UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2004 Meeting


Section: Atmosphere and Earth Science; Environment Protection


Title:
The role of North Atlantic Oscillation in the natural variability of winter phreatic groundwater regime over Romanian territory, some numerical results.


Authors:
Elena Tanase


Affiliation:
National Institute of Hydrology and Water Management,

Bucharest, Romania


E-mail
elena.tanase@hidro.ro


Keywords:
Low frequency variability, NAO, phreatic groundwater


Abstract:
A Low Frequency Variability (LFV) at the scale of inter-annual to inter-decadal variability mechanism responsible for the NH Hemisphere-particularly over Eurasia regions is the NAO (North Atlantic Oscillation) mode. The spatial pattern associated is well characterized in the North Atlantic area at any time scale. The dominant large-scale fluctuation is between the Azores Anticyclone and the Iceland Low, and the normalized pressure between them is defining the NAO index. In midwinter and early spring, NAO type atmospheric circulation influences the extent of snow cover over Eurasia; the NAO signal is strongest in the cold season (DJFM),the linkage between NAO variability and snow cover extent over Eurasia is manifested for the previous and next winter( 1973-1998) and are computed correlation coefficients between monthly Eurasian snow cover content and the Hurrell’s Index. The sign(and values) of the NAO is influencing the phreatic groundwater regime, so the expected results are a numerical evidence concerning the response of the phreatic groundwater regime to the NAO natural mode of large scale mechanism of variability, for predictability purposes (as expected from the reference, from monthly to decadal time scales). Because a good degree of predictability is found in the snow-related atmospheric circulation anomalies and NAO type atmospheric circulation influences the extent of snowcover and the snowcover affects the atmosphere in the late spring, summer and early autumn, a particular attention is paid to the winter phreatic groundwater regime. The computations are consistent with the significant variability at different time scales, but for our purpose, are used monthly phreatic groundwater levels covering the interval 1964-2000. As resulted from a set of computations from data locations covering a wide area of the Romanian territory, the significance of the correlation coefficients for lagtime < 4 between phreatic groundwater levels from different months are concluding to expected dependencies following the reference correlations, cited above.