3,976 research outputs found
Land-atmosphere interactions in Southwest Western Australia
No full textThe Southwest of Western Australia (SWWA) is a region of extensive land cover change with an estimated 13 million hectares of native vegetation cleared since European settlement. Whilst previous studies have suggested meteorological and climatological implications of this change in land use, no studies have explicitly focussed on the detailed mechanisms behind the impacts of land-cover change on individual meteorological phenomena. This thesis seeks to identify the physical mechanisms inducing changes within the atmosphere by using the Regional Atmospheric Modeling System (RAMS V6.0) to simulate the impact of land use change on meteorological phenomena at different scales and evaluate these model results against high resolution atmospheric soundings, station observations, and gridded rainfall analyses where appropriate. Sensitivity tests show that land-cover change results in an increase in low-level atmospheric moisture advection associated with the southern sea-breeze due to a reduction in surface roughness. It also results in a decrease in convective precipitation associated with cold-fronts and convective clouds associated with the surface heat trough, due to an increase in wind speed, and a decrease in turbulent kinetic energy and vertically integrated moisture convergence within the PBL. Large-eddy simulations further highlight the role of land-cover change and soil moisture, as well as the contributions of surface versus entrainment fluxes on the growth of the PBL and development of convective clouds. These results are discussed within the broader context of the meteorology of the region
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No full textHere is a curious book. Its title-page declares "The Artist's Book of Fables" but its pre-title-page has "Fables, Original and Selected, with a Memoir of the Author." After that title-page, it is identical with "Fables, Original and Selected" as in our copy printed by John Murray in 1833. There is again an AI at the front and an index of engravings and engravers at the back. I found that copy twenty years ago. I had found an inferior copy twenty-two years before that. At that time, I noted Aesopic fables here including "Stone Broth" and "The Mouse and the Oyster."This is a hardbound book (hard cover)James Northcote, R.A
Turbulent entrainment in a shearless mixing layer at the edge of a cloud
No full textThree-dimensional direct numerical simulations which combine the Eulerian description of temperature, vapor content and velocity with a Lagrangian ensemble of cloud water droplets are used to study the turbulent entrainment and subsequent mixing of clear air with a cloudy air filament. The study is conducted in a shearless mixing layer setup which is adjusted to realistic conditions at a cumulus cloud boundary. The magnitude of turbulent velocity fluctuations in- and outside the cloud can be varied independently. We find that the evolution of the cloud water droplet ensemble depends slightly only on the contrast of turbulent velocity fluctuations in- and outside the cloud filament. The buoyancy feedback on the flow via the evaporating droplets causes a transient amplification of all fluctuations before the turbulence eventually decays. We study the evolution of the probability density functions of droplet size as well as of supersaturation, temperature and vorticity at the droplet positions
Flyleaf of The Village Politicians, signed by author and publisher R.A. Parsons, and printed by Guardian Ltd.
No full textNewIntroduction. Flyleaf of the The Village Politicans by R.A. Parsons and printed by Guardian Ltd.DA vol. 15 no.
Non-Linear Time Series Analysis of Deep Groundwater Levels: An application to the Veluwe
No full textThe objective of this study is to improve the simulation of deep groundwater levels by time se- ries models with pre-defined impulse response functions. This is attempted by adding a conceptual non-linear root zone model to simulate the recharge series to the model and by testing the use of a separate response function for the percolation zone. Three root zone models are developed based on two different recharge mechanisms: preferential flow, percolation, and a combination of the two. The performance of these models is compared to a linear model that is commonly used in time se- ries models to simulate the recharge. The approach is applied to groundwater level measurements in the Veluwe, a largely forested area in the Netherlands characterized by thick unsaturated zones. The effect of groundwater extractions and land reclamations is added to the model to further im- prove the simulation of the groundwater levels. The models are tested on three observations wells with increasing thickness of the unsaturated zone, varying from 7 m to 29 m to 49 m. The results show that model performance is improved by the implementation of a non-linear root zone model, particularly in simulating the peaks and lows in the groundwater levels. The recharge fluxes simulated by the non-linear models show different patterns that are physically more realistic than those simulated by the linear model. It is shown that different recharge series result in simulated groundwater levels that are very similar. This is a clear example of equifinality and it is recommended to introduce new sources of information to validate the modelled processes (e.g., water content measurements of the percolation zone or actual evaporation data). For the shallow well, the models with a single response function are selected as the best. The largest improvements for the deeper groundwater levels are obtained by the addition of a separate response for the percolation zone. For example, the average deviation from the observed ground- water levels decreased 0.18 m to 0.08 m for the deepest observation well by applying the separate response function. The models with an additional response function were better at simulating the estimated time to peak, the time it takes a recharge pulse to cause a peak in the groundwater levels. The time to peak is introduced in this research as a qualitative indicator to validate the modelled processes. The simulated responses indicate that the groundwater levels respond very quickly to water that leaves the root zone, even though the percolation zone is tens of metres thick. For each of the observations wells it is investigated if adding the effect of groundwater extrac- tions or land reclamations of Flevoland to the models improves the simulation of the groundwater levels. For the shallow well it is concluded that either the effect of land reclamations or groundwater extractions needs to be taken into account. Since these two stresses are correlated, it is concluded that only one of these should be taken into account when no further information is available to con- strain the models. For the medium deep well, the additional stresses did not significantly improve model performance and it is concluded that they do not have to be taken into account for this well. For the deep well, model performance is improved by both stresses. The largest improvements are observed when the effect of groundwater extractions is considered in the model. For implemen- tation of these stresses, the entire simulation period should be used for calibration, or constraints have to be implemented to obtain realistic results.Water ResourcesWater ManagementCivil Engineering and Geoscience
Genetics of ANCA-Associated Vasculitis
No full textANCA-associated vasculitis (AAV) is a group of disorders that is caused by inflammation affecting small blood vessels. AAV includes microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA) renamed from Wegener’s granulomatosis, and eosinophilic granulomatosis with polyangiitis (EGPA), renamed from Churg-Strauss syndrome. AAV can be considered a complex disease; in fact, both genetic and environmental factors are involved in its susceptibility. To improve the understanding of the disease, the genetic component has been extensively studied by candidate association studies and genome-wide association studies. Most of the identified genetic AAV risk factors are common variants, which still needs further investigation to clarify their importance. In this chapter, we discuss the results of genetic studies in AAV. We also present novel approaches to identifying the causal variants in complex susceptibility loci and disease mechanisms. Finally, we discuss the limitations of current methods and the challenges that we still have to approach in order to translate genomic and epigenomic data into clinical practice
Chemicals from renewable biomass: A renaissance in carbohydrate chemistry
No full textThe conversion of sugars, derived from waste polysaccharide biomass, to commodity chemicals by fermentation or catalytic hydrogenation, oxidation or dehydration or combinations thereof are reviewed.Accepted Author ManuscriptBT/Biocatalysi
Clouds form preferentially over native vegetation
No full textThe replacement of native vegetation for agriculture leads to significant changes in land surface characteristics, such as albedo, surface roughness and canopy resistance. These land surface changes induce changes in the atmospheric boundary layer. It is shown that in Western Australia, this change in surface characteristics and in particular, the albedo, has reduced the occurrence of convective cloud formation through limiting the vertical development of the boundary layer
Does liquidity in the FX market depend on volatility?
No full textWe re-examine the relationship between exchange rates and order flow as proposed by Evans and Lyons (2002). Compared to their linear specification, we find that the response of exchange rates to order flow may depend on market historical volatility. If market historical volatility is high, a given order seems to have a lower price impact than in calmer periods. Overall, our simple threshold mechanism has the power to produce higher correlation coefficients.exchange rate dynamics
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