DrylandEcology/SOILWAT2: v6.0.0

• Improved estimation of radiation on tilted surfaces
  • code now accounts for seasonally varying sun-earth distance
  • new approach implements a clear-sky model (additionally attenuated by a cloud factor) and a separation model to treat direct beam and diffuse radiation separately (previously, code estimated only direct beam insolation and used a crude all-sky model)
  • code estimates now all possible sunrise and sunset hour angles for a horizontal and a tilted surface (with 0, 1, or 2 periods of possible sunlight) as well as the daily integral of the cosine of the solar incidence angle and the daily integral of the sine of the solar altitude angle (previous estimates were increasingly wrong the further away from equator the slope was facing)
  • new approach implements an anisotropic transposition model to transpose direct beam and diffuse components of global radiation from a horizontal to a tilted surface and to estimate a reflected radiation component

• User visible changes to inputs
  • climate.in: "Atmospheric transmissivity" is removed (was not used by code since a very long time/ever?)
  • siteparam.in:
    • Longitude is a new input (for complete documentation of location, but currently not used by code)
    • Latitude is now in degrees (instead of radians -- so that all input angles are in the same units)
    • Aspect changed orientation: now, S = 0 (degrees), E=-90, N=±180, W=90 (previously, N=0, E=90, S=180, W=270)
  • weathsetup.in
    • flag to toggle source of daily meteorological forcing between weather generator to fill in missing inputs (1) and using only inputs from files (0) gained a new option (2) that indicates to use only the weather generator and to not check for weather input files
    • input to declare first year of weather input files gained a new option (-1) to indicate that first year of weather inputs corresponds to first year of simulation period
    • removed "number of days to use in a moving average of temperature" (was not used by code since a long time)

• User visible changes to outputs
  • Output type "PET" gained four new variables:
    • PET_H_oh_MJm-2 = extraterrestrial horizontal solar irradiation [MJ / m2]
    • PET_H_ot_MJm-2 = extraterrestrial tilted solar irradiation [MJ / m2]
    • PET_H_gh_MJm-2 = global horizontal irradiation [MJ / m2]
    • PET_H_gt_MJm-2 = global tilted irradiation [MJ / m2]

• Additional testing

  • Additional testing output can be generated by passing appropriate flags when running unit tests. Scripts are available to create sun hour angles plots for horizontal and tilted surfaces:
    • Numbers of daylight hours and of sunrise(s)/sunset(s) for each latitude and day of year for some slope/aspect combinations
    • Sunrise(s)/sunset(s) hour angles for each latitude and some slope/aspect/day of year combinations

      CPPFLAGS=-DSW2_SolarPosition_Test__hourangles_by_lat_and_doy make test test_run
      Rscript tools/plot__SW2_SolarPosition_Test__hourangles_by_lat_and_doy.R

      CPPFLAGS=-DSW2_SolarPosition_Test__hourangles_by_lats make test test_run
      Rscript tools/plot__SW2_SolarPosition_Test__hourangles_by_lats.R