Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 7

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
w słowach kluczowych:  Meteorological Aspects
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
Content available remote Storm-surges Indicator for the Polish Baltic Coast
Storm surges appear in the coastal zone of the Baltic Sea and, depending on row of factors, have different sizes, specifically characteristic for each region of the sea-coast. Observed climate changes are characterized with greater dynamics of weather phenomena. To compare the risk of storm surges to different areas, a new method had to be developed. Storm-surges indicator is used to compare the risks to the South Baltic water areas, varied along with conditions therein and the hydro meteorological and local conditions. The studies on the relations between the parameters and the occurrence of storm surges were carried out as well. The storm surges indicator “W” is related to the number of storm surges observed at the stations in the particular regions, the maximal wind velocity and the max sea level occurring during the same storm surges. The storm surges indicator was calculated for the period of 1955-2008 for the Polish coastal zone. The inten-tion is to use this indicator for research and forecasting purposes. Assessment of the tendencies and variability of the regional phenomena indicators in timescale prove occurrence of certain regional changes of hydrome-teorological conditions.
The use of methods of complex climatology, which treats climate as a many-year weather re-gime, made it possible to define the annual structure of weather states observed in seven Polish sea ports, i.e. Elbląg, Gdańsk, Hel, Łeba, Ustka, Kołobrzeg and Świnoujście. This work uses data originating from OGIMET and covers the period 2000-2009. Weather conditions that make port operation either difficult or even impossible are considered to be those when, during a day, we observe negative air temperatures, cloudiness, precipitation and strong winds at the same time. Once the frequency of occurrence of unfavorable weather conditions has been defined for the port operation then for each port a climatogram was drawn illustrating their frequency in the following decades of a given year. Weather conditions which are unfavorable for the work in Polish sea ports are observed only in autumn and winter, and during early spring; they are most frequent in the ports of Ustka and Gdańsk. Their annual fre-quency in none of the described ports exceeds 1% so the conditions in Polish sea ports may be regarded as fa-vorable for port operations. The worst weather conditions are observed in the last decade of December, third decade in January and in the second and third decades in February as well as i the first decade of April.
Content available remote Elements of Tropical Cyclones Avoidance Procedure
The updated version of the Cyclone II program was used for analyzing hundreds of cases where ships were facing dozens of developed cyclones. The program generates directions for navigators that are recommended for consideration before making decisions on passing around or avoiding tropical cyclones. Three specific situations were defined where a vessel may enter the area affected by a tropical cyclone, and its commander must consider three recommendations for safe passing of the cyclone: – vessel – cyclone encounter, where if on opposite course, the most effective is course alteration; – when the ship overtakes the cyclone, speed reduction is the most effective action; – when the vessel and the cyclone are on crossing routes (30 ÷ 90°), a slight decrease in speed or a slight course alteration or both actions can be effective.
Content available remote Baltic Navigation in Ice in the Twenty First Century
The Baltic Sea, even though not large in the global scale, is an important shipping lane. In winter, especially in the region of the Gulf of Bothnia, navigation is seriously obstructed by ice. The aim of this work was investigation of changes in the intensity of the obstruction by ice, caused by climate change in coming 90 years of the twenty first century. It was one of the first attempts of technical application of the global climate scenarios effects. It should be stressed, that the presented work results (as application of the climate scenarios), couldn’t be treated as forecast, as it is only the changes tendency assessment. The climate changes were examined as the changes in air temperature (adaptation of global emission models to regional scale) and atmospheric pressure gradient (model ECHAM5), according to three global scenarios B, A2 and A1B. The number of cases, in which Swedish and Finnish icebreakers assisted the ships, was assumed as the indicator of navigation obstruction by ice “K”. The severity of sea ice conditions was presented by the indicator “S”, calculated as the mean value of regional indices. The “S” is the function of the number of days with sea ice, observed at the stations in the particular regions and probability of the sea ice appearances. Relations between sea ice severity index “S” and regional climate parameters (monthly and annual air temperature and atmospheric pressure gradient ) were calculated for the calibration period of 1956-2004. Three models were build: model 1a. “thermal” (the dependence on the mean monthly temperature of July and December); model 1b. thermal “B” (the function of average annual air temperature and of the mean monthly December temperature) and model 2 “thermal zonal” (the dependence on the mean temperature of July and December and zonal component of air pressure gradient). The level of approximation was similar for the analyzed models (over 0,6). Calculation of the future (in XXI century) changes of indicator “K” was done according to three scenarios B, A1B and A2. The number of icebreakers’ assistance events should be lower than the one in the twentieth century. The lowest intensity of this decrease is estimated by model 2 and scenario A1Br1, the highest one – for model M1b and scenario B r1. Otherwise, the minimum value, calculated for the scenarios, is higher than in a period of 1956-2004. It means, that probably, the period with obstruction for navigation in ice could be longer, but not as severe as in the period of 1956-2004. The obstruction intensity could increase during the 21 century according to scenario B1r1, the same for empirical model 2. The similar tendency has been shown by scenario A1Br1 and by model 1a. Other models and scenarios estimated the decreasing trend up to 2100.
Content available remote Low Sea Level Occurrence of the Southern Baltic Sea Coast
The level of 440 cm is defined as the upper limit of low sea level. This value is also accepted as the warning level for navigation, according to the NAVTEX. The low sea levels along the southern Baltic Sea coast were analyzed in the years 1955 – 2005. Lowest values recorded ranged from 309 cm in Wismar to 370 cm in Kołobrzeg. The phenomenon was chiefly generated by hurricane like offshore winds. Extremely low levels were not frequent, their occurrence did not exceed more than 0,3% in Świnoujście and not more than 1% in Warnemünde. In summer months these phenomena occurred extremely seldom, they were more fre-quent in the western, than in the eastern part of the coast. Long-term variation and statistical analysis was pre-sented. Probability of low sea levels occurrence was calculated by Gumbel method and percentile distribution for 4 gauge stations was analyzed. The calculations revealed that, for instance, in Warnemünde once in 20 years the minimum sea level can be as low as 358 cm.
Briefly characteristic of m/f „Polonia" ferry has been presented. For the port of Ystad, topographical, hydro and meteorological conditions have been described. Moorings of the “Polonia” ferry at the port of Ystad have been discussed. Researches based on experts’ questionnaire and statistical methods of analyses have been exemplified. Finally there are some conclusions concerning improvements of ferries manoeuvres safety.
Content available A Required Data Span to Detect Sea Level Rise
Altimetric measurements indicate that the global sea level rises about 3 mm/year, however, in various papers different data spans are adopted to estimate this value. The minimum time span of TOPEX/Poseidon (T/P) and Jason-1 (J-1) global sea level anomalies (SLA) data required to detect a statisti-cally significant trend in sea level change was estimated. Seeking the trend in the global SLA data was per-formed by means of the Cox-Stuart statistical test. This test was supported by the stepwise procedure to make the results independent of the starting data epoch. The probabilities of detecting a statistically significant trend within SLA data were computed in the relation with data spans and significance levels of the above-mentioned test. It is shown that for the standard significance level of 0.05 approximately 5.5 years of the SLA data are required to detect a trend with the probability close to 1. If the seasonal oscillations are removed from the combined T/P and J-1 SLA data, 4.3 years are required to detect a statistically significant trend with a probability close to 1. The estimated minimum time spans required to detect a trend in sea level rise are ad-dressed to the problem of SLA data predictions. In what follows, the above-mentioned estimate is assumed to be minimum data span to compute the representative sample of SLA data predictions. The forecasts of global mean SLA data are shown and their mean prediction errors are discussed.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.