Incoming radiation variables

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michael3911
Posts: 5
Joined: Sun Nov 17, 2019 9:50 am

Incoming radiation variables

Post by michael3911 » Tue Apr 27, 2021 9:56 am

Hello,

I am wondering if there is any difference between SWDNB and SWDOWN variables for shortwave incoming radiation and between GLW and LWDNB for longwave radiation? I have found a 0.001 W.m-2 difference in domain maximum for SW variables (using ncview) but otherwise both SW and LW variables seem to be identical or very similar. I would like to compare modelled fluxes with observations.

Thank you.
Michael

Ming Chen
Posts: 1456
Joined: Mon Apr 23, 2018 9:42 pm

Re: Incoming radiation variables

Post by Ming Chen » Thu Apr 29, 2021 10:04 pm

Michael,
SWDNB and SWDOWN have the same physical meaning and they should be identical. The same for GLW and LWDNB. However, note that SWDNB is directly output from radiation scheme, while SWDOWN is derived from GSW and albedo (SWDOWN(I,J)=GSW(I,J)/(1.-ALBEDO(I,J)))
I guess this might cause slight difference between the two variables.
I would suggest you use SWDNB to compare with in-situ observations. This is because, unless there is accurate measurement, we are not sure how precise albedo is. Bias in albedo may introduce bias to SWDOWN.
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michael3911
Posts: 5
Joined: Sun Nov 17, 2019 9:50 am

Re: Incoming radiation variables

Post by michael3911 » Fri Apr 30, 2021 9:34 am

Hello,
Thank you for explanantion. It is clear for me now :) .
Have a nice day,
Michael

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