Table 3-6. Solar Radiation Source Flags
Flag Definition
A

  Post-1976 measured solar radiation data as received from
  NCDC or other sources
B

  Same as 'A' except the global horizontal data underwent a
  calibration correction
C


  Pre-1976 measured global horizontal data (direct and
  diffuse were not measured before 1976), adjusted from
  solar to local time, usually with a calibration correction
D

  Data derived from the other two elements of solar
  radiation using the relation, Kt = Kn + Kd (see Part 2,
  Section 8.1 for more information)
E


  Modeled solar radiation data using inputs of observed sky
  cover (cloud amount) and aerosol optical depths derived
  from direct normal data collected at the same location
F


  Modeled solar radiation using interpolated sky cover and
  aerosol optical depths derived from direct normal data
  collected at the same location
G


  Modeled solar radiation data using observed sky cover and
  aerosol optical depths estimated from geographical
  relationships
H

  Modeled solar radiation data using interpolated sky cover
  and estimated aerosol optical depths
?


  Source does not fit any of the above categories. Used for
  nighttime values, calculated extraterrestrial values, and
  missing data


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