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Evaluation of precipitation totals simulated by the ALADIN/PERUN atmospheric reanalysis at high spatial resolution
Bližňák, Vojtěch ; Zacharov, Petr, jr.
Atmospheric reanalyses represent powerful tools for obtaining information about the state of the atmosphere in history, which is obtained by numerical weather prediction (NWP) models whose predictions may (but may not) be improved through the assimilation of measured data. Significant developments in computer technology have recently enabled to increase their spatial resolution so that even meteorological phenomena of a local nature can be better captured. However, most NWP models compensate this capability by reducing the computational domain, which largely limits the use of these forecasts for the following meteorological, climatological and/or hydrological applications. The newly developed ALADIN/PERUN atmospheric reanalysis provides simulations of various meteorological variables at high spatial (2.3 km) and temporal (1 h) resolution over most of Europe between 1989 and 2020. Due to the high resolution of the reanalysed data, it can be expected that precipitation fields will capture local-scale processes well, and thus reproduce more faithfully, for example, heavy convective precipitation. The presented paper aims to evaluate this capability based on gauge-adjusted radar estimates of precipitation totals during warm parts of the year when strong convective but also stratiform precipitation occurs in Central Europe. The accuracy of the localization and precipitation sums will be evaluated for two different runs of the NWP model. The first one (ALADIN/Reanalysis) involves a complete assimilation of the observed data every 6 hours using a 4D-VAR assimilation scheme. The second (ALADIN/Evaluation Run) uses only the boundary conditions from the ERA-5 global reanalysis and the calculation of the forecasts is not further modified based on measured data. Comparing the two runs will provide us with information about the level of physical description in the NWP model as well as the effect of assimilation on the resulting precipitation fields. In addition, the paper is unique in that it will use detailed fields of 'observed' precipitation totals at high spatial resolution, which conventional rain gauge data cannot offer.\n
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Testing of products generated from Meteosat satellite (MSG) images in synoptic praxis
Pokorný, Michal ; Žák, Michal (advisor) ; Bližňák, Vojtěch (referee) ; Dejmal, Karel (referee)
First part of the thesis introduces possibilities of depicting of the data provided by the MSG (Meteosat Second Generation) satellite. Different color combinations (RGB - red, green, blue) description made by the basic channels combination follows. The main part of this thesis is focused on T-re profiles (T - temperature, re - effective cloud particle radius). The analysis of profiles of temperature versus the effective radius of cloud particles shows the vertical distribution of the effective particle size in clouds. The profiles are computed and constructed from the satellite retrieved data and they show graphically the distribution of cloud particles and indirectly represent the severity of the developing storms. Forecasting and predicting dangerous phenomena such as hailstorms or tornados that occur in severe storms is the main objective of the technique. This nowcasting tool was tested in Central Europe and the end of this thesis presents the results of the testing.
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Possibilities of Using of Remote Detection Data for Convective Storms Intensity Nowcasting
Valachová, Michaela ; Žák, Michal (advisor) ; Bližňák, Vojtěch (referee) ; Simon, André (referee)
Title: Possibilities of Using of Remote Detection Data for Convective Storms Intensity Nowcasting Author: Michaela Valachová Department: Department of Atmospheric Physics Supervisor: Mgr. Michal Žák, Ph.D., Department of Atmospheric Physics Abstract: Evolution of 60 isolated convective storms from 2016 and 2017, which formed in the region of Central Europe, is studied by means of multi-sensor observations. According to the reports from the European Severe Weather Da- tabase, two categories of storms are classified: severe and non-severe. Based on radar, lightning and satellite measurements, trends of storm characteristics are analyzed to ascertain their typical behavior. Lightning stroke rates and their change could well warn about the ability of the storm to become severe, therefore a Lightning jump algorithm was proposed within this work. From individual case studies follows that methods of remote sensing offer comprehensive information about convective storm life-cycles. In order to objectively determine crucial variables for estimating the storm se- verity, logistic regression models and regularized regressions (elastic net) are employed. In total 53 variables from the first 30, 60 and 90 minutes of the moni- tored storm lifetime are used to show their predictive skill. Results of the models indicate...
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The analysis of short-term rainfalls and their link to the orography of the Czech republic
Bližňák, Vojtěch
The diploma thesis deals with the dependence of short-term intensive precipitations on the altitude of the Czech Republic. Data from the warm period of the year were used, it means from 1st April to 30th September, because there are the most frequent occurrence of the convective phenomena, which are the cause of the intensive precipitations. It was used data of 3 years: 2002, 2004 and 2005. These data represent the results of radar's measurement from weather radar Network CZRAD (radars Skalky, Brdy), for the year 2005 it was used also data corrected according to the rain gauges network (adjustment). The emphasis is placed on the study of 1-hour precipitation amounts, their comparison with results of 3-hours, 6-hours, 12-hours and 24-hours precipitation amounts and the interpretation in graphs, tables and cartograms. The analyses of 1-hour precipitation amounts showed very slow trend from the lowlands till the altitudes of 600 - 800 m a. s. l. The precipitation amounts descended towards the mountains. During longer precipitations the maximum values were situated mostly in the altitude 500 m a. s. l., whereas the precipitation amounts rose to this altitude, upward descended. Maxima are mostly situated in piedmont windward slopes. It was also used daily rainfall totals from the same years, which...
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Possibilities of Using of Remote Detection Data for Convective Storms Intensity Nowcasting
Valachová, Michaela ; Žák, Michal (advisor) ; Bližňák, Vojtěch (referee) ; Simon, André (referee)
Title: Possibilities of Using of Remote Detection Data for Convective Storms Intensity Nowcasting Author: Michaela Valachová Department: Department of Atmospheric Physics Supervisor: Mgr. Michal Žák, Ph.D., Department of Atmospheric Physics Abstract: Evolution of 60 isolated convective storms from 2016 and 2017, which formed in the region of Central Europe, is studied by means of multi-sensor observations. According to the reports from the European Severe Weather Da- tabase, two categories of storms are classified: severe and non-severe. Based on radar, lightning and satellite measurements, trends of storm characteristics are analyzed to ascertain their typical behavior. Lightning stroke rates and their change could well warn about the ability of the storm to become severe, therefore a Lightning jump algorithm was proposed within this work. From individual case studies follows that methods of remote sensing offer comprehensive information about convective storm life-cycles. In order to objectively determine crucial variables for estimating the storm se- verity, logistic regression models and regularized regressions (elastic net) are employed. In total 53 variables from the first 30, 60 and 90 minutes of the moni- tored storm lifetime are used to show their predictive skill. Results of the models indicate...
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Testing of products generated from Meteosat satellite (MSG) images in synoptic praxis
Pokorný, Michal ; Žák, Michal (advisor) ; Bližňák, Vojtěch (referee) ; Dejmal, Karel (referee)
First part of the thesis introduces possibilities of depicting of the data provided by the MSG (Meteosat Second Generation) satellite. Different color combinations (RGB - red, green, blue) description made by the basic channels combination follows. The main part of this thesis is focused on T-re profiles (T - temperature, re - effective cloud particle radius). The analysis of profiles of temperature versus the effective radius of cloud particles shows the vertical distribution of the effective particle size in clouds. The profiles are computed and constructed from the satellite retrieved data and they show graphically the distribution of cloud particles and indirectly represent the severity of the developing storms. Forecasting and predicting dangerous phenomena such as hailstorms or tornados that occur in severe storms is the main objective of the technique. This nowcasting tool was tested in Central Europe and the end of this thesis presents the results of the testing.
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Radar-based summer precipitation climatology with respect to orography in the Czech Republic
Bližňák, Vojtěch ; Müller, Miloslav ; Kašpar, Marek
The aim of this work is climatological analysis of 10-year series of summer precipitation derived from radar and precipitation\nmeasurements in high spatial and temporal resolution. The definition of the summer season is related to the fact that\nthis part of the year represents the most humid period with the most probable occurrence of extreme rainfall events.\nParticular attention is paid to spatial distribution of average seasonal and maximum 30 min - 24 h\ntotal precipitation in the middle and mountainous locations. Part of the study is also the characteristic of daytime precipitation with respect\non the Czech Republic (Czech Republic).\nDespite the relatively short period of 10 summer seasons, the present work provides new and more detailed knowledge\nthe spatial and temporal distribution of the mean and maximum sums of summer precipitation. Within climatological analysis\nis used glide sums of precipitation that are better able to capture absolute maxima in time series,\nwhich gives room for more precise calculation of frequency of occurrence, respectively. N-year rainfall sums in sub-days\nscale. Calculated climatological characteristics will be further refined in the future with prolonged time\nmeasurement.
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