I Infrared energy flux from the Moon

[Incnis Mrsi]

TL;DR Summary

The quantitative value of the Moon’s energy flux density on Earth is in tens mW/m², but how many namely?

I am interested in energy flux density from the Moon at Earth’s surface, specifically in infrared (albeit most of it comes in infrared anyway).
Physics.SX (boyfarrell) gives an estimate 89 mW/m². I doubt it for several reasons.

• 400 K (as effective mean) on Moon seems to be unrealistically hot. This Soviet research gives 380 K. Not a small mismatch after taking to 4th power.
• The Sun’s photosphere is 15 times hotter than 380 K. From the solar flux value 1360 W/m² (and keeping in mind that both discs are of the same angular size) we obtain, via division by 15⁴, as little as 27 mW/m², and even accounting for the fact that Sun is less a black body than Moon, we are a way below boyfarrell’s estimate. Moreover, iRL there is more atmospheric extinction in infrared than in visible.
• I generally distrust aforementioned Q&A site, including their ability to do correct math.

I understand that the flux density depend greatly on the phase and other conditions, but the upper estimate (for the full moon overhead and clear weather) is the most important for me.
By the way, why information on measured energy flux from various sources is difficult to find with a Google search?

 

[Drakkith]

Are you looking for the peak value, the mean, or something else? Obviously it changes with the phases of the Moon since the part of the surface in shadow is going to be cooler than the part in sunlight.

 

[Tom.G]

Are you assuming the Moon is a disk or a sphere? Or does it even matter?

https://www.physicsforums.com/threa...of-sunlight-to-moonlight-at-full-moon.166111/

Cheers,
Tom

 

[Incnis Mrsi]

Firstly, I do not “assume” and am interested in factual flux density, some upper estimate (at least, for land not very far from the equator and not very above the m.s.l.). An answer consisting of a link to measurement results (and possibly not a single formula) will qualify. Replies consisting of speculations and pettifogging about hypothetical effects will not (as answers).

Secondly, it is obvious that the full moon’s limb is cooler than the central regions of the Near Side. But I don’t expect the thermal radiance to depend strongly on the angle of view, although do not preclude such dependence and certainly can do necessary corrections (in case the dependence can be backed by peer-reviewed publications).

Thirdly, here is not a homework question; it is rather a research topic. Anyway, I prefer not to waste my effort browsing through help-with-my-homework postings full of «^» and «*».

 

[Drakkith]

I understand that the flux density depend greatly on the phase and other conditions, but the upper estimate (for the full moon overhead and clear weather) is the most important for me.

My apologies, it appears I missed this part of your post when I replied, making my entire earlier post unnecessary.

Anyways, I couldn't find much during a quick google search, but I'll try to do a deeper dive when I have the chance.

 

[russ_watters]

https://sos.noaa.gov/datasets/moon-surface-temperature/

 

[Incnis Mrsi]

https://sos.noaa.gov/datasets/moon-surface-temperature/

Is the lunar day–night period “28 Earth days”, is it really that short? I expected it to be exactly equal to the Earth–Moon–Sun synodic period (29½ days) because Moon is tidally locked to Earth. But Incnis Mrsi might miss some very advanced findings of astronomy…

 

[Drakkith]

Is the lunar day–night period “28 Earth days”, is it really that short? I expected it to be exactly equal to the Earth–Moon–Sun synodic period (29½ days) because Moon is tidally locked to Earth. But Incnis Mrsi might miss some very advanced findings of astronomy…

It should be equal to the synodic period. Either someone fat-fingered a number when making that page or they didn't think they needed to be exact.