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1. Short-term variability of atmospheric helium revealed through a cryo-enrichment method

   https://doi.org/10.5194/amt-16-1551-2023  

   Birner, Benjamin ; Morgan, Eric ; Keeling, Ralph F. ( January 2023 , Atmospheric Measurement Techniques)

   Chen, Huilin (Ed.)

   Abstract. Tropospheric helium variations are tightly linked to CO2 due to the co-emission of He and CO2 from natural-gasburning. Recently, Birner et al. (2022a) showed that the global consumption of natural gas has measurably increased the He content of theatmosphere. Like CO2, He is also predicted to exhibit complex spatial and temporal variability on shorter timescales, butmeasurements of these short-term variations are lacking. Here, we present the development of an improved gas delivery and purification system for thesemi-continuous mass spectrometric measurement of the atmospheric He-to-nitrogen ratio (He/N2). The method replaces the chemicalgetter used previously by Birner et al. (2021, 2022a) to preconcentrate He in an air stream with a cryogenic trap which can be more simplyregenerated by heating and which improves the precision of the measurement to 22 per meg (i.e., 0.022 ‰) in10 min (1σ). Using this “cryo-enrichment” method, we measured the He/N2 ratios in ambient air at La Jolla (California,USA) over 5 weeks in 2022. During this period, He/N2 was strongly correlated with atmospheric CO2 concentrations, as expectedfrom anthropogenic emissions, with a diurnal cycle of 450–500 per meg (max–min) caused by the sea–land breeze pattern of local winds,which modulates the influence of local pollution sources.

    

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2. Deriving column-integrated thermospheric temperature with the N₂ Lyman–Birge–Hopfield (2,0) band

   https://doi.org/10.5194/amt-14-6917-2021  

   Cantrall, Clayton ; Matsuo, Tomoko ( January 2021 , Atmospheric Measurement Techniques)

   Abstract. This paper presents a new technique to derive thermospheric temperature from space-based disk observations of far ultraviolet airglow. The technique, guided by findings from principal component analysis of synthetic daytime Lyman–Birge–Hopfield (LBH) disk emissions, uses a ratio of the emissions in two spectral channels that together span the LBH (2,0) band to determine the change in band shape with respect to a change in the rotational temperature of N2. The two-channel-ratio approach limits representativeness and measurement error by only requiring measurement of the relative magnitudes between two spectral channels and not radiometrically calibrated intensities, simplifying the forward model from a full radiative transfer model to a vibrational–rotational band model. It is shown that the derived temperature should be interpreted as a column-integrated property as opposed to a temperature at a specified altitude without utilization of a priori information of the thermospheric temperature profile. The two-channel-ratio approach is demonstrated using NASA GOLD Level 1C disk emission data for the period of 2–8 November 2018 during which a moderate geomagnetic storm has occurred. Due to the lack of independent thermospheric temperature observations, the efficacy of the approach is validated through comparisons of the column-integrated temperature derived from GOLD Level 1C data with the GOLD Level 2 temperature product as well as temperatures from first principle and empirical models. The storm-time thermospheric response manifested in the column-integrated temperature is also shown to corroborate well with hemispherically integrated Joule heating rates, ESA SWARM mass density at 460 km, and GOLD Level 2 column O/N2 ratio. 

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3. Chlorine-initiated oxidation of <i>n</i>-alkanes under high-NO_<i>x</i> conditions: insights into secondary organic aerosol composition and volatility using a FIGAERO–CIMS

   https://doi.org/10.5194/acp-18-15535-2018  

   Wang, Dongyu S. ; Hildebrandt Ruiz, Lea ( January 2018 , Atmospheric Chemistry and Physics)

   Abstract. Chlorine-initiated oxidation of n-alkanes (C₈₋₁₂) under high-nitrogen oxide conditions was investigated. Observed secondary organic aerosol yields (0.16 to 1.65) are higher than those for OH-initiated oxidation of C₈₋₁₂ alkanes (0.04 to 0.35). A high-resolution time-of-flight chemical ionization mass spectrometer coupled to a Filter Inlet for Gases and AEROsols (FIGAERO–CIMS) was used to characterize the gas- and particle-phase molecular composition. Chlorinated organics were observed, which likely originated from chlorine addition to the double bond present on the heterogeneously produced dihydrofurans. A two-dimensional thermogram representation was developed to visualize the composition and relative volatility of organic aerosol components using unit-mass resolution data. Evidence of oligomer formation and thermal decomposition was observed. Aerosol yield and oligomer formation were suppressed under humid conditions (35% to 67% RH) relative to dry conditions (under 5% RH). The temperature at peak desorption signal, T_max, a proxy for aerosol volatility, was shown to change with aerosol filter loading, which should be constrained when evaluating aerosol volatilities using the FIGAERO–CIMS. Results suggest that long-chain anthropogenic alkanes could contribute significantly to ambient aerosol loading over their atmospheric lifetime.

    

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4. A multi-decade record of high-quality <i>f</i>CO₂ data in version 3 of the Surface Ocean CO₂ Atlas (SOCAT)

   https://doi.org/10.5194/essd-8-383-2016  

   Bakker, Dorothee C. ; Pfeil, Benjamin ; Landa, Camilla S. ; Metzl, Nicolas ; O'Brien, Kevin M. ; Olsen, Are ; Smith, Karl ; Cosca, Cathy ; Harasawa, Sumiko ; Jones, Stephen D. ; et al ( January 2016 , Earth System Science Data)

   Abstract. The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. High-profile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "living data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here: doi:10.3334/CDIAC/OTG.SOCAT_V3_GRID. 

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5. A rapid high‐precision analytical method for triple oxygen isotope analysis of CO 2 gas using tunable infrared laser direct absorption spectroscopy

   https://doi.org/10.1002/rcm.9391  

   Perdue, Nathan ; Sharp, Zachary ; Nelson, David ; Wehr, Rick ; Dyroff, Christoph ( September 2022 , Rapid Communications in Mass Spectrometry)

   The simultaneous analysis of the three stable isotopes of oxygen—triple oxygen isotope analysis—has become an important analytical technique in natural sciences. Determination of the abundance of the rare¹⁷O isotope in CO₂gas using magnetic sector isotope ratio mass spectrometry is complicated by the isobaric interference of¹⁷O by¹³C (¹³C¹⁶O¹⁶O and¹²C¹⁶O¹⁷O, both have mass 45 amu). A number of analytical techniques have been used to measure the¹⁷O/¹⁶O ratio of CO₂gas. They either are time consuming and technically challenging or have limited precision. A rapid and precise alternative to the available analytical methods is desirable.

   We present the results of triple oxygen isotope analyses using an Aerodyne tunable infrared laser direct absorption spectroscopy (TILDAS) CO₂analyzer configured for¹⁶O,¹⁷O, and¹⁸O combined with a custom gas inlet system. We evaluate the sensitivity of our results to a number of parameters. CO₂samples with a wide range of δ¹⁸O values (from −9.28‰ to 39.56‰) were measured and compared to results using the well‐established fluorination‐gas source mass spectrometry method.

   The TILDAS system has a precision (standard error, 2σ) of better than ±0.03‰ for δ¹⁸O and ±10 per meg for Δ′¹⁷O values, equivalent to the precision of previous analytical methods. Samples as small as 3 μmol CO₂(equivalent to 300 μg CaCO₃) can be analyzed with a total analysis time of ~30 min.

   We have successfully developed an analytical technique for the simultaneous determination of the δ¹⁷O and δ¹⁸O values of CO₂gas. The precision is equal to or better than that of existing techniques, with no additional chemical treatments required. Analysis time is rapid, and the system is easily automated so that large numbers of samples can be analyzed with minimal effort.

    

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