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Climate change impact on avalanches is ambiguous. Fewer, wetter, and smaller avalanches are expected in areas where snow cover is declining, while in higher-altitude areas where snowfall prevails, snow avalanches are frequently and spontaneously triggered. In the present paper, we (1) analyse trends in frequency, magnitude, and orientation of wet- and slab-avalanche activity during 59 winter seasons (1962–2021) and (2) detect the main meteorological and snow drivers of wet and slab avalanches for winter seasons from 1979 to 2020 using machine learning techniques – decision trees and random forest – with a tool that can balance the avalanche-day and non-avalanche-day dataset. In terms of avalanches, low to medium–high mountain ranges are neglected in the literature. Therefore we focused on the low-altitude Czech Krkonoše mountain range (Central Europe). The analysis is based on an avalanche dataset of 60 avalanche paths. The number and size of wet avalanches in February and March have increased, which is consistent with the current literature, while the number of slab avalanches has decreased in the last 3 decades. More wet-avalanche releases might be connected to winter season air temperature as it has risen by 1.8 ∘C since 1979. The random forest (RF) results indicate that wet avalanches are influenced by 3 d maximum and minimum air temperature, snow depth, wind speed, wind direction, and rainfall. Slab-avalanche activity is influenced by snow depth, rainfall, new snow, and wind speed. Based on the balanced RF method, air-temperature-related variables for slab avalanches were less important than rain- and snow-related variables. Surprisingly, the RF analysis revealed a less significant than expected relationship between the new-snow sum and slab-avalanche activity. Our analysis allows the use of the identified wet- and slab-avalanche driving variables to be included in the avalanche danger level alerts. Although it cannot replace operational forecasting, machine learning can allow for additional insights for the decision-making process to mitigate avalanche hazard. [ABSTRACT FROM AUTHOR]

The paper shows a large-scale shift in agroclimatic zones in the territory of the Czech Republic (CR) between 1961 and 2019. The method used for agroclimatic zoning took advantage of high-resolution (0.5 km × 0.5 km) daily climate data collected from 268 climatological and 787 rain-gauge stations. The climate information was combined with soil and terrain data at the same resolution. The set of seven agroclimatic indicators allowed us to estimate rates of changes in agroclimatic conditions over the 1961-2019 period, including changes in the air temperature regime, global radiation, drought, frost risks and snow cover occurrence. These indicators are relevant for all main crops and agroclimatic zoning and account for local soil and slope conditions. The study clearly highlights major shifts in the type and extent of agroclimatic zones between 1961-2000 and 2000-2019, which led to the occurrence of entirely new combinations of agroclimatic indicators. [ABSTRACT FROM AUTHOR]

This paper presents a new analysis of how global warming may affect the size of forest fires through its effects on air temperature, relative humidity, and wind speed. The effects of attack time on the size of the final burned area were also determined simultaneously in the statistical analysis. Two nonlinear functions determining the size of fires in the Prague-East District of the Czech Republic were estimated, based on a set of explanatory variables including air temperature, relative humidity, wind speed, and attack time. The functions were determined by multiple regression analysis combined with logarithmic transformations. The effects of climate change scenarios on future forest fires were calculated using the estimated fire-size function. The results show that if global warming leads to increased air temperature, reduced humidity, and stronger winds, we can expect larger fires. According to climate change scenarios, an upturn in the size of fires is predicted over this century. While we can control the fire by reducing the attack time, the results also show that if firefighters can reach a fire more quickly, the size of the fire will be reduced. If forest management methods, infrastructure, and fire brigade capacity are not adapted to the new climate, larger areas can be expected to be destroyed by fire. [ABSTRACT FROM AUTHOR]

This paper describes a newly designed, experimental, and affordable rock slope monitoring system. This system is being used to monitor three rock slopes in Czechia for a period of up to 2 years. The instrumented rock slopes have different lithology (sandstone, limestone, and granite), aspect, and structural and mechanical properties. Induction crackmeters monitor the dynamic of joints, which separate unstable rock blocks from the rock face. This setup works with a repeatability of measurements of 0.05 mm. External destabilising factors (air temperature, precipitation, incoming and outgoing radiation, etc.) are measured by a weather station placed directly within the rock slope. Thermal behaviour in the rock slope surface zone is monitored using a compound temperature probe, placed inside a 3 m deep subhorizontal borehole, which is insulated from external air temperature. Additionally, one thermocouple is placed directly on the rock slope surface. From the time series measured to date (the longest since autumn 2018), we are able to distinguish differences between the annual and diurnal temperature cycles of the monitored sites. From the first data, a greater annual joint dynamic is measured in the case of larger blocks; however, smaller blocks are more responsive to short-term diurnal temperature cycles. Differences in the thermal regime between the sites are also recognisable and are caused mainly by different slope aspect, rock mass thermal conductivity, and colour. These differences will be explained by the statistical analysis of longer time series in the future. [ABSTRACT FROM AUTHOR]

Many studies showed that afforestation increases carbon storage and it can have effects on physical, chemical and biological properties of soil. Afforestation can affect local and regional climate and these effects differ between tropical, temperate and boreal areas. Forests are also efficient in protecting soils against erosion and their flood mitigation functions or other benefits are described in different publications. In this study, the pattern of air temperatures (20 cm, 40 cm and 60 cm above the surface) was studied 10 years after the afforestation of agricultural land (warm, mild dry region of the Czech Republic) with a mixture of broadleaved tree species (Quercus robur L., Quercus rubra L. and Acer platanoides L.) or monospecific Pinus sylvestris L. stand. The aim of our study was to find out the pattern of air temperatures (20 cm, 40 cm and 60 cm above the surface) on two plots (one of the plots - old beech trees, the other plot - clearing) in a beech (Fagus sylvatica L.) forest in a mildly warm, mildly wet region of the Czech Republic. The afforestation of agriculturally used land led to air temperature cooling and to a reduction of the amplitude of maximum and minimum temperatures. The average air temperature (from April 2021 to the beginning of November 2021) decreased by 0.7-1.1 °C on the afforested plots compared with the agriculturally used plot. In the beech forest, the average temperature decreased on the plot with clearing compared with the old beech trees (from the middle of September 2021 to the middle of November 2021). Our results confirm the benefits of afforestation to climate change mitigation; buffering of extreme temperatures is important for the human thermal comfort. [ABSTRACT FROM AUTHOR]

Air temperature and humidity conditions were monitored in Hradec Králové, Czech Republic, by a network of meteorological stations. Meteorological sensors were placed across a representative variety of urban and suburban environments. The data collected over the 2011-2014 period are analysed in this paper. The data from reference standard meteorological stations were used for comparison and modelling purposes. Air temperatures at the points of interest were successfully modelled using regression relationships. The spatial expression of point measurements of air temperatures was provided by GIS methods in combination with CORINE land cover layer, and satellite thermal images were used to evaluate the significance of these methods. The use of standard climate information has low priority for urban planners. The impact of the urban heat island on city residents and visitors was evaluated using the HUMIDEX index, as it is more understandable for urban planners than temperature conditions as such. The aim of this paper is the modification, description and presentation of urban climate evaluation methods that are easily useable for spatial planning purposes. These methods are based on comprehensible, easily available but quality data and results. This unified methodology forms a theoretical basis for better urban planning policies to mitigate the urban heat island effects. [ABSTRACT FROM AUTHOR]

Winter oilseed rape (Brassica napus) is one of the most cultivated oilseeds in the Czech Republic and belongs among major pollen allergens. Pollen allergies have an extensive clinical impact worldwide, and as well as in the Czech Republic. In this paper, meteorological variables such as mean air temperature, maximum and minimum air temperature, precipitation total and number of rainy days in the period 1991–2012 were studied using the PhenoClim phenological model to find the best predictor of the beginning of flowering of the Brassica napus in the Czech Republic. In addition, temporal and spatial evaluations of the beginning of flowering of the Brassica napus were examined at individual stations in different climatic zones within the same period. In total, three phenological stations at altitudes from 270 m asl to 533 m asl located in warm (W2), medium warm (MW7) or cold (C7) climatic zones were used for detailed evaluation. Based on the observation results at selected stations, the beginning of flowering of the Brassica napus advanced progressively in timing (nearly −15 days) in the 1991–2012 period. The base temperature and temperature sums were calculated for the beginning of flowering of the winter oilseed rape using the PhenoClim computer tool. As the most accurate predictor for the beginning of flowering of the Brassica napus, the mean air temperature was determined. The optimal start day for calculation was 30th January, the threshold (base temperature) was 6.0 °C and the temperature sum was 157.0 °C. The RMSE value was 4.77 and the MBE value was −3.00. The simulated data had a good correlation with the real observed data (the correlation coefficients were within the range from 0.56 to 0.76), and the PhenoClim model results indicate using them in the forecast modeling of the beginning of flowering of the Brassica napus in the Czech Republic. [ABSTRACT FROM AUTHOR]

The current application of local climate zones (LCZs) often ends with (inter)zonal comparation of land surface temperature (LST) or air temperature (AT). LST evaluation employs an enhanced concept of LCZs together with cluster analysis for LCZs grouped based on LST. The paper attempts to combine them into a complex approach derived from the case study on a medium-sized Central European city (Hradec Králové, the Czech Republic). In particular, the paper addresses the following. (i) The relation of LST and AT, when the daily course of temperature profile ranging clear off the surface up to 2 m was fitted by a rational 2D function. The obtained equation enables derivation of the AT from LST and vice versa. (ii) The differences in thermal response of LCZs based on LST or AT, where the highest average LST and average maximum LST show LCZs 10, 2, 3 and 8, i.e., with a significant proportion of artificial surfaces. The cluster of LCZs with a significant representation of vegetation, LCZs 9, B, D, A and G, have significantly lower LST. (iii) The contribution of LCZs to understanding of LST/AT relation and whether their specific relation could be expected in particular LCZs, when subsequent interaction assessment of LST and AT revealed statistically their significant correlation in LCZs for certain cases. [ABSTRACT FROM AUTHOR]

The present study is focused on European beech (Fagus sylvatica L.) growth in eastern Bohemia in the Broumovské stěny National Nature Reserve, Czech Republic. The objective of this research was to develop an evaluation of European beech radial growth in relation to solar activity (number of sunspots), air temperature in the growing season, annual precipitation and air pollution (SO2 depositions). The highest positive significant correlation coefficient was found between radial growth of European beech and number of sunspots, followed by the correlation with air temperature in the growing season. The radial growth showed a negative significant correlation with SO2 depositions. The correlation of the radial growth indicates that precipitation and sunspots have a lower correlation coefficient with beech growth than seasonal temperature during an air pollution disaster in the 21st solar cycle. Radial growth, precipitation total and air temperature in the growing season were processed by spectral analysis for the evaluation of periodic cycles. The 7.5- to 11-year cycles were observed in air temperature and in sunspot cycles. Precipitation and air temperature in the growing season indicate a higher frequency at 3.7-year cycles. The long-term periodicity of radial growth was influenced by both solar activity and fluctuations of growing-season air temperature. [ABSTRACT FROM AUTHOR]

Changes in climatic conditions increase risks associated with crop production in certain regions. Early detection of these changes enables the implementation of suitable adaptation measures in the local area, thereby stabilising agricultural production. Our analysis shows a significant shift in climatic conditions in Czechia between 1961 and 2020. We examined the changes in observed temperature conditions, precipitation distribution, drought occurrences, and frost incidents at a high resolution (0.5 × 0.5 km). The outputs show a significant increase in air temperatures and drought occurrence. Temperature totals above 5 °C in 1991–2020 were 15% higher than in 1961–1990. Furthermore, the relative change in totals above 10 °C was 26% after 1991. Over the last 30 years, drought incidence was four times more frequent than in 1961–1990, particularly in spring. In contrast, no significant changes in the distribution of precipitation occurred, and there was a slight decrease in the probability of frost during the growing season. Ongoing climate change brings warmer and drier conditions to higher-altitude regions in Czechia. Assessing climatic conditions on a global scale is less precise for relatively small and topographically diverse countries like Czechia due to coarse resolution. Therefore, a high-resolution analysis is more appropriate for these countries. [ABSTRACT FROM AUTHOR]

An abstract is a brief of the paper; the abstract should not contain references, the text of the abstract section should be in 12 point normal Times New Roman. Temperature variability was investigated for the near surface air temperature time series measured at Sporilov station (Prague, the Czech Republic) between 2003–2016. The interpretation of the Sporilov daily air temperature averages was completed with the results of the long-term observation at the Prague Klementinum station (daily averages, daily maximum and daily minimum temperatures). Variability was detected by the method of absolute difference of temperature anomalies between two adjacent discrete time periods. The results demonstrated increasing warming trends for all investigated temperature time series and a general reduction of the diurnal temperature range. The range of temperature oscillations reduces also on the annual scale. The temperature variability has shown general decline, however the velocity of the detected variability decreasing trend is significantly minor in comparison with the previously investigated period 1994–2001. The analysis also revealed that the occurrence of both hottest and coldest extremes have been increasing during the investigated period at both stations. [ABSTRACT FROM AUTHOR]

Analysis of a long-term temperature variability of mountains has been neglected for a long time. Here we homogenised and reconstructed four temperature series (1961–2020) of selected mountain stations situated above 1000 m representing the area of northern Moravian mountain ridges (the Czech Republic) and their spatiotemporal variability was examined. A statistically significant increase of 10-year linear trends of annual (0.26–0.38), summer/winter half-year and seasonal mean temperatures were found at most stations. Summer (JJA) was detected as the season with the highest mean temperature increase between 1961–1990 and 1991–2020 normal periods (1.5 °C). From the spatial point of view, the climate conditions were becoming warmer faster in higher elevations compared to the lower ones. At all stations, a statistically significant decrease in ice and frost days was observed (−9.1–19.9 and −9.5–16.3, respectively). Moreover, it was proved that the temperature series of a newly established Vysoká hole station are representative enough and comparable with measurements of other meteorological stations in the studied region. This research provided valuable insight into the temperature variability of mountain ridges and the results completed our sparse knowledge about temperature changes in the mountain regions in Central Europe. [ABSTRACT FROM AUTHOR]

Freshwater fish production is significantly correlated with water temperature, which is expected to increase under climate change. This study evaluated changes in water temperature and their impact on productive ponds at fisheries in the Czech Republic. A model was developed to calculate surface water temperature based on the five-day mean of the air temperature and was then tested in several ponds in three major Czech fish production areas. The output of the surface water temperature model was compared with independently measured data (r = 0.79–0.96), and the verified model was then applied to predict climate change conditions. The results were evaluated with regard to the thresholds characterizing the water temperature requirements of fish species and indicated that the limitation of Czech fish farming results from (i) an increased number of continuous periods during which given fish species are threatened by high water temperatures and (ii) the extension of continuous periods with stressful water temperatures. For Czech fisheries, the model suggests a sharp increase in unprecedented temperature regimes, which will pose critical challenges to traditional forms of common carp farming within several decades. Although reducing the level of eutrophication and loading them with organic substances might alleviate expected threads, farming current fish species in deeper and colder ponds at higher elevations might be inevitable. [ABSTRACT FROM AUTHOR]

Forest ecosystems in Europe undergo cyclic fluctuations with alternating periods of forest prosperity and disturbances. Forest disturbances are caused by large-scale calamities (climate-induced and unforeseen events) resulting in an increased volume of salvage logging. In recent decades, climate change (warming, long-term droughts, more frequent storms, bark beetle outbreaks) has contributed to an increased frequency of salvage logging. However, until now, it has not been revealed what triggers national-scale forest calamities. All of the above-mentioned natural disturbances are connected to solar activity, which is the driver of climate change. This research relates the total volume of harvested timber and salvage logging to the climate and cosmic factors in the Czech Republic, Central Europe. Data of total and salvage logging are compared with air temperatures, precipitation, extreme climatic events, sunspot areas, and cosmic ray intensities. The results document a significant effect of average annual temperatures on the total and salvage logging for the entire period of observations since 1961. A significant correlation of salvage logging to the sunspot area and cosmic ray intensity was observed. The link between salvage logging and sunspots and cosmic ray intensity is supported by spectral analysis in which a significant 11-year cycle was observed since 1973. The results also show an increasing significant effect of sunspots and cosmic ray intensity on logging in recent years in connection with synergism of extreme climate events and the subsequent bark beetle outbreaks. Space and cosmic effects are factors that substantially influence forest ecosystems. Therefore, this paper provides new knowledge about, and possible predictions of, the forest response under climate change. [ABSTRACT FROM AUTHOR]

An increasing number of individuals and institutions own or operate meteorological stations, but the resulting data are not yet commonly used in the Czech Republic. One of the main difficulties is the heterogeneity of measuring systems that puts in question the quality of outcoming data. Only after a thorough quality control of recorded data is it possible to proceed with for example a specific survey of variability of a chosen meteorological parameter in an urban or suburban region. The most commonly researched element in the given environment is air temperature. In the first phase, this paper focuses on the quality of data provided by amateur and institutional stations. The following analyses consequently work with already amended time series. Due to the nature of analyzed data and their potential use in the future it is opportune to assess the appropriateness of chronological and possibly spatial interpolation of missing values. The evaluation of seasonal variability of air temperature in the scale of Brno city and surrounding area in 2015–2017 demonstrates, that the enrichment of network of standard (professional) stations with new stations may significantly refine or even revise the current state of knowledge, for example in the case of urban heat island phenomena. A cluster analysis was applied in order to assess the impact of localization circumstances (station environment, exposition, etc.) as well as typological classification of the set of meteorological stations. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents our first experience with the application of the METRo model, which forecasts road surface temperature and road conditions (e.g., wet or dry surface, ice) in the Czech Republic. In our version, the model uses online measurements from road weather stations (RWS) in the Czech Republic and weather forecasts from ALADIN, the operational numerical weather prediction NWP model of the Czech Hydrometeorological Institute. The METRo model was quasi-operationally tested during the winter season (November 2012–February 2013) using data from 25 RWS. We compared three model runs with an emphasis on road surface temperature. The first run used the original model and served as a reference. The second run applied model output statistics (MOS) to ALADIN forecasts of temperature and humidity at 2m above the ground, which are required by METRo. The third run applied METRo in a nowcasting mode by starting the model every hour and using new measurements available from the RWS. The results indicated that MOS improved the accuracy of the temperature and humidity at 2m but had little impact on the forecasted road surface temperature. However, the nowcasting scheme significantly improved the accuracy of the forecasts for the initial 3 to 4h. The evaluation of the METRo results suggests that the radiation flux forecast is crucial for an accurate road surface temperature forecast. [Copyright &y& Elsevier]

The influence of increased horizontal resolution on regional climate models simulations of 1961-1990 period was investigated with a focus on precipitation. The main attention was paid to the annual cycle of precipitation described by a special characteristic, precipitation half-time. Two models (RegCM3 and ALADIN-CLIMATE/CZ), both of them in two horizontal resolutions (25 and 10 km), were used. An evaluation of model simulations with 25 km resolution on the European domain is presented as well as a more detailed evaluation of both 25 and 10 km versions on the area of the Czech Republic. Generally, the effects of increased horizontal resolution vary with climate model and evaluated characteristic. For the precipitation amount and the dependence of precipitation amount on altitude, the increase in horizontal resolution decreases the accuracy of results in both models. For the simulation of annual precipitation cycle and the precipitation half-time, RegCM3 results improved with the increased horizontal resolution, whereas ALADIN-CLIMATE/CZ results worsened. [ABSTRACT FROM AUTHOR]

Periglacial features, such as various kinds of patterned ground, cryoturbations, frost wedges, solifluction structures, and blockfields, are among the most common relics of cold climate periods, which repetitively occurred throughout the Quaternary. As such, they are widespread archives of past environmental conditions. Climate controls on the development of most periglacial features, however, remain poorly known, and thus empirical palaeo-climate reconstructions based on them have limited validity. This study presents and evaluates a simple new inverse modelling scheme called PERICLIMv1.0 (PERIglacial CLIMate) that derives palaeo-air temperature characteristics related to the palaeo-active-layer thickness, which can be recognized using many relict periglacial features found in past permafrost regions. The evaluation against modern temperature records showed that the model reproduces air temperature characteristics with average errors ≤1.3 ∘C. The past mean annual air temperature modelled experimentally for two sites in the Czech Republic hosting relict cryoturbation structures was between -7.0±1.9 and -3.2±1.5 ∘C , which is well in line with earlier reconstructions utilizing various palaeo-archives. These initial results are promising and suggest that the model could become a useful tool for reconstructing Quaternary palaeo-environments across vast areas of mid-latitudes and low latitudes where relict periglacial assemblages frequently occur, but their full potential remains to be exploited. [ABSTRACT FROM AUTHOR]

• 4 years of species-oriented phenocamera and ground-based phenological observations. • Confirmed prolongation of growing season length due to a warmer climate. • Phenocamera-derived phenophases corresponded closely with field observations. • Greenup was advanced by above-average warm days, but leaf maturation was delayed. • Cold spell in 2017 showed marked effect on phenological shifts. Phenological observations are important as indicators of global warming and as estimation tools for the terrestrial carbon balance in vulnerable ecosystems, such as the last fragments of floodplain forests in the Czechia. The aim of this paper was to compare ground-based phenological observations of three dominant species (European hornbeam, English oak and narrow-leaved ash) in this ecosystem, with the seasonal trajectory of the greenness index (G cc) and thresholds extracted from images taken by phenocameras located on a meteorological mast. The average annual air temperature in the studied years 2014–2017 was 1 °C higher than the long-term average, and the precipitation deficit reached ⅓ of annual rainfall. We found a high proportion of above-average warm days in the warmest part of the growing season. Above-average air temperatures significantly accelerated the onset of budbreak in ash. Yet a higher proportion of above-average air temperatures prolonged the period between budbreak to fully developed leaf area, especially in ash and oak. In 2017, rapid cooling after exceptionally warm temperatures at the onset of spring had a detrimental effect on the stand productivity and showed a marked effect on the phenological shifts. The period when leaf area developed was in the range of DOY 66-286 for hornbeam, DOY 79-329 for oak and DOY 88-321 for ash in 2014–2017. The seasonal trajectory of G cc showed differences between tree species that corresponded to the dynamics of the onset of phenophases observed in the field. According to image analyses, the phenophase of greenup and maturity for hornbeam and ash had minimal uncertainty. In contrast, the uncertainty was high in the determination of phenophases for oak. Our observations show that the modern method of phenological observation by phenocameras is suitable for mixed forests, but classical ground-based observations by a phenologist are still crucial in order to verify the results. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Due to climate change, the question of thermal comfort in cities is becoming more important in Central Europe. The aim of the study is to design and experimentally verify the typology of outdoor areas of restaurants in terms of their thermal comfort factors, based on a case study of Pilsen's city centre. The research carried out in 2017 in the city centre of Pilsen investigated what means are used by restaurants to improve thermal conditions and how the location of an outdoor restaurant in an urban area affects its thermal comfort. There were forty-three outdoor areas of city centre restaurants included in the proposed typology, based upon their location. The relevance of typology was verified using a selected set of fourteen outdoor restaurant areas. They were evaluated according to the availability of means for comfort enhancement and experimental measurements of relevant meteorological elements. Type 1 (Square restaurant) exhibited the highest air and surface temperatures. In contrast, Type 2 (Courtyard restaurant) showed the lowest air and surface temperatures and Type 3 (Park restaurant) showed the highest air humidity. Type 4 (Street canyon restaurant) had similar temperatures to Type 1, and air humidity was closer to Type 2. According to the number of Beergarden Days, the days when the air temperature at 9 p.m. was higher than 20 °C, the best conditions for sitting outside throughout the year occur from the second half of June to the end of August. The results of the study can contribute to an improvement in the thermal comfort of customers of outdoor restaurants in cities, especially with regard to the choice of locations of outdoor restaurants and the use of elements that influence thermal comfort. [ABSTRACT FROM AUTHOR]

Our research focuses on the analysis of extreme high maximum air temperature events (EXHTEs) in the Czech Republic in the period 1961-2010, their climatological characteristics, and on the identification of synoptic-scale circulation conditions conductive to them. EXHTEs are detected using the Weather Extremity Index (WEI) combining return periods of daily maximum air temperature, duration of events, and the extent of the affected area. We selected 37 EXHTEs as non-overlapping periods with the highest WEI. Some long EXHTEs were divided into several shorter synoptically homogeneous episodes. Using the two-level divisive clustering of 700 hPa air temperature and wind field anomalies, we obtained four main variants of synoptic-scale circulation conditions. The most frequent variant associated with extreme episodes is characterized by a westerly flow connected with a high pressure ridge extending northeastward from North Africa over Central Europe or with an anticyclone centered over the Central Mediterranean. The most extreme episodes occurred during the variant characterized by an easterly flow between a high pressure area to the northeast and a low pressure area to the southeast. [ABSTRACT FROM AUTHOR]

Projected changes of warm season (May-September) rainfall events in an ensemble of 30 regional climate model (RCM) simulations are assessed for the Czech Republic. Individual rainfall events are identified using the concept of minimum inter-event time and only heavy events are considered. The changes of rainfall event characteristics are evaluated between the control (1981-2000) and two scenario (2020-2049 and 2070-2099) periods. Despite a consistent decrease in the number of heavy rainfall events, there is a large uncertainty in projected changes in seasonal precipitation total due to heavy events. Most considered characteristics (rainfall event depth, mean rainfall rate, maximum 60-min rainfall intensity and indicators of rainfall event erosivity) are projected to increase and larger increases appear for more extreme values. Only rainfall event duration slightly decreases in the more distant scenario period according to the RCM simulations. As a consequence, the number of less extreme heavy rainfall events as well as the number of long events decreases in majority of the RCM simulations. Changes in most event characteristics (and especially in characteristics related to the rainfall intensity) depend on changes in radiative forcing and temperature for the future periods. Only changes in the number of events and seasonal total due to heavy events depend significantly on altitude. [ABSTRACT FROM AUTHOR]

Techniques for forecasting extreme temperature are mostly empirically based, using collections of statistics over a long period of time for a range of weather situations. In the article we have used the McKenzie's method for forecasting the minimum temperature and Callen and Prescott's method for forecasting the maximum temperature. Both of methods belong among the successfully and routinely used techniques. Main aim is to adjust these methods for routine application on aerodromes currently used by Czech Air Force. [ABSTRACT FROM AUTHOR]

The recent study of meteorological singularities in the Czech Republic—Řezníčková et al. (Theor Appl Climatol 88:179–192, 2007)—is supplemented with respect to findings concerning temporal stability of air temperature singularities. A long-term daily series at Prague-Klementinum is examined over 1881–2000, adopting the same statistical background for the detection of singularities. A procedure that reduces the dependence of results on the choice of a reference period is proposed. It is shown that nearly all temperature singularities found over the period since 1961 and/or the whole period of 1881–2000 are temporally unstable, and a lot of them should be treated as statistical properties of particular data samples (time periods) reflecting sampling variability rather than stable and recurrent anomalies related to distinct circulation patterns. The most important singularities are identified, occurring on 4 days in year only (around St. Médard’s Day, 8 June), and they are linked to intraseasonal variations in the occurrence of circulation patterns conducive to warm and cold temperature anomalies. A sharp increase (decrease) in the frequency of north (south) circulation types after 8 June leads to the most robust irregularity in the mean annual cycle of temperature. [ABSTRACT FROM AUTHOR]

Based on the mean daily values of air temperature, air pressure, and precipitation totals at 13 climatological stations within the territory of the Czech Republic in the period 1961–2002, a statistical analysis of “meteorological singularities” (i.e., calendar-dependent deviations from the mean annual variation for selected meteorological elements) was performed. At the 13 stations analysed, a total of 45 meteorological singularities (37 singularities in air temperature, 35 in air pressure, and 30 in precipitation) were found. The singularities detected correlate well with cases traditionally recognised in the Czech Republic as well as with the results of analyses performed for Germany. Despite the considerable variability of singularities in time and space, most of them are found across the entire territory of the Czech Republic and can be observed for the most part in all three elements processed. The majority of the singularities detected may be explained on the basis of circulation mechanisms, by relating them to a significantly higher occurrence of certain groups of synoptic situations characterised by anomalous temperature or precipitation effects. Cases of “competition” between singularities, when different singularities may occur on the same calendar day, were found. [ABSTRACT FROM AUTHOR]

Using temperature and pressure records from Czech meteorological stations and NCEP/NCAR reanalysis series, we tested for the presence of detectable nonlinearity in univariate and multivariate climatic time series. The method of surrogate data was utilized for nonlinearity detection – results of nonlinear prediction for the original series were compared to the results for series whose nonlinear structure was randomized. The prediction was done by means of local linear models in the reconstructed phase space. None or very weak nonlinearity was found in the single (univariate) series, and pressure series generally exhibited stronger nonlinearity than series of temperature (daily mean, minimum or maximum). Distinct nonlinearity was found in all tested multivariate systems, especially when both temperatures and pressures were used simultaneously to form the phase space. Nonlinearity tests were carried out for 30-year and 10-year-long datasets and nonlinear behavior was generally more apparent in the longer versions. In addition, the tested systems showed more substantial nonlinearity when the success of short-range prediction was used as the discriminating statistic; with an increase of the prediction time, detectable nonlinearity became weaker and it disappeared completely for long-term prediction. [ABSTRACT FROM AUTHOR]

Summary Two methods of estimation of the trend magnitude are compared: the parametric one (least-squares regression) with the non-parametric one (median of pairwise slopes). The comparison is carried out for seasonal and annual trends of ten climatic variables at a network of stations in the Czech Republic. We show that the difference between the two trend estimates is very small, falling well within the 95% confidence limits of the parametric estimate. The magnitude of the difference does not depend on the degree of normality of the distributions, with the exception of two variables, maximum temperature and precipitation, for which a slight dependence is observed. As a by-product, the normality of seasonal and annual means of the climatic variables is evaluated by the Kolmogorov-Smirnov one-sample test. [ABSTRACT FROM AUTHOR]

Corrosion of weathering steels in outdoor conditions has been observed since their pioneering applications in construction in the 1960s. Changing environmental conditions such as decreasing SO2 concentration and changes in temperature and relative air humidity affect the formation and development of a protective layer of corrosion products on the surface of these steels. The study compares the long‐term corrosion rates of weathering steels according to EN ISO 9224 with the measured rates for various environments in the Czech Republic and abroad, with a focus on sites with high concentrations of chlorides from de‐icing salts. When considering related uncertainties, the corrosion rate models provide estimates in a wide range, and in‐situ measurements can significantly improve corrosion loss predictions. The reliability of bridges made of weathering steels with a well‐developed protective layer is insignificantly affected by corrosion. However, low reliability levels may be experienced in critical details where for example leakage may damage the protective layer of patina. [ABSTRACT FROM AUTHOR]