Washington, Aug 28 (Inditop.com) Sun spot frequency, the equivalent of a solar sneeze, can upset cloud formation and precipitation on earth.
Our sun radiates rather erratically, the best known example being the famous 11-year sun-spot cycle activity.
Nobody denies its influence on the natural climate variability, but climate models have been unable to reconstruct its impact on climate activity.
Researchers from the US and Germany, for the first time, have now successfully simulated the complex interaction between solar radiation, atmosphere, and the ocean.
Gerald Meehl, from the US-National Center for Atmospheric Research (NCAR) and his team have been able to calculate how the tiny variations in radiation brings about a comparatively significant change in our climate.
Taking into consideration the complete radiation spectrum of the sun, the radiation intensity within one sun spot cycle varies by just 0.1 percent, said study co-author Katja Matthes of the GFZ German Research Centre for Geosciences.
“Complex interplay mechanisms in the stratosphere and the troposphere, however, create measurable changes in the water temperature of the Pacific and in precipitation.”
The initial process runs from the top downwards: increased solar radiation leads to more ozone and higher temperatures in the stratosphere.
“The ultraviolet radiation share varies much more strongly than the other shares in the spectrum, that is by five to eight percent, and that forms more ozone” explains Katja Matthes.
As a result, especially the tropical stratosphere becomes warmer, which in turn leads to changed atmospheric circulation. Thus, the interrelated typical precipitation patterns in the tropics are also displaced.
The second process takes place in the opposite way: the higher solar activity leads to more evaporation in the cloud free areas, said a GFZ release.
With the trade winds the increased amounts of moisture are transported to the equator, where they lead to stronger precipitation, lower water temperatures in the East Pacific and reduced cloud formation, which in turn allows for increased evaporation.
“It is this positive back coupling that strengthens the process,” said Katja Matthes. With this, it is possible to explain the respective measurements and observations on the Earth’s surface.
These findings were published in the latest issue of Science.
