[Radiance-general] [help] how to get short-wave and long-wave solar radiation value?

[Jia Hu]

It is good to know this!  Thanks.

On Mon, Jul 18, 2011 at 2:49 AM, Lars O. Grobe <grobe at gmx.net> wrote:

> Hi Ji Zhang!
>
>
>  May I ask whether it's possible to "isolate" the contribution of
>> short-wave and long-wave solar radiation using Radiance?
>>
>> One of our colleagues wants to get these values for the calculation of
>> "mean radiant temperature" for the purpose of analyzing the implications
>> of urban geometries on thermal comfort.
>>
>> Correct me if I'm wrong, the irradiation value obtained in Radiance is
>> the total solar radiation energy received on a given surface.
>>
>> So, is this "total" value encompasses the full spectrum of solar
>> radiation, including the visible part and the short-wave and long-wave
>> parts that are not visible to human eyes?
>>
>> If it is, then, is there a way to single out the contribution from
>> short-wave and long-wave radiation separately?
>>
>> Clarification and advices are deeply appreciated!
>>
>
> You are (almost) completely free to choose what wavelength range to squeeze
> into any of the three channels that we usually refer to as RGB. So instead
> of calling the first channel "RED", you could call it "Shortwave". As long
> as you use the three channels for the same wavelength ranges when defining
> materials, sources, and interpreting results, that is fine for radiative
> transfer of energy.
>
> However I would advice not to make use of the possibility of rendering all
> these wavelength ranges at once by making use of the three channels. It
> would be better to set all three channels to the same wavelength range, so
> work with "neutral grey" lights and surfaces. The reason is that there are
> some (few) parts of Radiance's code where the channels are weighted
> according to human perceiption assuming RGB-like wavelengths.
>
> Another question is how to find how much of the absorped short-wave solar
> irradiation may get emitted as long-wave radiation by a surface. Radiance
> does not consider such "shift" effects. So IR radiation by surfaces heating
> up in the sun would not be reflected.
>
> Cheers, Lars.
>
>
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