Energy Transfer in the Atmosphere
Radiation heats the Earth’s surface. Some of this
energy is re-radiated out of the surface as infrared
radiation and absorbed by the atmosphere. In addition,
air particles just above the Earth’s surface are heated
through conduction, and transfer energy to other
parts of the atmosphere through convection currents.
High-Low Pressure Cells
Wind – movement of air from _______ to _______ pressure
Air Mass – a parcel of air with similar temperature and humidity
When an air mass cools, gases ____________, creating ________ pressure. This
________ pressure air mass is now more dense than its surroundings so it sinks.
When an air mass warms, the gases ___________, creating _______ pressure. This
_____ pressure air mass is also now less dense than its surroundings so it floats up.
Low Pressure – Rising Air Parcel High Pressure – Sinking Air Parcel
These changes in air pressure are caused by uneven surface heating. Energy is being
transferred through the atmosphere by _______________________________________
If these changes occur over a large scale they are called ________.
A. High Pressure Cell – an area of high pressure where air cools (usually over cool land
or oceans), shrinks and sinks. As this air sinks it becomes warmer and drier often
resulting in clear skies.
B. Low Pressure Cell – an area of low pressure where air warms (usually over warm land
or oceans), expands and rises. As this air rises it cools, allowing water vapour to
condense and turn into clouds and precipitation.
Note: Due to the Coriolis effect air/wind flows clockwise ______ of the high pressure
cell in the northern hemisphere. Air/wind flows counter-clockwise _______ the low
pressure cell in the northern hemisphere. Air flows highlow!!!
Coriolis effect –
apparent deflection of
moving objects when
they are viewed
from a rotating frame
Prevailing winds – winds that blow in a consistent pattern over large portions of the Earth
Prevailing winds are influenced by
changes in pressure, but also by
changes in the _______________
(ex. Coast Mountains cause
moist air to condense leaving air
drier when it reaches the Okanagon)
Local Winds – Land & Sea Breezes
Land and sea breezes are created by differences in heating over land and water.
Recall: Water has a _____________ heat capacity than land so it warms up slower, but
also retains its heat more efficiently than land
During the day, land heats up faster than a nearby body of water. The land radiates heat,
which warms air at the surface. The warm air ________, replaced by cooler air drawn in
from the water. The wind created is called a ______ (onshore) breeze.
During the night, the land cools down faster than the nearby water. The warm air over
the water rises and draws in cool air over the land. The wind created is called a _______
Global Wind Systems
Wind systems are zones of ___________________ which result from convection currents
and the Coriolis effect. Large scale convection currents called ______ (ex. Hadley cells
at equator) form due to uneven surface heating producing _________ systems. The
Earth’s rotation affects the direction of these ________ systems.
Note: The equator receives the most thermal
energy since radiant energy from the
Sun is receiving light over a concentrated
area in relation to higher latitudes.
The Earth has three major wind systems
that occur in each hemisphere:
Note: Large scale ocean
currents are also similarly
affected by changes in
Prevailing wind also flows in the upper atmosphere. Jet streams are narrow bands of
high-speed westerly winds formed by convection currents that occur at the top of the
troposphere. Jet streams have a large influence on weather patterns. See pg. 441
Thunderstorms, Tornadoes and Cyclones
Thunderstorm – a weather system that
produces rain, hail, strong winds,
thunder and lightning.
Thunderstorms are formed when water
vapour in rising warm air condenses,
releasing thermal energy, further
heating the surrounding air. This air
rises rapidly up producing further clouds/
precipitation. Thunderstorms occur
where atmospheric conditions are
unstable (ex. mountain bases, tropics, etc.)
Tornado – a violent funnel-shaped column of rotating
air that touches the ground
Tornadoes usually form when high-altitude
horizontal winds meet thunderstorms. The
horizontal winds cause the rapidly rising air
to rotate, producing a spinning vortex of air
called a funnel cloud. If the funnel cloud
reaches the ground it becomes a tornado.
Surface winds caused by tornadoes
can reach up to 400km/hr.
Tropical Cyclone - a storm system
characterized by a low pressure center
and numerous thunderstorms that
produce strong winds and flooding rain.
A tropical cyclone forms when moist air rises,
resulting in condensation of water vapour
contained in the moist air. The resulting
precipitation releases large amounts of
thermal energy further heating the air
enhancing the low pressure area.
Further air rushes into the low pressure
area enchancing wind speeds. Wind speeds
can reach up to 240km/hr.