Interaction of internal waves with a horizontally inhomogeneous density field area overlying a ridge

In the context of the general linear theory, we consider the propagation of an internal tide across a frontal zone overyling an oceanic ridge. For a uniformly stratified ocean, the solution was derived using Riemann's technique. The dependences of the generated internal wave amplitudes on the stratification parameters and bottom topography were determined. We have found that wave disturbances of high intensity inside and in the neighbourhood of the ridge may be concentrated in raytype areas. An increase of the horizontal density gradient in the frontal zone results in a perceptible deformation of these areas.Translated by Vladimir A. Puchkin.     

Atmospheric temperature sounding with the Fourier spectrometer

Preliminary results of a space experiment using the IKFS-2 infrared sounder (Meteor-M2 satellite) showed high-quality of measurements of spectra of the outgoing thermal radiation of the atmosphere–surface system and the adequacy of developed IR radiation atmospheric models in the 15-μm carbon gas absorption band used to recover the vertical profiles of the atmospheric temperature. Outgoing radiation spectra measured by IKFS-2 instruments make it possible to restore vertical temperature profiles with errors close to 1K in most of the 0–30 km high-altitude region, except for the lower troposphere and altitudes above 30 km, where these errors are close to 2–3K.     

Are droughts predictable?

From a study of rainfall series at several locations, it is shown that approximate but meaningful predictions of drought-prone intervals are possible only for regions where the rainfall series have prominent periodicities (of large amplitudes) in the long periodicity region (about 10 yr or more), provided the patterns do not change abruptly and drastically. Also, rainfall for individual years cannot be predicted accurately.     

Calculation of free seepage from watercourses with curvilinear profiles

A strict hydromechanical solution is given to the problem of free seepage from watercourses (rivers, canals, water bodies, industrial and agricultural ponds) for a family of smooth and complex curvilinear profiles with the use of conformal mappings and with the representation of the flow domain as the basis of the water-course profile in the Zhukovski complex domain. All necessary parameters of the flow are determined, including the outline of the curvilinear profile of the watercourse, depression curves and constant pressure lines (isobars), seepage flow, etc. For the particular case of a circular base of the watercourse profile, the results of obtained solution coincide with the known exact solutions derived by V.V. Vedernikov and N.N. Pavlovskii. Specific numerical examples of calculations for watercourses with different relative widths are given.     

Behaviour of brick infill walls strengthened with expanded steel plates

The present study was dedicated to investigate an effective, economical and convenient method for strengthening brick infill walls, i.e. the use of externally-bonded expanded steel plates. A total of 30 plastered wall assemblies were tested under monotonic diagonal loading to investigate the contribution of these plates to the load capacities, ductilities and rigidities of brick walls. The plate thickness, bolt spacing and location of the plates in the wall were the parameters of the test program. The experiments indicated that application of the plates on the outermost fine plaster layer significantly improves the diagonal load–deflection behaviour of infill walls and reducing the bolt spacing provides the strengthened walls with higher load capacity values. An analytical expression was developed for estimating the diagonal load capacities of plated brick walls. The analytical load estimates were found to be in close agreement with the experimental values.     

Geochemical Characteristics of Gold Polymetallic Deposits as Exemplified by the Laozuoshan Deposit,Heilong jiang,China

From the studies of ore deposit geologic settings,sulfur isotopes,lead isotopes,carbon isotopes and oxygen isotopes,fluid inclusions and petrochemistry in this paper,the authors have drawn a conclusion that the ore-forming hydrothermal solutions are the high-temperature magmatic hydrothermal solutions for the gold ore deposit,and at the same time,the involvemety of crustal materials can not be ruled out .It is the first time that the authors have proposed that the Laozuoshan gold-ploymetallic ore deposit in Heilongjiang Province was formed in the calc-alkaline series environment at the margin of an active continent.     

Distribution characteristics of Geo-hazards in Ganxi Valley after the Wenchuan earthquake

A devastating earthquake of Ms 8.0 struck the Wenchuan area on May 12, 2008. The quake triggered numerous landslides and avalanches in Ganxi Valley. Aerial photo interpretation indicates that the landslides and avalanches, presently in a stable state, are concentrated in 91 subregions of the valley, occupying 10.42 km², about 29% of the valley area. Some laws have been found on the gradient, aspect, elevation, distance of rupture, and formation lithology of geo-hazards in Ganxi Valley: (1) They are mainly situated on slopes between 30° and 50° and increase in number with increasing slope; (2) Failures are mainly in a southerly direction; and most occurred between 1,000 and 1,600 m, especially between 1,000 and 1,400 m; (3) Most are within 2,000 m of the Beichuan fault or within 1,000 m of other major faults; (4) most failures occurred from the T₁f + t formation in the study area. The geo-hazards status quo of Ganxi Valley provides foundation for the scheme of hazard reducing in the future.     

Natural and anthropogenic aquatic environmental changes reconstructed by paleolimnological analyses in Lake Kitaura,central Japan

In order to assess the recent anthropogenic environmental changes in Lake Kitaura, central Japan, changes during the past few centuries were reconstructed from results of radiometric and tephrochlonological age determination, magnetic susceptibility measurements, total organic carbon analyses, total nitrogen analyses and fossil diatom analyses on a sediment core from the lake. A total of six major and sub-zones are recognized according to the diatom fossil assemblages, and we discuss aquatic environmental change in Lake Kitaura mainly based on these diatom assemblage change. Zone Ia and Zone Ib (older than AD 1707) are marine to brackish. In Zone IIa (AD␣1707–AD 1836), most of the brackish diatoms disappeared, and were replaced by freshwater species indicating a decrease in salinity. We interpret the salinity decrease in Zone I–IIa as a sea-level fall during the Little Ice Age. The salinity of the lake decreased to near freshwater conditions in Zone IIb (AD 1836–AD 1970), which could arise from alteration in River Tone or development of a sandspit in the mouth of River Tone in addition to sea-level change. In Zone IIIa (AD 1970–AD 1987), the diatom assemblage indicates a freshwater environment, and sedimentation rates increase rapidly. These changes reflect sedimentary environment change and an ecosystem transition due to the construction of the tide gate. In Zone IIIb (AD 1987–AD 2002), the diatom flux (valves cm⁻² y⁻¹) increased and species composition changed. The changes in Zone IIIb show a good agreement with limnological monitoring data gathered from the lake. These paleolimnological data suggest that the recent human-induced changes of the aquatic environment of the lake after the 1970s exceed rates during the period concerned in this study.     

Assessing groundwater storage changes in the Nubian aquifer using GRACE data

Gravity Recovery and Climate Experiment (GRACE) level two (L2) data is used in estimating the groundwater storage changes (GWSC) in the Nubian Sandstone Aquifer System (NSAS). This set of data consists of spherical harmonics coefficients with specific degree and order. The GRACE data is de-correlated using a sixth degree polynomial in order to reduce the effect of the noise error resulting from the correlation between the spherical harmonics coefficients with the same degree parity. The GRACE estimates of GWSC are smoothed using Gaussian filter with half width of 1000 km. This half width is chosen in order to maximize the correlation between the GRACE estimates of GWSC and previous modeling results of the NSAS. The loss in groundwater storage occurring in each of the four countries sharing the NSAS is calculated to assess the sustainability of using the NSAS as a water resource in each country. The overarching finding in this study is that NSAS is losing its groundwater storage at a very high rate. Also, it is found that Egypt is the fastest in losing its groundwater storage from the NSAS. This loss of groundwater storage in Egypt may not necessarily be resulting from in-country extractions because of the trans-boundary nature of this aquifer. The GRACE-based estimates are found to be close to available data and previous modeling results of the NSAS.