Number of found documents: 198
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Metody odhadu extrémních srážek a jejich aplikace v ČR
Picek, J.; Kyselý, Jan; Gaál, Ladislav
2013 - Czech
Příspěvek shrnuje koncepce a metodické postupy, na jejichž základě byla řešena problematika odhadu pravděpodobnosti extrémních srážek a návrhových hodnot v ČR v nedávném období. The paper summarizes concepts and methods applied in estimation of probabilities of extreme precipitation amounts and design precipitation in the Czech Republic in the recent past. This work was motivated by the occurrence of several extraordinary precipitation events that resulted in floods with enormous material damages, but also by advances in the field of statistical modelling of extremes. The methods that we introduce are split in two main parts: methods for estimation of probable maximum precipitation and methods for estimation of design precipitation using different variants of the regional frequency analysis. In the concluding section several open issues and possible directions of follow-up research and improvements are outlined. Keywords: precipitation extremes; design values; probable maximum precipitation; regional frequency analysis Fulltext is available at external website.
Metody odhadu extrémních srážek a jejich aplikace v ČR

Příspěvek shrnuje koncepce a metodické postupy, na jejichž základě byla řešena problematika odhadu pravděpodobnosti extrémních srážek a návrhových hodnot v ČR v nedávném období....

Picek, J.; Kyselý, Jan; Gaál, Ladislav
Ústav fyziky atmosféry, 2013

Occurrence Rate of Equatorial Noise Emissions as a Function of the McIlwain's Parameter
Hrbáčková, Zuzana; Santolík, Ondřej
2012 - English
We report results of a statistical analysis of equatorial noise (EN) emissions based on the data set collected by the four Cluster spacecraft between January 2001 and December 2010. We have investigated a large range of the McIl- wain’s parameter from L 1 to L 11 thanks to the change of orbital parameters of the Cluster mission. We have processed data from the STAFF-SA instruments which analyze measurements of electric and magnetic field fluctuations onboard and provide us with hermitian spectral matrices. We have used linear polarization of magnetic field fluctuations as a selection criterion. Propagation in the vicinity of the geomagnetic equator has been used as an additional criterion for recognition of EN. We have identified about 6000 equatorial passages of all four spacecraft during the investigated time period and about 2000 passages in which we observed EN emissions. We demonstrate that EN can occur almost at all the analyzed L shells. However, the occurrence rate at L shells below 2 and above 8.5 is very low. At L shells above 10 the occurrence rate is zero. We show that EN is dependent on the magnetic local time. Keywords: Cluster spacecraft; Earth's magnetosphere; equatorial noise emission; magnetic local time Available at various institutes of the ASCR
Occurrence Rate of Equatorial Noise Emissions as a Function of the McIlwain's Parameter

We report results of a statistical analysis of equatorial noise (EN) emissions based on the data set collected by the four Cluster spacecraft between January 2001 and December 2010. We have ...

Hrbáčková, Zuzana; Santolík, Ondřej
Ústav fyziky atmosféry, 2012

Rain impact on FSO link attenuation based on theory and measurement
Brázda, V.; Schejbal, V.; Fišer, Ondřej
2012 - English
The FSO link becomes a usual mean of modern wireless communications. But it suffers from atmospheric particles causing attenuation. That´s why this random attenuation must be carefully considered by the FSO link design. As it is known the most serious atmospheric phenomenon is fog, and low cloudiness. But the rain attenuation (night mare of mm wave links) is not negligible on optical links, too. In this contribution we focus on rain attenuation from theoretical as well as experimental point of view. Statistics and rain event analysis are shown. There is an overview and a comparison of several formulas for rain attenuation derived from DSD or rain rate. Rain is not the worst phenomena for the transmission but we can’t neglect its influence on FSO. Only full understanding of influence of real atmosphere can lead to solution of a high availability of FSO systems. Keywords: Free-space optics; atmospheric attenuation; rain rate Available at various institutes of the ASCR
Rain impact on FSO link attenuation based on theory and measurement

The FSO link becomes a usual mean of modern wireless communications. But it suffers from atmospheric particles causing attenuation. That´s why this random attenuation must be carefully considered by ...

Brázda, V.; Schejbal, V.; Fišer, Ondřej
Ústav fyziky atmosféry, 2012

The STEREO/Waves Goniopolarimetric Products for Centre de Données de la Physique des Plasmas
Krupař, Vratislav; Cecconi, B.; Maksimovic, M.; Nguyen, Q. N.; Santolík, Ondřej
2011 - English
We present results on the calibration of the HFR receiver, a part of the S/Waves instrument onboard the STEREO spacecraft. The HFR provides us with GP measurements in the frequency range 125–1975 kHz. The obtained data products will be archived in the Plasma Physics Data Center: CDPP. This paper contains a description of used methods and summarizes outputs of the calibration. Keywords: Solar Radio Emissions; Goniopolarimetric inversion Available at various institutes of the ASCR
The STEREO/Waves Goniopolarimetric Products for Centre de Données de la Physique des Plasmas

We present results on the calibration of the HFR receiver, a part of the S/Waves instrument onboard the STEREO spacecraft. The HFR provides us with GP measurements in the frequency range 125–1975 ...

Krupař, Vratislav; Cecconi, B.; Maksimovic, M.; Nguyen, Q. N.; Santolík, Ondřej
Ústav fyziky atmosféry, 2011

Vliv dešťových srážek na koncentraci prachu v ovzduší
Fišák, Jaroslav; Bartůňková, Kristýna
2011 - Czech
V tomto příspěvku je pozornost věnována vlivu srážek na množství prachu v ovzduší. Jsou použity dvě charakteristiky srážek: srážkový úhrn a doba trvání srážek. Pro stanovení koncentrace prachu v ovzduší je využita suchá filtrovací metoda, kdy byl vzduch nasáván vývěvou přes hlavici s filtrem. Expozice filtru byla cca 1 týden. Doba odběru vzorků nebyla zcela konstantní. Proto bylo nutno přistoupit na relativní charakteristiky. Zvolen byl srážkový úhrn připadající na 1 den expozice filtru. Ještě složitější bylo charakterizovat dobu trvání srážek. Zde bylo zvoleno procentuální vyjádření doby trvání srážek vzhledem k době expozice filtru. Bylo zjištěno, že v období, kdy se vyskytují jen kapalné srážky, je koncentrace prachu v ovzduší silně ovlivněna jejich výskytem. Lze předpokládat, že část prachu je zachycena vodními kapičkami. Část prachu se do ovzduší vůbec nedostane. S růstem doby trvání i množství srážek klesá koncentrace prachu v ovzduší. In this contribution the impact of precipitation on the amount of dust in the air is studied. Two precipitation characteristics are used: precipitation amount and time of precipitation duration. For the determination of dust concentrations dry filtering method was used. By this method the air is being sucked in by the suction pump over the head with filter. The exposition of the filter lasted approximately one weak. The time of samples collecting was not absolutely constant. Therefore it was necessary to choose relative characteristics. Precipitation amount for daily exposition of the filter was used. Even more difficult was to characterize the time of precipitation duration. In this case percent expression of precipitation duration to the time of filter exposition was used. Keywords: dust in the air; precipitation amount; time of precipitation duration Available at various institutes of the ASCR
Vliv dešťových srážek na koncentraci prachu v ovzduší

V tomto příspěvku je pozornost věnována vlivu srážek na množství prachu v ovzduší. Jsou použity dvě charakteristiky srážek: srážkový úhrn a doba trvání srážek. Pro stanovení koncentrace prachu v ...

Fišák, Jaroslav; Bartůňková, Kristýna
Ústav fyziky atmosféry, 2011

Influence of Non-vertical Echoes to Ionogram Scaling
Kouba, Daniel; Koucká Knížová, Petra
2011 - English
Digisonde DPS 4 replaced the older ionosonde IPS 42 KEL Aerospace in the Observatory Pruhonice in January 2004. Additional information about the wave polarization enables us to determine and to distinguish exactly between ordinary and extraordinary wave traces on the ionogram records. This new ability basically changes scaling of the ionograms comparing to the ionograms obtained by classical ionosondes. Digisonde measurements show that in some cases the interpretation of ionograms based on classical ionospheric soundings may lead to the systematic errors, which affect classical ionograms interpretation. We demonstrate possible significant misinterpretations of the ionograms obtained using the classical equipment that is not able to distinguish between ordinary and extraordinary modes and records only time of flight of the electromagnetic sounding pulse. We show the necessity to be careful in using an old ionosonde measurements and scaled data for further analysis. Keywords: Digisonde; ionogram interpretation; spread F Available at various institutes of the ASCR
Influence of Non-vertical Echoes to Ionogram Scaling

Digisonde DPS 4 replaced the older ionosonde IPS 42 KEL Aerospace in the Observatory Pruhonice in January 2004. Additional information about the wave polarization enables us to determine and to ...

Kouba, Daniel; Koucká Knížová, Petra
Ústav fyziky atmosféry, 2011

Evaluating drought risk for permanent grasslands under present and future climate conditions
Trnka, Miroslav; Schaumberger, A.; Formayer, H.; Eitzinger, Josef; Hlavinka, Petr; Semerádová, Daniela; Dubrovský, Martin; Možný, M.; Thaler, S.; Žalud, Zdeněk
2011 - English
Over the past years, the changing climate has affected parts of Czech Republic and Austria by drought spells of the intensity and extend that was unprecedented in previous decades. These events had a significant impact on agricultural areas, especially on the grasslands. The idea behind the GIS monitoring relies on hypothesis that the effect of weather and climate conditions on the grassland production can be estimated by models that describe certain natural processes in a simplified manner and in spatialized form. Keywords: climatic change; drouhgt stress; grasslands; modelling; yield Available at various institutes of the ASCR
Evaluating drought risk for permanent grasslands under present and future climate conditions

Over the past years, the changing climate has affected parts of Czech Republic and Austria by drought spells of the intensity and extend that was unprecedented in previous decades. These events had a ...

Trnka, Miroslav; Schaumberger, A.; Formayer, H.; Eitzinger, Josef; Hlavinka, Petr; Semerádová, Daniela; Dubrovský, Martin; Možný, M.; Thaler, S.; Žalud, Zdeněk
Ústav fyziky atmosféry, 2011

Statistical analysis of equatorial noise emissions as a function of magnetic local time
Hrbáčková, Zuzana; Němec, F.; Santolík, Ondřej
2011 - English
The four spacecraft of the Cluster mission collect a unique data set since January 2001. We process the time period from January 2001 to December 2009. The spacecraft changed their orbits over the last few years, resulting in the data set with excellent coverage of a wide range of radial distances from the Earth, especially in the equatorial plane. We focus on the statistical analysis of whistler-mode waves called the equatorial noise (EN). These intense wave emissions are generated by unstable ion distributions. They propagate close to the geomagnetic equator at frequencies between the local proton cyclotron frequency and the lower hybrid frequency. Polarization of the magnetic field fluctuations corresponding to these emissions is linear. We processed data from the STAFF-SA instruments which preanalyze data from electric and magnetic field fluctuations onboard and provide us hermitian spectral matrices. We use the data measured at radial distances from about 2 to 11 RE to show the dependence of the occurrence of EN on the magnetic local time (MLT). We show from the statistical analysis that EN is occurred at all research radial distances within 10◦ from the geomagnetic equator and the maximum occurrence rate of EN is during the daytime especially in the afternoon sector. Keywords: Cluster spacecraft; Earth's magnetosphere; equatorial noise emission Available at various institutes of the ASCR
Statistical analysis of equatorial noise emissions as a function of magnetic local time

The four spacecraft of the Cluster mission collect a unique data set since January 2001. We process the time period from January 2001 to December 2009. The spacecraft changed their orbits over the ...

Hrbáčková, Zuzana; Němec, F.; Santolík, Ondřej
Ústav fyziky atmosféry, 2011

Models of FSO link attenuation due to fog, rain and wind derived from measurement
Fišer, Ondřej; Brázda, Vladimír; Chládová, Zuzana; Pešice, Petr; Svoboda, Jaroslav; Schejbal, V.
2011 - English
The Institute of Atmospheric Physics of the Czech Academy measures atmospheric attenuation on 60 m experimental FSO link while wavelength being 830 and 1550 nm. The measurement lasts three years. In this contribution we show dependences of FSO link attenuation on visibility, rain rate and selected wind parameters. We show that the measured attenuation values are higher than the theoretical values derived by the Kim formula. The sonic temperature is surprisingly very well correlated with attenuation. Keywords: Free-space optics; atmospheric attenuation; visibility; rain rate; wind parameters; sonic temperature Available at various institutes of the ASCR
Models of FSO link attenuation due to fog, rain and wind derived from measurement

The Institute of Atmospheric Physics of the Czech Academy measures atmospheric attenuation on 60 m experimental FSO link while wavelength being 830 and 1550 nm. The measurement lasts three years. In ...

Fišer, Ondřej; Brázda, Vladimír; Chládová, Zuzana; Pešice, Petr; Svoboda, Jaroslav; Schejbal, V.
Ústav fyziky atmosféry, 2011

The insoluble particles in water deposited from fog at Milešovka Observatory (Czech Republic)
Bartůňková, Kristýna; Fišák, Jaroslav; Stoyanova, V.; Schoumkova, A.
2011 - English
This study concerns insoluble chemical pollution of fog at Milešovka Observatory in the Czech Republic. In period from August 2006 till July 2007, 25 fog samples at the top of Milešovka Mountain in České Středohoří Mountains were collected by active fog water collector. Water samples were filtered. From 53 to 116 particles from every sample were chosen according to the quantity of particles found in dried filters. Altogether it was more than 2000 particles. Particles were examined with the help of Scanning Electron Microscope and Energy Dispersive X-Ray Spectrometer to distinguish sizes, shapes and composition. After analyzing the data, statistical evaluation was made. Particles were put into categories according to their shapes on spherical and not spherical. Typical particles like Al, Si, K, Fe or Ca-rich particles were determined. Focus was also to particles with rarely represented elements like Ni, Au, Pb, Cu, Zr and Ba. Groups of typical insoluble particles were collated according to meteorological conditions - synoptic situations and wind directions which prevailed in the days of fog events in order to try to find out possible sources of this fog pollution. Keywords: Insoluble particles; Scanning Electron Microscope; fog water Available at various institutes of the ASCR
The insoluble particles in water deposited from fog at Milešovka Observatory (Czech Republic)

This study concerns insoluble chemical pollution of fog at Milešovka Observatory in the Czech Republic. In period from August 2006 till July 2007, 25 fog samples at the top of Milešovka Mountain in ...

Bartůňková, Kristýna; Fišák, Jaroslav; Stoyanova, V.; Schoumkova, A.
Ústav fyziky atmosféry, 2011

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