MRT/Surface temp with reflected solar load

[rxs5160]

Posting a following up question to this post: Surface Temperature under reflected solar heat gain

A clarifying question for my understanding…using the componentSolarMRT, we plug in the DIRECT solar rad from the weather file and unobstructed direct solar irradiance. For the DIFFUSE solar rad, we take the difference b/w the reflected irradiance on the calc surface and the direct solar irradiance with no obstructions. the different makes sense because we are finding the delta MRT due to the solar reflection. just need some clarity as to why the reflected rays find its way into the diffuse component - do we account for the sky’s original diffuse radiation in the radiance PIT calc then add the reflected rays as additional diffuse?

Given the above, what does the deltaMRT represent?

Attached is the script I am referencing. thanks to @chris

PIT_SolarAdjusteMRTExample.gh (551.5 KB)

[rxs5160]

I found explanation of delta MRT here: MRT for UTCI calculation - #2 by chris

From the componentSolarMRT, if you take the MRT minus the longwave MRT you get the deltaMRT, which makes sense.

I would still like clarity why diffuse radiation = radiance PIT values minus direct irradiance. I assume the diffuse irradiance is accounted for in the PIT calc.

I tried running the script above and compared that to the component solar MRT without the PIT radiance calc for when there is no reflected solar energy (made a “shade” way off in the distance). I expect the values to be similar but maybe I am missing something?

[rxs5160]

Following up on this post, if anyone has insight. Let me know if something isn’t clear