The Coriolis Effect
What is the coriolis and why should I care about it?
The coriolis effect
is why everything that is moving in the Northern hemisphere
turns right and everything that is moving in the Southern
hemisphere turns left-the reason why lows and highs, ocean
currents and tides circulate the way they do
We all know that the Earth rotates from west to east and takes
about 24 hrs to go around. If you stood on the equator you would
be moving faster than if you were standing on the North and
South pole and so in 24 hrs you would make more distance .So in
effect a point on the equator travelling at about 1,600 km/h)
travels more than a point on the 60 degrees Northpole travelling
at about 800km/h
To understand the coriolis effect, thing of a cloud in Dublin.
Before you do anything you must realise that its travelling west
to east at a certain speed, say for example “Dublin speed". If
you now suddenly push it southwards towards Spain the cloud will
be travelling at Dublin speed but the ground beneath it is
travelling at a faster speed. Therefore the clouds will lag
behind relative to earth surface. Instead of travelling directly
north to south it will veer to the right
If on the other hand the cloud starts in Spain and you push it
towards Dublin, the opposite will happen. The cloud having
carried with it its Spanish west east velocity, will find itself
travelling eastwards faster than the Earth beneath it, and so it
will swerve to the right.
If you force the cloud in an east west direction, say from
Dublin travelling from west to east with the earth at Dublin
speed .This time as it moves eastward towards say Moscow its
rotational speed has increased slightly, This increase in speed
means an increase in the centrifugal force, which tends to throw
the cloud outwards, the easiest thing the cloud can do is to
increase its radius of curvature is to move to a position where
the earth is fatter and so the cloud ends up swerving south
towards the equator. Alternatively if you move the cloud
westwards from Moscow to Dublin, you decrease its rotational
force and so decrease its centrifugal force. As a result it
wants to travel around a smaller radius of curvature nearer the
North pole. It veers off towards the north.

In summary by a
combination of two different mechanisms , air in the northern
hemisphere will swerve right and in the southern hemisphere the
opposite occurs with air moving to the left.
How does all this help us understand weather patterns and why
highs and lows move they way they do. The natural tendency for
any of these clouds or air parcels is to move from high to low
pressure i.e. down the pressure gradient. Imagine a centre of
low pressure in the Northern hemisphere surrounded by air at a
relatively higher pressure. Immediately there will be a stream
of air parcels trying to rush into the low from outside i.e.
trying to fill up the low and equalise the pressure. But the
coriolis force deflects them to the right and they end up
revolving around the low pressure in an anticlockwise direction.
The same principle applies to a high pressure cell surrounded
but lower pressure. The air will try to flow out and and
equalise the pressure, however they will be deflected to the
right and end up going around in a clockwise direction. In
the southern hemisphere the opposite happens and so lows go
clockwise and highs go anticlockwise.

It should now be obvious that the coriolis force is central now only to meteorology but oceanography as well and can be used to explain why ocean currents bring cold polar water to west facing coasts and why tides behave in such strange ways.




