Transcript Section 6.1

Water and Weather
Chapter Six: Weather and
Climate
• 6.1 Introduction to Weather
• 6.2 Weather Patterns
• 6.3 Climates and Biomes
Investigation 6A
Observing the Weather
• How can you use weather data to make
predictions?
6.1 Introduction to Weather
•
Weather is a term
that describes the
condition of the
atmosphere in terms
of temperature, wind,
and atmospheric
pressure.
6.1 Temperature
•
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Heated air near a hot
surface is less dense than
the colder air above it.
The heated air rises, forcing
the colder air to move aside
and sink toward the ground.
Then this colder air is
warmed by the surface, and
it rises.
Wind is created.
6.1 Pressure
1.
2.
3.
4.
5.
When warm air rises from Earth’s
surface, an area of low pressure is
created.
This lower-pressure area draws in
air from surrounding higherpressure areas.
Eventually the warm air that rose
from the surface cools and
becomes more dense.
Dense, cool air sinks back to the
surface causing an area of high
pressure.
This new high pressure may
become the source of more wind.
6.1 Convection in the atmosphere
• Convection near coastlines causes sea
breezes during the day and land breezes
at night.
6.1 Convection in the atmosphere
• A small upward flow
of warm air is called
a thermal.
• Pilots of sailplanes
(which lack engines)
fly by riding the
thermals.
6.1 Convection cells
• The combination of
global convection
and Earth’s rotation
sets up a series of
wind patterns called
convection cells.
6.1 Coriolis effect
• The bending of currents of air due to the
Earth’s rotation is called the Coriolis effect.
6.1 Air and water vapor
•
Three important global
wind patterns exist in
each hemisphere:
– Trade winds
– Prevailing westerlies
– Polar easterlies
6.1 Air and water vapor
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Water in gas form is
called water vapor.
Like a soggy sponge, air
reaches a point and can’t
hold anymore vapor.
The vapor turns back into
liquid and form droplets.
Use these pictures to explain
how the cycle can continue.
6.1 Relative Humidity
• Relative humidity is a measure of how
much water vapor an air mass contains.