Download Mid - Atmospheric and Oceanic Sciences

•  What you should bring for exam:
2B pencil, pencil/pen, your photo ID
•  Exam Length: 50 minutes
Date and Time: Feb 13th:Monday,11:00-11:50 am
•  Location: our lecture room, Franz 1178
AOS 3 Mid-term Review
•  Exam Layout:
Winter 2012
by Yang Cao
Review Time : Feb 10th Friday
Location : Franz Hall 1178
1) around 36 Multiple-choice questions
2) around 20 Filling-blank questions
5:00 – 6:50 PM
•  Coverage:
1
From the beginning through the end of Chapter 4:
Atmospheric Pressure.
2
Atmosphere is a relatively thin layer.
Earth
Viewed from space,
it appears to hug
the ground.
3
4
Nitrogen (78.08%)
Permanent
Gases
Oxygen (20.95%)
more abundant
(Fixed Gases,
Non-variable Gases)
Most abundant
variable gas
Argon (0.93%)
……
Atmosphere
Water Vapor
Variable
Gases
Minor constitutes are also
very important.
Carbon Dioxide
Ozone
Methane
……
Greenhouse gases
(absorb Infrared
Radiation)
• Ozone also absorbs
Ultraviolet radiation
5
6
• 
being
cycled
in
Produced by
•  Ozone in the
stratosphere (97% of
the total atmospheric
ozone) : ‘Good
Ozone’
•  Stratospheric Ozone
absorbs harmful
Ultraviolet (UV)
radiation— ‘earth’s
natural Sun scream’
Removed by
7
20
-40
km
•  Ozone in the
stratosphere screens
UV radiation.
•  Human exposure to
UV increases the risk
of skin cancer.
•  If there’s less Ozone in the
stratosphere, more UV
radiation gets to the earth;
•  If there’s more Ozone in
the stratosphere, less UV
radiation gets to the earth.
9
Weight
of air
Air is compressible, water can be treated as uncompressible.
" Pressure goes down with
increasing altitude simply
because the weight of the
air above some point
decreases as we travel
upward;
" Pressure and density
decreases exponentially
(extremely quickly) with
height, due to the
compressibility of air.
11
Ozone near the surface: ‘Bad
Ozone’
(eat rubber; damage plants,
contribute to smog)
earth
8
Why Ozone Hole at South Pole?
-- South Pole is much colder than
the North Pole, and the reaction
between Chlorofluorocarbon and
Ozone needs a very cold
environment.
Ozone hole at the South Pole
A chemical released from
refrigeration and air
conditioning, manufacture of
plastic foams, solvents.
!reduction of the
stratosphere ozone
10
over Antarctica.
•  The most important
direct source of energy
for the atmosphere is
not downward-moving
solar radiation but
rather energy
emanating upward
from Earth’s surface.
• The reason is that the
atmosphere is
relatively transparent
(absorb Ultraviolet radiation)
to most types of
radiant energy emitted
by the Sun and opaque
to outgoingTerrestrial
Radiation.
(80% of the atmospheric mass)
12
*The ionosphere influences
the distance to which AM
radio waves can be
transmitted.
D, E layer（exist only daytime）: absorptive；F layer: reflective
Gas constitutes uniformly
distributed expect Ozone and
Water Vapor
•  During the day, the Dlayer absorbs the radio
waves, the D-and Elayer break up at night,
allowing the waves to
reach the F-layer.
•  The F-layer reflects the
radio waves back
towards Earth’s surface.
Lighter gases
(Hydrogen, Helium)
increase with height
Earth
•  Repeated reflections
between the F-layer and
Earth’s surface enable
the waves to be picked
up by receivers at
greater distances at
night.
13
14
15
16
17
18
Representing Weather
elements on the map
19
20
Macroscopic KE
Microscopic KE
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22
Converting Celsius to Kelvin:
Heat ~ ! Energy
(cumulative )
T ~ Energy
(average)
Converting Fahrenheit to Celsius:
Converting Celsius to Fahrenheit:
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24
Conduction (slowest)
Heat transfer:
Convection (moderate)
1)
Radiation (fastest)
25
2)
3)
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29
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• Ozone absorbs Ultraviolet radiation
•  Solar radiation is mainly shortwave radiation (visible light takes up to 50%)
• Terrestrial radiation (from the earth) is mainly longwave (Infrared radiation)
• Greenhouse gases (water vapor, carbon dioxide, ozone, methane) absorb
infrared radiation
30
E emitted= E absorbed
Intensity of
radiation
If Ta: Tb=2:1.
Then Ea:Eb=16:1.
‘Plank curve’
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32
(µm)
constant=2900
This is
shortwave
radiation!
(1 µm =10 -6 m)
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34
r
r
This is
longwave
radiation!
E ~ 1 / r2
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E received on a planet ~ 1 / r2
(r = distance away from the Sun)
depending on
( Depending on solar altitude (angle):
0~90° )
( Duration of daylight )
Solar
altitude
37
38
tilting angle
A common misunderstanding is the
seasons are determined by the distance of
the Earth from the Sun. The actual reason
is the tilt of the Earth’s axis of rotation.
Ecliptic Plane
shortest
distance
longest
distance
39
40
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Equator
Always so for
Equator
43
44
June 21
December 21
30°N
30°S
45
Solar
altitude
Solar
altitude
47
46
Inverse square law
E ~ 1 / r2
49
50
(shorter
wavelength)
(during daytime)
A higher solar
altitude (angle)
allows sunlight
to pass through
the atmosphere
with a relatively
short path.
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52
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54
(red setting sun)
At sunset
•  At sunrise or sunset, the
sunlight passes through
longer path of the
atmosphere.
•  This increase in
atmospheric length
results in a depletion of
mostly preferential
scattering light—bluish
light.
•  Blue light has been depleted
through transmitting the longer
path of atmosphere during sunset, leaving
mostly red lights reaching our eyes.
latitude dominates
Clouds dominate: more humid at the East Coast=>
more clouds=> less radiation
55
56
57
58
59
60
Net lost
SH+LH= 29 units!
Net gain
61
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63
64
* Solar radiation can be
treated as shortwave
radiation.
* Terrestrial radiation can be
treated as longwave
radiation.
* The atmosphere is almost
transparent to solar radiation
(does NOT absorb solar
radiation). But atmosphere is
a good absorber of longwave
terrestrial radiation emitting
from the earth surface .
Without Greenhouse Effect
With Greenhouse Effect
65
66
This figure shows the
balance between
incoming and
outgoing radiation
varies with latitude
on an annual basis.
The Earth is spherical, the poles receive less intense sunlight than the tropics.
This imbalance is alleviated by transport or circulation of heat poleward by the
67
atmosphere and oceans.
Slope aspect is one of the local factors affecting temperature:
•  In the north hemisphere: north-facing slopes typically receive less
intense daytime heating=> lower temperature=> retards the rate of
surface evaporation=> more water available for plants.
68
Maximum daily temp:
mid-to-late afternoon;
daily temp curve
Minimum daily temp:
just after sunrise.
Red curve: depending on
earth’s temperature
69
Effect of Cloudy condition on
Daily Temperature Range
1.Clouds can REDUCE
daily temperature range:
Reason:
1) During the day: clouds
can shade the earth
surface, reduce the
incoming solar radiation
received at the surface=>
decrease max temp;
70
Effect of Windy condition on Daily Temperature Range
2.
Reason:
Higher wind speeds promote greater forced turbulence ! the enhanced
vertical movement causes any small parcel of air immediately in
contact with the ground to be quickly displaced upward and replaced
by another parcel ! enhance air mixing!
!make the vertical temperature profile much more uniform
(homogeneous) ! reduce daily temperature ranges (shown in figures).
Calm
height
height
Windy
2) During the night: clouds
absorb the outgoing LW
radiation emitting from the
earth=> increase min
temp.
Temperature
71
Temperature
Inversion phenomenon: temperature increases 72
with
height near the ground, very common during the night.
When heated or
cooled
Measure maximum temperature
only: contain mercury, has
within a small constriction that
only allows the mercury to
move outward from the bulb.
Measure minimum temperature
only: contain dyed alcohol, has
within a small dumbbell-shape
index. Surface tension pulls the
index toward the bulb when
temperature is decreasing.73
All metal have different rates of
expansion and contraction with
temperature, one undergoes a
greater change in length than
the other.
A thermistor is a particular type
of resistance thermometer that
uses a ceramic semiconductor
instead of a metallic wire for a
filament.
74
Located 1.5 meter above the
ground
75
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78
(Fundamental
force to drive
winds)
different
associated with
Friction
80
Pressure decreases
exponentially (extremely
quickly) with height, due to the
compressibility of air.
81
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83
84
Barometric pressure is often
expressed as the height of the
column of mercury in a barometer.
Mercury is adopted because it is
extremely heavy, and allows the
instrument to be of a manageable
size.
The atmosphere
presses on the
chamber and
compresses it by an
amount proportional
to the air pressure.
Means “without
liquid”
An aneroid barometer and its working.
Isobars on weather map are usually at 4mb intervals.
1 mb (millibar=100 pascal)
85
86
500mb
height
contour map
weaker
pressure
gradient
greater
pressure
gradient
The contour
labels tell how
high you must go
upward from the
surface to find a
pressure of 500
mb.
87
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90
Arise due to the rotation of the earth
Pressure gradient force (PGF): the fundamental force to
drive winds
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This is the vertical plane:
93
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Gradient wind
This is the
horizontal
plane!
Subgeostrophic
wind
PGF
Supergeostrophic
wind
PGF
Geostrophic flow
occurs only in the
upper atmosphere
where friction is
absent and only the
Coriolis and PGF
apply.
95
96
wind
Angle between winds and
the isobars: 15~30 degree
wind
PGF
(The angle is
greater at higher
latitudes and over
smooth surfaces.)
PGF
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98
Surface Weather Map
Wind
direction
We have
friction
Converging wind around the Low at the surface
Diverging wind around the High at the surface
Cyclone
Anticyclone
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100
Difference between (anti)cyclone and Trough/Ridge
850 mb (~1.5 km)
Ridge: elongated areas around
the High Pressure
700 mb (~3 km)
Trough: elongated areas around
the Low Pressure
500 mb (~5.5 km)
101
300 mb (~9 km)
Many low- and high- pressure systems occur not as closed cells, but rather
as troughs (low p) and ridges (high p). E.g.,there is a tendency for pressure to
be distributed as cyclones and anticyclones at the surface gradually give way
102
to ridges and troughs in the upper atmosphere.
Aerovane: measure both
speed and direction
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