scholarly journals Studying boundary layer methane isotopy and vertical mixing processes at a rewetted peatland site using an unmanned aircraft system

2020 ◽  
Vol 13 (4) ◽  
pp. 1937-1952 ◽  
Author(s):  
Astrid Lampert ◽  
Falk Pätzold ◽  
Magnus O. Asmussen ◽  
Lennart Lobitz ◽  
Thomas Krüger ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Distribution ◽  
Isotopic Composition ◽  
Water Samples ◽  
Vertical Mixing ◽  
Temperature Inversion ◽  
Mixing Processes ◽  
Air Masses ◽  
The Vertical Distribution ◽  
Different Altitudes

Abstract. The combination of two well-established methods, of quadrocopter-borne air sampling and methane isotopic analyses, is applied to determine the source process of methane at different altitudes and to study mixing processes. A proof-of-concept study was performed to demonstrate the capabilities of quadrocopter air sampling for subsequently analysing the methane isotopic composition δ13C in the laboratory. The advantage of the system compared to classical sampling on the ground and at tall towers is the flexibility concerning sampling location, and in particular the flexible choice of sampling altitude, allowing the study of the layering and mixing of air masses with potentially different spatial origin of air masses and methane. Boundary layer mixing processes and the methane isotopic composition were studied at Polder Zarnekow in Mecklenburg–West Pomerania in the north-east of Germany, which has become a strong source of biogenically produced methane after rewetting the drained and degraded peatland. Methane fluxes are measured continuously at the site. They show high emissions from May to September, and a strong diurnal variability. For two case studies on 23 May and 5 September 2018, vertical profiles of temperature and humidity were recorded up to an altitude of 650 and 1000 m, respectively, during the morning transition. Air samples were taken at different altitudes and analysed in the laboratory for methane isotopic composition. The values showed a different isotopic composition in the vertical distribution during stable conditions in the morning (delta values of −51.5 ‰ below the temperature inversion at an altitude of 150 m on 23 May 2018 and at an altitude of 50 m on 5 September 2018, delta values of −50.1 ‰ above). After the onset of turbulent mixing, the isotopic composition was the same throughout the vertical column with a mean delta value of −49.9 ± 0.45 ‰. The systematically more negative delta values occurred only as long as the nocturnal temperature inversion was present. During the September study, water samples were analysed as well for methane concentration and isotopic composition in order to provide a link between surface and atmosphere. The water samples reveal high variability on horizontal scales of a few tens of metres for this particular case. The airborne sampling system and consecutive analysis chain were shown to provide reliable and reproducible results for two samples obtained simultaneously. The method presents a powerful tool for distinguishing the source process of methane at different altitudes. The isotopic composition showed clearly depleted delta values directly above a biological methane source when vertical mixing was hampered by a temperature inversion, and different delta values above, where the air masses originate from a different footprint area. The vertical distribution of methane isotopic composition can serve as tracer for mixing processes of methane within the atmospheric boundary layer.

scholarly journals Studying boundary layer methane isotopy and vertical mixing processes at a rewetted peatland site by unmanned aircraft system

2019 ◽  
Author(s):  
Astrid Lampert ◽  
Falk Pätzold ◽  
Magnus O. Asmussen ◽  
Lennart Lobitz ◽  
Thomas Krüger ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Distribution ◽  
Isotopic Composition ◽  
Water Samples ◽  
Isotopic Signature ◽  
Unmanned Aircraft ◽  
Mixing Processes ◽  
Two Samples ◽  
Methane Fluxes ◽  
The Vertical Distribution

Abstract. A proof of concept study was performed to demonstrate the capabilities of quadrocopter air sampling for analysing the methane isotopic composition in the laboratory. Boundary layer mixing processes and the methane isotopic composition were studied with a quadrocopter system at Polder Zarnekow in Mecklenburg–West Pomerania in the North East of Germany, which has become a strong source of biogenically produced methane after rewetting the drained and degraded peatland. Methane fluxes are measured continuously at the site. They show high emissions from May to September, and a strong diurnal variability with maximum methane fluxes up to 2 μmol m−2 s−1 for summer 2018. For two case studies on 23 May 2018 and 5 September 2018, vertical profiles of temperature and humidity were recorded up to an altitude of 650 m and 1000 m, respectively, during the morning transition. Air samples were taken at different altitudes and analysed in the laboratory for methane isotopic composition. The values showed a different isotopic signature in the vertical distribution during stable conditions in the morning (−51.5 ‰ below the temperature inversion at an altitude of 150 m on 23 May 2018 and at an altitude of 50 m on 5 September 2018, −50.1 ‰ above). After the onset of turbulent mixing, the isotopic signature was the same throughout the vertical column with a mean value of −49.9 ± 0.45 ‰. During the September study, water samples were analysed as well for methane concentration and isotopic composition in order to provide a link between surface and atmosphere. The water samples reveal high variability on scales of few 10 m for this particular case. The airborne sampling system and consecutive analysis chain were shown to provide reliable and reproducible results for two samples obtained simultaneously. The method presents a powerful tool for constraining the origin of methane by analysing its isotopic signature, and for measuring the vertical distribution of methane isotopic signature, which is based on mixing processes of methane within the atmospheric boundary layer.

Two Inversion Layers and Their Impacts on PM2.5 Concentration over the Yangtze River Delta, China

2019 ◽  
Vol 58 (11) ◽  
pp. 2349-2362 ◽  
Author(s):  
Yiwen Xu ◽  
Bin Zhu ◽  
Shuangshuang Shi ◽  
Yong Huang
Keyword(s):  
Boundary Layer ◽  
Vertical Distribution ◽  
Rural Area ◽  
Yangtze River ◽  
Layer Structure ◽  
Yangtze River Delta ◽  
Emission Sources ◽  
The Yangtze River ◽  
The Vertical Distribution ◽  
The Yangtze River Delta

AbstractAn integrated winter field campaign was conducted to investigate the atmospheric boundary layer structure and PM2.5 concentration at three sites over the Yangtze River delta (YRD) in China: Shouxian (a rural area), a site in a northern suburb of Nanjing, and Dongshan (a residential area). Two temperature inversion layers and air pollution events occurred simultaneously from 30 to 31 December 2016, local time, over the YRD. It was found that the two inversion layers were related to the presence of a high pressure system, resulting in divergence in the upper boundary layer and radiative cooling near the ground at night. Dominated by agricultural and residential biomass burning, the surface emission sources from the Shouxian rural area were moderately strong. After the formation of the two inversions, the vertical distribution of PM2.5 concentration below the upper inversion layer was uniform as a result of thorough boundary layer mixing in the earlier hours. During nighttime at the Nanjing site, air pollutant plumes from nearby elevated point sources could not easily diffuse downward/upward between the two inversion layers, which led to a distinct peak in the PM2.5 concentration. At the Dongshan site, the emission sources were weak and the nighttime PM2.5 concentration above 100 m was high. The surface PM2.5 concentration gradually increased from early morning to noon, which was attributed to emissions related to the local residents. The results indicated that the vertical distribution of pollutants was affected by a combination of local emissions, vertical boundary layer structure, and horizontal and vertical transports.

scholarly journals Linking Meteorology, Turbulence, and Air Chemistry in the Amazon Rain Forest

2016 ◽  
Vol 97 (12) ◽  
pp. 2329-2342 ◽  
Author(s):  
Jose D. Fuentes ◽  
Marcelo Chamecki ◽  
Rosa Maria Nascimento dos Santos ◽  
Celso Von Randow ◽  
Paul C. Stoy ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Surface Layer ◽  
Vertical Distribution ◽  
Rain Forest ◽  
Forest Canopy ◽  
Cloud Condensation Nuclei ◽  
Chemical Species ◽  
Chemical Transformations ◽  
Condensation Nuclei ◽  
The Vertical Distribution

Abstract We describe the salient features of a field study whose goals are to quantify the vertical distribution of plant-emitted hydrocarbons and their contribution to aerosol and cloud condensation nuclei production above a central Amazonian rain forest. Using observing systems deployed on a 50-m meteorological tower, complemented with tethered balloon deployments, the vertical distribution of hydrocarbons and aerosols was determined under different boundary layer thermodynamic states. The rain forest emits sufficient reactive hydrocarbons, such as isoprene and monoterpenes, to provide precursors of secondary organic aerosols and cloud condensation nuclei. Mesoscale convective systems transport ozone from the middle troposphere, enriching the atmospheric boundary layer as well as the forest canopy and surface layer. Through multiple chemical transformations, the ozone-enriched atmospheric surface layer can oxidize rain forest–emitted hydrocarbons. One conclusion derived from the field studies is that the rain forest produces the necessary chemical species and in sufficient amounts to undergo oxidation and generate aerosols that subsequently activate into cloud condensation nuclei.

scholarly journals Characterization of the <sup>222</sup>Rn family turbulent transport in the convective atmospheric boundary layer

2007 ◽  
Vol 7 (3) ◽  
pp. 697-712 ◽  
Author(s):  
J.-F. Vinuesa ◽  
S. Galmarini
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Vertical Distribution ◽  
Turbulent Transport ◽  
Radioactive Decay ◽  
Atmospheric Boundary Layers ◽  
Eddy Simulation ◽  
The One ◽  
The Vertical Distribution ◽  
Unsteady Conditions

Abstract. The combined effect of turbulent transport and radioactive decay on the distribution of 222Rn and its progeny in convective atmospheric boundary layers (CBL) is investigated. Large eddy simulation is used to simulate their dispersion in steady state CBL and in unsteady conditions represented by the growth of a CBL within a pre-existing reservoir layer. The exact decomposition of the concentration and flux budget equations under steady state conditions allowed us to determine which processes are responsible for the vertical distribution of 222Rn and its progeny. Their mean concentrations are directly correlated with their half-life, e.g. 222Rn and 210Pb are the most abundant whereas 218Po show the lowest concentrations. 222Rn flux decreases linearly with height and its flux budget is similar to the one of inert emitted scalar, i.e., a balance between on the one hand the gradient and the buoyancy production terms, and on the other hand the pressure and dissipation at smaller scales which tends to destroy the fluxes. While 222Rn exhibits the typical bottom-up behavior, the maximum flux location of the daughters is moving upwards while their rank in the 222Rn progeny is increasing leading to a typical top-down behavior for 210Pb. We also found that the relevant radioactive decaying contributions of 222Rn short-lived daughters (218Po and 214Pb) act as flux sources leading to deviations from the linear flux shape. In addition, while analyzing the vertical distribution of the radioactive decay contributions to the concentrations, e.g. the decaying zone, we found a variation in height of 222Rn daughters' radioactive transformations. Under unsteady conditions, the same behaviors reported under steady state conditions are found: deviation of the fluxes from the linear shape for 218Po, enhanced discrepancy in height of the radioactive transformation contributions for all the daughters. In addition, 222Rn and its progeny concentrations decrease due to the rapid growth of the CBL. The analysis emphasizes the crucial role of turbulent transport in the behavior of 222Rn n morning concentrations, in particular the ventilation at the top of the boundary layer that leads to the dilution of 222Rn by mixing with radon low concentration air.

scholarly journals Seasonal and Diurnal Variations in Aerosol Concentration on Whistler Mountain: Boundary Layer Influence and Synoptic-Scale Controls

2011 ◽  
Vol 50 (11) ◽  
pp. 2210-2222 ◽  
Author(s):  
John P. Gallagher ◽  
Ian G. McKendry ◽  
Anne Marie Macdonald ◽  
W. Richard Leaitch
Keyword(s):  
Boundary Layer ◽  
Meteorological Data ◽  
Warm Season ◽  
Weather Conditions ◽  
Careful Analysis ◽  
Median Number ◽  
Synoptic Scale ◽  
Mixing Processes ◽  
Air Masses ◽  
Seasonal And Diurnal Variations

AbstractA mountain air chemistry observatory has been operational on the summit of Whistler Mountain in British Columbia, Canada, since 2002. A 1-yr dataset of condensation nuclei (CN) concentration from this site has been analyzed along with corresponding meteorological data to assess the frequency and patterns of influence from the planetary boundary layer (PBL). Characterization of air masses sampled from the site as either PBL influenced or representative of the free troposphere (FT) is important to subsequent analysis of the chemistry data. Median CN concentrations and seasonal trends were found to be comparable to other midlatitude mountain sites. Monthly median number concentrations ranged from 120 cm−3 in January to 1601 cm−3 in July. Using well-defined diurnal cycles in CN concentration as an indicator of air arriving from nearby valleys, PBL influence was found to occur on a majority of days during spring and summer and less frequently in late autumn and winter. Days with PBL influence were usually associated with synoptic-scale weather patterns that were conducive to convective mixing processes. Although more common in the warm season, vertical mixing capable of transporting valley air to the mountaintop also occurred in February during a period of high pressure aloft. In contrast, an August case study indicated that the more stable character of marine air masses can at times keep the PBL below the summit on summer days. Considerable variability in the synoptic-scale weather conditions at Whistler means that careful analysis of available datasets must be made to discriminate FT from PBL periods at the observatory.

scholarly journals An Ocean Modeling Study To Quantify Wind Forcing and Oceanic Mixing Effects on The Tropical North Pacific Subsurface Warm Bias in CMIP and OMIP Simulations

2021 ◽  
Author(s):  
Yuchao Zhu ◽  
Rong-Hua Zhang ◽  
Delei Li
Keyword(s):  
Boundary Layer ◽  
North Pacific ◽  
Thermal Structure ◽  
Vertical Mixing ◽  
Upper Ocean ◽  
Subsurface Temperature ◽  
Mixing Processes ◽  
Warm Bias ◽  
The Past ◽  
Upper Boundary

Abstract Sea surface temperature (SST) bias in the climate models has been a focus in the past, but subsurface temperature biases have not been received much attention yet. In this study, subsurface temperature biases in the Tropical North Pacific (TNP) are investigated by analyzing the CMIP6, CMIP5 and OMIP products, and performing ocean model simulations. It is found that almost all the CMIP and OMIP simulations have a pronounced subsurface warm bias (SWB) in the northeastern tropical Pacific (NETP), and the model developments over the past decade do not indicate obvious improvements in bias pattern and magnitude from CMIP5 to the latest version CMIP6. This SWB is primarily caused by the model deficiencies in the simulated surface wind stress curl (WSC) in the NETP, which is too weak to produce a sufficient Ekman upwelling, a bias that also exists in OMIP simulations. The uncertainties in the parameterizations of the oceanic vertical mixing processes also make a great contribution, and it is demonstrated that the estimated oceanic vertical diffusivities are overestimated both in the upper boundary layer and the interior in the CMIP and OMIP simulations. The relationship between the SWB and the misrepresented oceanic vertical mixing processes are investigated by conducting several ocean-only experiments, in which the upper boundary layer mixing is modified by reducing the wind stirring effect in the Kraus-Turner type bulk mixed-layer approach, and the interior mixing is constrained by using the Argo-derived diffusivity. By applying these modifications to oceanic vertical mixing schemes, the SWB is greatly reduced in the NETP. The consequences of this SWB are further analyzed. Because the thermal structure in the NETP can influence the simulations of oceanic circulations and equatorial upper-ocean thermal structure, the large SWB in the CMIP6 models tends to produce a weak equatorward water transport in the subsurface TNP, a weak equatorial upwelling and a warm equatorial upper ocean.

scholarly journals Vertical distribution of sub-micron aerosol chemical composition from North-Western Europe and the North-East Atlantic

2009 ◽  
Vol 9 (2) ◽  
pp. 9117-9150
Author(s):  
W. T. Morgan ◽  
J. D. Allan ◽  
K. N. Bower ◽  
G. Capes ◽  
J. Crosier ◽  
...  
Keyword(s):  
Organic Matter ◽  
Chemical Composition ◽  
Vertical Distribution ◽  
Western Europe ◽  
Vertical Profiles ◽  
East Atlantic ◽  
Air Masses ◽  
North East ◽  
The North ◽  
The Vertical Distribution

Abstract. A synthesis of UK based airborne in-situ measurements of aerosol properties representing air masses from North-West Europe and the North-East Atlantic is presented. The major focus of the study is the vertical distribution of sub-micron aerosol chemical composition. Vertical profiles are derived from a Quadrupole Aerosol Mass Spectrometer (Q-AMS). Background sub-micron aerosol vertical profiles are identified and are primarily composed of organic matter and sulphate aerosol. Such background conditions occurred predominantly during periods associated with long-range air mass transport across the Atlantic. These instances may serve as useful model input of aerosol to Western Europe. Increased mass concentration episodes are coincident with European outflow and periods of stagnant/recirculating air masses. Such periods are characterised by significantly enhanced concentrations of nitrate aerosol relative to those of organic matter and sulphate. Periods of enhanced ground level PM2.5 loadings are coincident with instances of high nitrate mass fractions measured on-board the aircraft, indicating that nitrate is a significant contributor to regional pollution episodes. The vertical structure of the sulphate and organic aerosol profiles were shown to be primarily driven by large-scale dynamical processes. The vertical distribution of nitrate is likely determined by both dynamic and thermodynamic processes, with chemical partitioning of gas phase precursors to the particle phase occurring at lower temperatures at the top of the boundary layer. Such effects have profound implications for the aerosol's lifetime and subsequent impacts, highlighting the requirement for accurate representation of the aerosol vertical distribution.

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