Atmospheric Mercury Concentrations observed at ground-based monitoring sites globally distributed in the framework of the GMOS network

Atmospheric mercury concentrations observed at ground-based monitoring sites globally distributed in the framework of the GMOS network

Atmospheric Chemistry and Physics ◽

10.5194/acp-16-11915-2016 ◽

2016 ◽

Vol 16 (18) ◽

pp. 11915-11935 ◽

Cited By ~ 86

Author(s):

Francesca Sprovieri ◽

Nicola Pirrone ◽

Mariantonia Bencardino ◽

Francesco D'Amore ◽

Francesco Carbone ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Ad Hoc ◽

Temporal Trends ◽

Global Scale ◽

Atmospheric Mercury ◽

Global Network ◽

Observation System ◽

Large Network ◽

Deposition Processes ◽

The Impact

Abstract. Long-term monitoring of data of ambient mercury (Hg) on a global scale to assess its emission, transport, atmospheric chemistry, and deposition processes is vital to understanding the impact of Hg pollution on the environment. The Global Mercury Observation System (GMOS) project was funded by the European Commission (http://www.gmos.eu) and started in November 2010 with the overall goal to develop a coordinated global observing system to monitor Hg on a global scale, including a large network of ground-based monitoring stations, ad hoc periodic oceanographic cruises and measurement flights in the lower and upper troposphere as well as in the lower stratosphere. To date, more than 40 ground-based monitoring sites constitute the global network covering many regions where little to no observational data were available before GMOS. This work presents atmospheric Hg concentrations recorded worldwide in the framework of the GMOS project (2010–2015), analyzing Hg measurement results in terms of temporal trends, seasonality and comparability within the network. Major findings highlighted in this paper include a clear gradient of Hg concentrations between the Northern and Southern hemispheres, confirming that the gradient observed is mostly driven by local and regional sources, which can be anthropogenic, natural or a combination of both.

Impact of transport model errors on the global and regional methane emissions estimated by inverse modelling

Atmospheric Chemistry and Physics ◽

10.5194/acp-13-9917-2013 ◽

2013 ◽

Vol 13 (19) ◽

pp. 9917-9937 ◽

Cited By ~ 45

Author(s):

R. Locatelli ◽

P. Bousquet ◽

F. Chevallier ◽

A. Fortems-Cheney ◽

S. Szopa ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Transport Model ◽

Initial Conditions ◽

Spatial Scales ◽

Global Scale ◽

Methane Emissions ◽

Inverse Modelling ◽

Model Errors ◽

Inverse Systems ◽

The Impact

Abstract. A modelling experiment has been conceived to assess the impact of transport model errors on methane emissions estimated in an atmospheric inversion system. Synthetic methane observations, obtained from 10 different model outputs from the international TransCom-CH4 model inter-comparison exercise, are combined with a prior scenario of methane emissions and sinks, and integrated into the three-component PYVAR-LMDZ-SACS (PYthon VARiational-Laboratoire de Météorologie Dynamique model with Zooming capability-Simplified Atmospheric Chemistry System) inversion system to produce 10 different methane emission estimates at the global scale for the year 2005. The same methane sinks, emissions and initial conditions have been applied to produce the 10 synthetic observation datasets. The same inversion set-up (statistical errors, prior emissions, inverse procedure) is then applied to derive flux estimates by inverse modelling. Consequently, only differences in the modelling of atmospheric transport may cause differences in the estimated fluxes. In our framework, we show that transport model errors lead to a discrepancy of 27 Tg yr−1 at the global scale, representing 5% of total methane emissions. At continental and annual scales, transport model errors are proportionally larger than at the global scale, with errors ranging from 36 Tg yr−1 in North America to 7 Tg yr−1 in Boreal Eurasia (from 23 to 48%, respectively). At the model grid-scale, the spread of inverse estimates can reach 150% of the prior flux. Therefore, transport model errors contribute significantly to overall uncertainties in emission estimates by inverse modelling, especially when small spatial scales are examined. Sensitivity tests have been carried out to estimate the impact of the measurement network and the advantage of higher horizontal resolution in transport models. The large differences found between methane flux estimates inferred in these different configurations highly question the consistency of transport model errors in current inverse systems. Future inversions should include more accurately prescribed observation covariances matrices in order to limit the impact of transport model errors on estimated methane fluxes.

Four years of atmospheric mercury records in Northwestern Patagonia (Argentina): potential sources, concentration patterns and influence of environmental variables observed at the GMOS EMMA station

10.5194/acp-2016-1076 ◽

2017 ◽

Cited By ~ 2

Author(s):

Maria C. Diéguez ◽

Patricia E. Garcia ◽

Mariantonia Bencardino ◽

Francesco D'Amore ◽

Jessica Castagna ◽

...

Keyword(s):

Global Scale ◽

Atmospheric Mercury ◽

Observation System ◽

Monitoring Site ◽

Night Time ◽

Mean Values ◽

The Andes ◽

Southern Volcanic Zone ◽

Andes Cordillera ◽

Active Volcanoes

Abstract. The Global Mercury Observation System (GMOS) project, has developed a global-scale network of ground-based atmospheric monitoring sites, expanding the coverage of atmospheric mercury (Hg) measurements worldwide and improving the understanding of global atmospheric Hg transport and deposition, particularly in regions of the South Hemisphere where atmospheric Hg observational data is limited. This work provides the first continuous records of gaseous elemental Hg (GEM) concentrations observed from October 2012 to May 2016 in Northwestern Patagonia (Argentina) at the GMOS EMMA monitoring station (41°7'43.82" S, 71°25'11.89" W, 803 m a.s.l). The monitoring site is located inside Nahuel Huapi National Park, a natural reserve in the Lake District of Andean Patagonia. The area is within the Southern Volcanic Zone, influenced by several active volcanoes aligned in the Andes cordillera. During the studied period, GEM concentrations ranged between 0.23 and 1.43 ng m−3, with an annual mean of 0.9 ± 0.15 ng m−3. GEM records at EMMA station resemble background concentrations measured in Antarctica and other remote locations of the Southern Hemisphere. GEM concentrations showed seasonal variation with mean values higher during spring (0.93 ± 0.13 ng m−3) and winter (0.92 ± 0.10 ng m−3) followed by summer (0.86 ± 0.15 ng m−3) and at last by autumn (0.81 ± 0.15 ng m−3). Further, a clear daily pattern was observed, with higher GEM levels during day-time than at night-time across all seasons. Multivariate analyses showed that GEM levels are chiefly determined by meteorological parameters, and, in particular by the westerly winds which represented the most influential variable on GEM records. In order to investigate the potential impact of natural and/or anthropogenic emission sources as well as the role played by the long-range transport on GEM levels, analyses of HYSPLIT backward trajectories (BWT) were carried out for different periods characterized by low and high GEM concentrations. The BWT analysis highlighted the influence of clean oceanic air masses and also of the local and regional active volcanoes in the Andes cordillera.

Odds and ends of atmospheric mercury in Europe and over northern Atlantic Ocean: Temporal trends of 25 years of measurements

10.5194/acp-2021-753 ◽

2021 ◽

Author(s):

Danilo Custódio ◽

Franz Slemr ◽

Katrine Aspmo Pfaffhuber ◽

T. Gerard Spain ◽

Fidel F. Pankratov ◽

...

Keyword(s):

Temporal Trends ◽

Mass Function ◽

Global Scale ◽

Atmospheric Mercury ◽

Anthropogenic Sources ◽

Back Trajectories ◽

Air Masses ◽

Minamata Convention On Mercury ◽

Northern Atlantic ◽

Concentration Weighted Trajectories

Abstract. The Global Monitoring Plan of the Minamata Convention on Mercury was established to generate long-term data necessary for evaluating the effectiveness of regulatory measures at a global scale. After 25 years monitoring (since 1995), Mace Head is one of the atmospheric monitoring stations with the longest mercury record, and has produced sufficient data for the analysis of temporal trends of Total Gaseous Mercury (TGM) in Europe and the Northern Atlantic. Using concentration-weighted trajectories for atmospheric mercury measured at Mace Head as well as other five locations in Europe, Amderma, Andøya, Villum, Waldhof and Zeppelin we identify the regional probabilistic source contribution factor and its changes for the period of 1996 to 2019. Temporal trends indicate that concentrations of mercury in the atmosphere in Europe and the Northern Atlantic have declined significantly over the past 25 years, at a non-monotonic rate averaging of 0.03 ng m-3 year-1. Concentrations of TGM at remote marine sites were shown to be affected by continental long-range transport, and evaluation of reanalysis back-trajectories display a significant decrease of TGM in continental air masses from Europe in the last two decades. In addition, using the relationship between mercury and other atmospheric trace gases that could serve as a source signature, we perform factorization regression analysis, based on positive rotatable factorization of non-singular matrix to solve probabilistic mass function. We reconstructed atmospheric mercury concentration and accessed the contribution of the major natural and anthropogenic sources. The positive matrix factorization (PMF) reveals that the downward trend is mainly associated with a factor with a high load of long-lived anthropogenic species.

Modeling the impact of sub-grid scale emission variability on upper-air concentration

Atmospheric Chemistry and Physics ◽

10.5194/acp-8-141-2008 ◽

2008 ◽

Vol 8 (2) ◽

pp. 141-158 ◽

Cited By ~ 15

Author(s):

S. Galmarini ◽

J.-F. Vinuesa ◽

A. Martilli

Keyword(s):

Ad Hoc ◽

Mesoscale Model ◽

Global Scale ◽

Average Concentration ◽

Air Concentration ◽

Concentration Variance ◽

Eddy Simulation ◽

Subgrid Model ◽

Error Bar ◽

The Impact

Abstract. The long standing issue of sub-grid emission heterogeneity and its influence to upper air concentration is addressed here and a subgrid model proposed. The founding concept of the approach is the assumption that average emission act as source terms of average concentration, emission fluctuations are source for the concentration variance. The model is based on the derivation of the sub-grid contribution of emission and the use of the concentration variance equation to transport it in the atmospheric boundary layer. The model has been implemented in an existing mesoscale model and the results compared with Large-Eddy Simulation data for ad-hoc simulation devised to test specifically the parametrization. The results show an excellent agreement of the models. For the first time a time evolving error bar reproducing the sub-grid scale heterogeneity of the emissions and the way in which it affects the concentration has been shown. The concentration variance is presented as an extra attribute to better define the mean concentrations in a Reynolds-average model. The model has applications from meso to global scale and that go beyond air quality.

The impact of ice uptake of nitric acid on atmospheric chemistry

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-225-2006 ◽

2006 ◽

Vol 6 (1) ◽

pp. 225-235 ◽

Cited By ~ 24

Author(s):

R. von Kuhlmann ◽

M. G. Lawrence

Keyword(s):

Atmospheric Chemistry ◽

Transport Model ◽

Global Scale ◽

Large Set ◽

Model Match ◽

Uptake Process ◽

Significant Uptake ◽

The Impact ◽

Experimental And Theoretical Studies

Abstract. The potential impact of the uptake of HNO3 on ice on the distribution of NOy species, ozone and OH has been assessed using the global scale chemistry-transport model MATCH-MPIC. Assuming equilibrium uptake according to dissociative Langmuir theory results in significant reductions of gas phase HNO3. Comparison to a large set of observations provides support that significant uptake of HNO3 on ice is occurring, but the degree of the uptake cannot be inferred from this comparison alone. Sensitivity simulations show that the uncertainties in the total amount of ice formation in the atmosphere and the actual expression of the settling velocity of ice particles only result in small changes in our results. The largest uncertainty is likely to be linked to the actual theory describing the uptake process and the value of the initial uptake coefficient. The inclusion of non-methane hydrocarbon chemistry partially compensates for the absence of HNO3 uptake on ice when this is neglected in the model. The calculated overall effect on upper tropospheric ozone concentrations and the tropospheric methane lifetime are moderate to low. These results support a shift in the motivation for future experimental and theoretical studies of HNO3-ice interaction towards the role of HNO3 in hydrometeor surface physics.

Conflicts in Routing and UAV Autonomy

Australian Journal of Telecommunications and the Digital Economy ◽

10.18080/jtde.v6n4.169 ◽

2018 ◽

Vol 6 (4) ◽

pp. 96-108 ◽

Cited By ~ 1

Author(s):

Ogbonnaya Anicho ◽

Philip B Charlesworth ◽

Gurvinder S Baicher ◽

Atulya Nagar

Keyword(s):

Network Architecture ◽

Ad Hoc ◽

Area Coverage ◽

Global Network ◽

Network Efficiency ◽

Aerial Vehicle ◽

Routing Techniques ◽

Stability Issues ◽

Link Availability ◽

The Impact

Routing is very fundamental to the implementation of any networking or communications infrastructure. This paper, therefore, examines the conflicts and relevant considerations for implementing autonomous or self-organising unmanned aerial vehicles (UAVs) for communications area coverage, with particular emphasis on the impact of aerial vehicle autonomy algorithms on routing techniques for such networks. UAV networks can be deployed either as ad-hoc or infrastructure-based solutions. The mobility of UAVs introduces periodic topology changes, impacting link availability and routing paths. This work examines the implications of autonomous coordination of multiple UAVs on routing techniques and network architecture stability. The paper proposes a solution where routing techniques and UAV autonomy algorithms are integrated for improved global network efficiency for both ad-hoc and infrastructure-based scenarios. Integrating UAV autonomy algorithms with routing schemes may be an efficient method to mitigate link/topology stability issues and improve inter-UAV communication and network throughput, a key requirement for UAV networks. The implementation of inter-UAV links using optical, microwave or mmWave transmission is examined in the context of this work. The proposed integration may be crucial for communications coverage, where UAVs provide communications area coverage of a community of mobile or fixed users in either ad-hoc or infrastructure-based modes.

Impact of atomic chlorine on the modelling of total methane and its <sup>13</sup>C : <sup>12</sup>C isotopic ratio at global scale

10.5194/acp-2019-925 ◽

2019 ◽

Cited By ~ 2

Author(s):

Joël Thanwerdas ◽

Marielle Saunois ◽

Antoine Berchet ◽

Isabelle Pison ◽

Didier Hauglustaine ◽

...

Keyword(s):

Atmospheric Chemistry ◽

Transport Model ◽

Isotopic Ratio ◽

Circulation Model ◽

Global Scale ◽

Major Influence ◽

Atmospheric Methane ◽

Global Circulation Model ◽

Substantial Impact ◽

The Impact

Abstract. Methane (CH4) is the second strongest anthropogenic greenhouse gas after carbon dioxide (CO2) and is responsible for about 20 % of the warming induced by long-lived greenhouse gases since pre-industrial times. Oxidation by the hydroxyl radical (OH) is the dominant atmospheric sink for methane, contributing to approximately 90 % of the total methane loss. Chemical losses by reaction with atomic oxygen (O1D) and chlorine radicals (Cl) in the stratosphere are other sinks, contributing about 3 % to the total methane destruction. Moreover, the reaction with Cl is very fractionating, thus it has a much larger impact on δ13C-CH4 than the reaction with OH. In this paper, we assess the impact of atomic Cl on atmospheric methane mixing ratios, methane atmospheric loss and atmospheric δ13C-CH4. The offline version of the Global Circulation Model (GCM) LMDz, coupled to a chemistry module including the major methane chemical reactions, is run to simulate CH4 concentrations and δ13C-CH4 at the global scale. Atmospheric methane sink by Cl atoms in the stratosphere is found to be 7.32 ± 0.16 Tg/yr. Methane observations from vertical profiles obtained using AirCore samplers above 11 different locations across the globe and balloon measurements of δ13C-CH4 and methane are used to assess the impact of the Cl sink in the chemistry transport model. Above 10 km, the presence of Cl in the model is found to have only a small impact on the vertical profile of total methane but a major influence on δ13C-CH4 values, significantly improving the agreement between simulations and available observations. Stratospheric Cl is also found to have a substantial impact on surface δ13C-CH4 values, leading to a difference of +0.27 ‰ (less negative values) after a 19-year run. As a result, this study suggests that the Cl sink needs to be properly taken into account (magnitude and trends) in order to better understand trends in the atmospheric δ13C-CH4 signal when using atmospheric chemistry transport models for forward or inverse calculations.

Conflicts in Routing and UAV Autonomy

Australian Journal of Telecommunications and the Digital Economy ◽

10.18080/ajtde.v6n4.169 ◽

2018 ◽

Vol 6 (4) ◽

pp. 96-108

Author(s):

Ogbonnaya Anicho ◽

Philip B Charlesworth ◽

Gurvinder S Baicher ◽

Atulya Nagar

Keyword(s):

Network Architecture ◽

Ad Hoc ◽

Area Coverage ◽

Global Network ◽

Network Efficiency ◽

Aerial Vehicle ◽

Routing Techniques ◽

Stability Issues ◽

Link Availability ◽

The Impact

Routing is very fundamental to the implementation of any networking or communications infrastructure. This paper, therefore, examines the conflicts and relevant considerations for implementing autonomous or self-organising unmanned aerial vehicles (UAVs) for communications area coverage, with particular emphasis on the impact of aerial vehicle autonomy algorithms on routing techniques for such networks. UAV networks can be deployed either as ad-hoc or infrastructure-based solutions. The mobility of UAVs introduces periodic topology changes, impacting link availability and routing paths. This work examines the implications of autonomous coordination of multiple UAVs on routing techniques and network architecture stability. The paper proposes a solution where routing techniques and UAV autonomy algorithms are integrated for improved global network efficiency for both ad-hoc and infrastructure-based scenarios. Integrating UAV autonomy algorithms with routing schemes may be an efficient method to mitigate link/topology stability issues and improve inter-UAV communication and network throughput, a key requirement for UAV networks. The implementation of inter-UAV links using optical, microwave or mmWave transmission is examined in the context of this work. The proposed integration may be crucial for communications coverage, where UAVs provide communications area coverage of a community of mobile or fixed users in either ad-hoc or infrastructure-based modes.

The earth orbiting space debris

Serbian Astronomical Journal ◽

10.2298/saj0570001r ◽

2005 ◽

pp. 1-12 ◽

Cited By ~ 16

Author(s):

A. Rossi

Keyword(s):

Space Debris ◽

Ad Hoc ◽

High Energy ◽

Long Term Evolution ◽

Asteroid Belt ◽

Large Network ◽

The Earth ◽

Term Evolution ◽

The Impact

The space debris population is similar to the asteroid belt, since it is subject to a process of high-velocity mutual collisions that affects the long-term evolution of its size distribution. Presently, more than 10 000 artificial debris particles with diameters larger than 10 cm (and more than 300 000 with diameters larger than 1 cm) are orbiting the Earth, and are monitored and studied by a large network of sensors around the Earth. Many objects of different kind compose the space debris population, produced by different source mechanisms ranging from high energy fragmentation of large spacecraft to slow diffusion of liquid metal. The impact against a space debris is a serious risk that every spacecraft must face now and it can be evaluated with ad-hoc algorithms. The long term evolution of the whole debris population is studied with computer models allowing the simulation of all the known source and sink mechanisms. One of these codes is described in this paper and the evolution of the debris environment over the next 100 years, under different traffic scenarios, is shown, pointing out the possible measures to mitigate the growth of the orbital debris population. .