Sunspot Abundance Linked to Heavy Rains in East Africa
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6 August 2007
AGU Release No. 07-19
For Immediate Release
Sunspot abundance linked to heavy rains in East Africa
AGU Contact: Peter Weiss
+1 (202) 777-7507
pwe...@agu.org
Paul Smith's Contact:
Kenneth Aaron
+1 (518) 327-6297
kaa...@paulsmiths.edu
WASHINGTON - A new study reveals correlations between
plentiful sunspots and periods of heavy rain in East Africa.
Intense rainfall in the region often leads to flooding and
disease outbreaks.
The analysis by a team of U.S. and British researchers shows that
unusually heavy rainfalls in East Africa over the past century
preceded peak sunspot activity by about one year. Because periods
of peak sunspot activity, known as solar maxima, are predictable,
so too are the associated heavy rains that precede them, the
researchers propose.
"With the help of these findings, we can now say when especially
rainy seasons are likely to occur, several years in advance," says
paleoclimatologist and study leader Curt Stager of Paul Smith's
College in Paul Smiths, New York. Forewarned by such predictions,
public health officials could ramp up prevention measures against
insect-borne diseases long before epidemics begin, he adds.
The sunspot-rainfall analysis is scheduled to appear on 7 August
in the Journal of Geophysical Research - Atmospheres, a publication
of the American Geophysical Union.
Increasing sunspot numbers indicate a rise in the sun's energy
output. Sunspot abundance peaks on an 11-year cycle. The next solar
maximum is expected in 2011-2012. If the newfound pattern holds,
rainfall
would also peak the year before.
"We expect East Africa to experience a major intensification of
rainy season precipitation, along with widespread Rift Valley Fever
epidemics, a year or so before the solar maximum of 2011-2012," the
team reports. Because mosquitoes and other disease-carrying insects
thrive in wet conditions, heavy rains may herald outbreaks of
diseases such as Rift Valley Fever.
The new analysis relies on rainfall data going back a century. The
scientists also used historical records of water levels at lakes
Victoria, Tanganyika, and Naivasha.
The work counters previous research that found no connection
between sunspot cycles and rainfall in East Africa. Stager's team
concludes that, although the link between sunspots and rainfall was
weak between 1927 and 1968, the cyclic pattern held true throughout
the 20th century. Previous statistical analysis discounted the link
for a variety of reasons, including the influence of El Nino and
other climatic disturbances not associated with sunspots.
Scientists have investigated apparent correlations between solar
variability and Lake Victoria's water levels since the beginning of
the last century, says co-author Alexander Ruzmaikin of NASA's Jet
Propulsion Laboratory in Pasadena, California. The new research
"shows that these correlations are, in fact, not accidental,
effectively resolving a longstanding historical puzzle and improving
our knowledge of how solar variability affects Africa's climate," he
adds.
Stager, Ruzmaikin and their colleagues offer several reasons why
sunspot peaks may affect rainfall. In a simple scenario, increased
solar energy associated with sunspots heats both land and sea, forcing
moist air to rise and triggering precipitation.
While sunspot peaks augur extraordinarily wet rainy seasons, heavy
rains are possible at other times as well, Stager acknowledges. But,
most of the rainiest times, he says, are consistently coupled with the
predictable rhythms of sunspot peaks. And, to be forewarned is to be
forearmed.
"The hope is that people on the ground will use this research to
predict
heavy rainfall events," Stager says. "Those events lead to erosion,
flooding, and disease."
The National Science Foundation funded the study.
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Neither the paper nor this press release are under embargo.
Title:
"Sunspots, El Nino, and the levels of Lake Victoria, East Africa"
Authors:
J. Curt Stager, Natural Sciences Division, Paul Smith's College, Paul
Smiths, NY 12970, USA;
Alexander Ruzmaikin, Jet Propulsion Laboratory, California Institute
of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA;
Declan Conway, School of Development Studies, University of East
Anglia, Norwich NR4 7TJ, UK;
Piet Verburg, Institute of Ecology, University of Georgia, Athens, GA
30602, USA;
Peter J. Mason, MWH UK Ltd, Terriers House, 201 Amersham Road,
High Wycombe, Bucks HP13 5AJ, UK.
Citation:
Stager, J. C., A. Ruzmaikin, D. Conway, P. Verburg, and P. J. Mason
(2007), Sunspots, El Nino, and the levels of Lake Victoria, East
Africa, J. Geophys. Res., 112, D15106, doi:10.1029/2006JD008362.
Contact information for authors:
Curt Stager, professor of natural resources, office phone: +1
(518) 327-6342, cst...@paulsmiths.edu