Download Weather - Jefferson Township Public Schools

Heating the Atmosphere
Electromagnetic Waves
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The sun is the ultimate source of
energy that creates our weather.
You know that the sun emits light
and heat as well as the ultraviolet
rays that cause a sunburn.
Electromagnetic Waves
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These forms of energy are only a
part of a larger array of energy
called the electromagnetic spectrum.
All radiation, whether X-rays, radio
waves or infrared waves, travel
through the vacuum of space at
300,000 kilometers per second.
Only 7% of the light
energy received by
the earth is visible
light.
Electromagnetic waves are classified
by their
wavelengths;
the distance
from the
crest of one
wave to the
crest of the
next wave.
Heat transfer
Three mechanisms of energy transfer
as heat are
—Conduction
—Convection
—Radiation
All three processes happen
simultaneously in our atmosphere.
These mechanisms work to transfer
energy between Earth’s surface (both
land and water) and the atmosphere.
Heat transfer

Conduction – the movement of heat
from molecule to molecule; through
molecular activity
• Heat flows from the higher temperature
matter to the lower temperature matter
• Metals are good conductors
of heat; air is a poor
conductor of heat.
Heat transfer
Because air is a poor conductor,
conduction is important only
between Earth’s surface and air
directly in contact with the
surface.
For our atmosphere, conduction is
the least important mechanism of
heat transfer.
Heat transfer
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Convection – the movement of heat
by circulation within a substance
Much of the heat transfer that occurs
in the atmosphere is convection
Convection takes place in fluids
where the molecules can move
freely.
The atmosphere behaves like a fluid
Heat transfer

example of convection: a pot of
boiling water
Heat transfer
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Radiation – the release and transfer
of energy in wavelengths of heat
and light through space.
Solar Energy reaches the Earth from
the sun by radiation
There are actually 4 laws that
govern radiation….
1: All objects, at any temperature,
emit radiant energy.
Not only hot objects like the sun,
but colder objects like the Earth
(including it’s polar ice caps)
continuously emit energy.
2. Hotter objects
radiate more
total energy
“per unit area”
than colder
objects do.
3. The hottest
radiating bodies
produce the
shortest
wavelengths of
maximum
radiation

The sun, at 6000C,
radiates at .5
micrometers.
When radiation strikes an
object, there are usually three
different results.
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1. Some energy is absorbed by the
object. When radiant energy is absorbed,
it is converted to heat and causes a
temperature increase.
Like what??
When radiation strikes an
object, there are usually three
different results
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2. Substances such as water and air are
transparent to certain wavelengths of
radiation. These substances transmit the
radiant energy.
In other words – Radiation goes THROUGH
the object
When radiation strikes an
object, there are usually three
different results
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3. Some radiation may bounce off the object
without being absorbed or transmitted.
Thus being scattered

This
scattering is
why the sky
is blue…
… and the sunsets
are often red
(what do you think
is the meaning of
“Red sky at night,
sailors’ delight; red
sky in the morning,
sailors’ take
warning”
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Heat Budget of the Atmosphere
When it reaches the Earth, some is reflected
back to space by clouds, some is absorbed
by the atmosphere, and some is absorbed
at the Earth's surface.
Since the Earth is much cooler than the Sun,
its radiating energy is much weaker (long
wavelength) infrared energy.
Heat energy from the earth can be trapped by
clouds leading to higher temperatures as
compared to nights with clear skies.
The air is not allowed
to cool as much with
cloudy skies.
Under partly cloudy
skies, some heat is
allowed to escape
and some remains
trapped.
Clear skies allow for
the most heat to
escape & cooling to
take place.
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About 50% of solar energy reaches
the surface and is absorbed.
Most of THIS energy is reradiated.
The atmosphere absorbs the longer
wavelengths
Larger molecules, like water vapor
and CO2, absorb the energy
This energy is transformed into
molecular motion – rise in
temperature
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Simplified diagram of the heating of
the atmosphere
Albedo (Al-bee-dough)
The percent of radiation returning from
a surface compared to that which
strikes it
When an object reflects most of the
light that hits it, it looks bright and it
has a high albedo.
When an object absorbs most of the
light that hits it, it looks dark. Dark
objects have low albedos.
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Clouds’ albedo is near 60%
Snow’s albedo is up to 95 percent
Water’s albedo is (on average) about
10%
Average albedo for earth and clouds
is about 30%
Conditions of the Air
Temperature – amount of hotness or coldness
relative to something else
•Thermometer – an instrument that measures
relative hotness or coldness
•Dew Point temperature – The temperature at
which air becomes saturated
•Isotherm – a line connecting places with equal
temperature on a weather map
Temperature scales:
1°C = 1.8°F or
1°F = 5/9 ° C
Celsius to Fahrenheit and
Fahrenheit to Celsius
Formula
°C x 9/5 + 32 = °F
(°F - 32) x 5/9 = °C
For Example
Convert 37°C to Fahrenheit.
37°C x 9/5 + 32 = 98.6°F
OR
37°C x 9 + 32 = 98.6°F
5
Convert 98.6°F to Celsius.
(98.6°F - 32) x 5/9 = 37°C
OR
(98.6°F - 32) x 5 = 37°C
9
Conditions of the Air (cont.)
Air pressure - the downward pressure exerted by
the weight of the overlying atmosphere or the
“weight” of the atmosphere per unit AREA.
 Barometer – an instrument used to measure air
pressure
 Measured in inches of
mercury in a column
 Or millibars (metric
conversion)
 Average air pressure
at sea level is 1013 millibars
What do you notice about the
relationship between air pressure
and volume?
What do you notice about the
relationship between air pressure
and temperature?
What do you notice about the
relationship between volume
and temperature?
Pressure depicted on a weather
map
Isobars –
lines connecting
points of
equal
pressure
Isobars on the ‘vertical’
Note: the density of molecules close to the surface
Measurement of the
Atmosphere

The condition(s)
of the
atmosphere is
measured by the
radiosonde
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A radiosonde is a small instrument
package tethered to a weather
balloon.
• take a vertical profile of the atmosphere
as the balloon ascends to altitudes up to
115,000 feet.
• the data is relayed by radio transmitter
to a computer at the surface
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Launch
of a
weather
balloon
off an
aircraft
carrier
photo shows the weather balloon
bursting at 99,712 feet
http://www.brothers-brick.com/2008/08/06/mindstorms-nxt-fans-launch-lego-into-space-via-weather-balloon/
Synoptic Map
Station models – group of symbols
depicting weather conditions
Isobar – line of equal pressure
a. show locations of High or Low
pressures
b. close lines mean strong winds
c. lines far apart mean gentle winds
Station Model
how
meteorologists
can put a lot of
information in a
small area
Water in the atmosphere
Water Vapor
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Humidity – the amount of water
vapor in the air
Relative humidity – the actual
amount of water vapor in the air
compared to the greatest amount
the air can hold
Water in the atmosphere
Water Vapor
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Saturated – to be completely filled
with water vapor
Psychrometer – an instrument to
measure relative humidity
Hygrometer – an instrument used to
measure the air’s humidity
Precipitation
water or ice that condenses in the air
and falls to the ground as:
 Rain- liquid water that falls to the ground
 Snow - ice crystal flakes; water vapor in
the atmosphere that froze into ice crystals
and falls to the ground in the form of
flakes
 Sleet -partially melted grains of ice
 Hail - pellets made of layers of ice and
snow
 Freezing rain – rain that freezes into ice as
it hits the ground
Weather Advisories
Weather WATCH – predictions about
approaching severe weather
Weather WARNING – specific severe
weather conditions have been
actually observed by a person or
verified by a computer
http://www.sleepingdogstudios.com/Network/Earth%20Science/ES_17.2_files/frame.htm