Forms of weather and life of long day/night planets?

[Flyndaran]

Another thread taught me that temperature changes can get more extreme than I expected for long day/night cycles.
So I wonder how weather, life, and hypothetical aliens would evolve on such worlds.
I know that atmosphere mass greater than Earth's would dampen extremes, but not by how much.

For worlds with full day/night cycles of 48, 72, and more hours long?
Atmosphere masses of 2, 4, and more times that of Earth?

What unexpected and interesting ways would aliens have to evolve to cope with such massive rapid extremes?

[Anthony]

In general, temperature swings are milder near the ocean, due to the buffering effect of large amounts of water, and that would remain true. High desert areas can already have diurnal temperature variations of 50C or so, and that would get worse (both in the day and at night, but probably more at night, daytime temperature is naturally self-limiting).

[Flyndaran]

What do you mean by self limiting? Why would daytime highs be less extreme than nighttime lows?

I can't find an example of a desert that drops 50 C regularly over 24 hours. But copying hot desert life's behavior certainly sounds reasonable to keep in mind.

Not many animal(oids) without burrows in which to weather the extremes for which they aren't adapted. Ouch, trying for nice grammar lead to one awkward sentence.

[Anthony]

Originally Posted by Flyndaran

What do you mean by self limiting?

Daytime temperature rises until the rate heat is radiated away is equal to the rate it comes in, or the sun sets.

Over its entire surface, the planet is capturing light across an area of pi r^2, and radiating heat across an area of 4 pi r^2, so it needs to radiate at about 1/4 the intensity of sunlight to retain constant temperature.

A flat sheet normal to the sun, insulated on the back so it only radiates from one side, needs to radiate at the full intensity of sunlight to retain constant temperature. Because blackbody radiation varies as the 4th power of temperature, this corresponds to a temperature of 1.414x the mean planetary temperature, which for Earth limits things to around 250F.

[Flyndaran]

Ok. Circle vs. sphere issues. Now that's another thing that is not remotely obvious to laypeople like me.
As it relates to the entire planet, atmospheres would have little to no effect being such a tiny fraction of the whole.

Not that that ceiling is nice to anything living of an earth like nature. Even anything water based wouldn't exactly like air temps above the literal boiling point.
Then again that assumes earth like air pressures. Simply doubling it would allow water to stay liquid at 250 F.

So that would make Earth's mean temperature about 40 F?

[whswhs]

Originally Posted by Flyndaran

Ok. Circle vs. sphere issues. Now that's another thing that is not remotely obvious to laypeople like me.
As it relates to the entire planet, atmospheres would have little to no effect being such a tiny fraction of the whole.

Not actually true. The atmosphere plays an important role in distributing heat around a planet's surface, largely via convection. Remember that the part of the planet that living beings inhabit is only a tiny fraction of the whole, too.

[David Johnston2]

Originally Posted by Flyndaran

Ok. Circle vs. sphere issues. Now that's another thing that is not remotely obvious to laypeople like me.
As it relates to the entire planet, atmospheres would have little to no effect being such a tiny fraction of the whole.

The stuff that happens a mile underground is however, not very significant to us. We live on the surface and the air affects us.

[Flyndaran]

Originally Posted by whswhs

Not actually true. The atmosphere plays an important role in distributing heat around a planet's surface, largely via convection. Remember that the part of the planet that living beings inhabit is only a tiny fraction of the whole, too.

That would lower the "ceiling" for highest daytime high though, which doesn't change what I meant... I hope.
I was referring to Anthony's post of highest highs possible.
I understand how atmospheres can help to lower highs and increase lows by averaging temperatures across the planet.
I'm sorry for causing confusion through my over vagueness.

[Flyndaran]

Originally Posted by David Johnston2

The stuff that happens a mile underground is however, not very significant to us. We live on the surface and the air affects us.

I live in northern Oregon. I would say that what STARTED a mile underground had quite the effect here in Portland back in 1980. ;)
The daytime sky turning dark as ash fell like a mini-snowstorm.

[Anthony]

Some back of the hand calculations give a pretty substantial heat capacity to the atmosphere, I suspect a lot of nighttime cooling only applies fairly near the surface (on the other hand, the upper atmosphere is pretty cool all the time).