Validation of OML,AERMOD/PRIME and MISKAM Using the Thompson Wind-Tunnel Dataset for Simple Stack-Building Configurations

A comprehensive dataset on dispersion behind rectangular buildings has been used to analyse the performance of two dispersion models in respect to their handling of building effects: the Danish OML model and the US AERMOD model with the PRIME building algorithm; additionally, the German MISKAM model has been assessed. OML and AERMOD are regulatory plume models with limited requirements in terms of input and computing resources, whereas MISKAM is a computational fluid dynamical model, and as such much more demanding. For most scenarios considered, the degree of misprediction in respect to the maximum concentrations is less than a factor of two for OML and AERMOD. However, in respect to the concentration at a specific location, especially in the near field, both models often result in larger mispredictions. MISKAM provides more accurate predictions.     

Late Quaternary glaciation history of Isla de los Estados,southeasternmost South America

Isla de los Estados is a mountainous island southeast of Tierra del Fuego, in southernmost South America. Its central and eastern parts have an alpine topography, transected by U-shaped valleys, small, partly over-deepened fjords, and a multitude of abandoned cirques, all associated with extensive former local glaciations. Traces of glacial erosion generally reach 400–450 m a.s.l., and above that trimline a distinct sharp-edged nunatak derived landscape is present. The westernmost part of the island has a lower, more subdued topography, reflecting its “softer” geology but possibly also over-running and erosion by mainland-derived ice streams. The present study concentrated on glacigenic sediment sequences exposed along coastal erosional cliffs. A combination of OSL and ¹⁴C datings show that these sediments mostly date from the latest (Wisconsinan/Weichselian) glacial cycle, i.e. from the last ca. 100 ka with the oldest (glaciolacustrine) deposits possibly as old as 90–80 ka. The upper parts of overlying tills, with associated lateral and terminal moraines from glaciers that expanded onto an eustatically exposed dry shelf north of the island, date from the last global glacial maximum (LGM). Radiocarbon ages of peat and lake sediments indicate that deglaciation began 17–16 cal ka BP.     

Using 87Sr/86Sr, δ18O and δ2H isotopes along with major chemical composition to assess groundwater salinization in lower Shire valley,Malawi

Groundwater resources in some parts of the lower section of Shire River valley, Malawi, are not useable for rural domestic water supply due to high salinity. In this study, a combined assessment of isotopic (⁸⁷Sr/⁸⁶Sr, δ¹⁸O and δ²H) and major ion composition was conducted in order to identify the hydro-geochemical evolution of the groundwater and thereby the causes of salinity. Three major end-members (representing fresh- and saline groundwater, and evaporated recharge) were identified based on major ion and isotopic composition. The saline groundwater is inferred to result from dissolution of evaporitic salts (halite) and the fresh groundwater shows influence of silicate weathering. Conservative mixing models show that brackish groundwater samples result from a three component mixture comprising the identified end-members. Hence their salinity is interpreted to result from mixing of fresh groundwater with evaporated recharge and saline groundwater. On the other hand, the groundwater with low TDS, found at some distance from areas of high salinity, is influenced by mixing of evaporated recharge and fresh groundwater only. Close to the Shire marshes, where there is shallow groundwater, composition of stable isotopes of water indicates that evaporation may also be an important factor.     

Determinants of corporate adaptation to climate change in winter tourism: An econometric analysis

While corporate adaptation strategies in response to climate change have been characterized, the determinants of adaptation have not been comprehensively analyzed. Knowledge of these determinants is particularly useful for policy makers to provide favorable conditions in support of corporate adaptation measures. Based on unique data from a survey of Swiss ski lift operators, this paper empirically examines such determinants at the business level. Our econometric analysis with linear regression and count data models finds a positive influence of the awareness of possible climate change effects on the scope of corporate adaptation. Surprisingly, no significant influence of the vulnerability to climate change effects on the scope of adaptation could be found. Finally, the dependency on the affected business and the ability to adapt influence the specific strategic directions of corporate adaptation.     

Nucleonic gamma-ray production in pulsar wind nebulae

Observations of the inner radian of the Galactic disk at very high energy (VHE) gamma-rays have revealed at least 16 new sources. Besides shell type super-nova remnants, pulsar wind nebulae (PWN) appear to be a dominant source population in the catalogue of VHE gamma-ray sources. Except for the Crab nebula, the newly discovered PWN are resolved at VHE gamma-rays to be spatially extended (5–20 pc). Currently, at least 3 middle aged (t>10 kyrs) PWN (Vela X, G18.0-0.7, and G313.3+0.6 in the “Kookaburra” region) and 1 young PWN MSH 15-52 (t=1.55 kyrs) have been identified to be VHE emitting PWN (sometimes called “TeV Plerions”). Two more candidate “TeV Plerions” have been identified and have been reported at this conference (Carrigan, These proceedings, in preparation). In this contribution, the gamma-ray emission from Vela X is explained by a nucleonic component in the pulsar wind. The measured broad band spectral energy distribution is compared with the expected X-ray emission from primary and secondary electrons. The observed X-ray emission and TeV emission from the three middle aged PWN are compared with each other.     

Managing organizational change in an international scientific network: A study of ICES reform processes

Organizations involved in the governance of natural resources are challenged to adjust to the call for more holistic management approaches. This often necessitates organizational change. Here change processes in the International Council for the Exploration of the Sea (ICES) during the years 1998–2009 are investigated using semi-structured interviews combined with observations and review of documents. Several organizational reforms were implemented during the time period studied. The major drivers were the need to improve efficiency and a striving for better integration between different components within the organization. The reform processes were driven forward by individuals who navigated between opportunities and constrains embedded in the network structure of ICES. This required good leadership and communication skills. Broad consultations were important to ensure support within the ICES community. By increasing the understanding of the dynamics of change in organizations, which operate at the science–policy interface developments in desired directions can be facilitated.     

Pre-Cambrian atmosphere:evidence from the Pre-Cambrian of Sweden

Sedimentary haematite ores of central Sweden give evidence of the existence of an oxidizing atmosphere about 2000 × 10⁶ years ago. This is not consistent with Rankama's conclusions from the unoxidized condition of a diorite conglomerate in Finland. Therefore a (later) Pre-Cambrian conglomerate in northern Sweden has been examined for comparison. Where it is made up of dioritic material no proofs of oxidation can be found, but where the material is mainly iron-ore pebbles, magnetite ore is found to have been completely oxidized to haematite (martite) before being embedded as pebbles in the conglomerate.     

Using the pseudospectral technique on curved grids for 2D acoustic forward modelling1

The Fourier pseudospectral method has been widely accepted for seismic forward modelling because of its high accuracy compared to other numerical techniques. Conventionally, the modelling is performed on Cartesian grids. This means that curved interfaces are represented in a ‘staircase fashion‘causing spurious diffractions. It is the aim of this work to eliminate these non-physical diffractions by using curved grids that generally follow the interfaces. A further advantage of using curved grids is that the local grid density can be adjusted according to the velocity of the individual layers, i.e. the overall grid density is not restricted by the lowest velocity in the subsurface. This means that considerable savings in computer storage can be obtained and thus larger computational models can be handled. One of the major problems in using the curved grid approach has been the generation of a suitable grid that fits all the interfaces. However, as a new approach, we adopt techniques originally developed for computational fluid dynamics (CFD) applications. This allows us to put the curved grid technique into a general framework, enabling the grid to follow all interfaces. In principle, a separate grid is generated for each geological layer, patching the grid lines across the interfaces to obtain a globally continuous grid (the so-called multiblock strategy). The curved grid is taken to constitute a generalised curvilinear coordinate system, where each grid line corresponds to a constant value of one of the curvilinear coordinates. That means that the forward modelling equations have to be written in curvilinear coordinates, resulting in additional terms in the equations. However, the subsurface geometry is much simpler in the curvilinear space. The advantages of the curved grid technique are demonstrated for the 2D acoustic wave equation. This includes a verification of the method against an analytic reference solution for wedge diffraction and a comparison with the pseudospectral method on Cartesian grids. The results demonstrate that high accuracies are obtained with few grid points and without extra computational costs as compared with Cartesian methods.     

Land degradation,natural resources and local knowledge in the sahel zone of Burkina Faso

This paper proposes a conceptual model that integrates physical and ecological aspects with human aspects of land degradation through a multidisciplinary approach. The model was applied at the local level in a case study in northern Burkina Faso. Assessments of the degradation of the vegetation cover from aerial photographs and a satellite image were analysed in the framework of the model. Another input to the model was results from interviews and field visits with peasants living in the area.The local knowledge of the physical symptoms of land degradation and of the physical variables, eg rainfall and wind, is very close to the scientific logic. However, people do not generally see the links between these variables and the symptoms. Likewise, they do not perceive land degradation to be influenced in any way by human actions. Instead, the cause of land degradation is attributed to God, Allah. Thus, an important field of intervention for governments and development agencies should be to make people aware of their role in land management.