The influence of water vapor absorption in the 290-350 nm region on solar radiance: Laboratory studies and model simulation

Abstract

Water vapor is an important greenhouse gas in the Earth's atmosphere. Absorption of solar radiation by water vapor in the near-UV region may partially account for up to 30% discrepancy between the modeled and the observed solar energy absorbed by the atmosphere. But the magnitude of water vapor absorption in the near-UV region at wavelengths shorter than 384 nm is not known. We have determined absorption cross sections of water vapor at 5 nm intervals in the 290-350 nm region, by using cavity ring-down spectroscopy. Water vapor cross-section values range from 2.94 × 10-24 to 2.13 × 10-25 cm2/molecule in the wavelength region studied. The effect of the water vapor absorption in the 290-350 nm region on the modeled radiation flux at the ground level has been evaluated using radiative transfer model. Key Points Water vapor near-UV absorption can affect solar flux at the ground ©2013. American Geophysical Union. All Rights Reserved.