Heat waves in California can be deadly and costly. Now scientists think a phenomenon in the Indian and eastern Pacific Oceans might predict when the next one could hit the state.
New findings, published in the journal Advances in Atmospheric Sciences, analyzed 24 heat waves from 1979 to 2010. They define a heat wave as three or more consecutive days of 100 degree temperatures.
They compared them with phases of a major traveling atmospheric circulation called the Madden-Julian Oscillation. The pattern creates heavy rain and is known to influence winter weather patterns.
“It’s well known that tropical rainfall ... has effects beyond the tropics,” said study co-author Yun-Young Lee of the APEC Climate Center in Busan, South Korea. “So a question comes to mind: Is hot weather in the Central California Valley partly attributable to tropical rainfall?”
The answer? A resounding yes. Heat waves show up in California within about two weeks after heavy rainfall in the eastern Pacific Ocean and the Indian Ocean.
Knowing the timeframe of when a heat wave could hit is important because it would allow farmers, residents and government officials to plan for the effects of sustained high temperatures. A 10-day heat wave in 2006 killed 650 people and cost the dairy industry about a billion dollars.
"I think 1,000 PG&E transformers blew out just because of the load of electricity running through the lines,” said UC Davis’ Richard Grotjahn who’s authored multiple reports on heat waves. “People running air conditioners was a big power demand."
That’s important for places like California’s Central Valley, where more than half of the country’s tree fruit and nuts are grown. It’s also important for areas of the state where having air conditioning units isn’t common.
Another reason having this information is important? Heat waves are predicted to get worse as warming temperatures create more extremes in weather.
"Heat waves by the end of the century would be lasting twice as long on average and be four to eight degrees Fahrenheit warmer,” Grotjahn explained in a past study.