Atmospheric absorption of terahertz radiation and water vapor continuum effects

Slocum, David; Slingerland, Elizabeth J.; Giles, Robert H.; Goyette, Thomas M.

doi:10.1016/j.jqsrt.2013.04.022

Cited by 147 publications

(81 citation statements)

References 29 publications

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“…The submillimetre's fractional contribution to the total energy incident at the ground from the nadir direction is small (below 0.5 %), but not insignificant, accounting for a larger proportion of the total radiance in colder and drier conditions (black line). To put this into context the downwards flux resulting from an isotropic radiance field (Flux = π Radiance) for both of these cases is about 0.6 Wm −2 , which is approximately equal to the total energy imbalance of the Earth (Smith et al, 2015;Hansen et al, 2011). For maximum accuracy across the whole longwave spectrum the submillimetre would benefit from the same rigorous treatment applied to other regions to provide confidence that it is sufficiently well represented by radiative transfer algorithms in line-by-line and global climate models.…”

Section: Submillimetre Atmospheric Observationsmentioning

confidence: 99%

“…To our knowledge, the equivalent has not been performed in the region between 1100-10 500 GHz. Terahertz continua have been measured under controlled conditions in the laboratory (Slocum et al, 2013;Podobedov et al, 2008); however, the exact atmospheric conditions and composition of the air is difficult to reproduce without in situ measurements. Therefore, continuum models at submillimetre wavelengths are determined by analytical continuation of values determined in other regions.…”

Section: Submillimetre Atmospheric Observationsmentioning

confidence: 99%

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Simulation of submillimetre atmospheric spectra for characterising potential ground-based remote sensing observations

et al. 2016

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Abstract. 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 • ) clearsky 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 2 ) and nitrous oxide (N 2 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 2 produce brightness temperature peaks in the mK to µK range, whereas the N 2 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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Section: Submillimetre Atmospheric Observationsmentioning

confidence: 99%

Section: Submillimetre Atmospheric Observationsmentioning

confidence: 99%

Simulation of submillimetre atmospheric spectra for characterising potential ground-based remote sensing observations

et al. 2016

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“…Another recent surge in interest in technology at this frequency range has appeared recently due to the saturation of the "classical radio window" in telecommunications (Hosako et al 2007). For this reason, atmospheric models for absorption of THz photons (Rosenkranz 1998, Slocum et al 2013 and artifact removal models (Withayachumnankul et al 2008) have been developed. Countries near the Equator face a challenge in using this frequency band for astronomical observations and telecommunications using terabit satellite links (Suen 2016) due to the presence of a tropical belt of dense water vapor which efficiently absorbs THz radiation (Seidel et al 2008).…”

Section: Introductionmentioning

confidence: 99%

“…The lower the elevation of a potential site, the longer the path becomes for that photon, increasing its chances of being absorbed by a water vapor molecule (Liebe 1989, Clough et al 1989, Slocum et al 2013. For this reason, the quality of a site is determined by the atmospheric water vapor column above the potential site (Smith et al 2001, Cimini et al 2007, He et al 2012, Bustos et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Low Dimensional Embedding of Climate Data for Radio Astronomical Site Testing in the Colombian Andes

Molano¹,

Suárez²,

Restrepo

et al. 2017

PASP

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Abstract. We set out to evaluate the potential of the Colombian Andes for millimeter-wave astronomical observations. Previous studies for astronomical site testing in this region have suggested that nighttime humidity and cloud cover conditions make most sites unsuitable for professional visible-light observations. Millimeter observations can be done during the day, but require that the precipitable water vapor column above a site stays below ∼10 mm. Due to a lack of direct radiometric or radiosonde measurements, we present a method for correlating climate data from weather stations to sites with a low precipitable water vapor column. We use unsupervised learning techniques to low-dimensionally embed climate data (precipitation, rain days, relative humidity, and sunshine duration) in order to group together stations with similar long-term climate behavior. The data were taken over a period of 30 years by 2046 weather stations across the Colombian territory. We find 6 regions with unusually dry, clear-sky conditions, ranging in elevations from 2200 to arXiv:1705.06121v4 [astro-ph.IM] 15 Sep 2017Low Dimensional Embedding of Climate Data for Radio Astronomical Site Testing 2 3800 masl. We evaluate the suitability of each region using a quality index derived from a Bayesian probabilistic analysis of the station type and elevation distributions. Two of these regions show a high probability of having an exceptionally low precipitable water vapor column. We compared our results with global precipitable water vapor maps and find a plausible geographical correlation with regions with low water vapor columns (∼ 10 mm) at an accuracy of ∼ 20 km. Our methods can be applied to similar datasets taken in other countries as a first step toward astronomical site evaluation.

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“…2.2. Although there is some work still to be done [2], the atmospheric absorption at THz frequencies is better and better determined by the recent research [14]- [17], showing some transmission windows, but a general highattenuation behavior and a high water vapor continuum absorption spectrum. Thus, THz frequencies are not suitable for long-distance atmospheric transmission as they can be microwave frequencies.…”

Section: Thz Band Fundamental Characteristicsmentioning

confidence: 99%

Analysis and design of efficient passive components for the millimeter-wave and THz bands

Verdú¹,

Antonio²

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To my parents, brother and sister."Success is peace of mind which is a direct result of self-satisfaction in knowing you made the effort to become the best of which you are capable."Jonh Wooden "Lo que con mucho trabajo se adquiere, más se ama." Aristóteles AgradecimientosLa realización de esta tesis ha implicado no pocos años de trabajo y esfuerzo. Durante este importante periodo de mi vida han sido muchas las personas han estado a mi lado, brindándome su apoyo, ayuda, cariño y amor. Ya sea de una forma u otra, todas estas personas han contribuido a que este trabajo haya sido posible dando como fruto esta tesis. A todos ellos, me gustaría dedicarles un agradecimiento muy especial de todo corazón.Sin duda alguna, debo dar las gracias en primer lugar a mi director de tesis Mariano Baquero. Mariano, has sido un padre para mí profesionalmente hablando. Te conocí como alumno en las clases de Microondas, en las cuales me abriste la puerta a un conocimiento que me fascinó.Recuerdo perfectamente cuando fui a verte para preguntarte si podrías dirigirme el Proyecto Final de Carrera, y desde ese año 2009 hemos estado trabajando juntos. Quiero agradecerte no sólo haberme dado la oportunidad de trabajar en cada momento en elárea que más me ha gustado, sino el haberte preocupado por mí a nivel personal, velando siempre por mis intereses, ayudándome a desarrollarme personal y profesionalmente. Extiendo en este sentido mi agradecimiento a Miguel Ferrando. Si Mariano es el padre, tu serías sin duda el abuelo. Sin tu ayuda, la beca para la realización de esta tesis y los proyectos que han respaldado la misma no hubieran sido posibles. Tu esfuerzo ha permitido que el Grupo de Radiación Electromagnética (GRE) esté hoy dónde esta y que sus miembros nos beneficiemos de un entorno de trabajo excelente, produciendo trabajo de calidad. Debo agradecerte también tus siempre innovadoras ideas, algunas de las cuales se han convertido en una realidad plasmada en esta tesis.Una mención especial merece Daniel Sánchez. Dani, aunque tu nombre no figure como co-director bien sabes que podría estarlo. Jamás podré agradecerte lo suficiente la ayuda que me has prestado. Cuántas horas dedicadas a enseñarme en un sin fin de aspectos sin esperar nada a cambio, apoyándome también en los momentos difíciles, siempre presentes en una tesis. Bien sabes que lo mismo has hecho con cada uno tus compañeros, por eso eres el pilar del GRE Dani.Otra persona a la que estoy muy agradecido es a Vicente Boria. Tu activa colaboración en la dirección de esta tesis ha sido indispensable para la consecución de los resultados más relevantes de la misma. Sugeriste muy acertadamente una estancia en la Queen's University of Belfast, y me abriste la puerta a nuevas líneas de investigación en las cuales seguimos trabajando actualmente. Gracias por preocuparte por mi a nivel profesional y personal.En elámbito anterior, extiendo los agradecimientos a todo el GRE. It is also very important for me to acknowledge Prof. Vince Fusco. Thank you for hosting me in your group in Belfast ...

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Atmospheric absorption of terahertz radiation and water vapor continuum effects

Cited by 147 publications

References 29 publications

Simulation of submillimetre atmospheric spectra for characterising potential ground-based remote sensing observations

Simulation of submillimetre atmospheric spectra for characterising potential ground-based remote sensing observations

Low Dimensional Embedding of Climate Data for Radio Astronomical Site Testing in the Colombian Andes

Analysis and design of efficient passive components for the millimeter-wave and THz bands

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