Weather Notes
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The earth is heated unevenly by the sun.
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There are three key reasons why:
1. The tilt of the Earth on its axis- the sun hits the earth at different angles
2. The shape of the earth- also because the sun hits the earth at different angles and spreads out the
energy as the suns rays moves away from the equator
3. the composition of the earth- land heats and cools quicker than water, and different materials heat at
different rates
***The overall MAIN reason is because the sun’s rays hit different parts of the earth at different angles
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Wind is caused by the uneven heating of the earth
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Properties of hot air: low density, low pressure, it rises, higher temperature and it holds more moisture than
cold air
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Properties of cold air: high density, high pressure, it sinks, lower temperature and it doesn’t hold much
moisture
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Air Masses are large bodies of air that have nearly the same temperature, humidity, and air pressure
throughout the entire air mass
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Air masses have the same or similar properties as the place on the earth over which they formed. For
example, if an air mass formed off of the coast of south Florida, it would be a warm and wet or moist air mass
because the coast of Florida is warm and wet.
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There are four types of air masses
1. Maritime Tropical- formed near or over a body of water in an area that is warm
2. Maritime Polar- formed near or over a body of water in an area that is cold
3. Continental Tropical- formed over land in an area that is warm
4. Continental Polar- formed over land in an area that is cold
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Air masses are responsible for day to day weather changes
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Wind is air in motion moving horizontally
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Wind always blows from high pressure to low pressure
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The tool or instrument we use to measure air pressure is called a barometer
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The tool or instrument we use to measure wind speed is called an anemometer
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Wind blowing into a low pressure system rises in a counterclockwise direction; this is called a cyclone
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Wind blowing out of a high pressure area blows clockwise and is sinking; this is called an anticyclone
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Fronts- boundaries between two air masses of different density, moisture, or temperature.
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There are four types of fronts: cold front, warm front, occluded front, and stationary front
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Cold Front- A cold air mass moves in on a warm air mass, and forces warm moist air up. This usually
causes brief (short) thunderstorms
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Warm Front- warm air mass gently glides or rises over a colder air mass, and this normally causes rain for
many hours.
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Occluded Front- this is when a very cold air mass moves in on a cold air mass, and traps moist air between
them. This causes long periods of precipitation
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Stationary Front-A cold air mass meets a very large warm air mass, and they battle for a very long time
staying in the same spot. This causes extremely long periods of rain
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Below are the symbols used to identify the different types of fronts.
Number 1 is the symbol for a cold front
Number 2 is the symbol for a warm front
Number 3 is the symbol for a stationary front
Number 4 is the symbol for a occluded front
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An atmosphere is a protective layer of gasses that surrounds a planet
The earth’s atmosphere has 5 layers
The names of the layers in order starting from the lowest layer are: troposphere, stratosphere, mesosphere,
thermosphere, exosphere
All of the names have the suffix “sphere.” This is because each layer surrounds the earth
Troposphere- starts at earth’s surface and goes up about 12km; we live in this layer, and this is where weather
happens (clouds, precipitation, etc); most commercial aircraft fly in this layer. The temperature and air pressure
both decrease as you go higher into the troposphere
The most abundant gasses in our atmosphere are nitrogen (78%) and oxygen (21%); most of the gasses are
located in the troposphere
Rain Shadow is an effect that happens when moist air is blown towards mountains. The side where the wind hits
the mountain forces the air up like a ramp, and causes it to form clouds and rain. This side is called the
windward side. On the other side of the mountain, all the moisture is gone, so virtually no rain happens, and it
becomes a desert like condition. This side is the leeward side.
Factors that affect climate are elevation (topography), latitude, proximity to bodies of water, and currents
The stem “nimbus” means rain. Cumulonimbus clouds are storm clouds, and nimbostratus clouds are flat rain
clouds