scholarly journals A comprehensive global dataset of atmospheric <sup>7</sup>Be and <sup>210</sup>Pb measurements: air concentration and depositional flux

2021 ◽  
Author(s):  
Fule Zhang ◽  
Jinlong Wang ◽  
Mark Baskaran ◽  
Qiangqiang Zhong ◽  
Yali Wang ◽  
...  
Keyword(s):  
Geographic Location ◽  
Particle Dynamics ◽  
Published Data ◽  
Air Concentration ◽  
Mixing Processes ◽  
Air Masses ◽  
Public Consumption ◽  
Depositional Flux ◽  
Flux Measurements ◽  
Deposition Processes

Abstract. 7Be and 210Pb air concentration and depositional flux data provide key information on the origins and movements of air masses, as well as deposition processes and residence time of aerosols. After their deposition onto the Earth's surface, they are utilized for tracing soil redistribution processes on land and particle dynamics and mixing processes in the ocean. Here we present a global dataset of air concentration and depositional flux measurements of atmospheric 7Be and 210Pb made by a large number of researchers and laboratories. Data were collected from published papers between 1955 and early 2020. It includes the annual surface air concentrations data of 7Be from 367 sites and of 210Pb from 270 sites, the annual depositional flux of 7Be from 279 sites, and of 210Pb from 602 sites. When available, appropriate metadata have also been summarized, including geographic location, sampling date, methodology, annual precipitation, and references. The dataset is available at https://doi.org/10.5281/zenodo.4521649 (Zhang et al., 2021). The purpose of this paper is to have the published data available in one place for future researchers' public consumption in their research and provide an overview of the scope and nature of this dataset holdings.

scholarly journals A global dataset of atmospheric <sup>7</sup>Be and <sup>210</sup>Pb measurements: annual air concentration and depositional flux

2021 ◽  
Vol 13 (6) ◽  
pp. 2963-2994
Author(s):  
Fule Zhang ◽  
Jinlong Wang ◽  
Mark Baskaran ◽  
Qiangqiang Zhong ◽  
Yali Wang ◽  
...  
Keyword(s):  
Geographic Location ◽  
Future Research ◽  
Air Concentration ◽  
Concentration Data ◽  
Mixing Processes ◽  
Air Masses ◽  
Flux Data ◽  
Depositional Flux ◽  
Flux Measurements ◽  
Deposition Processes

Abstract. 7Be and 210Pb air concentration and depositional flux data provide key information on the origins and movements of air masses, as well as atmospheric deposition processes and residence time of aerosols. After their deposition onto the Earth's surface, they are utilized for tracing soil redistribution processes on land, particle dynamics in aquatic systems, and mixing processes in open ocean. Here we present a global dataset of air concentration and depositional flux measurements of atmospheric 7Be and 210Pb made by a large number of global research communities. Data were collected from published papers between 1955 and early 2020. It includes the annual surface air concentration data of 7Be from 367 sites and 210Pb from 270 sites, the annual depositional flux data of 7Be from 279 sites and 210Pb from 602 sites. When available, appropriate metadata have also been summarized, including geographic location, sampling date, methodology, annual precipitation, and references. The dataset is archived at https://doi.org/10.5281/zenodo.4785136 (Zhang et al., 2021) and is freely available for the scientific community. The purpose of this paper is to provide an overview of the scope and nature of this dataset and its potential utility as baseline data for future research.

3-D tomographic observations of Rossby wave breaking over the Northern Atlantic during the WISE aircraft campaign in 2017

2021 ◽  
Author(s):  
Lukas Krasauskas ◽  
Jörn Ungermann ◽  
Peter Preusse ◽  
Felix Friedl-Vallon ◽  
Andreas Zahn ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Water Vapour ◽  
Rossby Wave ◽  
Wave Breaking ◽  
Thin Filament ◽  
Small Scale ◽  
Data Sets ◽  
Mixing Processes ◽  
Air Masses ◽  
Rossby Wave Breaking

&lt;p&gt;We present measurements of ozone, water vapour and nitric acid in the upper troposphere/lower stratosphere (UTLS) over North Atlantic and Europe. The measurements were acquired with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the Wave Driven Isentropic Exchange (WISE) campaign in October 2017. GLORIA is an airborne limb imager capable of acquiring both 2-D data sets (curtains along the flight path) and, when the carrier aircraft is flying around the observed air mass, spatially highly resolved 3-D tomographic data. We show a case study of a Rossby wave (RW) breaking event observed during two subsequent flights two days apart. RW breaking is known to steepen tracer gradients and facilitate stratosphere-troposphere exchange (STE). Our measurements reveal complex spatial structures in stratospheric tracers (ozone and nitric acid) with multiple vertically stacked filaments. Backward trajectory analysis is used to demonstrate that these features are related to several previous Rossby wave breaking events and that the small-scale structure of the UTLS in the Rossby wave breaking region, which is otherwise very hard to observe, can be understood as stirring and mixing of air masses of tropospheric and stratospheric origin. It is also shown that a strong nitric acid enhancement observed just above the tropopause is likely a result of NO&lt;sub&gt;x&lt;/sub&gt; production by lightning activity. The measurements showed signatures of enhanced mixing between stratospheric and tropospheric air near the polar jet with some transport of water vapour into the stratosphere. Some of the air masses seen in 3-D data were encountered again two days later, stretched to very thin filament (horizontal thickness down to 30&amp;#8201;km at some altitudes) rich in stratospheric tracers. This repeated measurement allowed us to directly observe and analyse the progress of mixing processes in a thin filament over two days. Our results provide direct insight into small-scale dynamics of the UTLS in the Rossby wave breaking region, witch is of great importance to understanding STE and poleward transport in the UTLS.&lt;/p&gt;

Simulation of Fluid Flow in a Microchannel at Low Reynolds Number Using Dissipative Particle Dynamics

2018 ◽  
Author(s):  
Waqas Waheed ◽  
Anas Alazzam ◽  
Ashraf N. Al Khateeb ◽  
Eiyad Abu Nada
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Velocity Profile ◽  
Drag Coefficient ◽  
Dissipative Particle Dynamics ◽  
Particle Dynamics ◽  
Published Data ◽  
Two Dimensional ◽  
Close Match ◽  
Good Agreement

In this paper, a two-dimensional Dissipative Particle Dynamics (DPD) technique to simulate the poiseuille flow in a microchannel is developed using an in-house code. The calculated Reynolds number is reduced via adjusting the DPD parameters. The obtained velocity profile is compared with the analytical results and a good agreement is found. The drag force and the drag coefficient on a stationary cylinder exerted by the fluid particles are obtained using the developed DPD code. The calculated drag coefficient exhibits a close match with already published data in the literature.

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 A Relaxed Eddy Accumulation (REA) LOPAP-System for Flux Measurements of Nitrous Acid (HONO)

2021 ◽  
Author(s):  
Lisa von der Heyden ◽  
Walter Wißdorf ◽  
Ralf Kurtenbach ◽  
Jörg Kleffmann
Keyword(s):  
Nitrous Acid ◽  
Formation Mechanisms ◽  
Minor Importance ◽  
Night Time ◽  
Field Campaign ◽  
Air Masses ◽  
Relaxed Eddy Accumulation ◽  
Photolysis Frequency ◽  
Ultrasonic Anemometer ◽  
Flux Measurements

Abstract. In the present study a Relaxed Eddy Accumulation (REA) system for the quantification of vertical fluxes of nitrous acid (HONO) was developed and tested. The system is based on a three-channel-LOPAP instrument, for which two channels are used for the updrafts and downdrafts, respectively, and a third one for the correction of chemical interferences. The instrument is coupled to a REA gas inlet, for which an ultrasonic anemometer controls two fast magnetic valves to probe the two channels of the LOPAP instrument depending on the vertical wind direction. A software (PyREA) was developed, which controls the valves and measurement cycles, which regularly alternates between REA-, zero- and parallel ambient measurements. In addition, the assignment of the updrafts and downdrafts to the physical LOPAP channels is periodically alternated, to correct for differences in the interferences of the different air masses. During the study, only small differences of the interferences were identified for the updrafts and downdrafts excluding significant errors when using only one interference channel. In laboratory experiments, high precision of the two channels and the independence of the dilution corrected HONO concentrations on the length of the valve switching periods were demonstrated. A field campaign was performed in order to test the new REA-LOPAP system at the TROPOS monitoring station in Melpitz, Germany. HONO fluxes in the range of −4·1013 molecules m−2 s−1 (deposition) to +1.0·1014 molecules m−2 s−1 (emission) were obtained. A typical diurnal variation of the HONO fluxes was observed with low, partly negative fluxes during night-time and higher positive fluxes around noon. After an intensive rain period the positive HONO emissions during daytime were continuously increasing, which was explained by the drying of the upper most ground surfaces. Similar to other campaigns, the highest correlation of the HONO flux was observed with the product of the NO2 photolysis frequency and the NO2 concentration (J(NO2)·[NO2]), which implies a HONO formation by photosensitized conversion of NO2 on organic surfaces, like e.g. humic acids. Other postulated HONO formation mechanisms are also discussed, but are ranked being of minor importance for the present field campaign.

scholarly journals An experimental search for a correlation between outdoor 222Rn concentration and 210Pb activity in air particulate samples

2018 ◽  
Vol 33 (1) ◽  
pp. 112-116 ◽  
Author(s):  
Elio Tomarchio
Keyword(s):  
Gamma Ray ◽  
Experimental Tests ◽  
Air Transport ◽  
Weak Correlation ◽  
Air Concentration ◽  
Air Masses ◽  
222Rn Concentration ◽  
Air Particulate ◽  
210Pb Activity ◽  
Lead 210

This work was aimed to search for a correlation between outdoor 222Rn air concentration and 210Pb activity in particulate samples collected on a filter. The existence of a correlation could support the hypothesis that both 222Rn and its long-lived product 210Pb are embedded into the same air masses and undergo the same air transport phenomena. Lead-210 activity was determined by means of gamma ray spectrometric measurement carried out a few days after the sampling whereas 222Rn concentration was measured through a commercial monitor. Experimental tests allowed to obtain a weak correlation between 222Rn and 210Pb air concentration as a preliminary result due to high uncertainties of outdoor 222Rn concentration measurements.

Prediction of Rheometric Properties of Compounds by Using Artificial Neural Networks

2001 ◽  
Vol 74 (1) ◽  
pp. 116-123 ◽  
Author(s):  
Gustavo Ariel Schwartz
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Prior Information ◽  
Published Data ◽  
Mathematical Treatment ◽  
Mixing Processes ◽  
Optimum Parameters ◽  
Rubber Compounds ◽  
Artificial Neural ◽  
Artificial Neural Network Ann

Abstract The ability of an Artificial Neural Network (ANN) to evaluate the variability of rheometric properties of rubber compounds from their formulation is presented. Because of the complexity and non-linearity of mixing processes, an exact mathematical treatment of the problem is extremely difficult, or even impossible. The use of artificial neural networks (ANNs) might be very useful to analyze these processes, since they have the ability to map nonlinear relationships without prior information about process or system models. In this work a three-layer ANN is used and the optimum parameters are determined. The results are compared with theoretical and experimental published data. The dependence of the rheometric properties as a function of compound components is also analyzed. Finally, the sensibility matrix concept is introduced. The sensibility matrix allows us to calculate the minimum expected variability, for a given compound, due to the weight tolerances of its components.

scholarly journals Mixing processes and exchanges in the tropical and the subtropical UT/LS

2008 ◽  
Vol 8 (3) ◽  
pp. 10627-10664
Author(s):  
R. James ◽  
B. Legras
Keyword(s):  
Mixing Time ◽  
Chemical Compositions ◽  
Mixing Processes ◽  
Mixing Properties ◽  
Back Trajectories ◽  
Air Masses ◽  
Upper Troposphere ◽  
The Tropics

Abstract. Both in situ measurements and satellite observations indicate evidence of mixing in the upper troposphere (UT) and the lower-stratosphere (LS). In this study, the measurements performed during the Pre-AVE and Costa-Rica AVE campaigns are analysed with diffusive back-trajectories to assess mixing properties in the tropical and the subtropical UT/LS. A description of cross-tropopause pathways and mixing time scales is provided. In the subtropics, Troposphere-Stratosphere mixing processes are found to differ in the vicinity of the tropopause and at higher altitudes. Below 350 K, the mixing line observed during Pre-AVE is shown to result from fast and local cross-tropopause irreversible exchange, involving two initially distant air masses with distinct chemical compositions. For measurements located above 350 K, mixing of the tropospheric air in the subtropical stratosphere occurs over a period of a month, the origins of the tropospheric source being localised in the tropical UT and the tropical boundary layer. In the tropics, quantitative reconstructions of CO and O3 profiles above 360 K are obtained for one month back-trajectories calculations, pointing out that long term mixing is essential to determine the chemical composition in the tropical ascent. In particular, the existence of two-way meridional irreversible exchanges between 360 and 450 K is found to export tropical air in the subtropical stratosphere and to entrain old stratospheric air in the tropical ascent. Calculations of the Lagrangian mean age of air is shown to be in qualitative agreement with the CO2 observations and diabatic calculations.

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.

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