Air Motions Geology 390 WSUV Dr Robert M

Air Motions Geology 390 WSUV Dr. Robert M Mac. Kay

1 st Law (Law of Inertia) Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it. acceleration = 0. 0 unless the objected is acted on by an unbalanced force

Which path does the ball follow after the string breaks?

Which path does the ball follow after the string breaks? Path C

Forces that influence the wind 1. Pressure Gradient Force 2. Coriolis Force 3. Friction On average Gravity nearly balances the vertical Pressure gradient (hydrostatic balance)

Pressure gradient force (PGF) pushes from high to low pressure Fig. 8 -16, p. 203

Pressure Gradient=∆P/dist Isobars are lines of constant pressure When distance between isobar is large the pressure gradient is small and when the distance is small the pressure gradient is large.

Pressure Gradient Where is the pressure gradient largest A, B, C, or D ?

Pressure Gradient Where is the pressure gradient largest A, B, C, or D ? ANSWER A

Centrifugal force an (Apparent Force)

Centrifugal force an (Apparent Force)

Coriolis Force (apparent force due to Earth’s rotation)

Coriolis Force Deflects air to right in NH & Left in SH Is always zero at the equator Increases with latitude Increases with wind speed Increases as planet rotation speed increase

Coriolis Force

Coriolis Force

Geostrophic Winds Wind flows parallel to straight line isobars Geostrophic wind the PGF is balanced by the Coriolis force. Low pressure is always to the Left of the wind direction in NH Right in SH

Geostrophic Winds When isobars are close wind speeds are high.

In the Northern hemisphere cyclonic flow is counter clock-wise As air moves toward the center of rotation is spins faster so cyclonic flow is typical relatively fast. Central low pressure is associated with rising air and hence clouds / rain

In the Northern hemisphere Anti-cyclonic flow is clock-wise As air moves away from the center of rotation is spins slower so anti-cyclonic flow is typical relatively slow. Central high pressure is associated with sinking air and clear skies.

Which hemisphere?

Which hemisphere? NH

Which hemisphere?

Which hemisphere? SH

In the upper atmosphere wind flows parallel to isobars and is fast where isobars are close together. Low pressure is always to the Left of the wind direction in NH Right in SH

Friction near the surface slows wind speeds, weakens the coriolis force and tend to steer winds towards the low pressure. Low pressure is always to the Left of the wind direction in NH

Is the above wind pattern associated with a central High pressure Or Low pressure?

Is the above wind pattern associated with a central High pressure (the air flow is away from center) Or Low pressure?

Is the above wind pattern associated the Northern Hemisphere or Southern Hemisphere

Is the above wind pattern associated the Northern Hemisphere or Southern Hemisphere (Counter Clockwise around High)