The inclusion of surface synoptic data in very short range predictions of convective events

Summary Predictor vectors, including upper air as well as surface data, were used for categorical forecasting convective events over a subregion of the Czech territory, and the effect of including surface variables in the predictor vector was examined. While upper air data were considered as Perfect Prognosis, the surface data were successively included according to the time of their origin. The forecasting technique was based on linear multiple regression with learning, and the accuracy of the forecast was measured by the Critical Success Index. The input data from the three May-September periods in 1989–91 were used, and the first year served as the learning set. The aerological data from TEMP 12 UTC, simulating Perfect Prognosis, were the source of the upper air predictors. The performance of all, upper air, surface and combined, predictors were evaluated and compared. It turned out that the improvement of prediction accuracy due to the inclusion of surface variables was not negligible. Significant improvements were made in the forecasts of thunderstorm occurrence between 18 and 24 UTC.     

Palaeomagnetism and palaeogeography of Mongolia from the Carboniferous to the Cretaceous—final report

The present study summarizes the results of palaeomagnetic investigations of Carboniferous to Cretaceous rocks with respect to global-tectonic interpretations of Eurasia. Normal and reverse directions of stable remanence components were found for the Carboniferous to Cretaceous rocks within single outcrops, sometimes even within individual samples. Triassic, Permian and Carboniferous pole positions for Mongolia are strikingly different from those of the Siberian platform. The conclusion about the different palaeogeographical development of Mongolia with respect to the Siberian platform is well seen from differences in palaeolatitudes (up to 50°) and palaeorotations (up to 150°). The apparent polar wander paths for Mongolia and the north China block are almost identical since the Carboniferous. This way, palaeomagnetic and palaeogeographical data are contributing to the global-tectonics model of the regions under study. During the Carboniferous, Permian and Triassic, the regions of Mongolia investigated were not part of Eurasia. Together with the north China block, they show a palaeogeographical affinity with the Pacific Plate.     

On the solution of the boundary problem of the potential theory by means of the vertical derivative of the gravity anomaly

Summary The boundary problem of the potential theory is treated for the case in which the values of the vertical derivative of the gravity anomaly are known. There boundary conditions are derived and alternatives are also treated.Dedicated to RNDr. Jan Pícha, CSc., on his 60th Birthday     

A palaeomagnetic and petromagnetic study of Upper-Carboniferous,Permian and Triassic sediments,NW Bulgaria

Summary In order to obtain basic palaeomagnetic data on Upper Carboniferous, Permian and Triassic sediments collected from the NW Bulgaria, laboratory stability tests were extended from A.C. and thermal treatments to studies of mineral phase changes and to investigations of changes of magnetic anisotropy during laboratory procedures. Laboratory criteria were found which permitted to distinguish samples suitable for palaeomagnetic analyses from those representing rocks totally or almost totally chemically reworked during their history. Palaeomagnetic directions and pole positions derived from Stephanian, Lower Permian and Triassic rocks from the southern margin of the Moesian Platform are compatible with the values obtained for the tectonically stable North-European Platform.     

Stresses and displacements due to a stationary point source of heat in an elastic halfspace

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Potential field of a stationary electric current in a stratified medium with a three-dimensional perturbing body

Summary The potential of the electric field of a stationary current in a two-layered Earth is calculated by applying Green's formula in the case where a three-dimensional inhomogeneity of different conductivity is located in the basement of the layer. It is proved that the potential outside and inside the perturbing body can be calculated from the potential of an electric double-layer distributed on the surface of this body. An integral equation of the Fredholm type is derived for the surface density of the double-layer, together with some of its integral properties. A similar procedure can be applied to computing the magnetic anomalies of three-dimensional magnetized bodies, geothermal anomalies due to three-dimensional inhomogeneities of different heat conductivity, as well as to potential problems of theoretical electrical engineering.     

On the solution of the Molodenskii boundary value problem using successive approximations

Gravimetric methods of determining the figure of the Earth can be divided into two groups. The first employs an auxiliary surface—the geoid. The second employs the so-called quasigeoid as an auxiliary surface. Its main advantage is in that it only uses surface measurements and that it does not require knowledge of the structure of the Earth's crust. This method was treated in [1]. The results display an accuracy of the order of the Earth's flattening. The purpose of this paper is to show that this method can be applied theoretically to reach an arbitrary accuracy.