Atlas of ACE spectra of clouds and aerosols

Lecours, Michael J.; Bernath, Peter F.; Sorensen, Jason J.; Boone, C. D.; Johnson, Ryan M.; Labelle, Keith

doi:10.1016/j.jqsrt.2022.108361

Cited by 10 publications

(8 citation statements)

References 34 publications

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“…In satellite-and aircraft-based infrared measurements, however, only -NAT has been clearly identified, e.g. by its signature at 820 cm -1 (Höpfner et al, 2006;Woiwode et al, 2016;Woiwode et al, 2019;Lecours et al, 2022;Lecours et al, 2023). The new data set of optical constants for -NAD clearly does not question this assignment, since the 2(NO3 -) mode in -NAD is located at 812 cm -1 .…”

Section: Discussionmentioning

confidence: 89%

“…The distinctive PSC spectral signature at a wavenumber of 820 cm -1 , corresponding to the 2 symmetric deformation mode of the NO3ion (Spang and Remedios, 2003), could be best matched by refractive index data for -NAT (Höpfner et al, 2006). The -NAT phase was also identified in broadband infrared transmittance spectra recorded between 4400 and 750 cm -1 with the Fourier transform spectrometer on board the Atmospheric Chemistry Experiment (ACE) satellite (Lecours et al, 2022;Lecours et al, 2023).…”

mentioning

confidence: 81%

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Particle shapes and infrared extinction spectra of nitric acid dihydrate crystals: Optical constants of the β-NAD modification

Wagner

James

Frankland

et al. 2023

Preprint

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Abstract. Satellite- and aircraft-based mid-infrared measurements of polar stratospheric clouds (PSCs) have provided spectroscopic evidence for the presence of β-NAT (nitric acid trihydrate) particles. Metastable nitric acid hydrate phases such as α-NAT and α-NAD (nitric acid dihydrate) have been frequently observed in laboratory experiments, but not yet detected as a constituent of PSCs in atmospheric measurements. As for the β-NAD modification, its formation was first observed in X-ray diffraction measurements when the low-temperature α-NAD phase was warmed to a temperature above 210 K. Its infrared spectrum has been reported, but so far no optical constants have been derived that could be used as input for infrared retrievals of PSC composition. In this work, we show that β-NAD particles were efficiently formed in isothermal, heterogeneous crystallisation experiments at 190 K from supercooled HNO3/H2O solution droplets containing an embedded mineral dust or meteoric smoke particle analogue. An inversion algorithm based on a T-matrix optical model was used to derive for the first time the mid-infrared complex refractive indices of the β-NAD modification from the measured extinction spectrum of the particles. In contrast to the heterogeneous crystallisation experiments, the α-NAD phase was formed when the HNO3/H2O solution droplets did not contain a solid nucleus and crystallised homogeneously. Using a light scattering detector that recorded two-dimensional scattering patterns of the crystallised NAD particles, we were able to determine predominant shapes of the α- and β-NAD crystals. We found that α-NAD grew into elongated, needle-shaped crystals, while β-NAD particles were compact in shape. This agrees with previously reported images of α- and β-NAD particles grown on the cryo-stage of an Environmental Scanning Electron Microscope.

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Section: Discussionmentioning

confidence: 89%

mentioning

confidence: 81%

Particle shapes and infrared extinction spectra of nitric acid dihydrate crystals: Optical constants of the β-NAD modification

Wagner

James

Frankland

et al. 2023

Preprint

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“…Figure S7 in Supporting Information shows an example of an ash‐NAT mixture where there are clearly NAT features such as the sharp 820 cm −1 peak and the signature NAT shape to the spectrum from 2,000 to 4,400 cm −1 . Figure 6 in L22 shows an example of pure ash from PCCC. There is also a strong 1,100 cm −1 silicate feature typical of volcanic ash.…”

Section: Resultsmentioning

confidence: 99%

“…The resulting residual spectrum is then classified by composition, using the fact that each aerosol type will generate a unique spectral shape in the infrared see Lecours et al. (2022); Lecours et al. (2023) hereby referred to as L22 and L23.…”

Section: Methodsmentioning

confidence: 99%

“…The calculated spectrum consists of all known gas-phase contributions, employing spectroscopic data from the HITRAN 2020 database (Gordon et al, 2022) and VMR profiles taken from ACE-FTS version 5.2 retrievals (Boone et al, 2023). The resulting residual spectrum is then classified by composition, using the fact that each aerosol type will generate a unique spectral shape in the infrared see Lecours et al (2022); Lecours et al (2023) hereby referred to as L22 and L23.…”

Section: Methodsmentioning

confidence: 99%

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Antarctic Polar Stratospheric Cloud Analysis of ACE‐FTS Data From 2005 to 2023

Lecours,

Boone,

Bernath

2024

JGR Atmospheres

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We present an analysis of Antarctic polar winters from 2005 to 2023 as observed by the Atmospheric Chemistry Experiment (ACE). The unique broad band infrared spectral features in ACE “residual” spectra are used to classify the spectra of polar aerosols by composition into polar stratospheric clouds (PSCs) and sulfate aerosols. The spectra of PSCs are further classified into nitric acid trihydrate, supercooled ternary solutions, supercooled nitric acid, ice‐mix, and mixtures of PSCs. A breakdown of PSC composition is presented for each year. Antarctic winter seasons with unusual compositions are: 2011, in which volcanic ash mixed with PSCs was observed from July to August; 2019, which experienced a stratospheric warming event; 2020, the PSC season following the Australian Black Summer pyrocumulonimbus event; and 2023, which had unusually large sulfate aerosols following the Honga‐Tonga Honga Ha'apai eruption of 2022.

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