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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/hess-2016-304
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
28 Jun 2016
Review status
This discussion paper has been under review for the journal Hydrology and Earth System Sciences (HESS). The manuscript was not accepted for further review after discussion.
Hydrological response in the Danube lower basin to some internal and external climate forcing factors
Ileana Mares1, Venera Dobrica1, Crisan Demetrescu1, and Constantin Mares2 1Institute of Geodynamics, Romanian Academy, Bucharest, Romania
2National Institute of Hydrology and Water Management, Bucharest, Romania
Abstract. Of the internal factors, we tested the predictors from the fields of precipitation, temperature, pressure and geopotential at 500hPa. From the external factors, we considered the indices of solar/geomagnetic activity. Our analysis was achieved separately for each season, for two time periods 1901–2000 and 1948–2000. We applied developments in empirical orthogonal functions (EOFs), cross correlations, power spectra, filters, composite maps. In analysis of the correlative results, we took into account, the serial correlation of time series. For the atmospheric variables simultaneously, the most significant results (confidence levels of 95 %) are related to the predictors, considering the difference between standardized temperatures and precipitation (TPP), except for winter season, when the best predictors are the first principal component (PC1) of the precipitation field and the Greenland-Balkan-Oscillation index (GBOI). The GBOI is better predictor for precipitation, in comparison with North Atlantic Oscillation index (NAOI) for the middle and lower Danube basin. The significant results, with the confidence level more than 95 %, were obtained for the PC1-precipitation and TPP during winter/spring, which can be considered good predictors for spring/summer discharge in the Danube lower basin. Simultaneous, the significant signal of geomagnetic index (aa), was obtained for the smoothed data by band pass filter. For the different lags, the atmospheric variables respond to solar/geomagnetic activity after about 2–3 years. The external signals in the terrestrial variables are revealed also by power spectra and composite maps. The power spectra for the terrestrial variables show significant peaks that can be associated with the interannual variability, Quasi-Biennial Oscillation influence and solar/geomagnetic signals. The filtering procedures led to improvement of the correlative analyses between solar or geomagnetic activity and terrestrial variables, under the condition of a rigorous test of the statistical significance.

Citation: Mares, I., Dobrica, V., Demetrescu, C., and Mares, C.: Hydrological response in the Danube lower basin to some internal and external climate forcing factors, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2016-304, 2016.
Ileana Mares et al.
Ileana Mares et al.

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Short summary
This investigation was necessary due to the economical and social importance of the Danube lower basin discharge, taking into account the climate change (greenhouse and solar/geomagnetic activity) impact, as well as few approaches on this issue. By applying robust statistical methods and rigorously testing of results, new indicators were found to estimate the discharge in the Danube lower basin. The investigation will be extended with indicators from the climate change models.
This investigation was necessary due to the economical and social importance of the Danube lower...
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