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O reżimie wiatru przyziemnego w Zachodniej Antarktyce

Lagun V. E., Ivanov N. E., Jagovkina S. V.

Problemy Klimatologii Polarnej

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2007

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nr 17

7-30

PL

Statystyczna analiza prędkości wiatru przyziemnego została przeprowadzona w oparciu o dane z obserwacji terminowych (4 razy w ciągu doby) przeprowadzonych na stacji Russkaya (Antarkyda Zachodnia). Wykorzystano szeregi obserwacyjne od 1980 do 1990 roku. Oceny parametrów zmienności międzyrocznej, rytmiki rocznej, procesów skali synoptycznej i przebiegu dobowego dokonano w kategoriach wektora oczekiwania matematycznego (przestrzeni probabilistycznej) i inwariantów tenzorów dyspersji i gęstości spektralnej oraz korelacji okresowej wektorów procesu losowego. Dla parametryzacji zmienności skali synoptycznej wykorzystano model losowego procesu impulsowego w postaci kolejnych następstw "sztormów" i "okien pogody". "Sztorm" oznacza przewyższenie zadanego poziomu prędkości wiatru, a "okno pogody" - odstęp czasu między dwoma kolejnymi sztormami. Dla opisania statystyki zjawisk skali synoptycznej utworzono szeregi czasowe charakterystyk inten-sywności sztormów oraz czasu trwania sztormów i okien pogody. Poziomy progowe wyznaczono na podstawie analizy kwantyli jako kryteria graniczne niebezpiecznych lub szczególnie niebezpiecznych warunków pogodowych. Zmienność skali synoptycznej najbardziej celowo jest analizować w szeregach centrowanych względem wartości średnich rocznych oraz względem rocznego przebiegu wartości średnich miesięcznych. Modulację sezonową i zmienność międzyroczną intensywności procesów skali synoptycznej można opisać za pomocą szeregu czasowego dyspersji wewnątrzmiesięcznej prędkości wiatru, jako wyniku okresowych korelacji zachodzących w procesie losowym.

EN

Statistical analysis of surface wind velocity is executed on the base of current observations (six-hourly) at Russkaya station, located in Western Antarctic for period from 1980 to 1990. Estimates of inter-annual variability parameters, parameters of annual rithmics, processes of synoptic scale and diurnal variability with account of low frequency modulation are obtained in terms of mathematics expectance vector and of invariant of dispersion tensor and spectral density in suggestion of stationary and periodic correlation vector stochastic process. For parameterization of synoptic scale variability the model of stochastic impulse process is applied as consequence of 'storms' and 'weather windows'. 'Storm' is defined as an excess of wind regime parameter values over defined level, and 'weather windows' are the intervals between two consequed storms. For synoptic events statistics description there are formed time-series of storm intensity characteristics, storms and weather windows durations. Threshold levels are prescribed on the base of quantile analysis or as a criteria of dangerous or especially dangerous parameters of wind regime. Synoptic variability based on time-series, centered on annual mean values and annual course of monthly mean values is analysed. Seasonal modulation and inter-annual variability of synoptic scale processes intensivity by time-series of intra-monthly dispersion as realization of periodic correlated process are described.

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Ujemny trend rocznych sum opadowych na Stacji im. H. Arctowskiego (Wyspa Króla Jerzego, Szetlandy Pd., Antarktyka Zach.)

Marsz A. A.

Problemy Klimatologii Polarnej

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1998

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nr 8

63--77

EN

The paper treats variabiliry of annual precipitation sum registred at the Arctowski Station for the 1978-1996 time period. The annual sum of precipitation show a big variability, its to possible to distinguish three periods in their course. For the period 1978-1985 mean annua1 precipitation sum amounted 560 mm (δn = 26 mm), for the next period (1986-1989) precipitation sum was characterised by a very strong variability (min = 377, max = 630 mm) mean precipitation sum amounted 472 mm,where δn = 95.4 mm. For the last, third period (1990-1996) mean precipitation sum amounted 456 mm (o n = 26.1 mm) (tab. l, fig. 1). Occurrence of strong periodicty every 6.0, 2.0, 4.50, 2.57 and 9.0 years has been found for the course of annual precipitation sum (fig. 2). Also, the spectrum analysis of a course of monthly precipitation sum in March (maximum of precipitation) and August (minimum of precipitation) has been led. Analysis showed the existence strong common periodicity (for annual and month sum: maximum and minimum) every 2.00, 3.60 and 6.00 years. Analysis of amplitudes and phases of periodicity do not explain the occurrence of so big variability of observed precipitation sum. The strong negative trend of annual precipitation sum, significant from the statistic point of view occurs here (fig. 3, formula l). Negative trends were also found in: the course of mean monthly precipitation sum for 8 from 12 monts of a year (the strongest and significant in February), in the course of number of days with measurable precipitation, in the mean annual twenty-four-hours precipitation sum. The negative trend of precipitation sum at Arctowski Station is not conformable to signalised (Ackley S., Bentley C., Foldvik A., Clarke A., King J, Priddle J. 1996.) positive trend of precipitation sum, which appears on the west coast of the Antarctic Peninsula. The examination of relation between precipitation sum at the Arctowski Station with walues of SOI shows, that the strongest relations between annual and maximum precipitation sum in a given year appears with one year delay (SOI of the previous year - precipitation of the present year), whereas in case of minimum sum the strongest relation appears with three years defay (tab. 2). The significant relation between monthly precipitation sum at the Arctowski Station and values of SOI appears in January and February (fig. 4, the strongest correlation with values of SOI are the end of winter and spring of the previous year). The negative trend of SOI correspond with the negative annual precipitation sum at the Arctowski Station. The observed environmental results, which confirms decrease of precipitation sum at the Arctowski Station has been shortly discussed (decrease of fields of permanent snow, disapperance of lakes and seasonal streams, drying of seashore terraces, hastening of ablation of glaciers ice from a surrounding glaciers, hastening of deglaciation processes).

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Głębokie zimowe inwersje temperatury na nadmorskiej terasie okolic Stacji im. H. Arctowskiego (wyspa Króla Jerzego, Szetlandy Pd., Antarktyka Zach.)

Kruszewski K.

Problemy Klimatologii Polarnej

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1998

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nr 8

47--62

EN

Paper presents results of investigations on temperature inversions, carried out during XIX Antarctic Expedition PAS in 1995, Temperature values taken from thermograph readings at Arctowski Station (3 m asl) and Point Thomas (173 m asl, situated 850 m, WNW from Station) were used to find periods of time with temperature inversions, Seven cases, analysed in this paper. Were selected as deep inversions (mean temperature gradient counted from hourly values was higher than 1°C/100 m), All presented inversions were radiation type, accompanied by calms and relatively small total nebulosity, except three cases, when nebulosity was the effect of inversion Influence of local orographic conditions on deepening temperature inversions is strong, but the main factor for it's forming is anticyclonic situation in the region of South Shetland Islands (accompanied by calms) and sea ice conditions. All analysed inversions were fonned during months with fast ice cover existence in Admiralty Bay and very close ar close ice fields on Bransfield Strait. In other ice conditions deep temperature inversions were not recorded, Minimum air temperatures at Arctowski Station recorded in July, August and September 1995 were measured during inversions. Maximum difference in air temperature between Point Thomas and Arctowski Station was recorded on July 22 (l4°C), These cases let to make conclusion, that probably all extremely low temperatures recorded during severe winters at Arctowski Station were measured in inversion conditions.