Geostrophic flow Flashcards

1
Q

what is geostrophic wind

A

A geostrophic wind results from an equal and opposite balance between two forces, the horizontal pressure gradient force and the Coriolis

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2
Q

what happens when a column of air is heated

A

It expands, pressure falls less rapidly with height

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3
Q

what happens if a column of air is cooled

A

Then it condenses, pressure falls more rapidly with height

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4
Q

What way does air flow

A

From high pressure to low pressure

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5
Q

What happens if a surface is heated differentially

A

Air expands more rapidly at the warmer end

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6
Q

What does air expanding at the warmer end of a surface result in

A

A horizontal pressure gradient force and therefore a pressure gradient force. the pressure gradient force then causes air to move towards the region of lower pressure

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7
Q

What about the pressure increases with height above ground level

A

The pressure gradient and therefore pressure gradient force increases with height above ground level

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8
Q

In the pressure gradient force equation what does P mean

A

It means the density of air; this will be given where necessary, but near the surface it is 1.225 kg/m

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9
Q

What is dn in the pressure gradient force equation

A

Change in location (distance) in metres

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10
Q

What is dp in the pressure gradient force equation

A

Change in pressure, convert hPa to (in N/M squared) (hPa times 100 =N/m squared)

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11
Q

what is N in the PGF equation more in depth

A

N is the distance between the flow from higher pressure to lower pressure that you are calculating and can be measured irrespective of orientation provided n remains perpendicular to isobars

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12
Q

How does moving from high to low pressure effect our value of n

A

Will always be a negative value (down-gradient)

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13
Q

What are three important points about the Coriolis force

A

An apparent force, Deflects objects to the right in the northern hemisphere, impacts large scale flow over a period of a few hours

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14
Q

How can you calculate wubleu

A

Divide 2pi radians by the number of seconds in a day.

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15
Q

What is the value of wubleu

A

7.29 times 10 to the the minus 5 rad/sec

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16
Q

What is the component of the earths rotation around the local vertical at P

A

wubleu sin theta (radians are dimensionless)

17
Q

Explain how the pressure gradient force interacts with the coriolis force

A

The PGF induces a flow towards the region of lower pressure and Coriolis force deflects it

18
Q

What is said when the pressure gradient force Coriolis are equal and opposite

A

They are said to be in geostrophic balance

19
Q

What is the wind formed by geostrophic balance

A

Known as the geostrophic wind

20
Q

What does isobar spacing give an indication of

A

Geostrophic wind

21
Q

What is the equation for geostrophic wind

A

vg = -1/fp dp/dn