ATMO 336Climate, Weather and Society

LectureAtmospheric Composition

Temperature, Density, PressureVertical Structure

Weather vs. Climate

Atmospheric CompositionPermanent Gases

• 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

Ahrens, Table 1.1, 3rd Ed.

N2

Boiling point: 77 K or -196°C or –320 °F

O2

Boiling point: 90 K or -183 °C or -297 °F

N2 and O2

Balance between input (production) and output (destruction):

Input: plant/animal decaying

Sink: soil bacteria;

oceanic plankton-->nutrients

Input: plant photosynthesis

Sink: organic matter decay

chemical combination (oxidation)

breathing

Atmospheric CompositionImportant Trace Gases

Ahrens, Table 1.1, 3rd ed.

Which of these is now wrong even in the 4th edition of Ahrens?

Sourcesvegetative decayvolcanic eruptionsanimal exhalationcombustion of fossil fuels(CH4 + 2 O2 > 2 H2O + CO2)

Sinksphotosynthesis (oxygen production)dissolves in waterphytoplankton absorption (limestone formation)

Carbon Dioxide COCarbon Dioxide CO22

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 VariabilityPrecipitable Water (mm)

Some gases can vary spatially and daily

Aerosols

1 cm3 of air can contain as many as 200,000non-gaseous particles.

– 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 kilometersScientific Notation for distance would be?

Scientific Notation

Example…Distance between the Earth and the Sun is

150,000,000 kilometersScientific 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 100oCoC= 5/9 (oF-32)

• Kelvin (K) - absolute

K= oC+273Ahrens p27

What is Temperature?Microscopic ViewEnergy due to random

jiggling of moleculesRelated to average

molecular speed (v); 500 m/s for air at room temperature

Maxwell DistributionK.E.=(1/2)mv2=(3/2)kT m = mass of one moleculek = Boltzmann constant =1.38065×10−23 joule/K

(joule is unit of energy)

Impact of Extreme Temperatures on Humans

Hypothermia

Condition in which the internal temperature drops below that required for normal metabolism and bodily functions.

HyperthermiaCondition 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 1-2C (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

– Body temperature drops to 2-4C 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

– Body temp. drops below 32C (90F)– 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)– Body temp. drops below 30C (86F)– 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 life-threatening

– 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 Symptomswww.mayoclinic.com

• High body temperature of 104F (40C) 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 Symptomswww.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…• 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 eithera) # molecules in a constant volumeb) volume occupied by the same # molecules

ab

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.

Higher elevation Less air aboveLower pressure

Lower elevation More air above Higher pressureBottom

Top

Density and Pressure VariationKey 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 compressiblecompressible.

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.

massmass

massmass

massmass

massmass

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. pp

pp

pp

pp

Water versus Air

Pressure variation in water acts more like bricks, close to incompressible, instead of like springs.

Air:Lower density, Gradual drop

Higher densityRapid decrease Bottom

Top

Bottom

Top Water:Constant drop

Constant drop

A Thinning Atmosphere

Bottom

Top Lower density, Gradual drop

w/elevation

Higher density,Rapid decrease

w/elevation NASA photo gallery

Pressure Decreases Exponentially with Height

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

100 mb

10 mb

1 mb

16 km

32 km

48 km

Ahrens, Fig. 1.5

Equation for Pressure Variation

We can Quantify Pressure Change with Height /(16km)

MSL

MSL

where

is elevation in kilometers (km)

is pressure in millibars (mb)

at elevation z in meters (km)

is pre

(at elevation zin km)

ssure (mb

1

) at mean sea l

0

leve

Z

z

p

p

p

p −= ×

What is Pressure at 2.8 km?(Summit of Mt. Lemmon)

Use Equation for Pressure Change/(16 km)

MSL

(2.8km) /(16 km)

0.175

MSL

(at elevation Zin km) 10

(2.8 km) 1013mb 10

(2.8 km) 1013mb

set = 2.8 km, 10

10

(2.8 km) 1013mb 0.668 677mb

13 mb

Zp p

p

p

p

Z

p

−

−

−

= ×

= ×

= ×= × =

=

What is Pressure at Tucson?

Use Equation for Pressure Change

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

/(16km)M

MS

S

L

L(at e

set =

levation Zin

800 m

km) 10

, 1013 mb

Z

Z p

p p −= ×=

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 Symptomsen.wikipedia.org/wiki/Altitude_sickness

No appetite, nausea or vomitingFatigue or weaknessDizziness or light-headednessInsomniaPins and needlesShortness of breath upon exertionPersistent rapid pulseDrowsinessGeneral malaisePeripheral edema (swelling hands,

feet, and face)Sign on Mt. Evans CO

Life-threatening Conditionsen.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)– headache that does not respond to analgesics– unsteady walking– increasing vomiting– gradual loss of consciousness

Critical Altitude Conditionsen.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 Conditionsen.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 Sicknessen.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).

Nepalen.wikipedia.org/wiki/Nepal

Temperature (T) Profile• More complex than

pressure or density • Layers based on the

Environmental Lapse Rate (ELR), the rate at which temperature decreases with height. inversion

isothermal

6.5oC/km

Ahrens, Fig. 1.7

Higher AtmosphereMolecular 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 kmTemps 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 ProfileComplex vertical structure

Climate and Weather

“Climate is what you expect.

Weather is what you get.”-Robert A. Heinlein

WeatherWeather – 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

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 360Ahrens, p 431

Responsible for boxed parameters

Sky Cover and Weather Symbols

Ahrens, p 431

Ahrens, p 431

Wind Barbs

Direction

Wind is going towards

WesterlyWesterly from the West

Speed (accumulated)

Each flag is 50 knots

Each full barb is 10 knots

Each half barb is 5 knotsAhrens, p 432

65 kts from west

temperature dew point

SLP pressure

wind

cloud cover

Ohio State website

Practice Surface Station

Temperate (oF)Pressure (mb) Last

Three Digits (tens, ones, tenths)

Dew Point (later) Moisture

Wind Barb Direction and Speed

Cloud Cover Tenths total coverage

Ahrens, p 431

72

58

111

Decimal point

What are Temp, Dew Point, SLP, Cloud Cover, Wind Speed and Direction?

Practice Surface Station

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 360Ahrens, p 431

42

18

998

Decimal point

What are Temp, Dew Point, SLP, Cloud Cover, Wind Speed and Direction?

Surface Map Symbols

• Fronts

Mark the boundary between different air masses…later

Significant weather occurs near fronts

Current US MapAhrens, p 432

Radiosonde

Weather balloons, or radiosondes, sample atmospheric to 10 mb.

They measuretemperaturemoisturepressure

They are tracked to get windsAhrens, Fig. 1

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