Predicting heat waves? Look half a world away

Reblogged from Watts Up With That:

[HiFast Note:  This study identifies the Madden-Julian Oscillation (MJO) and correlates one of its phases to California heat waves.  Nothing really new here.  Joe Bastardi has been talking about the MJO for many years.]

charles the moderator /

When thunderstorms brew over the tropics, California heat wave soon to follow

University of California – Davis

An orchard of young trees withstands drought in California's Central Valley in 2014. The ability to predict heat waves in the Central Valley could help better prepare and protect crops and people from the impacts. Credit UC Davis

An orchard of young trees withstands drought in California’s Central Valley in 2014. The ability to predict heat waves in the Central Valley could help better prepare and protect crops and people from the impacts. Credit UC Davis

When heavy rain falls over the Indian Ocean and Southeast Asia and the eastern Pacific Ocean, it is a good indicator that temperatures in central California will reach 100°F in four to 16 days, according to a collaborative research team from the University of California, Davis, and the Asia-Pacific Economic Cooperation (APEC) Climate Center in Busan, South Korea.

The results were published in Advances in Atmospheric Sciences on April 12.


Heat waves are common in the Central California Valley, a 50-mile-wide oval of land that runs 450 miles from just north of Los Angeles up to Redding. The valley is home to half of the nation’s tree fruit and nut crops, as well as extensive dairy production, and heat waves can wreak havoc on agricultural production. The dairy industry had a heat wave-induced economic loss of about $1 billion in 2006, for instance. The ability to predict heat waves and understand what causes them could inform protective measures against damage.

“We want to know more about how extreme events are created,” said Richard Grotjahn, corresponding author on the paper and professor in the UC Davis Department of Land, Air and Water Resources. “We know that such patterns in winter are sometimes linked with areas of the tropics where thunderstorms are enhanced. We wondered if there might be similar links during summer for those heat waves.”

The scientists analyzed the heat wave data from June through September from 1979 to 2010. The data were collected by 15 National Climatic Data Centers 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.


“It’s well known that tropical rainfall, such as the MJO, has effects beyond the tropics,” said Yun-Young Lee of the APEC Climate Center in Busan, South Korea, the paper’s first author. “So a question comes to mind: Is hot weather in the Central California Valley partly attributable to tropical rainfall?”

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.


A Synthesis of Papers about the Madden-Julian Oscillation under Anthropogenic Warming

Reblogged from Watts Up With That:

Maloney, et al. (2019) Madden–Julian oscillation changes under anthropogenic warming (paywalled) is a summary of a gazillion papers (well, that may be an exaggeration) about the future of the Madden-Julian oscillation in an anthropogenic-warming world. There’s an assumption there, isn’t there?

The MJO is of great interest to many weather forecasters.

The abstract of Maloney, et al. (2019) reads:

The Madden–Julian oscillation (MJO) produces a region of enhanced precipitation that travels eastwards along the Equator in a 40–50 day cycle, perturbing tropical and high-latitude winds, and thereby modulating extreme weather events such as flooding, hurricanes and heat waves. Here, we synthesize current understanding on projected changes in the MJO under anthropogenic warming, demonstrating that MJO-related precipitation variations are likely to increase in intensity, whereas wind variations are likely to increase at a slower rate or even decrease. Nevertheless, future work should address uncertainties in the amplitude of precipitation and wind changes and the impacts of projected SST patterns, with the aim of improving predictions of the MJO and its associated extreme weather.

Hmmm, “…wind variations are likely to increase at a slower rate or even decrease…” That narrows it down.

Also (with my boldface), “…MJO-related precipitation variations are likely to increase in intensity…” If that’s a “likely” based on the IPCC likely scale, then that’s about a 66% likelihood, or so they say.

Ian Wilson: Is the November 2018 Madden Julian Oscillation (MJO) a possible trigger for an El Niño?

Tallbloke's Talkshop

Conservation of angular momentum – ice skater
The title says it all. Another in the author’s series of intriguing brain-teasers for followers of climate theory to explore, this time with a particularly topical theme.

1. The Madden Julian Oscillation (MJO)

The Madden Julian Oscillation (MJO) is the dominant form of intra-seasonal (30 to 90 days) atmospheric variability in the Earth’s equatorial regions (Zang 2005). It is characterized by the eastward progression of a large region of enhanced convection and rainfall that is centered upon the Equator.

This region of enhanced precipitation is followed by an equally large region of suppressed convection and rainfall. The precipitation pattern takes about 30 – 60 days to complete one cycle, when seen from a given point along the equator (Madden and Julian 1971, 1972).

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