Solar Forcing of the Streamflow of a Continental Scale South American River

TL;DR

This study finds a significant correlation between solar activity, particularly sunspot numbers, and the streamflow of the Parana River over the last century, suggesting solar forcing influences regional hydrology.

Contribution

It provides evidence of solar forcing on a major South American river's streamflow, linking solar activity to hydrological variability on multidecadal scales.

Findings

Strong correlation (r=0.78) between sunspot number and river flow.

Correlation with El Nino on shorter time scales.

Potential for improved flood prediction models.

Abstract

Solar forcing on climate has been reported in several studies although the evidence so far remains inconclusive. Here, we analyze the stream flow of one of the largest rivers in the world, the Parana in southeastern South America. For the last century, we find a strong correlation with the sunspot number, in multidecadal time scales, and with larger solar activity corresponding to larger stream flow. The correlation coefficient is r=0.78, significant to a 99% level. In shorter time scales we find a strong correlation with El Nino. These results are a step toward flood prediction, which might have great social and economic impacts.