Improving the S-Shape Solar Radiation Estimation Method for Supporting Crop Models

Table 1

Investigated types of the S-shape radiation estimation method. *Two other forms (when parameter 𝑓 and 𝑔 were considered to be constant) of the 0-2-1-4 type were also investigated.

Notation	Term in (5)				Number of parameters	Note
	τ	𝐹cd	1+𝑞⋅𝑅	𝐹𝑠
5-44-4S	^2F-series	(3)	No	No	37	S-shape as proposed in [11].
5-44-4	^2F-series	(3)	No	^2F-series	17	Separate parameterization for wet and dry days.
3-44-4	^1F-series	(3)	No	^2F-series	15
1-44-4	constant	(3)	No	^2F-series	13
1-33-4	constant	(4)	No	^2F-series	11
1-33-2	constant	(4)	No	^1F-series	9
0-33-4	Estimated from Δ𝑇avg	(4)	No	^2F-series	10
0-3-1-4	Estimated from Δ𝑇avg	(4)	Yes	^2F-series	8
0-2-1-4*	Estimated from Δ𝑇avg	(4)	Yes	^2F-series	7	Parameter 𝑛 in (4) is set to 2.285 which is the average of the 𝑛 parameters of the 0-3-1-4 method obtained with site specific parameterization for the 109 stations.