Effect of water vapour absorption on hydroxyl temperatures measured from Svalbard

Chadney, Joshua; Whiter, Daniel; Lanchester, B. S.

doi:10.5194/angeo-35-481-2017

Cited by 5 publications

(12 citation statements)

References 31 publications

(43 reference statements)

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“…Sigernes et al, 2003;Phillips et al, 2004;Holmen et al, 2014). Using the HiTIES instrument, we observe OH lines from the (8-3) vibrational band in the O + panel (Chadney et al, 2017) and from the (5-4) and (9-1) bands in the OH panel.…”

Section: Oh Airglowmentioning

confidence: 96%

“…A given temperature retrieval is rejected if the linear fit to P 1 line variance is greater than 0.05 or if the linear fit to P 2 line variance is over 0.3. For more information on this process, see Chadney et al (2017).…”

Section: Oh Airglowmentioning

confidence: 99%

“…This process, which is described further in Sect. 4 and Chadney et al (2017), also provides us with an estimate of the column density of water vapour in the atmosphere: the precipitable water vapour (PWV).…”

Section: Oh Airglowmentioning

confidence: 99%

“…3.1, but also for each O + and N 2 emission line. The HITRAN (Rothman et al, 2013) spectral database is used to determine the H 2 O absorption cross section, and water vapour absorption in the column of atmosphere above the instrument is calculated using the Beer-Lambert law (see Chadney et al, 2017). We parameterise water vapour absorption with the coefficient ς given for the OH and O + lines in Table 1, which is related to absorption (a λ ) and transmission (t λ ) coefficients by the following:…”

Section: Fitting Processmentioning

confidence: 99%

“…In this way, neutral temperatures have been determined from observations of airglow emissions from the OH layer located near the mesopause (e.g. French et al, 2000;Phillips et al, 2004;Suzuki et al, 2010;Holmen et al, 2014;Chadney et al, 2017). It has also been possible to measure rotational temperatures from N + 2 ions observed during aurorae (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

Chadney

Whiter

2018

Geosci. Instrum. Method. Data Syst.

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We have developed a spectral fitting method to retrieve upper atmospheric parameters at multiple altitudes simultaneously during times of aurora, allowing us to measure neutral temperatures and column densities of water vapour. We use the method to separate airglow OH emissions from auroral O + and N 2 in observations between 725 and 740 nm using the High Throughput Imaging Echelle Spectrograph (HiTIES) located on Svalbard. In this paper, we describe our new method and show the results of Monte Carlo simulations using synthetic spectra which demonstrate the validity of the spectral fitting method and provide an indication of uncertainties on the retrieval of each atmospheric parameter. We show that the method allows for the retrieval of OH temperatures with an uncertainty of 6 % when contamination by N 2 emission is small. N 2 temperatures can be retrieved with uncertainties down to 3 %-5 % when N 2 emission intensity is high. We can determine the intensity ratio between the O + doublets at 732 and 733 nm (which is a function of temperature) with an uncertainty of 5 %.Published by Copernicus Publications on behalf of the European Geosciences Union.

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Section: Oh Airglowmentioning

confidence: 96%

Section: Oh Airglowmentioning

confidence: 99%

Section: Oh Airglowmentioning

confidence: 99%

Section: Fitting Processmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

Chadney

Whiter

2018

Geosci. Instrum. Method. Data Syst.

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High‐Resolution Optical Observations of Neutral Heating Associated With the Electrodynamics of an Auroral Arc

et al. 2019

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We present results that indicate the existence of two distinct neutral heating processes associated with a discrete auroral arc over Svalbard. Within the order of seconds, the thermospheric temperature profile displays a significant response to the arc on spatial scales smaller than 10 km. It is suggested that both heating signatures are associated with the electrodynamic system responsible for the formation of the arc. Pedersen currents produce a temperature increase of approximately 100 K, observed at altitudes between 80 and 160 kilometres, directly adjacent to the arc structure and on its poleward edge only. In contrast, field-aligned currents produce a variable temperature increase, of approximately 50 K, which is observed within the arc itself and constrained to a narrow altitude range between 90 and 110 km. By utilizing a range of observations and new analysis methods we are able to measure the atmospheric neutral temperature profile, over auroral altitudes, at unprecedented temporal and spatial scales. The High Throughput Imaging Echelle Spectrograph records high-resolution emission spectra of the aurora, which are then fitted with synthetic N 2 spectra, generated with modeled N 2 volume emission rate profiles and a library of trial temperature profiles. The N 2 volume emission rate profiles are retrieved from the Southampton ionospheric model using precipitating particle energies and fluxes obtained from Auroral Structure and Kinetics and the EISCAT Svalbard Radar. The application of this technique allows us to produce a time series of neutral temperature profiles and measure the localized heating of the neutral atmosphere resulting from the electrodynamics of the arc. Key Points: • Development of a new observing technique allows for the measurement of neutral temperature profiles during auroral events at an unprecedented temporal resolution • A case study of a morning sector auroral arc over Svalbard reveals a region of significant Joule heating on its poleward edge • Evidence of a separate Ohmic heating signature embedded within the arc and associated with strong field aligned currents Supporting Information: • Supporting Information S1

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Method for retrieval of atmospheric water vapor using OH airglow for correction of astronomical observations

Liu

Bian

et al. 2020

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Context. Water vapor in the atmosphere undergoes quick spatial and temporal variations. This has a serious impact on ground-based astronomical observations from the visible band to the infrared band resulting from water vapor attenuation and emission. Aims. We seek to show how the sky spectrum of an astronomical observation can be used to determine the amount of precipitable water vapor (PWV) along the line of sight toward the science target. Methods. In this work, we discuss a method to retrieve the PWV from the OH(8-3) band airglow spectrum. We analyzed the influences of the pressure and temperature of the atmosphere and the different water vapor vertical distributions on the PWV retrieval method in detail. Meanwhile, the accuracy of the method was analyzed via Monte Carlo simulations. To further verify the method of PWV retrieval, we carried out cross comparisons between the PWV retrieved from OH airglow and PWV from the standard star spectra of UVES using equivalent widths of telluric absorption lines observed from 2000 to 2016 at Cerro Paranal in Chile. Results. The Monte Carlo tests and the comparison between the two different methods prove the availability the PWV retrieval method from OH airglow. These results show that using OH airglow spectra in astronomical observations, PWVs along the same line of sight as the astronomical observations can be retrieved in real time. Conclusions. We provide a quick and economical method for retrieving the water vapor along the same line of sight of astronomical observation in the real time. This is especially helpful to correcting the effect of water vapor on astronomical observations.

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Effect of water vapour absorption on hydroxyl temperatures measured from Svalbard

Cited by 5 publications

References 31 publications

Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

High‐Resolution Optical Observations of Neutral Heating Associated With the Electrodynamics of an Auroral Arc

Method for retrieval of atmospheric water vapor using OH airglow for correction of astronomical observations

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