An international team of scientists, led by the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, used more than a 100 years of weather observations and three powerful computer models to tackle one of the more difficult questions in meteorology. The question was, if the total energy that reaches Earth from the Sun changes by only 0.1 percent during the 11-year solar cycle, how can it drive major changes in weather patterns on Earth?
According to the study, the answer to this question has to do with how the Sun impacts the stratosphere and the tropical Pacific Ocean. These two areas don't seem to be related, but the stratosphere and tropical Pacific Ocean actually work together to create occasional weather patterns that affect much of the Earth.
During solar maximum, chemicals in the stratosphere and sea surface temperatures in the Pacific Ocean react to the Sun in a way that affects how air moves. This can make winds and rainfall more intense, change sea surface temperatures and cloud cover over certain tropical and subtropical regions, and influence weather around the Earth.
These changes keep the eastern Pacific even cooler and drier than usual, producing conditions similar to a La Niña event. The Earth's response to the solar cycle continue over the year or two following peak sunspot activity. The La Niña-like pattern triggered by the solar maximum tends to evolve into a pattern similar to El Niño, as slow-moving currents replace the cool water over the eastern tropical Pacific with warmer water.
The Indian monsoon, Pacific precipitation and sea surface temperatures, and other regional climate patterns are largely driven by rising and sinking air in Earth's tropics and subtropics. The new study could help scientists use solar-cycle predictions to estimate how that circulation, and the regional climate patterns related to it, might change over the next ten or twenty years.
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