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Possible Seismic Influence on VLF Wave Intensity: Observations by a Low-Altitude Satellite
Němec, František; Santolík, Ondřej; Parrot, M.
2008 - English
We present results of a statistical study of VLF (up to 10 kHz) wave intensity measured by a low-altitude spacecraft in the vicinity of earthquakes. The data from the French DEMETER spacecraft (altitude about 700 km, nearly Sun-synchronous orbit) that was specially developed for such kind of studies are used. The recently developed two-step data processing method is briefly introduced and the main obtained results are reviewed. Finally, a simple independent test of the obtained results is done in order to give an additional evidence for the existence of possible seismic-related effect. Our results indicate that there is a decrease of power spectral density of electric field fluctuations shortly (0-4 hours) before the time of the main shock. This decrease was observed close to surface earthquakes (depth less than 40 km) with magnitude larger than or equal to 4.8 and only during the night. No similar effect was observed for deep earthquakes nor during the day. Výsledky statistické studie nízkofrekvenčních (f < 10 kHz) elektromagnetických vln pozorovaných na družici s nízkou orbitou v blízkosti zemětřesení. Naše výsledky indikují, že krátce (0-4 hodiny) před hlavním otřesem dochází k poklesu výkonové spektrální hustoty elektrických fluktuací. Tento efekt byl pozorován v blízkosti povrchových (hloubka menší než 40 km) zemětřesení s magnitudou větší nebo rovnou 4.8 během noci. Žádný podobný efekt nebyl pozorován během dne.
Keywords:
seismo-electromagnetic effects; VLF electromagnetic waves; DEMETER
Available at various institutes of the ASCR
Possible Seismic Influence on VLF Wave Intensity: Observations by a Low-Altitude Satellite
We present results of a statistical study of VLF (up to 10 kHz) wave intensity measured by a low-altitude spacecraft in the vicinity of earthquakes. The data from the French DEMETER spacecraft ...
Analysis of Critical Frequencies in the Ionosphere
Mošna, Zbyšek; Šauli, Petra; Santolík, Ondřej
2008 - English
Ionosphere is a highly variable system. The most used way how to describe the state of ionosphere is to deal with the critical frequencies which directly reflect the maximum electron concentration in an ionospheric layer. Ionosphere, like many natural systems, exhibits scaling properties. In this paper, we show results of the scaling analysis of ionospheric data from Pruhonice observatory, geomagnetic, and solar flux data from 1957-2005. Ionosféra je vysoce proměnlivý systém. Pro popis ionosféry se často používají kritické frekvence, které udávají maximální elektronovou koncentraci v dané ionosférické vrstvě. Ionosféra, podobně jako mnoho dalších přírodních systémů, vykazuje scaling vlastnosti. V tomto článku jsou uvedeny výsledky scaling analýzy z ionosférických dat ze stanice Průhonice, geomagnetických dat a dat sluneční aktivity z let 1957-2005.
Keywords:
ionosphere; critical frequencies; scaling; monofractal; multifractal; selfsimilarity
Available at various institutes of the ASCR
Analysis of Critical Frequencies in the Ionosphere
Ionosphere is a highly variable system. The most used way how to describe the state of ionosphere is to deal with the critical frequencies which directly reflect the maximum electron concentration in ...
Ionospheric F-region Drift Measurements in Observatory Průhonice, Seasonal Quiet Day Patterns
Kouba, Daniel; Šauli, Petra; Boška, Josef; Santolík, Ondřej
2007 - English
In the paper we concentrate on the F-region drift-data measured by the ionospheric station Pruhonice (50.0N, 14.6E). We demonstrate application of the skymap points selection method on the data set collected in 2006, during a period of low geomagnetic and solar activity. Using histograms of horizontal and vertical velocity components we found prevailing directions of plasma motion corresponding to specified ranges of velocities. Within the analyzed data we found significant decrease of the daily-maximal horizontal component from winter to summer 2006. Článek se zaměřuje na ionosférická driftová měření v F-vrstvě na stanici Průhonice. Demonstrujeme aplikaci metody výběru zdrojových bodů na datech pro rok 2006, tj. pro období nízké geomagnetické a sluneční aktivity. Na histogramech horizontální a vertikální složky rychlosti nacházíme převažující směr pohybu plazmatu pro různé úrovně rychlostí. V analyzovaných datech jsme pro období zima – léto nalezli výrazný pokles denního maxima horizontální složky.
Keywords:
ionospheric drift; Digisonde; F-region; skymap
Available at various institutes of the ASCR
Ionospheric F-region Drift Measurements in Observatory Průhonice, Seasonal Quiet Day Patterns
In the paper we concentrate on the F-region drift-data measured by the ionospheric station Pruhonice (50.0N, 14.6E). We demonstrate application of the skymap points selection method on the data set ...
Evaluation of uncertainty in the area related quantitative precipitation forecast of heavy convective precipitation
Zacharov, Petr, jr.; Řezáčová, Daniela
2007 - English
Extreme convective events have been studied with numerical weather prediction model LM COSMO (horizontal resolution of 2.8km) and radar data. An ensemble of 13 forecasts, which followed from modyfying initial fields, was created for two of analyzed events. Uncertainty in area-related quantitative precipitation forecast (QPF) was evaluated by fraction skill score (FSS) to quantify an ensemble spread and skill. The spread assesses a difference between a control forecast and ensemble member forecasts and the skill evaluates a difference between a precipitation forecast and radar derived precipitation. The uncertainty analysis shows an effect of forecast lead time and space scale as well as a sensitivity to the area structure of precipitation field. In this paper we summarize our first results dealing with the scale influence on the ensemble spread and skill. Pomocí numerického předpovědního modelu LM COSMO (horizontální rozlišení 2.8km) a radarových dat jsme studovali události s extrémními konvektivními srážkami. Pro dvě vybrané události byl vytvořen ensemble 13-ti předpovědí, ktarý vznikl díky modifikaci počátečních podmínek. Nejistota v plošné předpovědi srážek (QPF) byla vyhodnocena pomocí verifikační techniky FSS ("Fraction Skill Score"). Byl stanoven rozptyl ("spread") a kvalita ("skill") ensemble předpovědi. Rozptyl ("skill") stanovuje rozdíl mezi kontrolní předpovědí srážek (předpověď s nezměněnými poč. podmínkami) a předpovědí srážek jednotlivých členů ensemblu. Kvalita ("skill") stanovuje rozdíl mezi polem srážek získaným z radarových měření a členy enseblu. Analýza ukazuje vliv doby předpovědi, velikosti plochy a stuktury pole předpovědi srážek na kvalitu a rozptyl předpovědi. V této studii shrnujeme první výsledky vlivu velikosti plochy pro výpočet plošné srážky na kvalitu a rozptyl ensemble.
Keywords:
verification; quantitative precipitation forecast; forecast spread; forecast skill; ensemle forecast
Available at various institutes of the ASCR
Evaluation of uncertainty in the area related quantitative precipitation forecast of heavy convective precipitation
Extreme convective events have been studied with numerical weather prediction model LM COSMO (horizontal resolution of 2.8km) and radar data. An ensemble of 13 forecasts, which followed from modyfying ...
Dependence of the Sweep Rate of Whistler-mode Chorus Emissions on the Plasma Density
Macúšová, Eva; Santolík, Ondřej; Gurnett, D. A.; Pickett, J. S.; Nunn, D.; Trakhtengerts, V. Y.; Demekhov, A. G.; Titova, E. E.; Kozelov, V.; Rycroft, M. J.
2007 - English
Whistler-mode chorus consists of intense electromagnetic wave packets generated by a nonlinear mechanism involving wave-particle interactions. Chorus wave packets are discrete frequency-time structures in a frequency range from a few hundreds of Hz to several kHz changing their frequency on a time scale from a few tenths of seconds to a few seconds. The source region of chorus emissions is localised close to the geomagnetic equatorial plane. Our investigation is based on multipoint measurements of the wideband (WBD) plasma wave instruments on board the four Cluster spacecraft. We investigate the sweep rate of the chorus frequency as a Whistler-mode chorus consists of intense electromagnetic wave packets generated by a nonlinear mechanism involving wave-particle interactions. Chorus wave packets are discrete frequency-time structures in a frequency range from a few hundreds of Hz to several kHz changing their frequency on a time scale from a few tenths of seconds to a few seconds. The source region of chorus emissions is localised close to the geomagnetic equatorial plane. Our investigation is based on multipoint measurements of the wideband (WBD) plasma wave instruments on board the four Cluster spacecraft. We investigate the sweep rate of the chorus frequency as a function of the cold plasma density in the equatorial plane and then we compare it A theoretical model, numerical simulations and also our preliminary results from the measurements predict an increasing sweep rate with decreasing cold plasma density.
Keywords:
Chorus Emissions
Available at various institutes of the ASCR
Dependence of the Sweep Rate of Whistler-mode Chorus Emissions on the Plasma Density
Whistler-mode chorus consists of intense electromagnetic wave packets generated by a nonlinear mechanism involving wave-particle interactions. Chorus wave packets are discrete frequency-time ...
Preparation of a Database for the Study of Scaling Phenomena in the Ionosphere
Mošna, Zbyšek; Šauli, Petra; Santolík, Ondřej
2007 - English
The correct forecast of the state of the ionosphere requires understanding of all the effects which influence its behaviour as well as the extent of the relationships in the system. A convenient way how to analyse large data sets and describe the coupling or disconnection at various time scales is to study the scaling phenomena. For the computations of scaling properties of the processes that influence the ionosphere dynamics we have prepared a database of several characteristics that describe the coupling processes in the solar-magnetosphere-ionosphere system. This data are of sufficient length and sampling density to verify the presence or absence of links between the processes under study. Popis dostupných dat a nástin jejich plánovaného zpracování.
Keywords:
scaling phenomena; solar-magnetosphere-ionosphere coupling
Available at various institutes of the ASCR
Preparation of a Database for the Study of Scaling Phenomena in the Ionosphere
The correct forecast of the state of the ionosphere requires understanding of all the effects which influence its behaviour as well as the extent of the relationships in the system. A convenient way ...
Ionospheric F-region Drift Measurements, First Results for Winter 2006
Kouba, Daniel; Šauli, Petra; Boška, Josef; Santolík, Ondřej
2006 - English
We describe step by step a newly improved method of drift velocity evaluation: (i) height range selection, (ii) Doppler frequency shift value limitation, and (iii) choice of the maximum incidence angle. Our preliminary results describe drift velocity behaviour during quiet geomagnetic conditions for the winter season for station Pruhonice. Krok po kroku popisujeme nově vyvinutou matodu pro výpočet rychlostí ionosférických driftů (i, určení správného výškového rozsahu; ii, omezení uvažovaných hodnot Dopplerova posunu; iii, volba maximálního úhlu dopadu). Naše předběžné výsledky popisují chování driftových rychlostí za klidných geomagnetických podmínek v zimním období na stanici Průhonice.
Keywords:
Ionospheric drift; Skymap; Digisonde
Available at various institutes of the ASCR
Ionospheric F-region Drift Measurements, First Results for Winter 2006
We describe step by step a newly improved method of drift velocity evaluation: (i) height range selection, (ii) Doppler frequency shift value limitation, and (iii) choice of the maximum incidence ...
Modelling of the wind speed profiles obtained by a sodar in complex terrain
Hošek, Jiří
2005 - English
The wind profiles with two Doppler sodars were measured in wide range of synoptic situations in Ore mountains (Erzgebirge) and in the region of Orlické hory (mountains), both in the Czech republic. Ore mountains represent the region most suitable for construction of wind turbines in the Czech republic. Concerning the observed wind profiles, their generalization may serve for improvement of precision of the simulated wind profile fields. In the second part of the work, we performed the modelling of wind speed profiles in the complex terrain of above-mentioned mountain ranges. We have applied the non-hydrostatic meso-scale models KAMM and PIAP. The numerical simulations with the models were performed for different situations of the ambient flow, described by geostrophic wind speed and direction, and temperature stratification. Sodarová měření byla prováděna na vhodných lokalitách Krušných a Orlických hor v letech 2000 a 2003 v široké škále synoptických situací. Krušné hory představují nejvhodnější oblast ke stavbě větrných elektráren. Zobecnění získaných profilů rychlosti větru může pomoci zlepšit přesnost numerických modelů v takových výškách nad povrchem, které jsou významné pro stavbu větrných elektráren. Ve druhé části práce jsou v obou oblastech počítána pole rychlosti větru pro termíny získaných vertikálních profilů. Použity byly nehydrostatické mezoměřítkové modely KAMM a PIAP. Inicializace modelů byla provedena rychlostí a směrem geostrofického proudění a teplotním zvrstvením.
Keywords:
wind profile; sodar; boundary layer; complex terrain
Available at various institutes of the ASCR
Modelling of the wind speed profiles obtained by a sodar in complex terrain
The wind profiles with two Doppler sodars were measured in wide range of synoptic situations in Ore mountains (Erzgebirge) and in the region of Orlické hory (mountains), both in the Czech republic. ...
Pollutant concentration in cloud water in relation to the air flow direction at 850 hPa level
Fišák, Jaroslav; Řezáčová, Daniela; Fottová, D.; Potužníková, Kateřina
2004 - English
The negative impact of pollutant concentration in fog water on the environment and consequently on the health of population was proved by numerous studies. Recently, the investigation has been focused on the pollutant concentration in fog water from several points of view. In this paper we briefly summarizethe results of clustering the fog water samples according to the enrichment factor and establishing the link of clusters and the air flow at 850 hPa level Negativní dopad koncentrací polutantů v mlžné vodě na přírodní prostředí a následně na zdravotní stav populace byly ukázány v řadě studií. Výzkum koncentací polutantů v mlžné vodě byl prováděn s různým zaměřením. V tomto příspěvku jsou stručně shrnuty výsledky shlukování vzorků mlžné vody v závislosti na faktoru obohacení a stanovení závislosti shluků na proudění vzduchu v hladině 850 hPa
Keywords:
pollutant concentration; fog water; environment
Fulltext is available at external website.
Pollutant concentration in cloud water in relation to the air flow direction at 850 hPa level
The negative impact of pollutant concentration in fog water on the environment and consequently on the health of population was proved by numerous studies. Recently, the investigation has been focused ...
On methods distinguishing drop size distribution type for improved estimation of radiowave attenuation due to rain
Fišer, Ondřej
2003 - English
The contribution shows some criteria to distinguish the rain types (related to the drop size distribution-DSD types) aimed at improved rain attenuation estimation.
Keywords:
drop size distribution; rain types; radar reflectivity factor
Available at various institutes of the ASCR
On methods distinguishing drop size distribution type for improved estimation of radiowave attenuation due to rain
The contribution shows some criteria to distinguish the rain types (related to the drop size distribution-DSD types) aimed at improved rain attenuation estimation.
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