Transcript Under Pressure - Galena Park ISD Moodle

Under Pressure
• As we know, the air in the atmosphere is made up of a
number of gases. These gases press down on the
Earth’s surface, exerting a force that we call
atmospheric pressure or air pressure. Although we are
usually unaware of this pressure, it actually presses
down very hard – roughly equivalent to the force of an
elephant balancing on a desk!
• Each layer of air presses down on the layers below, and
so the greatest pressure is at ground level where we
have the maximum amount of air above.
• In the stratosphere air pressure decreases until it
reaches about zero.
Changes in Air Pressure
Changes in air pressure are caused by the difference in air temperature
above the earth. Land masses and areas of water change the temperature
of the air above them. These changes create wind and cause pressure
patterns to develop. The wind moves these pressure patterns that change
as they pass over mountains, oceans, and other areas.
The Sun: Heat Energy and the
Atmosphere
Radiant energy from the sun is transformed into heat by absorption at the earth’s
surface.
The angle of the sun’s rays affect the
heating of Earth’s surface.
• The uneven distribution of heat energy in the
atmosphere is the cause of weather.
Wind
•
Changes in air pressure bring changes in the
weather and make winds blow.
• Air usually moves from areas of high pressure to
areas of low pressure, and this produces winds. This
can be easily remembered with the phrase:
"Winds blow from high to low!"
Wind Facts:
• Winds move from high to low pressure areas.
• High pressure is associated with cold air, low pressure with warm air.
• Warm air rises because it is less dense than cold air
• Both local and global winds are caused by differences in air pressure
due to unequal heating of the air.
Air Circulation Pattern
,
• When air is heated, it becomes lighter (less dense) than the surrounding air.
Therefore, warm air rises.
• Cool air is heavier (more dense), so it tends to sink. As air rises or falls, the
surrounding air rushes in to replace it, causing air to circulate. This circulation,
brings about changes in the weather.
• The heating of Earth's surface depends on the nature of the surface
Local Winds
Sea Breeze, Land Breeze, and Monsoon
Land Breeze
Sea Breeze
• Occur on warm sunny days
• Occur at night and on cool days
• Air over the land heats faster than
the air over the cool ocean
• Air over water maintains an even
temperature
• Warmer air rises
• Air over land cools faster
• Cool air flows in under it to fill the
area over the land
• Cooler air flows from the land out
under the warmer ocean air
• This air warms and the cycle
• This air warms and the cycle continues
continues
Global Winds
Coriolis Force (effect)
The original circulation of air caused
by convection is in a north –south
direction. But because the earth
turns toward the east, all winds veer
from this north-south direction.
The Coriolis force is caused by the
differences in velocity of rotation at
different latitudes. At the equator
the velocity of rotation is at its
maximum (1,000 mi/hr). At the
poles the velocity of rotation is at its
minimum (0mi/hr). The velocity of
rotation gradually decreases from
the equator to the poles.
• Rotation of the
earth, distribution
of land and water
areas, and the
exchange of heat
between warm and
cold areas causes
the circulation
patterns of the
atmosphere.
Major Wind Systems
Trade Winds or Easterlies - An area of calm
found at the equator.
• When warm air from the equator rises, it
cools, and flows back toward the
equator. It appears to flow to the west
because of the Coriolis Effect.
Prevailing Westerlies - When air moves
toward the poles, it flows from west to
east.
• clouds, rain , or snow may occur when
highs and lows overtake one another
Polar Easterlies - Air over the poles cools
and sinks back down, it eventually
returns to the equator.
The Jet Stream
• The Polar Front at
the Tropopause
• Recall that winds
aloft are faster than
surface winds
Climate
• Climate is the general character of the weather that prevails in an area
from season to season and from year to year. It can be thought of as the
average weather of an area over a long period of time.
• Factors that combine to produce different climates:
• latitude
• altitude
• Large bodies of water
• Mountain barriers
Air masses are classified based on their
and amount of
Air masses get their characteristics based
on
The abbreviations used to classify air masses
use the following letters: c, m, T, P, and A.
For each letter, describe its property:
Word
c
continental
m maritime
T Tropical
P Polar
A Arctic
Means
dry
moist
warm
cold
very cold
warm and moist
cold and dry