Earth and Planetary Sciences ETDs

Publication Date



The water cycle in the tropics and subtropics exerts a strong influence on Earth's climate. Isotopic ratios in modern water vapor can provide us with insights into low-latitude moisture-transport processes in the modern climate system, recorded in paleoclimate proxy records, and in general circulation models that we rely on to understand how our climate is changing. Advances in satellite and groundbased instruments in the past decade have improved measurements of isotopes in water vapor. In this study, I focus on satellite (chapters 2 and 3) and ground-based (chapters 2 and 4) measurements of isotopes in atmospheric water vapor to evaluate processes responsible for moisture transport in tropical and subtropical South America. Satellite-measured hydrogen isotope ratios (δD), mixing ratios (q), and outgoing longwave radiation (OLR) show that upwind convective intensity controls the seasonal variability in isotopic ratios in tropical Andean water vapor and leads to lower isotopic ratios than predicted by equilibrium isotope fractionation models (i.e. DδD = δDmeasured - δDRayleigh < 0°) (chapter 2). Deep convection in the South American Summer Monsoon domain in austral summer and in the Inter-tropical Convergence Zone in austral winter leads to zones where DδD is negative from the Lifted Condensation Level through the mid- to upper-troposphere and possibly above the Level of Neutral Buoyancy (chapter 3). In subtropical South America, nearly continuous measurements of isotopic ratios, mixing ratios, and deuterium-excess (i.e. d-excess = δD – (8*δ18O)) indicate that condensation under ice supersaturated conditions and mixing with moister air play important roles in controlling moisture transport to the hyperarid Chajnantor Plateau.

Degree Name

Earth and Planetary Sciences

Level of Degree


Department Name

Department of Earth and Planetary Sciences

First Committee Member (Chair)

Sharp, Zachary

Second Committee Member

Gutzler, David

Third Committee Member

Hardy, Douglas

Project Sponsors

National Science Foundation, New Mexico EPSCoR



Document Type