Biogeochemistry and Climate

2019 ◽  
pp. 29-43
Author(s):  
Han Dolman
Keyword(s):  
Ice Cores ◽  
Atmospheric Composition ◽  
System Modelling ◽  
Biogeochemical Processes ◽  
Sources And Sinks ◽  
Direct Observations ◽  
Geological Processes ◽  
In Situ Observations ◽  
Insight Into

This chapter focuses on tools for climate research: biogeochemical observations and models. It discusses physical climate observations, such as temperature and humidity, and in situ observations of atmospheric composition. Turning these into reliable climate records appears to be non-trivial. The chapter describes how isotopes are used to get insight into biogeochemical processes. A special category of observations is biogeochemical proxy observations, used to gain insight into geological processes when no direct observations are possible. The example of climate proxy observations, such as those obtained via ice cores, is described. Models are increasingly used to gain insight into sensitivity of climate to changes in the forcing. Earth system modelling has become increasingly complex over the last two decades, including often detailed biogeochemical processes in the ocean and on land. The parametrization of these remains an important research subject. Inverse modelling is being used to identify sources and sinks of greenhouse gases.

scholarly journals A Photometric Study of Regolith Intimate Mixing with Ice-Like Impurity

2021 ◽  
Author(s):  
Dwaipayan Deb ◽  
Pavan Chakraborty
Keyword(s):  
Solar System ◽  
Linear Trend ◽  
Geological Processes ◽  
Solar System Objects ◽  
Shadowing Effect ◽  
Mixing Proportion ◽  
In Situ Observations ◽  
End Members ◽  
Reflectance Data

Abstract Surfaces of solid solar system objects are covered by layers of particulate materials called regolith originated from their surface bedrock. They preserve important information about surface geological processes. Often regolith is composed of more than one type of particle in terms of composition, maturity, size, etc. Experiments and theoretical works are being carried out to constrain the result of mixing and extract the abundance of compositional end-members from regolith spectra. In this work we have studied, photometric light scattering from simulated surfaces made of two different materials – one is highly bright quartz particles ≈ 80µm and the other moderately bright sandstone particles ≈ 250µm. The samples were mixed with varying proportions and investigated at normal illumination conditions to avoid the shadowing effect. Said combinations may resemble ice mixed regolith on various solar system objects and therefore important for in situ observations. We find that the combinations show a linear trend in the corresponding reflectance data in terms of their mixing proportion and some interesting facts come out when compared to previous studies.

In-Situ Observations of the Effect of Electron Irradiation on the Defect Microstructure of Alumina

1997 ◽  
Vol 3 (S2) ◽  
pp. 601-602
Author(s):  
S.-J. Chen ◽  
U. Dahmen ◽  
D.G. Howitt
Keyword(s):  
High Temperature ◽  
Electron Irradiation ◽  
Shear Bands ◽  
Valuable Insight ◽  
High Velocity Impact ◽  
Dislocation Densities ◽  
In Situ Observations ◽  
Very High ◽  
Insight Into

The interaction of radiation produced point defects with a dislocation microstructure at high temperature is of considerable interest and careful high voltage microscopy experiments can provide valuable insight into the mechanisms. Veyssière and Westmacott carried out in-situ experiments monitoring the partial dislocation climbs in Ni3Al induced by thermal vacancies as well as by Frenkel pairs produced during irradiation.1 We report here the results of some preliminary experiments we performed on alumina (A12O3) single crystals with high dislocation densities to study the modification of the microstructure by electron irradiation at high temperature.The dislocation microstructures were produced by shock wave deformation using a high-velocity impact technique. The technique is capable of producing a very high density of defects consisting primarily of basal twins, and slips on the basal, pyramidal and rhombohedral planes in alumina. The dislocations are all of glide type, mostly forming shear bands. A typical microstructure prior to irradiation is shown in figure la.

scholarly journals Cloud microphysical characteristics versus temperature for three Canadian field projects

2002 ◽  
Vol 20 (11) ◽  
pp. 1891-1898 ◽  
Author(s):  
I. Gultepe ◽  
G. A. Isaac ◽  
S. G. Cober
Keyword(s):  
General Circulation ◽  
Research Study ◽  
Liquid Water Content ◽  
Atmospheric Composition ◽  
The Arctic ◽  
Bay Of Fundy ◽  
Arctic Clouds ◽  
Composition And Structure ◽  
In Situ Observations

Abstract. The purpose of this study is to better understand how cloud microphysical characteristics such as liquid water content (LWC) and droplet number concentration (Nd) change with temperature (T). The in situ observations were collected during three research projects including: the Radiation, Aerosol, and Cloud Experiment (RACE) which took place over the Bay of Fundy and Central Ontario during August 1995, the First International Regional Arctic Cloud Experiment (FIRE.ACE) which took place in the Arctic Ocean during April 1998, and the Alliance Icing Research Study (AIRS) which took place in the Ontario region during the winter of 1999–2000. The RACE, FIRE.ACE, and AIRS projects represent summer mid-latitude clouds, Arctic clouds, and mid-latitude winter clouds, respectively. A LWC threshold of 0.005 g m-3 was used for this study. Similar to other studies, LWC was observed to decrease with decreasing T. The LWC-T relationship was similar for all projects, although the range of T conditions for each project was substantially different, and the variability of LWC within each project was considerable. Nd also decreased with decreasing T, and a parameterization for Nd versus T is suggested that may be useful for modeling studies.Key words. Atmospheric composition and structure (cloud physics and chemistry) – Meteorology and atmospheric dynamics (climatology; general circulation)

scholarly journals Local artifacts in ice core methane records caused by layered bubble trapping and in situ production: a multi-site investigation

2016 ◽  
Vol 12 (4) ◽  
pp. 1061-1077 ◽  
Author(s):  
Rachael H. Rhodes ◽  
Xavier Faïn ◽  
Edward J. Brook ◽  
Joseph R. McConnell ◽  
Olivia J. Maselli ◽  
...  
Keyword(s):  
Growth Rate ◽  
High Frequency ◽  
Ice Core ◽  
Ice Cores ◽  
Gas Diffusion ◽  
Atmospheric Composition ◽  
Pass Filter ◽  
Low Pass Filter ◽  
Bubble Trapping

Abstract. Advances in trace gas analysis allow localised, non-atmospheric features to be resolved in ice cores, superimposed on the coherent atmospheric signal. These high-frequency signals could not have survived the low-pass filter effect that gas diffusion in the firn exerts on the atmospheric history and therefore do not result from changes in the atmospheric composition at the ice sheet surface. Using continuous methane (CH4) records obtained from five polar ice cores, we characterise these non-atmospheric signals and explore their origin. Isolated samples, enriched in CH4 in the Tunu13 (Greenland) record are linked to the presence of melt layers. Melting can enrich the methane concentration due to a solubility effect, but we find that an additional in situ process is required to generate the full magnitude of these anomalies. Furthermore, in all the ice cores studied there is evidence of reproducible, decimetre-scale CH4 variability. Through a series of tests, we demonstrate that this is an artifact of layered bubble trapping in a heterogeneous-density firn column; we use the term “trapping signal” for this phenomenon. The peak-to-peak amplitude of the trapping signal is typically 5 ppb, but may exceed 40 ppb. Signal magnitude increases with atmospheric CH4 growth rate and seasonal density contrast, and decreases with accumulation rate. Significant annual periodicity is present in the CH4 variability of two Greenland ice cores, suggesting that layered gas trapping at these sites is controlled by regular, seasonal variations in the physical properties of the firn. Future analytical campaigns should anticipate high-frequency artifacts at high-melt ice core sites or during time periods with high atmospheric CH4 growth rate in order to avoid misinterpretation of such features as past changes in atmospheric composition.

Impact of Assimilating PECAN Profilers on the Prediction of Bore-Driven Nocturnal Convection: A Multiscale Forecast Evaluation for the 6 July 2015 Case Study

2020 ◽  
Vol 148 (3) ◽  
pp. 1147-1175 ◽  
Author(s):  
Hristo G. Chipilski ◽  
Xuguang Wang ◽  
David B. Parsons
Keyword(s):  
Remote Sensing ◽  
Temporal Frequency ◽  
Objective Assessment ◽  
Successful Prediction ◽  
Physical Insight ◽  
In Situ Observations ◽  
Using Data ◽  
Insight Into

Abstract Using data from the 6 July 2015 PECAN case study, this paper provides the first objective assessment of how the assimilation of ground-based remote sensing profilers affects the forecasts of bore-driven convection. To account for the multiscale nature of the phenomenon, data impacts are examined separately with respect to (i) the bore environment, (ii) the explicitly resolved bore, and (iii) the bore-initiated convection. The findings from this work suggest that remote sensing profiling instruments provide considerable advantages over conventional in situ observations, especially when the retrieved data are assimilated at a high temporal frequency. The clearest forecast improvements are seen in terms of the predicted bore environment where the assimilation of kinematic profilers reduces a preexisting bias in the structure of the low-level jet. Data impacts with respect to the other two forecast components are mixed in nature. While the assimilation of thermodynamic retrievals from the Atmospheric Emitted Radiance Interferometer (AERI) results in the best convective forecast, it also creates a positive bias in the height of the convectively generated bore. Conversely, the assimilation of wind profiler data improves the characteristics of the explicitly resolved bore, but tends to further exacerbate the lack of convection in the control forecasts. Various dynamical diagnostics utilized throughout this study provide a physical insight into the data impact results and demonstrate that a successful prediction of bore-driven convection requires an accurate depiction of the internal bore structure as well as the ambient environment ahead of it.

scholarly journals Katabatic winds and piteraq storms: observations from the Greenland ice sheet

1969 ◽  
Vol 33 ◽  
pp. 83-86 ◽  
Author(s):  
Dirk Van As ◽  
Robert S. Fausto ◽  
Konrad Steffen
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Surface Mass ◽  
Surface Ablation ◽  
Iceberg Calving ◽  
Energy Exchanges ◽  
In Situ Observations ◽  
Insight Into

In 2007 the Programme for Monitoring the Greenland Ice Sheet (PROMICE) was initiated to observe and gain insight into the mass budget of Greenland ice masses. By means of in situ observations and remote sensing, PROMICE assesses how much mass is gained as snow accumulation on the surface versus how much is lost by iceberg calving and surface ablation (Ahlstrøm et al. 2008). A key element of PROMICE is a network of automatic weather stations (AWSs) designed to quantify components of the surface mass balance, including the energy exchanges contributing to surface ablation (Van As et al. 2013).

scholarly journals Measurement report: Photochemical production and loss rates of formaldehyde and ozone across Europe

2021 ◽  
Author(s):  
Clara M. Nussbaumer ◽  
John N. Crowley ◽  
Jan Schuladen ◽  
Jonathan Williams ◽  
Sascha Hafermann ◽  
...  
Keyword(s):  
Trace Gases ◽  
Ozone Production ◽  
Trace Gas ◽  
Coastal Site ◽  
Sources And Sinks ◽  
Oxidation Of Methane ◽  
Mountain Site ◽  
In Situ Observations ◽  
Summer Time

Abstract. Various atmospheric sources and sinks regulate the abundance of tropospheric formaldehyde (HCHO) which is an important trace gas impacting the HOx (≡ HO2 + OH) budget and the concentration of ozone (O3). In this study, we present the formation and destruction terms of ambient HCHO and O3 calculated from in-situ observations of various atmospheric trace gases measured at three different sites across Europe during summer time. These include a coastal site in Cyprus in the scope of the Cyprus Photochemistry Experiment (CYPHEX) in 2014, a mountain site in Southern Germany as part of the Hohenpeißenberg Photochemistry Experiment (HOPE) in 2012 and a forested site in Finland where measurements were performed during the Hyytiälä United Measurements of Photochemistry and Particles (HUMPPA) campaign in 2010. We show that at all three sites formaldehyde production from the OH oxidation of methane (CH4), acetaldehyde (CH3CHO), isoprene (C5H8) and methanol (CH3OH) can almost completely balance the observed loss via photolysis, OH oxidation and dry deposition. Ozone chemistry is clearly controlled by nitrogen oxides (NOx ≡ NO + NO2) that includes O3 production from NO2 photolysis and O3 loss via the reaction with NO. Finally, we use the HCHO budget calculations to determine whether net ozone production is limited by the availability of VOCs (VOC limited regime) or NOx (NOx limited regime). At the mountain site in Germany O3 production is VOC limited, whereas it is NOx limited at the coastal site in Cyprus. The forested site in Finland is in the transition regime.

Evolution of the Raikoke volcanic plume in the Northern Hemisphere UT/LS over 9 months past eruption as seen from IAGOS-CARIBIC in-situ observations

2021 ◽  
Author(s):  
Andreas Petzold ◽  
Ulrich Bundke ◽  
Marcel Berg ◽  
Rita Gomes ◽  
Jim Haywood ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Research Programme ◽  
Global Scale ◽  
Number Concentration ◽  
Atmospheric Composition ◽  
Volcanic Plume ◽  
Joint Research ◽  
In Situ Observations ◽  
The Impact

<p>IAGOS (In-Service Aircraft for a Global Observing System; www.iagos.org) is a European Research Infrastructure which uses passenger aircraft equipped with autonomous instrumentation for the continuous and global-scale observation of atmospheric composition in the upper troposphere and lowermost stratosphere (UT/LS; see Petzold et al., 2015). Among others, IAGOS provides today detailed information on atmospheric trace species by the flying laboratory in IAGOS-CARIBIC. Since July 2018, number concentration and fraction of non-volatile particles for d<sub>p</sub> > 15 nm as well as size distributions for d<sub>p</sub> >  250 nm are measured (Bundke et al., 2015). Since lately, aerosol chemical composition is provided as well (Schulz et al., 2020). IAGOS-CARIBIC flight routes covered during the period from July 2018 to March 2020 include regular flights from Munich, Germany, to North America, East Asia and South Africa.</p><p>On 22 June 2019, the Raikoke Volcano on the Kuril Islands erupted and transported vast amounts of gaseous and particulate matter into the UT/LS. Two months after the eruption CALIPSO observed enhanced aerosol optical depth and aerosol scattering across the entire lower stratosphere. IAGOS-CARIBIC conducted several flight series in the Northern Hemisphere before and after the eruption phase such that the pre- and post-eruption data provide profound information on the impact of the Raikoke eruption on the Northern Hemisphere UT/LS aerosol and the evolution of the plume during 9 months of regular observation.</p><p>Data indicate an increase in the number concentration of particles with d<sub>p</sub> > 250 nm by a factor of 10 across the entire sampled altitude range, while the increase of the total aerosol number concentration (d<sub>p</sub><sub> </sub>> 15 nm) is less pronounced but also significant. We present a detailed analysis of the changes in UT/LS aerosol load and properties caused by the Raikoke eruption, including the temporal evolution of the aerosol plume during 9 months past the eruption. In-situ observations are backed-up by CALIPSO products and results from associated volcanic plume modelling studies deploying the UK Earth System Model UKESM1.</p><p>The authors gratefully acknowledge the continuous support of IAGOS by Deutsche Lufthansa. Without their commitment these observations would not have been possible. Parts of this study were funded by the German Ministry for Education and Research (BMBF) under Grant No. 01LK1301A as part of the joint research programme IAGOS Germany.</p><p>Bundke, U., et al. (2015) Tellus B 67, 28339 https://doi.org/10.3402/tellusb.v67.28339.</p><p>Petzold, A., et al. (2015) Tellus B 67, 28452 https://doi.org/10.3402/tellusb.v67.28452.</p><p>Schulz, C., et al. (2020) EAC 2020 Abstract <span>ID 1258</span></p>

scholarly journals Physical and biogeochemical spatial scales of variability in the East Australian Current separation from shelf glider measurements

2016 ◽  
Vol 13 (6) ◽  
pp. 1967-1975 ◽  
Author(s):  
Amandine Schaeffer ◽  
Moninya Roughan ◽  
Emlyn M. Jones ◽  
Dana White
Keyword(s):  
Organic Matter ◽  
Spatial Scales ◽  
Sampling Strategy ◽  
Coastal Processes ◽  
East Australian Current ◽  
Biogeochemical Processes ◽  
Physical Processes ◽  
In Situ Observations ◽  
Sparse Measurements

Abstract. In contrast to physical processes, biogeochemical processes are inherently patchy in the ocean, which affects both the observational sampling strategy and the representativeness of sparse measurements in data assimilating models. In situ observations from multiple glider deployments are analysed to characterize spatial scales of variability in both physical and biogeochemical properties, using an empirical statistical model. We find that decorrelation ranges are strongly dependent on the balance between local dynamics and mesoscale forcing. The shortest horizontal (5–10 km) and vertical (45 m) decorrelation ranges are for chlorophyll a fluorescence, whereas those variables that are a function of regional ocean and atmosphere dynamics (temperature and dissolved oxygen) result in anisotropic patterns with longer ranges along (28–37 km) than across the shelf (8–19 km). Variables affected by coastal processes (salinity and coloured dissolved organic matter) have an isotropic range similar to the baroclinic Rossby radius (10–15 km).

Direct observations of incipient plasticity during nanoindentation of Al

2004 ◽  
Vol 19 (1) ◽  
pp. 176-182 ◽  
Author(s):  
A.M. Minor ◽  
E.T. Lilleodden ◽  
E.A. Stach ◽  
J.W. Morris
Keyword(s):  
Crystalline Silicon ◽  
Dislocation Nucleation ◽  
Direct Observations ◽  
Transmission Electron ◽  
Incipient Plasticity ◽  
Grain Boundary Motion ◽  
Mechanisms Of Plastic Deformation ◽  
Insight Into

The mechanical testing technique for in situ nanoindentation in a transmission electron microscope is described and is shown to provide real-time observations of the mechanisms of plastic deformation that occur during nanoindentation. Here, the importance of this technique was demonstrated on an aluminum thin film deposited on a single-crystalline silicon substrate. Significant results include direct observation of dislocation nucleation, characterization of the dislocation distribution created by indentation, and the observation of indentation-induced grain boundary motion. The observations achieved by this technique provide unique insight into mechanical behavior studied with conventional instrumented nanoindentation techniques and also provide microstructural-level understanding of the mechanics of ultrasmall volumes.

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