The Role of Open Lead Interactions in Atmospheric Ozone Variability Between Arctic Coastal and Inland Sites

Boundary layer atmospheric ozone depletion events (ODEs) are commonly observed across polar sea ice regions following polar sunrise. During March-April 2005 in Alaska, the coastal site of Barrow and inland site of Atqasuk experienced ODEs (O3 \u3c 10 nmol mol-1) concurrently for 31% of the observations, consistent with large spatial scale ozone depletion. However, 7% of the time ODEs were exclusively observed inland at Atqasuk. This phenomenon also occurred during one of nine flights during the BRomine, Ozone, and Mercury EXperiment (BROMEX), when atmospheric vertical profiles at both sites showed near-surface ozone depletion only at Atqasuk on 28 March 2012. Concurrent in-flight BrO measurements made using nadir scanning differential optical absorption spectroscopy (DOAS) showed the differences in ozone vertical profiles at these two sites could not be attributed to differences in locally occurring halogen chemistry. During both studies, backward air mass trajectories showed that the Barrow air masses observed had interacted with open sea ice leads, causing increased vertical mixing and recovery of ozone at Barrow and not Atqasuk, where the air masses only interacted with tundra and consolidated sea ice. These observations suggest that, while it is typical for coastal and inland sites to have similar ozone conditions, open leads may cause heterogeneity in the chemical composition of the springtime Arctic boundary layer over coastal and inland areas adjacent to sea ice regions

Observations of bromine monoxide transport in the Arctic sustained on aerosol particles

The return of sunlight in the polar spring leads to the production of reactive halogen species from the surface snowpack, significantly altering the chemical composition of the Arctic near-surface atmosphere and the fate of long-range transported pollutants, including mercury. Recent work has shown the initial production of reactive bromine at the Arctic surface snowpack; however, we have limited knowledge of the vertical extent of this chemistry, as well as the lifetime and possible transport of reactive bromine aloft. Here, we present bromine monoxide (BrO) and aerosol particle measurements obtained during the March 2012 BRomine Ozone Mercury EXperiment (BROMEX) near Utqiaġvik (Barrow), AK. The airborne differential optical absorption spectroscopy (DOAS) measurements provided an unprecedented level of spatial resolution, over 2 orders of magnitude greater than satellite observations and with vertical resolution unable to be achieved by satellite methods, for BrO in the Arctic. This novel method provided quantitative identification of a BrO plume, between 500 m and 1 km aloft, moving at the speed of the air mass. Concurrent aerosol particle measurements suggest that this lofted reactive bromine plume was transported and maintained at elevated levels through heterogeneous reactions on colocated supermicron aerosol particles, independent of surface snowpack bromine chemistry. This chemical transport mechanism explains the large spatial extents often observed for reactive bromine chemistry, which impacts atmospheric composition and pollutant fate across the Arctic region, beyond areas of initial snowpack halogen production. The possibility of BrO enhancements disconnected from the surface potentially contributes to sustaining BrO in the free troposphere and must also be considered in the interpretation of satellite BrO column observations, particularly in the context of the rapidly changing Arctic sea ice and snowpack

Assistant-based reconstruction of believed destroyed shredded documents

This article introduces the assistance system for the virtual reconstruction of shredded documents developed at Fraunhofer IPK. The system enables the user to reconstruct documents, which often could not be reconstructed by hand. By this system the information contained in the documents can be made usable again. The process of the assistance system is divided into the four phases of Digitalization, Feature-Extraction, Context Matching and Interactive Viewer. In the first phase the fragile and often twisted strips to be reconstructed have to be separated and straightened. They then need to be scanned double-sided, anechoic, and shadeless as well as with highest colour and geometrical fidelity compared to the originals. In the second phase the strips are segmented pixel by pixel from the raw scans. Foreground from background information is separated and describing content features for a discriminative similarity comparison are extracted from the digitized strips. The third phase works on the basis of these calculated features. At first a search space reduction is carried out. Afterwards a pairwise context matching is executed by using dynamic programming algorithms. Thereby similarity scores of all possible combinations of shredder strip pairs are calculated. On the basis of these scores a semi-automatic reconstruction is performed in the interactive viewer in phase four. By doing so strip-pairs are put together gradually to grow partial reconstructions up to complete reconstructed documents by user interaction. In the past, numerous enquiries within the framework of tax and murder investigations could be solved successfully by means of this assistance system, enabling the evaluation of procedural relevant documents; which had been destroyed purposely