RADIATION (FAO-24)
fW
Table-W
Climate Access Database
Tmx, Tmn,RH, SS, SR
C
Table-C
LWa = 0.9
SWa = 0.25
LWb = 0.1
SWb = 0.5
albedo = 0.25
radiant = π Latitude/180
i
1 To 12
AvgT = (Tmx + Tmn)/2
EaTn = 0.61078 e(17.27*Tmn/(Tmn + 237.3))
EaTx = 0.61078 e(17.27*Tmx/(Tmx + 237.3))
ea = (EaTx + EaTn)/2
Edew = RH/(50/EaTx + 50/EaTn)
RHmax = Edew/EaTn*100
Dayno = 30.5 i - 14.6
2
1
Soldeclin = Sin (2Dayno/365 - 1.39) * 0.4093
xx = Sin(Soldeclin)*Sin(radiant)
yy = Cos(Soldeclin)*Cos(radiant)
temp1 = -Tan(Soldeclin*Tan(radiant))
Omega = tan-1(-temp1/√(-temp12 + 1)) + 2 tan-1(1)
Dr = (1 + 0.033*Cos((2/365)*Dayno))
RAa = 37.586*Dr*(Omega*xx + Sin(Omega)*yy)
N1 = 24/ Omega
NbyN = SR/N1
Rnl = albedo*(293.164)*(7.723 - √(10*Edew))*(0.1 + 0.9*NbyN)
Rns = (1 - Alpha)*RAa*(SWa + SWb*NbyN)
FNbyN = (LWb + LWa*NbyN)
> =0, <45
RHmax
RH = 45
3
2
> =45, <75
RHmax
RH = 60
> =75
RHmax
RH = 90
< 1.5
FNbyN
Unight = 1
>= 1.5, <2.5
FNbyN
Unight = 2
>= 2.5, <3.5
FNbyN
Unight = 3
>= 3.5, <4
FNbyN
Unight = 4
>= 0, <4.5
SR
SolR = 3
>= 4.5, <7.5
SR
4
SolR = 6
3
>= 7.5, < 10.5
SolR = 9
SR
>= 10.5
SR
SolR = 12
>= 0, <1.5
N1
Uday = 0
N1
>= 1.5, <4.5
Uday = 3
>= 4.5, <7.5
N1
Uday = 6
>= 7.5
N1
Uday = 9
xin = (RH/30 - 1)*4 + SolR/3
yin = (4 - Unight)*4 + (Uday/3 + 1)
Altitude = Int(Elev/500)*500
TempC = Int(AvgT/2)*2
5
4
Rn = Rns - Rnl
ETO = c(xin, yin) (fW(TempC/2, Altitude/500) Rn)
i