Transcript What Is Weather?

What Is Weather?
Weather Factors
• Define weather.
• Weather is the condition of the atmosphere at any given
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moment.
Name four conditions that weather describes.
Weather describes:
• Air pressure
• Wind
• Temperature
• The amount of moisture in the air
Air Temperature
• What is temperature?
• Temperature is a measure of the average
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amount of motion of molecules.
Explain what causes temperature to feel hot or
cold.
When the temperature is high the molecules
move faster and it feels warm. When the
temperature is low the molecules move slower
and it feels cold.
Wind
• Explain what causes wind.
• Wind results when air moves from an area of high
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pressure to an area of low pressure.
Name the instruments that are used to measure wind
direction.
A wind vane and a wind sock are used to measure
wind direction.
Name the instrument that is used to measure wind
speed.
An anemometer is used to measure wind speed.
Humidity
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Explain where water goes when it evaporates.
When water evaporates it fits into spaces among the air molecules.
What is humidity?
Humidity is the amount of water vapor in the air.
Which will hold more water vapor, warm air or cold air. Explain.
Warm air holds more moisture. The molecules of water vapor in
warm air move to fast to stick together.
• What is condensation?
• Condensation is when water vapor cools and forms water droplets
Relative Humidity
• What does it mean when we say that the air is
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saturated?
Saturated means that the air cannot hold any
more moisture.
Relative Humidity
• What is relative humidity?
• Relative humidity is the amount of moisture the
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air is holding compared to what it could hold at
that temperature.
When the weatherman's says that we have 60%
relative humidity what does that mean?
60% relative humidity means that the air is
holding 60% of the moisture that it could hold at
that temperature.
Dew point
• What is dew point?
• Dew point is the temperature at which the air
becomes saturated and condensation forms.
Forming clouds
• Explain what causes clouds to form.
• Clouds form when warm air rises, cools and the
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water vapor condenses forming clouds.
Name the three basic forms of clouds.
The three basic forms of clouds are:
stratus
Cumulus
cirrus
Classifying Clouds
• Describe stratus clouds.
• Stratus clouds are layered, or smooth even
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sheets.
Describe cumulus clouds.
Cumulus clouds are puffy, white clouds with flat
bases.
Describe cirrus clouds.
Cirrus clouds are wispy, feathery, clouds made
of ice crystals.
Cloud height
• Name the three prefixes that describe the height
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of a cloud and tell what each one means.
Cirro means high clouds, alto describes middleelevation clouds and strato describes low
elevation clouds.
What does nimbus means and what kind of
weather is associated with it.
Nimbus means dark rain cloud and is associated
with rainy or snowy weather.
Precipitation
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What is precipitation?
Precipitation is water falling from clouds.
Name two factors that affect the size of raindrops.
The size of a raindrop depends on the strength of the
updraft and the rate of evaporation.
• Explain what determines whether precipitation falls as
rain or snow.
• Air temperature determines whether water falls as rain
or snow.
Precipitation
• What causes hail?
• Hail is caused when water freezes in layers
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around a small nucleus of ice.
What determines how large hailstones will be?
The strength of the updraft in a thunderstorm.