National Repository of Grey Literature 61 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Spatial variability of precipitation annual cycles
Slezáčková Zíková, Naděžda
Title: Spatial variability of precipitation annual cycles Author: Naděžda Zíková Department: Department of Meteorology and Environment Protection Supervisor: doc. RNDr. Jaroslava Kalvová, CSc. Supervisor's e-mail address: Abstract: This thesis enquires into the spatial variability of precipitation annual cycles and its representation by regional climate models. Goal is to find suitable metrics that could describe spatial character of the precipitation field and con- sequently evaluate model results. For complete understanding the issue, there is an introduction to modeling with regional climate models and also parameters of the precipitation in the Czech Republic. The main part of the thesis is an application of different methods of descripiton on the results of the regional cli- mate models (including the Czech model ALADIN) and CRU data. Results of the models are compared to observed data transferred into the regular grid. Each method is applied on the model results and assessed with regard to advantages and disadvantages. The metrics that were found useful are recommended for the further evaluation of the spatial variability of precipitation annual cycles. The ALADIN model seems to be quite successfull, weak points are only modelling of the precipitation in spring and the effect...
Prediction of mean hourly values of surface ozone concentrations from passive sampler measurements
Sinkulová, Michaela ; Hůnová, Iva (advisor) ; Zíková, Naděžda (referee)
In terms of air pollution, ground-level ozone is according to current knowledge, contributes the most to damage to ecosystems. To calculate the key indicators of potential damage to ecosystems, such as the exposure index AOT40 and stomatal flux, it is important to know the hourly ozone concentrations, which are the input data for both calculations. For the measurement of O3 air pollution concentrations for the purposes of environmental studies, continuous measurement is not used, but measurement by passive (diffusion) dosimeters, which are exposed for a longer period (usually 1 week-1 month) and thus indicate the average concentration for the relevant longer period. The aim of this diploma thesis is the prediction of hourly concentrations of ground-level ozone from measurements by diffusive samplers, which took place in the period 2006-2010 in Jizerské hory mountains. Monitoring always took place for 2 weeks during the vegetation seasons (April-October) at localities and at various altitudes (714 m above sea level - 1,000 m above sea level). Ogawa diffusive samplers were used. From these average and meteorological concentrations, hourly values of ground-level ozone concentrations were calculated according to the model from professional study and these were compared with measurements from an...
Cafe indoor air quality assesment
Jüthner, Ludvík ; Zíková, Naděžda (advisor) ; Mašková, Ludmila (referee)
Cafes are specific places with increasing popularity these days. However, the spaces used mainly for meetings, work or studying have not been yet explored in detail from the microclimate point of view, although suboptimal microclimatic conditions can have a negative effect not only on employees but also on customers. The bachelor thesis deals with an evaluation of air quality in coffee shops and juxtaposes its findings with the legislation that defines beneficial conditions for the particular environment. The aim of the thesis is to determine whether the values of temperature, relative moisture including the concentration of PM2,5 and carbon dioxide, based on an example of three specific coffee shops situated in the center of Prague, correspond with the acceptable standard quotes stipulated by the law. To that end, the author explores three assumptions: 1) the selected spaces are not strictly controlled by the Public Health Authority in comparison for instance with hospitals and therefore the recorded values do not correspond with the regulations, 2) the number of people worsens the CO2 values and 3) coffee shops with an entrance facing a busy street show a higher concentration of PM2,5. The results were achieved by experimental measuring in Winter months. The theoretical part defines the concept...
The measurement of the heterogeneous particles in the steam
Bartoš, Ondřej ; Hrubý, Jan ; Ždímal, Vladimír ; Kolovratník, Michal ; Jiříček, I. ; Moravec, Pavel ; Zíková, Naděžda
The aim of this extended abstract is to reveal the work done as cooperation between several institutions which was presented and published in recent years (Kolovratník, 2014). The formation of droplets in low-pressure steam turbines has a significant impact on the efficiency of energy conversion due to the strongly nonequilibrium nature of this process . The condensed water also erodes the turbine blades. A very important question is to what extent heterogeneous nucleation contributes to the phase transition process . In the case of heterogeneous nucleation , the number of droplets depends only on the number of h eterogeneous particles in the system, whereas in the case of homogeneous nucleation, the number of created droplets is determined rather by the expansion rate - in a faster expansion, greater supersaturation and more droplets are formed until the released condensation enthalpy quenches the nucleation.\nThe specific number of droplets (number of droplets per unit mass of steam) formed in the turbine can be determined by optical probes, developed first by Walters and later in the Czech Republic improved by Petr and Kolovratník. Until recently, no information was available on the relative importance of heterogeneous nucleation in forming these droplets.
Dependence of activated aerosol on horizontal hydrometeor type.
Zíková, Naděžda ; Pokorná, Petra ; Pešice, Petr ; Sedlák, Pavel ; Ždímal, Vladimír
Atmospheric aerosol (AA) affects not only cloud formation, but also other cloud properties such as droplet size distribution, chemical composition, etc. The interaction between AA and cloud does not have to be investigated only by aerial measurements, but the same processes can be observed in fog and low clouds. An example of a station suitable for such research is Milešovka station, where the fog (or low clouds) is 55% of the time. Here, measurements were made to describe the effect of fog on the number size distributions of AA and activated nucleation nuclei.
Holubová, Adéla ; Zíková, Naděžda ; Ždímal, Vladimír ; Plachá, H. ; Bitter, M.
Differences or similarities of growth rates and condensation sinks - characteristics represanting New Particle Formation events were investigated at four background stations located in different types of enviroments, influenced by a different mixture of emissions sources. We found out that the median growth rate is very similar at all stations and the most grequent length of growth lasted between 2 and 4 hours. On the contrary, differences were found in variables affecting growth rates.
Application of Cross-Section Filtration to Detect and Correct Errors Caused by Technical Problems in SMPS.
Wagner, Zdeněk ; Kovanic, P. ; Zíková, Naděžda ; Ondráček, Jakub ; Schwarz, Jaroslav ; Ždímal, Vladimír
The aim of the work is thus development of a robust algorithm for detection of such errors and their fully automatic correction. The algorithm should be fast so that it could be applied in real time.
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Comparison of Winter Biomass Burning Source Contribution at National Atmospheric Observatory Košetice Based on AMS and Aethalometer Data.
Schwarz, Jaroslav ; Vodička, Petr ; Zíková, Naděžda ; Mbengue, Saliou ; Šerfözö, Norbert ; Pokorná, Petra ; Makeš, Otakar ; Ždímal, Vladimír
Although atmospheric aerosol concentrations exhibit decreasing trend in last decades, the contribution of aerosol emitted by biomass combustion is opposite due to increasing wood combustion used for residential heating. Previous works determined that the share of aerosol of biomass burning origin was up to 50 % in winter. In this work, the data from aerosol mass spectrometer (AMS) and Positive Matrix Factorization (PMF) are used to elucidate biomass combustion aerosol impact at National Atmospheric Observatory Košetice (NAOK) and the results are compared with simple aethalometer model approach.
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