--- Chuck Hards <chuckhards@yahoo.com> wrote:
I'm moving on.
See ya.
Considering the relative albedos of a mostly cloudless vs. cloud-covered hemisphere, I'd be willing to bet that at extremes it still has a greater effect on earthshine than distance.
It was a sufficiently cool question that I checked out the journal literature. Here are my notes and links for group archival purposes: Apparently, the relationship between Earthshine and the Earth's albedo wasn't looked at closely until recently as part of the study of global climate change. In 2003, a researcher at the CIT and Big Bear Solar Observatory developed an automated CCD camera system to measure the albedo of the Earth using Earthshine reflected off the Moon as a detector. Effectively Goode was using the Moon as a photographic big "grey" card. He mathematically compensated for changes in Earthshine from the phase and position of Moon and lunar topography - leaving only the Earth's albedo. Variations in Earthshine are well-correlated with the Earth's albedo. It looks like within a single year, variations in the Earth's albedo are around -+8%.
From 1985 to 2003, there was an annual average variation of +8% to -2%.
Goode used "daily cloud-cover data from Intellicast" to come up with an estimate of the daily global cloud cover. Goode, P. et al. 2003. Sunshine, Earthshine and Climate Change II. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003JKAS...36S..83G Per Figure 2 - +-8% (within a single year) Earthshine project public ed. science info summary http://www.bbso.njit.edu/science_may28.html http://www.bbso.njit.edu/espr/sci_images/fig_watts_website.gif (annual variations - 1985-2003 - +10% to -2%) http://www.bbso.njit.edu/espr/sci_images/trycover3.jpg Big Bear Solar Observatory - Earthshine project http://www.bbso.njit.edu/Research/EarthShine/ http://www.bbso.njit.edu/ Palle, E. et al. 2003. Earthshine and the Earth's albedo 2. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003JGRD.108vACL13P Thejll, P., Goode, P. 2002. Earthshine: A Proposal to Build an Automatic System for Observing Terrestrial Albedo. (abstract). http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002EGSGA..27.4058T Qui, J. Goode, P. 2003. Earthshine and the Earth's albedo: 1. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003JGRD.108vACL12Q Koonin, S.E. 1998. Earthshine and the Earth's Albedo. http://www.bbso.njit.edu/Research/EarthShine/espaper/earthshine_paper.html __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com