air motions
DESCRIPTION
Air Motions. Geology 390 WSUV Dr. Robert M MacKay. 1st 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. - PowerPoint PPT PresentationTRANSCRIPT
Air Motions
Geology 390WSUV
Dr. Robert M MacKay
1st 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)
Fig. 8-16, p. 203Pressure gradient force (PGF) pushes from high to low pressure
Pressure Gradient=∆P/dist
Isobars are lines of constant pressureWhen 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 WindsWind 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 NHRight 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 NHRight 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 NHRight in SH
Is the above wind pattern associated with a central High pressureOr 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 orSouthern Hemisphere
Is the above wind pattern associated the Northern Hemisphere orSouthern Hemisphere (Counter Clockwise around High)