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Mozny M.,Czech Hydrometeorological Institute | Brazdil R.,Masaryk University | Dobrovolny P.,Masaryk University | Trnka M.,Mendel University in Brno
Climatic Change | Year: 2012

Cereal crop harvests reflect the weather patterns of the period immediately preceding them, and thus the dates at which they begin may be used as a source of proxy data on regional climate. Using systematic phenological observations in the Czech Lands (now known as the Czech Republic) after 1845, together with exploration of further surviving documentary evidence (chronicles, diaries, financial accounts etc.), it has proved possible to create series of winter wheat harvest dates for the period 1501-2008. Employing linear regression, the harvesting dates of the main cereal species (wheat, rye, barley, oats) were first converted to winter wheat harvest days and then normalised to the same altitude above sea level. The next step consisted of using series of winter wheat harvest dates to reconstruct mean March-June temperatures in the Czech Republic, applying standard palaeoclimatological methods. Series reconstructed by linear regression explain 70% of temperature variability. A profound cold period corresponding with late winter wheat harvests was noted between 1659 and 1705. In contrast, warm periods (i. e. early winter wheat harvests) were found for the periods of 1517-1542, 1788-1834 and 1946-2008. The period after 1951 is the warmest of all throughout the entire 1501-2008 period. Comparisons with other European temperature reconstructions derived from documentary sources (including grape harvest dates), tree-rings and instrumental data reveal generally close agreement, with significant correlations. Lower correlations around A. D. 1650 and 1750 may be partly related to deterioration of socio-economic conditions in the Czech Lands resulting from prolonged wars. The results obtained demonstrate that it is possible to use widely-available cereal harvest data for climate analysis and also that such data constitute an independent proxy data series for the region of Central Europe crucial to further studies of the potential impact of climatic variability and climate change on agriculture. © 2011 Springer Science+Business Media B.V.

Hirschi M.,ETH Zurich | Seneviratne S.I.,ETH Zurich | Alexandrov V.,National Institute of Meteorology and Hydrology | Boberg F.,Danish Meteorological Institute | And 5 more authors.
Nature Geoscience | Year: 2011

Climate change is expected to affect not only the means of climatic variables, but also their variabilities and extremes such as heat waves. In particular, modelling studies have postulated a possible impact of soil-moisture deficit and drought on hot extremes. Such effects could be responsible for impending changes in the occurrence of heat waves in Europe. Here we analyse observational indices based on measurements at 275 meteorological stations in central and southeastern Europe, and on publicly available gridded observations. We find a relationship between soil-moisture deficit, as expressed by the standardized precipitation index, and summer hot extremes in southeastern Europe. This relationship is stronger for the high end of the distribution of temperature extremes. We compare our results with simulations of current climate models and find that the models correctly represent the soil-moisture impacts on temperature extremes in southeastern Europe, but overestimate them in central Europe. Given the memory associated with soil moisture storage, our findings may help with climate-change-adaptation measures, such as early-warning and prediction tools for extreme heat waves. © 2011 Macmillan Publishers Limited. All rights reserved.

Nikodem A.,Czech University of Life Sciences | Kodesova R.,Czech University of Life Sciences | Bubenickova L.,Czech Hydrometeorological Institute
Journal of Hydrology and Hydromechanics | Year: 2013

The aim of this study was to assess the impact of different vegetation on the distribution of rainfall (due to throughfall and stemflow), water regime, and Al and SO4 2- leaching from forest soils. The water flow and Al and SO4 2- transport were modeled using HYDRUS-1D. The study was performed at two elevation transects on the Paličník and Smědava Mountain in Jizera mountains. Podzols and Cambisols were prevailing soil units in this area. It was shown that the effect of the precipitation redistribution on water regime was considerable in the beech forest, while it was almost negligible in the spruce forest. Redistribution of precipitation under trees caused runoff (in one case), increased water discharge through the soil profile bottom, reduction of water storage in the soil, and thus reduction of root water uptake. Simulated Al leaching from the soil profile was determined mainly by the initial Al content in the soil profile bottom. Leaching of SO4 2- was mainly determined by its initial content in the soil and to a lesser extent by redistributed precipitation and SO4 2- deposition.

Elleder L.,Czech Hydrometeorological Institute
Global and Planetary Change | Year: 2010

The flood of February 1784 was one of the most extreme events, not only in Bohemia (present Czech Republic), but across Europe. This paper presents a reconstruction of the 1784 flood hydrograph based on all available, mostly non-instrumental, data. The reconstructed 1784 flood hydrograph, the oldest one available for the Vltava River in Prague, reveals the extraordinary dynamics of the flood. In comparison with the hydrographs of the most disastrous Czech historical floods (of 1845, 1862, 1872, 1890 and 2002), the 1784 flood was a very rapid event. From the onset of precipitation, it took only 45 h for the flood to peak in Prague and there was a ∼ 4 m rise in water level during a 12-hour period. The steep gradient of the rising limb of the flood hydrograph is still a record in Prague and the recorded peak water stage was exceeded only by the flood of 2002. This paper introduces a method for flood reconstruction for the early instrumental period of hydrology and meteorology when the direct measurement of water levels was not widespread. This approach has practical applications for enhanced flood warning systems. An improved understanding of past hydrological extremes may contribute significantly to our understanding of flood dynamics in an era of global change. © 2009 Elsevier B.V. All rights reserved.

Potop V.,Czech University of Life Sciences | Mozny M.,Czech Hydrometeorological Institute | Soukup J.,Czech University of Life Sciences
Agricultural and Forest Meteorology | Year: 2012

Two multi-scalar drought indices, the Standardized Precipitation Index (SPI) and the Standardized Precipitation-Evapotranspiration Index (SPEI), were used to study secular drought evolution from 1901 to 2010 in the lowland regions of the Czech Republic. To assess the temporal patterns of droughts as multi-scalar events, the SPEI and SPI were calculated for short-term (1-2 months), medium-term (3-12 months) and long-term droughts (13-24 months). In this study, daily and monthly potential evapotranspiration was integrated to estimate the evaporative power of the atmosphere and to explain its effect on drought conditions in the Czech Republic. For the lowland regions in the Czech Republic, long winter droughts occurred frequently at the beginning of the 20th century, while spring and summer droughts prevailed toward the end of the century. The mean durations of the drought episodes calculated from both indices were the same in the short time scales, between 2.2 and 2.5 months, whereas the mid- and long-term droughts that were determined based on the SPEI were longer than those that were identified by the SPI. We found relatively significant negative correlations between the SPEI from April to September and the detrended yields of Root vegetables (r= -0.68), and a linear regression model based on the SPEI series explained 59.1% of the variability of the annual detrended yield. The results showed that more frequent occurrences of dry episodes during the growing periods of Brassica vegetables produced damaging effects, especially during the planting and formation of the stem bulbs in kohlrabi, setting of the heads in cauliflower, and head formation in cabbage (late spring and earlier summer droughts). During sowing, the Bulb vegetables were less affected by even the longest dry spell (early spring droughts). Fruit vegetables were exposed to the risk of impact from a longer dry spell during their flowering and formation of the first fruits (summer drought episodes, i.e., SPEI ≤ -1.5 at July-August). However, the greatest fraction of decreases in Fruit vegetable yields occurred during the growing seasons with extreme wet spells in June (SPEI ≥ 1.5). © 2012 Elsevier B.V.

Elleder L.,Czech Hydrometeorological Institute
Hydrology and Earth System Sciences | Year: 2015

This study presents a flood frequency analysis for the Vltava River catchment using a major profile in Prague. The estimates of peak discharges for the pre-instrumental period of 1118-1824 based on documentary sources were carried out using different approaches. 187 flood peak discharges derived for the pre-instrumental period augmented 150 records for the instrumental period of 1825-2013. Flood selection was based on Q10 criteria. Six flood-rich periods in total were identified for 1118-2013. Results of this study correspond with similar studies published earlier for some central European catchments, except for the period around 1750. Presented results indicate that the territory of the present Czech Republic might have experienced extreme floods in the past, comparable - with regard to peak discharge (higher than or equal to Q10) and frequency - to the flood events recorded recently. © 2015 Author(s).

Novak M.,Czech Hydrometeorological Institute
Geographia Polonica | Year: 2013

The new Universal Thermal Climate Index (UTCI) was designed for use in the human bioclimatology and biometeorology field. This article describes a set of basic tests used to test the UTCI. These tests were made using real data from selected meteorological stations in the Czech Republic. Days with extreme temperatures and days with extremely windy conditions (extratropical cyclone known as 'hurricane Kyrill', January 18-19, 2007) were selected for the UTCI testing. The Universal Thermal Climate Index is different from other, more commonly used indices. A complete set of meteorological and radiation factors: air temperature, humidity, wind speed and mean radiation temperature were used using when testing the UTCI. Other indices were calculated using limited numbers of the following factors: air temperature and humidity (Heat Index), air temperature and wind speed (Wind Chill), and also air temperature, humidity and wind speed (NET). Testing of the UTCI was necessary before the possible application of this index in the national weather service of the Czech Republic (CHMI). © Martin Novak.

Hunova I.,Czech Hydrometeorological Institute | Maznova J.,Czech Hydrometeorological Institute | Kurfurst P.,Czech Hydrometeorological Institute
Environmental Pollution | Year: 2014

We present the temporal trends and spatial changes of deposition of sulphur and nitrogen in Czech forests based on records from long-term monitoring. A statistically significant trend for sulphur was detected at most of the sites measuring for wet, dry, and total deposition fluxes and at many of these the trend was also present for the period after 2000. The spatial pattern of the changes in sulphur deposition flux between 1995 and 2011 shows the decrease over the entire forested area in a wide range of 18.1-0.2 g m-2 year -1 with the most pronounced improvement in formerly most impacted regions. Nitrogen still represents a considerable stress in many areas. The value of nitrogen deposition flux of 1 g m-2 year-1 is exceeded over a significant portion of the country. On an equivalent basis, the ion ratios of NO3 -/SO4 2- and NH 4 +/SO4 2- in precipitation show significantly increasing trends in time similarly to those of pH. © 2013 Elsevier Ltd. All rights reserved.

Elleder L.,Czech Hydrometeorological Institute | Herget J.,University of Bonn | Roggenkamp T.,University of Bonn | Niessen A.,University of Bonn
Hydrology Research | Year: 2013

The paper aims to reconstruct peak discharges of historic floods in an urbanized area of the historic city of Prague based on documentary sources from pre-instrumental and the early instrumental period (1481-1825). Approximately 20-30 maximum water levels are denoted by flood-marks, accounts describing or related at unchanged sites, or by early instrumental measurements. The challenge in this reconstruction is the identification and consideration of man-made floodplain modifications influencing the cross-section area and the hydraulic roughness. In order to overcome this problem, a simple approach to estimate peak discharges of historic floods has been developed and applied to the River Vltava. This approach includes a procedure for reconstructing the hydraulic parameters of the river channel and inundated floodplain, coupled with an approach for the verification of estimated peak discharge reliability. As a result of the different hydraulic characteristics associated with ice jam floods all winter-flood events are excluded to avoid their potential inclusion. We present 18 reconstructed discharge maxima. The validation of the technique by comparison with the recent gauged flood of 2002 reveals results of adequate accuracy. The comparison also shows that the flood event of 2002 was conspicuously greater than all calculated summer floods in 1481-1825. © 2013 IWA Publishing.

Novak P.,Czech Hydrometeorological Institute | Kyznarova H.,Czech Hydrometeorological Institute
Atmospheric Research | Year: 2011

The Czech Hydrometeorological Institute (CHMI) has utilized lightning data from the Central European Lightning Detection Network (CELDN) since 1999. The CELDN primarily focuses on the detection of cloud-to-ground (CG) lightning but intra-cloud (IC) lightning detection is also available. Lightning detection is used by the CHMI forecasters as an additional source to radar and satellite data for nowcasting of severe storms. Lightning data are also quantitatively used in automatic nowcasting applications. The quality of lightning data can be evaluated using their climatological characteristics. Climatological characteristics are also useful for defining decision thresholds that are valuable for human forecasters as well as for automatic nowcasting applications. The seven-year period from 2002 to 2008, which had relatively even-quality lightning data, was used to calculate the spatial and temporal distributions of lightning. The monthly number of CG strokes varies depending on the season. The highest number of CG strokes occurs during summer, with more than 20days of at least five detected CG strokes on the Czech Republic territory in June and July. The least number of CG stokes occurs in winter, with less than three days per month having at least five detected CG stokes. The mean diurnal distribution of CG strokes peaks between 1500 and 1600 UTC and reaches a minimum between 0500 and 0800 UTC. The average spatial distribution of CG strokes shows sharp local maxima corresponding with the locations of the TV broadcast towers. The average spatial distribution of CG flash density, calculated on a 20×20 km grid, shows the maximum (3.23 flashes km-2year-1) in the western part of Czech Republic and the minimum (0.92 flashes km-2year-1) in the south-southeast of the Czech Republic. In addition, lightning characteristics related to the identified convective cells, such as distribution of the lightning stroke rates or relation to the radar derived by Vertically Integrated Liquid, are presented. © 2010 Elsevier B.V.

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