Updates of HITRAN spectroscopic database from 2008 to 2016 and implications for near‐infrared radiative transfer calculations

Abstract

Spectroscopic information on atmospheric gases, such as absorption line positions, intensities and widths, is important for radiative transfer calculations in climate and weather models. The widely used HIgh resolution TRANsmission (HITRAN) spectroscopic database is updated regularly. A line‐by‐line radiative transfer model has been used to investigate the impacts of the updates of HITRAN from 2008 to 2016 on clear‐sky calculations of absorption and solar heating rates in the near‐infrared region from 4,000 to 10,000 cm−1 (1.0–2.5 µm). These calculations were carried out for the tropical and sub‐arctic atmospheres at solar zenith angles of 30° and 75° using HITRAN absorption line parameters for H2O, CO2, O3, N2O, CO, CH4 and O2 as well as the MT_CKD 2.5 (Mlawer‐Tobin‐Clough‐Kneizys‐Davies) continua for H2O, CO2, O3 and O2. It was found that the improvements in HITRAN absorption line parameters led to modest increases in the spectrally integrated absorbed downward solar fluxes and heating rates. The differences in absorbed fluxes are larger between HITRAN2016 and HITRAN2008 (maximum difference ∼1.3%) than between HITRAN2016 and HITRAN2012 (largest difference ∼0.3%). The corresponding maximum differences in heating rates are less than 2%. In order to improve accuracy, HITRAN2016 should be used in preference to earlier line‐lists for calculating near‐infrared absorbed solar fluxes and heating rates; but for calculations of clear‐sky heating rates in the near‐infrared region that do not require better than 2% accuracy, line parameters from HITRAN2012 and HITRAN2008 may still be used. Although the revisions of HITRAN led to relatively small differences in the spectrally integrated quantities, the improved quality of near‐infrared line parameters will have a significant impact on other atmospheric applications such as the measurements of CO2 concentrations at a precision of less than 1% in Greenhouse Gases Observatory Satellite (GOSAT) and Orbiting Carbon Observatory‐2 (OCO‐2) missions.