Risk occurrences of damaging frosts during the growing season of vegetables in the Elbe River lowland,the Czech Republic

This study has, for the first time, analysed in detail the risk occurrences of the last spring frost, first fall frost and the length of the frost-free period during the growing season of vegetable crops at a high horizontal resolution of 10 km in the Elbe River lowland in the Czech Republic. The daily minimum air temperature from 116 grid points throughout the studied area for the period 1961–2011 was used. The daily values of minimum air temperature ranges of 0 to ?1.1 °C, ?1.2 to ?2.2 °C and below ?2.2 °C were considered to constitute mild, moderate and severe frost intensities, respectively. Firstly, the spatiotemporal variability of the date of the last spring frost, the date of the first fall frost and the length of the frost-free period in the Elbe River lowland is provided. Secondly, the estimation of the probability of a later date in the spring and an earlier date in the fall for various severe frost events and the length of the frost-free period is determined. Third, the changes in the timing of the last and first frosts of the three severities, as well as the length of the frost-free period, are evaluated. From 1961 to 2011, the Elbe River lowland has experienced a decrease in the number of frost days, while the length of the frost-free period between the last spring frost and the first fall frost has increased. The temporal evolution of the frost-free period anomalies displays two distinct periods: a shortening of the frost-free period in the 1960s and an intensified lengthening of the frost-free period since the 1980s. Whereas the latest spring frost has ended on an earlier date across the Elbe River lowland, the first frost date in the fall has generally been delayed to a later date. The dates of the last spring frost have advanced by ?0.21 days per year on average. The fall dates are delayed up to 0.18 days per year, whereas the frost-free period is lengthening by up to 0.39 days per year on average. However, regional frost series suggests that the frost-free period exhibits a large amount of inter-annual variability. In terms of the growth of field vegetables, a late spring frost remains a risk factor, but the degree of risk has decreased. There is a 25 % chance of the occurrence of dangerous spring frosts during the planting of field vegetables after 3rd May, but after 15th May, the risk is only 10 %.     

The magnetic anisotropy of basalts and its variations under oxidation of titanomagnetites

Summary Using four samples of basaltic rocks from the Bohemian Massif, Nos 201, 202, 206 and 218, the curves of rotational moments in a magnetic field of 4 × 10⁵ A/m were studied as a function of the degree of oxidation of titanomagnetites. The amplitudes of the individual harmonics were determined by harmonic analysis for samples oxidized to various degrees. It was found that the proportion of the harmonic A ₁ withsin increases with the degree of oxidation. Simultaneously, the anisotropy of the magnetic susceptibility changes in a field of 60 A/m and the structure changes from linearly parallel to plane parallel.     

Finite-difference modelling of magnetotelluric fields in two-dimensional anisotropic media

An algorithm for the numerical modelling of magnetotelluric fields in 2-D generally anisotropic block structures is presented. Electrical properties of the individual homogeneous blocks are described by an arbitrary symmetric and positive-definite conductivity tensor. The problem leads to a coupled system of partial differential equations for the strike-parallel components of the electromagnetic field. E _x, and H _x These equations are numerically approximated by the finite-difference (FD) method, making use of the integro-interpolation approach. As the magnetic component H _x, is constant in the non-conductive air, only equations for the electric mode are approximated within the air layer. The system of linear difference equations, resulting from the FD approximation, can be arranged in such a way that its matrix is symmetric and band-limited, and can be solved, for not too large models, by Gaussian elimination. The algorithm is applied to model situations which demonstrate some non-trivial phenomena caused by electrical anisotropy. In particular, the effect of 2-D anisotropy on the relation between magnetotelluric impedances and induction arrows is studied in detail.     

A possible rotation period for the minor planet 164 Eva

The minor planet 164 Eva passed through opposition on December 1, 1975 with a magnitude B_opp = 11.3 mag. Photoelectric observations at the Observatory of Torino, Italy, were carried out in two nights on Oct. 27/28 and Nov. 11, each with a run of about 3 hr. Two further successful photoelectric observations were carried out at the OHP, France, each with a run of about 6 hr. From all observed parts of the lightcurve a resulting synodic period of rotation of about 27.3 hr can be deduced, with a range of the total amplitude of at least Δm = 0.07 mag. With this period of 27.3 hr the minor planet 164 Eva is one more long period object, falling now between 654 Zelinda (H. J. Schober, 1975, Astron. Astrophys.44, 85–89) and 139 Juewa (J. Goguen et al., 1976, Icarus29, 137–142), at the high end in the histogram of the distribution of minor planet rotation periods.     

Iterative Spherical Downward Continuation Applied to Magnetic and Gravitational Data from Satellite

In the last few decades, satellites have acquired various potential data sets hundreds of kilometers above the Earth’s surface. Conventionally, these global magnetic and gravitational data sets are approximated by using spherical harmonics that allow straightforward work with both fields outside the Earth’s mass. In this article, we present an alternative approach for working with potential data in mass-free space given over a regular coordinate grid on a spherical surface. The algorithm is based on an iterative scheme and the Poisson integral equation for the sphere. With help from the Fourier transform, global potential (magnetic or gravitational) data can efficiently be continued from a mean orbital sphere down to a reference surface without using the spherical harmonics. This is illustrated both with simulated magnetic field data and with real data from the satellite gradiometry mission GOCE. In the case of simulated magnetic data and the downward continuation for 450 km, we have achieved a root mean square at the level of 0.05 nT, while it was <1 E (eotvos) for real GOCE data continued for 250 km. The crucial point is to apply the algorithm twice as a large part of noise can be removed from the input data.     

Magnetic and nuclear structure and thermal expansion of orthorhombic and monoclinic polymorphs of CoGeO3 pyroxene

CoGeO₃ was synthesized at 1,273 and 1,448 K using ceramic sintering techniques in the monoclinic and orthorhombic modification, respectively. The two compounds were analysed by magnetic susceptibility measurements and neutron diffraction in order to study magnetic ordering and spin structures at low temperature. The monoclinic form of CoGeO₃ has C2/c symmetry and orders magnetically below 36 K with a small negative paramagnetic Curie temperature θ _P = −4.6 (2) K. The magnetic structure can be described with k = (1, 0, 0) in the magnetic space group C2′/c′ having a ferromagnetic spin arrangement within the chains of M1 sites, but a dominating antiferromagnetic coupling between the chains. At the M1 sites the magnetic spins are aligned within the a–c plane forming an angle of 120° with the +a-axis and they are not parallel to the spins at M2. Here spins are also ferromagnetically coupled within, but antiferromagnetically coupled between the M1/M2 site bands. The orthorhombic phase of CoGeO₃ displays Pbca symmetry and transforms to an antiferromagnetically ordered state [θ _P = −18.6(2) K] below 33 K. The magnetic spin structure can be described with k = (0, 0, 0) in space group Pbca′ and it is similar to the one of the C2/c phase except that it is non-collinear in nature, i.e. there are components of the magnetic moment along all three crystallographic axes. Small magneto-elastic coupling is observed in the orthorhombic phase.     

Abrupt deglaciation on the northeastern Tibetan Plateau: evidence from Lake Qinghai

We inferred the climate history for Central Asia over the past 20,000 years, using sediments from core QH07, taken in the southeastern basin of Lake Qinghai, which lies at the northeastern margin of the Tibetan Plateau. Results from multiple environmental indicators are internally consistent and yield a clear late Pleistocene and Holocene climate record. Carbonate content and total organic carbon (TOC) in Lake Qinghai sediments are interpreted as indicators of the strength of the Asian summer monsoon. Warm and wet intervals, associated with increased monsoon strength, are indicated by increased carbonate and TOC content. During the glacial period (~20,000 to ~14,600 cal year BP), summer monsoon intensity remained low and relatively constant at Lake Qinghai, suggesting cool, dry, and relatively stable climate conditions. The inferred stable, cold, arid environment of the glacial maximum seems to persist through the Younger Dryas time period, and little or no evidence of a warm interval correlative with the Bølling–Allerød is found in the QH07 record. The transition between the late Pleistocene and the Holocene, about 11,500 cal year BP, was abrupt, more so than indicated by speleothems in eastern China. The Holocene (~11,500 cal year BP to present) was a time of enhanced summer monsoon strength and greater variability, indicating relatively wetter but more unstable climatic conditions than those of the late Pleistocene. The warmest, wettest part of the Holocene, marked by increased organic matter and carbonate contents, occurred from ~11,500 to ~9,000 cal year BP, consistent with maximum summer insolation contrast between 30°N and 15°N. A gradual reduction in precipitation (weakened summer monsoon) is inferred from decreased carbonate content through the course of the Holocene. We propose that changes in the contrast of summer insolation between 30°N and 15°N are the primary control on the Asian monsoon system over glacial/interglacial time scales. Secondary influences may include regional and global albedo changes attributable to ice-cover and vegetation shifts and sea level changes (distance from moisture source in Pacific Ocean). The abruptness of the change at the beginning of the Holocene, combined with an increase in variability, suggest a threshold for the arrival of monsoonal rainfall at the northeastern edge of the Tibetan Plateau.     

Прерывистое освещение поля зрения при методе соответствуюших высот и относительные уклонения отвеса в высоких татрах

To determine the relative deflections of the vertical from geodetic data and from astronomical measurements we used the method of equal altitudes, determining the time of passage by means of interrupted illumination of the field of view. The field of view of the telescope used (Zeiss Theo 010 and an astrolabe having an angle of 60°) was therefore supplied with five groups of seven horizontal fibres and during the passage of the two images the field of view was illuminated by a neon tube for a period of about 0·15 s every three seconds. The neon tube was connected either directly to an OMA 50 time signal by means of a transistor receiver or to a chronometer. The calculation was performed by means of relations (1) and (2). Apart from the corrections usually introduced, the personal-instrumental error (containing also a correction from the decimal equation) of the longitudeo _λ and the correctiona _η of the component η were also determined from the measurements. The correctionso _λ=?0·069s ando _η=?0·66″ also contain a correction from the decimal equation. Its value iso _λ ^′ =?0·030s for the longitude. The lago _λ?o _λ ^′ in reading the interpolation was ?0·039 s. The valueo _η=?0·66″ was introduced into the calculation of the vertical components η obtained from measurements in the High Tatras. The values of the corrections are given in Tab. 1. The method permits measurement of the passages of stars through the almucantar in the meridian. No conclusive proof was found for the impersonality (Tab. 1). The method was verified practically when determining the relative deflections of the vertical in the High Tatras for refining altitude measurements. The results are given in Tab. 2 and Fig. 2. The course of the quasigeoid profile in the Kriváňmeridian was also found (Fig. 3).     

The spatial distribution of the lignite qualitative parameters and variant estimates of coal reserves: the Czech Part of the Vienna Basin

The aim of this article is to inform about the spatial distribution of the lignite qualitative parameters and total lignite reserves in the Czech Part of the Vienna Basin—The South Moravian Lignite Coalfield (SMLC). The total reserves were estimated on the basis of several composed variant digital models of individual seams in four partial area of SMLC. Calculations of the reserves resulted from the identified spatial distribution of chemical-technological parameters obtained from the thousands analysis of samples taken from more than 4,000 exploration works. The basic model of the deposit was so-called geological model characterising genetic evolution of the deposit and defines the spatial positions of the coal seams. Subsequently developed variant economical models spatially define the selected areas by the quality of lignite expressed by the limits of ash yield. Based on the created models, it was found that in the past just 3–7 % (depending on the variant model) of the total lignite reserves SMLC had been extracted. The presented geological reserves are currently using the existing mining technologies only partially mineable.