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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 2:08 |
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Conference: Bucharest University Faculty of Physics 2006 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Spatial and temporal variability of precipitation and river flows in Romania, on winter period, in connection with the North Atlantic Oscillation
Authors:
Monica Ghioca(1), Sabina Stefan(2)
Affiliation:
(1)National Institute of Hydrology and Water Management
97 Sos. Bucuresti-Ploiesti, 013686 Bucuresti, ROMANIA
(2)University of Bucharest, Faculty of Physics, P.O.BOX MG-11,Bucharest, Romania
E-mail
monica.ghioca@hidro.ro
Keywords:
Mann-Kendall test, EOF analysis, NAO
Abstract:
The main characteristics of spatial and temporal variability of the precipitation and streamflow on winter season were determined by analyzing the precipitation quantities and the monthly average discharges series from 26 meteorological stations and 40 hydrometrical stations (December-February, 1950-2003). The local significance of trends has been analysed with the nonparametric Mann-Kendall (MK) test for the winter streamflow. The values of the statistics are negative in almost entire region, excepting north-eastern part.The dominant mode of precipitation and flow variability was determined using the Empirical Orthogonal Function (EOF) technique. The first EOF pattern of precipitation, that explains 74% of the total variance, is characterised by the same sign in the entire region, with higher values in the region situated in the southern and eastern part of region. The second EOF, that explains 11% of total variance, presents a dipolar structure with one pole situated in the intra-Carpathian region and the other in the extra-Carpathian region. The first EOF pattern of discharges explains 53% of the total variance and it is characterized by the same sign in the entire region, with higher values in the intra-Carpathian region. The second EOF, that explains 20% of total variance, presents a dipolar structure with one pole situated in the southern region and the other in the northern region. The first patterns suggest that in spite of the highly irregular topography of the region, there is a common physical dominating the winter precipitation and streamflow variability and this process could be linked to large-scale process. The second patterns suggest the influence of the Carpathian Mountain on the winter precipitation and streamflow variability. The first principal components (PC1) of precipitation evidences a negative trend and a significant downward shift in the winter 1969/1970. The PC1 of streamflow evidences a significant negative trend too and a significant downward shift in the winter 1981/1982.There is an out-of-phase relationship between the Romanian precipitation and river flows and NAO index.
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