A.B. Polonsky1, 2, A.V. Torbinskii1
1Institute of Natural and Technical systems, 28 Lenin str., Sevastopol, Russian Federation
2Sevastopol Branch of Lomonosov Moscow State University, 7 Heroes of Sevastopol str., Sevastopol, Russian Federation
The Indian Ocean dipole (IOD) is one of the main modes characterizing the interannual variability of the parameters of large-scale interaction between the ocean and the atmosphere in the equatorial zone of the World Ocean. The influence of IOD on the climate of Europe has poorly been studied so far, but it is known that an area with increased convection intensity over North Africa can also cover the southern part of the Mediterranean-Black Sea region.
In this paper, we will make a quantitative assessment of the impact of IOD and interannual variability of the Danube River run off fluctuations in the summer months. This will make possible to assess the contribution of IOD to the variability of climatic characteristics of Europe and the Black Sea basin, as the run off of the Danube in the total run off of rivers flowing into the Black Sea is about 60%.
The average monthly discharges of the Danube for the period from 1947 to 2001 were used as initial data. As an index of IOD the normalized difference of anomalies of the sea surface temperature between the western (50 E – 70 E, 10 S– 10 N) and eastern (90 E – 110 E, 0 – 10 S) parts of the equatorial zone of the Indian Ocean were taken. Positive values of the index characterize the positive IOD phase, the negative values – the negative IOD phase. To assess the impact of IOD on the performance of the runoff in the Danube, correlation coefficients between the average monthly levels of runoff and IOD indices for the periods 1947-1964, 1947-1971 and 1947-2001 for each month from May to September were calculated.
The obtained results allow us to conclude that there is a statistically significant signal associated with the IOD on the territory of the Danube watershed in summer. It was found that the maximum (in absolute value) correlation coefficients between the IOD index and the values of average monthly expenses were observed in the period from June to July and equaled to -0.3 in the period before the artificial regulation of the Danube drain. The IOD likely affects the European climate through the mechanism of the propagation of atmospheric disturbances from the equatorial-tropical parts of the Indian Ocean into the Mediterranean-Black Sea region.
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