INFLUENCE OF THE NORTH ATLANTIC OSCILLATION ON MULTIYEAR HYDROLOGICAL AND THERMAL REGIME OF NORTHERN EURASIA. I. STATISTICAL ANALYSIS OF OBSERVATIONAL DATA

V. V. Popova and A. B. Shmakin

Monthly mean series of the North Atlantic Oscillation index (INAO) and meteorological parameters at a regular 2.5º grid, namely, anomalies of atmospheric precipitation (from the GISS archive, 1950—1997) and air temperature (NCEP archive, 1958—1997) are used to construct fields of the correlation coefficient between these parameters and INAO for each month. The fields of air temperature and precipitation anomalies are also constructed for several INAO gradations. A comparative analysis of the patterns of correlation coefficient of temperature and precipitation with INAO and of the fields of anomalies of these parameters for different INAO values demonstrates their complicated nonlinear dependence on the index fluctuations. The nonlinear influence of the NAO manifests itself in the river runoff integrating variations of the hydrothermal regime. The NAO signal is found in the Volga River annual runoff variability (1879—1991) and appears in quasi-periodicities of 7—7.5 and 12—14 years typical of the NAO.