Abstract
The Mediterranean area belongs to the regions most exposed to hydroclimatic changes, with a likely increase in frequency and duration of droughts in the last decades. However, many climate records like, e.g., North Italian precipitation and river discharge records, indicate that significant decadal variability is often superposed or even dominates long-term hydrological trends. The capability to accurately predict such decadal changes is, therefore, of utmost environmental and social importance. Here, we present a twofold decadal forecast of Po River (Northern Italy) discharge obtained with a statistical approach consisting of the separate application and cross-validation of autoregressive models and neural networks. Both methods are applied to each significant variability component extracted from the raw discharge time series using Singular Spectrum Analysis, and the final forecast is obtained by merging the predictions of the individual components. The obtained 25-year forecasts robustly indicate a prominent dry period in the late 2020s/early 2030s. Our prediction provides information of great value for hydrological management, and a target for current and future near-term numerical hydrological predictions.
Highlights
The Mediterranean region is an area of complex morphology in the transition zone between the arid to semiarid subtropical climate of Northern Africa and the humid extratropical climate of central and northern Europe
Our analysis indicates that during the last two centuries Northern Italy evolved from a relatively stable and quiet 19th-century regime, with only one decadal drought episode identified in the 1830s, to a 20th-century regime characterized by recurrent decadal periods of low discharges and, most recently, to a significant intensification of interannual droughts culminated in the extreme events of the late 20th and early 21st centuries
We presented a twofold statistical approach for a robust interannual-to-decadal prediction of midsize basin river discharges for the Euro-Mediterranean region, using the North Italian Po River as a case study
Summary
The Mediterranean region is an area of complex morphology in the transition zone between the arid to semiarid subtropical climate of Northern Africa and the humid extratropical climate of central and northern Europe. In the Mediterranean area, significant decadal variability is often superposed or even dominates observed long-term climatic and hydrological trends (e.g., [3]), a behavior that unequivocally emerges in North Italian precipitation and river discharge records [4,5,6]. The observed persistence of strong decadal fluctuations over periods of several decades provides the potential for near-term regional hydroclimate predictions. This paper explores the viability of statistical decadal river discharge predictions in the Mediterranean region using the North Italian Po River as a case study
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