Category (4): Extraterrestrial radiation and solar declination-based models:
Can Ertekin model (Model 18) which based on extraterrestrial radiation and solar declination, respectively displayed the best performance compared with other models with the largest coefficient of determination values [R.
mean] is the daily mean air temperature ([degrees]c), Ra is the Extraterrestrial Radiation for Daily Periods (mm/day), [E.
a] is the Extraterrestrial Radiation for Daily Periods (mm/day), T is the daily mean air temperature ([degrees]c).
Hourly global radiation was collected from a CASTNET weather station within the ASP on the Huntington Wildlife Forest (HWF187) and extraterrestrial radiation
The transmission of the H d from extraterrestrial radiation is only about 15% which rises to 18% in the month of August.
Fig (2) shows the behavior of cloudiness index K T ratio of diffuse to total radiation and diffuse to extraterrestrial radiation.
It is defined as the surface radiation divided by the extraterrestrial radiation
Daily extraterrestrial radiation
on a horizontal surface H0 can be calculated as a function of the solar constant ([I.
The direct radiation is empirical established depending on the extraterrestrial radiation
, the medium solar constant, the day number during a year, the distortion factor, the solar altitude angle, the solar declination, the latitude angle, the solar hour angle, and the local solar time.
13) Calculate the extraterrestrial radiation
from Equation 4.
The Hargreaves equation (HG) requires only daily mean, maximum and minimum air temperature extraterrestrial radiation
(Droogers and Allen 2002).