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The Rain and the Sea: Newsletter Challenge (January 2012)

Posted December 31, 2011 12:00 AM

This month's Challenge Question:

An old adage among seafaring people states the rain calms the ocean waves. Is this really a true statement?

And the answer is:

When a raindrop hits the surface of the ocean it causes the water surface movement to be disrupted, causing waves to be generated. This added energy makes the surface of the ocean become turbulent. This turbulence causes destructive interference to the waves with shorter wavelength.

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#1

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

12/31/2011 3:37 AM

Maybe the rain breaks the surface tension and adds a layer of different density near the surface which alters the mechanics of the wave.
Or maybe it's simply that conditions conducive to some types of rain are not conducive to high waves. I havn't studies wind paterns related to the passing of cold front or depressions.
I dunno, maybe tea and toast will help?
Del

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#2
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

12/31/2011 4:37 AM

I've just remembered - the GW alert bucket in my garden has not been checked for months. Last top-up from the sea was at least August . I'll lean out the window and top it up for re-callibration .

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#26
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 3:05 AM

It didn't work for the Boston Tea Party, but the thoughtful addition of toast may just turn the tide (so to say).

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#3

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

12/31/2011 4:42 AM

Rain implies a storm, and that would seem to imply heavy weather. So, that's clearly wrong. I just watch the seagulls - they come inland when it's rough. Arrr!

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#14
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 9:20 AM

And what about the "Silence after the Strom"?

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#38
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 12:13 AM

it's the Eye of the hurricane

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#4

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

12/31/2011 4:55 AM

I thought it was oil that soothed the troubled waters...the idea being that the oil prevents wind from picking up water drops that would make harsh spray.

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#5
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

12/31/2011 7:50 AM

That's why BP did you a favour.

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#34
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 8:11 PM

That was Benjamin Franklin's hypothesis but I don't know if it has been accepted yet. Small ripples do get damped.

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#6

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

12/31/2011 10:35 AM

How is this try?

Waves are, in part, whipped up by the winds. The wind consists of moving air. The moving air has kinetic energy. The rain is more dense than the wind. The wind loses energy to the rain by accelerating it in the horizontal direction. Removing energy from the wind slows it down. A slower wind whips smaller waves.

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#21
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 1:11 PM

You are probably the closest to the reason than anyone, but it is actually the turbulence caused by the rain striking the water surface that helps inhibit medium wave formation.

I am not sure of the exact physics in play. Hazard a guess?

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#36
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 8:31 PM

The theories of wave growth I read were not terribly convincing: Raleigh - sheltering theory, Phillips - turbulent winds. I would like to know if large waves grow more from the direct forces of the wind on them or by absorbing smaller waves that are whipped up along their sides. If it is the later then inhibiting the small waves would inhibit larger growth. Is the stilling effect just smoothing the surface of the large waves but not affecting their overall amplitude or are the large waves being noticeably damped themselves? I don't think a turbulent layer would affect their size much so it would have to be in reducing the amplitude of the wind that drives the waves and then viscous damping causes them to decrease. This later process is slow.

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#37
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 9:26 PM

I like it!

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#39
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 12:17 AM

(big) waves created by wind and rain and created by wind without rain, but not created by rain without wind

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#80
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 12:16 AM

and not created without wind and without rain (expected tsunamis)

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#103
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/10/2012 6:15 PM

I think the combination of the turbulence created by the ripples from the raindrops and the added mass of the rain itself act as a damping force to the wave action. I suppose the electronic equivalent would be a damped oscillator with an added noise component.

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#7

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

12/31/2011 2:40 PM

Does it not create a high pressure area with air then having to flow out-wards and oppose and calm the oncoming rough waves?

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#16
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 10:33 AM

As I understand things, in the Northern Hemisphere, a large, high pressure area (an anticyclone) rotates clockwise and usually brings clearing skies, lower temperatures and drier air.

The large low pressure area (a cyclone) rotates in an anti clockwise direction. It sucks warm moisture up into the clouds and deposits it as rain. Something like a widespread hurricane.

Wind is developed when there is a steep pressure gradient, when a cyclone and anti-cyclone approach each other, the steeper the gradient, the greater the wind velocity.

I don't know how this helps with the challenge, though.

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#8

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

12/31/2011 10:45 PM

There is more than one reason for the saying. One of the reasons is: Assuming the rain is falling, there is a somewhat of a downdraft and sometimes a serious downdraft. As the air can't move in two directions in the same place at once, you would no longer be in a fetch area or at least not in as strong a fetch area. Therefore you are dealing with swells and not waves. Swells that are no longer being built would of course be somewhat less than waves still being built. Therefore under most conditions the statement would be correct.

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#9

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 12:23 AM

As one who spent decades offshore, in all kinds of weather including 10 hurricanes (one of which was a cat 5), I can say that rain has NO effect on seas, that I observed. However, wind can have a calming effect on waves, when anchored on the Wapoo River, in Charleston, SC, just before the eye wall of Hugo passed our position, the wind was blowing so hard that it flattened the waves, but they began to build again as the other side of the eye approached (needless to say that rain was torrential except in the eye).

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#10

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 7:34 AM

Another reason may stem from the fact that whenever a warm front moves through, the rain follows the front and as it gets further away the wind dies down as the pressure goes back up. The question asked if it was true that the rain calmed the ocean waves. My answer is that the conditions that accompany the rain often do. In my last post I said the reason I gave was true in "most conditions". I should have said that it was "often true". I really don't know about "most." As an old sea dog from the middle of last century, I never heard of the adage. Also after several years work in the US Weather service I still never heard it. I guess I don't get around as much as I thought.

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#29
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 10:54 AM

I have to agree since I never heard of it during my years at sea back in the 60's. I can still vividly remember being in the north Pacific trying to skirt a typhoon with 25 foot waves crashing over the bow and rain falling in torrents and I never saw the waves decrease one Iota till we were well out of it.

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#11

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 7:37 AM

Simpler would be a spring-mass system in a vertical arrangement, if mass and impulse are added depending position and speed of the system at the moment of the join the mech energy would be increased or decreased: zero as average?.-

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#12
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 7:42 AM

Huh?

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#27
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 8:21 AM

That is interesting. Sometimes when I'm reading a post, I realize about half way down I have no idea what I'm reading. So, I start back at the top only to discover, at the moment of the join, there is something cleverly (and likely intentionally) wrong with the word arrangement.

Well done ferquiza. Well played.

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#32
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 7:56 PM

Hi A, please don't believe for a moment my post was guided at all by a second purpose, i believe, really i do,not other target of the challenge, if the total mass and impulse of rain on an oscillatory system (as the waving sea here) should increase or decrease its mechanical energy: rains on the top as the valley: i didn't find reasons for changes. Challenge is not about winds or so.-

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#33
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 7:59 PM

Somebody is really fast here: i got score 5 for off the topic at the same time appear my post, any explanation for that?

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#35
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 8:24 PM

When you reply to an off topic post, your post is automatically deemed off topic by the system - unless you un-check the box provided.

One would think some 300 post in, you would have noticed that - not be thinking it was 'somebody'.

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#76
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 8:39 PM

sorry, i apologize.-

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#43
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 9:28 AM

Already posted, sorry.

If you reply to an off topic post, you automatically give yourself 5 off topic points, unless you remove the off topic "tick"..

Or you can mark yourself off topic, which will have the same result!

I remove the tick when answering you so that I start with 0 points.

Read all before clicking on anything!!!

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#13

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 8:26 AM

Surface Tension effects would be my guess. As with using oil, dispersed via a canvas bag, the surface tension of the water is so increased by the "oil-slick", that the waves do not break and slosh over the boat but remain solid, staying in tack, and slide under the hull... hopefully. The rain, similarly, would give a layer of fresh water at one temperature over salt water at another temperature, creating a boundary layer giving somewhat the same effect.

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#18
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 11:42 AM

From my personal experience (deep sea yacht captain for forty years), Torrential rain, which relatively few people have experienced, does indeed have a calming effect on sea state, as does oil, or even a "slick" created by a vessel drifting sideways. One must realize that it is the breaking tops of the waves that are most discomforting and indeed damaging to a small vessel. Swell, no matter how large, is of no significance to a little chip of a boat; breakers however can and do overwhelm the small boat. Heavy rain does indeed "knock down" those dangerous tops, leaving the sometimes huge swell to slide harmlessly by under the boat. The flip side however is that breakers are created by the steepness of the wave front and in truly bad conditions rain alone is not going to produce a significant improvement. The sheer power of a large wave is not to be controlled by rain alone. The best place to be in those conditions is to be sitting under a tree! :-)

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#19
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 11:56 AM

or even a "slick" created by a vessel drifting sideways

One of my favorite reads was Patrick O'Brian's tales because of the minute details he could get packed in.

One of those being dropping sail and setting an athwarts sea anchor to take small boats aboard in heavy seas in the smooth water created by the larger ship.

Not bad for a 20th century author.

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#20
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 1:03 PM

I couldn't agree more; O'Brian definately knows a bit about the sea!... I have used a small "cargo" parachute instead of the cumbersome old style sea anchor and it works like magic!... Dry decks in extreme weather, unless one allows the boat to move ahead or astern of the slick, then all hell resumes.

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#81
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 12:40 AM

And a pleasure to meet you Cap'n

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#22
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 1:13 PM

You wrote, "The best place to be in those conditions is to be sitting under a tree! :-)"

Not in a lightning storm! :-)

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#23
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 2:45 PM

Its also a good fix for seasickness......

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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 9:16 PM

LOL

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#15

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 10:07 AM

A way to look at this question is the way a sailor treats it.

An old seafaring adage is:-

"When the wind comes before the rain,

soon we will be wearing topsails again". (many different versions are around!)

So I think that in many (but certainly not all) cases the rain appears to calm the storm because as the rain starts, the wind drops.

Conversely when the rain comes first, its less likely to calm down.....

I looked around and found this delightful website with regard to Folk Lore Weather Forecasting, it is easy to read and I feel very informative:-

http://tww.id.au/wea/forecast.html

Best of luck, happy new year to all.

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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 10:38 AM

Great link Andy!

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#25

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/01/2012 11:20 PM

I've spent a bit of time on the sea and have noticed that the calming effect is dependent on the angle at which the rain falls.

The effect varies from:

being locked in irons, when the rain is coming straight down

to

screaming "what were we smoking when we decided to come out in this???!!!", and raining generally upwards.

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#28

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 9:39 AM

Capillary waves give the small textured surface on waves that prevent them from reflecting smoothly. These are driven by surface tension not gravity. Impacts of large droplets would be enough to break these up.

As a secondary point, the motion of waves are moving back and forth at ~a*omega where a is the wave amplitude and omega is its frequency. The rain deposits a layer of water that is not part of this irrotational motion so enhances the shear drag on the wave. When the depth of water deposited is comparable to the wavelength of the wavelets on the surface they will be strongly damped.

I think the strongest effect will just be altering the turbulent motion of the wind over the surface of the waves that roughen their surface. Waves are driven by the wind but the wind is also significantly altered by the changing surface of the waves. Droplets are much more dense than air and drag appreciable air with them. (This is the real reason your shower curtain gets pulled in when you turn on the shower.)

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#41
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 12:32 AM

Actually it's the warm air (as warmed by the falling water) which creates an updraft--try using cold water which will blow the shower curtain outward.

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#42
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 1:05 AM

I'm pretty sure that was generally refuted some time ago but I think that individual configurations may have different effects dominate. http://www.scientificamerican.com/article.cfm?id=why-does-the-shower-curta

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#44
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 9:57 AM

Actually I do believe the "shower curtain" effect is more to do with the electrostatic charge produced when water runs over the human body. I don't think that temperature of the water changes much, cold or hot.....

There are many wrong explanations on the web, nobody agrees with anything, but here is a good explanation as he also shows that hot or cold water does not change the effect:-

http://www.physics.hku.hk/~phys0607/lectures/chap02.html

He writes:-

The induced electrostatic charge

When water streams out a narrow opening such as the hole in a shower-head, it can pick up a static electric charge. Electrons can also be scraped off - or onto - the water by the shower-head, depending on what it is made of. But if the water's molecules are to pick up, say, a negative charge on their way out of the shower-head by picking up some negative electrons, those extra electrons would repel some electrons from the surface of the shower curtain, because similar charges repel each other. That would leave the curtain's surface with a deficiency of negative charge, and its inherent positive charges would dominate. The negative water and the positive curtain would then attract each other, as is the property of opposite charges, and the curtain would move toward the water.

Do remember that near to waterfalls, a huge amount of negative ions are produced, they are measurable with suitable instruments. Many believe that they promote good health and long life, which is why many buy small electrostatic ion generators to both clean the air in a house (they precipitate any smoke or dust particles out of the air) and give a clean smelling atmosphere.

A great test to make, if you know a smoker, is to get the smoker to blow a lot of smoke into a big plastic seethru bag with the ion generator in there but not switched on. Seal the bag, watch the contents and switch the generator on. The smoke is GONE in about 100th of a second!!!! It simply disappears....

Dust and dirt are negatively charged by the generator when used in a house and simply drop down and stick to the floor where a normal Vacuum cleaner will pick them all up!!!

The shower curtain is attracted in the same way as the dust to the floor.....

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#45
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 10:09 AM

Tap water is actually very conductive. It is not going to establish a static charge. There are experiments that show breaking droplets lead to uneven charge distributions depending on relative size (Feynman lectures II) but that is really a very weak effect. To generate at 0.01 N force over 1 cm you would need to separate ~10^11 electrons. At 1 per drop breakage this is too small.

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#53
In reply to #45

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:27 AM

You must try the ion generator producing negatively charged ions, its very impressive.

Here:-

http://www.negativeiongenerators.com/ionizer-dustgrabber-combo.html

there is a video demonstration......

Here you will find a paper on the levels of negative ions produced by waterfalls:-

http://www.atmos-chem-phys-discuss.net/6/9297/2006/acpd-6-9297-2006.pdf

I hope this attracts your attention to the effects......

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#56
In reply to #53

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:44 AM

I am aware of the negative ion effect around waterfalls and claimed effects on health and mood but there are nowhere near enough of these to pull a shower curtain.

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#57
In reply to #56

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:47 AM

Unless you try the effects personally, you may be mislead.......

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#59
In reply to #57

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:53 AM

I have experience with these but you seem be jumping to the conclusion that seeing an effect makes you electrostatic model correct. If you don't want to calculate the conduction rate in the water and want to do it experimentally, get a voltmeter with some long cables. You can use the previous estimates to find a realistic voltage which will certainly be readable on a standard meter.

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#60
In reply to #59

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 2:03 PM

I tried the "wind" method years ago, its certainly nothing to do with warm or cold air, I am 100% certain, it simply did not do the trick with the "clinging".....try it yourself.....

Measuring static charge is quite difficult without specialised equipment, it might be possible using a scope which has a very high input impedance, possibly......but I am not a static electricity engineer, my knowledge is very, very limited......I knew such a Guy years and years ago......but not anymore....he lives in the UK, not here.

By the way, the static voltages that can be achieved are quickly to tens or even hundreds of thousands of volts.......but no real current!!! Static has its own laws and problems....I spent a great deal of my working life getting rid of it in machines!!!

As an example, if you can see the spark from your finger after moving/walking over a carpet, you are achieving approximately 6,000 volts or more.......

I was recently (yesterday) laminating some a4 paper sheets in a hot laminator. Getting the plastic sheets apart to place the paper in the middle was REALLY difficult, they were charged up and sticking together, so the power is there to cling. These were only a4 sheets (about letter size), so has anyone else noticed that as well when laminating thin sheets of plastic?.....static has real "cling" power in such situations.....

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#61
In reply to #60

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 3:02 PM

You wrote, "By the way, the static voltages that can be achieved are quickly to tens or even hundreds of thousands of volts..."

If you ever received any electro-static discharge at those voltages you would never want to take another shower in your life!

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#62
In reply to #61

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 3:52 PM

You are demonstrating to have even less knowledge than I about static.

For example, put on a pair of shoes with composite soles on, not leather, on a dry day and scuff your shoes on a piece of carpet that has plenty of man made fibers in it.

Go touch a water tap or a radiator that is earthed.

Did you notice the shock? Of course you did.

How high was the voltage? Most probably more than 300,000 volts. Did it kill you? Of course not, though you may have not liked the jolt as the discharge happens in a few microseconds.

With the water the charge and discharge are far slower and therefore unnoticed and continuous.

Why not try the test I mentioned with a hair dryer, then in the shower with the water spray (leave the hairdryer somewhere else first!!)

But at the end of the day, please believe what you want to believe, I am certainly not interested in "converting" anyone to another "belief"!!

Many believe blindly something without any facts or experiment, I personally am not one of them.....I have done the experiments in a simple rudimentary manner.....what have you done to prove me wrong up to now?

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#63
In reply to #62

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 4:31 PM

Wonkipedia: "The maximum potential is limited to about 35-40 kV, due to corona discharge dissipating the charge at higher potentials. Potentials below 300 volts are not typically detectable by humans. Maximum potential commonly achieved on human body range between 1 and 10 kV, though in optimal conditions as high as 20-25 kV can be reached. Low relative humidity increases the charge buildup; walking 20 feet (6.1 m) on vinyl floor at 15% relative humidity causes buildup of voltage up to 12 kilovolts, while at 80% humidity the voltage is only 1.5 kV". The static charge has limited charge so the current of discharge won't last long and deposit much energy. If you were to connect to such a such a voltage with a conductor (as you keep refusing to acknowledge for tap water) you would indeed be zapped!

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#64
In reply to #62

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 5:23 PM

Perhaps not.

The typical static shock you feel is about 8,000 to 12,000 Volts, with 12 kV being pretty painful. The minimum you can detect is going to be about 2,000 to 3,000 Volts.

Another clue that 300,000 Volts is a little large is that normal air has a arc breakdown of about 10,000 Volts per cm. That would mean a 300,000 Volt potential would have an arc length of 30 cm! Ask yourself when the last time you saw a 30 cm arc coming out of your fingertip!

When I worked in the appliance industry we would test ESD at a maximum of 24 kV. That is overkill because if you ever got that kind of a jolt touching an appliance you would be in severe pain. I watched one engineer who insisted that it was nothing volunteer to get a 22 kV jolt and he involuntarily leaped backwards. That also changed his mind about what was tolerable. ;-)

Back to ESD as a cause to drive the shower curtain. If the threshold for human detection of an ESD discharge is 2 to 3 kV, then I would think a wet shower curtain would not be impacted much at all at those potentials or less. It may cling to your body (and therefore play a part in the observed effect), but to drive a heavy wet plastic 10 to 25 cm from its resting position to your legs would require a pretty large field charge.

I am still thinking that the predominant force here is an air pressure gradient.

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#68
In reply to #64

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 5:38 PM

Agreed. We are way off topic from the original blog entry or I would give it a "good answer."

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#69
In reply to #64

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 6:59 PM

As I believe I mentioned before, I have no practical method measuring the voltages....

But it appears that many of you are mixing generated high voltages and static, they are not really the same. The static has infinitely tiny "power" levels, so don't mix up the two, its easily done.

as of this moment, there are two schools of t6hought, air movement due to vortexes generated by hot water or static.

I proposed a test using a hairdryer, nobody appears to have tried it......

A further test might be to seal off above the shower curtain and use a fan to remove the air and see how far the shower curtain moves inward. I personally don't believe it will move as much as when water is flowing, anyone care to try and prove me wrong?

By the way, the vortex idea would need to be strong enough to allow a human to "feel" the air movement. I have tried that also, there was basically nothing to feel, no noticeable air movement at all.....but my wife was securely "stuck" to the shower curtain.

It is sad that we have a hard plastic shower door (many years now) and no curtain (my wife hated it) or I would redo some of the tests with a video camera....

But as I said before, believe what you want, but a few simple tests might just change your mind!!!

Have a great day, but I do feel we have used this blog long enough.......and no waves!!! At least in the bathroom......

Remember, believing something without any proof is just religion.......in fact ANY religion that I have heard about, so its quite widespread!!!

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#72
In reply to #69

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 7:26 PM

You wrote, "As I believe I mentioned before, I have no practical method measuring the voltages..."

Well, I do have some experience with van de Graaff generators, ESD guns, and Tesla coils and know very well how much potential Voltages are involved. 300 kV is way, way too high.

You wrote, "I proposed a test using a hairdryer, nobody appears to have tried it......"

I have glass sliding doors, so I can't replicate the experiment. Otherwise I would.

As for shower curtains sticking to your wife, I suspect that being wet will do the same thing. Once the plastic makes contact I think van der Waals forces will do the rest when wet. Or, maybe your wife is more attractive than you have let on. ;-)

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#83
In reply to #72

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 8:49 AM

Van de Graaff machines, even quite small ones can produce deadly levels of voltage/current at powers than can kill or maim.

They also do not work well in wet areas. In fact some may never work again after getting wet.....

ESD guns and Tesla coils suffer similarly with regard to power and water.....

This is therefore completely the wrong way to go or even to consider thinking about......patently such ideas do not hold water!!!

Can you see that now?

I am REALLY surprised that such flawed thinking as demonstrated here actually is from fellow engineers......without a single valid test idea from any of them!!!!

Simply, that is not how good engineers think (or even bad ones!!!)

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#87
In reply to #83

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 10:01 AM

Let's get on track.

My post deals with ESD levels in the human body. There are plenty of scholarly articles on the web that you can Google to confirm my point.

I was simply replying to your claim that human ESD voltages of 300 kV is in error by over an order of magnitude. This is not an offense against you, just my informed opinion on the subject of ESD and the maximum human potential.

On the subject of whether ESD or static charges are the main force driving the movements of shower curtains, I have less of an informed opinion, but I am thinking that it may not be the largest factor.

My reasoning is that:

1. I can't find any information on static charge build up while showing on the web.
2. High humidity tends to dissipate static charges before they can accumulate. Here in Florida ESD is almost non-existent except in the coldest of winter when the heat is actually on.

If you have some articles that relate to #1 above I would really be interested in reading them.

I found this link on the web that seems to support prevailing claims here that it is the horizontal vortex effect of air surrounding the water spray. The low pressure gradient inside the vortex drives the curtain inward.

The author also empirically tested hot and cold showers with the results being similar, but with a diminished effect for cold water. This tells me that the actual effect is a collection of several factors, with the sideways vortex probably being the dominant factor, but not the only one.

Lastly, please don't take our arguments too seriously. They have nothing to do with you personally as you are one of my favorite characters on this forum. ;-)

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#90
In reply to #87

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 12:07 PM

My personal take is that its related to the waterfall charge effects and I posted a link where a study (the first ever I believe) that purports to document what happens. Just look back at my previous posts for the link. nobody appears to have read it fully other than myself!!

Here it is again, it is well worth reading and provides much more scientific opinion than any of the other posts here.-

http://www.atmos-chem-phys-discuss.net/6/9297/2006/acpd-6-9297-2006.pdf

I am still of the opinion that the phenomena is charge related, but this particular area of research appears to have been very poorly addressed over the years......

The pdf did not even exist when I did my tests about 20 years ago.....

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#75
In reply to #69

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 7:45 PM

If..... "no practical method measuring the voltages...."
and you believe the voltage to be in the order of 300,000...
Then..."believing something without any proof is just religion"
Is this your religion??? ;-)

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#85
In reply to #75

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 8:57 AM

Could be!!

Its certainly no worse than any other.....

I was actually quoting (badly) from memory from this website.....I got an extra zero in the mix!!!! Sorry.

http://www.esdsystems.com/whitepapers/wp_carpet.html

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#67
In reply to #62

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 5:35 PM

Quite noticeable, is Van der Graaf generators perform poorly in high humidity.

So far as I know there are zero case of electric shock in bathrooms, even in the GRP module ones, attributed to static. Faulty earthing practices and misuse of appliances are a separate issue.

Have you experimented rubbing your shoes on that carpet when it is damp?

Have you tried it in a steamy bathroom?

I think you will find what applies in the living area of a centrally heated house, particularly in winter, does not transfer to the saturated environment behind a shower curtain.

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#71
In reply to #67

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 7:23 PM

One last post as I see you have convinced yourself in a direction, without any formal thought on the subject, not my problem......

Falling water (as I cited in a pdf which you obviously ignored or did not read) produces strong negatively charged ions.......that is why the charge is developed.

Don't get stuck on dry room static, because patently its not quite that!!!! That is obvious to any one here....

The shower water produces a strong negative charge on a human body. This attracts the plastic curtain. Its as simple as that......

To stop the effect, just wetting the side of the metal bath prior to taking a shower and sticking the bottom of the curtain to the side of the bath, seemingly shorts out the difference in charge and reduces the attraction to basically nothing....Can someone try that also please.

Note, it may not help on plastic or GRP baths, but it does work on metal ones.... I have never had a plastic one myself, so I don't know for certain, or a plastic bath either.

I will not be posting anymore on this subject as I have done my best, but as nobody seemingly has the interest or the possibility to test, its rather like flogging a dead horse....let us agree to disagree....bye....

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#77
In reply to #71

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 9:32 PM

"Don't get stuck on dry room static, because patently its not quite that!!!! That is obvious to any one here...."

Then why did you raise it?

To answer your other questions;

Metal baths have one of several coatings all of which are insulators in the megohm range. At best there would be some capacitance, but no earth. Anymore than there would be earthing via water running down PCV drains.

For what its worth, I spend a lot of time in hotels so have a comprehensive experience with shower curtains, types shower and shower-bath. A wet curtain will stick to any bath or tiled surface.

A free hanging curtain, short of the floor in a cubicle will waft in if drawn full width - and not if not drawn fully.

Many curtains have weights in the hem to limit this. However the best curtains are double layer, where the heavy fabric outer sits outside the bath rim and the waterproof layer inside the rim. Because the outer layer cannot 'suck in' the inner layer just hangs there in the 'wind break'.

And I did consider your "falling water" theory, but like others above, found the forces insignificant.

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#78
In reply to #62

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:57 PM

what voltage does the electric chair need?

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#46
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 10:24 AM

An easy test is to turn on the shower with no one in it and see if pulls the curtain in.

I was at a relatives this Christmas and noted that they had a shower curtain. I would open the far end of the curtain a little and the problem all but goes away. This would tend to reinforce the idea of airflow or a pressure gradient as the mechanism at work.

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#47
In reply to #46

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 10:27 AM

I'll buy into the pressure gradient theory :-)

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#49
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 10:29 AM

You know, this would be a good challenge question. ;-)

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#55
In reply to #49

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:43 AM

Good idea.

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#50
In reply to #46

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:06 AM

It certainly is a pressure gradient. You can actually see the flow of steam around the room in some cases. The long standing debate is whether it is from heating (Stack effect), vortex force of droplets or the Coanda effect. As a granular materials guy I like the second one. You can show that each is enough to move the curtain on its own (but Coanda effect is short range) in some cases. I think that for different curtains, tubs, jets and bathroom shapes different ones may dominate. Clearly we need an NSF grant to map out the phase portrait here!

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#54
In reply to #46

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:41 AM

If you have a thin plastic shower curtain, and you stand in the shower and let it touch you while showering (hot or cold), you will find that it "clings", like a second skin. It is almost "glued" on in quite large areas....it will be the lower part of the curtain that is affected most.

Using a hairdryer on cold, but no water running does not produce the same clinging effect, only where the jet is directed, small areas.....been there done that maybe 20 years ago...at least.

A thick plastic curtain does not work as well, too heavy I guess, the cling effect is still there, but not as clearly as with a thin one......we are only talking about electrostatic effects......

If you don't try the experiments, you will not understand what I am talking about......

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#79
In reply to #54

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 12:09 AM

try the same with a haired body

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#86
In reply to #79

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 9:05 AM

Can you detail why please?

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#93
In reply to #86

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/07/2012 11:13 AM

will not work that way

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#94
In reply to #93

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/07/2012 11:18 AM

Understood, its a thought process not a fact of life.....

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#65
In reply to #46

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 5:25 PM

Precisely AH

Turned on and cold with no one in there, you have a venturi effect down draft, producing a pressure gradient behind the curtain. Generally an"S" form, in at the top and out at the bottom.

A body reduces/negates, this venturi effect, and generally the water then is 40 C +

producing a thermal updraft (presuming the room is below 40C)

A slightly open curtain allows inflow, negating the thermal pressure gradient 'sucking' the curtain inward.

The effect is noticeably greater in a cold room and noticeably less as the room heats up.

It's 101 thermal and pressure gradient stuff

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#82
In reply to #65

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 12:49 AM

I seemed to have started quite a discussion that had little to do with the original question regarding rain and its effect on waves.

However, regarding the shower curtain, I offer the following. I take a shower in the morning and the bathroom is a long way from the hot water heater. So I turn on the water in the shower with the handle all the way over to hot to let the COLD water flow while I sit on the toilet. The curtain blows outward until the HOT water arrives at which time it then blows inward. By then I have finished my business with the toilet and I then adjust the temperature to my liking and climb in. The only change has been the arrival of the hot water. I'd send a video but I'm not usually dressed for the occasion. I've repeated the experiment numerous times and believe that the effect is simply caused by the density difference between the air in the shower and that in the rest of the bathroom.

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#30

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 10:57 AM

If seafarers believe it, it must be true.

Excellent examples of the calming effect from 1:10 to 2:00 here

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#31
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/03/2012 1:58 PM
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#91
In reply to #30

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/06/2012 12:20 AM

I see no calming effect between 1:10 and 2:00... And the fact is, those frames depict different boats, therefore no "comparison" of effects is valid... As a long time yacht skipper, I would not trade places with any of those boats :-)

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#92
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Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/06/2012 2:20 AM

I see no calming effect....

No kidding.

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#40

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 12:25 AM

did you told your grandma so? remembering the sail to america?

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#48

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 10:29 AM

Rain will suppress the formation of small and mid sized water waves. Large waves propagate from the energy of ever increasing smaller waves as well as the wind.

So indirectly, rain can help slow or stop large waves from forming.

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#51
In reply to #48

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:07 AM

Hey I like this comment. Can you give me a reference for the second statement? I need closure.

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#52
In reply to #51

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:25 AM

Sure. Here is one I found. Twenty years old, but some references are therein.

Welcome to CR4 cchaf. I see you have been a member for a while but an infrequent poster.

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#58
In reply to #52

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 11:49 AM

I like the reference and thank you. I know that the methods of wave growth have been argued for some time. Maybe this will lead me to a better understanding. Some of the wave theory out there is very "mathy" but conceptually poorly thought out. I talked to a researcher who told me no one can get money for this anymore so research is pretty stalled. I only post when I know something about the subject and it interests me. Hope they keep coming up with interesting puzzles!

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#66

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 5:26 PM

I can't cite the source, but as I recall there was some research regarding this.

In essence what it said was that the rain breaks up the medium sized waves. The medium sized ones are the ones that transfer the wind energy to large waves. The end result is a less violent sea.

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#70

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 7:22 PM

Water consists of loosely bound molecules and the very assemblage of these molecules

unites to create waves. Rain drops are also made of molecules. So when they fall with a certain velocity over the waves they disturb the molecular density and pattern of molecules in the waves, This is why the intensity of waves tends to subside.

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#73

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 7:29 PM

Here is a detailed answer which a friend of mine dug out from the oceans!.

One summer four and a half years ago, meteorologist David Atlas was sailing in Buzzards Bay, off Cape Cod, when a storm suddenly came up.
"The waves were about one and a half feet high at the time, ... and we thought we should batten down the hatches and get ready for intense rain," he recalls. "But to my utter surprise, as soon as the rain started, the sea became glassy and perfectly calm, except for the little ripples generated by the drops themselves." Atlas had witnessed something described by sailors for centuries: namely, that rain can calm choppy seas. But Atlas, a visiting scientist at NASA's Goddard Space Flight Center in Maryland, has now found scientific confirmation of the phenomenon - as well as a possible explanation. After the incident in Buzzards Bay, Atlas combed through radar images of Earth made by a European Space Agency satellite, the ERS-1. One image showed a storm off Cape Hatteras, North Carolina, in July 1992. Atlas combined this image with ground-based radar data showing the amount of rain that had occurred at that time and place. The ERS-1 doesn't send its radar beam straight down at the planet; the beam is directed off to one side of the satellite's path. The strongest echoes sea was rough under most of the Hatteras storm, and Atlas found that those radar-bright areas coincided with areas of little or no rain. The waves had been flung up by a downdraft fanning out from the center of the storm. But in the storm core itself, where the rain was heavy, Atlas saw a dark hole in the radar image - a three-mile-long, 1.5-mile-wide zone that hadn't sent an echo back to the satellite at all, because the radar beam had just skipped off the flat, glassy sea like a stone. How does rain flatten a sea? Waves, Atlas explains, are an organized, coordinated motion of water. But when a raindrop enters the water, it first creates a splash, and then an eddy. "Now imagine a lot of raindrops doing this," Atlas says. "When you have a bunch of these eddies, that is disorganized turbulence, or random motion, and the turbulence interferes midi the organized wave motion. The rain is simply stirring the water underneath, and when you stir the water, you kill the waves."

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#74
In reply to #73

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/04/2012 7:38 PM

The problem I have with this explanation is that the vorticity transport theorem ensures that the irrotational motion of the waves should be largely decoupled from this turbulent rotational motion. A localized downpour would generate radially outwards winds that would often be counter to the prevailing driving winds and sympathetic wave motion. Maybe this plays a role.

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#84
In reply to #73

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 8:55 AM

GA.

That is as good an explanation/observation/validation of the effect that I have seen here, many thanks.

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#95
In reply to #73

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/07/2012 1:59 PM

Going by the following discoveries it may be said that , apart from other factors such as velocity of rain drops, agitation and subsequent depression caused by rain molecules in the moving waves, the size of the rain drops too plays a vital role in calming down the seas. Heavy the rainfall and bigger the rain drops they break the motion of the waves, disturbing their pattern, thereby calming the sea.

''One can add to the list of the fully explained: the hue of the sky, the orbits of planets, the angle of the wake of a boat moving through a lake, the six-sided patterns of snowflakes, the weight of a flying bustard, the temperature of boiling water, the size of raindrops, the circular shape of the sun. All these phenomena and many more, once thought to have been fixed at the beginning of time or to be the result of random events thereafter, have been explained as necessary consequences of the fundamental laws of nature-laws discovered by human beings.-By Alan P. Lightman''

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#88

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 10:34 AM

Calms the "Ocean Waves". Not many sea-faring sailors would consider 1 to 1.5 foot waves, as real waves. That's damn near calm. 5 foot would be standard and over 10 is what I had imagined was the topic of this challenge. Are we talking ripples or breakers? The cause and effects will vary dependent on all contributing factors at any one moment.

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#96
In reply to #88

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/07/2012 3:23 PM

Ahhh! Now we're getting to the nitty gritty of this mystical calming effect!... I would say that indeed, ripples will be easily "knocked down" by raindrops, but real waves (seas, in nautical nomenclature) are not as easily explained... I am not an engineer by any means, just a simple sea captain of forty years (ocean-going sailboats) and have no "scientific" explanation of what I have definately observed.... Heavy or torrential rain does indeed have a calming effect on quite large seas and is very welcome in a gale at sea, besides being an opportunity for a decent fresh water bath :-)... I doubt the effect would be observed by someone aboard a large ship as said large vessel is more stressed by seas hefty enough to produce hogging stress, which can damage a ship enough to actually cause her demise... Small craft simply climb up and over such seas and are mainly distressed by the breaking crests etc. Truly heavy rain damps these crests, even while the wind continues unabated.

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#89

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/05/2012 11:30 AM

I asked my kois in the frozen pond: Yes it can be and it can be not!

If the wind is calm, the raindrops induce turbulences down into the water, stimulate the water surface to oscillate or/and cause smal drops to splatter above.

All this activities make the upper layer of short waves turbulent and damp the waves.

If the rain, driven by a strong wind falls very slantwise, rain and wind can boost the short waves.

My kois love rain without wind!

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#97
In reply to #89

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/07/2012 10:39 PM

Can your Kois hear you through the ice cap on their pond?

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#98
In reply to #97

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/09/2012 2:54 AM

Yes they can!

Right now, the winter in central Eurpoe is very mild........and I could see their smile through the thin ice cup while it starts raining

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#99

Re: The Rain and the Sea: Newsletter Challenge (January 2012)

01/10/2012 12:14 PM

I believe the solution to be analogous to shot peening. The higher energy rain drops displace the water and since the wave crests are already seeking equilibrium the effect is to flatten the waves. I will leave it to someone else to do the MV(2) vs. M math.

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