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Advective transport between atmospheric layers
Zajíček, Radek ; Šácha, Petr (advisor) ; Karami, Khalil (referee)
The transport in the middle atmosphere is controlled by the global-scale Brewer-Dobson circulation. Advective transport is an important component of the Brewer-Dobson circulation. Using the transformed Eulerian mean framework this thesis focuses in detail on advective transport in the middle atmosphere based on data from the ERA5 reanalysis and chemistry-climate models within the Coupled Model Intercomparison Project Phase 6 (CMIP6) and the Chemistry-Climate Model Initiative (CCMI-1). Part of the thesis concerns the derivation of a new method for analytical decomposition of transport changes into partial kinematic factors such as accelerating residual circulation, changes in the vertical structure of the middle atmosphere and others.
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Type of the scheme and tuning dependence of the parameterized orographic gravity wave drag distribution in global climate models.
Hájková, Dominika ; Šácha, Petr (advisor) ; Gisinger, Sonja (referee)
Orographic gravity waves (OGWs) are ubiquitous in the atmosphere and they have an important influence on the dynamics and energy transport especially in the middle- atmosphere. As such, they have to be included in global climate models. Current global models have a low resolution and for that reason OGW effects have to be parameterized. This thesis focuses on the most important output of the OGW parameterizations - the resulting OGW drag. This drag is transported upwards from the surface by the wave and is distributed in the atmosphere. Parameterization schemes differ in many aspects such as the topography description, inclusion of non-linear effects, tuning of the free parameters and others. We have reviewed and described 7 different parameterizations, which are used in 9 different CMIP6 models. After comparing drag data from each of the models we find unexpectedly great differences in the vertical distribution of the drag as well as the magnitude. Focusing on 4 hotspots around the globe, we proposed hypotheses based on the knowledge of the parameterization schemes that can partially explain the inter-model differences. The thesis can pave the way for a more systematic research of the OGW parameterizations in the future, with an ultimate goal of lowering the amount of uncertainty of the future climate...
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New Perspective on the Role of Gravity Waves in the Stratospheric Dynamics and Variability
Šácha, Petr ; Pišoft, Petr (advisor) ; Dameris, Martin (referee) ; Rieder, Harald (referee)
This thesis is concerned with the role of internal gravity waves (IGWs) in the stratospheric dynamics and variability demonstrating the effect of spatiotemporal distribution of their activity on the stratospheric dynamics and transport. The first part introduces a theoretical overview of the most recent as well as classical approaches used for description of the wave-mean interaction in the middle atmosphere. Methodology for an IGW analysis from the GPS radio occultation density data is described in the next chapter and the advantages of utilization of density data are listed. The third chapter presents results describing the peculiar dynamics and anomalous IGW activity in the Eastern Asia/Northern Pacific region. An important part is dedicated to a discussion of accuracy limits and usability of different IGW activity proxies. The possible impact of the localized IGW activity is investigated using a mechanistic middle and upper atmosphere model in the last chapter. Sensitivity simulations are used to demonstrate an important role of the spatial distribution of IGW activity for a formation of planetary waves and for the longitudinal variability of the Brewer-Dobson circulation. Implications for the middle atmospheric and climate change research are discussed along with consequences for parameterizations of...
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Application of the Nambu mechanics formalism in atmospheric dynamics
Procházková, Zuzana ; Šácha, Petr (advisor) ; Badin, Gualtiero (referee)
Nambu mechanics is a generalization of Hamiltonian mechanics that uses multiple conserved quantities as Hamiltonians. In this thesis, we review Nambu mechanics and its application on the equations of incompressible flow and shallow water equations. The Nambu form of the equations of incompressible flow is guessed based on its Hamiltonian form and derived conserved quantities. With the example of the shallow water equations a more general method of Nambu form derivation is illustrated. Based only on the knowledge of the Hamiltonian and the potential enstrophy moments conservation, the shallow water equations are written as a sum of the Nambu brackets and a Poisson bracket. For the classical potential enstrophy, the derived equations are up to constant factors equivalent to the known form of the shallow water equations. The notation by antisymmetric Nambu brackets is convenient for finding conservative schemes and the theory can be also used for example for the study of deviations of flow from stationary flow.
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On the internal gravity wave - atmospheric circulation interaction
Procházková, Zuzana ; Šácha, Petr (advisor) ; Podglajen, Aurélien (referee)
Internal gravity waves (GWs) are an important component of the atmospheric dynamics, significantly affecting the middle atmosphere by momentum and energy transport and deposition. In order to be able to improve global circulation models, in which the majority of the GW spectrum is not resolved, it is necessary to quantify their effects as precise as possible. We study GWs in a high-resolution simulation of the WRF model around Southern Andes, Antarctic Peninsula and South Georgia Island. We analyse a Gaussian high-pass filter method for separation of GWs from the basic flow. To overcome an observed problem of dependence of the method on a cutoff parameter, we propose an improved method that determines the parameter at each time step from the horizontal kinetic energy spectrum. The differences between the methods are further examined using the horizontal kinetic energy spectrum, vertical potential energy spectrum and forcing to the divergence equation evaluated by the active wind method, which is a recent theory-based method that divides the flow into a balanced flow and a perturbation field. The results suggest that the high-pass filter method does not produce correct results for time periods with strong wave activity.
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Usage possibilities of the cloud products of satellite datasets
Šácha, Petr
Title Usage possibilities of the cloud products of satellite datasets Author: Bc. Petr Šácha Department: Department of Meteorology and Environment Protection Supervisor: RNDr. Petr Pišoft Ph.D. Supervisor's e-mail address: Petr.Pisoft@mff.cuni.cz Abstract: Cloudiness plays an important role in the global energy and water cycle. In particular, the presence of clouds dominates the planetary albedo and takes part in many climate feedback processes. In this thesis a short informational overview of remote sensing, a description of EUMETSAT, satellites, which it used, its part CM- SAF and a search retrieval of current research is given at first. Then the study is focused on the cloud satellite products, especially on CFC (cloud fractional cover) and CTY (cloud type) products. Data sets of daily averages of these products are compared with the daily averages created from the surface SYNOP observations of the total cloud cover and cloud type in the area of the Czech Republic. In the case of big variances between the two examined datasets of daily averaged cloud coverage, possible causes like the sampling error, dependence on season, localization of the station and the elevation and type of cloudiness, are searched. Several statistic analyses and validation scores are computed. Finally, possibilities of the examined...
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Application of the Nambu mechanics formalism in atmospheric dynamics
Procházková, Zuzana ; Šácha, Petr (advisor) ; Badin, Gualtiero (referee)
Nambu mechanics is a generalization of Hamiltonian mechanics that uses multiple conserved quantities as Hamiltonians. In this thesis, we review Nambu mechanics and its application on the equations of incompressible flow and shallow water equations. The Nambu form of the equations of incompressible flow is guessed based on its Hamiltonian form and derived conserved quantities. With the example of the shallow water equations a more general method of Nambu form derivation is illustrated. Based only on the knowledge of the Hamiltonian and the potential enstrophy moments conservation, the shallow water equations are written as a sum of the Nambu brackets and a Poisson bracket. For the classical potential enstrophy, the derived equations are up to constant factors equivalent to the known form of the shallow water equations. The notation by antisymmetric Nambu brackets is convenient for finding conservative schemes and the theory can be also used for example for the study of deviations of flow from stationary flow.
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Usage possibilities of the cloud products of satellite datasets
Šácha, Petr
Title Usage possibilities of the cloud products of satellite datasets Author: Bc. Petr Šácha Department: Department of Meteorology and Environment Protection Supervisor: RNDr. Petr Pišoft Ph.D. Supervisor's e-mail address: Petr.Pisoft@mff.cuni.cz Abstract: Cloudiness plays an important role in the global energy and water cycle. In particular, the presence of clouds dominates the planetary albedo and takes part in many climate feedback processes. In this thesis a short informational overview of remote sensing, a description of EUMETSAT, satellites, which it used, its part CM- SAF and a search retrieval of current research is given at first. Then the study is focused on the cloud satellite products, especially on CFC (cloud fractional cover) and CTY (cloud type) products. Data sets of daily averages of these products are compared with the daily averages created from the surface SYNOP observations of the total cloud cover and cloud type in the area of the Czech Republic. In the case of big variances between the two examined datasets of daily averaged cloud coverage, possible causes like the sampling error, dependence on season, localization of the station and the elevation and type of cloudiness, are searched. Several statistic analyses and validation scores are computed. Finally, possibilities of the examined...
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Usage possibilities of the cloud products of satellite datasets
Šácha, Petr ; Pišoft, Petr (advisor) ; Mikšovský, Jiří (referee)
Title Usage possibilities of the cloud products of satellite datasets Author: Bc. Petr Šácha Department: Department of Meteorology and Environment Protection Supervisor: RNDr. Petr Pišoft Ph.D. Supervisor's e-mail address: Petr.Pisoft@mff.cuni.cz Abstract: Cloudiness plays an important role in the global energy and water cycle. In particular, the presence of clouds dominates the planetary albedo and takes part in many climate feedback processes. In this thesis a short informational overview of remote sensing, a description of EUMETSAT, satellites, which it used, its part CM- SAF and a search retrieval of current research is given at first. Then the study is focused on the cloud satellite products, especially on CFC (cloud fractional cover) and CTY (cloud type) products. Data sets of daily averages of these products are compared with the daily averages created from the surface SYNOP observations of the total cloud cover and cloud type in the area of the Czech Republic. In the case of big variances between the two examined datasets of daily averaged cloud coverage, possible causes like the sampling error, dependence on season, localization of the station and the elevation and type of cloudiness, are searched. Several statistic analyses and validation scores are computed. Finally, possibilities of the examined...
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