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Convective and non-convective wind gusts in Poland, 2001-2015

Kolendowicz L., Taszarek M., Czernecki B.

Meteorology Hydrology and Water Management. Research and Operational Applications

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2016

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Vol. 4, iss. 2

15--21

EN

The main aim of the article is to present the climatology of the peak wind gust frequency in Poland caused by the impact of both atmospheric circulation and the presence of thunderstorm clouds. Nine meteorological stations for the measurement period of 2001-2015 were taken into account. Only SYNOP reports with a peak wind gust higher or equal to 15 m s-1 in thunderstorm and non-thunderstorm days are considered in this study. The results indicate that the highest threat in terms of frequency and strength of peak wind gusts due to convection occurs in July. In winter, thunderstorms are rare, but if they occur, about 80% of them produce wind gusts exceeding a threshold of 15 m s-1. Peak wind gusts in a non-thunderstorm days are the highest and the most frequent in January, and are at a minimum during summer. Comparing both types, peak wind gusts during days with a thunderstorm were on average stronger than those without an involved convection. This indicated that convection was an important factor in enhancing the strength of a wind gust. The highest value in our base was 34 m s-1, recorded in Kraków on 8th July 2015 within the occurrence of a severe thunderstorm, while the highest value in a day without a thunderstorm was 33 m s-1, recorded in Łódź on 31st January 2002.

2

Regionalizacje, typologie i wyznaczania sezonów klimatycznych z zastosowaniem analizy skupień

Bednorz E., Kolendowicz L., Bielec-Bąkowska Z., Bokwa A., Żelazny M., Kicińska B., Lewik P., Nowosad M., Ustrnul Z.

Przegląd Geofizyczny

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2003

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Z. 1-2

11-32

EN

In the paper are presented examples of regionalisation, typology and delimiting climatic seasons, completed with chosen cluster analysis methods: K-means, Ward's and Wroclaw dendrite. The methods were used to distinguish atmospheric circulation regions on the Northern hemisphere, thunderstorm regions and sulphur dioxide pollution regions in Poland, and snow-cover regions in North-Western Poland. Moreover, atmospheric circulation seasons, skiing seasons and thermal seasons were defined. The methods were also used for typology of thermal structure in the air layer near the ground, and for an attempt to define the relations between physical-chemical features of precipitation and meteorological conditions. The presented examples prove that it is possible to approach the problems of regionalisation and typology in climatology in a new way, namely without a priori assumptions, without imposing at the beginning the elements determining the spatial pattern of a phenomena. Additionally, it is very important that such an analysis requires from the researcher independence, responsibility and lot of criticism while interpreting the results, especially using non-hierarchical methods. Finally, the presented methods allow us to obtain the image of both spatial and temporal differentiation of chosen elements.

3

Zmniejszenie częstości dni z burzą na przełomie czerwca i lipca w Poznaniu w latach 1961-1990

Kolendowicz L.

Przegląd Geofizyczny

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1999

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Z. 1-2

73-78

EN

The study seeks to provide an explanation of why days with thunderstorms are less frequent at the close of June and the beginning of July in Poznań. Use was made of daily data from the Poznań- Ławica weather station of the Institute of meteorology and Water management (IMGW) from the years 1961-1990 on the occurrence of days with thunderstorms and diurnal means of air temperature and vapour pressure. The results of the study suggest that one of the immediate causes of the lower frequency of days with thunderstorms at the close of June and the beginning of July in Poznań in the period concerned is the increase in the number of days with mean diurnal temperature and vapour pressure lower than the lowest means of those meteorological elements for days with thunderstorms.