ハドレー循環
A study of climate records has shown a relationship between El Niño and the Western Hemisphere Warm Pool (WHWP). During a normal Northern Hemisphere winter, diabatic heating over the Amazon drives a Hadley cell with descending air over an anticyclone north of 20°N in the subtropical North Atlantic and associated northeast trade winds between Africa and the Caribbean. An El Niño weakens the Amazonian cell, the anticyclone and the easterly tradewinds, causing the tropical North Atlantic to warm more than usual in the spring. About half of El Niño events persist sufficiently into the spring months for the warm pool to become unusually large by summer.