Temperature-Dependence of the Near-UV Absorption of Water Vapor in the 290-350 nm Range

• Water vapor absorption cross-sections were measured in the 290 − 350 nm range. • Cross-sections are in the range of 10 −24 − 10 −25 cm 2 /molecule over 290 − 350 nm. • Water vapor near-UV absorption cross-sections vary significantly with temperature. • Effect of water vapor absorption on UV O 3 retrieval was modeled for tropics. • Effect of water vapor near-UV absorption on surface irradiance was modeled. Water vapor plays a critical role in the energy balance of the Earth's atmosphere. But there are limited experimental measurements of single photon water vapor absorption spectra and absorption strengths in the near-UV region. We determined the temperature-dependent absorption cross-sections of water vapor at 1 nm increments in the 290–350 nm range by using cavity ring-down spectroscopy. Water vapor exhibited structured absorption bands in this region, with cross-sections ranging from 1.4 × 10 −25 to 6.0 × 10 −25 cm 2 /molecule at 283 K; 1.6 × 10 −25 to 8.9 × 10 −25 cm 2 /molecule at 313 K; and 1.9 × 10 −25 to 1.0 × 10 −24 cm 2 /molecule at 333 K. A radiative transfer model was used to evaluate atmospheric impacts of water vapor near-UV absorption using laboratory temperature-dependent cross-section data.