The Atmosphere
The Atmosphere
Introduction
Atmosphere Connections
Each day, Earth’s 6.3 billion people interact with the atmosphere in many ways. Jet pilots, for example, fly
through the atmosphere and must be intimately familiar with weather patterns. Satellite TV stations send
signals through the atmosphere that bounce off satellites and then back through the atmosphere to
satellite dishes scattered far and wide. Many of these interactions are invisible and involve gases, heat, or
energy waves. The most basic of these interactions is, of course, breathing. In fact, right now as you
read these words, you are inhaling oxygen (O2) and exhaling carbon dioxide (CO2). We humans need a
steady supply of “clean” air.
The process by which humans inhale O2 and exhale CO2 is known as respiration. This exchange of gases
is the respiratory system's means of getting oxygen to the blood. Without air, a person will die faster than
if they were deprived of any other human need, such as food, water, cable television, and the Internet.
Most of us can only hold our breath for about a minute. After 30 seconds, it begins to get uncomfortable.
After 3 to 5 minutes, hypoxia, or oxygen deprivation sets in, brain cells begin to die and you’re on your
way to being dead. Note: This is not part of your lab assignment.
Besides breathing, how else does your body interact with the atmosphere? Maybe you’ve never asked
yourself this question before, but there are many other ways that your body and the atmosphere interact.
Have you ever sneezed? Sneezing is a reflex response to the presence of atmospheric particulates, such
as pollen or dust, in your nose. We also sneeze when we are sick with a cold. Sneezing sprays the
atmosphere around you with microscopic bacteria and fluid at a speed close to the fastest baseball
pitchers, about 100 miles per hour.
What other bodily functions interact with the atmosphere? How about burping or “passing” gas, that
releases nitrogen, oxygen, carbon dioxide, hydrogen, and methane into the atmosphere as a result of the
process of digestion. In addition, we all have our own unique body odor caused by the mixing of
perspiration and bacteria that those close to use can usually smell.
Have you ever made a sound? Sound travels through the atmosphere in waves called, not surprisingly,
sound waves. What do you think of when you heard the word “waves”? Most of us probably think of
waves in the ocean. If you’re a sports fan, you might think of how crowds in stadiums sometime make a
“human” wave. Waves are made up of both crests, which are the top of the wave, and troughs, which are
the bottom. The distance from one crest to the next is called wavelength.
There are many types of waves that pass through the atmosphere. Your eyes see light, which travels
Fig. 1: Electromagnetic spectrum (Source: NASA)
1
through the atmosphere in waves. If you’ve ever been sunburned or gotten a tan, it was ultraviolet waves
that cause the temporary changes in your skin color. So you see there are many ways that your body
interacts with the atmosphere and most of them are invisible. Figure 1 depicts the wavelengths of various
forms of energy ranging from radio waves, which are quite large, to X-rays and gamma rays, which are
infinitesimal.
Atmospheric Composition
The “air” you are breathing is actually a mixture of gases. This mixture of gases is known as the
atmosphere. The word “atmosphere”, by the way, comes from the Latin “atmosphaera”, which was
cobbled together from the from Greek word “atmos”, meaning “vapor”, and the Latin word “sphaera”
translated as sphere. Quite literally then, the atmosphere is the “vapor-sphere”.
This gaseous composition of the atmosphere is usually expressed by percentage volume, that is, each
gas’s relative part of the total mixture. For example, 78% of the atmosphere is made of the gas nitrogen
(N2), 21% is composed of oxygen (O2), and .9% is made up of argon (Ar). These three gases together
make up 99.9% of the atmosphere. Other “vapors” or gases that make up the atmosphere include water
vapor (H20), Carbon Dioxide (CO2), Neon (Ne), Helium (He), Methane (CH4), Krypton (Kr), and Hydrogen
(H2). These gases, along with many others, are referred to as “trace” gases, in that there are small traces
of them in the atmosphere. The concentration of gases in the atmosphere is measured in parts per
thousand (ppt), parts per million (ppm) and parts per billion (ppb).
The atmosphere also contains solid material in addition to the gases above. This solid material is very
small, between .1 and 25 thousandths of a millimeter, or micrometer and is known as particulates. To give
you some idea how small particulates are, a single grain of table salt is about 100 micrometers in size,
and so we are talking about a mass of material that is 1/1000 to ¼ the size of a grain of table salt. In
addition to gases and solids, liquids also exist in the atmosphere. The most common one of these is
water, good old H20. Water exists in the atmosphere as clouds, rain, and fog, all of which are visible and,
therefore, familiar. The table below shows the composition of the atmosphere and the cumulative volume
of each compound.
Full Name
Formula % Volume
# Of Parts
Unit
Variable?
Cumulative
Volume
Nitrogen
N2
78.1%
78 parts per Hundred
78.10%
Oxygen
O2
20.9%
21 parts per Hundred
99.00%
Argon Ar
0.934%
9
parts
per
Thousand
99.93%
Water Vapor
H20
0.04%
400 parts per million
variable
99.97%
Carbon Dioxide
CO2
0.0369%
370 parts per million
99.99%
Neon
Ne
0.00182%
18 parts per Million
100.00%
Helium He
0.000524%
5
parts
per
Million
100.00%
Methane CH4
0.0001842%
2
parts
per
Million
100.00%
Krypton
Kr
0.000114%
1 part per
Million
100.00%
Hydrogen
H2
0.0001%
1 part per
million
variable
100.00%
Nitrous Oxide
N20
0.0000315%
315 parts per billion
100.00%
Carbon Monoxide
CO
0.00002%
200 parts per billion
variable
100.00%
Xenon
Xe
0.0000087%
87 parts per billion
100.00%
Ozone
O3
0.000005%
34 parts per billion
variable
100.00%
Sulphur Dioxide
SO2
0.000002%
20 parts per billion
variable
100.00%
Ammonia
NH3
0.000002%
20 parts per billion
variable
100.00%
Formaldehyde
CH20
0.000001%
10 parts per billion
variable
100.00%
Nitrogen Dioxide
NO2
0.0000003%
3 parts per
billion
variable
100.00%
Nitric Oxide
NO
0.0000003%
3 parts per
billion
variable
100.00%
Hydrogen Sulfide
H2S
0.0000002%
2 parts per
billion
variable
100.00%
Hydrochloric Acid
HCl
0.00000015%
2 parts per
billion
variable
100.00%
Nitric Acid
HNO3
0.0000001%
1 part per
billion
variable
100.00%
2
Methyl Chloride
CH3Cl
0.00000006%
600 parts per trillion
100.00%
Freon-12
CF2Cl2
0.0000000544%
546 parts per trillion
100.00%
Carbonyl Sulfide
COS
0.00000005%
500 parts per trillion
100.00%
Freon-11
CFCl3F
0.0000000263%
263 parts per trillion
100.00%
Carbon Tetrachloride CCl4
0.000000098%
97 parts per trillion
100.00%
Freon-113
C2F3Cl3 0.000000082%
82 parts per trillion
100.00%
Methyl Chloroform
CH3CCl3 0.000000056%
47 parts per trillion
100.00%
HCFC-22
CHClF2
0.0000001525%
153 parts per trillion
100.00%
HFC-23
CHF3
0.0000000011%
23 parts per trillion
100.00%
Sulphur Hexaflouride SF6
0.000000004%
5 parts per
trillion
100.00%
Perfluoroethane C2F6 0.000000004%
4
parts
per
trillion
100.00%
Triflouromethyl
SF5CF3 0.00000000012% .12 parts per trillion
100.00%
Sulphur Pentaflouride
Sources
1. McGraw-Hill Encyclopedia of Science and Technology, 1987, McGraw-Hill, Inc.
2. Carbon Dioxide Information Analysis Center
Layers of the Atmosphere
So we see that the atmosphere contains gases, suspended liquids, and solids that entirely surround the
earth. The earth's gravity pulls these gases, liquids, and solids toward the surface. Not surprisingly, there
are more gases closer to the surface and fewer as you move away. Therefore, the earth's atmosphere is
denser at the surface and gradually thins as altitude increases.
The atmosphere begins at sea level, (and in some places on land that are just below sea level) and
extends outward some 6,000 miles (10,000 km) into space. From the surface to an altitude of 50 miles
(80 km) the chemical composition is of the atmosphere is highly uniform. Due to this uniformity, this
section of atmosphere is known as the homosphere. The homosphere, or lower atmosphere, is divided
into various layers. The troposphere is the layer closest to the surface and it extends outward an average
of 11 miles (18 km), though it is thicker at the equator and thinner at the poles. Beyond the troposphere is
the stratosphere, which extends from 11 to around 30 miles from the surface. The mesosphere starts at
around 30 miles and extends outward to 50 miles from the surface.
Above 50 miles, the chemical composition of the
atmosphere changes with altitude. This layer is
known as the upper atmosphere or heterosphere.
This upper layer is also known as the
thermosphere and it extends outward several
thousand miles with no real boundary between
the upper atmosphere and space.
Though the atmosphere extends outward several
thousand miles, one half of the gas molecules
that comprise the atmosphere are located within
the first 3.5 miles (5.6 km), or 18,840 feet. Fully
90% of the molecules are within the first 10 miles
(16 kilometers), or 52,580 feet, and some 97% of
gas molecules are packed within the first 18
miles (30 km). Gravity keeps the atmosphere
very close to the earth's surface. Also, since most
human activities take place from sea level to
around 10,000 feet or 2 miles, conditions in the
layer of the lower atmosphere closest to the
surface, the troposphere, are what affects us day
to day. The troposphere, #8 in the diagram,
Fig. 2: Layers of the atmosphere (NASA)
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extends outward to about 11 miles, and contains about 90% of the molecules in the atmosphere.
Natural Changes in the Atmosphere
The troposphere is an extremely dynamic and ever changing system. Every day, the light, clouds, and
heat energy in the troposphere go through a million variations. These changes affect daily life in
thousands of subtle and direct ways and, for generations, humans have been fascinated by the
troposphere’s daily changes, which are known as weather. We all have a sense of what weather is. On
some days it is rainy, and some days sunny. Some days are hot and some are cold. Sometimes the wind
blows with intense ferocity.
Daily changes in the troposphere are known as weather. Long term, average conditions are referred to as
climate. Weather is more extreme than climate, meaning that daily ranges of temperature, precipitation,
pressure, and wind are greater than the long-term extremes of climate. Since climate refers to long-term
average conditions, it is more moderate.
One way to look at the relationship between weather and climate is to take a look at your checking
account. The monthly balance for twelve months of a year would represent climate and the daily inflows
and outflows of funds, weather. Your daily balances might vary a great deal from day to day while your
monthly balances, which are an average of your daily balances, would be more consistent. In the same
way, weather changes much more rapidly than climate and you know this from your own experience. One
day it might be warm and close to 60 degrees and the next day, cold and in the mid-forties. Climate also
changes, but on a much longer time scale. Later in this section on atmosphere we’ll look more closely at
climate change.
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ESA21: Environmental Science Activities
Activity Sheet
The Weather
Student Name:
Professor Name:
The Weather – Activity Sheet
The objective of this exercise is to have you observe atmospheric conditions as well as develop your
understanding of major atmospheric concepts. For this exercise, you are asked to observe and record
weather conditions for four days. In addition, you are asked to answer questions about your observations,
as well as respond to a series of questions on general atmospheric characteristics. In the second part of
the exercise, you are asked to perform a number of calculations relating to atmospheric conditions and
characteristics.
Part One - Weather Observation
Please read the exercise completely before you begin. Also, printing this exercise before you begin will
help you in carrying out the exercise.
1. Keep a log of atmospheric conditions for 4 days and record the following information. Find out
information from any one of the following sources such as local newspapers, television news, or the
Weather Channel.
Day One
Day Two
Day Three
Day Four
Date
Location
High Temperature (˚F)
Low Temperature (˚F)
High/Low Difference
Air Pressure (AP)
AP Rising or Falling?
Wind Direction
Wind Speed (mph)
Time of Sunrise
Time of Sunset
Length of Daylight
Answer the following questions with regards to the atmospheric observations you made and then
complete the temperature conversions below.
Question 1 - What is the overall four-day temperature trend?
Question 2 - What is the overall four-day pressure trend?
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Question 3 - Was the wind direction consistent over the four-day period? If not, what pattern did you
observe?
Question 4 - Was the wind speed consistent over the four-day period? If not, what pattern did you
observe?
Question 5 - What pattern did you observe with regards to the amount of daylight over the four-day
period? Are the days getting shorter or longer?
Part Two - Temperature Conversion
Temperature can be measured in different scales. In the U.S. we use the measure temperature in
degrees Fahrenheit (F). Most other countries and many scientists use the Celsius (C) scale. In the
Celsius scale, water boils at 100˚C and freezes at 0˚C. The formulas for converting from one temperature
scale to the other are as follows:
˚F = (9/5 x ˚C) + 32 and ˚C = (5/9) x (˚F – 32)
Complete the following calculations and place your answer in the center column below:
15 degrees Fahrenheit
degrees Celsius
75 degrees Fahrenheit
degrees Celsius
32 degrees Fahrenheit
degrees Celsius
31 degrees Celsius
degrees Fahrenheit
13 degrees Celsius
degrees Fahrenheit
0 degrees Celsius
degrees Fahrenheit
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