Clear air turbulence (CAT) poses a significant threat to aviation. CAT usually occurs in the lower stratosphere and the upper troposphere. It is generally associated with large scale waves, mountain waves, jet streams, upper-level fronts and tropopause folds. Aircraft can experience CAT when flying in proximity of a tropopause fold. To better understand and diagnose tropopause fold- associated CAT we selected a series of cases from among those reported by pilots between June 2017 and December 2018 in the Romanian airspace. Data on turbulence were used in conjunction with meteorological data, satellite imagery, and vertical profiles. Additionally, a set of indices as Ellrod, horizontal temperature gradient, Dutton, and Brown were computed to diagnose CAT associated with tropopause folding. These indices were also analyzed to test the physics mechanisms that may explain the occurrence of severe turbulence. Results show that out of the 420 cases announced by pilots, severe turbulence was reported in 80 cases of which 13 were associated with tropopause folding.
The goal of this article is to investigate how the Romanian air space would be affected by a potential large eruption of Vesuvius volcano. In order to characterize the potential impact of such an event on the Romanian air space, we simulated the ash plume transport from a hypothetical explosive eruption with a significant magnitude, that is, Volcanic Explosivity Index (VEI 4). The volcanic ash cloud transport towards Romania was described by using the mass distribution from the HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) for Volcanic Ash numerical model. To assess the dominant air circulation types, an adaptation of the WetterLagenKlassification (WLK) classification scheme was used. The results emphasized that a long-wave trough and southwesterly flow in upper levels would favour the direct transport of volcanic ash cloud towards the Romanian air space. Non-negative matrix factorization method has been used to identify the atmospheric layer with the maximum values of mass. The simulation results reveal that the maximum values of averaged mass were obtained at an altitude around 7 km.
This study is focused on finding the hypothetical conditions under of which the Romanian air space could be affected by a volcanic ash-like pollutant originating from Etna Volcano. We describe the plume transport behaviour, on its way to Romania, using the mass loading distribution displayed by the HYSPLIT (Hybrid Single Lagrangian Integrated Trajectory) model output. From the WLK (Wetterlagen-klassifikation) catalogue we have specific day sequences showing more than three days of a south-western circulation with a wet anticyclonic pattern over Romania. The resulting 24 cases in a period spanning more than a decade (2004-2014) displayed that the chances of contamination would be better for a quiescent environment around Etna’s summit. There were found ten cases in quiescent atmosphere and only four cases in windy atmosphere with Romanian air space contamination. Although it was not possible to determine the effective concentration of the fine ash pollutant it was possible to isolate the mass loading distribution in time. As the study cases displayed one order of magnitude difference between mass loading distributions it became obvious that the behaviour of the mass loading distribution in time has a directly dependence on the environmental stratification of the Etna’s summit atmosphere.
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