Comparison of optimal estimation HDO/H2O retrievals from AIRS with ORACLES...

Herman, R. L., J. Worden, D. Noone, D. Henze, K. Bowman, K. Cady-Pereira, V. Payne, S. Kulawik, and D. Fu (2020), Comparison of optimal estimation HDO/H2O retrievals from AIRS with ORACLES measurements, Atmos. Meas. Tech., 13, 1825-1834, doi:10.5194/amt-13-1825-2020.

In this paper we evaluate new retrievals of the deuterium content of water vapor from the Aqua Atmospheric InfraRed Sounder (AIRS), with aircraft measurements of HDO and H2 O 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 vertical profiles of the HDO/H2 O ratio, characterized uncertainties and instrument operators (i.e., averaging kernel matrix). These retrievals are compared to vertical profiles of the HDO/H2 O ratio from the Oregon State University Water Isotope Spectrometer for Precipitation and Entrainment Research (WISPER) on the ORACLES NASA P-3B Orion aircraft. Measurements were taken over the southeastern Atlantic Ocean from 31 August to 25 September 2016. HDO/H2 O is commonly reported in D notation, which is the fractional deviation of the HDO/H2 O ratio from the standard reference ratio. For collocated measurements, the satellite instrument operator (averaging kernels and a priori constraint) is applied to the aircraft profile measurements. We find that AIRS D bias relative to the aircraft is well within the estimated measurement uncertainty. In the lower troposphere, 1000 to 800 hPa, AIRS D 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 D bias is 6.8 ‰ and rms 44.9 ‰, comparable to the calculated uncertainty of 25.8 ‰.

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Research Program: 
Terrestrial Hydrology Program (THP)
Atmospheric Composition
Tropospheric Composition Program (TCP)
Energy & Water Cycle Program (EWCP)