Kippzonen BSRN Scientific Solar Monitoring System Manual do Utilizador descarregar pdf (Página 179)

167

Subroutine Solar: Equations based upon the paper of Michalsky (1988) and the approximate equations

given in the Astronomical Almanac.

Note: Subroutine call is to be a single line

SUB AstroAlm (year, jd, GMT, Lat, Lon, StnHeight, Az, El, EOT, SolarTime$, Decdegrees, Airmass$,

HaDegrees)

' ===========================================================================

' The following subroutine calculates the approxim ate solar position and is

' based on the following paper:

' Joseph J. Michalsky: The astronomical almanac's algorithm for approximate

' solar position (1950-2050). Solar Energy 40 (3), 227-235 (1988).

' Note also that an Errata notice appeared in Solar Energy Vol. 41, No. 1,

' p. 113, 1988 concerning a correction to the above algorithm . This

' correction has been incorporated into the subroutine that follows.

' In the original subroutine, a division by latitude in the determination of

' of 'elc' (critical elevation) caused a divide by zero error for equatorial

' calculations. This code has been replacedby equivalent code for deter-

' mining solar azimuth.

' This subroutine calculates the local azimuth and elevation of the sun at

' a specific location and time using an approximation to equations used to

' generate tables in The Astronomical Almanac. Refraction correction is added

' so sun position is the apparent one.

' The Astronomical Almanac, U.S. Government Printing Office, Washington, DC

' Input parameters:

' Year = year (e.g., 1986)

' JD = day of year (e.g., Feb. 1 = 32)

' GMT = Greenwich Mean Time (decimal hours)

' Lat = latitude in degrees (north is positive)

' Lon = longitude in degrees (west is positive)

' StnHeight = height of station in metres above sea level

' Output parameters:

' Az = sun azimuth angle

' (measured east from north, 0 to 360 degrees)

' El = sun elevation angle (degrees) plus others, but note the

' units indicated before return to calling routine

' EOT = equation of time (seconds)

' TST = True Solar Time (hours)

' SolarTime$ = solar time (HH:MM:SS)

' Decdegrees = declination in degrees

' Airmass$ = airmass as an alphanumeric string

' Notes: 1) The algorithm included in the above-mentioned paper was written

' in Fortran and has been translated into QuickBasic V4.5.

' 2) Since QuickBasic V4.5 does not contain the arcsin function, the

' following substitute relationship is used:

' arcsin(x) = ATN(X / SQR(1 - X ^ 2))

' where ATN is the arctangent.

' 3) The MOD (modulus) function provided by QuickBasic V4.5 is not

' used since it does not yield the same result as the modulus

' function in Fortran. For example:

' in QuickBasic V4.5 19 MOD 6.7 = 5.0 (decimal portion truncated)

' in Fortran 19 MOD 6.7 = 5.6

' As a result, the Fortran modulus function has been rewritten

' using the equivalent:

1 2 ... 174 175 176 177 178 179 180 181 182 183 184 ... 187 188

Comentários a estes Manuais

Sem comentários

Kippzonen BSRN Scientific Solar Monitoring System Manual do Utilizador Página 179

Comentários a estes Manuais