Lecture 9 The Coriolis Force Life in an Accelerating …...Lecture 9 The Coriolis Force Life in an...
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Lecture 9 The Coriolis Force Life in an Accelerating Reference Frame • Suppose we step into a subway car with a Teflon floor. • When the train starts to accelerate, we slide backward until we hit the back wall. • From our perspective in the accelerating car, there is a backward ‘apparent’ force that rammed us into the back wall. (rest) Our actual position Our original position with respect to car Our motion with respect to car time
Transcript of Lecture 9 The Coriolis Force Life in an Accelerating …...Lecture 9 The Coriolis Force Life in an...
• SupsubTefl
• Whaccbacthe
• Frothethe‘aprambac
Our actual position
Our original positionwith respect to car
Our motion withrespect to car
Lecture 9 The Coriolis Force
Life in an Accelerating Reference Framepose we step into away car with aon floor.en the train starts toelerate, we slidekward until we hit back wall.m our perspective in accelerating car,re is a backwardparent’ force thatmed us into thek wall.
(rest)
time
On th e it takes a forceto ac
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e rotating earth, we feel similar ‘apparent’ forces becauscelerate an object in a circle.
e apparent forces are:
trifugal force
riolis force
Centripetalforce needeto keep objegoing in cir
Apparentcentrifugalforce felt by
rotating observ
Motion ofrotating obje
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• Sligapp
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Gravity
CentrifugalEffectivegravity
Centrifugal ‘Force’
parent force pullingward from Earth’sar axis.htly changes thearent gravity
.5% weaker at thequator than at poles
level (and Earthface) are pulled 20 (0.3%) furtherm the center of theth at the equator than at poles. redefining ‘gravity’ to point perpendicular to sea level e absorb centrifugal ‘force’ into gravity.
• An(Ga
Coriolis ‘force’ or effect
apparent force on moving objects on the rotating Earth.spard Coriolis, 1848)
EOM 6.12
• Ro• Lat• Spe
It acc misphere and totheir rce at the equa-tor.
It is a direction but notits sp
A cofeelsIf theimpewoul
le
Denver
SLC
Coriolis force increases proportional to ...
tation rate of the planetitude.ed of the object
elerates moving objects to their right in the Northern Heleft in the Southern Hemisphere. There is no Coriolis fo
t right angles to the motion, changing a moving object’seed.
mmercial jet flying from Seattle to Denvera sideways Coriolis force of 0.1% of gravity. jet starts flying toward Denver, it mustrceptibly tip its wings to compensate, else itd be deflected to Salt Lake City!
Seatt
Coriolis Force
r ofre at
Coriolis Force and Air MotionEOM 6.14
Isobar = contou contant pressu a given height.
ng wind
Exce long the isobarsat a s he PGF.
Closely packed contours ⇒ Strong PGF ⇒ Stro
pt near surface, winds are nearly geostrophic, blowing apeed for which the Coriolis force (CF) nearly balances t
(EOM)
Frict rd low pressure.Less e along isobars.
EO
Effect of Friction
ion causes near-surface wind to spiral out of high, in towafriction over water than land, so surface wind blows mor
M 6.18
