensation. True or False?
8. Cold air holds more moisture than warm air. True or False?
9. As a mass of warm dry air rises, it expands and cools at the dry
adiabatic lapse rate. It will continue to rise through the stable air as
long as the temperature of the warm air mass remains above that of
the surrounding stable air. True or False? At each altitude, T Ask me.
10. If the temperature of rising air reaches the dew point
before it stops, it will continue to rise at the wet adiabatic rate. True
or False?
11. Cold fronts are steeper than warm fronts and cause cloud formation
and precipitation to occur across a narrower area. True or False?
12. High clouds (>6 km) have names that begin with “Cirr”, Middle
level clouds (2-6 km) have names that begin with “Alto”. True or
False?
13.
The weather forecasting significance of most cloud types greatly
depends on the direction of the wind. True or False? Check your cloud chart
14. Winds are identified with the direction they come from, not the
direction they are going to. True or False?
15. The approach and passage of a warm front is accompanied by a
definite progression of cloud types and surface winds. True or False?
16.Wind is the horizontal movement of air from areas of low to high
pressure. True or False? Backwards
17. High-pressure regions are dominated by cool or cold, descending air.
Low-pressure areas are associated with warm, rising air masses. True
or False?
18.Low-pressure systems would be rapidly dissipated by converging air
unless the inrushing air was balanced by a rising air column. True or
False?
19.Rising air above a surface Low becomes cooler and may reach
saturation, resulting in clouds and rain. True or False?
20. In the Northern Hemisphere, winds spiral clockwise toward a surface
Low, and counterclockwise away from a surface High. True or False?
Backwards
21. Cool air descends in high-pressure zones, warming as it approaches
Earth’s surface. As the air becomes warmer its relative humidity
decreases resulting in dryer air. True or False?
22. Cyclones (Lows) require divergent airflow at higher altitudes to
balance the convergent flow at the surface. True or False?
23.Above the surface, Coriolis turns the winds until they blow parallel to
the isobars. True or False?
24. Friction turns surface winds back toward the pressure gradient. True
or False?
D. Multiple Choice
1) Thunderstorms occur in the:
a) Troposphere, with overshoot into the Stratosphere.
b) Stratosphere, with overshoot into the Mesosphere.
c) Mesosphere, with overshoot into the Thermosphere.
d) All of the above.
2) Air with water vapor in it (moist air) is
a) denser (heavier) than dry air
b) less dense (lighter) than dry air
c) the same density as dry air
d) it depends on the Temperature.
E. 1. Short answers This and the next homework are the crux of this third of
the course.
Discuss rising columns of air in general. Be sure to include:
a. When water condenses, heat is released from the water to the air. What happens to
the air's density once it gets this extra heat? What about its buoyancy? Heated,
expands, so less dense. Less dense, lighter per unit volume, so more buoyant.
b. Why do clouds often form when moist air rises? The air cools, reaches saturation,
condenses to cloud droplets
c. If warmed, expanded air rises above an area of surface Low pressure, what does the
cooler, denser surrounding surface air around it do? Wedges under it
d. What are we looking at when we see a cloud, i.e. what is it made of? Tiny water
droplets. Is the water that we see in a low cloud in the gaseous (vapor), liquid, or
solid (ice) state? Usually liquid water in low and middle clouds, ice in high clouds
e. Are the gasses in a rising column of air more or less dense than surrounding air?
less dense
f. How does the temperature of the rising air compare to the surrounding air? warmer
g. Is the air above a surface Low more or less dense than surrounding surface air? less
h. Why doesn’t the surrounding air approach the Low in a straight line? Coriolis
i. In the Northern Hemisphere, does air spiral into a Low in a clockwise or counter
clockwise direction as viewed from above? counter-clockwise
j. What happens to the rising air when it hits the Tropopause? It stops, ponds, spreads out.
F. Graded questions. Turn these in.
1. For our last homework, we calculated a sample mean, an average lifespan of
x = 16.35 days in a sample of N = 290 flies. The sample standard deviation is 7.2. We
also mentioned that we can check if our data are close enough to normal with a
simple test: 1. do the center intervals spanned by  +/-  include about 70% of
the data? 2. Does each side contain similar numbers of observations? Let's try it,
estimating with the sample statistics x +/- s.
Our lower bound is 16.35 - 7.2 = 9.15. Our upper bound is 16.35 + 7.2 = 23.55
Our sample mean of 16.35 days falls in the interval 16-18 days, which includes 44
flies. The lower limb limit 9.15 days definitely includes 10-12 days (65 flies) and 1315 days (73 flies), plus a few more. The upper limb limit of 23.55 days definitely
includes 19-21 days (27 flies) and most of interval 22-24 days (15 flies). The total is
44 + 65 + 73 + 27 + 15 = 224. a. This is 224/290 x 100 = 77.2 % much greater
than 68.2% expected for two standard deviations about the mean.
Time
Interval days
Midpoint days
frequency
0-3
4-6
7-9
10-12
13-15
1618
1921
2224
2527
2830
3133
3436
3739
4042
4345
4648
49-51
2
5
8
11
14
17
20
23
26
29
32
35
38
41
44
47
50
0
2
27
65
73
44
27
15
17
5
7
2
3
0
0
0
3
Did you compare also each side? The sides do not have similar numbers of observations. The
mean is about 16, the standard deviation is about 7
Lower limb 73 + 65 = 138, upper limb 44 + 27 + about 15/2 = 78.5
b. We conclude (choose one: the data are sufficiently symmetrical for statistical tests / the data
are NOT sufficiently symmetrical for statistical tests and must be transformed)
2. A low pressure area near the surface is (choose one: denser / less dense) than an adjacent high
pressure air near the surface.
3. In the morning, an asphalt parking lot heats up quickly, then heats the air above it.
a. The heated air will (choose one: expand, becoming less dense, and will
probably rise / contract, becoming more dense, and will probably stay at the
surface)
b. If the air over the hot parking lot is 95o F, and the air over a nearby lake is
62oF, then (choose one: the cool 62oF air will push under the hot 95oF air/ the
cool 62oF air will rise over the hot 95oF air)
4. Suppose you measure a temperature of 27oC near the flagpole on the Kean University
campus. Your instructor then releases a weather balloon with a radiosonde instrument package
attached. The radiosonde reports a temperature of 21oC at the base of Cumulus clouds 1000
meters up.
What is the rate of temperature change? 6 o C / 1000 meters. This is a DRY lapse rate. WHY?