How do calculate the coefficients a and b in the equation Angstroms-Prescott? (please see the attached file)
Dear Rian,
Using a least-squares minimization. Angstrom-Prescott equation is widely used for estimating the global radiation. The formula is:
H/H0 = a+b(n/N)
where, H is the global radiation (MJ m-2 day-1)
H0 is the extraterrestrial solar radiation on a horizontal surface (MJ m-2 day-1); n is the number of hours measured by the sunshine recorder
N the maximum daily sunshine duration;
a and b are empirically determined regression constants.
Therefore, given the variables (H/Ho) and (n/N), you should be able to obtain the parameters "a" and "b", through a linear regression.
See attached publication
Article Estimation of monthly Angström–Prescott equation coefficient...
Dear Rian,
Using a least-squares minimization. Angstrom-Prescott equation is widely used for estimating the global radiation. The formula is:
H/H0 = a+b(n/N)
where, H is the global radiation (MJ m-2 day-1)
H0 is the extraterrestrial solar radiation on a horizontal surface (MJ m-2 day-1); n is the number of hours measured by the sunshine recorder
N the maximum daily sunshine duration;
a and b are empirically determined regression constants.
Therefore, given the variables (H/Ho) and (n/N), you should be able to obtain the parameters "a" and "b", through a linear regression.
See attached publication
Article Estimation of monthly Angström–Prescott equation coefficient...
Assistant can explain the details of the work
I want information /latitude of sit and
solar radiation measurement Mj/m2
sunshine duration unit : h
E-mail [email protected]
Dear Rian
As Eiras said, you can use "solver" in Excel or you can use a minimization method in Matlab software. this work is so easy to do :D
Good Luck
I'm preparing the Matlab software program.
Data provided by the incomplete
solar radiation measurement unit .kwh MJ W ......؟؟؟؟/m2
latitude of ..............؟؟؟؟
Dear Rian
H/H0 = a+b(n/Nd) is the first, simple and foremost empirical model called A-P model to estimate monthly mean daily global solar radiation at the location concerned. The regression coefficients a and b depend on geographical and meteorological condition of the given place. Different researchers proposed different values of regression coefficients for different places. Some are claimed universal nature of the coefficients and derived the values.
Since their geographical and meteorological dependable nature the best and simple way to determine a and b is the statistical technique i.e., linear regression equation/ least square line. For this one should have the data of monthly mean daily i) extraterrestrial radiation (H0), ii) measured radiation (H), iii) actual sunshine hours (n) and iv) maximum possible sunshine duration (Nd) of the site(s).
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