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Influence of computational grid resolution on the quality of forecasts of dangerous convection phenomena: a case study of August 11, 2017

Mazur Andrzej, Duniec Grzegorz

Meteorology Hydrology and Water Management. Research and Operational Applications

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2022

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Vol. 10, Iss. 2

106--114

EN

On August 11, 2017, a violent convection phenomenon took place in northwestern Poland, i.e., a storm combined with intense rainfall and hurricane winds. This paper presents an attempt to analyze this case by using the results of a numerical weather model, at grid spacings of 7 km, 2.8 km, and 0.7 km. Various convective indicators were analyzed to assess the nature of the event. The key question the authors try to answer is: „To what extent, if any, did a tenfold increase in resolution improve the quality of the numerical forecasts?” This question, however, has not been conclusively resolved. The most likely cause of this event was a supercell rapidly moving from south to northeast. This supercell's path has been mapped (qualitatively at least) by the Supercell Detection Index at all resolutions used. As the resolution increased, the forecasted maximum gusts also increased from 25 m/s in the domain with a resolution of 7 km to 35 m/s at a resolution of 2.8 km and up to about 50 m/s at the highest resolution of 0.7 km. A key conclusion is that the results of the model at a resolution of 2.8 km are much closer to reality than at 7 km. This effect did not pertain to differences between the 2.8 km and 0.7 km models. The latter increase in resolution did not significantly improve the quality of the forecast.

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Convective environment and development of a tornadic supercell in the Czech Republic on 24 June 2021

Sulik Sławomir

Meteorology Hydrology and Water Management. Research and Operational Applications

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2022

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Vol. 10, Iss. 1

60--72

EN

This study documents the atmospheric conditions and the development of a tornadic supercell in the Czech Republic, which occurred on the early evening on 24 June 2021. I used the data from the ERA5-reanalysis, vertical atmospheric sounding, synoptic map, and a Sentinel-2 satellite image to determinate the tornado route. As a result of the analysis, it can be concluded that the development of this tornadic supercell was caused by high CAPE values, amounting to around 5,000 J·kg-1, 0-6 km AGL wind shear 30 m·s-1, storm-relative helicity with values of 150 m2·s-2 and a wavy atmospheric front. The tornado occurred around 19:30 local time (1730 UTC) in the town Hrušky and moved north-east, reaching the town Hodonín. Based on satellite image derived from Sentinel-2, the widest point of the tornado reached 70 meters; it traveled a distance of about 20 kilometers and had a force of EF3/T5 on the Fujita/TORRO scale. As a result of this event, 6 people lost their lives, 200 people were seriously injured, and hundreds of buildings and cars were destroyed. Further studies on strong thunderstorm incidents in Europe are necessary for their better understanding and prediction.

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Point Defects in GaAs Photonic Crystals

Dissanayake S. E., Wijewardena Gamalath K. A. I. L.

International Letters of Chemistry, Physics and Astronomy

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2015

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Vol. 43

91--102

EN

Applying plane wave expansion method to one dimensional multilayer system formed from alternating layers of GaAs and air, a defect mode was artificially introduced by removing a GaAs layer at the centre of a supercell and the band structures and mode field distributions were obtained. The defect mode normalized frequency was 0.28. The parameters for developing a Febry-Perot filter in the visible frequencies are given. The point defects in a two dimensional square lattice formed from GaAs rods of radius 0.16a in air was created by removing one GaAs rod at the centre of a supercell and also by increasing the centre GaAs rod radius to 0.5a. The removal of the rod folded the band structure 25 times creating a localized evanescent defect mode. The increment of the centre GaAs rod radius led to five defect bands inside the band gap with one degenerate state creating a monopole, two quadrupoles and two hexapoles. Evolution of the defect modes with the variation of the radius of GaAs rod is also presented.