Metrics for Improved Reanalyses in Polar Regions

Atmospheric reanalyses are widely used for a variety of scientific endeavors in the Arctic and Antarctic. Reanalyses are used as boundary conditions for a regional and process-based models, for climate model validation, and for diagnostic analysis of physical processes, weather and climatic events. However, reanalyses are typically global and often do not account for specific, regional considerations, such as for polar regions. In this work, we provide a brief evaluation of a prototype for a new GMAO reanalysis, which incorporates higher spatial resolution, an updated approach for data assimilation, and a revised atmospheric model. We identify differences in the representation of the Arctic atmosphere in comparison to recent reanalyses. Furthermore, we provide a forum for Arctic scientists to consider the future improvements for reanalyses, and seek feedback for the following questions: 1) What are important performance factors to consider in evaluating new reanalyses? 2) What physical processes should be incorporated into new reanalyses? 3) What spatio-temporal scales should be considered

Making BEASTies: dynamical formation of planetary systems around massive stars

Exoplanets display incredible diversity, from planetary system architectures around Sun-like stars that are very different to our Solar System, to planets orbiting post-main sequence stars or stellar remnants. Recently the B-star Exoplanet Abundance STudy (BEAST) reported the discovery of at least two super-Jovian planets orbiting massive stars in the Sco Cen OB association. Whilst such massive stars do have Keplerian discs, it is hard to envisage gas giant planets being able to form in such hostile environments. We use N-body simulations of star-forming regions to show that these systems can instead form from the capture of a free-floating planet, or the direct theft of a planet from one star to another, more massive star. We find that this occurs on average once in the first 10Myr of an association's evolution, and that the semimajor axes of the hitherto confirmed BEAST planets (290 and 556au) are more consistent with capture than theft. Our results lend further credence to the notion that planets on more distant (>100au) orbits may not be orbiting their parent star.Comment: 5 pages, 4 figures, published in MNRAS Letter

Neutron spectroscopy as a tool in catalytic science

Catalytic science currently has access to a range of advanced experimental methods for the study of molecular behaviour in chemical processes. Neutron spectroscopy, however, is uniquely placed to gain detailed insight into such systems, particularly through techniques such as vibrational spectroscopy with neutrons (INS) which gives access to vibrational modes unavailable to conventional spectroscopy techniques, and quasielastic neutron scattering (QENS) which studies molecular motion on a range of timescales. The present article illustrates the role of these techniques in advancing the field of catalysis. We first provide a brief introduction to the basic principles of the techniques, and then discuss their use in the study of three key catalytic systems: the behaviour of hydrocarbons confined in zeolite catalysts; the methanol-to-hydrocarbons process; and methane reforming. We demonstrate the importance of neutron spectroscopy in understanding established catalytic processes, but also consider its role in the design of future catalytic systems

The elimination of surface cross-hatch from relaxed, limited-area Si1 – xGex buffer layers

The influence of lateral dimensions on the relaxation and surface topography of linearly graded Si1 – xGex buffer layers has been investigated. A dramatic change in the relaxation mechanism has been observed for depositions on Si mesa pillars of lateral dimensions 10 µm and below. Misfit dislocations are able to extend unhindered and terminate at the edges of the growth zone, yielding a surface free of cross-hatch. For lateral dimensions in excess of 10 µm orthogonal misfit interactions occur and relaxation is dominated by the modified Frank–Read (MFR) mechanism. The stress fields associated with the MFR dislocation pile-ups result in a pronounced cross-hatch topography