World climate clarification, please

[JeffSandmeier]

In trying to determine the average nighttime temperature for a world with a standard atmosphere, I ran into a little snag. For a 'chilly' climate (d20 roll of 12 on the chart on page 376), the average daytime temperature is 0 degrees Celsius. The average nighttime temperature for a Standard atmosphere is -1/2 x the average daytime temperature. This means that the average nighttime temperature is also 0 degrees Celsius. So, for chilly climates, how do you determine the real nighttime temperatures?

 

[tjoneslo]

That's the problem with the formula. Mathematically, if you have a lower temperature the night time low ends up being higher than the day-time high.

My suggestion: Pick a number between five and 15, and make the low that many degrees lower than the high temp.

 

[sandman]

Or work with Kelvins...

 

[Tanuki]

Originally posted by Sandman:
Or work with Kelvins...

So if the average daytime temp is shirt-sleeve comfortable, the average nighttime temp is halfway to absolute zero? I don't THINK so.

The formula is bogus.

 

[sandman]

Originally posted by Tanuki:
So if the average daytime temp is shirt-sleeve comfortable, the average nighttime temp is halfway to absolute zero? I don't THINK so.

The formula is bogus.

That'd be good for world without atmosphere though... but then, those aren't problem anyway

I guess that MJD and Hunter didn't follow Planetology courses then

There's always the "pick a number" answer...

 

[Tanuki]

On worlds with a reasonable rotation rate a possible rule of thumb would be to apply a temperature drop of one to two degrees per hour of night.

For tidelocked worlds or worlds with a very slow rotation rate see the following two papers:

"Habitability of Planets Around Red Dwarf Stars" by Martin Heath, Laurance Doyle, Manoj Joshi and Robert Haberle, Origins of Life and Evolution of the Biosphere, vol 29, p 405 (1999) is at http://www.as.utexas.edu/astronomy/education/ spring02/scalo/heath.pdf

"Simulations of the Atmospheres of Synchronously Rotating Terrestrial Planets Orbiting M Dwarfs: Conditions for Atmospheric Collapse and the Implications for Habitability" by Manoj Joshi, Robert Haberle and R. Reynolds, Icarus, vol 129, p 450 (1997) is at http://www.seismo.unr.edu/ftp/pub/gillett/joshi.pdf

I'll go over them again and see if I can come up with a rule of thumb that will apply.

 

[tjoneslo]

I'm also posting this to the Errata board because this is not the first time this discussion has come up.

The latest version of the Errata has already changed the Max temperature to Average Temperature.

The climate to termerature table gives the average temperature.

The table that follows should be "Temperature Range"
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">Atmosphere Range
None 30 degrees
Trace 20 degrees
Very Thin 15 degrees
Thin 10 degrees
Standard 5 degrees
Dense 2 degrees</pre>[/QUOTE]Add the note:
Temperature can vary from the average by the range given, falling at night, rising during the day. Traveling north 30 degrees latitude subtracts the same value from the average temperature. Travelling south to the equator adds a like amount. Seasonal average temperatures can be up to twice this amount.

Make more sense?