ATM 10Lecture topics:T, P, & WindRecall: ForcesCoriolis Force (part 1)Coriolis Force (part 2)Coriolis Force (part 3)Coriolis Force (part 4) – Southward motionCoriolis Force (part 5) – adding vectorsCoriolis Force (part 6) – Southward motionCoriolis Force (part 7) – Northward motionCoriolis Force (part 8) – Eastward motionCoriolis Force (part 9) – Westward motionCoriolis Force (part 10)Coriolis Force (part 11)Coriolis Force (part 12)Coriolis Force (part 13)Coriolis Force (part 14) - SummaryGeostrophic Winds (part 1)Geostrophic Winds (part 2)Geostrophic Winds (part 3)Geostrophic Winds (part 4)Geostrophic wind (part 5) - summaryCentripetal Force (“RF”)Surface Winds (part 1)Surface Winds (part 2)Surface Winds (part 3)Surface Winds (part 4)Surface wind (part 5) - summaryExample Weather MapsCurrent Weather MapATM 10Severe and Unusual WeatherProf. Richard Grotjahnhttp://atm.ucdavis.edu/~grotjahn/course/atm10/index.htmlLecture topics:Lecture topics:••Rotation and windRotation and wind––CoriolisCoriolisForce (CF)Force (CF)––Adding VectorsAdding Vectors••GeostrophicGeostrophicWinds (Vg)Winds (Vg)••Centripetal Force (RF)Centripetal Force (RF)••Surface WindsSurface WindsT, P, & Wind• Recall: Why do clouds move like this?Recall: Forces• 4 forces: – Pressure, – Coriolis, – Centripetal, – Friction• Most motions a combination of 2 or more these 4Coriolis Force (part 1)• Newton’s First Law: A body in motion will stay in motion unless acted upon by an external force• Viewed from space (red line) path is straight.• Viewed from the North Pole (black line) path appears defected to the right as you look from the starting point (N. Pole)Coriolis Force (part 2)• Newton’s First Law: A body in motion will stay in motion unless acted upon by an external force• Viewed from space (red line) path is straight.• Viewed from ground (black line) path appears defected to the right• The change of direction (viewed from earth) implies a force named the “Coriolis force”Coriolis Force (part 3)• Coriolis force is hard to understand because we describe things in terms of fixed points on the earth, but those fixed points are rotating• Conceptual example: playground turntableFig. 9.20Coriolis Force (part 4) – Southward motion• Example: toss ball from middle to edge. Similar to the rocket launched from the North Pole.• Ball appears deflected to the right.Coriolis Force (part 5) – adding vectors• When adding 2 vectors, put the tail of one vector to the head of the other without changing direction of either vector.• Vector A = motion from tossing item straight out.• Vector B = motion of train.• Vector A + vector B = vector C• For rotating earth (or a rotating turn table) must add a vector for motion due to that rotation.Coriolis Force (part 6) – Southward motion• Example: toss ball from middle to edge. Similar to the rocket launched from the North Pole.• Vector A = motion of the toss• Vector B = 0 no speed of rotation at the middle • Ball appears deflected to the right.ACoriolis Force (part 7) – Northward motion• Example: toss ball from edge to middle.• A = vector motion of toss. • B = vector motion of turntable where toss was made • A + B = C • Ball appears deflected to the right.Coriolis Force (part 8) – Eastward motion• Example: toss ball in direction of rotation.• A = vector motion of toss. • B = vector motion of turntable where toss was made • A + B = C • Ball appears deflected to the right.Coriolis Force (part 9) – Westward motion• Example: toss ball opposite to the direction of rotation.• A = vector motion of toss. • B = vector motion of turntable where toss was made • A + B = C • Ball appears deflected to the right.Coriolis Force (part 10)1. when you view the motion in a rotating coordinate frame, freely moving objects seem deflected.2. No matter which direction the objects move, they will be deflected towards the RIGHT when the rotation is counter-clockwise. This deflection is called the Coriolis force.Coriolis Force (part 11)• Coriolis force = CF• CF depends on latitude.• CF positive in Northern hemisphere (deflection to the right)• CF negative in Southern Hemisphere (deflection to the left)• CF = 0 at equator• CF has maximum value at North PoleCoriolis Force (part 12)• Video loop of turntable, similar to this figure, but turntable in video rotates the other direction.• Drawing has deflection to right• This rotation like looking down on North PoleCoriolis Force (part 13)• Video loop of turntable, similar to this figure, but turntable in video rotates the other direction. (Hence video has deflection to the left)• This rotation like looking down on South PoleCoriolis Force (part 14) - Summary• CF depends on rotation rate of your reference frame (Earth’s rotation rate)• CF depends on your distance from axis of rotation (a function of latitude)• CF depends on your speed relative to the reference frame (speed of the air)• CF is directed to your right (looking downwind in the Northern Hemisphere)• CF in Southern Hemisphere directed to your left (turntable rotates other way).Geostrophic Winds (part 1)• pressure gradient force (PGF) from H to L• Coriolis force (CF) always to right• PGF opposes CF for lower P on your left as look downwind.Geostrophic Winds (part 2)• CF = 2 * Ω * Vg * sin φ•PGF = ∆P / {d * ρ }• Geostrophic wind formula:• CF = 2 * Ω * Vg * sin φ = ∆P / {d ρ } = PGF• Rearranging for Vg:• Vg = ∆P / {d*ρ*2 * Ω * sin φ }GeostrophicWinds (part 3)•Vg = ∆P / {d*ρ*2 * Ω * sin φ }• Vg greater where the P slope is greater. • Low to the left means flow is mainly westerly (from west)Fig. 9.12Fig. 9.13Geostrophic Winds (part 4)•Vg = ∆P / {d*ρ*2 * Ω * sin φ }• Vg greater where P contours more closely spacedFig. 9.24Geostrophic wind (part 5) - summary• Balance between PGF & CF• Blow parallel to the pressure contour lines• In the Northern Hemisphere lower pressure is on your left as you look downwind• In the Southern Hemisphere lower pressure is on your right as you look downwind.• Good approximation for winds more than 1 km above the ground (outside tropics)• Closer spacing of pressure contours means faster wind.Centripetal Force (“RF”)• When spin something around there is a force required to keep the object from flying off• The force keeps the direction of the