Calculation of solar radiative fluxes in the atmosphere: the effect of updates in spectroscopic data

Line-by-line calculations in the spectral region 2 000–20 000 cm (0.5–5 μm) were made to assess the impact of a variety of water vapor spectral databases on the accuracy of solar flux calculation in the atmosphere. The CKD1 and CKD2.4 continuum models were also compared. The maximum disagreement in the calculated solar surface flux due to all the investigated factors can reach 5.9 W/m for midlatitude summer atmosphere and the solar zenith angle 30°. This is ∼ 0.8% of the total downward solar flux at the surface and ∼ 3.3% of the total atmospheric absorption. The dominant cause of this difference is the extra absorption caused by weak lines, which are not included on the HITRAN databases.