UW ATMS 101 - The Coriolis Force

Unformatted text preview:

Lecture 9 The Coriolis ForceLife 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 ...On the rotating earth, we feel similar ‘apparent’ forces because it takes a force to accelerate a...These apparent forces are:Centrifugal forceCoriolis forceCentrifugal ‘Force’• Apparent force pulling outward from Earth’s polar axis.• Slightly changes the apparent gravity0.5% weaker at the equator than at poles• Sea level (and Earth surface) are pulled 20 km (0.3%) further from the center of the earth at t...• By redefining ‘gravity’ to point perpendicular to sea level everywhere we can absorb centrifuga...Coriolis ‘force’ or effect• An apparent force on moving objects on the rotating Earth. (Gaspard Coriolis, 1848)Coriolis force increases proportional to ...• Latitude.• Speed of the objectIt accelerates moving objects to their right in the Northern Hemisphere and to their left in the ...It is at right angles to the motion, changing a moving object’s direction but not its speed.A commercial jet flying from Seattle to Denver feels a sideways Coriolis force of 0.1% of gravity...Coriolis Force and Air MotionClosely packed contours fi Strong PGF fi Strong windExcept near surface, winds are nearly geostrophic, blowing along the isobars at a speed for which...Effect of FrictionFriction causes near-surface wind to spiral out of high, in toward low pressure.Less friction over water than land, so surface wind blows more along isobars.Lecture 9 The Coriolis ForceLife in an Accelerating Reference Frame• Suppose we step into asubway car with aTeflon floor.• When the train starts toaccelerate, we slidebackward until we hitthe back wall.• From our perspectiveinthe accelerating car,there is a backward‘apparent’ force thatrammed us into theback wall.(rest)Our actual positionOur original positionwith respect to carOur motion withrespect to cartimeOn the rotating earth, we feel similar ‘apparent’ forces because it takes a forceto accelerate an object in a circle.These apparent forces are:Centrifugal forceCoriolis forceCentripetalforce neededto keep objectgoing in circleApparentcentrifugalforce felt byrotating observerMotion ofrotating objectCentrifugal ‘Force’• Apparent force pullingoutward from Earth’spolar axis.• Slightly changes theapparent gravity0.5% weaker at theequator than at poles• Sea level (and Earthsurface) are pulled 20km (0.3%) furtherfrom the center of theearth at the equator than at poles.• By redefining ‘gravity’ to point perpendicular to sea level everywhere wecan absorb centrifugal ‘force’ into gravity.GravityCentrifugalEffectivegravityCoriolis ‘force’ or effect• An apparent force on moving objects on the rotating Earth.(Gaspard Coriolis, 1848)EOM 6.12Coriolis force increases proportional to ...• Rotation rate of the planet• Latitude.• Speed of the objectIt accelerates moving objects to their right in the Northern Hemisphere and totheir left in the Southern Hemisphere. There is no Coriolis force at the equa-tor.It is at right angles to the motion, changing a moving object’s direction but notits speed.A commercial jet flying from Seattle to Denverfeels a sideways Coriolis force of 0.1% of gravity.If the jet starts flying toward Denver, it mustimperceptibly tip its wings to compensate, else itwould be deflected to Salt Lake City!SeattleDenverSLCCoriolis ForceCoriolis Force and Air MotionEOM 6.14Isobar = contour of contant pressure at a given height.Closely packed contours ⇒ Strong PGF ⇒ Strong windExcept near surface, winds are nearly geostrophic, blowing along the isobarsat a speed for which the Coriolis force (CF) nearly balances the PGF.(EOM)Effect of FrictionFriction causes near-surface wind to spiral out of high, in toward low pressure.Less friction over water than land, so surface wind blows more along isobars.EOM


View Full Document

UW ATMS 101 - The Coriolis Force

Download The Coriolis Force
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view The Coriolis Force and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view The Coriolis Force 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?