Remote Sensing of the isotopic composition of water vapor: Application to hydrology and climate

Abstract:

Remotely sensed measurements of water vapor and its isotopologues are inferred by how these molecules spectrally affect light as it is transferred from some source (e.g., the sun, the earth, or a laser), through the atmosphere, to a detector.

Consequently, the use of satellite or ground based remotely sensed measurements of the isotopic composition of water vapor to investigate the global water cycle depends on the viewing geometry, photon source, and instrument characteristics which in turn affects the vertical resolution of the measurement and choice of regularization used to infer these quantities from a spectral radiance. Users of these data must therefore take these aspects formally into account when comparing these remotely sensed data to models or independent measurements.

In this presentation I will summarize how profiles of the HDO/H₂O ratio are inferred from Aura Tropospheric Emission Spectrometer thermal IR radiances and then how to account for the vertical resolution and regularization used in this “retrieval” when comparing to other models and data. In particular I will show comparisons of these satellite data to aircraft and model profiles of HDO and H₂O as well as discuss previous and ongoing research into the global water cycle, climate, and paleo-climate that use these data.