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Christophe Leroy-Dos Santos, Mathieu Casado, Frédéric Prié, Olivier Jossoud, Erik Kerstel, Morgane Farradèche, Samir Kassi, Elise Fourré, Amaëlle Landais. (2021). A dedicated robust instrument for water vapor generation at low humidity for use with a laser water isotope analyzer in cold and dry polar regions (Vol. 14). Bachelor's thesis, , .
Abstract: Obtaining Precise Continuous Measurements Of Water Vapor Isotopic Composition In Dry Places (Polar Or High-altitude Regions) Is An Important Challenge. The Current Limitation Is The Strong Influence Of Humidity On The Measured Water Isotopic Composition By Laser Spectroscopy Instruments For Low Humidity Levels (Below 3000 Ppmv). This Problem Is Addressed By Determining The Relationships Between Humidity And Measured δ18o And δD Of Known Water Standards. Here, We Present The Development Of A Robust Field Instrument Able To Generate Water Vapor, Down To 70 Ppmv, At Very Stable Humidity Levels (Average 1σ Lower Than 10 Ppmv). This Instrument, Operated By A Raspberry Interface, Can Be Coupled To A Commercial Laser Spectroscopy Instrument. We Checked The Stability Of The System As Well As Its Accuracy When Expressing The Measured Isotopic Composition Of Water Vapor On The Vsmow–slap (Vienna Standard Mean Ocean Water – Standard Light Antarctic Precipitation) Scale. It Proved To Be Highly Stable During Autonomous Operation Over More Than 1 Year At The East Antarctic Concordia And Dumont D'urville Stations.
Programme: 1110,1169,1205
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Albane Barbero, Camille Blouzon, Joël Savarino, Nicolas Caillon, Aurélien Dommergue, Roberto Grilli. (2020). A compact incoherent broadband cavity-enhanced absorption spectrometer for trace detection of nitrogen oxides, iodine oxide and glyoxal at levels below parts per billion for field applications (Vol. 13). Bachelor's thesis, , .
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Anne Boynard, Daniel Hurtmans, Katerina Garane, Florence Goutail, Juliette Hadji-Lazaro, Maria Elissavet Koukouli, Catherine Wespes, Corinne Vigouroux, Arno Keppens, Jean-Pierre Pommereau, Andrea Pazmino, Dimitris Balis, Diego Loyola, Pieter Valks, Ralf Sussmann, Dan Smale, Pierre-François Coheur, Cathy Clerbaux. (2018). Validation of the IASI FORLI/EUMETSAT ozone products using satellite (GOME-2), ground-based (Brewer–Dobson, SAOZ, FTIR) and ozonesonde measurements (Vol. 11). Bachelor's thesis, , .
Abstract: This Paper Assesses The Quality Of Iasi (Infrared Atmospheric Sounding Interferometer)/metop-a (Iasi-a) And Iasi/metop-b (Iasi-b) Ozone (O3) Products (Total And Partial O3 Columns) Retrieved With The Fast Optimal Retrievals On Layers For Iasi Ozone (Forli-o3; V20151001) Software For 9 Years (2008–july 2017) Through An Extensive Intercomparison And Validation Exercise Using Independent Observations (Satellite, Ground-based And Ozonesonde). Compared With The Previous Version Of Forli-o3 (V20140922), Several Improvements Have Been Introduced In Forli-o3 V20151001, Including Absorbance Look-up Tables Recalculated To Cover A Larger Spectral Range, With Additional Numerical Corrections. This Leads To A Change Of ∼4% In The Total Ozone Column (Toc) Product, Which Is Mainly Associated With A Decrease In The Retrieved O3 Concentration In The Middle Stratosphere (Above 30hpa/25km). Iasi-a And Iasi-b Tocs Are Consistent, With A Global Mean Difference Of Less Than 0.3% For Both Daytime And Nighttime Measurements; Iasi-a Is Slightly Higher Than Iasi-b. A Global Difference Of Less Than 2.4% Is Found For The Tropospheric (Tropo) O3 Column Product (Iasi-a Is Lower Than Iasi-b), Which Is Partly Due To A Temporary Issue Related To The Iasi-a Viewing Angle In 2015. Our Validation Shows That Iasi-a And Iasi-b Tocs Are Consistent With Gome-2 (Global Ozone Monitoring Experiment-2), Dobson, Brewer, Saoz (Système D'analyse Par Observation Zénithale) And Ftir (Fourier Transform Infrared) Tocs, With Global Mean Differences In The Range Of 0.1%–2% Depending On The Instruments Compared. The Worst Agreement With Uv–vis Retrieved Toc (Satellite And Ground) Is Found At The Southern High Latitudes. The Iasi-a And Ground-based Toc Comparison For The Period From 2008 To July 2017 Shows The Long-term Stability Of Iasi-a, With Insignificant Or Small Negative Drifts Of 1%–3%decade−1. The Comparison Results Of Iasi-a And Iasi-b Against Smoothed Ftir And Ozonesonde Partial O3 Columns Vary With Altitude And Latitude, With The Maximum Standard Deviation Being Seen For The 300–150hpa Column (20%–40%) Due To Strong Ozone Variability And Large Total Retrievals Errors. Compared With Ozonesonde Data, The Iasi-a And Iasi-b O3 Tropo Column (Defined As The Column Between The Surface And 300hpa) Is Positively Biased In The High Latitudes (4%–5%) And Negatively Biased In The Midlatitudes And Tropics (11%–13% And 16%–19%, Respectively). The Iasi-a-to-ozonesonde Tropo Comparison For The Period From 2008 To 2016 Shows A Significant Negative Drift In The Northern Hemisphere Of -8.6±3.4%decade−1, Which Is Also Found In The Iasi-a-to-ftir Tropo Comparison. When Considering The Period From 2011 To 2016, The Drift Value For The Tropo Column Decreases And Becomes Statistically Insignificant. The Observed Negative Drifts Of The Iasi-a Tropo O3 Product (8%–16%decade−1) Over The 2008–2017 Period Might Be Taken Into Consideration When Deriving Trends From This Product And This Time Period.
Programme: 209
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Abdelhadi El Yazidi, Michel Ramonet, Philippe Ciais, Gregoire Broquet, Isabelle Pison, Amara Abbaris, Dominik Brunner, Sebastien Conil, Marc Delmotte, Francois Gheusi, Frederic Guerin, Lynn Hazan, Nesrine Kachroudi, Giorgos Kouvarakis, Nikolaos Mihalopoulos, Leonard Rivier, Dominique Serça. (2018). Identification of spikes associated with local sources in continuous time series of atmospheric CO, CO2 and CH4 (Vol. 11). Bachelor's thesis, , .
Abstract: This Study Deals With The Problem Of Identifying Atmospheric Data Influenced By Local Emissions That Can Result In Spikes In Time Series Of Greenhouse Gases And Long-lived Tracer Measurements. We Considered Three Spike Detection Methods Known As Coefficient Of Variation (Cov), Robust Extraction Of Baseline Signal (Rebs) And Standard Deviation Of The Background (Sd) To Detect And Filter Positive Spikes In Continuous Greenhouse Gas Time Series From Four Monitoring Stations Representative Of The European Icos (Integrated Carbon Observation System) Research Infrastructure Network. The Results Of The Different Methods Are Compared To Each Other And Against A Manual Detection Performed By Station Managers. Four Stations Were Selected As Test Cases To Apply The Spike Detection Methods: A Continental Rural Tower Of 100m Height In Eastern France (Ope), A High-mountain Observatory In The South-west Of France (Pdm), A Regional Marine Background Site In Crete (Fkl) And A Marine Clean-air Background Site In The Southern Hemisphere On Amsterdam Island (Ams). This Selection Allows Us To Address Spike Detection Problems In Time Series With Different Variability. Two Years Of Continuous Measurements Of Co2, Ch4 And Co Were Analysed. All Methods Were Found To Be Able To Detect Short-term Spikes (Lasting From A Few Seconds To A Few Minutes) In The Time Series. Analysis Of The Results Of Each Method Leads Us To Exclude The Cov Method Due To The Requirement To Arbitrarily Specify An A Priori Percentage Of Rejected Data In The Time Series, Which May Over- Or Underestimate The Actual Number Of Spikes. The Two Other Methods Freely Determine The Number Of Spikes For A Given Set Of Parameters, And The Values Of These Parameters Were Calibrated To Provide The Best Match With Spikes Known To Reflect Local Emissions Episodes That Are Well Documented By The Station Managers. More Than 96% Of The Spikes Manually Identified By Station Managers Were Successfully Detected Both In The Sd And The Rebs Methods After The Best Adjustment Of Parameter Values. At Pdm, Measurements Made By Two Analyzers Located 200m From Each Other Allow Us To Confirm That The Ch4 Spikes Identified In One Of The Time Series But Not In The Other Correspond To A Local Source From A Sewage Treatment Facility In One Of The Observatory Buildings. From This Experiment, We Also Found That The Rebs Method Underestimates The Number Of Positive Anomalies In The Ch4 Data Caused By Local Sewage Emissions. As A Conclusion, We Recommend The Use Of The Sd Method, Which Also Appears To Be The Easiest One To Implement In Automatic Data Processing, Used For The Operational Filtering Of Spikes In Greenhouse Gases Time Series At Global And Regional Monitoring Stations Of Networks Like That Of The Icos Atmosphere Network.
Programme: 416
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Winton V.H.L., Ming A., Caillon N., Hauge L. Jones A.E., Savarino J., Yang X., Frey M.M. (2020). Deposition, recycling, and archival of nitrate stable isotopes between the air–snow interface: comparison between Dronning Maud Land and Dome C, Antarctica (Vol. 20). Bachelor's thesis, , .
Abstract: The nitrogen stable isotopic composition in nitrate (δ15N-NO−3) measured in ice cores from low-snow-accumulation regions in East Antarctica has the potential to provide constraints on past ultraviolet (UV) radiation and thereby total column ozone (TCO) due to the sensitivity of nitrate (NO−3) photolysis to UV radiation. However, understanding the transfer of reactive nitrogen at the air–snow interface in polar regions is paramount for the interpretation of ice core records of δ15N-NO−3 and NO−3 mass concentrations. As NO−3 undergoes a number of post-depositional processes before it is archived in ice cores, site-specific observations of δ15N-NO−3 and air–snow transfer modelling are necessary to understand and quantify the complex photochemical processes at play. As part of the Isotopic Constraints on Past Ozone Layer Thickness in Polar Ice (ISOL-ICE) project, we report new measurements of NO−3 mass concentration and δ15N-NO−3 in the atmosphere, skin layer (operationally defined as the top 5 mm of the snowpack), and snow pit depth profiles at Kohnen Station, Dronning Maud Land (DML), Antarctica. We compare the results to previous studies and new data, presented here, from Dome C on the East Antarctic Plateau. Additionally, we apply the conceptual 1D model of TRansfer of Atmospheric Nitrate Stable Isotopes To the Snow (TRANSITS) to assess the impact of NO−3 recycling on δ15N-NO−3 and NO−3 mass concentrations archived in snow and firn. We find clear evidence of NO−3 photolysis at DML and confirmation of previous theoretical, field, and laboratory studies that UV photolysis is driving NO−3 recycling and redistribution at DML. Firstly, strong denitrification of the snowpack is observed through the δ15N-NO−3 signature, which evolves from the enriched snowpack (−3 ‰ to 100 ‰), to the skin layer (−20 ‰ to 3 ‰), to the depleted atmosphere (−50 ‰ to −20 ‰), corresponding to mass loss of NO−3 from the snowpack. Based on the TRANSITS model, we find that NO−3 is recycled two times, on average, before it is archived in the snowpack below 15 cm and within 0.75 years (i.e. below the photic zone). Mean annual archived δ15N-NO−3 and NO−3 mass concentration values are 50 ‰ and 60 ng g−1, respectively, at the DML site. We report an e-folding depth (light attenuation) of 2–5 cm for the DML site, which is considerably lower than Dome C. A reduced photolytic loss of NO−3 at DML results in less enrichment of δ15N-NO−3 than at Dome C mainly due to the shallower e-folding depth but also due to the higher snow accumulation rate based on TRANSITS-modelled sensitivities. Even at a relatively low snow accumulation rate of 6 cm yr−1 (water equivalent; w.e.), the snow accumulation rate at DML is great enough to preserve the seasonal cycle of NO−3 mass concentration and δ15N-NO−3, in contrast to Dome C where the depth profiles are smoothed due to longer exposure of surface snow layers to incoming UV radiation before burial. TRANSITS sensitivity analysis of δ15N-NO−3 at DML highlights that the dominant factors controlling the archived δ15N-NO−3 signature are the e-folding depth and snow accumulation rate, with a smaller role from changes in the snowfall timing and TCO. Mean TRANSITS model sensitivities of archived δ15N-NO−3 at the DML site are 100 ‰ for an e-folding depth change of 8 cm, 110 ‰ for an annual snow accumulation rate change of 8.5 cm yr−1 w.e., 10 ‰ for a change in the dominant snow deposition season between winter and summer, and 10 ‰ for a TCO change of 100 DU (Dobson units). Here we set the framework for the interpretation of a 1000-year ice core record of δ15N-NO−3 from DML. Ice core δ15N-NO−3 records at DML will be less sensitive to changes in UV than at Dome C; however the higher snow accumulation rate and more accurate dating at DML allows for higher-resolution δ15N-NO−3 records.
Programme: 1177
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Rolf Weller, Michel Legrand, Susanne Preunkert. (2018). Size distribution and ionic composition of marine summer aerosol at the continental Antarctic site Kohnen (Vol. 18). Bachelor's thesis, , .
Abstract: We Measured Aerosol Size Distributions And Conducted Bulk And Size-segregated Aerosol Sampling During Two Summer Campaigns In January 2015 And January 2016 At The Continental Antarctic Station Kohnen (Dronning Maud Land). Physical And Chemical Aerosol Properties Differ Conspicuously During The Episodic Impact Of A Distinctive Low-pressure System In 2015 (Lps15) Compared To The Prevailing Clear Sky Conditions. The Approximately 3-day Lps15 Located In The Eastern Weddell Sea Was Associated With The Following: Marine Boundary Layer Air Mass Intrusion; Enhanced Condensation Particle Concentrations (1400±700cm−3 Compared To 250±120cm−3 Under Clear Sky Conditions; Mean±sd); The Occurrence Of A New Particle Formation Event Exhibiting A Continuous Growth Of Particle Diameters (Dp) From 12 To 43nm Over 44h (Growth Rate 0.6nmh−1); Peaking Methane Sulfonate (Ms−), Non-sea-salt Sulfate (Nss–so42-), And Na+ Concentrations (190ngm−3ms−, 137ngm−3 Nss–so42-, And 53ngm−3na+ Compared To 24±15, 107±20, And 4.1±2.2ngm−3, Respectively, During Clear Sky Conditions); And Finally An Increased Ms−∕nss–so42- Mass Ratio βMs Of 0.4 Up To 2.3 (0.21±0.1 Under Clear Sky Conditions) Comparable To Typical Values Found At Coastal Antarctic Sites. Throughout The Observation Period A Larger Part Of Ms− Could Be Found In Super-micron Aerosol Compared To Nss–so42-, I.e., (10±2) % By Mass Compared To (3.2±2) %, Respectively. On The Whole, Under Clear Sky Conditions Aged Aerosol Characterized By Usually Mono-modal Size Distributions Around Dp=60nm Was Observed. Although Our Observations Indicate That The Sporadic Impacts Of Coastal Cyclones Were Associated With Enhanced Marine Aerosol Entry, Aerosol Deposition On-site During Austral Summer Should Be Largely Dominated By Typical Steady Clear Sky Conditions.
Programme: 414
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Michel Legrand, Susanne Preunkert, Rolf Weller, Lars Zipf, Christoph Elsässer, Silke Merchel, Georg Rugel, Dietmar Wagenbach. (2017). Year-round record of bulk and size-segregated aerosol composition in central Antarctica (Concordia site) – Part 2: Biogenic sulfur (sulfate and methanesulfonate) aerosol (Vol. 17). Bachelor's thesis, , .
Abstract: Multiple year-round (2006–2015) records of the bulk and size-segregated composition of aerosol were obtained at the inland site of Concordia located in East Antarctica. The well-marked maximum of non-sea-salt sulfate (nssSO4) in January (100 ± 28 ng m−3 versus 4.4 ± 2.3 ng m−3 in July) is consistent with observations made at the coast (280 ± 78 ng m−3 in January versus 16 ± 9 ng m−3 in July at Dumont d'Urville, for instance). In contrast, the well-marked maximum of MSA at the coast in January (60 ± 23 ng m−3 at Dumont d'Urville) is not observed at Concordia (5.2 ± 2.0 ng m−3 in January). Instead, the MSA level at Concordia peaks in October (5.6 ± 1.9 ng m−3) and March (14.9 ± 5.7 ng m−3). As a result, a surprisingly low MSA-to-nssSO4 ratio (RMSA) is observed at Concordia in mid-summer (0.05 ± 0.02 in January versus 0.25 ± 0.09 in March). We find that the low value of RMSA in mid-summer at Concordia is mainly driven by a drop of MSA levels that takes place in submicron aerosol (0.3 µm diameter). The drop of MSA coincides with periods of high photochemical activity as indicated by high ozone levels, strongly suggesting the occurrence of an efficient chemical destruction of MSA over the Antarctic plateau in mid-summer. The relationship between MSA and nssSO4 levels is examined separately for each season and indicates that concentration of non-biogenic sulfate over the Antarctic plateau does not exceed 1 ng m−3 in fall and winter and remains close to 5 ng m−3 in spring. This weak non-biogenic sulfate level is discussed in the light of radionuclides (210Pb, 10Be, and 7Be) also measured on bulk aerosol samples collected at Concordia. The findings highlight the complexity in using MSA in deep ice cores extracted from inland Antarctica as a proxy of past dimethyl sulfide emissions from the Southern Ocean.
Programme: 414
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Casado, M. A. Landais, V. Masson-Delmotte, C. Genthon, E. Kerstel, S. Kassi, L. Arnaud, G. Picard, F. Prie, O. Cattani, H.-C. Steen-Larsen, E. Vignon, and P. Cermak. (2016). Continuous measurements of isotopic composition of water vapour on the East Antarctic Plateau (Vol. 16). Bachelor's thesis, , .
Abstract: Water stable isotopes in central Antarctic ice cores are critical to quantify past temperature changes. Accurate temperature reconstructions require one to understand the processes controlling surface snow isotopic composition. Isotopic fractionation processes occurring in the atmosphere and controlling snowfall isotopic composition are well understood theoretically and implemented in atmospheric models. However, post-deposition processes are poorly documented and understood. To quantitatively interpret the isotopic composition of water archived in ice cores, it is thus essential to study the continuum between surface water vapour, precipitation, surface snow and buried snow. Here, we target the isotopic composition of water vapour at Concordia Station, where the oldest EPICA Dome C ice cores have been retrieved. While snowfall and surface snow sampling is routinely performed, accurate measurements of surface water vapour are challenging in such cold and dry conditions. New developments in infrared spectroscopy enable now the measurement of isotopic composition in water vapour traces. Two infrared spectrometers have been deployed at Concordia, allowing continuous, in situ measurements for 1 month in December 2014–January 2015. Comparison of the results from infrared spectroscopy with laboratory measurements of discrete samples trapped using cryogenic sampling validates the relevance of the method to measure isotopic composition in dry conditions. We observe very large diurnal cycles in isotopic composition well correlated with temperature diurnal cycles. Identification of different behaviours of isotopic composition in the water vapour associated with turbulent or stratified regime indicates a strong impact of meteorological processes in local vapour/snow interaction. Even if the vapour isotopic composition seems to be, at least part of the time, at equilibrium with the local snow, the slope of δD against δ18O prevents us from identifying a unique origin leading to this isotopic composition.
Programme: 1110,1013
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Joël Savarino, William C. Vicars, Michel Legrand, Suzanne Preunkert, Bruno Jourdain, Markus M. Frey, Alexandre Kukui, Nicolas Caillon, Jaime Gil Roca. (2016). Oxygen isotope mass balance of atmospheric nitrate at Dome C, East Antarctica, during the OPALE campaign (Vol. 16). Bachelor's thesis, , .
Abstract: Abstract. Variations In The Stable Oxygen Isotope Composition Of Atmospheric Nitrate Act As Novel Tools For Studying Oxidative Processes Taking Place In The Troposphere. They Provide Both Qualitative And Quantitative Constraints On The Pathways Determining The Fate Of Atmospheric Nitrogen Oxides (No + No2 = Nox). The Unique And Distinctive 17o Excess (Δ17o = δ17o − 0.52 × δ18o) Of Ozone, Which Is Transferred To Nox Via Oxidation, Is A Particularly Useful Isotopic Fingerprint In Studies Of Nox Transformations. Constraining The Propagation Of 17o Excess Within The Nox Cycle Is Critical In Polar Areas, Where There Exists The Possibility Of Extending Atmospheric Investigations To The Glacial–interglacial Timescale Using Deep Ice Core Records Of Nitrate. Here We Present Measurements Of The Comprehensive Isotopic Composition Of Atmospheric Nitrate Collected At Dome C (East Antarctic Plateau) During The Austral Summer Of 2011/2012. Nitrate Isotope Analysis Has Been Here Combined For The First Time With Key Precursors Involved In Nitrate Production (Nox, O3, Oh, Ho2, Ro2, Etc.) And Direct Observations Of The Transferrable Δ17o Of Surface Ozone, Which Was Measured At Dome C Throughout 2012 Using Our Recently Developed Analytical Approach. Assuming That Nitrate Is Mainly Produced In Antarctica In Summer Through The Oh + No2 Pathway And Using Concurrent Measurements Of Oh And No2, We Calculated A Δ17o Signature For Nitrate On The Order Of (21–22 ± 3) ‰. These Values Are Lower Than The Measured Values That Ranged Between 27 And 31 ‰. This Discrepancy Between Expected And Observed Δ17o(no3−) Values Suggests The Existence Of An Unknown Process That Contributes Significantly To The Atmospheric Nitrate Budget Over This East Antarctic Region. However, Systematic Errors Or False Isotopic Balance Transfer Functions Are Not Totally Excluded.
Programme: 1011,1149
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Gallée H, Preunkert S, Argentini S, Frey M M, Genthon C, Jourdain B, Pietroni I, Casasanta G, Barral H, Vignon E, Amory C, Legrand M, . (2015). Characterization of the boundary layer at Dome C (East Antarctica) during the OPALE summer campaign
. Atmospheric Chemistry and Physics, 15(11), 6225–6236.
Abstract: Regional climate model MAR (Modèle Atmosphérique Régional) was run for the region of Dome C located on the East Antarctic plateau, during Antarctic summer 2011–2012, in order to refine our understanding of meteorological conditions during the OPALE tropospheric chemistry campaign. A very high vertical resolution is set up in the lower troposphere, with a grid spacing of roughly 2 m. Model output is compared with temperatures and winds observed near the surface and from a 45 m high tower as well as sodar and radiation data. MAR is generally in very good agreement with the observations, but sometimes underestimates cloud formation, leading to an underestimation of the simulated downward long-wave radiation. Absorbed short-wave radiation may also be slightly overestimated due to an underestimation of the snow albedo, and this influences the surface energy budget and atmospheric turbulence. Nevertheless, the model provides sufficiently reliable information about surface turbulent fluxes, vertical profiles of vertical diffusion coefficients and boundary layer height when discussing the representativeness of chemical measurements made nearby the ground surface during field campaigns conducted at Concordia station located at Dome C (3233 m above sea level).
Programme: 414,903,1013
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