Počet nalezených dokumentů: 130
Publikováno od do

TM03000027-V6: ESC 3 - Posouzení vlivu na přesnost navigačních systémů GNSS - Evaluation of factors influencing the GNSS positioning accuracy
Urbář, Jaroslav; Suchánek, P.; Chum, Jaroslav
2022 - anglický
Technická zpráva o vlivu na přesnost navigačních systémů GNSS. Získaná data k ověření vlivu na přesnost navigačních systémů GNSS při výskytu MSTID v ionosféře. \n\nTechnical report analyzing the effect of MSTIDs on an accuracy of GNSS based positioning. The analysis should be performed based on experimentally obtained data.\n Klíčová slova: medium-scale traveling ionospheric disturbances (MSTIDs); Global Navigation Satellite System (GNSS); GADIOD; GNSS Plné texty jsou dostupné na vyžádání prostřednictvím repozitáře Akademie věd.
TM03000027-V6: ESC 3 - Posouzení vlivu na přesnost navigačních systémů GNSS - Evaluation of factors influencing the GNSS positioning accuracy

Technická zpráva o vlivu na přesnost navigačních systémů GNSS. Získaná data k ověření vlivu na přesnost navigačních systémů GNSS při výskytu MSTID v ionosféře. \n\nTechnical report analyzing the ...

Urbář, Jaroslav; Suchánek, P.; Chum, Jaroslav
Ústav fyziky atmosféry, 2022

Total Electron Content Measurements by Single-Frequency GPS Receiver
Rejfek, Luboš; Pitaš, K.; Urbář, Jaroslav; Chmelař, P.
2019 - anglický
In this paper is described the measurement of the Total Electron Content by the single-frequency GPS receiver. Disadvantage of this method is that it cannot be used for realtime processing. The advantages of the proposed method are that the device is cheaper than dual-frequency GPS receiver and it can reinterpret older valuable measurements by such singlefrequency receivers. The algorithm was tested with the dualfrequency receiver. Signal from selected frequency (f1, or f2) was processed by presented algorithm and results were compared with standard processing of the signals, which is used for the dual-frequency receivers. Results are promising. Klíčová slova: GPS; TEC; ionosphere; signal propagation Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Total Electron Content Measurements by Single-Frequency GPS Receiver

In this paper is described the measurement of the Total Electron Content by the single-frequency GPS receiver. Disadvantage of this method is that it cannot be used for realtime processing. The ...

Rejfek, Luboš; Pitaš, K.; Urbář, Jaroslav; Chmelař, P.
Ústav fyziky atmosféry, 2019

Earth-space path propagation characteristics in the climatic conditions of the Czech Republic from Alphasat Ka/Q band experiment
Fišer, Ondřej; Brázda, Vladimír; Pešice, Petr; Grabner, M.
2017 - anglický
The objective of the activity is to prepare, realize and conduct experimental research of the influence of atmospheric phenomena on the Earth-space path propagation characteristics at 20 and 40 GHz (Ka/Q) bands in the specific climatic conditions of the Czech Republic (CR). The scientific approach is based on the comprehensive measurements of physical parameters of atmosphere together with concurrent measurements of propagation characteristics on the Earth-space path and on 10 collocated terrestrial paths with star configuration. The proposed activity will utilize the ESA Alphasat Mission Ka/Q experiment that is designed to investigate the propagation characteristics on slant paths in Europe and elsewhere. Klíčová slova: satellite communication; atmosphere; atmospheric attenuation; propagation characteristics Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Earth-space path propagation characteristics in the climatic conditions of the Czech Republic from Alphasat Ka/Q band experiment

The objective of the activity is to prepare, realize and conduct experimental research of the influence of atmospheric phenomena on the Earth-space path propagation characteristics at 20 and 40 GHz ...

Fišer, Ondřej; Brázda, Vladimír; Pešice, Petr; Grabner, M.
Ústav fyziky atmosféry, 2017

Observation and modelling of local wind circulation in the complex topography of Svalbard archipelago
Chládová, Zuzana; Láska, K.; Hošek, Jiří
2016 - anglický
The atmospheric boundary layer processes over Svalbard fjords are strongly influenced by complex topography and sea ice occurence. In this study we point at foehn winds and low level jets in surrounding of Petuniabukta in central part of Spitsbergen. We used the Weather Research and Forecasting mesoscale model. The low level jets and wind have been successfilly simulated by the model. Klíčová slova: Svalbard; model evaluation; low level jets; föhn Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Observation and modelling of local wind circulation in the complex topography of Svalbard archipelago

The atmospheric boundary layer processes over Svalbard fjords are strongly influenced by complex topography and sea ice occurence. In this study we point at foehn winds and low level jets in ...

Chládová, Zuzana; Láska, K.; Hošek, Jiří
Ústav fyziky atmosféry, 2016

Seasonal Variation in Propagation Directions of Acoustic Gravity Waves in the Thermosphere
Fišer, Jiří; Chum, Jaroslav
2016 - anglický
We investigate seasonal behaviour of acoustic gravity waves (AGWs) in\nthe thermosphere. For this purpose, measurements of HF Doppler sounding stations\noperated by or in cooperation with our institute are used. These measurements\nare compared with previously reported studies which employed different techniques\nof ionospheric observations. The propagation of AGWs is found to have strong\nseasonal dependence. AGWs in summer generally tend to propagate poleward in\nsummer and equatorward in winter. Klíčová slova: thermosphere; acoustics gravity waves; ionosphere; HF Doppler sounding Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Seasonal Variation in Propagation Directions of Acoustic Gravity Waves in the Thermosphere

We investigate seasonal behaviour of acoustic gravity waves (AGWs) in\nthe thermosphere. For this purpose, measurements of HF Doppler sounding stations\noperated by or in cooperation with our ...

Fišer, Jiří; Chum, Jaroslav
Ústav fyziky atmosféry, 2016

Measurements of electromagnetic signals generated by lightning and atmospheric discharges associated with transient luminous events
Zemanová, Hana; Santolík, Ondřej; Kolmašová, Ivana
2016 - anglický
This paper focuses on the measurement techniques of extremely low\nfrequency EM waves generated by lightning. Basic types of lightning and transient\nluminous events along with the definition and properties of Schumann resonance are\npresented. We also show the description of our measurement site in Nov´y Kostel,\nwhich uses one horizontal magnetic antenna.\n Klíčová slova: magnetosphere; lightning; extremely low frequency waves (ELF); transient luminous events; Schumann resonance; Novy Kostel Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Measurements of electromagnetic signals generated by lightning and atmospheric discharges associated with transient luminous events

This paper focuses on the measurement techniques of extremely low\nfrequency EM waves generated by lightning. Basic types of lightning and transient\nluminous events along with the definition and ...

Zemanová, Hana; Santolík, Ondřej; Kolmašová, Ivana
Ústav fyziky atmosféry, 2016

HF Doppler Observations of Ionospheric Disturbances over Taiwan
Fišer, Jiří; Chum, Jaroslav
2015 - anglický
Results of observations of traveling ionospheric disturbances (TIDs) by the multipath continuous HF Doppler sounding system operating in Taiwan are presented. We analysed one-year long period of measurements from April 2014 to March 2015 and investigated horizontal velocities and azimuths of propagation of medium scale traveling ionospheric disturbances (MSTIDs) with periods from 4 min to 60 min. Horizontal velocities range from ≈ 100 m s−1 to ≈ 300 m s−1 and MSTIDs propagate preferentially south-eastward in the local winter and preferentially northward in the local summer. The disturbances rarely propagate with azimuth in the range of 200–290◦ . Klíčová slova: traveling ionospheric disturbances; ionosphere; HF Doppler sounding Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
HF Doppler Observations of Ionospheric Disturbances over Taiwan

Results of observations of traveling ionospheric disturbances (TIDs) by the multipath continuous HF Doppler sounding system operating in Taiwan are presented. We analysed one-year long period of ...

Fišer, Jiří; Chum, Jaroslav
Ústav fyziky atmosféry, 2015

Comparison of parametric methods for radar signal processing
Rejfek, Luboš; Burešová, Dalia; Fišer, O.; Brázda, V.
2015 - anglický
The paper deals with comparison of parametric power spectral density methods for the utilization in the meteorological radar (pulse radar of frequency modulated pulses). We have compared duration of signal processing requested by single methods involved in the test. The methods used are the Auto Regressive model, MUSIC method, Eigen Vector algorithm and CAPON. The best results we have obtained for the AR model. Klíčová slova: PSD method; MUSIC; Eigen Vector algorithm; CAPON; Auto Regressive (AR) model; frequency modulated radar Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Comparison of parametric methods for radar signal processing

The paper deals with comparison of parametric power spectral density methods for the utilization in the meteorological radar (pulse radar of frequency modulated pulses). We have compared duration of ...

Rejfek, Luboš; Burešová, Dalia; Fišer, O.; Brázda, V.
Ústav fyziky atmosféry, 2015

Automated eddy covariance data quality control for long-term measurements
Šigut, L.; Mauder, M.; Sedlák, Pavel; Pavelka, M.; Špunda, V.
2015 - anglický
Estimation of matter and energy exchange using the eddy covariance method is often organized into regional or global networks. To achieve comparability among sites, it is important to standardize and specify the methodology used. Currently, quality control (QC) is one of the most time-demanding steps in data processing within the Czech Carbon Observation System. Although manual QC (MQC) enables consideration of more complex test applications, it is often difficult to document. The aim of this study was to establish an automated QC (AQC) scheme based on available literature and post-processing software and test its effectivity and reliability on sites comprising an agroecosystem and a mature European beech forest. AQC successfully flagged low-quality CO2 fluxes and provided estimates of net ecosystem productivity similar to estimates based on MQC. The tests’ efficiency was particularly high for the agroecosystem, where AQC removed 13% less data than did MQC. We conclude that the adopted AQC displays satisfactory performance, especially for sites with low canopy heights. Klíčová slova: eddy covariance; data quality control Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Automated eddy covariance data quality control for long-term measurements

Estimation of matter and energy exchange using the eddy covariance method is often organized into regional or global networks. To achieve comparability among sites, it is important to standardize and ...

Šigut, L.; Mauder, M.; Sedlák, Pavel; Pavelka, M.; Špunda, V.
Ústav fyziky atmosféry, 2015

Heat waves over Central Europe in ALADIN-Climate/CZ regional climate model: evaluation and future projections
Lhotka, Ondřej; Farda, A.; Kyselý, Jan
2015 - anglický
We evaluated a simulation of Central European heat waves and analysed possible changes of their characteristics in the future climate using the ALADIN-Climate/CZ regional climate model with 25km horizontal grid spacing. Lateral boundary conditions were provided by the ARPEGE global climate model, using historical forcing and the SRES A1B scenario. Observed data were taken from the E-OBS gridded data set. Heat waves were evaluated over 1970−1999 and changes in their characteristics were assessed for 2020−2049. Their definition is based on exceedance of the 90th percentile of summer daily maximum temperature calculated separately for modelled and observed data. ALADIN-Climate/CZ simulates characteristics for the recent climate quite well, especially the overall severity of heat waves. In contrast, temperature amplitude was considerably overestimated. This model projects an increase in overall heat wave severity by a factor of 2 to 3 in the future climate, primarily driven by an increasing number of events. The study shows that ALADIN-Climate/CZ is generally capable of simulating Central European heat waves, which gives more credibility to model projections of future heat waves. Klíčová slova: heat waves; regional climate models; ALADIN-Climate/CZ Dokument je dostupný na externích webových stránkách.
Heat waves over Central Europe in ALADIN-Climate/CZ regional climate model: evaluation and future projections

We evaluated a simulation of Central European heat waves and analysed possible changes of their characteristics in the future climate using the ALADIN-Climate/CZ regional climate model with 25km ...

Lhotka, Ondřej; Farda, A.; Kyselý, Jan
Ústav fyziky atmosféry, 2015

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