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The large-scale moisture transfer in the tropical zone during the culmination of El-Nino and La-Nina eventsстатья
- Автор: Platonov V.
- Сборник: Climate Variability in the Tropical Pacific: Mechanisms, Modeling and Observations
- Год издания: 2010
- Место издания: MAKS Press Moscow
- Первая страница: 77
- Последняя страница: 88
- Аннотация: Abstraction of scenarios of development of large-scale moisture transfer anomalies is spent according to re-analyses NCEP/NCAR, GPCP and ERA-40 data during the periods of warm and cold phases of the phenomenon the El-Nino – Southern Oscillation. Moisture transfer patterns in extreme events of phenomenon ENSO (both warm, and cold phases) were considered. The analysis has shown that in both cases unprecedented anomalies of large-scale circulation in zonal and meridional directions are observed. During the period of the El-Nino intensive moisture transfer in the system of equatorial western winds is displaced from area of Indonesia in the central water areas of Pacific ocean and converged with weakened east trade winds transfer to east parts of ocean. Finally it leads to formation of powerful congestions of cumulo-nimbus cloudiness and rich precipitations in the centre and in the east of tropics of Pacific ocean. Thus, over Indian ocean during the period of El-Nino the unique situation also was observed – in all layer of atmosphere to 5 km moisture transfer to system of equatorial western winds has been replaced with a moisture transfer by trade winds. As a result of these two macro-scale anomalies the area of Indonesia and northern Australia in a summer monsoon has turned out in the field of large-scale moisture divergence, here again instead of monsoonal rains catastrophic droughts were observed. In a cold phase – La-Nina – took place essentially other situation. The area of the western moisture transfer was displaced on some thousand kilometers on the West, in the traditional area over Indonesia. Over Pacific ocean, on the contrary, completely prevailed east trade winds transfer. During La-Nina the intensification of the moisture transfer by western trade winds over Indian ocean was observed and circulation in tropics over there was reinstated. As a result of sea continent of Indonesia and northern Australia have turned of in La-Nina in the field of large-scale moisture convergence that has led to strengthening of the Australian monsoon and catastrophic flooding. In addition for revealing of the mechanisms defining anomalies of precipitations in a tropical zone empirical orthogonal function analysis (EOF) of precipitation fields is applied. The first EOF mode has received almost 36 % of the general dispersion. Their main components schedule has shown that its most extreme values were observed in 1983 and 1998, i.e. in those years when the most catastrophic events the El-Nino – Southern Oscillation were occurred. It is shown that in 1983 and 1998 the greatest positive anomalies of precipitations caused by variability of large-scale atmospheric circulation, were observed in the central areas of Pacific ocean, and negative – in western areas. In years of La-Nina the opposite picture, accordingly, was observed.
- Добавил в систему: Платонов Владимир Сергеевич