Climate and Dynamics
Is solar variability reflected in the Nile River?
Article first published online: 11 NOV 2006
Copyright 2006 by the American Geophysical Union.
Journal of Geophysical Research: Atmospheres (1984–2012)
Volume 111, Issue D21, 16 November 2006
How to Cite
2006), Is solar variability reflected in the Nile River? J. Geophys. Res., 111, D21114, doi:10.1029/2006JD007462., , and (
- Issue published online: 11 NOV 2006
- Article first published online: 11 NOV 2006
- Manuscript Accepted: 9 AUG 2006
- Manuscript Revised: 5 JUL 2006
- Manuscript Received: 1 MAY 2006
- climate variability;
- solar variability
 We investigate the possibility that solar variability influences North African climate by using annual records of the water level of the Nile collected in 622–1470 A.D. The time series of these records are nonstationary, in that the amplitudes and frequencies of the quasi-periodic variations are time-dependent. We apply the Empirical Mode Decomposition technique especially designed to deal with such time series. We identify two characteristic timescales in the records that may be linked to solar variability: a period of about 88 years and one exceeding 200 years. We show that these timescales are present in the number of auroras reported per decade in the Northern Hemisphere at the same time. The 11-year cycle is seen in the Nile's high-water level variations, but it is damped in the low-water anomalies. We suggest a possible physical link between solar variability and the low-frequency variations of the Nile water level. This link involves the influence of solar variability on the atmospheric Northern Annual Mode and on its North Atlantic Ocean and Indian Ocean patterns that affect the rainfall over the sources of the Nile in eastern equatorial Africa.