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How to calculate Net radiation in WRF

W

wonseok ko

New member
Hello,

WRF version: WRF-4.3WPS version: WPS-4.3

I am trying to calculate net radiation with the equation Rn = SWD + GLW - SWU − LWU.
  1. I think that SWD is SWDOWN and GLW is GLW. Is that correct?
  2. I can't find SWU (Upward shortwave flux at the ground surface) and LWU (Upward longwave flux at the ground surface). How can I obtain these values?
  3. What is the difference between SWDOWN, SWDNT, and SWDNB?
  4. What is the difference between LWDNT and LWDNB?
  5. Is there any method to calculate net radiation with radiation flux? I have already calculated it with HFX, LFX, and GFX.
Any help is highly appreciated!
 
Please see my answers below:
wonseok ko said:
Hello,

WRF version: WRF-4.3WPS version: WPS-4.3

I am trying to calculate net radiation with the equation Rn = SWD + GLW - SWU − LWU.
  1. I think that SWD is SWDOWN and GLW is GLW. Is that correct?
Click to expand...
You are correct.
wonseok ko said:
  1. I can't find SWU (Upward shortwave flux at the ground surface) and LWU (Upward longwave flux at the ground surface). How can I obtain these values?
Click to expand...
WRF doesn't output SWU and LWU. However, GSW is "NET SHORT WAVE FLUX AT GROUND SURFACE", which is equivalent to SWD-SWU.

wonseok ko said:
  1. What is the difference between SWDOWN, SWDNT, and SWDNB?
Click to expand...

SWDOWN is "DOWNWARD SHORT WAVE FLUX AT GROUND SURFACE"
SWDNT is "INSTANTANEOUS DOWNWELLING SHORTWAVE FLUX AT TOP"
SWDNB is "INSTANTANEOUS DOWNWELLING SHORTWAVE FLUX AT BOTTOM"

wonseok ko said:
  1. What is the difference between LWDNT and LWDNB?
Click to expand...
LWDNT is "INSTANTANEOUS DOWNWELLING LONGWAVE FLUX AT TOP"
LWDNB is "INSTANTANEOUS DOWNWELLING LONGWAVE FLUX AT BOTTOM"
wonseok ko said:
  1. Is there any method to calculate net radiation with radiation flux? I have already calculated it with HFX, LFX, and GFX.
Click to expand...
net radiation is equal to GSW+netLW, netLW is net longwave radiation in the ground.
wonseok ko said:
Any help is highly appreciated!
Click to expand...
 
Ming Chen said:
Please see my answers below:

You are correct.

WRF doesn't output SWU and LWU. However, GSW is "NET SHORT WAVE FLUX AT GROUND SURFACE", which is equivalent to SWD-SWU.



SWDOWN is "DOWNWARD SHORT WAVE FLUX AT GROUND SURFACE"
SWDNT is "INSTANTANEOUS DOWNWELLING SHORTWAVE FLUX AT TOP"
SWDNB is "INSTANTANEOUS DOWNWELLING SHORTWAVE FLUX AT BOTTOM"


LWDNT is "INSTANTANEOUS DOWNWELLING LONGWAVE FLUX AT TOP"
LWDNB is "INSTANTANEOUS DOWNWELLING LONGWAVE FLUX AT BOTTOM"

net radiation is equal to GSW+netLW, netLW is net longwave radiation in the ground.
Click to expand...
Hello, Ming:
I'm new to WRF, and I'm currently using Noah-MP as the surface physics scheme. I noticed that the variable GSW is not available in the output. However, I found SWDOWN, FSA, and FIRA. What's the difference between SWDOWN and FSA? Does FSA represent netSW, and FIRA represent netLW? Does Rn = FSA + FIRA?
I’d greatly appreciate your detailed feedback.
 
Last edited:
SWDOWN is total downward solar radiation on the surface.
FSA, and FIRA are variables from NoahMP. They represent total absorbed solar radiation and total net longwave radiation.
Positive FSA means downward, and positive FIRA means upward (from land to the atmosphere), so net Rn = FSA - FIRA.
 
Ming Chen said:
SWDOWN is total downward solar radiation on the surface.
FSA, and FIRA are variables from NoahMP. They represent total absorbed solar radiation and total net longwave radiation.
Positive FSA means downward, and positive FIRA means upward (from land to the atmosphere), so net Rn = FSA - FIRA.
Click to expand...
Thanks for your answer! I have another question. Suppose my WRF output is every three hours — are the radiation variables (eg., FSA and FIRA) three-hour averages or instantaneous values at that time step? Is there any official documentation that provides detailed descriptions of the WRF output variables?
 
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