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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Every spacecraft immersed in space plasma environments significantly distorts the local conditions making measurements of the unperturbed plasma properties very difficult. Electron measurements are mostly affected by the spacecraft charging and by emissions of secondary electron populations. The main objective of the present project is to study the plasma interactions with the Solar Orbiter spacecraft and their effects on 3D electron velocity distribution functions (eVDFs) acquired by the SWA/EAS plasma detectors. We will study the local spacecraft environment by means of numerical PIC simulations and model the changes in the eVDFs as seen by the EAS sensors with respect to unperturbed ambient conditions. By comparison of the simulation results with real SWA/EAS measurements we will aim to distinguish true electron perturbations naturally caused by local kinetic plasma processes from those of the spacecraft origin. Finally, in cooperation with the instrument team, we will develop enhanced data calibration techniques and implement them to public SWA/EAS scientific data products.
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Heat waves are considered as one of the largest hazards related to climate change. Initial studies using one-dimensional station data were gradually supplemented by papers employing more advanced two-dimensional products, i.e. station data interpolated into a regular grid. They allowed capturing spatial patterns of heat waves but lacked the ability to identify vertical air mass characteristics. Besides radiative heating of the surface during clear-sky conditions, heat wave characteristics are also determined by a horizontal advection and an adiabatic heating during air subsidence – the processes that require data from free atmosphere to be analysed. In order to advance in knowledge of heat waves’ mechanisms, we propose this project which aims to study atmospheric circulation and land–atmosphere coupling as a joint driver governing heat waves in three-dimensional space. The state-of-the-art ERA5 reanalysis and CORDEX regional climate models will be employed to achieve project aims defined below.
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Solar Orbiter, an ESA-NASA mission to study physical processes in the solar corona and in the solar wind, was successfully launched in February 2020. The Time Domain Sampler (TDS) module on this spacecraft has been developed at the Institute of Atmospheric Physics (IAP) in Prague. It has been designed for electromagnetic measurements between 1 kHz and 200 kHz. The proposed project is focused on the scientific exploitation of the data from TDS taken during an early operational phase when the spacecraft encounters several perihelia. The effort will be focused on the study of higher frequency plasma waves, e.g. Langmuir and ion acoustic waves, resolved in the TDS data, with the objective to understand their origin, dynamics and interaction with plasma particles. We will also study the properties of dust grains impacting the spacecraft based on their characteristic signatures in electric field measurements. The project includes the planning and preparation of instrument operations and updates to TDS flight software.
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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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