Page 42 - Oceans

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oceans and the atmosphere

The heat of the Sun makes water evaporate from oceans and rise

into the air as water vapor. The vapor then cools to form clouds
and rain. This evaporation effect is most intense near the equator,
where it creates a zone of huge storm clouds and heavy rain. The

rising air is replaced by air drawn in from farther north and south,
where cooler air is sinking. This airflow creates prevailing winds
that blow across the tropical oceans. The Earth’s rotation makes
these tropical winds swerve toward the west. Meanwhile, air drawn
toward the poles from the temperate regions sweeps eastward.

These prevailing winds carry weather systems with them, and in
many regions they have a big

Cold air sinks influence on climate.
over the Arctic
polar Cell and flows south
≤ rising vapor
About 100,000 cubic miles (425,000 cubic km)
of water evaporates from the oceans each year.
Low-level air The water vapor mixes with warm air above the
flows north in oceans, which tends to rise above colder, denser
temperate zone atmosphere
air. When the air rises it expands and cools down.
ferrel This makes the vapor condense into tiny water
Cell droplets that form clouds and rain.

Air sinks over
the subtropical
desert zone
the spinning planet
Dry desert air
flows south Earth rotates from
west to east
hadley
Cell
High-level Northern air moving
tropical air carries away from the tropics
heat north swerves right, toward
the east
< CirCulating Cells Northern air
When the warm air moving toward the
rising off tropical equator swerves right,
oceans reaches a toward the west
height of about
hadley 10 miles (16 km), it
Cell meets the warmer air
of the stratosphere, and Southern air moving
toward the equator
stops rising. Pushed aside by Southern air turns left, but also
more rising air, it flows north moving away from toward the west
and south before cooling and tropics turns left,
sinking over the subtropics. Near toward the east
the surface it is pushed aside by the
sinking air. Some flows back toward The airflow in the lower parts of the circulating cells causes
the equator, replacing the air rising there the winds. If the planet was not spinning, winds would blow
to form a circulating Hadley cell. A similar directly north or south, away from the zones of sinking air
ferrel circulation occurs in the polar regions, and toward regions where warm air is rising. But the Earth’s spin
Cell pushes the airflow off-course. Air moving toward the equator
these tropical and polar cells are linked by
Ferrel cells flowing in the opposite direction. swerves west, while air moving toward the poles swerves east.
This is called the Coriolis effect. It creates the global pattern
of prevailing winds that blow over the oceans.
polar Cell Cool air sinks
over Antarctica