Ozone and PAN Formation Inside and Outside of the Berlin Plume – Process Analysis and Numerical Process Simulation

During the BERLIOZ field phase on 20 July 1998 a 40 km wide ozone-plume 30 to 70 km north of Berlin in the lee of the city was detected. The ozone mixing ratio inside the plume was app. 15 ppb higher than outside, mainly caused by high ozone precursor emissions in Berlin, resulting in a net chemical ozone production of 6.5 ppb h^–1, which overcompensates ozone advection of –3.6 ppb h^–1 andturbulent diffusion of –1.1 ppb h^–1. That means, although moreozone leaves the control volume far in the lee of Berlin than enters it at the leeside cityborder and although turbulent diffusion causes a loss of ozone in the leeside control volume the chemical production inside the volume leads to a net ozone increase. Using a semi-Lagrangian mass budget method to estimate the net ozone production, 5.0 ppb h^–1 are calculated for theplume. This means a fraction of about 20% of ozone in the plume is producedby local emissions, therefore called `home made' by the Berlin emissions. For the same area KAMM/DRAIS simulations using an observation based initialisation, results in a net production rate between 4.0 and 6.5 ppbh^–1, while the threefold nested EURAD model gives 6.0 ppbh^–1. The process analysis indicates in many cases goodagreement (10% or better) between measurements and simulations not only in the ozone concentrations but also with respect to the physical and chemical processes governing the total change. Remaining differences are caused by different resolution in time and space of the models and measurements as well as by errors in the emission calculation.The upwind-downwind differences in PAN concentrations are partly similar to those of ozone, because in the BERLIOZ case they are governed mainly by photochemical production. While in the stable boundary layer at night and windward of Berlin 0.1 to 0.3 ppb are detected, in the centre of the plume at noon concentrations between 0.75 ppb and 1.0 ppb are measured. The O₃/PAN ratio is about 80 to 120 and thus due to the relatively lowPAN concentrations significantly higher than found in previous studies. The low PAN formation on 20 July, was mainly restricted by the moderate nonmethane hydrocarbon levels, whereas high PAN concentrations of 3.0 ppb on 21 July, are caused by local production in the boundary layer and by large scale advection aloft.     

Integrative multiplicity through suburban realities: exploring diversity through public spaces in Scarborough

Questions of “integration” are normatively assumed to promote particular ideals of the multicultural city and lead to a “settlement” culture that bodes well with the hegemonic majority. This paper, however, questions the concept from an alternative perspective – that is, it aims to explore how “integration” is imagined and understood by displaced migrants through the contextual specificities of multiple and peripheral “public spaces” – defined in this paper as the everyday practices of integrative multiplicity. Exploring these questions in Scarborough, a post-war primarily ethno-racialized suburb of Toronto, the unique experiences of migrants, many who have faced histories of trauma and violence suggest that the settlement experience is not devoid of anxiety and pain. Memories of places and communities left behind, sometimes never to be returned to, harness a longing and deeper need for home-making often spilling into the public realm. Understanding public space and its inherent conceptual and political complexity as defined, used, and valued by recent migrants, allows integration to be understood through the dynamics of power relations. The findings reveal how recent migrants not only understand and use the city but also how they reflect upon and envision the city-building process, through their own individual subjectivities of inclusion/place-making and exclusion/displacement. Through such complex spaces of encounter, civic engagement and grounded experiences, the participants frame Scarborough in multiple and metaphorical forms: from a City of Refuge and Peace; City of Memory, Desire, and Imagination; City of Multifariousness; to a City of Civic Engagement and Fluid Resistance. This stands in stark contrast from how the city is framed in dominant discourse and the unsettling debates on how to reform it.     

A new flare star member candidate in the Pleiades cluster

We present a new flare star, which was discovered during our survey on a selected field at the edge of the Pleiades cluster. The field was observed in the period 2007–2010 with three different CCD‐cameras at the University Observatory Jena with telescopes from 25 to 90 cm. The flare duration is almost one hour with an amplitude in the R‐band of about 1.08 mag. The location of the flare star in a color‐magnitude diagram is consistent with age and distance of the Pleiades. In the optical PSF of the flare star there are two 2MASS objects (unresolved in most images in the optical Jena PSF), so it is not yet known which one of them is responsible for this flare. The BVRIJHK colors yield spectral types of M1 and M2 with extinction being A_v = 0.231 ± 0.024 mag and A_v = 0.266 ± 0.020 for those two stars, consistent with the Pleiades cluster (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hydrogen peroxide production rates in clean and polluted coastal marine waters of the Mediterranean, Red and Baltic Seas

The main aim of this study was to assess the hydrogen peroxide (HP) production rates (HPPR) related to anthropogenic pollution in coastal waters by laboratory and field experiments. HPPR's were assessed by simultaneous measurements of HP concentrations, cumulative solar UV irradiation and dissolved organic matter (DOM) fluorescence in the seawater samples at clean and polluted sites in the Mediterranean, Red and the Baltic Seas. The natural HP concentrations at all sites (8–100 nM) fall within the normal range recorded elsewhere, and follows a diurnal pattern. The polluted stations in the Mediterranean and Baltic Seas showed higher HPPR (3.2–16.6 nM m² W⁻¹ h⁻¹) than the clean stations, while in the Red Sea no significant differences were found because the station that was considered a priori polluted was actually rather clean (2–3 nM m² W⁻¹ h⁻¹). Laboratory experiments demonstrated that HPPR was positively linearly correlated to DOM fluorescence, however, this relationship was not found in the natural seawater samples examined in the field. The lack of relationship between HPPR and DOM in the field was attributed to enzymatic breakdown of HP as observed in dark decay experiments. HP dark decay rates were highest in polluted stations, probably due to larger bacterioplankton populations in these samples. Moreover, the HP dark decay rates were much lower in filtered than in non-filtered samples. Sun incubation of filtered (0.2 μm) seawater samples were performed to assess whether elimination of particles would yield higher HPPRs than in non-filtered samples. In the Baltic Sea (low UV irradiation) HPPR was higher in the filtered samples, while at sites with relatively high UV irradiation (Mediterranean and Red Seas), filtration of seawater did not stimulate HPPRs, probably due to UV-damage to planktonic microorganisms.     

Transitions to broad cells in a nonlinear thermal convection system

Abstract

This paper explores the properties of a two-dimensional, Boussinesq convection model with an ad hoc term in the buoyancy tendency equation that represents a positive external feedback process acting on the buoyancy fluctuations. Linear stability analyses and nonlinear integrations are presented for the case of constant heat flux boundary conditions. Although the large wavenumber modes grow the fastest from a state of rest, the nonlinear solutions progressively evolve to cells of small wavenumber. Applications to mesoscale cellular convection in the atmosphere are discussed.     

Diurnal momentum budget analysis of thermally induced slope winds

Summary  Data measured during the TRACT field campaign at various stations along a 7.5° steep and west-northwest facing slope of the Black Forest mountain range (Germany) are used to analyze the thermal structure and the momentum budget associated with thermally induced slope winds. Acceleration of the air close to the ground is found to be directed nearly vertically downward during the night and nearly vertically upward during the day, rather than parallel to the slope. This means that during the night the airflow is deflected by the slope surface in the down-slope direction, whereas during daytime stable stratification above the heated slope layer is required to establish up-slope flow parallel to the slope. The diurnal cycle of the momentum budget of the along-slope wind component near the surface is analyzed in detail with respect to the driving forces (buoyancy and pressure gradient force) and friction. It is found that a small imbalance between forcing and friction is responsible for the diurnal change in slope flow intensity. The along-slope components of the horizontal pressure gradient force and the buoyancy force are shown to have the same order of magnitude. This means that for small to moderate slope angles the pressure gradient force cannot be neglected as is done in some analytical slope wind models. The reaction time of the slope flow to changes in forcing is estimated to be in the range of 30 to 120 seconds, which confirms the empirically known fact that slope winds react very quickly. Received December 1, 1999 Revised June 13, 2000     

Evaluation of Modeled Spatially and Temporarily Highly Resolved Emission Inventories of Photosmog Precursors for the City of Augsburg: The Experiment EVA and Its Major Results

Emission inventories of NO_x, CO, and individual volatile organic compounds (VOC), highly resolved in space and time, belong to the most important input parameters for chemistry and transport models (CTM) used for ozone prediction. Because of the decisive influence of the input quality on the outcome of CTM simulations, the quality of emission inventories has to be assessed. This paper presents an experimental evaluation of the highly resolved emission inventories for the city of Augsburg. The emissions of the city, determined in March and October 1998 using mass balance and tracer techniques, and derived from the measured receptor concentration ratios, were compared with emissions modeled from an emission inventory. The modeled CO emissions were in agreement with the measured ones within the combined experimental and model uncertainties. More detailed CO emission model simulations suggest that the tendency of calculated CO emissions being smaller than the measured ones may be due to higher traffic activity in Augsburg. Modeled NO_x emissions were in agreement with the measured ones within the combined experimental and model uncertainties. Large deviations between modeled and measured values have been found for some individual NMHC compounds. The measured NMHC emission fingerprints were dominated by mobile sources. Substantial model predicted NMHC emissions from the solvent use could not be detected by measurements suggesting that they may not be correctly represented by the emission model.     

Calibration of electromagnetic seismographs by means of responses to release and shock tests

Summary The paper deals with the problems of fast determination of the magnification curve and of the partial constants of an electromagnetic seismograph by means of responses to release and shock tests, using a computer.     

Spatial and temporal variability of a coarse-sand anomaly on a sandy inner shelf,northeastern Gulf of Mexico

A 10-km² area of anomalously uniform coarse sand and low relief, in 30 m water depth off Panama City, Florida, USA, exists as a palimpsest hardbottom within the prevailing sand-wave system. Side-scan sonar observations over a ten-year period document the morphologic response of the anomaly to the bottom—wave—current interaction regime. The anomaly and surrounding sand waves remained fixed during this period. Ripples form within the anomaly in response to seasonal storms and decay during quiescent periods. Hurricane response includes minor realignment of sand waves, formation of megaripples, and deposition of a thin mud layer.