Direct Observations of Anthracene Clusters at Ice Surfaces

2021 ◽  
Author(s):  
Subha Chakraborty ◽  
Annastacia Stubbs ◽  
Tara Kahan
Keyword(s):  
Chemical Speciation ◽  
Lateral Diffusion ◽  
Atmospheric Composition ◽  
Atmospheric Sciences ◽  
Direct Observations ◽  
Heterogeneous Processes ◽  
Model Predictions ◽  
Ice Surfaces ◽  
Self Association ◽  
Reaction Media

Heterogeneous processes can control atmospheric composition. Snow and ice present important, but poorly understood, reaction media that can greatly alter the composition of air in the cryosphere in polar and temperate regions. Atmospheric scientists struggle to reconcile model predictions with field observations in snow-covered regions due to experimental challenges associated with monitoring reactions at air-ice interfaces, and debate regarding reaction kinetics and mechanisms has persisted for over a decade. In this work, we use wavelength-resolved fluorescence microscopy to determine the distribution and chemical speciation of the pollutant anthracene at the surfaces of environmentally relevant frozen surfaces. We show that anthracene adsorbs to frozen surfaces in monomeric form, but that following lateral diffusion, molecules ultimately reside within brine channels at saltwater ice surfaces, and in micron-sized clusters at freshwater ice surfaces; emission profiles indicate extensive self-association. We also measure anthracene photodegradation kinetics in aqueous solution and artificial snow prepared from frozen freshwater and saltwater solutions and use the micro-spectroscopic observations to explain the rate constants measured in different environments. These results resolve long-standing debates and will improve predictions of pollutant fate in the cryosphere. The techniques used can be applied to numerous surfaces within and beyond the atmospheric sciences.

A laboratory and model investigation of secondary ice production during to supercooled drop collisions with ice surfaces 

2021 ◽  
Author(s):  
Paul Connolly ◽  
Rachel James ◽  
Vaughan Phillips
Keyword(s):  
Laboratory Data ◽  
Ice Formation ◽  
Atmospheric Sciences ◽  
Ice Particles ◽  
Cold Room ◽  
Mode 2 ◽  
Rain Drops ◽  
Break Up ◽  
Ice Surfaces ◽  
Ice Production

<p>This work presents new laboratory data investigating collisions between supercooled drops and ice particles as a source of secondary ice particles in natural clouds. Furthermore we present numerical model simulations to put the laboratory measurements into context.</p><p>Secondary ice particles form during the breakup of freezing drops due to so-called “spherical freezing” (or Mode 1), where an ice shell forms around the freezing drop. This process has been studied and observed for drops in free-fall in laboratory experiments since the 1960s, and also more recently by Lauber et al. (2018) with a high-speed camera. Aircraft field measurements (Lawson et al. 2015) and lab data (Kolomeychuk et al. 1975) suggest that such a process is dependent on the size of drops, with larger drops being more effective at producing secondary ice.  Collision induced break-up of rain drops has been well studied with pioneering investigations in the mid-1980s, and numerous modelling studies showing that it is responsible for observed trimodal rain drop size distributions in the atmosphere, which can be well approximated by an exponential distribution.</p><p> </p><p>In mixed-phase clouds we know that rain-drops can collide with more massive ice particles. This, depending on the type of collision, may lead to the break-up of the supercooled drop (e.g. as hinted by Latham and Warwicker, 1980), potentially stimulating secondary ice formation (Phillips et al. 2018 - non-spherical, Mode 2).  There is a dearth of laboratory data investigating this mechanism.  This mechanism is the focus of the presentation.</p><p>Here we present the results of recent experiments where we make use of the University of Manchester (UoM) cold room facility. The UoM cold room facility consists of 3 stacked cold rooms that can be cooled to temperatures below -55 degC. A new facility has been built to study secondary ice production via Mode 2 fragmentation. We generate supercooled drops at the top of the cold rooms and allow them to interact with different ice surfaces near the bottom. This interaction is filmed with a new camera setup.</p><p>Our latest results will be presented at the conference.</p><p>References</p><p>Kolomeychuk, R. J., D. C. McKay, and J. V. Iribarne. 1975. “The Fragmentation and Electrification of Freezing Drops.” <em>Journal of the Atmospheric Sciences</em> 32 (5): 974–79. https://doi.org/10.1175/1520-0469(1975)032<0974>2.0.CO;2.</p><p>Latham, J., and R. Warwicker. 1980. “Charge Transfer Accompanying the Splashing of Supercooled Raindrops on Hailstones.” Quarterly Journal of the Royal Meteorological Society 106 (449): 559–68. https://doi.org/10.1002/qj.49710644912.</p><p>Lauber, Annika, Alexei Kiselev, Thomas Pander, Patricia Handmann, and Thomas Leisner. 2018. “Secondary Ice Formation during Freezing of Levitated Droplets.” Journal of the Atmospheric Sciences 75 (8): 2815–26. https://doi.org/10.1175/JAS-D-18-0052.1.</p><p>Lawson, R. Paul, Sarah Woods, and Hugh Morrison. 2015. “The Microphysics of Ice and Precipitation Development in Tropical Cumulus Clouds.” Journal of the Atmospheric Sciences 72 (6): 2429–45. https://doi.org/10.1175/JAS-D-14-0274.1.</p><p> </p><p> </p>

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 The red-sky enigma over Svalbard in December 2002

2005 ◽  
Vol 23 (5) ◽  
pp. 1593-1602
Author(s):  
F. Sigernes ◽  
N. Lloyd ◽  
D. A. Lorentzen ◽  
R. Neuber ◽  
U.-P. Hoppe ◽  
...  
Keyword(s):  
Scattered Light ◽  
Atmospheric Composition ◽  
The Sun ◽  
Polar Stratospheric Clouds ◽  
Atmospheric Sciences ◽  
Composition And Structure ◽  
History Of Geophysics ◽  
History Of ◽  
Instruments And Techniques ◽  
Stratospheric Clouds

Abstract. On 6 December 2002, during winter darkness, an extraordinary event occurred in the sky, as viewed from Longyearbyen (78° N, 15° E), Svalbard, Norway. At 07:30 UT the southeast sky was surprisingly lit up in a deep red colour. The light increased in intensity and spread out across the sky, and at 10:00 UT the illumination was observed to reach the zenith. The event died out at about 12:30 UT. Spectral measurements from the Auroral Station in Adventdalen confirm that the light was scattered sunlight. Even though the Sun was between 11.8 and 14.6deg below the horizon during the event, the measured intensities of scattered light on the southern horizon from the scanning photometers coincided with the rise and setting of the Sun. Calculations of actual heights, including refraction and atmospheric screening, indicate that the event most likely was scattered solar light from a target below the horizon. This is also confirmed by the OSIRIS instrument on board the Odin satellite. The deduced height profile indicates that the scattering target is located 18–23km up in the stratosphere at a latitude close to 73–75° N, southeast of Longyearbyen. The temperatures in this region were found to be low enough for Polar Stratospheric Clouds (PSC) to be formed. The target was also identified as PSC by the LIDAR systems at the Koldewey Station in Ny-Ålesund (79° N, 12° E). The event was most likely caused by solar illuminated type II Polar Stratospheric Clouds that scattered light towards Svalbard. Two types of scenarios are presented to explain how light is scattered. Keywords. Atmospheric composition and structure (Transmissions and scattering of radiation; Middle atmospherecomposition and chemistry; Instruments and techniques) – History of geophysics (Atmospheric Sciences; The red-sky phenomena)

scholarly journals Metal speciation from stream to open ocean: modelling v. measurement

2016 ◽  
Vol 13 (3) ◽  
pp. 464 ◽  
Author(s):  
Edward Tipping ◽  
Stephen Lofts ◽  
Anthony Stockdale
Keyword(s):  
Coastal Waters ◽  
Natural Waters ◽  
Chemical Speciation ◽  
Metal Speciation ◽  
Open Ocean ◽  
Large Set ◽  
Data Set ◽  
Fresh Waters ◽  
Speciation Model ◽  
Model Predictions

Environmental contextThe chemical speciation of metals strongly influences their transport, fate and bioavailability in natural waters. Analytical measurement and modelling both play important roles in understanding speciation, while modelling is also needed for prediction. Here, we analyse a large set of data for fresh waters, estuarine and coastal waters, and open ocean water, to examine how well measurements and modelling predictions agree. AbstractWe compiled a data set of ~2000 published metal speciation measurements made on samples of fresh waters, estuarine and coastal waters, and open ocean waters. For each sample, we applied the chemical speciation model WHAM7 to calculate the equilibrium free metal ion concentrations, [M] (molL–1), amounts of metal bound by dissolved organic matter (DOM), ν (molg–1), and their ratio ν/[M] (L g–1), which is a kind of ‘local’ partition coefficient. Comparison of the measured and predicted speciation variables for the whole data set showed that agreements are best for fresh waters, followed by estuarine and coastal waters, then open-ocean waters. Predicted values of ν/[M], averaged over all results for each metal, closely follow the trend in average measured values, confirming that metal reactivity, and consequent complexation by DOM, in natural waters accord with the expectations of the speciation model. Comparison of model predictions with measurements by different analytical techniques suggests that competitive ligand–stripping voltammetry methods overestimate metal complexation by DOM, and therefore underestimate [M]. When measurements by other methods are compared with predictions, for all metals, reasonable agreement with little bias is obtained at values of ν>10–6molg–1 DOM, but at lower values of ν, the model predictions of [M] are mostly higher than the measured values, and the predictions of ν and ν/[M] are mostly lower. Research is needed to establish whether this reflects analytical error or the failure of the model to represent natural high-affinity ligands.

scholarly journals Optimal Estimation Retrievals and Their Uncertainties: What Every Atmospheric Scientist Should Know

2020 ◽  
Vol 101 (9) ◽  
pp. E1512-E1523 ◽  
Author(s):  
Maximilian Maahn ◽  
David D. Turner ◽  
Ulrich Löhnert ◽  
Derek J. Posselt ◽  
Kerstin Ebell ◽  
...  
Keyword(s):  
Optimal Solution ◽  
Optimal Estimation ◽  
Atmospheric Sciences ◽  
Direct Observations ◽  
Retrieval Algorithms ◽  
Distribution Parameters ◽  
Ill Posed ◽  
Retrieval Problem ◽  
Atmospheric State

Abstract Remote sensing instruments are heavily used to provide observations for both the operational and research communities. These sensors do not provide direct observations of the desired atmospheric variables, but instead, retrieval algorithms are necessary to convert the indirect observations into the variable of interest. It is critical to be aware of the underlying assumptions made by many retrieval algorithms, including that the retrieval problem is often ill posed and that there are various sources of uncertainty that need to be treated properly. In short, the retrieval challenge is to invert a set of noisy observations to obtain estimates of atmospheric quantities. The problem is often complicated by imperfect forward models, by imperfect prior knowledge, and by the existence of nonunique solutions. Optimal estimation (OE) is a widely used physical retrieval method that combines measurements, prior information, and the corresponding uncertainties based on Bayes’s theorem to find an optimal solution for the atmospheric state. Furthermore, OE also allows the relative contributions of the different sources of error to the uncertainty in the final retrieved atmospheric state to be understood. Here, we provide a novel Python library to illustrate the use of OE for inverse problems in the atmospheric sciences. We introduce two example problems: how to retrieve drop size distribution parameters from radar observations and how to retrieve the temperature profile from ground-based microwave sensors. Using these examples, we discuss common pitfalls, how the various error sources impact the retrieval, and how the quality of the retrieval results can be quantified.

scholarly journals <i>Letter to the Editor</i> Aerosol radiative forcing over land: effect of surface and cloud reflection

2002 ◽  
Vol 20 (12) ◽  
pp. 2105-2109 ◽  
Author(s):  
S. K. Satheesh
Keyword(s):  
Optical Depth ◽  
Atmospheric Aerosols ◽  
Radiative Forcing ◽  
Tropical Indian Ocean ◽  
Atmospheric Composition ◽  
Aerosol Layer ◽  
Atmospheric Sciences ◽  
Aerosol Radiative Forcing ◽  
Aerosol Forcing ◽  
Absorbing Aerosols

Abstract. It is now clearly understood that atmospheric aerosols have a significant impact on climate due to their important role in modifying the incoming solar and outgoing infrared radiation. The question of whether aerosol cools (negative forcing) or warms (positive forcing) the planet depends on the relative dominance of absorbing aerosols. Recent investigations over the tropical Indian Ocean have shown that, irrespective of the comparatively small percentage contribution in optical depth ( ~ 11%), soot has an important role in the overall radiative forcing. However, when the amount of absorbing aerosols such as soot are significant, aerosol optical depth and chemical composition are not the only determinants of aerosol climate effects, but the altitude of the aerosol layer and the altitude and type of clouds are also important. In this paper, the aerosol forcing in the presence of clouds and the effect of different surface types (ocean, soil, vegetation, and different combinations of soil and vegetation) are examined based on model simulations, demonstrating that aerosol forcing changes sign from negative (cooling) to positive (warming) when reflection from below (either due to land or clouds) is high.Key words. Atmospheric composition and structure (aerosols and particles) History of Geophysics (atmospheric sciences) Hydrology (anthropogenic effects)

scholarly journals A benchmark for testing the accuracy and computational cost of shortwave top-of-atmosphere reflectance calculations in clear-sky aerosol-laden atmospheres

2019 ◽  
Vol 12 (2) ◽  
pp. 805-827 ◽  
Author(s):  
Jeronimo Escribano ◽  
Alessio Bozzo ◽  
Philippe Dubuisson ◽  
Johannes Flemming ◽  
Robin J. Hogan ◽  
...  
Keyword(s):  
Radiative Transfer ◽  
Reference Model ◽  
Computational Cost ◽  
Atmospheric Composition ◽  
Scattering Method ◽  
Atmospheric Sciences ◽  
Clear Sky ◽  
Transfer Equations ◽  
Potential Resource ◽  
Radiative Transfer Equations

Abstract. Accurate calculations of shortwave reflectances in clear-sky aerosol-laden atmospheres are necessary for various applications in atmospheric sciences. However, computational cost becomes increasingly important for some applications such as data assimilation of top-of-atmosphere reflectances in models of atmospheric composition. This study aims to provide a benchmark that can help in assessing these two requirements in combination. We describe a protocol and input data for 44 080 cases involving various solar and viewing geometries, four different surfaces (one oceanic bidirectional reflectance function and three albedo values for a Lambertian surface), eight aerosol optical depths, five wavelengths, and four aerosol types. We first consider two models relying on the discrete ordinate method: VLIDORT (in vector and scalar configurations) and DISORT (scalar configuration only). We use VLIDORT in its vector configuration as a reference model and quantify the loss of accuracy due to (i) neglecting the effect of polarization in DISORT and VLIDORT (scalar) models and (ii) decreasing the number of streams in DISORT. We further test two other models: the 6SV2 model, relying on the successive orders of scattering method, and Forward-Lobe Two-Stream Radiance Model (FLOTSAM), a new model under development by two of the authors. Typical mean fractional errors of 2.8 % and 2.4 % for 6SV2 and FLOTSAM are found, respectively. Computational cost depends on the input parameters but also on the code implementation and application as some models solve the radiative transfer equations for a range of geometries while others do not. All necessary input and output data are provided as a Supplement as a potential resource for interested developers and users of radiative transfer models.

scholarly journals The influence of clouds on radical concentrations: observations and modelling studies of HO<sub>x</sub> during the Hill Cap Cloud Thuringia (HCCT) campaign in 2010

2015 ◽  
Vol 15 (6) ◽  
pp. 3289-3301 ◽  
Author(s):  
L. K. Whalley ◽  
D. Stone ◽  
I. J. George ◽  
S. Mertes ◽  
D. van Pinxteren ◽  
...  
Keyword(s):  
Droplet Surface ◽  
Atmospheric Composition ◽  
Uptake Coefficient ◽  
Transport Models ◽  
Cloud Droplets ◽  
Direct Observations ◽  
Modelling Studies ◽  
The Hill ◽  
Ho2 Radical ◽  
Good Agreement

Abstract. The potential for chemistry occurring in cloud droplets to impact atmospheric composition has been known for some time. However, the lack of direct observations and uncertainty in the magnitude of these reactions led to this area being overlooked in most chemistry transport models. Here we present observations from Mt Schmücke, Germany, of the HO2 radical made alongside a suite of cloud measurements. HO2 concentrations were depleted in-cloud by up to 90% with the rate of heterogeneous loss of HO2 to clouds necessary to bring model and measurements into agreement, demonstrating a dependence on droplet surface area and pH. This provides the first observationally derived assessment for the uptake coefficient of HO2 to cloud droplets and was found to be in good agreement with theoretically derived parameterisations. Global model simulations, including this cloud uptake, showed impacts on the oxidising capacity of the troposphere that depended critically on whether the HO2 uptake leads to production of H2O2 or H2O.

scholarly journals Cézeaux-Aulnat-Opme-Puy De Dôme: a multi-site for the long term survey of the tropospheric composition and climate change

2019 ◽  
Author(s):  
Jean-Luc Baray ◽  
Laurent Deguillaume ◽  
Aurélie Colomb ◽  
Karine Sellegri ◽  
Evelyn Freney ◽  
...  
Keyword(s):  
Climate Models ◽  
Scientific Research ◽  
Climate Science ◽  
Time Of Day ◽  
Atmospheric Composition ◽  
Natural Conditions ◽  
Atmospheric Sciences ◽  
Cloud Properties ◽  
Instrumental Development

Abstract. For the last twenty-five years, CO-PDD (Cézeaux-Aulnat-Opme-puy de Dôme) has evolved to become a full instrumented platform for atmospheric research. It is nationally accredited by CNRS, the French national center for scientific research, and recognized as a global station in the GAW network (Global Atmospheric Watch). It is a reference site of the European and national research infrastructures ACTRIS (Aerosol Cloud and Trace gases Research Infrastructure) and ICOS (Integrated Carbon Observing System). The site located on-top of the puy de Dôme mountain (1465 m a.s.l.) is completed by additional sites located at lower altitudes and adding the vertical dimension to the atmospheric observations: Opme (660 m a.s.l.), Cézeaux (410 m) and Aulnat (330 m). On the sites has been developed a unique combination of in-situ and remote sensing measurements capturing and documenting the variability of particulate and gaseous atmospheric composition, but also the optical, biochemical and physical properties of aerosol particles, clouds and precipitations. Given its location far away from any major emission sources, its altitude and the mountain orography, the puy de Dôme station is ideally situated to sample different air masses in the boundary layer or in the free troposphere depending on time of day and seasons. It is also an ideal place to study cloud properties with frequent presence of clouds at the top in autumn and winter. As a result of the natural conditions prevailing at the site and of the very exhaustive instrumental deployment, scientific studies at puy de Dôme strongly contribute to improving the knowledge in atmospheric sciences including the characterization of trends and variability, the understanding of complex and interconnected processes (microphysical, chemical, biological, chemical and dynamical) and providing a reference point for climate models. In this context, CO-PDD is a pilot site to conduct instrumental development inside its wind tunnel for testing liquid/ice cloud probes in natural conditions, or in-situ systems to collect aerosol and cloud. This paper reviews 25 years (1995–2020) of atmospheric observation at the station, and related scientific research contributing to atmospheric and climate science.

scholarly journals Effect of mantle oxidation state and escape upon the evolution of Earth's magma ocean atmosphere

2020 ◽  
Author(s):  
Nisha Katyal ◽  
Gianluigi Ortenzi ◽  
John Lee Grenfell ◽  
Lena Noack ◽  
Frank Sohl ◽  
...  
Keyword(s):  
Chemical Speciation ◽  
Longwave Radiation ◽  
Infrared Emission ◽  
Atmospheric Composition ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Magma Ocean ◽  
Effective Height ◽  
Redox States ◽  
The Impact

&lt;p&gt;The magma ocean is a critical phase determining how Earth's atmosphere developed into habitability. However there are major uncertainties in the role of key processes such as outgassing from the planetary interior and escape to space which determine subsequent atmospheric evolution.&amp;#160; We investigate the impact of outgassing of species and escape of H&lt;sub&gt;2&lt;/sub&gt; for different mantle redox states upon the composition and evolution of the atmosphere for the magma ocean period. We include an important new atmosphere-interior coupling namely the redox evolution of the mantle which strongly affects the outgassing of species. We simulate volatile outgassing and chemical speciation at the surface for various redox states of the mantle by employing a C-H-O based chemical speciation model combined with an interior outgassing model.&lt;br /&gt;We then apply a Line-By-Line radiative transfer model (GARLIC) to study the remote appearance of the planet in terms of the thermal infrared emission and transmission. Finally, we use a diffusion-limited and energy-driven &amp;#160;escape model for calculating the loss of H&lt;sub&gt;2&lt;/sub&gt; from the atmosphere. We obtain that the outgoing longwave radiation and effective height of the atmosphere are potentially influenced by the redox state of the mantle and the volatile outgassing from the magma ocean. An atmosphere above a reduced mantle consisting of light H&lt;sub&gt;2&lt;/sub&gt; emits larger outgoing radiation to space and has a larger effective height compared with heavier, oxidized atmospheres consisting of H&lt;sub&gt;2&lt;/sub&gt;O and CO&lt;sub&gt;2&lt;/sub&gt; lying above an oxidized mantle. We simulate responses in the nature and composition of the atmosphere over the magma ocean period. Results also suggest that outgassing rates of H&lt;sub&gt;2&lt;/sub&gt; can be a factor of x10 larger than those of diffusive H&lt;sub&gt;2&lt;/sub&gt; escape rate during this period. We evaluate the mass-loss timescale of H&lt;sub&gt;2&lt;/sub&gt; via escape of the primary outgassed H&lt;sub&gt;2&lt;/sub&gt; atmosphere to be within few tens of Myr. Our work presents useful input to guide future studies such as those discussing exoplanetary interior composition and its possible links with atmospheric composition that might be estimated from observed infrared spectra (via retrieval) by future planned missions such as ELT, ARIEL and JWST etc.&lt;/p&gt;

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