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The course of precipitation totals and water flows in rivers during the 20th century
Střeštík, Jaroslav
Whereas mean air temperatures have increased during the 20th century, though supplemented by considerable fluctuations, and increase further, mean precipitation totals in Prague as well as in the whole Bohemia during the same period slightly decrease. At the same time also mean annual flows in Vltava in Prague and in Labe in Děčín decrease. This decrease is a little less rapid than the decrease of precipitation totals. This fact means that the part of water from atmospheric precipitation which flows way from our territory slowly increases and relatively smaller part remains. This trend appears in summer more than in other seasons. The increasing portion of water which flows away from our territory is caused by the decreasing ability of soil to absorb the water.
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Fly-ash mobility in sandy material
Kodešová, R. ; Kapička, Aleš ; Fialová, Hana ; Žigová, Anna ; Kočárek, M. ; Kopáč, J. ; Petrovský, Eduard
Fly-ash migration in three sands of various particle size distributions and consequently various porosities was studied in the laboratory. The fly-ash was applied on the top of all sands packed in plastic cylinders followed by pulse infiltrations. Water regime was monitored using the soil water content sensors SM200 and micro-tensometers T5. Kappameter SM400 was used to monitor migration of ferrimagnetic particles-tracers presented in the fly-ash. Undisturbed samples of sands polluted by fly-ash were taken at the end of the experiments to study final fly-ash distribution in section planes and thin sections of sandy material.
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Precipitation totals and rich precipitations in Klementinum in Prague between 1805 and 2007
Střeštík, Jaroslav
In the university campus Klementinum in Prague daily precipitation totals have been observed since 1805 without interruption. This seris, in contrast to the temperature series, does not display any long-term change similar to the global warming, only a little drier period 1850-1880 and perhaps a weak decrease after 1980 can be observed. Numbers of days without precipitations in the individual years do not show any long-term change or periodicity. The incidence of rich precipitations can be described by two methods. When it is expressed by the number of days in a year when daily precipitation totals exceeded 5 or 10 mm, its long-term trend is similar to the long-term change of precipitation totals. When it is expressed by the number of days in a year when daily precipitation totals exceeded 1 or 2 per cent of the annual precipitation total, no long-term trend or periodicity is observed.
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Tree stem diameter and the Moon: a detailed analysis of periodic relationships
Mikulecký, M. ; Střeštík, Jaroslav
Zürcher and Cantiani (Nature, 1998) reported "a strong correlation" between rhythmic fluctuations of diameter of spruce stem on one side and gravimetric lunisolar tides on the ohter. The relationship between stem diameter D and tidal force G has been tested by more exact biometrical means. The 75 diameter and gravity hourly values have been processed by the Halberg cosinor regression and by Bartlett cross-"correlation". The higher peaks of the stem curve are located at 0,7-2,8 hours later than the peaks of the inverted tides. The cross-"correlation" between D and G as the function of time lag shows a 24-hour periodicity with its maximal significant deviation from zero for G delayed after D by 4 hours.
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The influence of geomagnetic activity on the course of stratospheric warming
Davídkovová, Hana ; Bochníček, Josef ; Hejda, Pavel ; Huth, Radan
The temperature of the winter polar lower stratosphere is affected except the solar activity and atmospheric circulation by the geomagnetic activity as well. Plausible physical mechanism for its effect was described by Arnold and Robinson. According to this paper, warming in the lower thermosphere caused by geomagnetic activity produces the reduction of blending mid and high latitude air masses. In consequence of this reduction the temperature of solar insulated region (polar lower stratosphere)decreases. The aim of this work is to verify functionality of such mechanism.
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Analysis of the global temperature growth
Střeštík, Jaroslav
Global air temperature increased during the last 150 years approximately by 0.8°C. This increase can be approximated by a polynomial of third order. Nearly the same is valid for the CO2 and other greenhouse gases concentration in the atmosphere. The increase of global temperature is supplemented by considerable fluctuations, where periods with a quicker increase and periods with a slow increase or stagnation can be found. Subtracting the long-term trend from the observed temperature course the sinusoidal variation appears more apparent. Spectral analysis discovers a dominant sine wave with the period of 62 years with maxima in 1878, 1940, and 2002, supplemented by a subsidiary wave with the period of 20.7 years. Combination of these waves with above mentioned polynomial a curve is obtained, which sufficiently well fits into the observed course of global temperature during the whole period 1850-2008.
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Robust solver of a system of nonlinear equations
Růžek, Bohuslav ; Kolář, Petr ; Kvasnička, M.
ANNIT (Artificial Neural Network Inversion Tool) is solver of a set of non- linear equations. It is implemented in MATLAB and Scilab. ANNIT is based on numerical approximation of mapping the right hand sides residuals of the original set of equations to searched parameters. A population of individuals is used for building such approximation. The shape, location and size of this population is adaptively changed during the inversion depending on the convergence of the solved problem. ANNIT has been thoroughly tested by using a set of standard problems and also by using selected geophysical problems (localization of the earthquake hypocenter, magnetotelluric inversion, inversion of group velocities of surface waves etc.).
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