Maksymalne prędkości wiatru w Polsce

W ostatnich kilkunastu latach w Polsce obserwuje się, że ryzyko zagrożenia życia i mienia przez wiatr o dużych prędkościach jest coraz większe. Tę trudną tematykę podjęto więc z takim przesłaniem i w takim celu, by ze względu na charakter maksymalnych prędkości wiatru jako zjawiska niosącego zagrożenie: • poznać jego genezę oraz określić meteorologiczne warunki ich występowania w Polsce, • określić ich wartości i zróżnicowanie terytorialne, • określić prawdopodobieństwo występowania maksymalnych prędkości wiatru w Polsce, • opracować dla warunków krajowych skalę tych prędkości i określić prędkość progową, która w naszych warunkach klimatycznych może już spowodować wymierne, niekorzystne skutki działania, • opracować mapy ryzyka występowania silnego wiatru o określonej prędkości dla obszaru Polski. W tym przypadku przez mapy ryzyka należy rozumieć mapy ilustrujące zgodnie z przyjętym kryterium obszary o największym prawdopodobieństwie występowania prędkości wiatru stanowiących największe zagrożenie.

Aim of this study is to deepen knowledge of the occurrence of maximum wind speed in Poland being a threat to the economy and society. The work was undertaken also because the knowledge of the structure of hurricane wind speeds is insufficient in the face of contemporary needs and expectations. In order to fulfill this objective primarily suitable criterion of maximum wind speed was adopted, meteorological conditions of their occurrence were specified, their size and diversity within the country were determined as well as the probability of occurrence of maximum wind speed in Poland; appropriate scale of maximum wind speed in Polish conditions was developed and the appropriate threshold values of dangerous wind speed were adopted. On the basis of maximum wind speed gusts for 35 years (1971-2005) it was found that the presence of high wind speeds in Poland is linked to three genetically different meteorological situations: 1. cyclonic activities related to the general circulation of the atmosphere; 2. foehn situations in mountainous regions; 3. presence of meteorological conditions appropriate to create small-scale vortices of air – thermal storms, whirlwinds and squalls. Data analysis shows that the greatest increase in wind speed are reached during hurricane types of circulation according to the classification of J. Litynski: NWc, Wc, SWc, Nc in the country, and NWo, SEc and Sc – interacting mainly in three regions of the country. In case of any of these circulation types, with the horizontal pressure gradient of at least 1,5 hPa/100 km, there is a high probability of the emergence of strong, gusty wind. The strongest winds, associated with the distinguished types of circulation (named hurricane) are the ones for which the lower speed limit is empirically derived value ≥ 11 m/s. The first noticeable damage is caused when the wind speed is over or equal 17 m/s. In order to identify damage with wind speed, a specially designed seven-step scale of maximum wind speed occurring in Poland from 11 m/s (40 kph) to 70 m/s (251 kph) was developed. In the horizontal pressure gradient of ≥ 4 hPa/100 km wind gusts reach speed of 35-40 m/s. A characteristic feature of the maximum wind speed is their presence in cycles lasting for hours, which may occur on average 11 times a year. The longest cycle lasted for 192 hours. The most devastating cyclones are forming over the area of the eastern coast of North America. Trends analysis of hurricane circulation types frequency shows no statistically significant changes in relation to their current pattern, except for the type Sc in mountain areas and highlands. This means the future increase in the emergence of lowpressure centers from the Po Plain usually bringing heavy rain flooding in parts of the upper Vistula and the Oder rivers, and the influx of tropical air masses causing the creation of mesoscale convective systems as a symptom of future whirlwinds and squalls. Regions of the country with the largest annual probability of occurrence of maximum wind speeds are generally two areas of Poland: east part of the Slowinskie Coast as well as the Silesian and the Żywiec Beskids. It is also noted in the Suwalki Region and Mazovia. On the Polish territory, every year, there are observed wind speeds gusts at least 17 m/s, causing greater