Comparison of trends in stream water quality

A method is described for assessing the strength of evidence for differences in the trends in chemical concentrations in stream water between catchments. A smoothing spline technique is used to model changes in water quality as a result of changes in flow rates, seasonal effects and an underlying trend. The method involves fitting the model twice, once with the underlying trends constrained to be identical for each river and once with the trends unconstrained. Statistical properties are assessed by simulation methods that allow for the autocorrelation in the residuals from the unconstrained fit. The method is applied to data from two streams in the Balquhidder catchments in the Highlands of Scotland and to data from the Dee, Don and Ythan rivers in the north‐east of Scotland. Copyright © 2003 John Wiley & Sons, Ltd.     

Observations of the Ushant tidal front in September 2007

The Ushant tidal front is the dominant feature of the summer season hydrological structure of the Iroise Sea. It separates tidally mixed coastal waters from thermally stratified open Celtic Sea waters. This article reports on observations made in September 2007 during two short cruises that took place aboard R/V “Côtes de la Manche”, and gives a general account of the physical structure of the front along one cross-frontal transect. The data set comprises data from a 4 month ADCP mooring, short CTD/fluorescence/nutrients transects, Lagrangian drifter trajectories, and HF radar surface current measurements. One finding is that the surface and bottom fronts, being affected by different dynamical influences, are not necessarily coincident in the vertical. This entails that the opposite density gradients located above and below the thermocline depth do not necessarily compensate, and can each be associated with a significant surface geostrophic expression. A second finding is that mixing effects bear a very strong influence on the thermal structure of the warm-water intrusions associated with frontal cyclonic eddies of the kind described by Pingree [1978. Cyclonic eddies and cross-frontal mixing. Journal of the Marine Biological Association of the United Kingdom 58 (4), 955–963].     

Coseismic and other short-term strain changes recorded with Sacks-Evertson strainmeters in a deep mine, South Africa

Summary. During 1977 March and April, three Sacks-Evertson borehole dilatometers were installed at the ends of boreholes drilled into the sidewall of an experimental tunnel at a depth of 3.1 km in the ERPM gold mine near Johannesburg. In the following year coseismic strain changes ranging from 5 ± 10⁻¹⁰ to values exceeding 5 ± 10⁻⁶ were recorded for hundreds of mine tremors in the magnitude range -1 to 3.7 and at hypocentral distances of 50 m to about 2 km. Hypocentral coordinates and magnitudes were determined from seismograms recorded from an underground array of geophones. Amplitudes and polarities of the coseismic strain steps are generally in excellent agreement with theoretical expectations based on point-source dislocation theory; specifically, the strain steps are proportional to the seismic moment divided by the cube of hypocentral distance. At a strain level of 5 ± 10⁻⁹ or greater the tremors do not appear to be preceded by any short-term indications of instability even for tremors producing coseismic steps greater than 5 ± 10⁻⁶ and for which the strainmeters were within a source radius of the hypocentre. Continuous strain changes observed at the times when the mine excavation, at a distance of about 100 m, is extended are in good agreement with calculated changes based on the theory of elasticity. A similar calculation is consistent with post-seismic strain changes observed to follow some of the closer tremors. These post-seismic strains show a logarithmic dependence on time following the tremor and appear to be due to the interaction of a tremor with the adjacent mine excavation rather than to deformation within the actual seismic source region.     

On the impact of cloudiness on the characteristics of nocturnal downslope flows

The effects of cloud cover amount and the height of cloud base on nighttime thermally induced downslope flow were investigated using analytical and numerical model approaches. The conclusions obtained with the analytical and the numerical model evaluations agreed. It was concluded that, (i) as cloud cover increases and/or the height of cloud base decreases, the depth and the intensity of nighttime thermally-induced downslope flows may decrease by a factor reaching one sixth and one tenth, respectively, in the case of overcast low cloud; (ii) when skies suddenly cloud over around midnight, the development of the downslope flow is altered in different ways: a reduction in intensity; or a cessation of further development, depending on the fraction of cloud coverage, and (iii) with a sudden clearing of overcast low cloud around midnight, the depth and the intensity of the downslope flow increases significantly.On leave from the Institute of Atmospheric Physics, Academia Sinica, Beijing, China.On leave from CSIRO, Division of Atmospheric Research, Private Bag No. 1, Mordialloc, Victoria 3195, Australia.     

On the relationship between historical land‐use change and water availability: the case of the lower Tarim River region in northwestern China

Natural ecosystems in the region of the lower Tarim River in northwestern China strongly deteriorated since the 1950s due to an expanding desertification. As a result, the downstream Tarim River reaches became permanently dry land. This historical evolution in land‐use change is typically the result of the anthropogenic impact on natural ecosystems. On the basis of a spatially distributed hydrological catchment model bidirectionally linked with a fully hydrodynamic MIKE11 river model, land‐use changes characterized by historical changes in leaf area index (LAI) of vegetation, as well as the evolution of irrigated surface areas, can be causally related to changes in water resources (groundwater storage and surface water resources). An increased surface area of irrigated (agricultural) land, together with a majority of inefficient irrigation methods, did lead to a strong increase of water resources consumption of the farmlands located in the upper Tarim River area. Evidently, this evolution influenced available water resources downstream in the Tarim basin. As a result, farmland has been gradually relocated to the upstream regions. This has led to reduced flows from the upper Tarim stream, which subsequently accelerated the dropping of the groundwater level downstream in the basin. This study moreover demonstrates that land surface biomass changes (cumulative LAI) along the lower Tarim River are strongly related to the changes in groundwater storage. Copyright © 2012 John Wiley & Sons, Ltd.     

Magnetic field of the solar wind

Relationship between the geoefficiency of the solar flares as well as of the active regions passing the central meridian of the Sun and the configuration of the large scale solar magnetic field is studied.It is shown that if the tangential component of the large scale magnetic field at the active region or at the flare region is directed southwards, that region and that flare produce geomagnetic storm. In case when the tangential magnetic field is directed northward, the active region and the flares occurring at that region do not cause any geomagnetic disturbance.An index of the geoefficiency of the solar flares and of the active regions is proposed.     

The peaks and gaps in the redshift distributions of active galactic nuclei and quasars

The distributionsf(z) of the redshifts for active galaxies (Seyfert galaxies, radio galaxies, and quasars) have been studied. Some statistically-significant maxima and minima are observed in the distributionsf(z) for these objects. The significance of peaks and gaps increases for the brighter objects, for which the samples are more complete. The clustering of the Seyfert galaxies is significantly different from that of the nearby normal galaxies. The distributionf(z) for the radio galaxies is similar to the analogous distribution for the galaxy clusters. Three of the five peaks in the distributionf(z) for the radio quasars may be caused by the selection effects. Two peaks within the intervalsz (0.5, 0.7) and (1.0, 1.1) are probably real. The corresponding scales of the QSO clustering along the line-of-sight are about 100h ^–1 Mpc (h is the Hubble constant in the units of 75 km s^–1 Mpc^–1). The possibility of some global quasi-periodical cycles for the processes of activity is discussed. The period of a cycle for the Seyfert and radio galaxies is about 1×10⁸ years that corresponds to the distances of about 30h ^–1 Mpc between the shells.     

Comparative Analysis of “Exact” and “Approximate” Methods for Estimating the Absolute and Relative Elements of Detached Close Binary Systems

In this paper the star characteristics (luminosities, spectra, masses, absolute and relative radii of the components, mass ratio, major semiaxis, and orbital inclination) of close binary systems (CBS) with detached components are compared element-by-element. Svechnikov and Perevozkina's Catalog of the orbital elements, masses, and luminosities of pre-main sequence-type eclipsing variable stars with known photometric and spectroscopic elements and Svechnikov and Kuznetsova's Catalog of approximate photometric and absolute elements of eclipsing variable stars are used as initial data. The orbital elements contained in the first catalog are determined from solutions of the known photometric light curves and the known radial velocity curves, while the orbital elements for the second catalog were estimated using data from the General Catalog of Variable Stars (GCVS) IV employing approximate statistical relationships such as mass-radius, mass-luminosity, and mass-spectrum, along with the dependence of the orbital inclination on the depth of the principal minimum and others. Possible reasons for discrepancies among the compared quantities are discussed.