Predicting Heat Waves?
Look Half a World Away
The results were published in Advances in Atmospheric Sciences on April 12.
From prediction to protection
– Richard Grotjahn
The scientists analyzed the heat wave data from June through September from 1979 to 2010. The data were collected by 15 National Climatic Data Center stations located throughout the valley. From these data, the researchers identified 24 heat waves. They compared these instances to the phases of a large, traveling atmospheric circulation pattern called the Madden-Julian Oscillation, or MJO.
The MJO manifests as heavy rain that migrates across the tropical Indian and then Pacific oceans, and researchers have shown that it influences winter weather patterns.
Tropical rainfall and California
Lee and Grotjahn found that, yes, enhanced rainfall in the tropics preceded each heat wave in specific and relatively predictable patterns. They also found that hot weather in the valley is most common after more intense MJO activity in the eastern Pacific Ocean, and next most common after strong MJO activity in the Indian Ocean.
“The more we know about such associations to large-scale weather patterns and remote links, the better we can assess climate model simulations and therefore better assess simulations of future climate scenarios,” Grotjahn said.
This work was supported by the National Science Foundation, the National Aeronautics and Space Administration, the Department of Energy Office of Science, the United States Department of Agriculture’s National Institute of Food and Agriculture, and the APEC Climate Center in the Republic of Korea.