The NASA Carbon Airborne Flux Experiment (CARAFE): Instrumentation and Methodology

Wolfe, G. M.; Kawa, S. Randy; Hanisco, T. F.; Hannun, Reem A.; Newman, Paul A.; Swanson, Andrew; Bailey, Steve; Barrick, J. D.; Thornhill, K. L.; Diskin, G. S.; DiGangi, J. P.; Nowak, John B.; Sorenson, Carl; Bland, G.; Yungel, James K.; Swenson, C. A.

doi:10.5194/amt-2017-398

Cited by 6 publications

(6 citation statements)

References 46 publications

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“…Although some effort is made to capture subgrid variability by combining tower clusters (e.g., IMN, BON) and similar ecosystems (e.g., Figure ) and by examining sensitivity to spatial resolution (e.g., Figure S1), we caution that spatial representativeness issues remain in the flux tower–model comparisons. Airborne eddy covariance surveys provide a viable option to increase footprint size toward regional scale (Wolfe et al., ); (iii) flux partitioning of eddy covariance NEE into GPP and TER also carries large uncertainties and can yield very different results depending on method (e.g., Figure S1). This uncertainty in itself may explain the short time lags between thaw and GPP observed at Bonanza Creek.…”

Section: Discussionmentioning

confidence: 99%

Spring photosynthetic onset and net CO₂ uptake in Alaska triggered by landscape thawing

Parazoo

Arneth

Pugh

et al. 2018

Global Change Biology

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The springtime transition to regional-scale onset of photosynthesis and net ecosystem carbon uptake in boreal and tundra ecosystems are linked to the soil freeze-thaw state. We present evidence from diagnostic and inversion models constrained by satellite fluorescence and airborne CO from 2012 to 2014 indicating the timing and magnitude of spring carbon uptake in Alaska correlates with landscape thaw and ecoregion. Landscape thaw in boreal forests typically occurs in late April (DOY 111 ± 7) with a 29 ± 6 day lag until photosynthetic onset. North Slope tundra thaws 3 weeks later (DOY 133 ± 5) but experiences only a 20 ± 5 day lag until photosynthetic onset. These time lag differences reflect efficient cold season adaptation in tundra shrub and the longer dehardening period for boreal evergreens. Despite the short transition from thaw to photosynthetic onset in tundra, synchrony of tundra respiration with snow melt and landscape thaw delays the transition from net carbon loss (at photosynthetic onset) to net uptake by 13 ± 7 days, thus reducing the tundra net carbon uptake period. Two global CO inversions using a CASA-GFED model prior estimate earlier northern high latitude net carbon uptake compared to our regional inversion, which we attribute to (i) early photosynthetic-onset model prior bias, (ii) inverse method (scaling factor + optimization window), and (iii) sparsity of available Alaskan CO observations. Another global inversion with zero prior estimates the same timing for net carbon uptake as the regional model but smaller seasonal amplitude. The analysis of Alaskan eddy covariance observations confirms regional scale findings for tundra, but indicates that photosynthesis and net carbon uptake occur up to 1 month earlier in evergreens than captured by models or CO inversions, with better correlation to above-freezing air temperature than date of primary thaw. Further collection and analysis of boreal evergreen species over multiple years and at additional subarctic flux towers are critically needed.

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Section: Discussionmentioning

confidence: 99%

Spring photosynthetic onset and net CO₂ uptake in Alaska triggered by landscape thawing

Parazoo

Arneth

Pugh

et al. 2018

Global Change Biology

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“…The airborne vertical flux of HPMTF was computed using the EC technique using the CWT method (44)(45)(46). CWT methods for computing EC flux have emerged as a powerful technique in airborne flux studies, as it does not require homogeneity or stationarity over the averaging period and because it preserves time information, allowing for the computed flux to resolve changes over heterogeneous surfaces (44,45,47). All EC flux determinations for HPMTF were performed at 1-Hz time resolution.…”

Section: Methodsmentioning

confidence: 99%

Rapid cloud removal of dimethyl sulfide oxidation products limits SO ₂ and cloud condensation nuclei production in the marine atmosphere

Novak

Fite²,

Holmes³

et al. 2021

Proc. Natl. Acad. Sci. U.S.A.

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Oceans emit large quantities of dimethyl sulfide (DMS) to the marine atmosphere. The oxidation of DMS leads to the formation and growth of cloud condensation nuclei (CCN) with consequent effects on Earth’s radiation balance and climate. The quantitative assessment of the impact of DMS emissions on CCN concentrations necessitates a detailed description of the oxidation of DMS in the presence of existing aerosol particles and clouds. In the unpolluted marine atmosphere, DMS is efficiently oxidized to hydroperoxymethyl thioformate (HPMTF), a stable intermediate in the chemical trajectory toward sulfur dioxide (SO2) and ultimately sulfate aerosol. Using direct airborne flux measurements, we demonstrate that the irreversible loss of HPMTF to clouds in the marine boundary layer determines the HPMTF lifetime (τHPMTF < 2 h) and terminates DMS oxidation to SO2. When accounting for HPMTF cloud loss in a global chemical transport model, we show that SO2 production from DMS is reduced by 35% globally and near-surface (0 to 3 km) SO2 concentrations over the ocean are lowered by 24%. This large, previously unconsidered loss process for volatile sulfur accelerates the timescale for the conversion of DMS to sulfate while limiting new particle formation in the marine atmosphere and changing the dynamics of aerosol growth. This loss process potentially reduces the spatial scale over which DMS emissions contribute to aerosol production and growth and weakens the link between DMS emission and marine CCN production with subsequent implications for cloud formation, radiative forcing, and climate.

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“…For the EC analysis, we used a custom-made MATLAB toolbox made available to us by Wolfe et al (2018;hereafter referred to as W2018) who also used it for airborne EC. Only minor modifications were necessary to adapt the scripts to our dataset.…”

Section: Eddy Covariance Analysismentioning

confidence: 99%

Airborne flux measurements of ammonia over the Southern Great Plains using chemical ionization mass spectrometry

Schobesberger

D’Ambro

Vettikkat

et al. 2022

Preprint

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Abstract. Ammonia (NH3) is an abundant trace gas in the atmosphere and an important player in atmospheric chemistry, aerosol formation and the atmosphere-surface exchange of nitrogen. It is recognized as a major source of aerosol pollution, and it may limit the formation of cloud nuclei in remote or cold parts of the atmosphere. For soil and plants, NH3-mediated nitrogen can act as a harmful pollutant or as a desirable nutrient, mostly in natural and agricultural settings, respectively. Agriculture is also the main source of atmospheric NH3 via volatilization from fertilizers and manure processing in livestock farming. The accurate determination of NH3 emission rates remains a challenge, partly due to the propensity of NH3 to interact with instrument surfaces leading to high detection limits and slow response times. In this paper, we present a new method for quantifying ambient NH3, using chemical ionization mass spectrometry (CIMS) with deuterated benzene cations as reagents. The setup aimed at limiting sample-surface interactions and achieved a 1-σ precision of 10–20 pptv and an immediate 1/e response rate < 0.4 s, which compares favorably to the existing state of the art. The sensitivity exhibited an inverse humidity dependence, in particular in relatively dry conditions. Background of up to 10 % of the total signal required consideration as well, as it responded on the order of a few minutes. To showcase the method’s capabilities, we quantified NH3 mixing ratios from measurements obtained during deployment on a Gulfstream I aircraft during the HI-SCALE (Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems) field campaign in rural Oklahoma during May 2016. Typical mixing ratios were 1–10 parts per billion by volume (ppbv) for the boundary layer and 0.1–1 ppbv in the lower free troposphere. Sharp plumes of up to 10s of ppbv of NH3 were encountered as well. We identified two of their sources as a large fertilizer plant and a cattle farm, and our mixing ratio measurements yielded upper bounds of 350 ± 50 and 0.6 kg NH3 h–1 for their respective momentary source rates. The fast response of the CIMS also allowed us to derive vertical NH3 fluxes within the turbulent boundary layer via eddy covariance, for which we chiefly used the continuous wavelet transform technique. As expected for a region dominated by agriculture, we observed predominantly upward fluxes, implying net NH3 emissions from surface. The corresponding analysis focused on the most suitable flight, which contained two straight-and-level legs at ~300 m above ground. We derived NH3 fluxes between –4 and 18 mol km–2 h–1 for these legs, at an effective spatial resolution of 1–2 km. The analysis demonstrated how flux measurements benefit from suitably arranged flight tracks with sufficiently long straight-and-level legs, and explores the detrimental effect of measurement discontinuities. Following flux footprint estimations, comparison to the NH3 area emissions inventory provided by the US Environmental Protection Agency indicated overall agreement, but also the absence of some sources, for instance the identified cattle farm. Our study concludes that high-precision CIMS measurements are a powerful tool for in-situ measurements of ambient NH3 mixing ratios, and even allow for the airborne mapping of the air-surface exchange of NH3.

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The NASA Carbon Airborne Flux Experiment (CARAFE): Instrumentation and Methodology

Cited by 6 publications

References 46 publications

Spring photosynthetic onset and net CO₂ uptake in Alaska triggered by landscape thawing

Spring photosynthetic onset and net CO₂ uptake in Alaska triggered by landscape thawing

Rapid cloud removal of dimethyl sulfide oxidation products limits SO ₂ and cloud condensation nuclei production in the marine atmosphere

Airborne flux measurements of ammonia over the Southern Great Plains using chemical ionization mass spectrometry

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The NASA Carbon Airborne Flux Experiment (CARAFE): Instrumentation and Methodology

Cited by 6 publications

References 46 publications

Spring photosynthetic onset and net CO2 uptake in Alaska triggered by landscape thawing

Spring photosynthetic onset and net CO2 uptake in Alaska triggered by landscape thawing

Rapid cloud removal of dimethyl sulfide oxidation products limits SO 2 and cloud condensation nuclei production in the marine atmosphere

Airborne flux measurements of ammonia over the Southern Great Plains using chemical ionization mass spectrometry

Contact Info

Product

Resources

About

Spring photosynthetic onset and net CO₂ uptake in Alaska triggered by landscape thawing

Spring photosynthetic onset and net CO₂ uptake in Alaska triggered by landscape thawing

Rapid cloud removal of dimethyl sulfide oxidation products limits SO ₂ and cloud condensation nuclei production in the marine atmosphere