Weather Instruments

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Weather Instruments
These are the instruments that measure the
primary weather variables in our atmosphere
Barometer Rain gauge Thermometer Anemometer Sling
psychrometer
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Most sudden changes in the weather are a result
of Air Masses
An air mass is defined as a large parcel of
air that has taken on the characteristics of the
surface over which it has been sitting
When an air mass sits over a surface of the
earth It can acquire 2 primary properties
1. temperature
2. moisture content
How many possible combinations of air masses
could you have using only these 2 variables?
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1.warm and moist
2. warm and dry
3. cold and moist
4. cold and dry
What type of surface would these air masses form
over?
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Cold air mass
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cP
mT
cT
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The leading edge of an air mass is called a FRONT
The symbols point in the direction the air is
moving
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COLD FRONT

• COLD air mass advances on a WARM air mass,
  pushing forward into the warm air

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WARM FRONT

• WARM air mass advances on a COLD air mass.
• Since the cold air is more dense, the warm air
  mass is forced to rise as it pushes forward

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OCCLUDED FRONT

• TWO cold fronts approaching each other are
  separated by a warm air mass
• As the two cold fronts near each other, the warm
  front is pushed up over the cold front and off
  the ground

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Stationary Front

• A warm air mass and a cold air mass are adjacent
  to each other, but do not move

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The leading edge of an air mass is called a
Front
Here is a surface map showing a cold front that
has just moved through the midwest
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The following things usually happen as a cold
front approaches and moves past a location
cold front side view

• A rapid increase in cloud cover, usually tall
  cumulous or
• cumulonimbus type

2. A rise in the wind velocity, and shift in
direction from south to north
3. Brief heavy precipitation or thunderstorm
possible
4. A rapid fall in pressure, followed by a
gradual rise
5. A sharp drop in temperature
Notice the high angled slope or pitch
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Simulation at high speed
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Warm front side view
The following weather changes usually occur as a
warm front approaches
1. A steady drop in pressure
2. Cirrus clouds are first indication of
approaching warm front
3. A gradual increase in clouds until entire sky
is covered
4. A gradual increase in temperature
5. Long term light to moderate precipitation
6. A shift in the winds from north to south
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A warm front is a much gentler slope or pitch
Changes in the weather Occur much more slowly