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Počet nalezených dokumentů:
274
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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 - anglický
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.
Klíčová slova:
climatic change; drouhgt stress; grasslands; modelling; yield
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Statistical analysis of equatorial noise emissions as a function of magnetic local time
Hrbáčková, Zuzana; Němec, F.; Santolík, Ondřej
2011 - anglický
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.
Klíčová slova:
Cluster spacecraft; Earth's magnetosphere; equatorial noise emission
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
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 - anglický
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.
Klíčová slova:
Free-space optics; atmospheric attenuation; visibility; rain rate; wind parameters; sonic temperature
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
The insoluble particles in water deposited from fog at Milešovka Observatory (Czech Republic)
Bartůňková, Kristýna; Fišák, Jaroslav; Stoyanova, V.; Schoumkova, A.
2011 - anglický
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.
Klíčová slova:
Insoluble particles; Scanning Electron Microscope; fog water
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Multi-band Whistler-mode Chorus Emissions Observed by the Cluster Spacecraft
Macúšová, Eva; Santolík, Ondřej
2011 - anglický
Whistler-mode chorus emissions are one of the most significant mechanisms causing the acceleration of electrons in the outer Van Allen radiation belt to relativistic energies. They consist of individual wave packets divided into two frequency bands separated close to the source region by a gap at 1/2 of the electron cyclotron frequency (fce). This configuration is called banded chorus and it is correlated with magnetic activity. Landau damping is one of the possible explanations describing the existence of the gap. On the other hand, the role of ducts in its formation was also discussed. We present several events of chorus combined with noisy or shapeless chorus-like emissions that are arranged in three or more frequency bands with two or more gaps and are observed mostly in a magnetic latitude range from 3 to 10 degrees on the both sides of the equator. We investigate possible influences of the magnetic local time (MLT), the Kp index, the McIlwain parameter and the plasma density on the formation of these multi-band emissions.
Klíčová slova:
Cluster spacecraft; Whistler-mode chorus emissions
Dokument je dostupný na externích webových stránkách.
Multi-band Whistler-mode Chorus Emissions Observed by the Cluster Spacecraft
Whistler-mode chorus emissions are one of the most significant mechanisms causing the acceleration of electrons in the outer Van Allen radiation belt to relativistic energies. They consist of ...
Scaling Analysis Applied to Ionospheric, Solar and Geomagnetic Data
Mošna, Zbyšek; Koucká Knížová, Petra
2011 - anglický
Scaling analysis based on structure function zeta(q) computed using wavelet analysis and spectrum D(h) is used to study possible connection of ionospheric system with the solar and geomagnetic activity. Data from six ionospheric stations (critical frequency foF2), solar flux F10.7 and geomagnetic indices AE, Kp and Dst are used. Data of foF2 show scale invariance in the period range 2–32 day. Scaling properties of ionospheric data show strong dependence on geomagnetic latitude of the station. Similar distribution of values of scaling exponents h for ionospheric and geomagnetic activity AE and Kp suggests connection between these systems. Values of h for foF2 and F10.7 have different distribution which suggests weak connection between these systems at chosen periods.
Klíčová slova:
Scaling analysis; structure function; ionosphere; critical frequencies
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Scaling Analysis Applied to Ionospheric, Solar and Geomagnetic Data
Scaling analysis based on structure function zeta(q) computed using wavelet analysis and spectrum D(h) is used to study possible connection of ionospheric system with the solar and geomagnetic ...
Automatic Visualization Method of Height–Time Development of Ionospheric Layers
Mošna, Zbyšek; Koucká Knížová, Petra
2010 - anglický
An automatic method for visualization of variability of ionospheric plasma in terms of ionospheric layers is presented. Here, we use the virtual reflection height for visualization. We directly plot the height–time dependence using original raw digisonde outputs. It gives us an opportunity to promptly visualise the ionospheric digital data and locate events of the interest for further analysis. In this paper, we present a variability in height of E-layer with a special focus on the sporadic E-layer. The proposed method is applicable for any ionospheric region.
Klíčová slova:
Ionospheric Layers; Visualization
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Automatic Visualization Method of Height–Time Development of Ionospheric Layers
An automatic method for visualization of variability of ionospheric plasma in terms of ionospheric layers is presented. Here, we use the virtual reflection height for visualization. We directly plot ...
Systematic Analysis of Equatorial Noise Using Data of the Cluster Mission
Hrbáčková, Zuzana
2010 - anglický
The four spacecraft of the Cluster mission are collecting a unique data set. We use data measured between 2002 and 2009. These data are unique not only by their quantity but also because the spacecraft changed their orbits during their operational phase and therefore we have data from a large area around the Earth. We focus our analysis on observations of equatorial noise (EN) which is an intense electromagnetic emission generated by unstable ion distributions. It occurs in the inner magnetosphere and propagates close to the geomagnetic equator between the local proton cyclotron frequency and local lower hybrid frequency. We make systematic analysis of EN using data from the STAFF-SA instruments onboard the four spacecraft of the Cluster mission.
Klíčová slova:
Analysis; Equatorial Noise; Cluster Mission
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Systematic Analysis of Equatorial Noise Using Data of the Cluster Mission
The four spacecraft of the Cluster mission are collecting a unique data set. We use data measured between 2002 and 2009. These data are unique not only by their quantity but also because the ...
Dopady lidské činnosti na horní atmosféru
Laštovička, Jan
2010 - český
Trendy v teplotě mezosféry, elektronové koncentraci v dolní ionosféře, elektronové koncentraci a výšce jejího maxima v E vrstvě, elektronové koncentraci v maximu F1 vrstvy, hustotě termosféry a iontové teplotě ve vrstvě F kvalitativně souhlasí s následky zesíleného skleníkového efektu a tvoří konzistentní scénář globálních změn v horní atmosféře. Byly identifikovány tři skupiny parametrů, které nezapadají do tohoto scénáře, F2 vrstva ionosféry, vodní pára v mezosféře a dynamika mezosféry a dolní termosféry. V článku je podána informaci o pokroku v globálním scénáři dlouhodobých trendů v horní atmosféře se zaměřením na ty tři otevřené problémy. K dlouhodobým trendům přispívá několik dalších faktorů, jmenovitě antropogenní změny stratosférického ozónu, změny koncentrace vodních par v mezosféře, dlouhodobé změny geomagnetické aktivity a magnetického pole Země Trends in the mesospheric temperature, electron concentration in the lower ionosphere, electron concentration and height of its maximum in the E region, electron concentration in the F1-region maximum, thermospheric neutral density and F-region ion temperature qualitatively agree with consequences of the enhanced greenhouse effect and form a consistent pattern of global change in the upper atmosphere. Three groups of parameters were identified as not-fitting this global pattern, the F2 region ionosphere, mesospheric water vapour, and the mesosphere/lower thermosphere dynamics. The paper reports progress in development of the global pattern of trends with emphasis to these three open problems. There are several other factors contributing to long-term trends, namely the stratospheric ozone depletion, mesospheric water vapour concentration changes, long-term changes of geomagnetic activity and of the Earth’s magnetic field.
Klíčová slova:
Upper atmosphere; long-term trends; human activity
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Dopady lidské činnosti na horní atmosféru
Trendy v teplotě mezosféry, elektronové koncentraci v dolní ionosféře, elektronové koncentraci a výšce jejího maxima v E vrstvě, elektronové koncentraci v maximu F1 vrstvy, hustotě termosféry a ...
Statistical Study of the Ionospheric Density Variation Related to the 2010 Chile Earthquake and Measured by the DEMETER Satellite
Píša, David; Santolík, Ondřej; Parrot, M.
2010 - anglický
Statistical Study of the Ionospheric Density Variation Related to the 2010 Chile Earthquake and Measured by the DEMETER Satellite.
Klíčová slova:
Whistler-mode Chorus; Emissions
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Statistical Study of the Ionospheric Density Variation Related to the 2010 Chile Earthquake and Measured by the DEMETER Satellite
Statistical Study of the Ionospheric Density Variation Related to the 2010 Chile Earthquake and Measured by the DEMETER Satellite.
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