No abstract

Abstract. Mediterranean cyclones are extratropical cyclones, typically of smaller size and weaker intensity than other cyclones that develop over the main open ocean storm tracks. Nevertheless, Mediterranean cyclones can attain high intensities, even comparable to the ones of tropical cyclones, and thus cause large socioeconomic impacts in the densely populated coasts of the region. After cyclogenesis takes place, a large variety of processes are involved in the cyclone’s development, contributing with positive and negative potential vorticity (PV) changes to the lower-tropospheric PV anomalies in the cyclone center. Although the diabatic processes that produce these PV anomalies in Mediterranean cyclones are known, it is still an open question whether they occur locally within the cyclone itself or remotely in the environment (e.g., near high orography) with a subsequent transport of high-PV air into the cyclone center. This study introduces a Lagrangian method to determine the origin of the lower-tropospheric PV anomaly, which is applied climatologically to ERA5 reanalysis and to 12 monthly simulations, performed with the integrated forecasting system (IFS) model. We define and quantify so-called “cyclonic” and “environmental” PV and find that the main part of the lower-tropospheric PV anomaly (60 %) is produced within the cyclone, shortly prior (−12 h) to the cyclones' mature stage. Nevertheless, in 19.5 % of the cyclones the environmental PV production near the mountains surrounding the Mediterranean Basin plays a significant role in forming the low-tropospheric PV anomaly and therefore in determining the intensity of these cyclones. The analysis of PV tendencies from the IFS simulations reveals that the major PV production inside the cyclone is typically due to convection and microphysics, whereas convection and turbulent momentum tendencies cause most of the positive PV changes in the environment.

Abstract. Mediterranean cyclones are extratropical cyclones, typically of smaller size and weaker intensity than other cyclones that develop over the main open ocean storm tracks. Nevertheless, Mediterranean cyclones can attain high intensities, even comparable to the ones of tropical cyclones, and thus cause large socio-economic impacts in the densely populated coasts of the region. After cyclogenesis takes place, a large variety of processes are involved in the cyclone’s development, contributing with positive and negative potential vorticity (PV) changes to the lower-tropospheric PV anomalies in the cyclone center. Although the diabatic processes that produce these PV anomalies in Mediterranean cyclones are known in principle, it is still an open question whether they occur locally within the cyclone itself or remotely in the environment (e.g., near high orography) with a subsequent transport of high-PV air into the cyclone center. This study introduces a Lagrangian method to determine the origin of the lower-tropospheric PV anomaly, with an average amplitude of 1.2 PVU, relative to the tracks of cyclones identified in ERA5 reanalyses. We define and quantify so-called "cyclonic" and "environmental" PV and find that the main part of the lower-tropospheric PV anomaly (60 %) is produced within the cyclone, shortly prior (-12 h) to the cyclones mature stage. Nevertheless, in 10 % of the cyclones the environmental PV production near the mountains surrounding the Mediterranean basin plays the dominant role for the low-tropospheric PV anomaly, and therefore the intensity of the circulation associated with these cyclones. An additional investigation of IFS simulations with detailed output from physical parameterizations reveals that the major PV production inside the cyclone is typically due to convection and large-scale microphysics, whereas convection and turbulent momentum tendencies evoke most of the positive PV changes found in the environment.

Combustion of fossil fuels is one of the most important source of energy. However low carbon politics and environmental commitments, affects developing combustion and co -combustion technologies. Utilization of biomass fuels can be answer for new challenges, although more research on effective utilization of these fuels are needed. Nowadays, combustion of biomass fuels, especially straw, causes many technical problems, mainly slagging formation, fouling of heat exchangers inside combustion chamber and insufficient fuel burnout. This paper focuses on analysis of biomass combustion. Better knowledge of behavior during biomass combustion may help to optimization of PF (Pulverized Fuel) boiler of and avoid some technical problems. The results of investigation shows that temperature and oxygen concentration in reactor play significant role in process of devolatilization and char burnout. For instance during char burnout experiments at temperature 850⁰C at 14% oxygen concentration after 200 ms more than 80% of mass loss were achieved. Compared to 700⁰C at 14% oxygen concentration this same level of mass loss were completed after 500 ms. Experiments performed on Isothermal Plug Flow Reactor (IPFR) at Institute of Energy Process Engineering and Fuel Technology (IEVB) at TU Clausthal were a part of project between IEVB and the Karlsruhe Institute of Technology (KIT) in Germany. AbstraktSpalování fosilních paliv je jedním z nejdůležitějších zdrojů energie. Nicméně nízkouhlíková politika a environmentální závazky ovlivňují vývoj spalovacích a spolu-spalovacích technologií. Využívání paliv z biomasy může být odpovědí na nové výzvy, i když je zapotřebí více výzkumu o efektivním využití těchto paliv. V současné době spalování paliv z biomasy, zejména slámy, způsobuje řadu technických problémů, zejména tvorbu strusky, zanášení výměníků tepla uvnitř spalovací komory a nedostatečné vyhoření paliva. Tento příspěvek se zaměřuje na analýzu spalování

<p>Mediterranean cyclones are extratropical cyclones, typically of smaller size and weaker intensity than other cyclones that develop over the main open ocean storm tracks. Nevertheless, Mediterranean cyclones can attain high intensities, even comparable to the ones of tropical cyclones, and thus cause large socio-economic impacts in the densely populated coasts of the region. After cyclogenesis takes place, a large variety of processes are involved in the cyclone’s development, contributing with positive and negative potential vorticity (PV) changes to the lower-tropospheric PV anomalies in the cyclone center. Although the diabatic processes that produce these PV anomalies in Mediterranean cyclones are known, it is still an open question whether they occur locally within the cyclone itself or remotely in the environment (e.g., near high orography) with a subsequent transport of high-PV air into the cyclone center. This study introduces a Lagrangian method to determine the origin of the lower-tropospheric PV anomaly, which is applied climatologically to ERA5 reanalysis and to 12 monthly simulations, performed with the IFS model. We define and quantify so-called "cyclonic" and "environmental" PV and find that the main part of the lower-tropospheric PV anomaly (60%) is produced within the cyclone, shortly prior (-12 h) to the cyclones’ mature stage. Nevertheless, in 19.5% of the cyclones the environmental PV production near the mountains surrounding the Mediterranean basin plays a significant role in forming the low-tropospheric PV anomaly, and therefore in determining the intensity of these cyclones. The analysis of PV tendencies from the IFS simulations reveals that the major PV production inside the cyclone is typically due to convection and microphysics, whereas convection and turbulent momentum tendencies evoke most of the positive PV changes in the environment.</p>