code: def calc_horizontal_infrared_radiation_intensity(weatherdata):
      
      temp_drybulb_K = C2K(weatherdata._dry_bulb_temperature)
      temp_dew_K = C2K(weatherdata.dew_point_temperature)
      N = weatherdata.opaque_sky_cover
      sky_emissivity = (0.787 + 0.764 * math.log(temp_dew_K / C2K(0.0)) *
                        (1.0 + 0.0224 * N - 0.0035 * N ** 2 + 0.00028 * N ** 3))
      hor_id = sky_emissivity * sigma * temp_drybulb_K ** 4
      weatherdata.horizontal_infrared_radiation_intensity = hor_id
docs: Estimates the global horizontal infrared radiation intensity based
      on drybulb, dewpoint and opaque sky cover.
      References:
      Walton, G. N. 1983. Thermal Analysis Research Program Reference Manual. NBSSIR 83-
      2655. National Bureau of Standards, p. 21.
      Clark, G. and C. Allen, "The Estimation of Atmospheric Radiation for Clear and Cloudy
      Skies," Proceedings 2nd National Passive Solar Conference (AS/ISES), 1978, pp. 675-678.