Solar radiation incident at the earth's surface

Model : SolarRadiationDNDC
Simile version : 4.0
Date added : 2004-11-22
Keywords : Solar radiation ; Ecophysiology ;

Description

This model estimates the daily solar radiation incident at the earth's surface a given latitude and after passing through an atmosphere of given opacity (the cloudiness parameter in the model). Particularly it estimates:

• day length (hours)
• potential insolation on a horizontal plane (J m^-2day^-1)
• daily Photon Flux Density (PFD) sometimes refered to as, now deprecated, Photosynthetically Active Radiation (PAR)

The equations here were taken from the DNDC model (Li et al., 1992)

Files

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SolarRadiationDNDCP.sml

Diagram

Equations

Equations in climateP1
 
Variable   AC
	AC = TA=abs(z2),if TA<0.7 then 1.571-atan(TA/(1-TA^2)^0.5)else atan((1-TA^2)^0.5/TA) 
 
Variable   DayPAR : PAR (moles/m^2/day)
	DayPAR = solrad*2.05 
 
Variable   Day_Hrs : Length of day (hr)
	Day_Hrs = 2*(H*24)/(2*3.1416) 
 
Variable   H : Sun elevation angle at noon (radians)
	H = if z2>=1 then 0 elseif z2<= -1 then pi()else acos 
 
Variable   Jday : Day of Year
	Jday = time() 
 
Variable   PARc : Daily instantaneous PAR (umol m^-2 s^-1)
	PARc = DayPAR/(Day_Hrs*0.0036) 
 
Variable   Solar Constant : Solar constant (W m^2)
	Solar Constant = 1367.0 
	Comments:
		solar max Lean 1991 Rev. Geophysics 29 
 
Variable   Z
	Z = 0.398*sin(4.869+0.0172*Jday+0.0334*sin(6.224+0.0172*Jday)) 
 
Variable   acos
	acos = if z2<0 then 3.1416-AC else AC 
 
Variable   decl : Declination of the sun (radians)
	decl = if abs(Z)<0.7 then atan(Z/(1-Z^2)^0.5)else pi()/2-atan((1-Z^2)^0.5/Z) 
 
Variable   lat : Latitude (radians)
	lat = l=Latitude*pi()/1.8E+02,if abs(l*1.0)>=pi()/2 then sgn(l*1.0)*(pi()/2-0.01)else l 
	Comments:
		abs(lat) < 90 degrees 
 
Variable   psolrad : potential insolation on a horizontal plane, J/m^2/day
	psolrad = isc*(86400/(3.1416*r*r))*(H*sin(lat)*sin(decl)+cos(lat)*cos(decl)*sin(H)) 
	Where:
		isc=Solar Constant 
 
Variable   r : radius vector of the sun
	r = 1.0-0.0167*cos(0.0172*(Jday-3)) 
 
Variable   solrad : Insolation (MJ/m^2/day)
	solrad = psolrad*cloud/1.0E+06 
 
Variable   z2
	z2 = -(tan(decl)*tan(lat)) 

Results

References

Li et al., 1992. A model of nitrous oxide evolution from soil driven by rainfall events: 1. Model structure and sensitivity. Journal of Geophysical Research 97:9759-9776.

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