Self-broadened half-widths and self-induced line shifts for water vapor transitions in the 3.2–17.76 μm spectral region via complex Robert–Bonamy theory

Abstract

Water vapor in the Earth’s atmosphere is being studied in the 3.2–17.76 μm spectral region by the atmospheric infrared sounder (AIRS) on Aqua, the troposphere emission spectrometer (TES) and the high-resolution dynamics limb sounder (HIRDLS) on Aura, both part of the NASA EOS mission. However, the lack of sufficient data on spectral parameters will hamper the prospect of accurate retrievals of temperature and concentration profiles. The spectral parameters for thousands of water vapor transitions are required, which are hard to determine by measurements alone. As reported previously [Can. J. Chem. 82 (2004) 1013–1027], of the 10 602 measurements of H 2O self-broadening half-widths only 440 intercomparisons with more than 3 data points have estimated uncertainty less than 10%. In this work, we have employed the mean relative thermal velocity approximation of the complex implementation of Robert–Bonamy formalism to obtain the self-broadened half-widths and self-induced line shifts for 5442 water vapor transitions in the 3.2–17.76 μm region. The calculations are compared with the measurement database and trends in the half-widths and line shifts are studied.