National Repository of Grey Literature 33 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Zahradníček, Pavel ; Rožnovský, J. ; Brzezina, J. ; Štěpánek, Petr ; Farda, Aleš ; Chuchma, F.
Air temperature in winter months and colder half-year is an important factor for wide range of human activities, including recreation. As a result of current climate change, average air temperatures increase in winter as well. This, however, does not mean that there are no frosts. Each winter season can be assessed using several parameters. In this paper we used the sum of effective air temperatures below 0 degrees C and- 5 degrees C. Absolute minimum air temperature was used as an indicator of the extremity of a particular period. Space-time analysis has been performed for both parameters. Air temperatures in winter months are to a large extent influenced by the continentality of the climate. In general, the temperatures in Bohemia rise faster compared to Moravia and the absolute lowest minimum air temperatures are observed in the Western parts of the country. Based on a multiparametric analysis of climate characteristics, the coldest winter and colder half-year was in 1963, in contrast, the mildest winter was in 2007.
Summary report for providing meteorological forecasts for CEPS company
Farda, Aleš ; Štěpánek, Petr ; Meitner, Jan ; Zahradníček, Pavel
Global Change Research Institute CAS provides CEPS company with outputs from numerical weather prediction (NWP) models. The cooperation lasts from 2015 up to now. Selected fields of meteorological variables (namely solar radiation - global and direct, and air temperature in 2 m) are processed from grib files into suitable spatial information, like administrative districts (areal averages) or position of grid points of GFS model. NPW models used are ALADIN from Czech Hydrometeorological Institute and GFS model (from NCEP, NOAA). Outputs are provided for several days ahead, and are issued each morning.
System for monitoring and forecast of impacts of agricultural drought
Trnka, Miroslav ; Štěpánek, Petr ; Chuchma, F. ; Možný, M. ; Bartošová, Lenka ; Hlavinka, Petr ; Balek, Jan ; Zahradníček, Pavel ; Skalák, Petr ; Farda, Aleš ; Semerádová, Daniela ; Meitner, Jan ; Bláhová, M. ; Fiala, R. ; Žalud, Zdeněk
The methodology describes how to predict soil moisture and drought intensity, and at the same time addresses reliability of the predictions and how these can be used. The ability to predict soil moisture values over a period of up to 9 days is presented through using ensemble of models for numerical weather forecasts. This method brings also new opportunities to mitigate impacts during drought events by farmers using such forecasting tools. With regard to the relatively high predictability of soil moisture and drought intensity, the methodology introduces the basic procedures and provides necessary information for the users. In this methodology, the results of 2017 drought event are presented as an example. The drought forecasting system for the Czech Republic is fully functional and is and will be available through
Frost Indexes for the Cold Half-year in the Czech Republic
Zahradníček, Pavel ; Rožnovský, J. ; Brzezina, J. ; Štěpánek, Petr ; Farda, Aleš ; Chuchma, F. ; Potopová, V.
The dynamics of air temperatures during cold half-year to a large extent affect all human activities. Most significant damages are caused by minimum air temperatures dropping to very low values. Due to the current ongoing climate change, air temperatures in winter in general are increasing, however, this does not necessarily mean the frequency of these very low temperatures decreases. It is not easy to express the course of air temperatures during cold periods using some simple characteristic. Meteorologists and climatologists use various characteristics, which can be referred to as frost indexes. These include the number of frost, ice or arctic days. Since these indexes not always perfectly reflect reaction of the nature to a particular temperature threshold, the analysis also included number of days with minimum air temperature below -3, -5, -7, -10, -15, -20 and -25°C. In the last 15 years (2001-2015), there has been a decrease in the frost indexes in comparison to the normal period 1961-1990, this trend however, is not always statistically significant. Significant changes were found in particular in case of the number of days with a higher temperature threshold (frost, ice days and minimum air temperature above -3 to -10°C). In contrast, days with extremely low temperatures are relatively rare (sometimes only observed once in several years), so the dominant factor here is rather variability. The paper also includes an analysis of possible future development based on the most recent climatological models.
Determination and Changes in Winter Severity in the Period between 1961 and 2015
Zahradníček, Pavel ; Rožnovský, J. ; Brzezina, J. ; Štěpánek, Petr ; Farda, Aleš ; Chuchma, F. ; Potopová, V.
Values of the minimum air temperatures during cold periods, especially winter, have often negative impacts on a wide range of human activities. In the past there have been many cases when rapid decrease in air temperature caused damages to machines, halted traffic etc. Every winter or cold half-year can be assessed using several parameters. In this article, three climatological characteristics were used. First was the average air temperature. Second was the sum of effective air temperatures below 0°C and -5°C. Last characteristic, which determines the extremity of that particular period, is the absolute minimum air temperature. Space-time analysis was performed for all the three characteristics. Statistically, the most significant change was found in case of the average air temperature – there is a gradual warming since 1961. Air temperatures during winter are to a large extent affected by the continentality of the climate. In Bohemia, the warming is faster than in Moravia and the western part of the country has the lowest absolute minimum air temperatures. Using multiparametric analysis of climatological characteristics it was found that the coldest winter and coldest half-year from the analyzed years was in 1963. In contrast, mildest winter was in 2007. Current climatological models predict that winter temperatures by the end of 21st century will be higher by 2.4°C to 4.9°C, which would mean a significant change in the current winter conditions.\n
Increase in Winter Air Temperatures in the Czech Republic between 1961 and 2010
Střeštík, Jaroslav ; Rožnovský, J. ; Štěpánek, Petr ; Zahradníček, Pavel
Based on the analysis of average monthly air temperatures between 1961 and 2010 it can be statistically proven that there is an increasing trend. The actual level of increase, however, is different for each season and is also specific for a particular region – there are differences between Bohemia and Moravia. In the summer, the average monthly air temperatures rise more significantly in Moravia, where there is a higher number of stations with increase of over 1°C compared to Bohemia. This is also true for the spring, for which the difference is not so profound, and is yet smaller in the autumn. In contrast, in the winter there is a more significant increase in Bohemia, where most stations show an increase of over 0.5°C. In Moravia the increase is usually only around 0.3 to 0.4°C. Differences between the increases of average air temperature can also be seen across the individual winter months. Highest increase was found in January, where some stations in Bohemia show an increase of over 1°C, a value that was not observed in Moravia, where some stations have an increase of less than 0.8°C. In December and February, the level of increase in general is much smaller. However, given the predicted increase of air temperatures in the future in general, it can be expected that in the upcoming decades the number of warm winters will increase. Such increase of air temperatures in the winter is likely to have negative impacts for the agriculture.
Use of Euro-CORDEX Models for Drought Prediction with Respect to Black Frosts and Rain Deficit during the Cold Season
Potopová, V. ; Štěpánek, Petr ; Zahradníček, Pavel ; Farda, Aleš ; Türkot, L. ; Hiřmanová, D.
This paper focuses on the analysis of changes in the distribution of frequency, duration and magnitude of drought for various time scales for two future time periods, 2041 - 2070 and 2071 - 2100 and compared to the reference period 1981 - 2010 under the two Representative Concentration scenarios RCP4.5 and RCP8.5. Dry events are calculated and analysed according to the classification of the standardized precipitation evapotranspiration index (SPEI) and the standardized precipitation index (SPI). Estimates of future drought projections based on the SPI tend to underestimate risk, while risk of the SPEI drought magnitude increases by the end of the century, even if precipitation increases moderately.
Analysis of Frosts Observed in the End of April 2016 and the Associated Damages for Fruit Farming
Zahradníček, Pavel ; Rožnovský, J. ; Štěpánek, Petr ; Chuchma, F.
Air temperatures below 0°C, the so-called vegetation period frosts, have always been a problem in the climate conditions of the Czech Republic. The 2015/2016 winter as relatively mild, as well as the following beginning of spring and April. Major damages were caused by sudden rapid drop in air temperatures in the period between 25th and 30th April 2016, as a result of very cold air from the North. Air temperature began to fall on 19th April 2016, but only ground temperatures were below freezing point. Between 25th and 30th April, however, even air temperatures measured at 2m above the ground dropped below 0°C. All over the country, the minimum temperatures were below 0°C, usually between -2 and -4°C. The lowest minimum ground air temperatures were below -5°C at 85% of the area of the Czech Republic. In Moravia, the minimum ground air temperature was below 0°C on five days, in Bohemia it was every day in the period between 25th and 30th April 2016. It should be emphasized that during the flowering time of fruit trees without leaves, the flowers form an active surface. Due to radiation the flower temperature is often even lower than the measured ground air temperature minimum. This analysis does not include the effects of terrain, which determines positions of frost basins.
Forecasting models of solar powerplants and wind farms production based on numerical weather prediction models
Farda, Aleš ; Štěpánek, Petr ; Zahradníček, Pavel ; Rajdl, Kamil ; Meitner, Jan
Performance and potential of daily based forecasts of renewable energy sources power production have been investigated for the Czech Republic. The role of individual numerical weather prediction model errors has been researched and ensemble based technique has been studied as the mean to obtain more precise and reliable results providing a benefit for end users.\n\n
Drought periods in 2014
Zahradníček, Pavel ; Trnka, Miroslav ; Štěpánek, Petr ; Semerádová, Daniela ; Farda, Aleš
The first half of year 2014 was characterized by the occurrence of extreme weather. Episode without precipitation were alternated with thunderstorms, temperature were mostly above normal and was occurred first heat wave. The year began with a very mild winter, when amount of snow was only 27% of long term average and in agricultural region South Moravia only about 10%. The winter temperature was more than 2 degrees C higher than normal. March and April were characterized by low sum of precipitation mainly again in South Moravia, both months were about 70% of long term average. March and April temperature were significantly above normal (March about more than about 4 degrees C and April more than 2 degrees C). In contrast May was cold and rainy. In the middle of the month there were persistent rainfall, which caused an increase of river levels and flooding several areas. June was again very dry. These weather conditions led to the strong dry episodes during first half of the year.

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