markdown ## Diurnal Variation 從 Charles-Edward et al., (1986) 建議可以使用half-wave sine response (De Vries, 1955)，或Full-wave sine function (Charles-Edwards and Acock, 1977)，2Dsoil 是使用half wave sine function (P42, Equation 5.11)，GLYCIM 模式使用的公式應該也是 Half wave sine function。
**Half wave sine function**
$I(t)=\dfrac{\pi S}{2h} * sin(\dfrac{\pi t}{h})$
**Full wave sine function**
$I(t)=\dfrac{S}{h}\(1+sin(\dfrac{2\pi t}{h}+\dfrac{3\pi}{2}))$
其中，S是整天的日射量累積值，h為日照時數，t為日照開始的小時數。
2D soil 也是使用half wave sine function 進行解析 [P42, Equation 5.11]
## Solar radiation to PPFD
參考 Campbell and Norman (1998) An introduction to environmental biophysics. P 148.
1 J/m2 s = 1 Watt/m2 照射1秒鐘
1 PAR = 1/235000 = mol /m2 s
For solar radiation at sea level with sun zenith angle of 60 degrees, the median wavelength in the 400 to 700 nm waveband is about 550 nm, for which the photon energy is 2.17 * 10E5 J/ml. This conversion factor, which is often expressed as 4.6 umol quanta per J.
## 測試檔案
有興趣者可以參考一下
https://docs.google.com/spreadsheets/d/1SHxBYhAJ3v0O8KdBX7NlGBi-OUYrob3r/edit?usp=sharing&ouid=116278873958206756284&rtpof=true&sd=true
##參考文獻
Charles-Edwards, David., D. Deley, and G.M Rimminton. (1986) Modeling plant growth and development. Academic Press Australia.
Smithsonian Meteorological Tables. 1963. 6th edition. R.J. List (ed.). Smithsonian Institution, Washington, DC.
