Author Topic: How is albedo change calculated?  (Read 4408 times)

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Offline steili (OP)

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How is albedo change calculated?
« on: May 13, 2020, 12:19:26 PM »
I've tried searching for this, but it doesn't seem to be documented anywhere except for a paragraph on how it works in VB6:

Quote
The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

Is this still the case in C#? I've constructed a spreadsheet to calculate optimal terraforming, but as of now I need to recalculate when ice sheets melts. This would be unnecessary if I knew beforehand how the albedo would change :-)
 

Offline SpikeTheHobbitMage

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Re: How is albedo change calculated?
« Reply #1 on: May 13, 2020, 12:22:02 PM »
I've tried searching for this, but it doesn't seem to be documented anywhere except for a paragraph on how it works in VB6:

Quote
The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

Is this still the case in C#? I've constructed a spreadsheet to calculate optimal terraforming, but as of now I need to recalculate when ice sheets melts. This would be unnecessary if I knew beforehand how the albedo would change :-)
What you may need to do is keep track of the ice sheets and what change occurs to see if there is a pattern.
 

Offline skoormit

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Re: How is albedo change calculated?
« Reply #2 on: May 13, 2020, 12:35:22 PM »
I've tried searching for this, but it doesn't seem to be documented anywhere except for a paragraph on how it works in VB6:

Quote
The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

Is this still the case in C#? I've constructed a spreadsheet to calculate optimal terraforming, but as of now I need to recalculate when ice sheets melts. This would be unnecessary if I knew beforehand how the albedo would change :-)

I like you already.

I have the same spreadsheet. In my experience, the albedo doesn't change by much.

So, I don't worry about it when I'm planning.
When the sheet melts, I update the albedo value and make sure that my end-state temperature hasn't gone outside my hab range. Only because I'm paranoid. It's never even come close.
In cases where I'm adding a lot of GH to reach hab range, the albedo increase will allow me to get to the hab range sooner, but I've never seen it reduce the needed terraforming by much.
It does mean that, in cases where your final ATM will be greater than 1.0 (and therefore your final Oxygen will be more than the minimum 0.1), you want to make the sheet melt before you add oxygen, so that you don't add more oxygen than you actually needed for the final amount of GH.
 

Offline steili (OP)

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Re: How is albedo change calculated?
« Reply #3 on: May 13, 2020, 03:18:36 PM »
I'm aware that it's not typically very significant, but I want my calculations to be.. perfect  ;D

Regarding oxygen, I always only add 0.1. Is there any point to ever adding more than this? Here's my sheet if you want to have a look:

https://docs.google.com/spreadsheets/d/1YMiPY51KzF-l43Zvg0RB3Tnj6tHVHWTk3KkiOCbW63E/edit?usp=sharing
 

Offline steili (OP)

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Re: How is albedo change calculated?
« Reply #4 on: May 13, 2020, 03:22:50 PM »
It does mean that, in cases where your final ATM will be greater than 1.0 (and therefore your final Oxygen will be more than the minimum 0.1), you want to make the sheet melt before you add oxygen, so that you don't add more oxygen than you actually needed for the final amount of GH.

I don't quite get this: You can still have (much) more than 1atm and still only 0.1atm O2. Afaik there's no lower bound to relative oxygen partial pressure. In my sheet there's data from Io. Here I have 0.1atm O2 but 1.25 atm total pressure.
 

Offline davidb86

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Re: How is albedo change calculated?
« Reply #5 on: May 13, 2020, 03:52:20 PM »
Quote
I don't quite get this: You can still have (much) more than 1atm and still only 0.1atm O2. Afaik there's no lower bound to relative oxygen partial pressure. In my sheet there's data from Io. Here I have 0.1atm O2 but 1.25 atm total pressure.

you need at least 0.1 atm of oxygen and you need it to be between 10% and 30% of the atmosphere, if it drops below 10% it should kick back to un-breathable.  If he actually got this from an active game we need to note the version number and submit as a bug.
 

Offline Demonius

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Re: How is albedo change calculated?
« Reply #6 on: May 13, 2020, 03:55:42 PM »
I think the correct restriction is 0.1 - 0.3 atm, and below 30% overall.
 

Offline steili (OP)

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Re: How is albedo change calculated?
« Reply #7 on: May 13, 2020, 04:11:28 PM »
I think the correct restriction is 0.1 - 0.3 atm, and below 30% overall.

I'm pretty sure this is correct - there's no lower band on relative partial oxygen pressure.
 

Offline davidb86

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Re: How is albedo change calculated?
« Reply #8 on: May 13, 2020, 04:34:00 PM »
I stand corrected
 

Offline skoormit

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Re: How is albedo change calculated?
« Reply #9 on: May 13, 2020, 10:05:27 PM »
It does mean that, in cases where your final ATM will be greater than 1.0 (and therefore your final Oxygen will be more than the minimum 0.1), you want to make the sheet melt before you add oxygen, so that you don't add more oxygen than you actually needed for the final amount of GH.

I don't quite get this: You can still have (much) more than 1atm and still only 0.1atm O2. Afaik there's no lower bound to relative oxygen partial pressure. In my sheet there's data from Io. Here I have 0.1atm O2 but 1.25 atm total pressure.

Now I am scratching my head.
Was it so in VB? Surely I did not just invent the 10% rule to make things harder for myself?
 

Offline Steve Walmsley

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Re: How is albedo change calculated?
« Reply #10 on: May 14, 2020, 04:52:23 AM »
I've tried searching for this, but it doesn't seem to be documented anywhere except for a paragraph on how it works in VB6:

Quote
The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

Is this still the case in C#? I've constructed a spreadsheet to calculate optimal terraforming, but as of now I need to recalculate when ice sheets melts. This would be unnecessary if I knew beforehand how the albedo would change :-)

When the ice melts, Albedo increases by 0.0015 * Hydro Extent.
 
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Offline GL

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Re: How is albedo change calculated?
« Reply #11 on: May 14, 2020, 10:49:10 AM »
I've tried searching for this, but it doesn't seem to be documented anywhere except for a paragraph on how it works in VB6:

Quote
The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

Is this still the case in C#? I've constructed a spreadsheet to calculate optimal terraforming, but as of now I need to recalculate when ice sheets melts. This would be unnecessary if I knew beforehand how the albedo would change :-)

When the ice melts, Albedo increases by 0.0015 * Hydro Extent.

Does this mean that if I add water vapor while the water is frozen I'll get a bigger Albedo increases when it melts?
 

Offline Steve Walmsley

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Re: How is albedo change calculated?
« Reply #12 on: May 14, 2020, 10:57:18 AM »
I've tried searching for this, but it doesn't seem to be documented anywhere except for a paragraph on how it works in VB6:

Quote
The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

Is this still the case in C#? I've constructed a spreadsheet to calculate optimal terraforming, but as of now I need to recalculate when ice sheets melts. This would be unnecessary if I knew beforehand how the albedo would change :-)

When the ice melts, Albedo increases by 0.0015 * Hydro Extent.

Does this mean that if I add water vapor while the water is frozen I'll get a bigger Albedo increases when it melts?

Yes, although I probably should change it so that adding ice reduces Albedo.
 

Offline SpikeTheHobbitMage

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Re: How is albedo change calculated?
« Reply #13 on: May 14, 2020, 11:25:03 AM »
I've tried searching for this, but it doesn't seem to be documented anywhere except for a paragraph on how it works in VB6:

Quote
The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

Is this still the case in C#? I've constructed a spreadsheet to calculate optimal terraforming, but as of now I need to recalculate when ice sheets melts. This would be unnecessary if I knew beforehand how the albedo would change :-)

When the ice melts, Albedo increases by 0.0015 * Hydro Extent.

Does this mean that if I add water vapor while the water is frozen I'll get a bigger Albedo increases when it melts?

Yes, although I probably should change it so that adding ice reduces Albedo.
The way to do that without getting exploity or having to deal with cumulative rounding errors is to factor ice extent into the temperature calculation instead of twiddling the albedo number.
 

Offline Pedroig

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Re: How is albedo change calculated?
« Reply #14 on: May 14, 2020, 12:23:02 PM »
I've tried searching for this, but it doesn't seem to be documented anywhere except for a paragraph on how it works in VB6:

Quote
The amount of albedo change is based on the extent of the ice sheet (F9 again) plus a random factor.

Is this still the case in C#? I've constructed a spreadsheet to calculate optimal terraforming, but as of now I need to recalculate when ice sheets melts. This would be unnecessary if I knew beforehand how the albedo would change :-)

When the ice melts, Albedo increases by 0.0015 * Hydro Extent.

Does this mean that if I add water vapor while the water is frozen I'll get a bigger Albedo increases when it melts?

Yes, although I probably should change it so that adding ice reduces Albedo.

Why would ice reduce Albedo?
Quote
Albedo is a non-dimensional, unitless quantity that indicates how well a surface reflects solar energy. Albedo (α) varies between 0 and 1. Albedo commonly refers to the "whiteness" of a surface, with 0 meaning black and 1 meaning white. A value of 0 means the surface is a "perfect absorber" that absorbs all incoming energy. Absorbed solar energy can be used to heat the surface or, when sea ice is present, melt the surface. A value of 1 means the surface is a "perfect reflector" that reflects all incoming energy.
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