Effects of improvements in near‐infrared water vapour line intensities on short‐wave atmospheric absorption

Abstract

The impact of updates of spectroscopic data on the short‐wave absorption by atmospheric water vapour is examined and compared to line parameters from the 1996 edition of HITRAN database. First, the impact of the 1999 HITRAN update to near‐infrared water vapour line intensities was examined. Second, new measurements of water vapour absorption for the 0.82‐ and 0.94‐µm bands are updated in the model. The HITRAN‐99 parameters cause a globally and annually averaged increase in short‐wave absorption of 0.26 Wm−2 with values for a particular month and latitude reaching 0.41 Wm−2. The new measurements lead to a globally and annually averaged increase of 0.64 Wm−2, reaching almost 1 Wm−2 in a particular month and latitude. These two cases increase the total short‐wave absorption by the atmosphere by between 0.4 and 1 %. They contribute to resolving the discrepancy between observed and modelled short‐wave absorption and indicate a need for the spectral data for other near‐infrared and visible bands of water vapour to be re‐examined.