National projects

Sudden stratospheric warmings (SSWs) are the most significant perturbations of the wintertime stratosphere. SSWs affect even the ionosphere; they can modify propagation of GNSS/GPS signals and thus precise positioning. However, the impact of SSWs on the midlatitude ionosphere is little understood. Therefore, our project aims to identify the chain of processes during SSWs, from the stratosphere through mesosphere and lower thermosphere up to the midlatitude ionosphere. Our goal is to describe the impact of SSWs, including coupling mechanisms such as changes in gravity wave activity, which are likely the main channel for SSWs effects on the midlatitude ionosphere. We will also search for the optimal parameters defining SSWs for ionospheric studies, and investigate gravity wave propagation from the stratosphere trough mesosphere into the midlatitude ionosphere. The project will rely on our measurements, international observation databases, modeling, and the latest meteorological reanalyses, whose quality at higher altitudes will be verified.
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Relationships between weather and human health are very complex. Many studies have shown a typical seasonal pattern of mortality, with its maximum in the cold period and minimum in summer. It remains unclear, however, to what extent seasonality of mortality can be explained by direct effects of winter weather and to what extent other factors are important, such as incidence of acute respiratory diseases (until recently, mainly seasonal influenza epidemics). This topic has become even more relevant in connection with the ongoing COVID-19 pandemic, which caused unprecedented excess mortality in 2020 and 2021. The aim of the project is to assess historical connections between weather variability, seasonal patterns of mortality, and the occurrence of acute respiratory infections in temperate climate conditions. Special emphasis will be given to how these patterns have been affected by the COVID-19 pandemic.
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Precise monitoring of ionospheric conditions to establish accuracies of GNSS measurements mainly during the periods with the MSTID and ionospheric scintillation occurrence. Development of actual MSTID effects mitigation algorithms for implementation into the GNSS receiver firmware to lower positioning errors.
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Long-term changes (trends) in short-term (day-to-day to intraseasonal) variability of temperature and precipitation are examined in the Northern Extratropics, both in the observed data and in outputs of global and regional climate models. Various characteristics of variability, which provide complementary information, are analyzed (standard deviation, persistence, dayto- day variations, transition probabilities, lengths of dry and wet spells). Their climatologies and trends are compared between different dataset types (station, gridded, reanalysis) with the aim to identify biases specific to individual dataset types. We also focus on mechanisms governing the short-term variability, and the day-to-day temperature changes in particular, in which atmospheric fronts are likely to play a role. We validate the short-term variability in climate model outputs and evaluate its future projections by models. Finally, we attempt to find out whether the anthropogenic climate change is already manifested in the recently observed changes of variability
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The increasing concentration of greenhouse gases affects the troposphere but even more the higher levels of the atmosphere, where it induces cooling. The first scenario of long-term trends in the upper atmosphere (mesosophere-thermosphere-ionosphere) was created by an international team in 2006 (Laštovička et al., 2006, Science). It has been improved but still it is not connected with trends in the stratosphere. Until recently the trends in the stratosphere and upper atmosphere were studied separately. The trends are affected also by other drivers, not only by greenhouse gases (mainly CO2), which change in time. The project is therefore focused on various aspects of trends in the stratosphere to improve possibilities of their comparison and joining with trends in the upper atmosphere, then on removing new problems in studying ionospheric trends, on specification of temporally varying roles of various non-CO2 trend drives, and on the main aim of the project, creation of the first joint scenario of long-term trends in the stratosphere-mesosphere-thermosphere-ionosphere system.
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Weather and climate extremes are associated with large impacts on society and environment, and frequency of some of these extremes has increased and/or is projected to increase in a future climate. It is important to better understand physical mechanisms leading to extremes, their mutual links, and how they are reproduced in climate models. The project deals with temperature and precipitation extremes in Europe, with focus on warm season. The main aims are to (i) examine the role of atmospheric circulation and land-atmosphere coupling in initiating development of temperature extremes and supporting their persistence in observed climate and ERA-5 reanalysis, including the study of links to extremes of precipition and other variables, (ii) analyze spatial patterns of differences between individual driving mechanisms (advective, radiative, and land-surface factors) in key regions of Europe, and (iii) evaluate ability of current high-resolution climate models to reproduce the driving mechanisms of extremes and their spatial patterns. This represents an important step towards better understanding credibility of climate model outputs, and for further model improvements.
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High-impact winter weather significantly affects both nature and society. Its severity may not decrease despite the growing global temperature, due to changes in atmospheric circulation in a future climate. The proposed project aims to expand knowledge of high-impact winter weather and, specifically, to evaluate threats associated with winter extremes that should be included in the preparation of adaptation strategies. The project aims (i) to analyse temporal and spatial variability of observed high-impact weather events over central Europe and their links to atmospheric circulation and other variables, (ii) to evaluate the ability of current EURO-CORDEX regional climate models to simulate high-impact weather events and their links to circulation, and (iii) to assess changes of those events in possible future climates in two sets of model projections (forced by RCP 4.5 and RCP 8.5 concentration pathways) for two periods (2021–2050, 2071–2100). Added value of studying compound extreme events (e.g. the combination of low temperature and high wind velocity) will be assessed.
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Links between weather and human health have been a subject of increased attention recently, but in spite of growing knowledge, many issues remain open. The main aims of the project are to (i) improve methodological aspects of modelling weather-related morbidity and mortality in the population of the Czech Republic using advanced statistical tools; (ii) identify susceptible population groups and examine modifying effects of characteristics such as age, health disorders, and education; (iii) identify differences in the susceptible population groups between urban and rural regions and in relation to socioeconomic status; and (iv) examine changes in weather-related morbidity and mortality over recent decades and their links to changes in the population structure, its socioeconomic status, diseases prevalence, and environmental factors. The project makes use of nationwide cause-specific mortality and morbidity data sets, and its results will allow for better understanding of the weather-to-human health links, which is necessary for preventing excess deaths.
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The main aim is development and testing of new features of the parametric spatial weather generator, so that it can be used to produce more realistic gridded weather series representing present and future climate conditions on various spatial and temporal scales. In completing the project aims (A) The surface weather generator will be linked with generator of modes of circulation variability, which will allow to account for the advection of spatial surface weather patterns and effect of the larger scale circulation on weather. (B) The nesting scheme will be developed to condition the high-resolution generator run on the smaller area with shorter time step on the lower-resolution generator. (C) The generator parameters will be modified with climate change scenarios, which will be derived from the Regional Climate Model simulations and account also for changes in temporal circulation variability and spatial weather variability. The generator will be validated using multiple climatological indices and its performance compared with other available gridded surface weather series.
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