ATMO 336
Climate, Weather and Society
Lecture
Atmospheric Composition
Temperature, Density, Pressure
Vertical Structure
Weather vs. Climate
Atmospheric Composition
Permanent Gases
Ahrens, Table 1.1, 3rd Ed.
• N2 and O2 are most
abundant gases
• Percentages hold
constant up to 80 km
• Ar, Ne, He, and Xe
are chemically inert
• N2 and O2 are
chemically active,
removed & returned
N2 and O2
N2
Boiling point: 77 K or -196°C or –320 °F
O2
Boiling point: 90 K or -183 °C or -297 °F
Balance between input (production) and output (destruction):
Input: plant/animal decaying
Input: plant photosynthesis
Sink: soil bacteria;
Sink: organic matter decay
oceanic plankton-->nutrients
chemical combination (oxidation)
breathing
Atmospheric Composition
Important Trace Gases
Ahrens, Table 1.1, 3rd ed.
Which of these is now wrong even in the 4th edition of Ahrens?
Carbon Dioxide CO2
Sources
vegetative decay
volcanic eruptions
animal exhalation
combustion of fossil fuels
(CH4 + 2 O2 > 2 H2O + CO2)
Sinks
photosynthesis (oxygen production)
dissolves in water
phytoplankton absorption (limestone formation)
CO2 Trend
“Keeling Curve”
Some gases vary by season and
over many years.
The CO2 trend is the cause for
concern about global warming.
CO2 increases
in northern spring,
decreases in northern fall
http://earthguide.ucsd.edu/globalchange/keeling_curve/01.html
H2O Vapor Variability
Precipitable Water (mm)
Some gases can vary
spatially and daily
Aerosols
1 cm3 of air can contain as many as 200,000
non-gaseous particles.
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dust
dirt (soil)
salt from ocean spray
volcanic ash
water
pollen
pollutants
Aerosols - Volcanic Ash
Fig. 1-4, p.6
Aerosols - Dust Particles
Dust Storm on Interstate 10, between Phoenix and Tucson, AZ.
Aerosols
• Provide surfaces upon which water vapor
can condense.
• Provide a surface area or catalyst needed for
much atmospheric chemistry.
• Aerosols can deplete stratospheric ozone.
They can also cool the planet by reflecting
sunlight back to space.
Scientific Notation
How do we write very big or very
small number?
Scientific Notation is the way that
scientists compactly write very large
or small numbers
It can be thought of as a coefficient
times ten raised to an exponent
Scientific Notation
Speed of light is 300,000 meters per second
(m s-1)
Scientific Notation for speed of light is
3.0 x 105 m s-1
Wavelength of visible light is close to
0.0000005 meters
Scientific Notation for wavelength would be
5.0 x 10-7 m s-1
Scientific Notation
Example…
Distance between the Earth and the Sun is
150,000,000 kilometers
Scientific Notation for distance would be?
Scientific Notation
Example…
Distance between the Earth and the Sun is
150,000,000 kilometers
Scientific Notation for distance would be?
1.5 x 108 km
Fundamental Concepts
Let us introduce three fundamental
concepts...
Temperature
Density
Pressure
Temperature Scales
• Fahrenheit (oF) - relative
US public standard
• Celsius (oC) - relative
Freezing point 0oC
Boiling point 100oC
o
C= 5/9 (oF-32)
• Kelvin (K) - absolute
K= oC+273
Ahrens p27
What is Temperature?
Microscopic View
Energy due to random
jiggling of molecules
Related to average
molecular speed (v);
500 m/s for air
at room temperature
Maxwell Distribution
K.E.=(1/2)mv2=(3/2)kT
m = mass of one molecule
k = Boltzmann constant
=1.38065×10−23 joule/K
(joule is unit of energy)
Impact of Extreme Temperatures
on Humans
Hypothermia
Hyperthermia
Condition in which the
internal temperature
drops below that
required for normal
metabolism and bodily
functions.
Condition in which the
internal temperature
rises above threshold
that leads to organ
failure.
Hypothermia Stages
• Stage 1 http://en.wikipedia.org/wiki/Hypothermia
– Body temperature drops by 1-2C
(Normal body temperature is 37 C)
– Mild to strong shivering occurs
– Hands become numb, can’t do complex tasks
– Blood vessels in outer extremities constrict
– Breathing becomes quick and shallow
– Goose bumps appear
Hypothermia Stages
• Stage 2 http://en.wikipedia.org/wiki/Hypothermia
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Body temperature drops to 2-4C below normal
Shivering becomes more violent
Lack of coordination apparent, e.g. stumbling
Mild confusion
Surface blood vessels contract further
Skin pallor becomes pale
Lips, ears, fingers and toes can turn blue
Hypothermia Stages
• Stage 3 http://en.wikipedia.org/wiki/Hypothermia
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Body temp. drops below 32C (90F)
Shivering usually stops
Difficulty speaking, slow thinking, amnesia
Inability to use hands and stumbling
Cellular metabolic processes shut down
Hypothermia Stages
• Stage 3 (cont’d)
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Body temp. drops below 30C (86F)
Walking nearly impossible
Incoherent or irrational behavior, even stupor
Pulse and respiration rates slow significantly
Heart arrhythmia; tachycardia, atrial fibrillation
Major organ failure. Clinical death occurs.
Decreased metabolism delays brain death
http://www.weather.gov/os/windchill/index.shtml
Hypothermia Prevention
www.mayoclinic.com
COLD - Cover, Overexertion, Layers, Dry
• Cover. Wear a hat to prevent body heat from escaping from
your head, face and neck. Cover your hands with mittens
instead of gloves.
• Overexertion. Avoid activities that would cause you to
sweat a lot.
• Layers. Wear loose-fitting, layered, lightweight clothing.
Outer clothing made of tightly woven, water-repellent
material is best for wind protection. Wool, silk or
polypropylene inner layers hold more body heat than
cotton does.
• Dry. Stay as dry as possible.
Hyperthermia
• Stages http://en.wikipedia.org/wiki/Hyperthermia
– Temperatures above 40°C (104°F) are lifethreatening
– 41°C (106 °F) brain death begins
– 45°C (113°F) death is nearly certain
– Core temperatures above 50°C (122°F) cause
muscle rigidity and certain, immediate death
Hyperthermia
• Stages http://en.wikipedia.org/wiki/Hyperthermia
– In its advanced stage, hyperthermia is called
heat stroke or sun stroke
– Heat stroke is a medical emergency that
requires hospitalization
– Heat stroke can come on suddenly, but it
usually follows the less-threatening condition
of heat exhaustion or heat prostration, which in
turn is often follows heat cramps
Heat Cramps
www.mayoclinic.com/health/first-aid-heat-cramps
– Mild form of heat exhaustion
– Cramps in the calves, arms, abdomen and back,
occurrence is common in athletes
– Inadequate intake of fluids or electrolytes is
very often a contributing factor
– Treatment: rest and cool down; drink clear juice
or electrolyte drink; stretch muscle group
Heat Exhaustion Symptoms
www.mayoclinic.com/health/first-aid-heat-exhaustion
Feeling faint or dizzy
Nausea
Heavy sweating
Rapid, weak heartbeat
Low blood pressure
Cool, moist, pale skin
Low-grade fever
Heat cramps
Headache
Fatigue
Dark-colored urine
Heat Exhaustion Treatment
www.mayoclinic.com
– Get the person out of the sun and into a shady
or air-conditioned location.
– Lay the person down, elevate the legs and feet
slightly.
– Loosen or remove the person's clothing.
– Have the person drink cool water.
Heat Exhaustion Treatment
www.mayoclinic.com
– Cool the person by spraying or sponging them
with cool water and fanning.
– Monitor the person carefully. Heat exhaustion
can quickly become heatstroke.
– If fever greater than 102 F (38.9 C), fainting,
confusion or seizures occur, dial 911 or call for
emergency medical assistance.
Heat Stroke Symptoms
www.mayoclinic.com
• High body temperature of 104F (40C) or higher
is the main sign of heat stroke.
• Cessation of sweating. In heatstroke brought on by
hot weather, your skin is hot and dry to the touch.
In heatstroke brought on by strenuous exercise,
your skin usually feels moist.
• Hyperventilation, rapid and shallow breathing.
Heat Stroke Symptoms
www.mayoclinic.com
• Rapid heart rate and pulse (tachycardia). Your
blood pressure usually remains normal, but your
pulse may increase to around 130 beats a minute,
well above the normal level for adults (60 to 100).
• Neurological symptoms. You may have seizures,
lose consciousness, slip into a coma, hallucinate,
or have difficulty speaking or understanding what
others are saying.
• Muscle cramps or weakness. Your muscles may
feel tender or cramped in the early stages of
heatstroke, but may later go rigid or limp.
Heat Stroke Treatment
www.mayoclinic.com
MEDICAL EMERGENCY!
Doctor/hospital may administer…
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Cold water immersion. (Currently out of favor.)
Evaporative cooling techniques.
Ice packs and cooling blankets.
Internal “flushing” techniques.
• Medications to stop treatment-caused shivering.
Heat Index
http://www.weather.gov/os/heat/index.shtml
Heat Injury Prevention
www.mayoclinic.com
• Wear loose-fitting, lightweight clothing.
• Seek a cooler environment. A good way to start
cooling off is to get to a cooler environment, like
an air-conditioned building or a shady spot.
• Drink plenty of fluids. Staying hydrated helps
your body sweat and maintain a normal body
temperature. Avoid diuretics (alcohol, caffeine).
• Take extra precautions with certain medications.
Apparent Temperature
Current U.S. Apparent Temperature Map
What is Density?
Density (d) = Mass (M) per unit Volume (V)
d = M/V
Typical Units: kg/m3, gm/cm3
Mass =
# molecules  molecular weight (gm/mole)
Avogadro number (6.023x1023 molecules/mole)
Density Change
Density (d) changes by altering either
a) # molecules in a constant volume
b) volume occupied by the same # molecules
a
b
What is Pressure?
Pressure (p) = Force (F) per unit Area (A)
Typical Units: pounds per square inch (psi),
millibars (mb), inches Hg
Average pressure at sea-level:
14.7 psi
1013 mb
29.92 in. Hg
Pressure
Can be thought of as weight of air above you.
(Note that pressure acts in all directions!)
So as elevation increases, pressure decreases.
Top
Bottom
Higher elevation
Less air above
Lower pressure
Lower elevation
More air above
Higher pressure
Density and Pressure Variation
Key Points
1. Both decrease
rapidly with height
2. Air is compressible,
i.e. its density varies
Ahrens, Fig. 1.5
Why rapid change with height?
Consider a spring with 10 kg bricks on top of it
The spring compresses a little more with each
addition of a brick. The spring is compressible.
10 kg
10 kg
10 kg
10 kg
10 kg
10 kg
Why rapid change with height?
Now consider several 10 kg
springs piled on top of
each other.
Topmost spring compresses
the least!
Bottom spring compresses
the most!
The total mass above you
decreases rapidly w/height.
 mass
 mass
 mass
 mass
Why rapid change with height?
Finally, consider piled-up
parcels of air, each with
the same # molecules.
The bottom parcel is
squished the most.
Its density is the highest.
Density decreases most
rapidly at bottom.
Why rapid change with height?
Each parcel has the same
mass (i.e. same number
of molecules), so the
height of a parcel
represents the same
change in pressure p.
Thus, pressure must
decrease most rapidly
near the bottom.
p
p
p
p
Water versus Air
Pressure variation in water acts more like bricks,
close to incompressible, instead of like springs.
Top
Bottom
Air:
Lower density,
Gradual drop
Higher density
Rapid decrease
Top
Water:
Constant drop
Constant drop
Bottom
A Thinning
Atmosphere
Top
Lower density,
Gradual drop
w/elevation
Higher density,
Bottom Rapid decrease
w/elevation
NASA photo gallery
Pressure Decreases Exponentially
with Height
1 mb
10 mb
48 km
32 km
100 mb 16 km
Ahrens, Fig. 1.5
Logarithmic Decrease
• For each 16 km
increase in altitude,
pressure drops
by factor of 10.
48 km - 1 mb
32 km - 10 mb
16 km - 100 mb
0 km - 1000 mb
Equation for Pressure Variation
We can Quantify Pressure Change with Height
p (at elevation zin km)  pMSL  10 Z /(16 km)
where
z is elevation in kilometers (km)
p is pressure in millibars (mb)
at elevation z in meters (km)
pMSL is pressure (mb) at mean sea level
What is Pressure at 2.8 km?
(Summit of Mt. Lemmon)
Use Equation for Pressure Change
 Z /(16 km)
p(at elevation Zin km)  pMSL 10
set Z = 2.8 km, pMSL  1013 mb
p(2.8 km)  1013mb 10 (2.8 km) /(16 km)
p(2.8 km)  1013mb 10
0.175
p(2.8 km)  1013mb  0.668  677 mb
What is Pressure at Tucson?
Use Equation for Pressure Change
p(at elevation Zin km)  pMSL 10 Z /(16 km)
set Z = 800 m, pMSL  1013 mb
Let’s get cocky…
How about Denver? Z=1,600 m
How about Mt. Everest? Z=8,700 m
You try these examples at home for practice
Impact of Density and Pressure
Changes on Humans
Altitude sickness or hypoxia.
Hypoxia means "deficient in oxygen."
Hypoxemia means "deficient oxygen in blood.”
Altitude sickness is caused by the decrease of
oxygen with increasing elevation.
Altitude Sickness Symptoms
• Headache is a primary symptom used to
diagnose altitude sickness, although
headache is also a symptom of dehydration.
A headache occurring at an altitude above
2,400 meters (8000 feet = 760 mb),
combined with any one or more of the
following symptoms, could be an indication
of altitude sickness.
Altitude Sickness Symptoms
en.wikipedia.org/wiki/Altitude_sickness
Sign on Mt. Evans CO
No appetite, nausea or vomiting
Fatigue or weakness
Dizziness or light-headedness
Insomnia
Pins and needles
Shortness of breath upon exertion
Persistent rapid pulse
Drowsiness
General malaise
Peripheral edema (swelling hands,
feet, and face)
Life-threatening Conditions
en.wikipedia.org/wiki/Altitude_sickness
Symptoms of extreme altitude sickness include:
• High altitude pulmonary edema (fluid in lungs)
– dry cough; may progress to pink, frothy sputum
– fever
– shortness of breath even when resting
• High altitude cerebral edema (swelling of brain)
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headache that does not respond to analgesics
unsteady walking
increasing vomiting
gradual loss of consciousness
Critical Altitude Conditions
en.wikipedia.org/wiki/Altitude_sickness
• HAPE occurs in ~2% of those who are
adjusting to altitudes of ~3000 m (10,000
feet = 700 mb) or higher.
• It can progress rapidly and is often fatal.
• Descent to lower altitudes alleviates the
symptoms of HAPE.
Critical Altitude Conditions
en.wikipedia.org/wiki/Altitude_sickness
• HACE occurs in 1% of people who are
adjusting to altitudes of ~2700 m (9,000 feet
= 730 mb) or higher.
• It can lead to coma or death.
• Descent to lower altitudes may save those
afflicted with HACE.
Prevention of Altitude Sickness
en.wikipedia.org/wiki/Altitude_sickness
• Oxygen enrichment or BYOB of O2!
• Altitude acclimatization
– Gradual adjustment to decreasing oxygen level
with increasing altitude, which allows for the
production of additional red blood cells
– Some drugs can accelerate the adjustment
• Humans can adjust to elevations up to
6000 meters (~20,000 feet = 470 mb).
Nepal
en.wikipedia.org/wiki/Nepal
Temperature (T) Profile
inversion
isothermal
6.5oC/km
Ahrens, Fig. 1.7
• More complex than
pressure or density
• Layers based on the
Environmental Lapse
Rate (ELR), the rate
at which temperature
decreases with height.
Higher Atmosphere
Molecular Composition
• Homosphere- gases
are well mixed.
Below 80 km.
Emphasis of Course.
• Heterosphere- gases
separate by molecular
weight, with heaviest
near bottom. Lighter
gases (H, He) escape.
Ahrens, Fig. 1.8
Atmospheric Layers Essentials
• Thermosphere-above 85 km
Temps warm w/height
Gases settle by molecular weight (Heterosphere)
• Mesosphere-50 to 85 km
Temps cool w/height
• Stratosphere-10 to 50 km
Temps warm w/height, very dry
• Troposphere-0 to 10 km (to the nearest 5 km)
Temps cool with height
Contains “all” H2O vapor, weather of public interest
Take Home Points
• Many gases make up air
N2 and O2 account for ~99%
Trace gases: CO2, H2O, O3, etc.
Can be very important…more later
• Pressure and Density Profiles
Decrease rapidly with height
• Temperature Profile
Complex vertical structure
Climate and Weather
“Climate is what you expect.
Weather is what you get.”
-Robert A. Heinlein
Weather
Weather – The state of
the atmosphere:
for a specific place
at a particular time
Weather Elements
1) Temperature
2) Pressure
3) Humidity
4) Wind
5) Visibility
6) Clouds
7) Significant Weather
Surface Station Model
Responsible for boxed parameters
Ahrens, p 431
Temperatures
Plotted F in U.S.
Sea Level Pressure
Leading 10 or 9 is
not plotted
Examples:
1013.8 plotted as 138
998.7 plotted as 987
1036.0 plotted as 360
Sky Cover and Weather Symbols
Ahrens, p 431
Ahrens, p 431
Wind Barbs
Direction
Wind is going towards
65 kts from west
Westerly  from the West
Speed (accumulated)
Each flag is 50 knots
Each full barb is 10 knots
Each half barb is 5 knots
Ahrens, p 432
SLP pressure
temperature
dew point
Ohio State website
cloud cover
wind
Practice Surface Station
72
58
111
Decimal point
What are Temp, Dew Point,
SLP, Cloud Cover, Wind
Speed and Direction?
Ahrens, p 431
Temperate (oF)
Pressure (mb)
Last Three Digits
(tens, ones, tenths)
Dew Point (later)
Moisture
Wind Barb
Direction and Speed
Cloud Cover
Tenths total coverage
Practice Surface Station
42
18
998
Decimal point
What are Temp, Dew Point,
SLP, Cloud Cover, Wind
Speed and Direction?
Ahrens, p 431
Sea Level Pressure
Leading 10 or 9 is
not plotted
Examples:
1013.8 plotted as 138
998.7 plotted as 987
1036.0 plotted as 360
Surface Map Symbols
• Fronts
Mark the boundary
between different
air masses…later
Significant weather
occurs near fronts
Current US Map
Ahrens, p 432
Radiosonde
Ahrens, Fig. 1
Weather balloons, or
radiosondes, sample
atmospheric to 10 mb.
They measure
temperature
moisture
pressure
They are tracked to get
winds
Radiosonde Distribution
Radiosondes released
at 0000 and at 1200
GMT for a global
network of stations.
Large gaps in network
over oceans and in
less affluent nations.
Stations ~400 km apart
over North America