It always seems that sunsets are accompanied by a few or a cluster of clouds, near where the sun drops below the horizon line.
I s this a real effect or just an impression?
You would have to demonstrate the reality of your assumption first. It MAY be true, but I can’t really say that I can go back into my memory to find sunsets I’ve seen and be able to tell how many had clouds and how many didn’t.
Now, it’s possible that it seems that way because when you look at the sun at noon (hopefully not directly), you’re looking at it through a relatively thin layer of atmosphere, only that column of atmosphere directly above you. But when you’re looking at the sun at sunset, you’re looking through the atmosphere at an acute angle, so actually looking through a much greater distance of atmosphere than you were at noon. That additional atmosphere is going to distort the image of the sun much more than the relatively thinner straight-up-into-space noon atmosphere did. And, similarly, you’ll see more clouds since you have more opportunity to do so through the thicker slice of atmosphere.
I don’t have a definitive answer, but if you start by looking right above you, and then start moving your view to the horizon, as you get closer and closer to the horizon you are seeing through longer and longer stretches of sky, so the chance of a cloud being in the way increases…
(Edit: Damn, jayjay beat me.)
There’s also a selection effect, in that sunsets with clouds are prettier than clear sunsets, so when you see one, you’re more likely to remember it if it has clouds.
This would also depend a great deal on your location.
I dunno. I once had a girlfriend who was convinced that dust in a room was attracted to the sunlight coming in the window though.
I can top that. I knew a guy when I was young who would point out that the ingredients of Coke included acid and believed that was why a warm Coke would melt ice placed into it.
You can’t make up stuff like that.
I not sure I understand the question. Are you wondering how clouds can appear around a sunset? If so, they just so happen to be the clouds hanging over that part of the ground. Those are the clouds that are visible just before they start to tuck behind the curvature of the earth.
So, in that regard, clouds are as common as clouds in any other part of the sky, but as said, when you look toward the horizon, you’re looking acutely through much more area of sky than that right above you, so the chances of there being more clouds around the horizon would be greater I think.
You can’t possibly mean to imply that clouds are somehow attracted to the sun? (since those same clouds you see on the horizon, are actually hanging above someone else’s head, miles away.)
Well, there might be one effect that actually could make clouds follow the sun:
Cumulus clouds are created during the day by sun-fueled thermal updrafts and disappear in the evening when the sun gets weaker.
Further West the evening is not quite as late so there might be more clouds left.
Of course you’d notice it only if you can look very far, and the selection effects mentioned above are far more important, I guess.
Yeah, but it’s not necessarily sunset there.
You could prove this pretty easily by using satellite pictures, if the OPs premise is true you should see a band of cloud moving around the Earth in step with local sunset. I’ve never seen anything like this in general.
If you look at the horizon at any time of day, you’re likely to see clouds even if it’s clear overhead, simply because you’re looking through maybe a few hundred miles of atmosphere, so if there are any clouds in that distance, you’ll see them (visibility permitting). It’s pretty rare that there are no clouds at all over a distance that great (especially in the UK!) so chances are you will see clouds towards the horizon.
That would imply clouds racing around the world at 1,000 MPH at the equator, which defies common sense to say the least.
There’s no need for it to be the same cloud, it just implies that new cloud would be forming at that rate, the point is that you don’t see this effect in satellite images so the OP is probably just seeing the visual illusion of more cloud described by others.
At sunset, you’ve had a full days worth of heating. The warm air near the surface will rise, producing instability in the atmosphere which produces clouds. It’s why hot air balloons are launched early in the morning, and why the nastiest thinderstorms happen in the late afternoon.