Satellite observations of long range transport of a large BrO plume in the Arctic

Ozone Depletion Events (ODE) during polar springtime are a well known phenomenon in the Arctic and Antarctic boundary layer. They are caused by the catalytic destruction of ozone by halogens producing reactive halogen oxides like bromine monoxide (BrO). The key halogen bromine can be rapidly transferred into the gas phase in an autocatalytic process – the so called "Bromine Explosion". However, the exact mechanism, which leads to an initial bromine release as well as the influence of transport and chemical processes on BrO, is still not clearly understood. <br><br> In this study, BrO measurements from the satellite instrument GOME-2 are used together with model calculations with the dispersion model FLEXPART to study an arctic BrO event in March 2007, which could be tracked over several days and a large area. Full BrO activation was observed within one day east of Siberia with subsequent transport to Hudson Bay. The event was linked to a cyclone with very high surface wind speeds, which could have been involved in the production and lifting of aerosols or blowing snow. Considering the short life time of BrO, transported aerosols or snow can also provide the surface for BrO recycling within the plume for several days. The evolution of the BrO plume could be reproduced by FLEXPART simulations of a passive tracer indicating that the activated air mass was transported all the way from Siberia to Hudson Bay. To localise the most probable transport height, model runs initialised in different heights have been performed showing similar transport patterns throughout the troposphere but best agreement with the measurements between the surface and 3 km. The influence of changes in tropopause height on measured BrO values has been considered, but cannot completely explain the observed high BrO values. Backward trajectories from the area of BrO initialisation show upward lifting from the surface up to 3 km and no indication for intrusion of stratospheric air. These observations are consistent with a scenario in which bromine in the air mass was activated on the surface within the cyclone, lifted upwards and transported over several thousand kilometres to Hudson Bay

Global observations of tropospheric BrO columns using GOME-2 satellite data

Measurements from the GOME-2 satellite instrument have been analyzed for tropospheric BrO using a residual technique that combines measured BrO columns and estimates of the stratospheric BrO content from a climatological approach driven by O<sub>3</sub> and NO<sub>2</sub> observations. Comparisons between the GOME-2 results and BrO vertical columns derived from correlative ground-based and SCIAMACHY nadir observations, present a good level of consistency. We show that the adopted technique enables separation of stratospheric and tropospheric fractions of the measured total BrO columns and allows quantitative study of the BrO plumes in polar regions. While some satellite observed plumes of enhanced BrO can be explained by stratospheric descending air, we show that most BrO hotspots are of tropospheric origin, although they are often associated to regions with low tropopause heights as well. Elaborating on simulations using the <i>p</i>-TOMCAT tropospheric chemical transport model, this result is found to be consistent with the mechanism of bromine release through sea salt aerosols production during blowing snow events. No definitive conclusion can be drawn however on the importance of blowing snow sources in comparison to other bromine release mechanisms. Outside polar regions, evidence is provided for a global tropospheric BrO background with column of 1–3 × 10<sup>13</sup> molec cm<sup>−2</sup>, consistent with previous estimates

Corrigendum to "Simultaneous satellite observations of IO and BrO over Antarctica" published in Atmos. Chem. Phys., 12, 6565–6580, 2012

No abstract available

Nitrate postdeposition processes in Svalbard surface snow

The snowpack acts as a sink for atmospheric reactive nitrogen, but several postdeposition pathways have been reported to alter the concentration and isotopic composition of snow nitrate with implications for atmospheric boundary layer chemistry, ice core records, and terrestrial ecology following snow melt. Careful daily sampling of surface snow during winter (11–15 February 2010) and springtime (9 April to 5 May 2010) near Ny‐Ålesund, Svalbard reveals a complex pattern of processes within the snowpack. Dry deposition was found to dominate over postdeposition losses, with a net nitrate deposition rate of (0.6 ± 0.2) µmol m−2 d−1 to homogeneous surface snow. At Ny‐Ålesund, such surface dry deposition can either solely result from long‐range atmospheric transport of oxidized nitrogen or include the redeposition of photolytic/bacterial emission originating from deeper snow layers. Our data further confirm that polar basin air masses bring 15N‐depleted nitrate to Svalbard, while high nitrate δ(18O) values only occur in connection with ozone‐depleted air, and show that these signatures are reflected in the deposited nitrate. Such ozone‐depleted air is attributed to active halogen chemistry in the air masses advected to the site. However, here the Ny‐Ålesund surface snow was shown to have an active role in the halogen dynamics for this region, as indicated by declining bromide concentrations and increasing nitrate δ(18O), during high BrO (low‐ozone) events. The data also indicate that the snowpack BrO‐NOx cycling continued in postevent periods, when ambient ozone and BrO levels recovered

A Dynamic Approach of Information in a Learning Task

A new theoretical and methodological approach of the processing of information is presented. On line modifications in the structure of information, such as stretched, broken, re- unified, or stuck pieces of information can be characterized from linguistic markers. For that two kinds of detachability from the situation are analyzed in a cognitive interpretation of Culioli's enunciative model. On one hand, the detachability linked to starting terms has for criterion the anaphora. It marks the categorization of external aggregates of information, their internalization, re-inscribing them at a subjective level, and their externalization, re-inscribing them in the spatio temporal environment. On the other hand, the detachability linked to modal terms marks a strategic reorganization of information. Both kinds of detachability are modelled by Culioli's diagram involving different levels between parameters S (subjective space) and T (temporal space). The passages from one of these levels to another follow specific routes with loops and strange loops. This paper analyzes the modification of information at the highest subjective level in the verbal protocol of a 10-year- old solving the Tower of Hanoi puzzle for the first time. The generalization to other tasks and to interaction between intelligent agents results from the interactive characteristics of linguistic markers

A memory institution for the digital age

The German National Library for Science and Technology (TIB) seizes the opportunity of an epochal change into the Digital Age, inter alia, by maintaining a prestigious research department covering the areas data science & digital libraries, visual analytics, scientific data management, knowledge infrastructures, learning & skill analytics, open science, and non-textual media. Without neglecting the original mission of collecting and curating literature for a widespread access to scientific information, TIB merges well-established processes with intelligent assistance tools. The Specialised Information Service for Mobility and Traffic Science (FID move) is one example of combining the mentioned research areas in order to build a user-centred subject-specific research infrastructure to support and shape tomorrow’s scientific work. We give a detailed introduction to the project’s action fields: web service platform, information supply with a focus on open access, strategy & structure for reusable research data, research community exchange & networking, communication strategies for the public & for scientists. Exemplary, we present the ongoing activities in building a comprehensive knowledge organisation system for e-mobility

Effets des labels verbaux dans une résolution de problème (approche énonciative)

POITIERS-BU Droit Lettres (861942101) / SudocSudocFranceF

Das Verhalten nanostrukturierter Schaltungen unter der Berücksichtigung von Quanteneffekten [The behavior of nanostructured circuits with regard to quantum effects]

In this paper we discuss the expected impact of quantum effects in nanostructured CMOS circuits. In order to describe transport in mesoscopic electronic systems our group develops a 1-d numerical simulation packet based on the "non equilibrium Green's functions" (NEGF) formalism. By means of the obtained simulation results we develop extended SPICE circuit models. With these SPICE models the influence of quantum effects to the functionality of classical circuit concepts can be studied. Using these results it is our intention to develop circuits with a higher robustness against these quantum effects. For the illustration of our simulation concept we discuss some results of some circuit examples.Aufgrund der Bedeutung der MOS-Technologie für Halbleiterindustrie und deren fortschreitende Miniaturisierung ist es wichtig sicherzustellen, dass die klassischen Schaltungskonzepte für stark skalierte Bauelemente nicht ihre Gültigkeit verlieren. Ziel unserer Arbeitsgruppe ist es ein Simulatorpaket zu entwickeln, welches von einer physikalischen Sicht heraus quantenmechanische Einflüsse in integrierten Schaltungen ermittelt und Konsequenzen für zukünftiges Schaltungsdesign prognostiziert. Zur Berechnung und Modellierung der Quanteneffekte wird ein auf dem "non equilibrium Green's functions" (NEGF) Formalismus basierender numerischer 1-dimensionaler Simulator entwickelt. Auf der Basis von numerischen Transportsimulationen werden Ersatzschaltbilder für die SPICE Simulationsumgebung erstellt, um den Einfluss der Quanteneffekte in die Schaltungssimulation einzubinden