Limits on the chirality of interstellar and intergalactic space

We raise the question of whether velocities of left and right circularly-polarized photons might be different (for reasons other than the well-known Faraday effect). Such a difference could manifest itself either in the time profiles of pulsed or bursting astronomical sources or in the rotation of the direction of polarization of linearly polarized radiation from them. The existing observations of pulsars, gamma ray bursters, and quasar jets are used to set limits to the difference in speed, between 10^-17and 10^-32     

Evaluation of TMPA 3B42 Precipitation Estimates during the Passage of Tropical Cyclones over New Caledonia

A deficit in precipitation may impact greatly on soil moisture, snowpack, streamflow, groundwater and reservoir storage. Among the several approaches available to investigate this phenomenon, one of the most applied is the analysis of dry spells. In this study, a non-homogeneous Poisson model has been applied to a set of high-quality daily rainfall series, recorded in southern Italy (Calabria region) during the period 1981–2010, for the stochastic analysis of dry spells. Firstly, some statistical details of the Poisson models were presented. Then, the proposed model has been applied to the analysis of long dry spells. In particular, a Monte Carlo technique was performed to reproduce the characteristics of the process. As a result, the main characteristics of the long dry spells have shown patterns clearly related to some geographical features of the study area, such as elevation and latitude. The results obtained from the stochastic modelling of the long dry spells proved that the proposed model is useful for the probability evaluation of drought, thus improving environmental planning and management.     

The Effect of the Bistatic Scattering Angle on the High-Frequency Radar Cross Sections of the Ocean Surface

High-frequency (HF) bistatic Doppler cross sections of the ocean surface are examined with respect to their dependency on the bistatic angle. Previously derived results which incorporate a pulsed dipole source and two orders of scatter are considered. It is trivially seen that the first-order result has a linear dependence on the cosine of the bistatic angle. The second-order echo accounts for a double scatter of incident radiation from first-order surface waves - the so-called electromagnetic term - and a single scatter from a second-order ocean wave. The latter, generally referred to as the second-order hydrodynamic term because it originates from coupling between first-order ocean waves, predominates the Doppler continuum in most regions of interest. The analysis presented here verifies that in addition to a cosine-dependent reduction in cross section magnitude with increasing bistatic angle, both components of the second-order scatter tend to zero under the condition of near-forward scatter for bistatic HF radar operation. Of course, this imposes practical limitations on the region over which a bistatically configured HF radar system may be used to remotely sense ocean surface parameters.     

The angular momentum-vs-mass relation and the distribution of mass ratios for visual binary systems

The investigation of the angular momentum vs mass relation for binary stars is completed with a study of the 847 systems contained in theFourth Catalog of Orbits of Visual Binary Stars. Because bothJ andM of a visual binary depend steeply on the distance to the system (5th and 3rd powers, respectively), and many of the distances are not well known, the study makes use of an auxiliary parameterR which is independent of distance and proportional toJM ^–5/3.R appears to be uncorrelated withM for the 789 systems for which both can be determined. The non-correlation implies thatJ M ^5/3, expected from Kepler's third law, provides a better fit to the visual binaries than doesJ M ², predicted by some more complex considerations.The distribution functionf(q=M ₂/M₁) of mass ratios for the visual binaries results as a byproduct of the investigation. It peaks extremely sharply towardq=1.0 (much more so than for spectroscopic binaries). Because most visual binaries are wide enough to consist of stars that condensed independently (and so that can be thought of as chosen at random from an initial mass function), one expects the realf(q) to rise toward low ratios. Observational selection against the discovery and study of systems with large magnitude differences between the components must be very large indeed to account for the discrepancy between expectation and observation. The alternative is a mechanism for formation of wide binaries that favours equal components. The distribution of mass ratios for eclipsing binaries is given in an appendix. It peaks strongly atq=0.6–0.75 and largely reflects processes of angular momentum, mass, and energy exchange between the stars in contact systems.     

A metamorphic perspective on foreland flexure during intraplate orogeny: evidence for the involvement of weak lithosphere

Constraining depth–temperature conditions of syn‐orogenic burial metamorphism of syn‐orogenic sediments in a foreland basin provides an innovative way to investigate the thermomechanical state of the lithosphere. In central Australia, major intraplate deformation resulted in 10 km of syn‐orogenic sedimentation in a basin approximately 70 km wide. The deep level of burial in the foreland of the intraplate orogen requires the involvement of weak lithosphere with an elastic thickness of ≤20 km. The profound flexural response of the foreland region indicates that major intraplate deformation in central Australia was localised into a region of dramatically weakened lithosphere.     

Holocene vegetation and climate changes from a peat pollen record of the forest – steppe ecotone,Southwest of Patagonia (Argentina)

Pollen analysis from a peat-bog sequence located at 50° 24′ S, 72° 42′ W in the Subantarctic forest – Patagonian steppe ecotone gives information about vegetation and climate changes in Southwestern Patagonia since the glacier retreat. After 11 000 cal yr BP a change from grass steppe to open Nothofagus forest indicates that climatic conditions became rapidly warmer. Development of a closed Nothofagus forest between 5800 and 3200 cal yr BP is interpreted as precipitation increase. During the late Holocene colder climate conditions prevail in response to Neoglacial events. After ca 3000 cal yr BP Nothofagus forest became opener, and after 800 cal yr BP grass steppe expanded. Changes in the forest-steppe ecotone composition as well as the ecotone longitudinal shifts suggest changes in temperature and precipitation. Present-day mean annual precipitation between 300 and 400 mm is associated with grass steppe, and 500–600 mm with a greater forest representation. During the last century, low presence of forest in the area may be related to European settlement and repeated flooding caused by periodic advances of Perito Moreno glacier.     

The role of sea ice in climatic variability: Theories and evidence 1

Abstract

The climatic role of sea ice is assessed in a survey of the recent literature. Theoretical or model‐based results are compared with existing evidence of ice‐atmosphere interactions over scales ranging from the local and regional to the hemispheric and global.

The evidence shows that sea‐ice fluctuations are meteorologically important locally, primarily through associations with air temperature. On the regional and hemispheric scales, atmospheric and sea‐ice fluctuations are correlated according to both observational evidence and model experiments. While the causal links have not been evaluated quantitatively, there is evidence that the stronger signal occurs in the response of the ice to the atmosphere. On the longer time‐scales, model experiments and qualitative arguments suggest that sea ice may play a major role in the climatic change. However, the results of large‐scale coupled model simulations contain deficiencies and must be viewed with caution pending more realistic treatments of sea‐ice dynamics, leads, ice thickness variations, and the areally‐integraled effects of the small‐scale features of sea ice.