The terahertz and far-infrared band, ranging from approximately 0.3 THz to 15 THz (1 mm to 20 μm), is important for astrophysics as it hosts the peak of the thermal radiation of the cold component of the Universe as well as many spectral lines that trace the cycle of interstellar matter1–8. However, water vapour makes the terrestrial atmosphere opaque to this frequency band over nearly all of the Earth’s surface9. Early radiometric measurements10 below 1 THz at Dome A (80° 22′ S, 77° 21′ E), the highest point of the cold and dry Antarctic ice sheet, suggest that this site may offer the best possible access for ground-based astronomical observations in the terahertz and far-infrared band. To fully assess the site conditions and to address the uncertainties in radiative transfer modelling of the atmosphere, we carried out measurements of atmospheric radiation from Dome A with a Fourier transform spectrometer, spanning the entire water vapour pure rotation band from 20 μm to 350 μm. Our measurements reveal substantial transmission in atmospheric windows throughout the whole band. By combining our broadband spectra with data on the atmospheric state over Dome A, we set new constraints on the spectral absorption of water vapour at upper tropospheric temperatures, which is important for accurate modelling of the terrestrial climate. We find that current spectral models significantly underestimate the H2O continuum absorption.
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We acknowledge the assistance of the 26th and 27th CHINARE teams supported by the Polar Research Institute of China and the Chinese Arctic and Antarctic Administration, the University of New South Wales PLATO team, the CAS Center for Antarctic Astronomy team and the other teams contributing to the operation of the Dome A facilities, in particular J.W.V. Storey, D.M. Luong-Van, A. Moore, C. Pennypacker, D. York, L. Wang, L. Feng, Z. Zhu, H. Yang, X. Cui, X. Yuan, X. Gong, X. Zhou, X. Liu, Z. Wang, and J. Huang. The exemplary work of D. Naylor and B. Gom of Blue Sky Spectroscopy Inc. and K. Wood of QMC Instruments Inc. is acknowledged. We also acknowledge discussions with D.D. Turner of NOAA on complex-domain calibration of the FTS spectra, and E.J. Mlawer of AER Inc. on the MT_CKD water vapour continuum model and its implementation in the radiative transfer code used in this work. MERRA data used in this study were provided by the Global Modeling and Assimilation Office (GMAO) at NASA Goddard Space Flight Center through the NASA GES DISC online archive. Primary support for this research was provided by the Operation, Maintenance and Upgrading Fund for Astronomical Telescopes and Facility Instruments, funded by the Ministry of Finance of China (MOF) and administered by the CAS. The traverse team was financially supported by the Chinese Polar Environment Comprehensive Investigation & Assessment Program. The PLATO team was funded by the Australian Research Council and the Australian Antarctic Division. Iridium satellite communications were provided by the US National Science Foundation and the US Antarctic Program. Co-authors S.P. and Q.Z. received additional support for this work from Smithsonian Institution Endowment funds and the Smithsonian Competitive Grants Program for Science. Co-author H.M. was supported partly by a visiting professorship of CAS for senior international scientists.
The authors declare no competing financial interests.
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Shi, S., Paine, S., Yao, Q. et al. Terahertz and far-infrared windows opened at Dome A in Antarctica. Nat Astron 1, 0001 (2017). https://doi.org/10.1038/s41550-016-0001
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