Chapter 11: Atmosphere

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Section 1: Atmospheric Basics Objectives

1. Describe the composition of the atmosphere. 2. Compare and contrast the various layers of the atmosphere. 3. Identify three methods of transferring energy throughout the atmosphere.

A. Atmospheric Composition

• _____ N2 + _____ O2 + _____ other, including Ar, H2O vapor, CO2, and trace gases such as H, He, Ne, methane (CH4), ozone (O3), Kr, and Xe

• The atmosphere also contains tiny particles of dust, salt, and ice. • Key Atmospheric Gases

o The amount of H2O vapor varies (≤ 4%) with the seasons, with the altitude of a particular mass of air, and with the surface features beneath the air.

o _____ is the only substance in the atmosphere that exists in three states: solid, liquid, and gas.

o When H2O changes from one state to another, heat is either absorbed or released, which greatly affects weather and climate.

o The amount of CO2 varies (≤ 1%) with the seasons and with fossil fuel combustion emissions.

o Both CO2 and H2O vapor help regulate the amount of energy the atmosphere absorbs. o Ozone (O3)

- _________________________________________________ - _________________________________________________ - Found primarily in the ozone layer of the stratosphere - Is important because it absorbs ______________________________ - Evidence indicates that the ozone layer is thinning

A. Structure of the Atmosphere

• Made up of several layers, which differ in composition and temperature

1. Troposphere • Is the layer closest to Earth’s surface • Contains most of the atmosphere’s mass (due to gravity), so pressure (P) and density

(D) are highest nearest the surface • ___________________________________________________ • ___________________________________________________ • Has an upper limit called the tropopause, which varies in height

2. Stratosphere • Is located above the tropopause • ___________________________________________________ • T increases (P and D decrease) with altitude • Has an upper limit called the stratopause

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3. Mesosphere • Is located above the stratopause • T decreases (P and D decrease) with altitude • Has an upper limit called the mesopause

4. Thermosphere • Is located above the mesopause • Contains only a minute portion of the atmosphere’s mass • ___________________________________________________

___________________________________________________ ___________________________________________________

• T increases (P and D decrease) with altitude

5. Exosphere • Is the outermost layer of Earth’s atmosphere • ___________________________________________________ • Fades into space… There is no absolute boundary between Earth’s atmosphere and

space. B. Solar Fundamentals

• The Sun is the source of all energy in the atmosphere. • Solar energy is transferred to Earth and throughout the atmosphere through radiation,

conduction, and convection.

1. Radiation • ___________________________________________________ • Is absorbed by Earth, which also continuously sends energy back into space • Absorption rates depend on __________________________________

and __________________________________ o Most solar radiation travels through the atmosphere at ________________

wavelengths, which are not easily absorbed o Earth’s surface re-radiates energy with ________________ wavelengths,

which warms the atmosphere through ________________ and ________________

2. Conduction • Is the transfer of energy that occurs when molecules collide • ___________________________________________________ • ___________________________________________________

___________________________________________________ • Affects only a very thin atmospheric layer near Earth’s surface

3. Convection • Is the transfer of energy by the flow of a heated substance

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• Creates _____________________, which are partially responsible for ___________________________________________ and, in turn, ___________________________________________________ (1) Pockets of air near Earth’s surface are heated, become less dense than the

surrounding air, and rise. (2) As the warm air rises, it expands and starts to cool. (3) When it cools below the temperature of the surrounding air, it increases in density

and sinks.

Section 2: State of the Atmosphere Objectives

1. Describe the various properties of the atmosphere and how they interact. 2. Explain why atmospheric properties change with changes in altitude.

A. Temperature vs. Heat

• Temperature (T) o Is a measurement of how rapidly or slowly molecules move around o Can be measured in degrees Fahrenheit (°F), Celsius (°C), or in kelvins (K; SI unit)

Freezing Point* of H2O Boiling Point* of H2O Absolute Zero* _____oF _____oF -523 oF _____oC _____oC -273 oC _____ K _____ K 0 K

*Measured at P = 1 atmosphere (atm)

o ________________: the point at which molecular motion theoretically stops

• Heat o Is the transfer of energy that occurs because of a difference in T between substances o ___________________________________________________

« Heat is the transfer of energy that fuels atmospheric processes, while T is used to measure and interpret that energy.

• _____________________: the T to which air must be cooled at constant pressure to reach saturation

• _____________________: the point at which the air holds as much water vapor as it possibly can and at which condensation can occur

• _____________________: change in state from a gas to a liquid B. Vertical Temperature Changes

• ______________________________________________________ • Dry adiabatic lapse rate

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o Is the rate at which rising unsaturated air, to which no heat is added or removed, will cool

o ≈_______________________ • If the air continues to rise, it will eventually cool to its condensation T at an altitude

known as the _____________________________________________, or LCL. Above the LCL, air is saturated and cools more slowly.

• Moist adiabatic lapse rate o Is the rate at which saturated air cools o ≈_______________________ (ranges from about 4°C/1000 m in very

warm air to almost 9°C/1000 m in very cold air) C. Pressure-Temperature-Density Relationships

• ____________________________________________________________________________________________________________ ____________________________________________________________________________________________________________

• However, in most atmospheric interactions, neither D nor P remains unchanged. o T varies with changes in both P and D; T is proportional to the ratio of P to D, which

decreases with increasing altitude. o Temperature inversion

- Is an increase in T with altitude in an atmospheric layer - Can occur when the lower layers of the atmosphere lose heat to Earth’s surface

and become cooler than the air above them - Can act like a lid to trap pollution under the inversion layer - Can have a profound effect on weather conditions

D. Wind

• ____________________________________________________________________________________________________________ ______________________________________________________

• Moves faster with increasing altitude (generally) E. Humidity vs. Relative Humidity

• ________________: the amount of water vapor in air… Air in the lower portion of the atmosphere always contains at least some water vapor.

• Relative humidity (RH) o Is the ratio of water vapor in a volume of air compared to how much water vapor that

volume of air is capable of holding o ___________________________________________________

___________________________________________________ - If the T of air increases and no additional water vapor is added, its RH decreases. - If more water vapor is added to the air, its RH increases.

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o Is expressed as a percentage: o If a certain volume of air is holding as much water vapor as it possibly can, then

it’s RH = 100%. o If that same volume of air is holding half as much water vapor as it can, its RH =

50%, and so on.

Section 3: Moisture in the Atmosphere Objectives

1. Explain how clouds are formed. 2. Identify the basic characteristics of different cloud groups. 3. Describe the water cycle.

A. Cloud Formation

• ________________ is the tendency for air to rise or sink as a result of differences in D.

• Clouds form (1) ___________________________________________________ (2) Around __________________________________, which are small

particles in the atmosphere, such as dust, sea salt, sulfur and nitrogen oxide aerosols. (3) Due to __________________________________, which occurs when

wind encounters a mountain and is forced upward where it expands and cools. (4) ___________________________________________________

o When warmer air collides with cooler air, the majority of the warmer air will be forced to rise over the more-dense, colder air.

o As the warm air cools, the water vapor in it condenses, forming a cloud.

• Stability, or the ability of an air mass to resist rising, is determined by how rapidly any given mass of air cools. o The rate of cooling depends on the T of rising air relative to the T of the stationary

surrounding air that it passes through. o If the temperature of the surrounding air falls more quickly with increasing altitude, it

continues to rise. ________________________________________ ___________________________________________________

« ______________________________________________________

• Latent heat is energy stored in water vapor that is released when condensation occurs. o The energy stored in the water vapor comes from the change in state from liquid

water into water vapor, a gas. o As water vapor condenses back into liquid water, heat is released.

« The amount of water vapor present in the atmosphere is a significant source of energy because of the latent heat it contains.

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B. Types of Clouds • When a rising air mass reaches its ________________________________,

or LCL, its water vapor condenses into liquid water. • If the D of these water droplets is great enough, they become visible in the form of a

cloud. • This process can take place at many different altitudes and form different cloud shapes. • Cloud classification was originally developed in _____ by English naturalist

__________________________________. • The modern classification system groups clouds by

(1) ___________________________________________________ (usually denoted as a prefix): o ______________ – low clouds that form below 2000 m o ______________ – middle clouds that form between 2000 and 6000 m. o Cirro – high clouds that form above 6000 m and are composed of ice crystals. o ______________ – develop vertically

(2) _________________________________ (usually denoted as a suffix): o ______________ – gray; precipitation-producers o ______________ – layered/featureless sheet o ______________ – puffy/lumpy o ______________ – wispy/stringy

« Clouds may be classified as: o Stratus, cumulus, and stratocumulus o Altostratus, altocumulus, and altocirrus o Cirrocumulus, cirrus, and cirrostratus o Nimbostratus, nimbus, and cumulonimbus

C. Precipitation

• ________________________ occurs when cloud droplets collide and join together to form a larger droplet. When the droplet becomes too heavy to be held aloft, gravity takes over and it falls to Earth.

• ________________________ includes all forms of water, both liquid and solid, that fall from clouds including rain, snow, sleet, and hail.

D. The Water Cycle

• Is the constant movement of water between the atmosphere and Earth’s surface. • Includes the following processes:

(1) ________________________: H2O (liquid) à H2O vapor (gas) (2) ________________________: H2O vapor (gas) à H2O (liquid) (3) ________________________