[gem]

Hi B/C in regards to the effects being small, I assume you are referring to the positive/negative frictional coupling Effect between the Atmosphere and earth’s surface, as per the original question.
So just to put a comparison value to reiterate that point and I think you posted previously in regards to how large the earth’s angular momentum is.
As a fraction of the Total solar radiation Received by Earth for one day allowing around 30% reflection vs Earth’s rotational Kinect energy gives :
Solar energy per day is 0.000005% of Earths rotational Kinect energy

[Bored chemist]

Hi B/C in regards to the effects being small, I assume you are referring to the positive/negative frictional coupling Effect between the Atmosphere and earth’s surface, as per the original question.
So just to put a comparison value to reiterate that point and I think you posted previously in regards to how large the earth’s angular momentum is.
As a fraction of the Total solar radiation Received by Earth for one day allowing around 30% reflection vs Earth’s rotational Kinect energy gives :
Solar energy per day is 0.000005% of Earths rotational Kinect energy

I thought my explanation to Alan was pretty clear.
That rotational energy is big, more importantly, it's not going anywhere (except due to tidal drag).
But many thanks for doing the maths for us.
As you say:
"Solar energy per day is 0.000005% of Earths rotational Kinetic energy"
That means that the energy of rotation is equivalent to about 55000 years' radiation from the  Sun .
So, if the weather was taking more energy from the spin than from the sun (as Alan originally said) then (simplistically) over about 55,000  years, the energy would be gone.
But the Earth is still spinning. And we know it's been spinning at pretty much the same rate for since they built Stonehenge.
That's about 5000 years ago.
A 10% change in the Earth's rotational energy would correspond to about a 5% change in rotation rate (The energy varies as the square of the rate).

And if the length of the day had varied by 5%, Stonehenge just wouldn't be aligned any more.
So that's another convincing argument that Alan is wrong.

[gem]

Yes what your saying makes perfect sense and is aligned with mainstream science, and in regards to your dispute with Alan, I believe it’s well accepted that the weather cycle is powered by the solar energy received.
Its also currently known that the weather patterns have a direct impact on length of day.
Which raises the question why does it appear that although there are known fluctuations To LOD due to the frictional couplings Due to weather patterns, the overall effects overtime is neutral. As per your post above.

On a slightly separate note I believe LOD is believed to have been around 20 hrs in the Devonian period but that is postulated that rotational energy has been transferred to the moons orbit.

[Bored chemist]

There's really rather a lot of science about it. I found more than I expected here
https://en.wikipedia.org/wiki/Day_length_fluctuations

But the atmospheric contribution- apart from the even smaller effect of airborne tides*- averages to zero.

*"even smaller" compared to the very small effect of oceanic tidal drag.

[alancalverd (OP)]

And what Alan was saying was that the spin of the Earth powered the weather.

I never said that.

Blazing sunshine today, no wind. If the sun powers the wind, why not?

If the sun is the principal determinant of wind, why is the prevailing wind westerly in high latitudes and easterly in low latitudes?

Sun heats earth, earth heats air, so there is more solar-derived energy in the lower atmosphere. But wind speed increases with altitude. And not just over mountains, but in the middle of the oceans, deserts and prairies. How come?

Why do we get more gales in the winter, when there is less sun?

[Bored chemist]

I never said that.

Was it some other Alan Calverd then?

Ignoring second-order effects such as thermal winds, the source of kinetic energy is the rotational energy of the planet, so it must eventually stop spinning.

The prevailing geostrophic wind is the result of coriolis force making the air move relative to the surface of the earth.  If we extract kinetic energy from the geostrophic wind and dissipate it as heat, whence came that energy? The only source is the spin of the earth.

The wind in the Southern Ocean is almost entirely due to the earth's spin

Just stop being silly and admit you got it utterly wrong.

[Bored chemist]

Blazing sunshine today, no wind. If the sun powers the wind, why not?

Earth is rotating today.
No wind.
If the rotation of th...
You get the point.

[alancalverd (OP)]

Was it some other Alan Calverd then?

I don't see the word "weather" in that sentence.

[alancalverd (OP)]

Just stop being silly and admit you got it utterly wrong.

I will pass your comment to the meteorological department of the International Civil Aviation Organisation, with a recommendation to modify the examination syllabus in line with such qualified expertise.

[Bored chemist]

Was it some other Alan Calverd then?

I don't see the word "weather" in that sentence.

The word popliteal is also missing.
So...?
Or are you somehow seeking to pretend that the wind isn't part of weather or some such?
Fundamentally, the windmill still doesn't get its energy from the rotation of the Earth.

[Bored chemist]

Just stop being silly and admit you got it utterly wrong.

I will pass your comment to the meteorological department of the International Civil Aviation Organisation, with a recommendation to modify the examination syllabus in line with such qualified expertise.

Well, that's not a bad idea- if they are teaching that the wind gets its energy from the rotation of the Earth- but I suspect they are not.
As I said; you have mistaken the rudder for the engine.
I doubt the ICAO would be happy to find pilots making that error.

[alancalverd (OP)]

The geostrophic wind is crucial to understanding major weather systems.

Sea breezes are great fun for gliding and dinghy sailing, but if you want to travel long distances or at high altitude, or extract useful electricity from the wind, you need to look beyond the primary school textbooks. 

This isn't new stuff. Prehistoric mariners understood trade winds and westerlies and were able to sail on oceans (where there is no differential heating even at midday) in the absence of sunshine.

[Bored chemist]

This isn't new stuff.

Well, I'm glad you accept that.
Because it helps demonstrate why you are mistaken.
If the Earth had been putting lots of energy into the weather for a long time, then the Earth would have slowed down since, for example, Stonehenge was built.


You still haven't actually answered the fundamental question.
What supplies the external torque that slows down the Earth's spin?
Surely you accept that , for a given moment of inertia, and a conserved angular momentum, the rotation rate , and thus the rotational energy of the Earth is conserved (pace  tides buffs) .

[Bored chemist]

The geostrophic wind is crucial to understanding major weather systems.

Did you notice how nobody ever said they weren't?
Nor has anyone said that their direction is not due to the spin of the Earth.

That's my point.
You keep thinking the rudder is the engine.

[alancalverd (OP)]

I refer the hon gent to reply #8 above, and the laws of physics.

The dominant geostrophic component of wind arises from the rotation of the planet. Windmills extract kinetic energy from the wind. We turn that energy into heat which is ultimately radiated away from the planet.

[Bored chemist]

I refer the hon gent to reply #8 above

Either that post agrees with the conservation laws, in which case it's redundant, or it disagrees, in which case it's wrong.

Are you saying that we can extract energy from the rotation of the Earth without slowing that rotation down?
Or are you saying you can slow down the Earth's rotation without an external torque?

[gem]

Yes I would agree oceanic tidal drag is probably an even greater frictional source of energy loss to the kinetic rotational energy of Earth, also shearing of various layers Believed to be occurring within the earth.
However It could be viewed that these energy transfers are not small, given the 0.2 of a milli second daily fluctuations occurring to the LOD  equates to approximately
10 x10 ^20 joules variation in kinetic energy, raises the question how does it appear that over time the length of day stays within such a tight range ??

[Bored chemist]

It's about 30 seconds drift in about 60 years

https://en.wikipedia.org/wiki/Day_length_fluctuations#/media/File:Deviation_of_day_length_from_SI_day.svg

Alan seems to have realised he's wrong, but isn't prepared to admit it.

[gem]

Did you notice the 3 milli second daily variation annual range On the link you provided.
On the data I have it looks like it’s peak this Hemispheres, summer is - 1.4599 milli seconds, and will anticipate a plus figure similar in early January.
Or approximately equivalent to Plus or minus 70% of the solar energy received just to put a scale on the variations in the energy to earth’s rotation.

[Bored chemist]

It would be interesting to calculate the effect of our orbit.
When we are near the Sun we are, I guess, hotter. That will slightly expand the atmosphere and temporarily alter the moment of inertia.It should mean the Earth spins slightly slow when we are nearest to the Sun (Early Jan, I think)