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11.
Integral transformations of gravitational gradients onto a Gravity Recovery And Climate Experiment (GRACE) type of observable are derived in this article. The gravitational gradients represent components of the gravitational tensor in the local north-oriented frame. The GRACE type of observable corresponds to a difference between two gravitational vectors as projected onto the line of sight between the two GRACE satellites. In total, three integral transformations relating vertical–vertical, vertical–horizontal and horizontal–horizontal gravitational gradients with the GRACE type of observable are provided. Spectral and closed forms of corresponding isotropic kernels are derived for each transformation. Special cases show that the integral transformations are general and relate gravitational gradients to many other quantities of the gravitational field, such as the gravitational vector, and its radial and tangential components. Correctness of the mathematical derivations is validated in a closed-loop simulation using synthetic data. 相似文献
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14.
The connection between avalanche dynamics and space physics has been studied for several years. In that context we recently suggested an avalanche model which explains the phenomena of reconnection. In this work the model is generalized to include the influence of an extremely strong perturbation, reflecting the effect of plasma storms originating from the sun. In addition, we allow for diffusion processes and show that the behavior changes with the onset of diffusion processes, rendering it quasi-periodic, along with the supression of small-size avalanches. 相似文献
15.
Radovan Pipík Anne-Marie Bodergat Danielle Briot Michal Ková? Ján Král’ Grzegorz Zielinski 《Journal of Paleolimnology》2012,47(2):233-249
The Turiec Basin (TB) of Slovakia formed in the Miocene when the West Carpathians escaped from the Alpine region. The 1,250-m-thick
sedimentary Neogene fill of the basin preserved fossil leaves as well as endemic bivalves, gastropods, and ostracodes. The
paleolimnologic changes recorded in the TB infill were derived from the most abundant fossils, the ostracodes. Five contemporaneous
ostracode assemblages within the Late Miocene lacustrine system were distinguished through statistical analysis. These assemblages
have low species similarity, between 2.1 and 24.1%, and are recognized by shape differences among the Candoninae. The ostracode
assemblages, mollusca fossils, and Sr-isotope ratios suggest a low-salinity environment at the beginning of the Late Miocene,
during a brief connection with the Central Paratethys. When the connection ceased, the basin became an isolated freshwater
lake, with five zones differentiated ecologically and bathymetrically using the ostracode assemblages. Taxonomic comparison
of the faunas of the TB and the freshwater to brackish Neogene basins of Europe demonstrates the endemic character of the
TB ostracode fauna. The biologic characteristics of the ostracode families, along with the geology of the lake basin, suggest
that the longevity of the Late Miocene lake probably exceeded 1 Ma. 相似文献
16.
Attenuation Correction Procedures for Water Vapour Fluxes from Closed-Path Eddy-Covariance Systems 总被引:1,自引:1,他引:0
Benjamin R. K. Runkle Christian Wille Michal Gažovič Lars Kutzbach 《Boundary-Layer Meteorology》2012,142(3):401-423
Evapotranspiration is a source of water vapour to the atmosphere, and as a crucial indicator of landscape behaviour its accurate
measurement has widespread implications. Here we investigate errors that are prevalent and systematic in the closed-path eddy-covariance
measurement of latent heat flux: the attenuation of fluxes through dampened cospectral power at high frequencies. This process
is especially pronounced during periods of high relative humidity through the adsorption and desorption of water vapour along
the tube walls. These effects are additionally amplified during lower air temperature conditions. Here, we quantify the underestimation
of evapotranspiration by a closed-path system by comparing its flux estimate to simultaneous and adjacent measurements from
an open-path sensor. We apply models relating flux loss to relative humidity itself, to the lag time of the cross-correlation
peak between the water vapour and vertical wind velocity signals, and to models of cospectral attenuation relative to the
cospectral power of simultaneous sensible heat-flux measurements. We find that including the role of temperature in modifying
the attenuation–humidity relationship is essential for unbiased flux correction, and that physically based cospectral attenuation
methods are effective characterizers of closed-path instrument signal loss relative to the unattenuated flux value. 相似文献
17.
Martin Mozny Mirek Trnka Zdenek Zalud Petr Hlavinka Jiri Nekovar Vera Potop Michal Virag 《Theoretical and Applied Climatology》2012,107(1-2):99-111
Since 2000, the network of stations that make up the Czech Hydrometeorological Institute (CHMI) has measured the soil moisture content at the 0- to 0.9-m layer using sensors placed within the natural soil profile under closely cropped grass cover. Using information from 8?years of continuous observation at seven stations throughout the Czech Republic, we verified the usefulness of the Soil Moisture Index (SMI). The SMI is a potentially useful index for calculating the water deficit in the Czech Republic and Central Europe. During this period, a statistically significant decrease in moisture content was detected, and negative SMI values predominated. There were frequent occurrences of flash drought, defined as a very rapid decline in soil moisture during a 3-week period. The CHMI can use SMI values below ?3 in the Integrated Warning Service System. The routine calculation of SMI values can alert agricultural producers to the development of flash drought conditions and provide them with information regarding the effectiveness of recent rainfall events. An increase in soil moisture, in contrast, could serve as a warning sign for hydrology because it creates the preconditions for flooding. The complex study of soil humidity regimes is becoming more significant in connection with current global climatic change warnings in hydrological cycles. 相似文献
18.
Michal K?í?ek 《New Astronomy》2012,17(1):1-7
The Hubble constant is split into two terms H = H1 + H2 , where H1 is a decreasing function due to the Big Bang and the subsequent gravitational interaction that slows the expansion of the Universe and H2 is an increasing function that corresponds to dark energy which accelerates this expansion. For T = 13.7 Gyr we prove that H2(T) > 5 m/(yr AU). This is a quite large number and thus the impact of dark energy, which is spread almost everywhere uniformly, should be observable not only on large scales, but also in our Solar system. In particular, we show that Earth, Mars and other planets were closer to the Sun 4.5 Gyr ago. The recession speed ≈5.3 m/yr of the Earth from the Sun seems to be just right for an almost constant influx of solar energy from the origin of life on Earth up to the present over which time the Sun’s luminosity has increased approximately linearly. This presents further support for the Anthropic Principle. Namely, the existence of dark energy guarantees very stable conditions for the development of intelligent life on Earth over a period of 3.5 Gyr. 相似文献
19.
The Jalovecký Creek catchment, Slovakia (area 22.2 km2, mean elevation 1500 m a.s.l.), is likely the last big valley complex in the Carpathian Mountains, in which the hydrological cycle is still governed by natural processes. Hydrological research is conducted there since the end of the 1980s. The overall mission of the research is to increase the knowledge about the hydrological cycle in the highest part of the Carpathians. The research agenda, briefly introduced in the first part of this article, is focused on water balance, snow accumulation and melt and runoff formation. Recent analysis of precipitation, discharge, snow cover and isotopic data from period 1989–2018 indicates that hydrological cycle has become more dynamic since 2014. Although several indicators suggest that it could be related to the cold part of the year, direct links with snow storage and the contribution of snowmelt water to catchment runoff were not confirmed. The second part of the article is therefore focused on an analysis of daily cycles in streamflow in March to June 1988–2018 to obtain a deeper insight into the snowmelt process. We describe characteristics of the cycles and examine their variability over the study period. The results indicate that less snow at the lowest elevations (800–1150 m a.s.l.) since 2009 could have influenced the cessation of the cycles in June since 2010. The possible role of the decreased amount of snow at the lowest elevations in changes in runoff characteristics is also suggested by an increase in time lags between maximum discharges during the events and maximum air temperatures preceding discharge maxima measured near the catchment outlet (at 750 m a.s.l.) in spring 2018 compared to springs with a similar number of streamflow cycles in the years 1988, 2000 and 2009. Wavelet analysis did not indicate changes in global power spectra in hourly discharge and air temperature data. 相似文献
20.
Tomáš Navrátil James B. Shanley Jan Rohovec Irena Dobešová Šárka Matoušková Michal Roll Tereza Nováková Filip Oulehle 《水文研究》2021,35(6):e14255
From 2011 to 2019, mercury (Hg) stores and fluxes were studied in the small forested catchment Lesní potok (LES) in the central Czech Republic using the watershed mass balance approach together with internal measurements. Mean input fluxes of Hg via open bulk deposition, beech throughfall and spruce throughfall during the periodwere 2.9, 3.9 and 7.6 μg m−2 year−1, respectively. These values were considerably lower than corresponding deposition Hg fluxes reported in the early years of the 21st century from catchments in Germany. Current bulk precipitation inputs at unimpacted Czech mountainous sites were lower than those in Germany. The largest Hg inputs to the catchment were via litterfall, averaging 22.6 and 17.8 μg m−2 year−1 for beech and spruce stands. The average Hg input, based on the sum of mean litterfall and throughfall deposition, was 23.0 μg m−2 year−1, compared to the estimated Hg output in runoff of 0.5 μg m−2 year−1, which is low compared to other reported values. Thus, only ~2% of Hg input is exported in stream runoff. Stream water Hg was only weakly related to dissolved organic carbon (DOC) but both concentrations were positively correlated with water temperature. The estimated total soil Hg pool averaged 47.5 mg m−2, only 4% of which was in the O-horizon. Thus Hg in the O-horizon pool represents 72 years of deposition at the current input flux and 3800 years of export at the current runoff flux. Age-dating by 14C suggested that organic soil contains Hg from recent deposition, while mineral soil at 40–80 cm depth contained 4400-year old carbon, suggesting the soil had accumulated atmospheric Hg inputs through millennia to reach the highest soil Hg pool of the soil profile. These findings suggest that industrial era intensification of the Hg cycle is superimposed on a slower-paced Hg cycle during most of the Holocene. 相似文献