The calculation of the clear-sky radiation, Rso, when n = N, is required for computing net longwave radiation.
cal_skySolarRadiation_withas_bs(as, bs, Ra)
A vector for clear-sky solar radiation [MJ m-2 day-1].
as+bs fraction of extraterrestrial radiation reaching the earth on clear-sky days (n = N).
extraterrestrial radiation [MJ m-2 day-1]. From cal_extraterrestrialRadiation_for_daily()
Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. FAO Irrigation and drainage paper No. 56. Rome: Food and Agriculture Organization of the United Nations, 1998.