Tropospheric HDO/H2O Distribution over the Southeast Atlantic Ocean from Satellite, Aircraft and Model
Abstract
We present new retrievals of the deuterium content of water vapor from the Aqua Atmospheric InfraRed Sounder (AIRS) to be compared with model and aircraft measurements of HDO and H2O. We use the isotope version of the Community Atmosphere Model (CAM). The aircraft measurements come from the "ObseRvations of Aerosols above CLouds and their intEractionS" (ORACLES) field mission.
Single footprint AIRS radiances are processed with an optimal estimation algorithm that provides a vertical profile of the HDO/H2O ratio, characterized uncertainties, and instrument operators (or averaging kernel matrix). These retrievals are compared to vertical profiles of the HDO/H2O from the Oregon State University Water Isotope Spectrometer for Precipitation and Entrainment Research (WISPER) on the ORACLES NASA P-3B Orion aircraft. Airborne measurements were taken over the Southeast Atlantic Ocean from 31 August to 25 September 2016. HDO/H2O is commonly reported in δD notation, which is the fractional deviation of the HDO/H2O ratio from the standard reference ratio (per thousand or ‰). For collocated measurements, the satellite operator (averaging kernels and a priori constraint) is applied to the aircraft profile measurements. We find that AIRS δD bias relative to the aircraft is well within the estimated measurement uncertainty. In the lower troposphere, 1000 to 800 hPa, AIRS δD bias is -6.6‰ and the Root Mean Square (RMS) deviation is 20.9‰, consistent with the calculated uncertainty of 19.1‰. In the mid-troposphere, 800 to 500 hPa, AIRS δD bias is -6.8‰ and RMS 44.9‰, comparable to the calculated uncertainty of 25.8‰. The confidence in the AIRS data that this analysis provides begins to establish the 17-year-long AIRS dataset as offering unprecedented opportunities to evaluate hydrological processes with isotopic constraints- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP23E1681H
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES;
- 1041 Stable isotope geochemistry;
- GEOCHEMISTRY;
- 1655 Water cycles;
- GLOBAL CHANGE;
- 1833 Hydroclimatology;
- HYDROLOGY