Water vapor isotopologue retrievals from high-resolution GOSAT shortwave infrared spectra

Abstract

Remote sensing of the isotopic composition of water vapor can provide valuable information on the hydrological cycle. Here, we demonstrate the feasibility of retrievals of the relative abundance of HDO (the HDO/H<sub>2</sub>O ratio) from the Japanese GOSAT satellite. For this purpose, we use high spectral resolution nadir radiances around 6400 cm<sup>−1</sup> (1.56 μm) to retrieve vertical column amounts of H<sub>2</sub>O and HDO. Retrievals of H<sub>2</sub>O correlate well with ECMWF (European Centre for Medium-Range Weather Forecasts) integrated profiles (<i>r</i><sup>2</sup> = 0.96). Typical precision errors in the retrieved column-averaged deuterium depletion (δD) are 20–40‰. We compare δD against a TCCON (Total Carbon Column Observing Network) ground-based station in Lamont, Oklahoma. Using retrievals in very dry areas over Antarctica, we detect a small systematic offset in retrieved H<sub>2</sub>O and HDO column amounts and take this into account for a bias correction of δD. Monthly averages of δD in the June 2009 to September 2011 time frame are well correlated with TCCON (<i>r</i><sup>2</sup> = 0.79) and exhibit a slope of 0.98 (1.23 if not bias corrected). We also compare seasonal averages on the global scale with results from the SCIAMACHY instrument in the 2003–2005 time frame. Despite the lack of temporal overlap, seasonal averages in general agree well, with spatial correlations (<i>r</i><sup>2</sup>) ranging from 0.62 in September through November to 0.83 in June through August. However, we observe higher variability in GOSAT δD, indicated by fitted slopes between 1.2 and 1.46. The discrepancies are likely related to differences in vertical sensitivities but warrant further validation of both GOSAT and SCIAMACHY and an extension of the validation dataset

Comparison of XH2O Retrieved from GOSAT Short-Wavelength Infrared Spectra with Observations from the TCCON Network

“…Versions 01.xx and 02.xx of the XCO 2 and XCH 4 products have been extensively validated [17,20,[26][27][28]. Independent algorithms developed separately are also used routinely to retrieve profile or column information from the TANSO-FTS spectra for CO 2 , CH 4 and, in some cases, H 2 O and deuterated water (HDO) [29][30][31][32]. However, the NIES XH 2 O data are still considered a research product.…”

Multispectral information from TANSO-FTS instrument – Part 1: Application to greenhouse gases (CO<sub>2</sub> and CH<sub>4</sub>) in clear sky conditions

“…Even if this instrument is mainly dedicated to CO 2 and CH 4 measurement, its instrumental qualities (spectral range, spectral resolution and signal-to-noise ratio) could enable detection of number of other species such as water vapor isotopologues HDO, H 2 18 O or H 2 17 O (see Fig. 1 and Frankenberg et al, 2013). …”

Variations of oxygen-18 in West Siberian precipitation during the last 50 years

“…Ground-based remote sensing of δ 18 O in water vapour has been realized recently but so far, only a small number of measurements have been carried out. For this reason we consider global observations of deuterium (δD) in total column water vapour retrieved from the GOSAT satellite (Boesch et al, 2013;Frankenberg et al, 2013) for the period April 2009 to June 2011. We select only measurements which pass a series of quality criteria involving the absence of clouds and the retrieval precision for different species Risi et al, 2013).…”