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Author Topic: Albedo-Warming Potential  (Read 42342 times)

Phoenix

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Re: Albedo-Warming Potential
« Reply #150 on: July 16, 2020, 06:37:54 AM »
Perhaps Nico can weigh and explain how to interpret some of the figures on his site. See the attached link...

https://cryospherecomputing.tk/awp-region.html

For the CAB chart on the bottom right, it looks like the annual solar input potential is ~ 2,600 MJ / m2 and the actual input  (if I understand the chart correctly) is ~ 500-600 MJ / m2. This would presumably be net of both albedo reflection and also cloud reflection ??

The charts are depicting actual albedo warming in the CAB as ~ 25% of the ice free potential implying 75% average reflection. I guess if I look at those charts a lot, I should try to know exactly what they mean. There is some distance to be reconciled here. Perhaps estimated cloudiness is the difference?
« Last Edit: July 16, 2020, 06:48:07 AM by oren »

sedziobs

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Re: Albedo-Warming Potential
« Reply #151 on: July 16, 2020, 07:10:16 AM »
This would presumably be net of both albedo reflection and also cloud reflection ??

The charts are depicting actual albedo warming in the CAB as ~ 25% of the ice free potential implying 75% average reflection. I guess if I look at those charts a lot, I should try to know exactly what they mean. There is some distance to be reconciled here. Perhaps estimated cloudiness is the difference?

Look at the y-axis title: clear sky absorption. Clouds are not factored in, which is why it's called Warming "Potential."

In the CAB, it looks like actual absorption is about 20% of ice free absorption until mid-May, which makes sense for 80% snow-covered ice albedo. Then the decadal values start to diverge as melt pond and open water fractions vary. I suspect that actual summer values are slightly underestimated as a result of albedo assumptions for bare ice and melt ponds.

oren

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Re: Albedo-Warming Potential
« Reply #152 on: July 16, 2020, 07:16:41 AM »
It's a result of an assumption about albedo which is true for part of the season but not for other parts of it. Remember the (excellent) tool is for comparison between years, mainly quantifying the latitude and location of open water and the amount of insolation it can receive.

Phoenix

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Re: Albedo-Warming Potential
« Reply #153 on: July 16, 2020, 03:39:55 PM »
It's a result of an assumption about albedo which is true for part of the season but not for other parts of it. Remember the (excellent) tool is for comparison between years, mainly quantifying the latitude and location of open water and the amount of insolation it can receive.

I see what you are saying. But if the tool is really only useful for accurately quantifying the open water AWP and not the areas which are covered by sea ice, it's not very useful for measuring what's going on in the CAB. 

I appreciate your taking the time. Math helps to drill down to the variables in question.

igs

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Re: Albedo-Warming Potential
« Reply #154 on: July 16, 2020, 06:25:37 PM »
It's a result of an assumption about albedo which is true for part of the season but not for other parts of it. Remember the (excellent) tool is for comparison between years, mainly quantifying the latitude and location of open water and the amount of insolation it can receive.

I see what you are saying. But if the tool is really only useful for accurately quantifying the open water AWP and not the areas which are covered by sea ice, it's not very useful for measuring what's going on in the CAB. 

I appreciate your taking the time. Math helps to drill down to the variables in question.


A potiential does not claim to be a good tool for measuring but to compare seasons which is what @Oren just said and there in fact wouldn't be much useful to add to that.
Knowledge that does not increase every day will decrease every day !

oren

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Re: Albedo-Warming Potential
« Reply #155 on: July 16, 2020, 07:49:56 PM »
I will add, most years albedo, and cloudiness, average out, and since open water has a much lower albedo than anything else, and is often found in more southern latitudes where insolation is accumulated over a longer season, the tool is quite useful even though it skips some of the details. In a weird year such as this, with both low albedo and low cloudiness especially in the center of the CAB, the comparison misses too much of what makes the year unique, but that does not mean the comparison is not useful or has not been useful in the past.

sedziobs

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Re: Albedo-Warming Potential
« Reply #156 on: July 16, 2020, 08:00:46 PM »
Similarly, Slater's model struggles with this season as well because it knows that compact ice in the CAB has historically not melted by September. That will be true until it isn't. All tools have their limits.

Phoenix

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Re: Albedo-Warming Potential
« Reply #157 on: July 16, 2020, 08:28:50 PM »
I will add, most years albedo, and cloudiness, average out, and since open water has a much lower albedo than anything else, and is often found in more southern latitudes where insolation is accumulated over a longer season, the tool is quite useful even though it skips some of the details. In a weird year such as this, with both low albedo and low cloudiness especially in the center of the CAB, the comparison misses too much of what makes the year unique, but that does not mean the comparison is not useful or has not been useful in the past.

Fair enough. Understanding is enhanced by trying to reconcile seemingly conflicting or ambiguous points. In this case about albedo.

You have made a persuasive case which helps to reconcile the ambiguity. Thank you.

"Tell me I forget, teach me I remember, involve me I learn" ~ Benjamin Franklin