New satellite dataset provides water vapour isotope observations with daily global coverage even above low clouds

Naturally occurring stable water isotopes can be used to track the movement of water. The measurement of these isotopes is difficult but promises new insights in the hydrological cycle. The common isotope H₂O and the molecule with one deuterium atom instead of a hydrogen atom, HDO, can be detected from satellites by their spectroscopic signature. A new satellite data set that provides observations of these two water vapour isotopes from the European Space Agency’s Tropospheric Monitoring Instrument (TROPOMI) also above low clouds for the first time has now been presented in the journal Atmospheric Measurement Techniques.

The publication validates the satellite observations with ground-based measurements, including measurements done at the Finnish Meteorological Institute’s Arctic Space Centre in Sodankylä, Finland. It also demonstrates first applications with global monthly means and presents a case study of the daily evolution of a cold-air outbreak over cloudy scenes over the Atlantic Ocean.

The study has shown that a calibration of the ground-based reference measurements is necessary. A new project lead by the Finnish Meteorological Institute named Water vapour Isotopologue Flask sampling for the Validation Of Satellite data (WIFVOS) will do just that by developing and deploying a novel balloon-borne flask sampler for the measurement of water vapour isotopes. The project is funded by the European Space Agency (ESA).

Further information:

Andreas Schneider, Researcher, Finnish Meteorological Institute, andreas.schneider@fmi.fi

Rigel Kivi, Researcher, Finnish Meteorological Institute, rigel.kivi@fmi.fi

Reference: Schneider, A., Borsdorff, T., aan de Brugh, J., Lorente, A., Aemisegger, F., Noone, D., Henze, D., Kivi, R., and Landgraf, J. 2022. Retrieving H₂O/HDO columns over cloudy and clear-sky scenes from the Tropospheric Monitoring Instrument (TROPOMI), Atmos. Meas. Tech., 15, 2251–2275, 2022. https://doi.org/10.5194/amt-15-2251-2022

Scientific article is available on Atmospheric Measurement Techniques.

Picture: Global distributions of atmospheric H₂O (upper panel) and the relative difference of the observed ratio of HDO and H₂O to the ratio in mean ocean water (δD, lower panel) averaged over the month September 2018 in a 0.5° x 0.5° grid.