Download Meteorology

Meteorology
Everyday Weather
Atmospheric Structure
• The atmosphere is
made up of four
layers:
–
–
–
–
The Troposphere
The Stratosphere
The Mesosphere
The Thermosphere
• As altitude goes up,
air pressure goes
down
The Troposphere
• Where most weather
occurs (clouds, wind,
precipitation, etc.)
• Extends to 10 km
above the earth’s
surface
• Temperature
decreases as altitude
increases
The Stratosphere
• Contains almost all of
the ozone (O3) in the
atmosphere
• Extends to 50 km
above the earth’s
surface
• Temperature
increases as altitude
increases
The Mesosphere
• Pressure varies from
.01 mb to 1 mb (very
low pressure)
• Extends to 80 km
above the earth’s
surface
• Temperature
decreases as altitude
increases
The Thermosphere
• Thermosphere is the
beginning of the end of
the atmosphere, right
before you reach the
Exosphere, or outer
space
• Extends to over 300 km
above the earth’s surface
• Temperature increases as
altitude increases, but the
molecules are so spread
out that it doesn’t “feel”
warm
Atmospheric Composition
• The Atmosphere is
composed of two
major elements:
– Nitrogen (78%)
– Oxygen (21%)
• And of many other
trace elements
including Helium,
Hydrogen, Carbon
Dioxide, and others
Air Masses
• Four types of air masses:
–
–
–
–
•
•
•
•
•
cP Continental Polar
cT Continental Tropical
mP Maritime Polar
mT Maritime Tropical
Maritime – over water
Continental – over land
Polar – colder
Tropical – warmer
Fronts form when
different air masses meet
• All individual air masses
have constant
temperature and moisture
levels
Fronts
• A front is a meeting
point of two different
air masses
• Four types of Fronts
–
–
–
–
Warm Front
Cold Front
Stationary Front
Occluded Front
• Fronts revolve around
low pressure systems
Warm Fronts
• Warm air mass pushes
and rises over cold air
mass
• Move slower than cold
fronts
• Warm fronts cause light
rain that may last for a
few days
• Clouds form on top of
cold air mass
• Represented on weather
map by red line with
semi-circles
Cold Fronts
• Cold air mass pushes
warm air up
• Moves faster than a warm
front
• Cold fronts cause short,
intense precipitation
• Clouds form on top of
cold air mass
• Represented on weather
map by a blue line with
triangles pointing in
direction of movement
Stationary Fronts
• Created when a cold
front meets a warm
front
• Unmoving front
(stationary)
• Altocumulus clouds
form
• Shown on a weather
map by a warm front
on one side and a
cold front on the other
Occluded Fronts
• Cold front and warm front
around low pressure
system
• Cold front (faster) catches
up with warm front
• Occluded front is warm
front merged with cold
front
• Represented on map by
triangles and semicircles
pointing in same direction
Air Pressure
• Air pressure is how much
the air above a certain
point weighs
• Air weighs 14.7 pounds
on every square inch of
earth at sea level
• Measured in inches of
mercury and milibars
• High and low pressure
zones marked on map by
H and L
• Air flows from high
pressure to low pressure
Isobars
• Isobars show lines of
pressure in milibars
• Lines drawn in
increments of four mb
(960,964,968,972,etc)
• Sea level air pressure
is 1013.25 mb or
29.921 inches of
mercury
Wind
• Wind is caused by
differences in
pressure
• Air flows from high
pressure to low
pressure
• Higher pressure is
usually associated
with better weather
• Lower pressure
equals stormier
weather
Temperature
• Measured in degrees
Fahrenheit, Celsius, and
Kelvin
• Water boils at 100°
Celsius, 212° Fahrenheit
• 0 degrees Kelvin is
Absolute Zero, where
there is no movement in
molecules
• C = 5/9*(F-32)
• F = (9/5*C)+32
• K = C+273
Isotherms
• Isotherms show lines
of temperature
• Lines drawn in
increments of 10°
Fahrenheit
(20,30,40,50,etc.)
Water
• Water comes in three
states: solid (ice),
liquid (water), and gas
(water vapor)
• The amount of water
in a given amount of
air is the “moisture
content”
• Air masses with a
higher moisture
content are lighter
than those with lower
moisture contents
Clouds
Cumulus
• Puffy, cotton ball
cloud
• Associated with fair
weather, but can
develop into
Cumulonimbus,
clouds that cause
storms
Stratus
• Low, gray blanket
• Cause light to
moderate
precipitation
Stratocumulus
• Lumpy, low clouds
• Can cause light
precipitation
Nimbostratus
• Dark, low-level clouds
• Light to moderate
precipitation
Cumulonimbus
• Dark, tall clouds
• Have an “anvil top”
from spreading out
too much vertically
•Cause severe
thunderstorms
Cirrus
• Thin, wispy clouds
• Generally come with
fair weather
Heat Transfer
• 3 types of heat
transfer:
– Conduction
– Convection
– Radiation
Conduction
• Conduction is the
transfer of heat by
direct contact
• For example, if you
are boiling water with
a metal spoon in the
pot, the heat from the
water will transfer into
the spoon
Convection
• Convection is a type
of heat transfer which
only occurs in fluids
(water, air, etc.)
• Hot fluid at the bottom
of the “pan” rises (hot
air balloon) and cold
fluid from the outer
top layer rushes to fill
its place, warming the
cold fluid and cooling
the hot fluid
Radiation
• Radiation is the
transfer of heat
through the air
• For example, roasting
marshmallows uses
radiation to heat up
the marshmallow
Insolation
• Insolation is incoming
solar radiation
• Solar rays that come
in at an angle are
weaker than direct
rays
• Some of it is reflected
off of clouds,
particles, water, etc.
• This reflected energy
is called albedo
Albedo
• Amount of Insolation
which reflects off of a
surface
• For example, deep
snow reflects about
90% of Insolation.
• This number
expressed as a
fraction is the Albedo
(9/10)
Atmospheric
Circulation
Intertropical Convergence Zone
(ITCZ)
• Where tropical
easterlies from the
Subtropical high
zones meet
The Jet Stream
• The Jet Stream is a
large belt of high
altitude winds
• Airplanes fly along the
jet stream to gain a
boost in speed and
save gasoline
• North of the jet
stream is a cold air
mass and south of the
jet stream is a warm
air mass
Sea Breezes
• A sea breeze occurs
during the summer,
when the land is
warmer than the
water. This is due to
the fact that water
heats and cools much
more slowly than land
Land Breeze
• A land breeze occurs
in the winter, when
the land is cooler than
the water.
• A way to remember
the difference
between the breezes
is that a land breeze
blows out from the
land, opposite of a
sea breeze
The Coriolis Effect
• The Coriolis
effect is a
force which
changes
direction of
winds and
objects due
to the
earth’s
rotation
•Causes all winds in Northern Hemisphere
to turn right, and all winds in Southern
Hemisphere to turn left
Planetary Wind Belts
• The wind belts are a
series of high and low
pressure zones which
result in major wind
groups (recall that air
flows from high to low
pressure)
• They include:
– Subtropical high at 30°
– Subpolar low at 60°
– Intertropical
convergence zone
3 Cell Model of Circulation
3 Cell Model of Circulation (cont.)
• The three cell model of circulation is based on
the planetary wind belts and the Coriolis effect.
• It is based on three cells:
– The Polar Cell
– The Ferrel Cell
– The Hadley Cell
Atmospheric Phenomena
Sundogs, Rainbows, Aurora,
Virga, etc.
Sundogs
• Two halos on either
side of the sun
• Light is reflected from
the sun off of ice
crystals in cirrus or
cirrostratus clouds
Rainbows
• Bet you’ve seen this
before…
• Rainbows are caused
by light from the sun
refracting through
water in the air, and
splitting the light into
all of the different
colors in the visible
spectrum
Aurora
• The earth’s magnetic
field (right) is pushed
by the magnetic field
from the sun (solar
wind, bottom). This
action causes the
moving electrons
within the earth’s field
to collide with gas
molecules, which give
off light in an aurora
(top)
Virga
• A virga is a form of
precipitation that
doesn’t reach the
ground. The
precipitation
evaporates
somewhere between
the clouds and the
Earth.