 Factors that control our weather: the
daily weather cycle and the seasons
 Temps are usually lowest right before
sunrise and warmest in the midafternoon
Short-term factors that affect
temps: Cloud cover and
regional weather systems
Long-term factor that affects
temps.: Seasons
Heating of the Atmosphere- Complete the
Handout-page 108
Conduction moves heat from
Earth into the atmosphere as
air touches Earth’s surface
Direct absorption of
insolation from the sun by
gases and aerosols moves
heat into the atmosphere
Absorption of long-wave
infrared radiation from Earth’s
surface moves heat into the
atmosphere
Much of the infrared absorption
by the atmosphere is due to the
presence of water vapor,
methane and carbon dioxide
The larger the amounts
of these greenhouse
gases, the more heat is
absorbed by the
atmosphere
Condensation and
sublimation release
large amounts of stored
heat, directly heating
the atmosphere
 Condensation and sublimation
release this energy when clouds,
fog, dew and frost form
 The Coriolis Effect, which results
from the rotation of Earth and
wind, causes friction where the
atmosphere and Earth’s surface
meet
This friction produces heat,
which is absorbed by the
atmosphere
Heat energy is transferred
within the atmosphere by
convection, caused by
differences in air pressure
 Convection currents/Convection
cells: energy within the atmosphere
moves in a circular pattern,
transferring heat
 Winds are parts of the convection
currents that are parallel to Earth’s
surface
 When a gas expands, its
temperature decreases
 When a gas is compressed, its
temperature increases
 When air rises in the atmosphere it
expands and its temperature
decreases
 When air descends, it is compressed
and its temperature increases
 Usually, air temperature in the
troposphere decreases with increasing
altitude because as air rises there is less
air above it and less air pressure, and
thus the air expands and cools.
 Cloud cover during the day reflect
solar energy back into space
generally making temps colder
 Cloud cover at night acts like a
blanket, holding heat energy to
Earth, generally making temps
warmer
We measure temperature with a
thermometer
Typically, a thermometer has a
bulb of liquid that expands
when heated and contracts
(moves down the neck) when it
is cooled
Temperature is measured in
Fahrenheit, Celsius or Kelvin
ESRT PAGE 13
Lines of equal temperature
are called
isotherms
 Air pressure is caused by the weight of the
atmosphere
 DO NOT WRITE: Air is relatively light, but
the atmosphere goes many miles above
Earth, exerting a pressure of nearly 15
pounds per square inch
 Write This: Air pressure is greatest at
Earth’s surface and decreases with altitude
 Air pressure is exerted in all directions,
which is why we can’t feel it
 Air pressure allows us to drink through
straws- as you drink, you lower the air
pressure in the straw. The air pressure
on the surface of the liquid outside the
straw is now higher than inside the
straw.
 Barometer: instrument used to
measure air pressure
 All barometers measure the effect of
the weight of the atmosphere
Meteorologists measure
pressure in millibars (mb)
Pressure at sea level:
1013.2 mb
ESRT page 13
 In groups of 3-4.. WITHOUT LOOKING AT YOUR
NOTES!
a. List two differences between rotation and revolution
b. What is condensation?
c. What is sublimation?
d. What happens to air temperature as a gas expands?
e. What happens to air temperature as a gas compresses
or contracts?
f. Draw a picture of a convection cell