Transcript Weather Factors

• Sun’s energy travels in
electromagnetic waves
• Visible light (ROYGBIV)
– Infrared light (IR or heat) longlazy waves
– Ultraviolet light
(UV) short-zippy
waves
Electromagnetic Spectrum
Energy in the Atmosphere
• Radiation goes
through the
atmosphere some
is ABSORBED
• Some radiation is
REFLECTED
• and SCATTERED
• CO2 and water
vapor absorb
some IR.
• Ozone absorbs
most of the UV.
• Clouds, dust and
other gases also
absorb radiation.
Why is the sky blue?
• As light reflects, blue and
violet get scattered
more…that’s why the sky is
blue in the daytime.
Why is the sky red?
• At sunrise or set, radiation
passes through a greater
thickness of atmosphere…so
the blue and violet
wavelengths get absorbed
and the orange-red
wavelengths are more visible.
Energy at the
Earth’s Surface
• Some radiation that
reaches earth is
reflected back.
• Some radiation that reaches earth is
absorbed by land and water and is
changed into heat.
• This infrared radiation is then
radiated back out into the
atmosphere.
• The atmosphere acts like a “blanket”
holding in the reflected radiation
from the earth.
• It is a natural good process…but too
much pollution may lead to Global
Warming.
Heat Transfer
• Gases are
constantly
moving…the
faster they move,
the more energy
they have.
• Temperature is
the AVERAGE
amount of energy
of motion of each
molecule.
Measuring Temperature
• We use a
thermometer and
the metric units
are in degrees
Celsius
• The movement of energy from a
hotter object to a cooler object
is called heat.
• There are 3 types of heat
transfer:
– Radiation
– Convection
– Conduction
• Direct transfer of
energy by waves through
empty space.
• Direct transfer of heat
from one substance to
another substance that it is
touching.
• Gases do not conduct heat
well.
• In gases or liquids,
molecules that
have more heat are
less dense and
therefore rise.
• Molecules that are
more dense sink.
• As molecules move,
they take their
heat with them.
• Only the first few
meters next to the
earth are heated by
conduction.
• Radiant energy from
both the sun and the
earth heat the
troposphere.
• Convection is MOST
important in weather!
What Causes Wind?
• Differences in air pressure
• Air moves from areas of high
pressure to areas of low
pressure
Measuring Wind
• Wind is measured with an
ANEMOMETER
• A speedometer
determines
the speed of
the cups turning
Wind Direction
• Wind direction is
determined by a
WIND VANE or
WIND SOCK.
• The name of the wind
tells you the
direction the
wind is coming
FROM.
• Winds that blow over short
distances
• Caused by unequal heating of Earth’s
surface within a small area
• Often occurs near large bodies of
water
• It takes more energy to warm water
than land, so land heats more during
the day.
• The warmer air over land expands,
rises creating a low pressure area.
• Wind blows from higher pressure
over the water onto the land.
• At night, the land cools more
quickly than the water.
• The air over water is warmer
and rises and cooler air over
land moves from land to sea.
• A large sea breeze blows inland all
summer, day and night carrying
heavy rain.
• In the winter, the land cools and a
land breeze blows steadily.
• Monsoons are important to rice
farmers.
• Winds that blow
steadily from
specific
directions over
long distances
• Created by
unequal heating
of Earth’s
surface
Most direct sunlight is at the
poles
• Temperature differences between
the equator and the poles cause
huge convection currents.
• Warm air rises at the equator and
sinks at the poles producing global
winds.
The Coriolis Effect
• If the Earth did not
rotate, wind would
blow in straight lines
• Since the Earth
rotates, it causes
winds to curve
toward the right
• South winds turn to
the southwest
• North winds turn to
the northeast
• These factors combine to produce
patterns of windy and calm areas of
the globe.
• The major wind belts are
– Trade winds
– Prevailing westerilies
– Polar easterlies
• The major calm areas are
– Doldrums
– Horse latitudes
Name that Wind
Polar Easterlies
Prevailing Westerlies
Horse Latitudes
Trade Winds
Doldrums
Trade Winds
Horse Latitudes
Prevailing Westerlies
Polar Easterlies
• 10 km above Earth’s surface are
bands of high-speed winds
• Hundreds of km wide, but only a few
km deep
• Blow from west to east at about
200-400 km per hour
• Help airplanes that travel west to
east
Water in Atmosphere
• Water cycle
• Humidity is the measure of the
amount of water vapor in the air.
Relative Humidity
• The percentage of water vapor in
the air compared to the maximum
amount the air could hold.
• Depends on temperature!
Measuring Relative
Humidity
• Measured with
a
psychrometer
• Use a table to
figure out the
%
How does it work?
–The dry bulb tells the temperature
–The wet bulb cools depending on the
humidity in the air
•If it is very wet, the water will not
evaporate much…the temperature of
the wet bulb is close to the dry
•If it is very dry, the water will
evaporate a lot…the temperature of
the wet bulb will drop lower than the
dry
How Clouds Form
• Condensation
– Water vapor in the
air becomes liquid
water or ice crystals
– As air cools, the
amount of water it
can hold decreases
– Water molecules
change to liquid and
stick to tiny solid
particles in the air
Dew Point
• The
temperature
at which
condensation
begins
• Air cools because it
– Is warm near the ground, is less dense
and then rises, expands and COOLS
– Wind can push warm air upwards to cool
and form clouds
Types of Clouds
Cumulus
Cirrus
Stratus
Cumulus
• Means heap or mass
• Look like fluffy, cotton piles
• Cumulonimbus clouds (nimbus means
dark) produce thunderstorms
•
•
•
•
•
Stratus
Flat layers
Means layers
Often cover the sky
Fog when low to the ground
May produce rain or snow
Cirrus Clouds
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•
•
•
Wispy, feathery clouds
High altitudes
Mostly made of ice crystals
No rain or snow
• Water that comes from some clouds
• Cloud droplets must become large and
heavy enough to fall through the air as
raindrops which may freeze
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–
–
Rain
Sleet
Snow
Hail
Freezing rain
Measuring Precipitation
• For rain, use a rain
gauge
•For snow, use a ruler or melt the
snow and use a rain gauge for the
water (more accurate)
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Quiz
Energy from the sun travels to the
Earth how?
Rising warm air transports heat energy
by_____.
A psychrometer is used to measure
___________.
Clouds form because water vapor in the
air __________.
Rain, sleet, snow, and hail are all forms
of ______________________.
6. In what form of radiation is MOST
of the energy from the sun?
7. The process by which gases hold
heat from the atmosphere is called
what?
8. Water molecules escape into the
atmosphere in the process called
what?
9. The instrument used to measure
the speed of wind is called a ____.
10. Clouds that cause thunderstorms
are _____________.
11. Clouds that form near the ground
are called _______.
12. What form of heat energy is most
important to the troposphere?
13. What causes wind to move from the
equator to the poles?
14. What is the Coriolus Effect?
15. How do high altitude clouds usually
form?
16. Why is the sky blue?