Assessment of value added for surface marine wind speed obtained from two regional climate models

Hindcasts with reanalysis-driven regional climate models (RCMs) are a common tool to assess weather statistics (i.e., climate) and recent changes and trends. The capability of different state-of-the-art RCMs (with and without spectral nudging applied) to add value for surface marine wind speed in comparison to the reanalysis wind speed forcing is assessed by the comparison with observations in the eastern North Atlantic in 1998. Added value is elaborated on instantaneous wind speeds and their frequency distribution. The observations are discriminated into groups according to their proximity to land and assimilation status, meaning whether they are assimilated into the reanalysis or not. For instantaneous wind speeds RCMs do not show added value both in ‘‘open ocean’’ areas and the German Bight. However, in the English Channel, where local topography and associated local wind regimes become important, the regional models show an added value for instantaneous wind speeds. Concerning the wind speed distribution there is a clear indication for an added value of the RCMs in coastal regions, especially for higher wind speed percentiles, while in open-ocean areas no added value is found. In comparison to the unnudged simulation, the spectrally nudged simulations better represent both instantaneous wind speeds and their frequency distribution. These results hold independently of the measurements’ assimilation status. Strictly the findings of this study only hold for hindcast studies, the results may differ for other areas and years

The path to fusion power†

The promise, status and challenges of developing fusion power are outlined. The key physics and engineering principles are described and recent progress quantified. As the successful demonstration of 16 MW of fusion in 1997 in the Joint European Torus showed, fusion works. The central issue is therefore to make it work reliably and economically on the scale of a power station. We argue that to meet this challenge in 30 years we must follow the aggressive programme known as the ‘Fast Track to Fusion’. This programme is described in some detail

Nanoscale quantum dot infrared sensors with photonic crystal cavity

We report high performance infrared sensors that are based on intersubband transitions in nanoscale self-assembled quantum dots combined with a microcavity resonator made with a high-index-contrast two-dimensional photonic crystal. The addition of the photonic crystal cavity increases the photocurrent, conversion efficiency, and the signal to noise ratio (represented by the specific detectivity D*) by more than an order of magnitude. The conversion efficiency of the detector at Vb=–2.6 V increased from 7.5% for the control sample to 95% in the PhC detector. In principle, these photonic crystal resonators are technology agnostic and can be directly integrated into the manufacturing of present day infrared sensors using existing lithographic tools in the fabrication facility

A new concept in the design of the LHC beam dump

Recent Monte Carlo cascade simulations have shown that a reduction in the maximum of deposited energy density can be obtained by applying a uniform magnetic field over a front part of the graphite core of the LHC dump. This paper shows the effect of field strength on spatial distributions of absorbed energy and temperatures, and discusses problems to be solved when designing a suitable magnet

Further support for the alignment of cattle along magnetic field lines: reply to Hert et al.

Hert et al. (J Comp Physiol A, 2011) challenged one part of the study by Begall et al. (PNAS 105:13451–13455, 2008) claiming that they could not replicate the finding of preferential magnetic alignment of cattle recorded in aerial images of Google Earth. However, Hert and co-authors used a different statistical approach and applied the statistics on a sample partly unsuitable to examine magnetic alignment. About 50% of their data represent noise (resolution of the images is too poor to enable unambiguous measurement of the direction of body axes, pastures are on slopes, near settlements or high voltage power-lines, etc.). Moreover, the authors have selected for their analysis only ~ 40% of cattle that were present on the pastures analyzed. Here, we reanalyze all usable data and show that cattle significantly align their body axes in North–South direction on pastures analyzed by Hert and co-authors. This finding thus supports our previous study. In addition, we show by using aerial Google Earth images with good resolution, that the magnetic alignment is more pronounced in resting than in standing cattle

Thermal performance of planktonic ciliates differs between marine and freshwaters: A case study providing guidance for climate change studies

Predicting the performance of aquatic organisms in a future warmer climate depends critically on understanding how current temperature regimes affect the organisms’ growth rates. Using a meta-analysis for published experimental data, we calculated the activation energy (Ea) to parameterize the thermal sensitivity of marine and freshwater ciliates, major players in marine and freshwater food webs. We hypothesized that their growth rates increase with temperature but that ciliates dwelling in the immense, thermally stable ocean are closely adapted to their ambient temperature and have lower Ea than ciliates living in smaller, thermally more variable freshwater environments. The Ea was in the range known from other taxa but significantly lower for marine ciliates (0.390 ± 0.105 eV) than for freshwater ciliates (0.633 ± 0.060 eV), supporting our hypothesis. Accordingly, models aiming to predict the ciliate response to increasing water temperature should apply the environment-specific activation energies provided in this study

On the dynamics of coupled S=1/2 antiferromagnetic zig-zag chains

We investigate the elementary excitations of quasi one-dimensional S=1/2 systems built up from zig-zag chains with general isotropic exchange constants, using exact (Lanczos) diagonalization for 24 spins and series expansions starting from the decoupled dimer limit. For the ideal one-dimensional zig-zag chain we discuss the systematic variation of the basic (magnon) triplet excitation with general exchange parameters and in particular the presence of practically flat dispersions in certain regions of phase space. We extend the dimer expansion in order to include the effects of 3D interactions on the spectra of weakly interacting zig-zag chains. In an application to KCuCl_3 we show that this approach allows to determine the exchange interactions between individual pairs of spins from the spectra as determined in recent neutron scattering experiments.Comment: 8 pages, 9 figures; some changes, figure added; final versio

Exploring high-end climate change scenarios for flood protection of the Netherlands

This international scientific assessment has been carried out at the request of the Dutch Delta Committee. The "Deltacommissie" requested that the assessment explore the high-end climate change scenarios for flood protection of the Netherlands. It is a state-of–the art scientific assessment of the upper bound values and longer term projections (for sea level rise up to 2200) of climate induced sea level rise, changing storm surge conditions and peak discharge of river Rhine. It comprises a review of recent studies, model projections and expert opinions of more than 20 leading climate scientists from different countries around the North Sea, Australia and the US