Physical Geography Lecture 05 - Atmospheric Energy and Global Temps 101216

Chapter 3
Atmospheric Energy
and
Global Temperatures

Earth’s Energy Balance
or:
What comes in must go out!
 The sun is the power source that drives
many of Earth’s flow systems (storms,
waves, ocean and wind currents)
 When the sun’s energy (sunlight) enters
our atmosphere, its inputs must be
balanced by equal outputs
 This energy must be redistributed over the
globe to maintain the conditions of our
current lifelayer

Net Radiation
 Net radiation is the difference between the
radiation energy surplus and deficit
 Can be measured daily, monthly, yearly, even
by century, in order to help us answer the
question, “Are we heating up or cooling
down?”
 Determining net radiation begins with a
number of insolation losses in the
atmosphere…

Surplus vs. Deficit
A surplus in your checkbook is a good thing!
A surplus of energy within Earth’s systems
generally means an increase in temperature
and changes in Earth’s systems’ circulations
(NOT such a good thing!)

Hypothetical Radiation Balance

Reflection
 Albedo—the % of
insolation reflected
back to space

The Redistribution of Energy
 Sensible heat transfer  Latent heat transfer

 Sensible heat is heat that can be felt and
measured
Moved by conduction; transferred by global
winds and ocean currents
Sensible Heat

Latent Heat
 Latent heat cannot be sensed or directly
measured
Heat that is stored or released during the change of
state of solids, liquids, and gases
Movement occurs most often through condensation
and evaporation (Ex.: the formation of clouds or the
evaporation of ocean water)
Water in the atmosphere is the most important mover
of latent heat, which ultimately helps to balance Earth’s
energy budget

Review
1.What is the power source that
drives Earth’s flow systems?
2.What happens if Earth’s energy
inputs and outputs are unbalanced?
3.Describe the different ways
incoming solar radiation is balanced
by outgoing radiation (draw a
diagram, if that makes it easier to
explain).

4.What is albedo? What kinds of
surfaces have a high albedo? What
surfaces have a low albedo?
5.Describe convection.
6.What is counterradiation? What
kinds of gases contribute to
counterradiation? What is the
greenhouse effect?
7.What is the difference between
sensible heat and latent heat?

Temperature
 Temperature—a measure of the level of
sensible heat of matter; an expression of
atomic motion
Heat moves from substances of higher temp.
to substances of lower temp. until their
temperatures equalize

Fahrenheit, Celsius, and Kelvin
 Three systems of temperature
measurement in use internationally:
Fahrenheit, Celsius, and Kelvin
In order to convert from Fahrenheit to
Celsius and back, use these formulae:
 C = 5/9 (F-32)
 F = 9/5 C + 32
 0K = absolute zero—the point at
which all molecular motion ceases
-273.15C or -459.67F
Room temperature is about 295K
Converting K to C only requires
adding 273 (e.g. 3C = 276K)
Especially useful when dealing with
very low temperatures, as there are no
negative numbers

Isotherms
 Isotherms—
lines on a map
that connect
points of equal
temperature

Daily and Seasonal
Temperature Changes
 Daily temperatures are influenced by
patterns of sunrise and sunset, which are
the result of seasonal changes, themselves
the result of latitude.

Daytime Temperatures:
Normal Condition

Temperature Inversions
 Temperatures are generally
hotter during the day at the
surface and cooler above.
 A temperature inversion
occurs when surface
temperatures are cooler than
the air above for some vertical
distance.
 Once a temperature inversion
occurs, it tends to persist until
all heat has been transferred
back out to space.
 There are four common types
of temperature inversions….

Subsidence Inversion
 Subsidence inversions
Occur in the upper atmosphere
Result of air slowly descending due to a high pressure
cell
As the air descends, it compresses and warms, and
this warm layer sits atop cooler air below
Most common in the subtropics year-round and in the
Northern Hemisphere in winter
Do not sink lower than a few hundred meters above
sea level due to low-level turbulence

Radiational Inversion
 Radiational inversions—the result of
rapid radiational cooling
Most common in high latitudes, especially at
night
Long wave radiation (heat) is radiated back
out to space and has left the lower portion of
the troposphere, but has not yet entirely left
the air above.

Advectional Inversion
 Advection = “wind” (any horizontal
movement of air, usually in response to
atmospheric pressure differences)
 Advectional inversions—a horizontal flow
of air displaces warmer air upward
Especially common along coasts, as air moves
out of high pressure zones over the water and
into a low pressure zone over land.

Cold-air-drainage Inversion
 Cold-air-drainage inversions—cooler air on mountain
slopes sinks into a valley below, forcing the warmer air in
the valley to rise upward
 Most common in the midlatitudes, especially in winter

Daily Temperature Lags
 Insolation levels rise as the sun rises, reach a
maximum at noon, then decrease and end at
sunset
 The coldest time of day is actually after the sun
has risen
 The hottest time of day is a few hours after noon
 The hottest time of day (maximum daily
temperature) varies based on such factors as
cloudiness, windiness, proximity to a large body
of water, and even storms.

Seasonal Temperature Lags
 In summer, monthly insolation is highest
 In winter, monthly insolation is lowest
 In between, during the equinoxes, insolation levels are in
the middle
 Highest monthly temperatures tend to be one month after
the summer solstice
 Lowest monthly temperatures also follow one month after
the winter solstice
 Although radiation levels are similar for both the fall
(autumnal) and spring (vernal) equinoxes, temperatures
are considerably warmer following the summer months
than following winter. The temperatures of the equinoxes
are not the same because each reflects the temperatures
of previous seasonal conditions.

Factors influencing differences in
temperature
 Latitude
 Elevation/Altitude
 Cloud Cover and Albedo
 Proximity to a Water Body
Differential heating of land and water
Ocean currents
 Proximity to an urban area

January—Global Temperatures
Latitude

July—Global Temperatures
Latitude

Elevation
 As discussed previously…
Remember the ELR!

Distribution of Land and Water:
Properties of Land vs. Water

Proximity to a Water Body:
Isotherms on a Hypothetical Continent

Proximity to a Water Body:
Exterior (Coastal) vs. Interior (Continental) Locations

General Circulation of the Oceans

Proximity to an Urban Area:
The Urban Heat Island

Global Temperature Patterns: Mini Quiz!
 Which will be colder? Highland areas (areas of higher elevation) or
lowland areas in the same region?
 Highlands are colder than surrounding lowlands.
 Does temperature increase or decrease with latitude (getting
closer to 90°N or S)?
 It decreases.
 True or False? Seasonal isotherm shifts are more dramatic over
land areas than over oceans.
 True
 Which influences temperatures on the edges of continents: warm
or cold ocean currents?
 Both warm and cold currents affect temperatures on nearby
land
 Equatorial locations receive an even amount of insolation year
round. How does that affect their temperature patterns?
They tend to have more even temperature patterns

Review
1.What is the difference between heat and
temperature?
2.True or False? Heat flows from the hot
object toward the cold object until both
objects are the same temperature.
3.Lines on a map that connect points of
equal temperature are called...
4.Draw two graphs: one showing a normal
atmospheric temperature condition and
one showing a temperature inversion.
5.Describe the 4 temperature inversions.

6.The hottest time of day is just after
noon and the coldest time is just after
sunrise. Why?
7.Name the 5 factors influencing the
temperature of any location.
8.Why does being near a body of water
make a location warmer in winter and
cooler in summer than locations further
inland? (Remember the properties of
land vs. water!)
9.What is an urban heat island?

Physical Geography Lecture 05 - Atmospheric Energy and Global Temps 101216

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Physical Geography Lecture 05 - Atmospheric Energy and Global Temps 101216