Sunspots encourage heavy rainfall in East Africa

Researchers are discovering the possible connection between solar activity and precipitation

Sunspot © SOHO (NASA / ESA)
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There seems to be more connections between the sun and our weather than we thought. Scientists have now found that periods of particularly heavy rainfall in East Africa are associated with periods of particularly high solar activity and associated sunspots. The new study thus contradicts previous findings.

An increased number of sunspots is an indication of a time of particularly strong energy radiation of the sun. The periods of this activity are cyclical - every eleven years solar activity reaches a maximum. The next is expected for 2011 or 2012. It is indisputable that these fluctuations are an influencing factor for the terrestrial climate as well, but it is hotly debated how strong this influence is. Now, a British-American research team led by Curt Stager of Paul Smith's College, New York, has discovered another link between solar activity and climate - in East Africa.

The researchers analyzed precipitation data for the last 100 years for this region, using historical records of water levels in the Victoria, Tangayika and Naivasha lakes. Previous studies had found no link between solar activity and rainfall here. Even the current results are not very clear for at least one period, the time between 1927 and 1968, but according to the researchers, the context as a whole is nevertheless clear and significant. It is apparent that solar activity mainly affects precipitation during the rainy season, but it can also cause heavy rainfall outside of this period.

More evaporation through higher solar activity?

"The results of the current study show that the correlations are not random, " explains Alexander Ruzmaikin of NASA's Jet Propulsion Laboratory and co-author of the study. "It expands our knowledge of how the sun affects the climate of Africa and solves a long-standing mystery at the same time."

But how exactly can solar activity affect precipitation? The researchers can imagine some possibilities here. In the simplest case, however, the higher energy radiation of the sun leads to a stronger warming of land and sea and thus to an increased evaporation. This increases the water vapor content of the atmosphere and precipitation becomes more frequent and intense. display

Next maximum starts in 2011

The next sun maximum await astronomers in 2011/2012. For Stager and his team, this means a possible weather reaction already a year before: "We expect that East Africa will experience a strong intensification of precipitation during the rainy season, as well as an increased spread of yellow fever", explains Stager. Since mosquitoes and other disease-transmitting insects reproduce particularly well in moist conditions, epidemics could be enhanced by this climate development.

"Our hope is that people will use our results to better predict the heavy rain, " Stager said. If these events lead to flooding, erosion and even disease. Forewarned by the approaching solar maximum, authorities could, for example, begin to prevent insect-borne diseases long before the actual epidemic breaks out.

(American Geophysical Union, 07.08.2007 - NPO)