Chapter 19 The Atmosphere in Motion  Page 412  What special gear is the hang glider wearing?  What force is keeping the hang glider aloft?  What other kind of activities depend on this force?  What causes winds?

Chapter 19.1

Air Pressure and the Wind

What is air pressure? AAAA column of air that reaches from sea level to the tom of the atmosphere pushes down at 147lbs per square inch AAAAir pressure – is the weight of the overlying atmosphere IIIIt is exerted in all directions FFFForce pushing on your body is balanced by your body pushing out

TTTT hhhh eeee h h h h iiii gggg hhhh eeee rrrr y y y y oooo uuuu g g g g oooo i i i i nnnn tttt oooo t t t t hhhh eeee a a a a tttt mmmm oooo ssss pppp hhhh eeee rrrr eeee t t t t hhhh eeee l l l l oooo vvvv eeee rrrr tttt hhhh eeee p p p p rrrr eeee ssss ssss uuuu rrrr eeee BBBBarometers – used to measure air pressure –A–A–A–Aneroid – evacuated can with read outs attached and barograph –M–M–M–Mercury p 414 UUUUnits of air pressure –i–i–i–inches or millimeters – used to read mercury –m–m–m–millibars used on weather maps – these are adjusted to sea level pressure due to altitude differences

Why does air pressure Change Why does air pressure Change EEEElevation – higher up less air pressure TTTTemperature – the warmer (more spread out) the less Air P. WWWWater Vapor – the more water vapor the lower the A.P. – H2O molecules weigh less than the N & O molecules in the air IIIIsobars – lines of equal pressure – closed isobar forms a closed lop on a map

IIIIf pressure increases toward center it is a High Pressure Center LLLLow pressure center – pressure is lower PPPPressure Gradient – how close the isobars are. Close together – large gradient

What makes the wind blow DDDDifference in A.P. – the greater the difference the faster the winds. The closer the isobars the faster the wind AAAA wind blows form High P. to low P. –e–e–e–e.g. Hot air on an island rises (form L.P.) Cool air from the water (H.P) rushes in, this is known as a sea breeze

Measuring surface wind direction and speed. WWWWind vane – measure the direction from which the wind is blowing – Winds are named by the direction they come from –e–e–e–e.g. westerly or sea breeze AAAAnemometer – measure wind speed

Chapter 19.2

Factors affecting Wind

Coriolis Effect IIIIf the earth did not spin and was perfectly smooth air would flow strait from high pressure areas (poles) directly to low pressure areas (equator) CCCCoriolis effect causes objects traveling freely over the earth to curve –I–I–I–I nnnn n n n n.... h h h h eeee mmmm iiii ssss pppp hhhh eeee rrrr eeee c c c c uuuu rrrr vvvv eeee r r r r iiii gggg hhhh tttt –I–I–I–I nnnn s s s s.... h h h h eeee mmmm iiii ssss pppp hhhh eeee rrrr eeee c c c c uuuu rrrr vvvv eeee l l l l eeee ffff tttt –T–T–T–The effect is greater near the poles –T–T–T–The effect is also greater in long diastase travel vs. short travel –T–T–T–The effect increases with increased speed

FFFFriction – with the earth’s surface slows winds down. The smooth surface(water) the faster wind can blow the higher coriolis effect TTTThe coriolis effect is a strong factor in determining wind direction as is a Pressure gradient speed CCCC oooo rrrr iiii oooo llll iiii ssss c c c c aaaa uuuu ssss eeee ssss w w w w iiii nnnn dddd ssss t t t t oooo b b b b llll oooo wwww c c c c oooo uuuu nnnn tttt eeee rrrr cccc llll oooo cccc kkkk wwww iiii ssss eeee i i i i nnnn a a a a l l l l oooo wwww,,,, c c c c llll oooo cccc kkkk wwww iiii ssss eeee i i i i nnnn h h h h iiii gggg hhhh JJJJet stream – swift winds due to low friction – direct path of storms

Global Wind Patterns NNNNon rotating earth would allow warm air to rise at the equator, move to the poles and sink to travel back to the equator, resulting in large circulation cell TTTThe coriolis effect (Rotation of earth) prevents this from happening 3333 cell circulation model WWWWeakness of 3Celled model –g–g–g–gives simplified view of circulation between 30 and 60 –N–N–N–No effect given to continents or season –S–S–S–Simplifies upper level winds

B. Description of Wind and Pressure Belts IIIITCZ (intertropical convergence zone) occurs at the equator –h–h–h–hot and humid with little or no wind –r–r–r–rain is common –h–h–h–historically been called the doldrums BBBBetween 20 and 35 air sinks forming subtropical highs, location of earth’s deserts. Known as horse latitudes BBBBetween the doldrums and the horse latitudes are the easterly trade winds –W–W–W–Warm and steady (speed and direction) winds

Chapter 19.3

Continental and Local Winds

Effects of Seasons and continents SSSSeasons, land masses and topography causes winds to vary from global patterns depicted in the 3 cell model HHHHot air above land in summer creates low- pressure. Cold air above oceans in summer creates high pressure –e–e–e–e.g. Atlantic Highs bring winds off the ocean into the eastern sea board. Winter is reversed MMMMonsoons – winds caused by seasonal pressure changes

Local winds – extent 100 km or less include sea breeze, land breeze, mountain breeze and valley breeze SSSS eeee aaaa – – – – l l l l aaaa nnnn dddd b b b b rrrr eeee eeee zzzz eeee - - D D D D uuuu rrrr iiii nnnn gggg d d d d aaaa yyyy l l l l aaaa nnnn dddd i i i i ssss wwww aaaa rrrr mmmm eeee rrrr c c c c rrrr eeee aaaa tttt iiii nnnn gggg l l l l oooo wwww p p p p rrrr eeee ssss ssss uuuu rrrr eeee a a a a bbbb oooo vvvv eeee ```` cccc aaaa uuuu ssss eeee ssss t t t t hhhh eeee c c c c oooo oooo llll a a a a iiii rrrr ( ( ( ( HHHH )))) t t t t oooo b b b b llll oooo wwww iiii nnnn gggg f f f f rrrr oooo mmmm tttt hhhh eeee w w w w aaaa tttt eeee rrrr ( ( ( ( ssss eeee aaaa )))) a a a a nnnn dddd n n n n iiii gggg hhhh tttt i i i i tttt r r r r eeee vvvv eeee rrrr ssss eeee MMMMountain Breeze – at night the air against the mountain cools more than the surround air and sinks down hill VVVValley breeze – mountain heats the air causing it to rise and the air from the valley flows up hill