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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, D21114, doi:10.1029/2006JD007462, 2006

Is solar variability reflected in the Nile River?

Alexander Ruzmaikin

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA


Joan Feynman

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA


Yuk L. Yung

Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA


Abstract

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.

Received 1 May 2006; accepted 9 August 2006; published 11 November 2006.

Keywords: climate variability; solar variability.

Index Terms: 1616 Global Change: Climate variability (1635, 3305, 3309, 4215, 4513); 1650 Global Change: Solar variability (7537); 1631 Global Change: Land/atmosphere interactions (1218, 1843, 3322); 1854 Hydrology: Precipitation (3354).

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Citation: Ruzmaikin, A., J. Feynman, and Y. L. Yung (2006), Is solar variability reflected in the Nile River?, J. Geophys. Res., 111, D21114, doi:10.1029/2006JD007462.