280 research outputs found
Suppression of the water ice and snow albedo feedback on planets orbiting red dwarf stars and the subsequent widening of the habitable zone
M-stars comprise 80% of main-sequence stars, and so their planetary systems
provide the best chance for finding habitable planets, i.e.: those with surface
liquid water. We have modelled the broadband albedo or reflectivity of water
ice and snow for simulated planetary surfaces orbiting two observed red dwarf
stars (or M-stars) using spectrally resolved data of the Earth's cryosphere.
The gradual reduction of the albedos of snow and ice at wavelengths greater
than 1 ?m, combined with M-stars emitting a significant fraction of their
radiation at these same longer wavelengths, mean that the albedos of ice and
snow on planets orbiting M-stars are much lower than their values on Earth. Our
results imply that the ice/snow albedo climate feedback is significantly weaker
for planets orbiting M-stars than for planets orbiting G-type stars such as the
Sun. In addition, planets with significant ice and snow cover will have
significantly higher surface temperatures for a given stellar flux if the
spectral variation of cryospheric albedo is considered, which in turn implies
that the outer edge of the habitable zone around M-stars may be 10-30% further
away from the parent star than previously thought.Comment: Final accepted by Astrobiology, 20 pages (double spaced), 3 figures
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Efficient dynamical downscaling of general circulation models using continuous data assimilation
Continuous data assimilation (CDA) is successfully implemented for the first
time for efficient dynamical downscaling of a global atmospheric reanalysis. A
comparison of the performance of CDA with the standard grid and spectral
nudging techniques for representing long- and short-scale features in the
downscaled fields using the Weather Research and Forecast (WRF) model is
further presented and analyzed. The WRF model is configured at 25km horizontal
resolution and is driven by 250km initial and boundary conditions from
NCEP/NCAR reanalysis fields. Downscaling experiments are performed over a
one-month period in January, 2016. The similarity metric is used to evaluate
the performance of the downscaling methods for large and small scales.
Similarity results are compared for the outputs of the WRF model with different
downscaling techniques, NCEP reanalysis, and Final Analysis. Both spectral
nudging and CDA describe better the small-scale features compared to grid
nudging. The choice of the wave number is critical in spectral nudging;
increasing the number of retained frequencies generally produced better
small-scale features, but only up to a certain threshold after which its
solution gradually became closer to grid nudging. CDA maintains the balance of
the large- and small-scale features similar to that of the best simulation
achieved by the best spectral nudging configuration, without the need of a
spectral decomposition. The different downscaled atmospheric variables,
including rainfall distribution, with CDA is most consistent with the
observations. The Brier skill score values further indicate that the added
value of CDA is distributed over the entire model domain. The overall results
clearly suggest that CDA provides an efficient new approach for dynamical
downscaling by maintaining better balance between the global model and the
downscaled fields
Environmental Prospects for the Next Century: Implications for Long-Term Policy and Research Strategies
This report examines environmental prospects for the twenty-first century, and then suggests some appropriate long-term management strategies and research priorities. A few current global trends (e.g., increasing concentrations of atmospheric trace gases, population, agricultural production) are practically irreversible over the next couple of decades due to inertias in the systems involved. However, there are bound to be nonlinearities, discontinuities, and surprises in the behavior of many environmental and socioeconomic systems. In fact, the main challenge for managers, policy analysts, and politicians is to develop strategies that are robust in response to these surprises, exploiting the opportunities as well as softening the shocks that may arise.
The main characteristics of such strategies are that they be adaptive, interdisciplinary, and cross-sectoral. As pointed out by Harvey Brooks (1986), we must avoid partial solutions that may be optimal for a particular sector or decade, but which are far from optimal for the biosphere as a whole over the long term
Changes in the Frontotemporal Cortex and Cognitive Correlates in First-Episode Psychosis
Background: Loss of cortical volume in frontotemporal regions has been reported in patients with schizophrenia and their relatives. Cortical area and thickness are determined by different genetic processes, and measuring these parameters separately may clarify disturbances in corticogenesis relevant to schizophrenia. Our study also explored clinical and cognitive correlates of these parameters.Methods: Thirty-seven patients with first-episode psychosis (34 schizophrenia, 3 schizoaffective disorder) and 38 healthy control subjects matched for age and sex took part in the study. Imaging was performed on an magnetic resonance imaging 1.5-T scanner. Area and thickness of the frontotemporal cortex were measured using a surface-based morphometry method (Freesurfer). All subjects underwent neuropsychologic testing that included measures of premorbid and current IQ, working and verbal memory, and executive function.Results: Reductions in cortical area, more marked in the temporal cortex, were present in patients. Overall frontotemporal cortical thickness did not differ between groups, although regional thinning of the right superior temporal region was observed in patients. There was a significant association of both premorbid IQ and IQ at disease onset with area, but not thickness, of the frontotemporal cortex, and working memory span was associated with area of the frontal cortex. These associations remained significant when only patients with schizophrenia were considered.Conclusions: Our results suggest an early disruption of corticogenesis in schizophrenia, although the effect of subsequent environmental factors cannot be excluded. In addition, cortical abnormalities are subject to regional variations and differ from those present in neurodegenerative diseases
Developing the knowledge base about carers and personalisation: contributions made by an exploration of carers’ perspectives on personal budgets and the carer–service user relationship
This qualitative study aimed to explore an under-researched issue within the emerging body of research about carers and personalisation – the carer–service user relationship. It was carried out across 11 English local authorities between 2011 and 2012 and focused on the impact of a change in the service user’s social care arrangements to a personal budget on this relationship. Using purposive sampling and explicit inclusion criteria, data were gathered through semi-structured in-depth interviews with 23 carers in long-term dyadic relationships with an adult in receipt of social care who had changed to a personal budget. The interviews explored carers’ perceptions of the carer–service user relationship before and after the advent of the personal budget and changes that had occurred. The findings were thematically analysed and reflect the fact that in addition to the effects of the move to a personal budget on the carer–service user relationship, the interviewees talked at length about a range of other effects of this move. Just over half of those interviewed felt that the personal budget had enhanced the carer–service user relationship. The other effects were both positive and negative. Three quarters reported positive outcomes, such as feeling happier, healthier and having more control over their lives. Although two thirds experienced negative feelings about having less involvement in the service user’s care, these feelings eased over time and if they had confidence in the quality of the care. Over half found administering the personal budget stressful. Further analysis of these findings showed the study contributes not only to existing knowledge about the carer–service user relationship within personalisation but also to knowledge about the effects of personalisation on carers more generally. It therefore simultaneously develops the emergent knowledge base about carers and personalisation. Recommendations based on this analysis are made about future practice and research
Cosmological constraints from galaxy clustering
In this manuscript I review the mathematics and physics that underpins recent
work using the clustering of galaxies to derive cosmological model constraints.
I start by describing the basic concepts, and gradually move on to some of the
complexities involved in analysing galaxy redshift surveys, focusing on the 2dF
Galaxy Redshift Survey (2dFGRS) and the Sloan Digital Sky survey (SDSS).
Difficulties within such an analysis, particularly dealing with redshift space
distortions and galaxy bias are highlighted. I then describe current
observations of the CMB fluctuation power spectrum, and consider the importance
of measurements of the clustering of galaxies in light of recent experiments.
Finally, I provide an example joint analysis of the latest CMB and large-scale
structure data, leading to a set of parameter constraints.Comment: 30 pages, 13 figures. Lecture given at Third Aegean Summer School,
The invisible universe: Dark matter and Dark energ
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