An automated system for selective and continuous measurements of vertical thoron profiles for the determination of transport times near the ground

Plake, Daniel; Trebs, Ivonne

doi:10.5194/amt-6-1017-2013

Cited by 5 publications

(17 citation statements)

References 31 publications

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“…However, a site‐specific model like Van Pul and Jacobs () may not capture variability in the resistance to canopy turbulence across different landscapes and boundary‐layer conditions. For example, daytime transport timescales near the ground over a grassland constrained with radon and thoron isotopes are 50% too low with the Van Pul and Jacobs () model (Plake & Trebs, ). In general, multilayer canopy LES models offer an opportunity to explore how turbulent transport influences ozone dry deposition and refine parameterizations.…”

Section: Theory Models and Observations Of Terrestrial Ozone Deposimentioning

confidence: 99%

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Clifton

Fiore

Massman

et al. 2020

Reviews of Geophysics

109

133

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Dry deposition of ozone is an important sink of ozone in near‐surface air. When dry deposition occurs through plant stomata, ozone can injure the plant, altering water and carbon cycling and reducing crop yields. Quantifying both stomatal and nonstomatal uptake accurately is relevant for understanding ozone's impact on human health as an air pollutant and on climate as a potent short‐lived greenhouse gas and primary control on the removal of several reactive greenhouse gases and air pollutants. Robust ozone dry deposition estimates require knowledge of the relative importance of individual deposition pathways, but spatiotemporal variability in nonstomatal deposition is poorly understood. Here we integrate understanding of ozone deposition processes by synthesizing research from fields such as atmospheric chemistry, ecology, and meteorology. We critically review methods for measurements and modeling, highlighting the empiricism that underpins modeling and thus the interpretation of observations. Our unprecedented synthesis of knowledge on deposition pathways, particularly soil and leaf cuticles, reveals process understanding not yet included in widely used models. If coordinated with short‐term field intensives, laboratory studies, and mechanistic modeling, measurements from a few long‐term sites would bridge the molecular to ecosystem scales necessary to establish the relative importance of individual deposition pathways and the extent to which they vary in space and time. Our recommended approaches seek to close knowledge gaps that currently limit quantifying the impact of ozone dry deposition on air quality, ecosystems, and climate.

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Section: Theory Models and Observations Of Terrestrial Ozone Deposimentioning

confidence: 99%

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Clifton

Fiore

Massman

et al. 2020

Reviews of Geophysics

109

133

View full text Add to dashboard Cite

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“…A vertical Thoron (Tn) profile system was operated at z 1 = 0.04, z 2 = 0.2 and z 3 = 0.8 m for the direct determination of transport times (for details see Plake and Trebs, 2013). Vertical profiles of NO, NO 2 , O 3 and CO 2 were measured at z 1 , z 2 , z 3 and additionally at z 4 = 4.0 m by a system described in detail by Plake et al (2014).…”

Section: Methodsmentioning

confidence: 99%

“…The median transport time through the 0.6 m high natural grassland canopy (also referred to as "canopy flushing time") was presented in the related study of Plake and Trebs (2013) for the same experiment. It was measured using the vertical thoron profile between z 1 and z 3 (Eq.…”

Section: Aerodynamic Resistances and Transport Timesmentioning

confidence: 99%

“…We performed an intensive field experiment from July to September 2011 at the estate of the Mainz Finthen Airport in Rhineland-Palatinate, Germany (further details given in Plake and Trebs, 2013;Plake et al, 2014;Moravek et al, 2014Moravek et al, , 2015. The vegetation at the site was nutrient-poor grassland with a mean canopy height (h c ) of 0.6 m and a leaf area index (LAI) of 4.8 m 2 m −2 .…”

Section: Site Descriptionmentioning

confidence: 99%

“…In the canopy, τ tr (L i , i = 1, 2) were derived from the vertical Tn profiles (Lehmann et al, 1999;Plake and Trebs, 2013):…”

Section: Transport Timesmentioning

confidence: 99%

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Influence of meteorology and anthropogenic pollution on chemical flux divergence of the NO–NO<sub>2</sub>–O<sub>3</sub> triad above and within a natural grassland canopy

et al. 2015

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Abstract. The detailed understanding of surface-atmosphere exchange fluxes of reactive trace gases is a crucial precondition for reliable modelling of processes in atmospheric chemistry. Plant canopies significantly impact the atmospheric budget of trace gases. In the past, many studies focused on taller forest canopies or crops, where the bulk plant material is concentrated in the uppermost canopy layer. However, within grasslands, a land-cover class that globally covers vast terrestrial areas, the canopy structure is fundamentally different, as the main biomass is concentrated in the lowest part of the canopy. This has obvious implications for aerodynamic in-canopy transport, and consequently also impacts on global budgets of key species in atmospheric chemistry such as nitric oxide (NO), nitrogen dioxide (NO 2 ) and ozone (O 3 ).This study presents for the first time a comprehensive data set of directly measured in-canopy transport times and aerodynamic resistances, chemical timescales, Damköhler numbers, trace gas and micrometeorological measurements for a natural grassland canopy (canopy height = 0.6 m). Special attention is paid to the impact of contrasting meteorological and air chemical conditions on in-canopy transport and chemical flux divergence. Our results show that the grassland canopy is decoupled throughout the day. In the lowermost canopy layer, the measured transport times are fastest during nighttime, which is due to convection during nighttime and a stable stratification during daytime in this layer. The inverse was found in the layers above. During periods of low wind speed and high NO x (NO+NO 2 ) levels, the effect of canopy decoupling on trace gas transport was found to be especially distinct. The aerodynamic resistance in the lowermost canopy layer (0.04-0.2 m) was around 1000 s m −1 , which is as high as values determined previously for the lowest metre of an Amazonian rain forest canopy. The aerodynamic resistance representing the bulk canopy was found to be more than 3-4 times higher than in forests. Calculated Damköhler numbers (ratio of transport and chemical timescales) suggest a strong flux divergence for the NO-NO 2 -O 3 triad within the canopy during daytime. During that time, the timescale of NO 2 uptake by plants ranged from 90 to 160 s and was the fastest relevant timescale, i.e. faster than the reaction of NO and O 3 . Thus, our results reveal that grassland canopies of similar structure exhibit a strong potential to retain soilemitted NO due to oxidation and subsequent uptake of NO 2 by plants. Furthermore, photo-chemical O 3 production was observed above the canopy, which was attributed to a deviation from the NO-NO 2 -O 3 photostationary state by a surplus of NO 2 due to oxidation of NO, by e.g. peroxy radicals. The O 3 production was one order of magnitude higher during high NO x than during low NO x periods and resulted in an underestimation of the O 3 deposition flux measured with the EC method.Published by Copernicus Publications on behalf of the European Geosciences ...

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Trace Gas Exchange at the Forest Floor

Sörgel

Riederer

Held

et al. 2017

Energy and Matter Fluxes of a Spruce Forest Ecosystem

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Exchange conditions at the forest floor are complex due to the heterogeneity of sources and sinks and the inhomogeneous radiation but are important for linking soil respiration to measurements in the trunk space or above canopy. Far more attention has therefore been paid to above and within canopy flows, but even studies that addressed forest floor exchange do not present measurements below 1 m or 2 m. We used a multilayer model that explicitly resolves the laminar layer, the buffer layer, and the turbulent layer to calculate fluxes from the measured profiles in the lowest meter above ground and to calculate effective surface concentrations from given fluxes. The calculated fluxes were compared to measured eddy covariance fluxes of sensible heat and O3 and to chamber derived soil fluxes of CO2 and 222Rn. Sensible heat fluxes agreed surprisingly well given the heterogeneity of radiative heating and the generally low fluxes (max. 25 W m−2). The chamber fluxes turned out to be not comparable as the chamber fluxes were too low, probably due to one of the well-known problems of enclosures such as pressure differences, disturbed gradients and exclusion of naturally occurring turbulence events and surface cooling. The O3 fluxes agreed well for high O3 values reaching down to the forest floor during full coupling of the canopy by coherent structures. During most of the time, the model overestimated the fluxes as chemical reactions were dominating within the profile. One new approach was to calculate the effective surface concentration from a given flux and compare this to measured surface concentrations. This allowed the identification of situations with a coupled and decoupled forest floor layer, which has important consequences for respiration measurements in the trunk space or above canopy and should be considered in upcoming studies

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An automated system for selective and continuous measurements of vertical thoron profiles for the determination of transport times near the ground

Cited by 5 publications

References 31 publications

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Influence of meteorology and anthropogenic pollution on chemical flux divergence of the NO–NO<sub>2</sub>–O<sub>3</sub> triad above and within a natural grassland canopy

Trace Gas Exchange at the Forest Floor

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An automated system for selective and continuous measurements of vertical thoron profiles for the determination of transport times near the ground

Cited by 5 publications

References 31 publications

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Influence of meteorology and anthropogenic pollution on chemical flux divergence of the NO–NO&lt;sub&gt;2&lt;/sub&gt;–O&lt;sub&gt;3&lt;/sub&gt; triad above and within a natural grassland canopy

Trace Gas Exchange at the Forest Floor

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Influence of meteorology and anthropogenic pollution on chemical flux divergence of the NO–NO<sub>2</sub>–O<sub>3</sub> triad above and within a natural grassland canopy