Transcript What Influences Weather?

Pages 229-241
How does the water cycle
affect weather?
 Water is constantly being recycled between liquid,
solid, and gaseous states
 Evaporation – Liquid to gas (forms water vapor)
 Transpiration – Liquid to gas FROM PLANTS (forms
water vapor)
 Condensation – Gas to liquid (forms clouds, fog, dew)
 Precipitation – Falls from clouds
 * Runoff – water that flows over land (streams, rivers)
 * Infiltration – seeps into the ground (ground water)
How does the water cycle
affect weather?
 The water cycle can cause a change in humidity,
visibility, and precipitation.
How do air masses affect weather?
 The weather changes when a new air mass moves into
your area.
 An air mass is a large volume of air in which
temperature and moisture content are nearly the same
throughout.
 Ex: If we have a warm, humid air mass sitting on our
city, we will have warm, humid weather.
What are air masses?
 https://www.youtube.com/watch?v=kzNR_tjKExU
How do fronts affect weather?
 When two air masses meet, a boundary or FRONT
forms.
 The warm air is forced up, cools and condenses, forms
clouds, and allows for precipitation.
 Cold front – moves quickly, brings heavy rain, cooler
weather follows
 Warm front – moves slowly, brings drizzly rain,
warmer weather follows
 Stationary front – doesn’t move, brings precipitation
for many days
Cold Fronts vs. Warm Fronts
 https://www.youtube.com/watch?v=tsD6zkBMmck
How do pressure systems
affect weather?
 In a high-pressure system, air sinks slowly down.
 Brings clear skies and calm air or gentle breezes
 In a low-pressure system, air rises.
 As the air rises, it cools, condenses, and forms clouds
 Brings stormy weather
REMEMBER: Winds always
blow from a high pressure
to a low pressure!
High vs. Low Pressure
 https://www.youtube.com/watch?v=aiYyCurh_SU
How do global winds
affect weather?
 Winds are caused by unequal heating of Earth’s
surface – which causes air pressure differences – and
can occur on a global or on a local scale.
 Global winds are:
 Polar easterlies – cold winds from the poles, blow EW,
60-90 latitudes
 Westerlies – blow from WE, 30-60 latitudes
 Trade winds – blow from EW, 0-30 latitudes
 Winds can bring weather that isn’t typical for an area.
Global Winds and Jet Streams
 https://www.youtube.com/watch?v=GvXPtQuQtiU
How do jet streams
affect weather?
 Long distance winds that travel
above the global winds
 They move very quickly in a
wavy pattern from WE
 Polar jet stream – brings cool,
dry air
 Subtropical jet stream – brings
warm, moist air
 Strong storms tend to form
along jet streams also
The Jet Stream
 https://www.youtube.com/watch?v=CgMWwx7Cll4
 https://www.youtube.com/watch?v=huweohIh_Bw
A Summary of the Jet Stream
 Jet streams are strong upper air currents
circumnavigating the globe.
 There are two main jets: the polar jet and the
subtropical jet.
 Jet streams can fluctuate in strength between 100200mph.
 The jet stream meanders in waves.
How do ocean currents
influence weather?
 Remember that ocean waters take a lot of energy and
time to warm up or to cool down
 This helps to moderate temperatures
 Winds cause ocean currents on the surface which can
bring cool weather or warm weather to areas
 Ex: Gulf Stream – brings warm water from the Gulf of
Mexico up the east coast of the US
 Ex: East Australian Current – brings warm water down
towards polar regions, FINDING NEMO Sea Turtles
used it for transportation
Ocean Currents
 https://www.youtube.com/watch?v=6vgvTeuoDWY
Gulf Stream
 https://www.youtube.com/watch?v=rR5TFWNLtOc
East Australian Current (EAC)
 https://www.youtube.com/watch?v=I-N_7cgwHmQ