Meteorology
(Weather)
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Follow along in your notes packet…
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http://www.youtube.com/watch?v=FMagDRCp
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http://www.youtube.com/watch?v=tkK4_F0VK
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Our atmosphere has 3 states of water:
1. Ice
2. Water
3. Water Vapor
Changing Forms of Water
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Water changes from one phase to another as
heat energy is either absorbed or released.
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We call this heat energy latent heat
Most water enters our atmosphere through
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Evaporation
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The process in which a solid changes directly
into a gas is Sublimation
Changing Forms of Water
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Water Vapor in the atmosphere, known as
humidity, is controlled by rates of
evaporation and condensation
Temperature often controls the rate of
evaporation, where as the rate of condensation
is determined by vapor pressure
When the rate of evaporation and condensation
are in equilibrium, the air is “saturated”
Humidity
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Absolute Humidity is the mass of water
vapor contained in a given volume of air (the
actual amount of water vapor in the air)
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Relative Humidity is a ratio of actual water
vapor content of the air to the amount of water
vapor needed to reach saturation
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We use a Psychrometer to measure humidity
Video
Relative & Absolute
Humidity
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Air moves from areas of high pressure to low
pressure
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The Coriolis Effect occurs when winds are
deflected by Earth’s rotation
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Air masses are large bodies of air throughout
which temperature and moisture content are
similar
How Air Moves
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Air masses are classified according to their
source regions, which are determined by the
temperature and humidity of the air masses
Cold Air Masses: Polar areas
Warm Air Masses: Tropical areas
Masses formed over oceans: Maritime (moist)
Masses formed over land: Continental (dry)
Types of Air Masses
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A cool air mass is dense and won’t mix with a
less dense and warm air mass- a boundary
called a front forms between the masses
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Video
Types of Fronts
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Cold Front: a cold air mass overtakes a warm
air mass. Cold air lifts the warm air
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Storms formed from a cold front are short-lived
and sometimes violent
If it is a slow moving cold front, the storm may
be weak with light precipitation
Types of Fronts
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Warm Front: a warm air mass overtakes a
cold air mass
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Generally produces precipitation over a large
area and may sometimes cause violent weather
Types of Fronts
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Stationary Front: air masses move very
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slowly or not at all
Weather produced is similar to a warm front
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Occluded Front : when a fast moving cold
front overtakes a warm front and lifts the warm
air off the ground completely
Types of Fronts
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Thunderstorms produce thunder and lightning.
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Clouds discharge electricity in the form of
lightning.
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The upper part of the cloud carried a positive
charge, the lower part carries the negative
charge.
Lighting is the huge spark that travels within
the cloud or between the cloud and ground to
equalize the electrical charges
Severe Weather:
Thunderstorms
Thunderstorms have 3 stages:
 1. Cumulus Stage
 2. Mature Stage
 3. Dissipating Stage
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Severe Weather:
Thunderstorms
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Hurricanes: severe storm that forms over
tropical oceans and whose strong winds of
more than 120 km/h spiral in toward the
intensely low pressure storm center
Most destructive storms on Earth
Cause rising in the sea levels with large waves
called storm surge
Severe Weather:
Hurricanes
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To rate a hurricane we use the Saffir-Simpson
Scale: 5 categories based on central pressure,
wind speed, and storm surge.
Category 1: least damage
Category 5: most damage
Hurricanes begin over warm water….how would
Global Climate Change affect this?
Severe Weather:
Hurricanes
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Shortest lived severe storms, destructive,
rotating column of air that has very high wind
speeds and that may be visible as a funnelshaped cloud
Forms when a thunderstorm meets highaltitude, horizontal winds which cause the
rising air in the thunderstorm to rotate. A storm
cloud may develop a narrow, funnel-shaped,
rapidly spinning extension that reaches
downward
Severe Weather:
Tornadoes
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To measure and indicate temperature we use a
Thermometer
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For changes in air pressure affect air masses at
certain locations or atmospheric pressure we
use a Barometer
Wind speed is measured with an
Anemometer
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Wind directed is measure with a Wind Vane
Radar, weather satellites and computers are useful
as well
Weather Instruments
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Meteorologists and weather stations collect
data and transfer it onto weather maps.
So that everyone around the world can
understand they use symbols and colors
A cluster of weather symbols are called a
station model: pattern of symbols that
represent the weather at a particular observing
station and is transferred onto a weather map
Forecasting the Weather
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Isotherms: lines that connect points of equal
temperature (think: thermometer)
Isobars: lines that connect points of equal
atmospheric pressure (think: barometer)
Centers marked with an “H” represent high
pressure; “L” is for low pressure
Areas with precipitation are marked with
colors or symbols
Plotting Temp & Pressure
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Doppler Radar & Satellite Images can tell
us about intensity and precipitationso that
meteorologists can create weather models
 Types:
 Daily Forecasts: predict weather for 48 hrs
Extended Forecast: 3-5 days
 Long-Range Forecast: more than 7 days
 Watch: conditions are ideal for severe weather
 Warning: severe weather has been spotted OR
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is predicted within 24 hours
Weather Forecasts
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Weather conditions for an area over a long
period of time is Climate
Different latitudes receive different amounts of
solar energy
The higher the latitude, the smaller the angle
at which the Sun’s rays hit the Earth and the
smaller the amount of solar energy received
by the area
The tilt of Earth’s axis is also a factor
Climate
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Topography: surface features of the land can
control the flow of air through a region
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Rain Shadow: moving air mass encounters a
mountain range, the air mass rises, cools and
loses most of its moisture through
precipitation. The air that flows down the other
side is usually warm and dry.
Warm winds that flows down the eastern
slopes of the Rocky Mountains are Chinooks
Topography
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Tropical Climates: high temperatures and
heavy precipitation during at least part of the
year
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Middle- Latitude Climates: has an average
maximum temperature below 18 degrees C in
the coldest month and an average minimum
temperature above 10 degrees C in the
warmest month
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Tropical Desert Climates: dry climates that
receive less than 40 cm of precipitation a year
Climate Zones
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Mediterranean Climate: mild climate that
has a small temperature range between
summer and winter
 Tundra Climate: smaller annual temperature
range than subarctic but has a colder climate
 Polar Icecap: much of the land and ocean
covered in thick sheets of ice, average temp
never rises above freezing
 Large bodies of water, such as lakes, can
influence local climates as well as precipitation
Climate Zones