Airborne laser absorption spectroscopy is used to determine water isotope ratios for D/H, 18O/16O, and 17O/16O in and out of cirrus clouds to help understand the moisture transported from troposphere into the stratosphere. Possible mechanisms include the tropopause minimum temperature, cloud physics, convection, and mixing of high and low altitude air parcels. Understanding of these mechanisms is one of the important remaining challenges in Earth science.
This work was reported in “Water Isotope Ratios D/H, 18O/16O, and 17O/16O in and out of Clouds Map Dehydration Pathways” by Christopher R. Webster, and Andrew J. Heymsfield in Science volume 302, number 5651 (5 December 2003) pages 1742 – 1745. (Legal Notice)