Introduction of water-vapor broadening coefficients and their temperature dependence exponents into the HITRAN database, Part I: CO2, N2O, CO, CH4, O2, NH3, and H2S

TL;DR

This paper compiles and reviews water-vapor broadening coefficients and their temperature dependence for key atmospheric molecules, updating the HITRAN database to improve spectral modeling of water-rich atmospheres.

Contribution

It introduces a comprehensive set of water-vapor broadening parameters and models into HITRAN, based on experimental and theoretical data for multiple molecules.

Findings

Water vapor broadening coefficients were systematically collected and reviewed.

Semi-empirical models were developed to estimate broadening and temperature dependence.

Updated parameters enhance spectral analysis of water-rich atmospheres.

Abstract

The amount of water vapor in the terrestrial atmosphere is highly variable both spatially and temporally. In the tropics it sometimes constitutes 4-5% of the atmosphere. At the same time collisional broadening of spectral lines by water vapor is much larger than that by nitrogen and oxygen. Therefore, in order to accurately characterize and model spectra of the atmospheres with significant amounts of water vapor, the line-shape parameters for spectral lines broadened by water vapor are required. In this work, the line-broadening coefficients (and their temperature dependence exponents) due to the pressure of water vapor for lines of CO2, N2O, CO, CH4, O2, NH3, and H2S from both experimental and theoretical studies were collected and carefully reviewed. A set of semi-empirical models based on these collected data was created and then used to estimate water broadening and its temperature dependence for all transitions of selected molecules in the HITRAN2016 database.