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W&C Ch. 2 Notes
Weather and Climate Chapter 2: Understanding Weather
1. Water in the Air
* The Water Cycle – the continuous movement of water from Earth’s _____________
& __________________ into the _______________________, in the
_______________, and back into the _______________ & ________________
- Humidity
* Amount of _____________________ in the air
* As the ______________________ increases so does the air’s ability to hold
water vapor
- Relative Humidity – measures the amount of _______________________ in the
air compared with the __________________ amount of water vapor that the air
can hold at a certain temperature
* Measured using a _____________________
- Condensation – process by which a gas (water vapor) becomes a liquid (water)
* The air must be ______________________ (100% relative humidity)
* Can also occur when air cools to its ________________________ (the
temperature at which gas becomes a _________________)
* Clouds – a collection of small water droplets or ice crystals suspended in the air
- Cumulus – puffy, white clouds that tend to have flat bottoms
- ______________ – form in layers & cover large areas of the sky & often block
out the sun (___________ is a stratus cloud that has formed near the ground)
- Cirrus – thin, feathery clouds found at high altitudes
- Nimbo – or – nimbus indicate clouds that are likely to form
_____________________
- Cirro – clouds formed at high altitudes
- Alto – clouds formed at middle altitudes
* Precipitation – when water returns to Earth’s surface
- Rain – most common
- _______________ – rain falls through freezing air & freezes into ice
- _______________ – air is so cold that the water vapor freezes directly into ice
- Hail – forms when raindrops are caught in an updraft & are carried into higher
clouds where it freezes. As it starts to fall more water vapor attaches to the ice.
The ice may be caught in another updraft & the outer water vapor freezes. This
happens again & again until the ice ball is too heavy to be lifted by an updraft.
The largest hailstone ever recorded was the size of a softball
W&C Ch. 2 Notes
2. Air Masses and Fronts
* Air mass – large body of air where ____________________ &
__________________________ are similar throughout
- Air masses that affect North America are represented by two symbols
* M - ____________________ – forms over water, wet
* C - ___________________ – forms over land
* P - _____________ – cold air
* T - ____________________– warm air
* Fronts – where two or more air masses meet – generally cause some form of
precipitation
- Cold front – cold air moves __________ warm air forcing the warm air to
________ – causes ______________________, heavy rain or snow then dry cool
weather
- Warm front – warm air moves __________ cold air – bring drizzly rain then
warm dry weather
- Occluded front – ____________ air is caught between two __________ air
masses – brings cool air & heavy rain or snow
- Stationary front – cold air & warm air meet with neither having the force to
move the other – bring many days of _______________________________
* Air Pressure & Weather
- Cyclones – rotating area around a low pressure area
- Anticyclones – rotating area around a high pressure area – winds will often feed
into a cyclone area
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W&C Ch. 2 Notes
3. Severe Weather
* Thunderstorms – small intense weather systems that produce
___________________, ______________________, ___________________ &
___________
- Requires warm, moist air near the surface & unstable atmospheric conditions
(surrounding air is colder than the rising air)
- Falls from ______________________ clouds
- Lightning – electrical discharge between a __________________ charged area
& a ____________________ charged area
* The energy causes the air to expand rapidly & send out sound waves
(__________________)
* Lightening is one of the most dangerous part of thunderstorms
- Severe storms can also cause _______________ & produce _________________
* Tornadoes
- Formed when wind moving in two directions causes a layer of air to start
spinning
- When the _______________ cloud reaches the ground it is considered a tornado
- _____% of tornadoes occur in the US
- Winds can reach ______ km/h
* Hurricanes – most powerful storms on Earth
- Start as a group of thunderstorms moving over ______________________ water
- Winds traveling in two different directions cause the storm to spin
- Fueled by warm water – loses its strength when it reaches _______ or
_________________
- Parts of a hurricane
* ________ – center of the storm, area of warm, calm air with low-pressure &
little wind
* Eye wall – __________________ part of the hurricane with heavy rain &
strong winds (up to 300 km/h)
* Rain bands – spiraling bands of clouds that extend beyond the eye wall.
Contain heavy rain & strong winds
- ___________________ – wall of water that builds up over the ___________
because of the strong winds and low pressure
W&C Ch. 2 Notes
* Severe Weather Safety
- Thunderstorms – stay inside. If you’re caught outside stay away from ________
& _________________________. If you’re in the open, crouch down so you’re
not the tallest object in the area.
- Tornadoes – find shelter in a _____________ or an interior room with no
windows such as a __________________ or ______________. If outside, lie
down in a field or deep ditch.
- Floods – find a ___________________ to wait out the flood. Stay out of flood
waters even if they look shallow
- Hurricane – listen to local TV & radio for updates. Prepare a ______________
supply kit with water & _____________________ food. Board up windows if
necessary. __________________ the area if instructed to.
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4. Forecasting the Weather
* ______________________ – person who observes & collects data on atmospheric
conditions to make weather predictions
* Weather forecasting technology
- Weather balloons – carry equipment that can measure weather conditions as high
as 30 km above Earth’s surface
- _____________________ – measures temperature
- _____________________ – measures air pressure
- Windsock or wind vane determine _________________________
- Anemometer determine _____________________
- Radar & satellites find the location, movement & amount of precipitation
- Weather maps are based on information gathered from 1000 weather stations
across the US
* H or L indicates high & low pressure areas
* ________________ – lines that connect points of equal air pressure
* Front are also labeled