Simulation of submillimetre atmospheric spectra for characterising potential ground-based remote sensing observations
The submillimetre is an understudied region of the Earth's atmospheric electromagnetic spectrum. Prior technological gaps and relatively high opacity due to the prevalence of rotational water vapour lines at these wavelengths have slowed progress from a ground-based remote sensing perspecti...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-11-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | https://www.atmos-meas-tech.net/9/5461/2016/amt-9-5461-2016.pdf |
| Summary: | The submillimetre is an understudied region of the Earth's atmospheric
electromagnetic spectrum. Prior technological gaps and relatively high
opacity due to the prevalence of rotational water vapour lines at these
wavelengths have slowed progress from a ground-based remote sensing
perspective; however, emerging superconducting detector technologies in the
fields of astronomy offer the potential to address key atmospheric science
challenges with new instrumental methods. A site study, with a focus on the
polar regions, is performed to assess theoretical feasibility by simulating
the downwelling (zenith angle = 0°) clear-sky submillimetre spectrum
from 30 mm (10 GHz) to 150 µm (2000 GHz) at six locations under
annual mean, summer, winter, daytime, night-time and low-humidity conditions.
Vertical profiles of temperature, pressure and 28 atmospheric gases are
constructed by combining radiosonde, meteorological reanalysis and
atmospheric chemistry model data. The sensitivity of the simulated spectra to
the choice of water vapour continuum model and spectroscopic line database is
explored. For the atmospheric trace species hypobromous acid (HOBr), hydrogen
bromide (HBr), perhydroxyl radical (HO<sub>2</sub>) and nitrous oxide (N<sub>2</sub>O)
the emission lines producing the largest change in brightness temperature are
identified. Signal strengths, centre frequencies, bandwidths, estimated
minimum integration times and maximum receiver noise temperatures are
determined for all cases. HOBr, HBr and HO<sub>2</sub> produce brightness
temperature peaks in the mK to µK range, whereas the N<sub>2</sub>O peaks
are in the K range. The optimal submillimetre remote sensing lines for the
four species are shown to vary significantly between location and scenario,
strengthening the case for future hyperspectral instruments that measure over
a broad wavelength range. The techniques presented here provide a framework
that can be applied to additional species of interest and taken forward to
simulate retrievals and guide the design of future submillimetre
instruments. |
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| ISSN: | 1867-1381 1867-8548 |