Vertical profile observations of water vapor deuterium excess in the lower troposphere

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By Olivia E. Salmon1, Lisa R. Welp1, Michael E. Baldwin1, Kristian Hajny1, Brian H. Stirm1, Paul B. Shepson1

Purdue University

Airborne vertical profile measurements of water vapor stable isotopes to examine how boundary layer, cloud, and mixing processes influence the vertical structure of deuterium-excess in the lower troposphere.

Version 1.0 - published on 15 Aug 2019 doi:10.4231/1MZN-1C18 - cite this Archived on 15 Sep 2019

Licensed under CC0 1.0 Universal

Description

These datasets for Indianaopolis and Washington D.C. support the forthcoming article: Salmon, O. E., Welp, L. R., Baldwin, M., Hajny, K., Stirm, B. H., and Shepson, P. B.: Vertical profile observations of water vapor deuterium excess in the lower troposphere, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-1313, in review, 2019.

We use H2Ov isotopic vertical profile measurements and complementary meteorological observations to examine how boundary layer, cloud, and mixing processes influence the vertical structure of deuterium-excess (d-excess = δD – 8 × δ18O) in the boundary layer, inversion layer, and lower free troposphere. Airborne measurements of water vapor (H2Ov) stable isotopologues were conducted around two continental U.S. cities in February–March 2016. Nine research flights were designed to characterize the δD, δ18O, and d-excess vertical profiles extending from the surface to ≤ 2 km. We examine observations from three unique case study flights in detail. One case study shows H2Ov isotopologue vertical profiles that are consistent with Rayleigh isotopic distillation theory coinciding with clear skies, dry adiabatic lapse rates within the boundary layer, and relatively constant vertical profiles of wind speed and wind direction. The two remaining case studies show that H2Ov isotopic signatures above the boundary layer are sensitive to cloud processes and complex air mass mixing patterns. These two case studies indicate anomalies in the d-excess signature relative to Rayleigh theory, such as low d-excess values at the interface of the inversion layer and the free troposphere, which is possibly indicative of cloud evaporation. We discuss possible explanations for the observed d-excess anomalies, such as cloud evaporation, wind shear, and vertical mixing. In situ H2Ov stable isotope measurements, and d-excess in particular, could be useful for improving our understanding of moisture processing and transport mixing occurring between the boundary layer, inversion layer, and free troposphere.

For related datasets, please see the Yale University Stable Water Vapor Isotopes Database.

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