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Meteorology
Unit 6
Energy Exchange in the Atmosphere
Weather
________the state of the atmosphere at a
given time and place.
Meteorology
____________the study of the entire
atmosphere including its weather.
Atmospheric variables- temperature, wind,
humidity, pressure, and atmospheric
transparency
A. Energy Transfer in the Atmosphere
1. _____________-the
transfer of energy by movements of
Convection
liquids and gases (fluids)
-movements are caused by differences in densities in the fluids.
convection currents
-heat is carried by ____________________
convection cell
(______________)
Water becomes
warmer, less
dense, and rises
Water becomes
colder, more dense,
and sinks
conduction
2. _______________transferring heat by
touching an object
i.e. pan on stove, air on radiator, air on earth’s
surface
radiation the transfer of electromagnetic
3. ________energy through space.
-heat emanating from a body as wavelengths of
energy
B. Heat Balance
• Energy enters and leaves Earth by radiation.
insolation
___________-incoming
solar radiation
Energy that Reaches the Atmosphere
- 30% reflected back into space
- 70% absorbed
- 19% absorbed by water vapor, clouds, ozone, and dust
- 51% absorbed by earth’s surface
- 21% of energy is radiated back by surface
-30% of energy is transferred to atmosphere by
conduction and convection
The Greenhouse Effect
•
Short wavelengths of energy from the sun
pass through the gases of the atmosphere but
the longer wavelength radiation
given off by the surface is reflected back to
the surface
• The burning of fossil fuels is increasing the
greenhouse gases
Greenhouse Gases
1) Carbon Dioxide
2) Methane
3) Water Vapor
Electromagnetic Spectrum
p. 14 in the Reference Tables
Greenhouse Effect
long wave,
infrared radiation
is released from
surface
C. Factors Affecting Atmospheric Variables
1) Temperature-measure of the energy of molecules
a. Latitude- higher latitude -lower temperatures
b. Altitude- higher altitude -lower temperatures
c. Closeness to large bodies of water - less
fluctuation in temperature of nearby land areas
*Due to specific heat capacity- water has a high
specific heat, meaning it heats up and cools down
more slowly than land.
2. moisture- liquid (water droplets), solid ice and
snow), gas (water vapor)
a. temperature –the higher it is, the more moisture the air can
hold
b. capacity – the amount of water vapor the air can hold
c. saturated – the air contains all the water vapor it can at that
temperature
d. dewpoint temperature –temperature at which
condensation occurs
e. absolute humidity – the amount of water vapor actually
present in the air
f. relative humidity – a comparison between the amount of
moisture in the air and the amount the air can hold.
-if the air is “half full” of water, the relative humidity is 50%
When is Relative
When is Relative Humidity 100%? When is Relative
Humidity highest?
Humidity lowest?
Notice when the high and low temperatures
are for the day. Why?
Sling Psychrometer
-________________instrument used to find
Psychrometer
dewpoint.
-two thermometers (one “wet”, one “dry”); as
water evaporates from the wet thermometer,
the temperature drops. The drier the air, the
more it evaporates, and the more it drops.
3. Pressure
Air Pressure- the force, or weight, of the air pushing
down on a unit surface area
atmospheric pressure
-also called ______________________or
____________________.
barometric
pressure
density
a. ___________the greater it is, the higher the
pressure.
b. ______________the greater it is, the less the
temperature
density and pressure.
Aneroid Barometer
Mercury Barometer
Barometer
________________instrument used to
measure atmospheric
pressure
Isobars lines on
________weather maps joining
places with equal air
pressure
As air temperature
increases, air pressure
decreases.
Inverse Relationship
c. moisture- the more moisture in the air, the
lower
the atmospheric pressure.
d. altitude- as altitude increases, the density and
pressure of the air decrease
D. Air Movement
winds large horizontal movements of air near
1. _______the Earth’s surface
breezes local horizontal movements of air
2. _________currents vertical air movements
3. _________Pressure gradient- the rate of change in pressure between two
locations.
Steep pressure gradient- isobars are close together
and winds are strong
Gentle pressure gradient- isobars are far apart and winds are
light
Land and Sea Breezes
-occur because land
heats up and cools off
faster than water
-sea breeze- onshore breeze
-land breeze- offshore breeze
Land and Sea Breeze Animation
NOAA Website for Diagrams
Air always moves from high to low pressure
Convection Cells
-occur because gravity pulls cool, dense air toward the Earth’s
surface, forcing warmer, less dense air to rise.
L
H
-zones of divergence
- high pressure regions where air
descends and spreads out (dry).
-zones of convergence - low pressure regions where air
comes together and rises (wet)
Planetary Winds
-If the earth did not rotate, air would rise at the equator and
sink at the poles, creating a large convection cell.
-Since the earth does rotate, winds are modified by the Coriolis
Effect. They are deflected to the right in the Northern
Hemisphere and to the left in the Southern Hemisphere
(causes wind belts and jet streams).
Major Wind Belts
• North and South Poles- Polar Highs
• 60°N to 90°N, 60°S to 90°S- Polar Easterlies
• 30°N to 60°N, 30°S to 60°S- Prevailing
Westerlies
• 30°S and 30°N- Horse Latitudes
• 0° to 30°N- Northeast Trades
• 0° to 30°S - Southeast Trades
• Equator- Doldrums and Intertropical
Convergence Zone (ITCZ)
Subpolar High
Prevailing Westerlies
Polar Easterlies
Northeast
Trades
Horse
Latitudes
Doldrums
Southeast
Trades
Polar Easterlies
Subpolar High
Prevailing Westerlies
Jet Streams
•
•
•
•
•
•
•
Bands of swiftly moving winds
Move in an west to east direction
Found near the top of the troposphere
Thousands of kilometers long
Hundreds of kilometers wide
One kilometer from top to bottom
Our weather is affected by a polar jet stream,
which is stronger than the tropical jet stream
Reference Tables p. 14
E. Clouds and Precipitation
Condensation- process by which gaseous water vapor changes to
liquid
-must condense onto a surface
-occurs when the air is saturated
Condensation nuclei- particles in the air such as dust or salt
that water condenses on
Deposition- when water vapor changes directly into a solid (ice
or snow).
-temperature must be below zero °C
dew condensation of water onto the ground
______frost
______-deposition
of water onto the ground
Clouds- collections of tiny water droplets or ice crystals
suspended in the atmopshere
-Air rises vertically, expands, and cools. If it cools to the
dewpoint temperature, clouds form.
orographic lifting
________________-occurs
when mountains act as barriers to
the flow of air, forcing it to rise to get to the other side
frontal
wedging occurs when warm, lighter air rises over cool air
____________-
Cloud Types
1.
2.
3.
4.
5.
_______________low rain clouds
nimbostratus
_______________-thunderclouds
cumulonimbus
___________fair weather (heap) clouds
cumulus
cirrus
___________fair weather (high, wispy) clouds
____fog cloud resting on the Earth’s surface
Precipitation- the falling of liquid or solid water from
clouds
rain
1. _______large falling drops of water
drizzle
2. _______fine falling drops of water
sleet
3. _______rain that freezes as it forms
4. _______falling ice crystals
snow
5. _______when water droplets freeze and start to
hail
fall they collect water and are forced upward,
freeze again, fall, collect water, and are forced
upward, etc.
Seeding- placing condensation nuclei into the
atmosphere where there is some available water
vapor
F. Weather Maps
Station Models
Isobars- isolines connecting points of equal
pressure
Isotherms- isolines connecting points of equal
temperature
Pressure gradient- high (steep) where isobars
are close together ; this produces strong
winds
front
_______the boundary between two different
air masses
-moving in the direction of the triangles or
half-circles
Weather Map of the United States
Cold, Dry
Air
H
L
Warm,
Moist Air
Air Masses
Air mass- huge body of air in the troposphere having
similar characteristics
-characteristics depend upon their geographic region of
origin (source region).
maritime
1. __________(m)air masses that develop over
water (moist)
2. continental
__________(c)- air masses that develop over land
(dry)
3. polar
_________(P)- air masses that develop over higher
latitudes (cool)
4. tropical
_________(T)- air masses that develop over lower
latitudes (warm)
Jet Stream- narrow, fast moving current of air that
flows just below the tropopause
Air flows from west to east across the United
States.
cyclone (low)- low-pressure air-mass with the winds
moving counter clockwise toward its center
-often produce rain
anticyclone
____________(high)high pressure air-mass with
winds moving in a clockwise direction away from its
center
-cool, clear weather
Fronts
-the boundary (interface) between two air masses
-usually unstable (meaning they have big differences
between temperature and moisture)
-often produce clouds, strong winds, precipitation,
temperature and pressure changes
-the half-circles and triangles point in the direction the
air-masses and front are moving.
1. warm
__________fronts occur when warm air meets
and rises over cold air on the ground
-long gentle slopes (1000km)
-cause extended periods of precipitation
mT
cP
2. cold
__________fronts occur when cold air meets and
pushes out warmer air
-short, steep slopes
-move faster than warm fronts
-cumulonimbus clouds- violent thunderstorms
-precipitation falls for a very short period of
time
-abrupt weather change, winds shift from
southerly to northerly
Cold Front
Cumulonimbus
mT
cPcP
3. ________________Occluded fronts occur when a faster
moving cold front overtakes a slower moving
warm front and lifts the warmer air between
the two fronts off the ground
stationary front occurs when a warm air4. ______________mass and a cold air-mass are side-by-side,
with neither air mass moving.
-gentle slope, weather similar to that of a
warm front
Mid-latitude Cyclones
-Begins when cold air pushes down from the
north, changing a stationary front into a pair
of warm and cold fronts moving around a low
pressure center.
-As the low moves eastward, the cold front
overtakes the slower-moving warm front,
producing an occluded front
Cyclone Animation
AC takes 12-24 hours
D- 3-4 days
-
Cyclones are “driven” by the heat energy released
by condensation (latent heat), causing the low
pressure to become even lower, thereby
strengthening the winds.
- In summer, cyclones move about 800 km a day,
while in winter they move about 1,100 km a day. A
mid-latitude cyclone may cover as much as onehalf of the entire continental United States at one
time.
1. Warm front would approach and bring long, steady
rainfall
2. Then you would have warm temperatures, high humidity
3. The cold front would arrive with thunderstorms
City 1
-Temperature
decreasing
-Pressure
increasing
-Short, heavy
precipitation
-Thunderstorms
1
1
2
3
2
3
City 2
-Warm temperature
-Pressure steady
-Humid, but no precipitation
City 3
-Temperature
increasing
-Pressure
decreasing
-Long-lasting,
light
precipitation
Predictions
1. Decreasing air pressurePrecipitation, higher humidity,
winds, building cloud cover
2. Increasing air pressure-
Clear skies, dry air, lower
humidity, calm