How did La Nina cause the Chinese Snowstorms 2008?
The connection between La Nina and the weather is not well understood. But there is a connection between the presence of La Nina and cooler than normal weather in China because there are more frequent outbreaks of arctic air spilling down into the country from Siberia. What causes the pool of cool water begins with a difference in pressure in the atmosphere. Higher than normal pressure over Tahiti and lower than normal pressure over Darwin Austrailia cause a strengthening of westerly trade winds near the equator. The westerly blowing winds pushes water near the surface of the Pacific Ocean westward. To account for this displacement of water, cool water upwells (rises) from deep in the ocean to create cooler than normal water temperatures. This pool of cool water gradually expands westward and persists until the pressure pattern at Tahiti and Darwin reverses…which will ultimately lead to a weakening of La Nina and the growth of warm water anomalies, or El Nino.
