Wyniki wyszukiwania - BazTech

1

Klasyfikacja górnych pól wiatru w okresach dodatniej i ujemnej fazy oscylacji północnoatlantyckiej

Degirmendzić J.

Przegląd Geofizyczny

|

2012

|

Z. 2

157-169

PL

Celem pracy jest wyróżnienie najczęstszych typów górnej cyrkulacji związanych z silnie dodatnią i silnie ujemną fazą NAO oraz określenie stref górnej dywergencji i rozkładów SLP związanych z typami cyrkulacji górnotroposferycznej. Wykorzystano następujące dane: składowe wiatru z Reanaliz NCEP-NCAR (0, 12 UTC, 300 hPa, 1958-2007), dobową serię NAO, pola dywergencji (300 hPa) i ciśnienia (SLP) z Reanaliz ERA-40. Analiza dotyczy sezonu zimowego. Pola wiatru podzielono na dwie próby: pierwszą, związaną z silną dodatnią fazą NAO, drugą, odpowiadającą silnej ujemnej fazie NAO. Oddzielne procedury klasyfikacji zastosowano względem obu prób. Wykorzystano zmodyfikowaną metodę Lunda - współczynnik Pearsona zastąpiono współczynnikiem korelacji wektorowej Crosby’ego. Pola dywergencji i SLP uśredniono w klasach cyrkulacji. Analizę ograniczono do 9 najliczniejszych klas cyrkulacji związanych z NAO+ + i 9 klas związanych z NAO- _. Wyróżnione klasy grupują ok. 66% wszystkich pól występujących w fazie NAO+ + i ok. 48% wszystkich pól występujących podczas NAO- -. Ten wynik wskazuje na dość dużą liczbę pól, które tworzą mało liczne grupy, które nie zostały uwzględnione w badaniu. Biorąc pod uwagę położenie struktur w polu wiatru, które generują silną dywergencję, wyróżnione klasy pogrupowano w kategorie, w obrębie, których te same cechy pola wiatru wpływają na dynamikę Wyżu Azorskiego i Niżu Islandzkiego. Scharakteryzowano 3 kategorie procesów synoptycznych, które intensyfikują dodatnią fazę NAO oraz 2 kategorie procesów charakterystycznych dla silnej ujemnej fazy NAO.

EN

The aim of this paper is to distinguish the most frequent upper circulation types associated with strong negative and positive NAO phase and to delimit zones of upper divergence and SLP fields associated with selected types. The following datasets are utilised: wind records from the NCEPNCAR Reanalysis (0, 12 UTC, 300 hPa, 19582007), daily NAO record, divergence (300 hPa) and pressure (SLP) fields from ERA40. The analysis is confined to winter season. Wind fields were divided into two samples: the first related to strong positive NAO phase, the second corresponding to strong negative NAO phase. Separate classification procedures were applied to both samples. Modified Lund classification method was used - Pearson coefficient was replaced with Crosby vector correlation coefficient. The divergence and SLP deviations fields were averaged within circulation classes. The analysis is restricted to nine largest wind classes associated with NAO+ + and the other nine classes associated with NAO- _. Analysed classes group ~66% of all fields related to NAO+ + and ~48% of all fields occurring during NAO- -. This result indicates a fairly large number of fields that form small classes, which were not included in the study. Having considered the position of the wind field features which generate strong divergence, selected types were grouped into categories within which the same wind features affect the dynamics of the Azores high and the Iceland low. Three categories of synoptic processes, which intensify NAO and two categories of synoptic processes characteristic for NAO- - were described.

2

Rozkład przestrzenny kwadrantów jet streak w górnej troposferze w okresach dodatniej oraz ujemnej fazy NAO

Degirmendzić J.

Przegląd Geofizyczny

|

2011

|

Z. 3-4

149-170

PL

Celem analizy jest określenie związków pomiędzy rozmieszczeniem dywergentnych i konwergentnych kwadrantów jet streak w górnej troposferze a fazą Oscylacji Północnoatlantyckiej. W procedurach obliczeniowych wykorzystano pola wiatru z powierzchni 300 hPa nad sektorem euroatlantyc- kim, z rozdzielczością 4 X dobę, obejmujące okres 1958-2007 oraz serie dobowych wartości indeksu NAO. W terminowych polach wiatru zlokalizowano układy jet streak oraz określono pozycje ich kwadrantów (LF, RR, LR i RF). Następnie zliczono wystąpienia poszczególnych sektorów jet streak w kolistych gridach osobno w okresie dodatniej i ujemnej fazy NAO. Przestrzenne rozkłady częstości kwadrantów oraz rozkłady różnic częstości kwadratów dywergentnych i konwergentnych stanowią podstawą niniejszej analizy. Rezultaty analizy wskazują, Se w dodatniej fazie NAO nad północną częścią badanego akwenu Atlantyku przewaSają dywergentne sektory jet streak nad konwergentnymi, a nad południowym regionem zaznacza się dominacja kwadrantów konwergentnych. Taki rozkład kwadrantów jet streak sprzyja utrwalaniu pola ciśnienia związanego z fazą NAO + . W ujemnej fazie oscylacji w obu regionach Atlantyku (Islandii i Azorów) występuje nieznaczna przewaga dywergentnych sektorów jet streak. Ta przewaga nie różni się wyraźnie między regionami, co sprzyja utrwalaniu słabego gradientu ciśnienia między Islandią a Azorami. Również proces zmiany fazy NAO wydaje się być stymulowany przez zmianę cyrkulacji w górnej troposferze - podczas transformacji NAO- do NAO+ obserwuje się wzrost przewagi kwadrantów dywergentnych nad regionem północnym oraz początkowy spadek przewagi dywergentnych sektorów i późniejszy wzrost dominacji konwergentnych sektorów nad południowym regionem badanego akwenu Atlantyku.

EN

The radiolarian fauna from deep-water settings in the Umbria- Marche and the Outer Carpathian basins of the Western Tethys is used for biostratigraphic purpose and interpretation of environmental changes during the late Cenomanian through the Early Turonian time interval. The frequency of 184 recognized species, thirteen of them newly described, has been processed and analyzed. Three radiolarian biozones and one subzone are distinguished based on radiolarian datum events, correlated with the chronostratigraphic scale through the ?13C curve. The whole radiolarian set has been subdivided into six super groups, including 25 groups related to specific water masses. The assembled species represented various feeding preferences and ecological strategies. An increase of radiolarian total number in the sediments related to the Bonarelli Level (BL) displays a positive correlation with an increase of phosphorus (P) content, and with a significant decrease in radiolarian diversity. Most of radiolarian species avoided levels with high P content, in contrast, some species as H. barbui and C. conara increased significantly in number of specimens. Diversified radiolarian assemblages appeared at levels, directly preceded by a notable P increase, marking a period when the water system was saturated in relation to nitrogen. The radiolarian abundance in the sediments was strongly related to their preservation during sinking in the water column and at the water/sediment interface, increasing significantly at levels, marked by high pellet production. Thus, pelletization played an important role in the transport of radiolarian skeletons and their further preservation, irrespective to conditions of radiolarians growth. Radiolarians experienced and responded to environmental changes during the 1.8 Ma around the Bonarelli Interval (BI). The Cenomanian-Turonian press extinction event – a period of unquestionable eutrophication represented by the BI, did not result in great radiolarian extinction and turnovers. The radiolarian radiation preceded the BI by over 330 ka. The extinction, directly connected with the OAE2 started ca. 240 ka before the end of the organic-rich sedimentation, coinciding with the onset of enhanced diatom frustules deposition, recorded in the siliceous part of the BI. Since this period, a step-wise radiolarian extinction continued through the Early Turonian. Many of the radiolarian species previously considered as terminating during the BI, in fact outlived up to “post-Bonarelli” times, having their last occurrence after the BI or even in the Early Turonian. In the case of the radiolarian fauna, the Bonarelli period caused the disappearance of many Lazarus taxa, which returned in almost their initial state during 940 ka after the BI. The current radiolarian study sheds light on the biological effects of anoxic events, indicating the role of the mesopelagic zone and oceanic circulation in nutrient exchange, which modulates and controls the OAE2. The mesopelagic zone played an important role in P sequestration and was responsible for the release of the most of P, leading to enhanced eutrophication of water column.

3

Obiektywna metoda klasyfikacji pól wektorowych na przykładzie górnotroposferycznych prądów strumieniowych

Degirmendzić J.

Przegląd Geofizyczny

|

2005

|

Z. 1-2

59-72

EN

In the paper there is presented the method designed for vector fields classification. It is based on the algorithm proposed by Lund (1963). The replacement of Pearson correlation coefficient with vector correlation coefficient defined by Crosby (1993) is the essential change that makes this technique suitable for treatment of vector fields. The correlation threshold, set a priori in scalar analyses, is calculated objectively, with the help of PVCR index introduced by Huth (1996). PVCR index expresses the proportion of average similarity between objects classified into different categories to objects grouped in the same classes. PVCR is computed for selected range of threshold values and minimum value indicates the ,,best" correlation threshold. The classification was carried out for wind fields at the 250 hPa surface over Europe for winter season during 1958-2003 period. 20 classes of jet stream patterns were distinguished, which constitute 60.7% of the sample. Basic statistics, i.e. average and maximum frequency and duration time, were calculated for the first six key jet types. The main features of upper circulation field as well as temperature and pressure distribution in the lower troposphere associated with the jet types were also described.

4

Fale termiczne nad Polską w zimie w zależności od pola wiatru w Europie

Degirmendzić J.

Przegląd Geofizyczny

|

2004

|

Z. 1-2

11-23

EN

The main goal of this paper is to analyze transformation of wind field over Europe associated with change of intensity of thermal wave in Poland during winter. Thermally anomalous periods were distinguished on the basis of daily mean temperature record at 52.5°N, 20°E grid point. Wind field was defined by meridional and zonal wind components. Both, temperature and wind data were retrieved from NCEP/NCAR Reanalysis. The analysis was performed for the period of 1950-2001 and 850 hPa isobaric level. Cold/heat waves were categorized into three thermal classes - extreme, moderate and weak. In order to analyze wind field the following parameters were employed: relative vorticity, wind speed and directional steadiness of wind vector. Additionally, the structure of streamlines was analyzed. Temperature rise in Poland is forced by the development of dipole-like structure, clearly seen on the map of anomalies of relative vorticity. Positive anomalies are situated over Norwegian See, eastern Atlantic and Scandinavia, while negative vorticity advection is observed in southern Europe. Simultaneously with dipole development the increase of wind speed in middle Europe is also noted - supposedly it constitutes significant feature of wind field responsible for temperature increase in Poland in winter. In case of extreme heat waves the source region of warm advection is shifted southwards. Streamline pattern indicates more parallel flow over the Atlantic to the Iberian Peninsula and change of wind direction over Poland, from westerly to south-westerly. Intensive transport of heat over the northern Europe reduces temperature contrast at the Mediterranean front, which consequently decelerates western flow and lowers directional steadiness of wind vector down to 50% over the southern part of continent. Field of vorticity anomalies corresponding to the cold waves occurrence over Poland posseses dipole-like structure, however its polarization is reversed. Anticyclonic vorticity advection occurs in northern Europe and northern Atlantic while southern Europe experiences increase of cyclonic vorticity. Cooling in central Europe is associated with transformation of circulation field into blocking type - simultaneously the source region of cold advection shifts northwards over the Scandinavia (around 70°N). Enhanced thermal contrasts over southern Europe together with air masses inflow from the north, i.e. possessing surplus of cyclonic vorticity, strengthen the Mediterranean front.

5

Epoki cyrkulacyjne XX wieku i zmienność typów cyrkulacji atmosferycznej w Polsce

Degirmendzić J., Kożuchowski K.

Przegląd Geofizyczny

|

2000

|

Z. 3-4

221-239

EN

A brief survey of classifications of the circulation epochs, ie. Periods of time when definite macro-forms of circulation prevail over the Northern Hemisphere, were included in this paper. All classifi-cations refer to the period from the end of XIXth century to the last decade of XXth century. Authors present conception of such classification procedure for the period 1901-1998 on the basis of mean seasonal values of the Zonal Index (ZI), assessing circulation conditions between the 350 and 650 N and seasonal values of the NAO. By means of the Ward's clustering method we were able to distinguish four groups of years within which: strong zonal flow prevails during the whole year (A), strong zonal flow dominates only in winter (B), weak zonal circulation affects only winter conditions (C) and weak zonal flow consti-tutes the characteristic feature of the circulation condition during the whole year (D). The occur-rence of the years classified as type B and C was particularly useful and allowed us to distinguish 7 circulation epochs. Definite seasonal patterns of intensity of the zonal flow expressed by values of the ZI and the NAO were ascribed to this epochs. During the epoch of 1987-1998 the strongest zonal circulation prevailed, whereas the least intense zonal flow occurred from 1957 to 1970. The changes in frequency of circulation types in Poland (according to Osuchowska-Klein, 1978, 1991) with reference to hemispheric circulation epochs were analysed. On the whole, considerable increase in ration between western and eastern types of circulation during the period of 1987-1998 and 1911-1927 is observed however during the epoch of 1971-1986 eastern types dominate.

6

Wpływ klina Wyżu Azjatyckiego nad Skandynawią na temperaturę powietrza w Europie

Degirmendzić J.

Przegląd Geofizyczny

|

1999

|

Z. 4

211-229

EN

In this paper relationships between temperature field in Europe and circulation generated by Asiatic High wedges over Scandinavia were investigated. In the preliminary stage of the study, according to appropriate synoptic criteria, the cases of Scandinavian wedge occurrence in the period between December and March (1946-1994), were identified. In order to characterize temperature variability influenced by the wedges, maps of daily temperature anomalies were used. The analysis of thermal properties of the airstream at 850 hPa isobaric level generated by the wedge was carried out on the basis of streamlines and isotachs pattern as well as temperature field during the wedge occurrence. Special attention was paid to the following points: 1. Asiatic High wedge over Scandinavia brings about a decrease in mean daily temperature at 850 hPa level within the aector 45 - 60 N, 5 - 30 E, that is in the middle-latitude belt which covers the Central and Northern Europe. The highest negative anomalies occur in March (-7 C), while the lowest ones in February (-3,5 C). It is due to the fact that in March the northeastern cold current over Central Europe originates in the eastern sector of Scandinavian High, in February, however the source region for the stream is located north of the Caspian and the Black Sea. 2. Couple pressure system: the Scandinavian wedge - a low a trough of low pressure in the eastern Mediteranean forces a flow of cold air to move southwestwards to the Central Europe. 3. In the eastern sector of the low coupled with the Scandinavian wedge (in the region of the Caspian Sea) a temperature increase is observed, which is equal to 3-4 C in December, January, March and 1,5 C in February. Although the daily temperature anomalies associated with the Scandinavian wedge are statistically significant, owing to its short-lived and episodic character (if this system occurs it lasts 4 days during one month on average), it shouldn't be treated as an important factor affecting the dynamics of climate in Poland and Europe.