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Analysis of daily minimum and maximum air temperature at Prague-Klementinum station
Tomšů, Radek ; Kalvová, Jaroslava (advisor) ; Mikšovský, Jiří (referee)
Long-term and continuous air temperature measurements at Prague-Klementinum (regular time observations are carried out since 1775, maximum and minimum air temperatures have been measured since 1881) are suitable for the analysis of possible climate changes. While researching the temperature extremes at this station, the increased occurrence of records of daily maximum air temperatures was documented in the second half of the 20th century, especially in the last 20 years, which is not connected to forcing Prague's urban heat island. There is a very rare occurrence of records of daily minimum air temperatures in the last 50 years, which is probably connected to forcing Prague's urban heat island, but also to the warming in the last decades. The change in the circulation is probably only a partial reason for high frequency of records of daily maximum air temperatures. There is warming about 1 řC by maximum air temperatures between periods 1961-83 a 1984-2006 in every season, except autumn. There is average warming about 0,5 řC by minimum air temperatures between periods 1961-83 a 1984-2006.
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Variability of meteorological processes in stratosphere in relation to vertical ozone profile
Motl, Martin ; Kalvová, Jaroslava (advisor) ; Halenka, Tomáš (referee)
There is studied an influence of dynamical processes in atmosphere on the total ozone and its vertical profile in this work. There are described known atmospherical processes with influence on ozone variability and statistical methods used in the work at first. Then is studied connection between ozone and tropopause height. There are also monitored time trends of ozone and tropopauzse height. There are computed modes of variability for the field of the geopotential in pressure levels from 500 to 10 hPa in the next part of the work and there is studied a statistical connection between computed modes and ozone. There is constructed linear regression model from time trend and computed modes. This model describes considerable part of the ozone variability and there are discussed possibilities of use some similar model for prediction of the total ozone in the resume.
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Singularities in annual cycle of climatic variables, their long-term changes and relationships to atmospheric circulation
Radová, Michaela ; Kyselý, Jan (advisor) ; Kalvová, Jaroslava (referee)
In this thesis a statistical detection of singularities (strong deviations from the smoothed mean annual cycle of a climatic variable) was performed on the basis of mean daily air temperature at the Prague - Klementinum station over the period 1881-2000. A temporal stability of all singularities was investigated, and probabilities of the occurrence of the strongest ones and some of the most often mentioned ones were determined. Long-term changes of occurrence of these singularities and their relationships to atmospheric circulation were analyzed. The results show that the temporal stability (annual recurrence as well as regular occurrence at specific calendar days of a year) cannot be assumed for most singularities. Moreover, some of the singularities found using this procedure can generally be just statistical properties of a chosen sampling without relationships e.g. to circulation conditions. That is why it is not proper to look for singularities tied closely to a specific date and use only one reference period for their detection. Variability of atmospheric circulation is the main source of long-term changes of the occurrence of examined singularities.
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Uncertainty of regional climate models outputs
Kliková, Barbora ; Kalvová, Jaroslava (advisor) ; Pišoft, Petr (referee)
This thesis focuses on examination of the ability of regional climate models (RCMs) to simulate precipitation patterns in the Czech Republic and on evaluation of uncertainties due to different global climate models (GCMs) driving the same RCM and due to different RCMs driven by a single GCM. Model outputs of regional climate models RCAO and HIRHAM driven by global climate models HadAM3H and ECHAM for period 1961-1990 were analyzed. It was shown that spatial variability of mean annual precipitation totals is mainly influenced by RCM. The global driving model determines areal mean and minimum values of precipitation totals for the Czech Republic. Both regional models overestimate the mean annual precipitation totals over most of the area, more markedly with driving model ECHAM. After the analysis of the further precipitation characteristics in selected grid points, it was shown that models RCAO and HIRHAM simulate most of the characteristics differently. Most of the characteristics were not expressed well by the models; the results of the model RCAO were better. Further, the model results distinctively differ between chosen areas. This variability is more noticeable for HIRHAM.
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The relationships between atmospheric circulation and surface climatic elements in Europe
Pokorná, Lucie ; Huth, Radan (advisor) ; Kalvová, Jaroslava (referee) ; Kliegrová, Stanislava (referee)
The relationships between atmospheric circulation and surface climatic elements in Europe Lucie Pokorná Abstract The variability of atmospheric circulation is the most important factor determining the changes in surface climatic elements. In this work, the relationship between atmospheric circulation and surface climatic elements like the temperature and the precipitation amounts and occurrence over the European region and some other climatic elements in central Europe is focused. The atmospheric circulation during the year is represented by modes of low-frequency circulation variability in sea level pressure (SLP) and 500-hPa heights (Z500) obtained by using statistical method "Principal component analysis". The Pearson correlation coefficient is used to describe the relationship between modes and climatic elements. Four circulation patterns in Z500 over Euro-Atlantic sector influence climate in Europe all over the year: the North Atlantic Oscillation (NAO) pattern, the East Atlantic (EA) pattern, and two Eurasian patterns (EU1, EU2). There were found patterns in SLP that strongly correlate with modes of the Z500 and influence surface climate similar way. Statistically important correlations of modes in Z500 and SLP with maximum, minimum and mean temperature, precipitation amounts and occurrence of...
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Spatial variability of precipitation annual cycles
Zíková, Naděžda ; Kalvová, Jaroslava (advisor) ; Pišoft, Petr (referee)
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 consequently 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 climate 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 of the continentality and oceanity on the precipitation annual cycles.
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Uncertainties in regional climate models outputs
Holtanová, Eva ; Kalvová, Jaroslava (advisor) ; Halenka, Tomáš (referee) ; Dubrovský, Martin (referee)
Title: Uncertainties in regional climate models outputs Author: RNDr. Eva Holtanová Supervisor: doc. RNDr. Jaroslava Kalvová, CSc. Department: Dept. of Meteorology and Environment Protection Faculty of Mathematics and Physics Charles University in Prague Present doctoral thesis focuses on the analysis of uncertainties in regional climate model outputs in the area of the Czech Republic. Generally, the uncertainties in model outputs come from inaccuracies of initial and boundary conditions, further from the necessity to parameterize the small scale processes, and the structure of the model, e.g. the choice of numerical schemes or spatial resolution. In case of the simulations of future climate, another source of uncertainty arises. It is the unknown development of forcings that influence the climate system. The analysis in this work focuses on two multi-model ensembles, that come from two international European projects PRUDENCE and ENSEMBLES. The simulated 30-year mean seasonal air temperature and precipitation amounts are used, for the reference period 1961- 1990, and several future time periods. Two techniques were employed to assess the uncertainties. The first one was aimed at dividing the variance of a multi-model ensemble into contributions of regional model, driving global model and emission...
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