Terahertz and Far-Infrared Windows Opened at Dome A, Antarctica

TL;DR

This study demonstrates that Dome A in Antarctica offers unique atmospheric windows in the terahertz and far-infrared bands, enabling ground-based astronomical observations and improving climate models by providing new spectral absorption data.

Contribution

The paper provides the first comprehensive measurements of atmospheric transmission in the 20 to 350 micron range at Dome A, revealing significant windows and challenging existing water vapor absorption models.

Findings

Identification of atmospheric windows with high transmission in the terahertz and FIR bands.

New constraints on water vapor spectral absorption at upper tropospheric temperatures.

Current models underestimate water vapor continuum absorption.

Abstract

The terahertz and far-infrared (FIR) band, from approximately 0.3 THz to 15 THz (1 mm to 20 micron), is important for astrophysics as the thermal radiation of much of the universe peaks at these wavelengths and many spectral lines that trace the cycle of interstellar matter also lie within this band. However, water vapor renders the terrestrial atmosphere opaque to this frequency band over nearly all of the Earth's surface. Early radiometric measurements below 1 THz at Dome A, the highest point of the cold and dry Antarctic ice sheet, suggest that it may offer the best possible access for ground-based astronomical observations in the terahertz and FIR band. To address uncertainty in radiative transfer modelling, we carried out measurements of atmospheric radiation from Dome A spanning the entire water vapor pure rotation band from 20 micron to 350 micron wavelength by a Fourier transform spectrometer. Our measurements expose atmospheric windows having significant transmission throughout this band. Furthermore, by combining our broadband spectra with auxiliary data on the atmospheric state over Dome A, we set new constraints on the spectral absorption of water vapor at upper tropospheric temperatures important for accurately modeling the terrestrial climate. In particular, we find that current spectral models significantly underestimate the H2O continuum absorption.