short wave radiation and long wave radiation

[Lei]

Hello guys,

Did you use the solar radiation data provided by NCEP-NARR for
US? Why the long wave radiation is larger than short wave radiation in
this dataset? To my understanding, the shortwave radiation almost take
up all the solar radiation,because the Sun generate most energy in the
short wave region. what data do you usually use for the solar
radiation in SWAT simulation? Thanks.

[Xuesong Zhang]

SWAT input is short-wave solar radiation. However, you'd better not use radiation data from NARR. It is about 30% overestimation, or even worse for some regions.

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+ Xuesong Zhang                                 
+ Research Scientist
+ Joint Global Change Research Institute
+ Pacific Northwest National Laboratory
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+ http://xzhang.pbworks.com/
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[lei qiao]

Thank you very much, Xuesong. I was using short-wave radiation because I found they are comparable to the SWAT climate database. The longwave radiation is very large in the dataset, and make me confused. Anyway, your answer is very useful for me. BTW, do you know which dataset is more reliable?

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QIAO Lei (Charlie)
3642 Lindell BLVD
Earth and Atmospheric sciences
Saint Louis University
Saint Louis, MO 63108

[Xuesong Zhang]

We compared NARR, NLDAS, and EPIC (I think swat use similar method) estimated SR. We found that NLDAS (15-25% bias) is better than NARR, and EPIC (about 10-15% bias) is even better. Therefore, maybe using NLDAS or the default method in SWAT. Good luck!