Transcript Air Mass

Weather is....
Weather is the day-to-day state of the
atmosphere, and its short-term
(minutes to weeks) variation
 Weather includes sunshine, rain, cloud
cover, winds, hail, snow, sleet, freezing
rain, flooding, blizzards, ice storms,
thunderstorms, steady rains from a cold
front or warm front, excessive heat,
heat waves and more

Climate is....
statistical weather information that
describes the variation of weather at a
given place for a specified interval
 Climate may include precipitation,
temperature, humidity, sunshine, wind
velocity, phenomena such as fog, frost,
and hail storms over a long period of
time.

Weather vs. Climate in NC
Weather
Climate
Monday morning:
Sunny in the morning...Then
becoming partly sunny.
Highs in the lower 70s. East
winds around 5 mph
North Carolina has a humid,
subtropical climate. Winters are
short and mild, while summers are
usually very sultry; spring and fall
are distinct and refreshing periods
of transition. In most of North
Carolina, temperatures rarely go
above 100°F (38°C) or fall below
10°F (–12°C)
Monday evening:
Partly cloudy. Lows in the
upper 40s. Light and variable
winds...Becoming east
around 5 mph after midnight.
Main points to remember as we
learn about weather:
The sun warms the earth’s surface and
therefore all the air above the surface
 The earth is warmed most at the equator and
least at the poles---why?
 The air above land is warmed more quickly
than air above water.
 Warm air expands and rises, creating an area
of low pressure; cold air is dense and sinks,
creating an area of high pressure

Air Mass
• large body of air that has similar temperature
and humidity properties throughout
• Properties of air masses, however are modified
as they move over areas outside where they
originate
• Source regions = regions where air masses
develop their characteristics
– need large areas with similar characteristic
Air Mass Classification
Air masses have 4 major classifications
• Polar (P)
• Tropical (T)
• continental (c) or maritime (m)
• Arctic (A) - extremely cold air masses
Air Mass Classification
Air masses are classified according to their source
regions:
1.Warm and dry continental tropical
2.Warm and humid maritime tropical
3. Cold and dry continental polar
4. Cold and humid maritime polar
5. Arctic
All five of these can be found in North America
Air Masses
• Air masses are masses of air that have the
same characteristics of the surface over which
it develops
Wind Systems
Air flows from areas of HIGH pressure to areas of
LOW pressure; this creates wind
Winds are named for the direction from which they
flow.
• Easterlies flow from the East to the West
Jet Stream
A high altitude,
narrow, westerly
wind band that
occurs above
large temperature
contrasts and can
flow as fast as
185 km/h.
Coriolis Effect
• Caused by the Earth’s
rotation
• Pulls the wind to the right
in the northern hemisphere
• Pulls the wind to the left in
the southern hemisphere
• Strongest at the Poles
• None at the Equator
Example of Coriolis Effect
http://www.classzone.com/books/earth_science/terc/content/visualiz
ations/es1904/es1904page01.cfm
Air Pressure

Warm air= expanding or rising air=
leaves behind L pressure

Cold Air=sinking air= leaves an area of
H pressure

Air Pressure/Atmospheric Pressure is
measured with a barometer
Wind Movement
Uneven heating of the earth’s
surface causes some areas to
be warmer than others.
 As we know, warm always
follows cold to share it’s
warmth- when this happens
in the atmosphere, wind
happens!

What causes winds?
A wind is a
horizontal
movement of air
from a area of high
pressure to an area
of low pressure
 It is this difference
in pressure that
makes the air
move=wind

Winds are measured
by direction and
speed
 The anemometer is
the tool we use to
measure this
 Wind chill=↑ cooling
the wind causes

Local Winds

The land cools and heats faster than the ocean.
Water holds heat longer than land, and takes longer
to heat or cool.
During the day, the land
SEA BREEZE
gets hotter faster than the
water. The heated air
rises, leaving behind an
area of low pressure.
Wind from the cooler sea
blows in to take the place
of that warmer air. These
happen during the day!
Land Breezes
At night the lands cools off faster than
the sea. Cool air sinks creating an area
of high pressure. Wind blows from the
land to the sea.
STOP
Global Circulation and Wind
Systems
Solar
energy is at its
greatest around the
equator---Why?
Global Winds:

Wind belts:
Horse Latitudes= 30°N and S of
equator =calm winds= worlds
desert areas
Jet Streams= 10km above the
surface blow from the west to the east
Some of the air moves back
towards the equator as it sinks...
Tradewinds:
Where do you think
they got their name?

Who were these winds
particularly important
to?
There was an area that sailors
avoided with their lives...

THE DOLDRUMS... is
the area around the
equator where the
wind completely dies
out... which meant
death as soon as the
fresh water ran out.
Weather Foldable
Warm front
 Cold front
 Occluded front
 Stationary Front

Fronts: the boundary between 2
air masses

Warm Front: warm air slides over
departing cold air- large bands of
precipitation form
This is
the
symbol
on a
map for
a warm
front
Cold Fronts

This is the symbol
for a cold front
Cold air pushes under a warm air mass.
Warm air rises quickly=narrow bands of
violent storms form
Occluded Front

This is the
weather map
symbol for an
occluded front
2 air masses merge and force warm air
between them to rise quickly. Strong
winds and heavy precipitation will occur
Stationary Front

This is the
weather map
symbol for a
stationary front
Warm or cold front stops moving. Light
wind and precipitation may occur across
the front boundary
Reading a weather map

ISOBAR= connects areas of equal
pressure BAR comes from BARometric
pressure
Reading a weather map...

Isotherm: Connects areas of equal
temperature; therm means temperature