Ciklonpályák és frontok gyakoriságváltozása az elmúlt 50 évben az európai térségben = Frequency changes of cyclones and fronts in the last fifty years in the European region

Changes in large-scale circulation patterns over the North-Atlantic-European region are presented and analyzed for the 20th century. First, changes in decadal frequency of Hess-Brezowsky macrocirculation patterns (MCP) are evaluated between 1881 and 2000. Frequency of several MCP types increased or decreased considerably during these 120 years, which may be explained by large scale changes in circulation characteristics, e.g. by cyclone activity changes in the different regions. Therefore, cyclone center identification and cyclone tracks and intensity analysis have been accomplished on the base of the European Centre for Medium-range Weather Forecast (ECMWF) reanalysis datasets (ERA-40) on a 2.5º horizontal resolution grid for the period between 1957 and 2002. Results suggest that both the number of midlatitude cyclones and the cyclone activity increased considerably in the North-Atlantic-European region, especially, in the northwestern part of domain. Finally, significant frontal events (e.g. frontal precipitation and temperature changes) are also analyzed, i.e., how often and how intense they occurred in the last few decades, whether or not any trend may be detected in the Carpathian Basin

The Lagrangian Atmospheric Radionuclide Transport Model (ARTM) - development, description and sensitivity analysis

Atmospheric dispersion models are applied to describe and predict the dispersion of emitted plumes. Here, we describe the Lagrangian Atmospheric Radionuclide Transport Model (ARTM) 2.8.0 which was developed to simulate the atmospheric dispersion of the emissions of nuclear facilities under routine operation for regulatory purposes over annual time scales. ARTM includes a diagnostic wind field model and a particle dispersion model. It simulates size-dependent wet and dry deposition, plume rise and cloud shine of radioactive exhaust plumes in the simulation domain

The Lagrangian Atmospheric Radionuclide Transport Model (ARTM) — Sensitivity studies and evaluation using airborne measurements of power plant emissions

The Atmospheric Radionuclide Transport Model (ARTM) operates at the meso-γ-scale and simulates the dispersion of radionuclides originating from nuclear facilities under routine operation within the planetary boundary layer. This study presents the extension and validation of this Lagrangian particle dispersion model and consists of three parts: i) a sensitivity study that aims to assess the impact of key input parameters on the simulation results; ii) the evaluation of the mixing properties of five different turbulence models using the well-mixed criterion; and iii) a comparison of model results to airborne observations of carbon dioxide (CO2) emissions from a power plant and the evaluation of related uncertainties. In the sensitivity study, we analyse the effects of stability class, roughness length, zero-plane displacement factor and source height on the three-dimensional plume extent as well as the distance between source and maximum concentration at the ground. The results show that the stability class is the most sensitive input parameter as expected. The five turbulence models are the default turbulence models of ARTM 2.8.0 and ARTM 3.0.0, one alternative built-in turbulence model of ARTM and two further turbulence models implemented for this study. The well-mixed condition tests showed that all five turbulence models are able to preserve an initially well-mixed atmospheric boundary layer reasonably well. The models deviate only 6% from the expected uniform concentration below 80% of the mixing layer height except for the default turbulence model of ARTM 3.0.0 with deviations by up to 18%, respectively. CO2 observations along a flight path in the vicinity of the lignite power plant Bełchatów, Poland measured by the DLR Cessna aircraft during the CoMet campaign in 2018 allow to evaluate the model performance for the different turbulence models under unstable boundary layer conditions

Aerosol backscatter profiles from ceilometers: validation of water vapor correction in the framework of CeiLinEx2015

With the rapidly growing number of automated single-wavelength backscatter lidars (ceilometers), their potential benefit for aerosol remote sensing received considerable scientific attention. When studying the accuracy of retrieved particle backscatter coefficients, it must be considered that most of the ceilometers are influenced by water vapor absorption in the spectral range around 910 nm. In the literature methodologies have been proposed to correct for this effect; however, a validation was not yet performed. In the framework of the ceilometer intercomparison campaign CeiLinEx2015 in Lindenberg, Germany, hosted by the German Weather Service, it was possible to tackle this open issue. Ceilometers from Lufft (CHM15k and CHM15kx, operating at 1064 nm), from Vaisala (CL51 and CL31) and from Campbell Scientific (CS135), all operating at a wavelength of approximately 910 nm, were deployed together with a multi-wavelength research lidar (RALPH) that served as a reference. In this paper the validation of the water vapor correction is performed by comparing ceilometer backscatter signals with measurements of the reference system extrapolated to the water vapor regime. One inherent problem of the validation is the spectral extrapolation of particle optical properties. For this purpose AERONET measurements and inversions of RALPH signals were used. Another issue is that the vertical range where validation is possible is limited to the upper part of the mixing layer due to incomplete overlap and the generally low signal-to-noise ratio and signal artifacts above that layer. Our intercomparisons show that the water vapor correction leads to quite a good agreement between the extrapolated reference signal and the measurements in the case of CL51 ceilometers at one or more wavelengths in the specified range of the laser diode\u27s emission. This ambiguity is due to the similar effective water vapor transmission at several wavelengths. In the case of CL31 and CS135 ceilometers the validation was not always successful. That suggests that error sources beyond the water vapor absorption might be dominant. For future applications we recommend monitoring the emitted wavelength and providing “dark” measurements on a regular basis

Uncertainties in the simulation of XCO2 plumes from power plant emissions: A comparison between 6 high-resolution atmospheric transport models

Power plants are a major source of CO2 globally. Although their emissions are routinely monitored in many countries especially in the developed world, these numbers are often not publicly available and a complete global record is still far from reality. An important goal of Europe's planned Copernicus CO2 satellite mission CO2M is therefore to provide an independent quantification of power plant emissions worldwide. Emissions may be estimated from satellite XCO2 observations by simulating the plumes with an atmospheric transport model and finding those emissions that minimize a cost function of the differences between simulation and observations. Here we present a comparison of CO2 plume simulations from six high-resolution models, three Large Eddy Simulation models, two mesoscale Eulerian models, and one Lagrangian particle dispersion model. Simulations were conducted for two large coal-fired power plants, Belchatow in Poland and Jänschwalde in Germany, which were extensively observed with aircraft in situ and remote sensing measurements during the CoMet campaign in May-June 2018. The observations provide a unique opportunity to study the capability of the models to simulate such plumes in a realistic manner and to design optimal modelling and emission quantification strategies. The Belchatow plume was sampled under highly convective and turbulent conditions whereas the Jänschwalde plume was observed in a more stable weather situation. The models are able to reproduce these differences by simulating a highly structured turbulent plume for Belchatow and a more Gaussian-shaped plume for Jänschwalde. However, the models differ in many details including the horizontal and vertical spread of the plumes, suggesting that in addition to resolution the specific choices of turbulence and advection scheme have a significant impact on the results. Our findings suggest that estimating emissions from individual images is particularly challenging for turbulent plumes. Since turbulence intensity evolves with the build-up of the convective boundary layer, a satellite overpass well before noon would likely be an advantage