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.
In this paper, the mechanism and model-representation of a late-spring severe blizzard event on eastern Romania are studied. The mechanism relies on the coupled contribution of the tropospheric ageostrophic circulations associated to jet streaks. These circulations: (1) interact under local and regional forcing (sea surface temperature, topography and latent heat) and (2) feedback on enhancing an upper-level jet’s secondary streak, leading to a persistent, severe event. The enhanced secondary jet streak appears only for developing systems that lead to extreme impact, as shown by 40 years of knowledge of late-spring severe blizzards over the area. It is shown that actual regional high-resolution models are able to represent the occurrence and the mechanism of late-spring severe blizzard events, thus increasing the confidence on their ability to represent current and future climate extreme variability. Understanding the preconditioning of dynamic and thermodynamic processes indicated by this analysis could be useful in supporting the operational forecast analysis.
Significant progress in tornado research and management can be claimed over the last few decades worldwide. However, tornado forecasting and warning continue to be permanent challenges for most European national meteorological services because they require particular skills and experience. Moreover, tornado warnings may generate panic. Therefore, one can remark that the main difficulties are related to (1) forecasting the tornado genesis, and (2) finding the most efficient way to communicate to the general public the possibility of tornado occurrence. This article presents the main characteristics of two convective events that occurred in Romania in order to emphasize the similarities and disparities between the tornado event (30 April 2019) and the non-tornado event (6 May 2019), from the warning perspective. Further, we investigate, for the first time in Romania, the general public’s comprehension, risk perception and reactions regarding the tornado events. The survey performed in 2020 emphasized that the Romanian public is able to recognize tornadoes (60%), understand the risks (over 80%), can manage the panic (over 70%), and is rather desirous to receive clear (over 90%) and real-time (95%) tornado warnings. The lessons learned may support the further development of tornado forecasting and warning procedures, and foster the public’s awareness related to tornado events.
<p>The general interest in tornado studies has been stimulated by scientific challenges, such as a better understanding of their genesis and development, and by applications and practical issues, such as forecast, building engineering, and risk analysis.&#160;</p><p>This context justifies the interest in reconstructing tornado characteristics based on different approaches. The recently released ERA5 reanalysis data set at 31&#8201;km-horizontal resolution, and hourly temporal resolution holds significant potential for many climate applications.&#160;</p><p>In this paper, the tornado environments in Romania between 1981-2020 are reconstructed using a series of thermodynamic and kinematic parameters (e.g., 0-1 km bulk wind shear, 0-6 km bulk wind shear, 0-500m mixed-layer CAPE, ML WMAX*SHEAR) calculated based on ERA5 data. A previous paper on the climatology of tornadoes in Romania showed that in the 1980s there was a minimum in the tornado activity (1 tornado report) followed by a period with a large number of reports (138 reports, approximately 4 tornadoes per year). The aim of the paper is twofold. First, we want to investigate the changes in the occurrence of tornado environments in Romania and thus understand if the minimum in tornado reporting in 1980 is due to tornadoes being ignored by the researchers and meteorologists (and reported as swerve wind events) or natural variability. Second, to study the spatial and temporal variability of the tornadoes in Romania in relation to large-scale patterns. The results show that the frequency of occurrence of tornado environments has increased in Romania since 1980, especially over southeastern Romania.&#160;</p><p>This work has been financed within project &#8222;Dezvoltarea Centrului de Competen&#539;&#259; pentru Adaptarea Comunit&#259;&#539;ilor Locale la Schimb&#259;rile Climatice prin parteneriate de tip public-privat &#238;n domeniul CDI&#8221; cod 3/16.11.2022 finan&#539;at prin Planul Na&#539;ional de Redresare &#537;i Rezilien&#539;&#259; Apel nr. PNRR-III-C9-2022 &#8211; I5"</p>
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