Dan P wrote:

> Christoph Hormann wrote:
> 
>> Dan P wrote:

<snip />

> This understanding may be incorrect; I'm wrong a lot!
> My ego is not invested in being right here -- for the good of the group, 
> please set us straight, Christoph! (The last sentence is actually not 
> being sarcastic).

Another thing; when I speak of an albedo value, I only speak of the 
value itself, not the application of the value. As you have mentioned, 
the albedo value depends on the angle the viewer observes it. If you 
bring in time, a body like Venus rotates over time and, thus, the albedo 
value changes because the surface the light is exposed to changes. So, 
an albedo value like the ones the web site provided are averages at best 
and are only useful for quantifying, somehow, the relative albedos of a 
set of objects; for example, how much more bright the object appears 
from earth compared to some other body in the set. It may also be useful 
for detecting changes on a surface. There are all kinds of APPLICATIONS 
for an albedo value, but this does not change the NATURE of an albedo value.

If an albedo value is not from 0 to 1, then it is bound within some 
arbitrary range described by the object with the highest albedo value we 
have observed at some moment in time. The definition, "the fraction of 
light that is reflected by a body or surface." can support this: a 
fraction can be 2+1/2, for example, or 250%. So, if we were to observe 
an albedo value of Venus at some moment in time, then we could say at 
some future moment in time that the albedo value is 250% higher than before.

I thought this was interesting:

"At BRW and MLO, albedo values above 1.0 are due to instrument noise at
low aerosol concentration. These high albedo values are not present in 
daily averaged data. Furthermore, these high albedo values are not 
present if data are excluded where ?sp is below 1 Mm-1. Hence, the high
albedo values result from an instrument detection limitation problem."
http://www.cmdl.noaa.gov/publications/annrpt26/3_1_3.pdf

So, an albedo value can be above 1, but is it valid?

I'm finding it hard to find albedo values above 1. Take the following 
example of snow albedos:

http://www.agu.org/pubs/sample_articles/cr/2001JD001160/figures.shtml#fig15

They assume from 0 to 1 on their graphs. Same for this site:

http://cires.colorado.edu/~maurerj/albedo/albedo.htm


So, the crux: the definition itself does not specify that an albedo must 
be from 0 to 1, but I believe that to be axiomatic (self-evident). I 
will attempt to create a proof:

Truth: A surface may not reflect less light than is applied to it.
Truth: A surface may not reflect more light than is applied to it.
Truth: A body cannot reflect less light than is applied to it.
Truth: A body cannot reflect more light than is applied to it.

Therefore

A minimum albedo means a surface reflects no light.
A minimum albedo means a body reflects no light.

A maximum albedo means a surface reflects all light.
A maximum albedo means a body reflects all light.

0% of light means no light.
100% of light means all light.

0% may be represented as 0.
100% may be represetnted as 1.

Therefore

A minimum albedo is 0
A maximum albedo is 1


If you have some further truths to add to this proof to disprove my 
claim, please add them; it will help mine and other's understanding of 
this interesting subject!

Some more web-sites of interest:
http://www.experimentarium.dk/uk/naturvidenskab_og_teknik/artikler/artikel.118.html
http://en.wikipedia.org/wiki/Albedo


(See, Mom, I can sound smart too!)
-- 
Respectfully,
Dan P
http://<broken link>

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