El Niño events have long been perceived as a determinant of low rainfall in winter and spring in Hawai'i, creating a six-month drought of the rainy season. However, the connection between winter rains Hawaiʻi and El Niño is not as straightforward as previously thought, according to a recent study by researchers at the University of Hawaiʻi at the School of Ocean and Land of Mānoa Science and Technology ( SOEST ).
Studies over the past decade suggested that there are at least two types of El Niño: the eastern Pacific and the central Pacific, when the warmest pool of water is in the eastern or central portions of the ocean basin, respectively. El Niño events generally begin in summer and last approximately one year.
Atmospheric scientists from UH Mānoa analyzed data on large-scale circulation patterns over the eastern and central Pacific to find that the Hawaiʻi drought is only associated with the eastern Pacific El Niño. In the case of El Niño events in the central Pacific, poor rains in Hawaiʻi occurred only 60% of the time. Therefore, a winter drought is not guaranteed after an El Niño in the central Pacific.
Critical to water resources planning and management
Differences in how El Niño from the central and eastern Pacific affect rainfall can be essential for proper planning and management of water resources.
“This new result is a boon to many agencies in Hawaiʻi, eg, the Water Supply Board, Hawaiʻi Department of Lands and Natural Resources, and Hawaiʻi Department of Agriculture, ”said Pao-Shin Chu professor SOEST state climatologist Hawaiʻi and study co-author. "Beyond these agencies, ranchers, flower growers and other stakeholders who are concerned about the relationship between El Niño and the water supply in Hawai'i can also benefit from the new findings."
Since El Niño is a recurring phenomenon, knowing the type of El Niño that occurs will allow researchers and resource managers to more easily assess and prepare for Hawaii's regional winter climate.
For more information, see the SOEST website .
–By Marcie Grabowski