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Design precipitation in Czech river basins
Müller, Miloslav ; Kašpar, Marek ; Hulec, Filip
Data on rainfall intensity on the territory of the Czech Republic with a horizontal resolution of 1 km2 and a time step of 10 minutes, obtained by adjusting radar estimates with data from rain gauge stations, were used to derive design areal precipitation in the Czech river basins of 1st to 4th order and in the basins of surface water bodies. When the rainfall accumulation time is doubled, the design precipitation total in individual pixels increases by about 20% on average. The magnitude of the design totals decreases with increasing catchment area, especially for shorter accumulation periods.
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Evaluation of the areal extremeness of extreme weather events in Czechia in the period of 1961–2020
Kašpar, Marek ; Müller, Miloslav
Due to the multiplication of impacts of weather extremes when occurring in larger area, we proposed an areal approach of their evaluation. We evaluated six types of extreme weather events, namely, heat waves, cold waves, air temperature drops, windstorms, heavy precipitation, and heavy snowfalls. We employed the original method using the Weather Extremity Index derived from return periods of values of relevant meteorological variables in the affected area. Each event is characterized not only by the areal extremeness quantified with the index but also by the spatial extent and duration. In the studied period, heat and cold\nwaves generally reach higher index values in relation with larger affected area. The increase in the frequency and extremity of heat waves is in contrast with the decrease in the frequency of cold waves and significant heavy snowfalls. The frequency of windstorms is slightly decreasing with the most significant ones concentrated in the cold half-year. Air temperature drops are the most frequent in the warm half-year, nevertheless three of four top events occurred in January. The frequency of heavy precipitation tends to fluctuate. The obtained meteorological database of extreme events may help to estimate the parameters of future ones using climate models.
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Comparison of heavy precipitation extremes at the turn of the 19th and the
Brych, Jan ; Müller, Miloslav (advisor) ; Kašpar, Marek (referee)
The purpose of my thesis is to evaluate the extremity of selected precipitation events on territory of the Czech Republic in 1890, 1896, 1897, 1899, 1902 and 1903. I used documented floods to identify specific precipitation events in this period. Individual events were examined by means of the WEI index (weather extremity index) and the frequency of measured precipitation amounts. The most extreme examined event occurred from 27 July to 31 July 1897. Its extremity was also determined by the affected area, which was almost the size of the entire Czech Republic. A very high value of 149 was calculated for the period from 1 September to 4 September 1890. For the events of September 1899, May 1896 and July 1903, the resulting value of WEI was close to the value of 80. The least extreme examined event occurred in June 1902 within a very small affected area (8,630 square kilometres). The recorded value was 25.3 WEI. When comparing the examined events and cases in the years 1961 - 2010 in terms of value of the WEI, I found that the years 1897 (first) and 1890 (fifth) are among the most extreme five years. For comparison, values of the WEI from July 1997, July 1981 and August 2002 were converted into a network of stations that applied to the surveyed years. The results proved the applicability of the WEI...
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Time variability of the vertical copmponent of wind speed and its relationship to other meteorological variables in the Czech Republic
Zeman, Šimon ; Kašpar, Marek (advisor) ; Müller, Miloslav (referee)
Title: Time variability of the vertical component of wind speed and its relationship to other meteorological variables in the Czech Republic Author: Bc. Šimon Zeman Department: Physical Geography and Geoecology Supervisor: RNDr. Marek Kašpar, Ph.D. Abstract: The large-scale vertical velocity of the horizontal scale up to thousands of kilometers has been studied in the presented study. These "centimeters" motions have a significant interest in the formation of cloud and precipitation bands in midlatitudes frontal cyclones. The formation and distribution of large-scale vertical motion in the frontal midlatitude cyclone are mentioned. For the statistical analysis, the data from the reanalysis project ECMWF ERA-40 were used for the Czech territory from 1957 - 2002. From March to July, higher frequency of ascend motions was found. In contrast, descent motions dominated. between September and January. Interannual variability of vertical velocity showed increased frequency of descent motions in the period 1972 - 1982 and increasing frequency of ascend motions between 1983 - 1988. Relationship of vertical velocity and high precipitation has a moderate correlation with exponential regression. Relationship of absolute vorticity advection and vertical velocity have a weak negative correlation. Keywords: vertical...
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Areal extremity of windstorms in the Czech Republic
Polášek, Jan Ferdinand ; Kašpar, Marek (advisor) ; Pop, Lukáš (referee)
Areal extremity of windstorms in the Czech Republic Abstract This thesis deals with the extremeness of events with strong winds in the Czech Republic in the period from 1961 to 2009. The first part is dedicated to the principles of air flow dynamics and to wind climatology. The second part describes theoretical distributions used for evaluating the extremeness of wind speed and presents various computation methods of distribution parameters and interpolation methods of converting point data to spatial information. At the end of this part, two modern indices are introduced: WEI (Weather Extremity Index) and SSI (Storm Severity Index) which use return periods and wind speeds for evaluating the extremeness of windstorms, respectively. The third part contains an application of the methods to the pre-processed data from meteorological stations. The fourth section presents the files of 50 most extreme and 50 seasonally most abnormal windstorms selected by both indices which determine in different ways the extremeness, the affected area and duration of each event. The spatial and temporal aspects of the events are discussed as well, along with their seasonal and interannual variability and causal synoptic conditions. Among extreme wind events, most of them are synoptic scale windstorms related to great horizontal...
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Convective environment indicies and their comparison
Marek, Lukáš ; Müller, Miloslav (advisor) ; Kašpar, Marek (referee)
In this work I created the overwiew of instability indices and other characteristics of convective environment which can be found in the literature. On the basis of variables, which the instability indices are calculated from, I suggested their categorization. It was created five groups of instability indices: (i) indices of isobaric levels differences, (ii) indices of rising air parcel, (iii) indices of potential temperatures, (iv) indices of the energy potential of convection and (v) indices of wind shear. In addition to these five categories it was created the sixth category consists of other thermodynamic characteristics. In the last chapter I used the upper air soundings data and values of instability indices of the University of Wyoming for one storm in Prague and I compared instability indices to each other. The group of the indices of potential temperatures was the most successful in the storm forecast, except the Rackliff index. The bulk Richardson number from the group of indices of wind shear forecasted a supercell storm correctly. The work could be used for creation of instability climatology of the Czech Republic on the basis of the selected instability indices. Keywords: instability index, convection, convective storm
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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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Comparison of heavy precipitation extremes at the turn of the 19th and the
Brych, Jan ; Müller, Miloslav (advisor) ; Kašpar, Marek (referee)
The purpose of my thesis is to evaluate the extremity of selected precipitation events on territory of the Czech Republic in 1890, 1896, 1897, 1899, 1902 and 1903. I used documented floods to identify specific precipitation events in this period. Individual events were examined by means of the WEI index (weather extremity index) and the frequency of measured precipitation amounts. The most extreme examined event occurred from 27 July to 31 July 1897. Its extremity was also determined by the affected area, which was almost the size of the entire Czech Republic. A very high value of 149 was calculated for the period from 1 September to 4 September 1890. For the events of September 1899, May 1896 and July 1903, the resulting value of WEI was close to the value of 80. The least extreme examined event occurred in June 1902 within a very small affected area (8,630 square kilometres). The recorded value was 25.3 WEI. When comparing the examined events and cases in the years 1961 - 2010 in terms of value of the WEI, I found that the years 1897 (first) and 1890 (fifth) are among the most extreme five years. For comparison, values of the WEI from July 1997, July 1981 and August 2002 were converted into a network of stations that applied to the surveyed years. The results proved the applicability of the WEI...
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