Absorption cross-sections in HITRAN2016 database: extensive update in the infrared for climate, environment, and atmospheric applications

Accounting for volatile organic compounds (VOCs) is crucial for many applications, including, for example, climate change monitoring, tracking of pollution and biomass burning, and atmospheric remote sensing. For many such molecules, the line-by-line spectroscopic data are still either unavailable, or incomplete. The spectroscopic databases, however, often give the wavenumber-dependent absorption cross-sections for each temperature and pressure set. In this paper we give a detailed overview for the current state of the HITRAN2016 infrared absorption cross-section part. The updated cross-sections include data for around 320 compounds, with more than 260 compounds being included in the database for the first time. These cross-sections come from high-resolution laboratory observations, predominantly from Fourier transform spectrometers. The update largely relies on spectra from the Pacific Northwest National Laboratory quantitative spectroscopic database and the Hodnebrog et al. (Rev Geophys 2013) compilation, but also on other recently published data. We give a description for the most atmospherically important compounds arranged by chemical categories, and validate the existing data sources for many of them. We also describe the HITRAN infrastructure which gives access to the data for all molecules from HITRAN, and discuss the best practices of searching the data. This update increases the amount of molecules in the HITRAN database almost six-fold compared to the previous edition, HITRAN2012; it is available via the HITRANonline website (www.hitran.org) and HITRAN Application Programming Interface (HAPI).