PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Scientists eye longer-term forecasts of US heat waves

2013-10-28
(Press-News.org) Contact information: David Hosansky
hosansky@ucar.edu
303-497-8611
National Center for Atmospheric Research/University Corporation for Atmospheric Research
Scientists eye longer-term forecasts of US heat waves

BOULDER -- Scientists have fingerprinted a distinctive atmospheric wave pattern high above the Northern Hemisphere that can foreshadow the emergence of summertime heat waves in the United States more than two weeks in advance.

The new research, led by scientists at the National Center for Atmospheric Research (NCAR), could potentially enable forecasts of the likelihood of U.S. heat waves 15-20 days out, giving society more time to prepare for these often-deadly events.

The research team discerned the pattern by analyzing a 12,000-year simulation of the atmosphere over the Northern Hemisphere. During those times when a distinctive "wavenumber-5" pattern emerged, a major summertime heat wave became more likely to subsequently build over the United States.

"It may be useful to monitor the atmosphere, looking for this pattern, if we find that it precedes heat waves in a predictable way," says NCAR scientist Haiyan Teng, the lead author. "This gives us a potential source to predict heat waves beyond the typical range of weather forecasts."

The wavenumber-5 pattern refers to a sequence of alternating high- and low-pressure systems (five of each) that form a ring circling the northern midlatitudes, several miles above the surface. This pattern can lend itself to slow-moving weather features, raising the odds for stagnant conditions often associated with prolonged heat spells.

The study is being published next week in Nature Geoscience. It was funded by the U.S. Department of Energy, NASA, and the National Science Foundation (NSF), which is NCAR's sponsor. NASA scientists helped guide the project and are involved in broader research in this area.

Predicting a lethal event

Heat waves are among the most deadly weather phenomena on Earth. A 2006 heat wave across much of the United States and Canada was blamed for more than 600 deaths in California alone, and a prolonged heat wave in Europe in 2003 may have killed more than 50,000 people.

To see if heat waves can be triggered by certain large-scale atmospheric circulation patterns, the scientists looked at data from relatively modern records dating back to 1948. They focused on summertime events in the United States in which daily temperatures reached the top 2.5 percent of weather readings for that date across roughly 10 percent or more of the contiguous United States. However, since such extremes are rare by definition, the researchers could identify only 17 events that met such criteria -- not enough to tease out a reliable signal amid the noise of other atmospheric behavior.

The group then turned to an idealized simulation of the atmosphere spanning 12,000 years. The simulation had been created a couple of years before with a version of the NCAR-based Community Earth System Model, which is funded by NSF and the Department of Energy.

By analyzing more than 5,900 U.S. heat waves simulated in the computer model, they determined that the heat waves tended to be preceded by a wavenumber-5 pattern. This pattern is not caused by particular oceanic conditions or heating of Earth's surface, but instead arises from naturally varying conditions of the atmosphere. It was associated with an atmospheric phenomenon known as a Rossby wave train that encircles the Northern Hemisphere along the jet stream.

During the 20 days leading up to a heat wave in the model results, the five ridges and five troughs that make up a wavenumber-5 pattern tended to propagate very slowly westward around the globe, moving against the flow of the jet stream itself. Eventually, a high-pressure ridge moved from the North Atlantic into the United States, shutting down rainfall and setting the stage for a heat wave to emerge.

When wavenumber-5 patterns in the model were more amplified, U.S. heat waves became more likely to form 15 days later. In some cases, the probability of a heat wave was more than quadruple what would be expected by chance.

In follow-up work, the research team turned again to actual U.S. heat waves since 1948. They recognized that some historical heat wave events are indeed characterized by a large-scale circulation pattern that indicated a wavenumber-5 event.

Extending forecasts beyond 10 days

The research finding suggests that scientists are making progress on a key meteorological goal: forecasting the likelihood of extreme events more than 10 days in advance. At present, there is very limited skill in such long-term forecasts.

Previous research on extending weather forecasts has focused on conditions in the tropics. For example, scientists have found that El Niño and La Niña, the periodic warming and cooling of surface waters in the central and eastern tropical Pacific Ocean, are correlated with a higher probability of wet or dry conditions in different regions around the globe. In contrast, the wavenumber-5 pattern does not rely on conditions in the tropics. However, the study does not exclude the possibility that tropical rainfall could act to stimulate or strengthen the pattern.

Now that the new study has connected a planetary wave pattern to a particular type of extreme weather event, Teng and her colleagues will continue searching for other circulation patterns that may presage extreme weather events.

"There may be sources of predictability that we are not yet aware of," she says. "This brings us hope that the likelihood of extreme weather events that are damaging to society can be predicted further in advance."



INFORMATION:

The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under sponsorship by the National Science Foundation. Any opinions, findings and conclusions, or recommendations expressed in this release are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

About the article

Title: Probability of U.S. heat waves affected by subseasonal planetary wave pattern

Authors: Haiyan Teng, Grant Branstator, Hailan Wang, Gerald A. Meehl, and Warren M. Washington

Publication: Nature Geoscience

On the Web

For news releases, images, and more: http://www.ucar.edu/atmosnews

Additional Contact:

Zhenya Gallon, NCAR/UCAR Media Relations
303-497-8607
zhenya@ucar.edu



ELSE PRESS RELEASES FROM THIS DATE:

Radioactive waste: Where to put it?

2013-10-28
Radioactive waste: Where to put it? 2013 GSA Annual Meeting Boulder, CO, USA — As the U.S. makes new plans for disposing of spent nuclear fuel and other high-level radioactive waste deep underground, geologists are key to identifying safe burial sites and techniques. ...

Mount Sinai researchers identify mechanisms and potential biomarkers of tumor cell dormancy

2013-10-28
Mount Sinai researchers identify mechanisms and potential biomarkers of tumor cell dormancy May be able to recreate conditions that keep cancer cells from growing after they have spread Oncologists have long puzzled over ...

Cell nucleus protein in brown fat cells governs daily control of body temperature

2013-10-28
Cell nucleus protein in brown fat cells governs daily control of body temperature Biorhythm of brown fat has implications for combating obesity, associated diabetes and heart disease, finds an interdisciplinary team from Penn Medicine PHILADELPHIA ...

International group finds 11 new Alzheimer's genes to target for drug discovery

2013-10-28
International group finds 11 new Alzheimer's genes to target for drug discovery Global collaboration including Penn Medicine experts yields fresh look at role of immune system in Alzheimer's PHILADELPHIA - The largest international Alzheimer's ...

Brief exposure to performance-enhancing drugs may be permanently 'remembered' by muscles

2013-10-28
Brief exposure to performance-enhancing drugs may be permanently 'remembered' by muscles Brief exposure to anabolic steroids may have long lasting, possibly permanent, performance-enhancing effects, shows a study published today [28 October] in The Journal of Physiology. Previously, ...

Smart neurons: Single neuronal dendrites can perform computations

2013-10-28
Smart neurons: Single neuronal dendrites can perform computations When you look at the hands of a clock or the streets on a map, your brain is effortlessly performing computations that tell you about the orientation of these objects. New research by UCL scientists ...

New material for quantum computing discovered out of the blue

2013-10-28
New material for quantum computing discovered out of the blue A common blue pigment used in the £5 note could have an important role to play in the development of a quantum computer, according to a paper published today in the journal Nature. The pigment, ...

11 new genetic susceptibility factors for AD discovered through the largest study

2013-10-28
11 new genetic susceptibility factors for AD discovered through the largest study Findings a major breakthrough in the understanding of Alzheimer's disease (Boston)-- The largest international study ever conducted on Alzheimer's disease (AD), the I-GAP ...

NIH-supported study identifies 11 new Alzheimer's disease risk genes

2013-10-28
NIH-supported study identifies 11 new Alzheimer's disease risk genes International groups join forces to find elusive gene variants in largest-ever sample set An international group of researchers has identified 11 new genes that offer important new insights ...

UNC neuroscientists discover new 'mini-neural computer' in the brain

2013-10-28
UNC neuroscientists discover new 'mini-neural computer' in the brain CHAPEL HILL, N.C. – Dendrites, the branch-like projections of neurons, were once thought to be passive wiring in the brain. But now researchers at the University ...

LAST 30 PRESS RELEASES:

Dancing alleviated perceived symptoms of depression and helped to understand its root causes

Tricky treats: Why pumpkins accumulate pollutants

Revealing the molecular structures of sugars using galectin-10 protein crystals

World’s leading medical journal details the climate emergency

GLP-1 drugs effective for weight loss, but more independent studies needed

Researchers uncover previously unexplored details of mosquito’s specialized detection mechanisms

Stem cell therapy linked to lower risk of heart failure after a heart attack

The NHS is reaching a crisis point in consultant recruitment, new report warns

UNM research suggests Halloween fireballs could signal increased risk of cosmic impact or airburst in 2032 and 2036

Biochar’s hidden helper: Dissolved organic matter boosts lead removal from polluted water

Sunlight turns everyday fabrics into ocean microfibers, new study finds

Antibiotics linked to lower risk of complications after obstetric tear

Rapid blood pressure fluctuations linked to early signs of brain degeneration in older adults

How microbes control mammalian cell growth

Emergency department pilot program serves rural families

Amid renewable-energy boom, study explores options for electricity market

Study finds improvement in knee pain with exercise and physical therapy

Researchers uncover key mechanism behind chemotherapy-induced nerve damage

Mayo Clinic researchers find enhancing the body’s ‘first responder’ cells may boost immune therapy for cancer

Secret to a long life? In bowhead whales, a protein repairs damaged DNA

MIT study: Identifying kids who need help learning to read isn’t as easy as A, B, C

Plant biomass substance helps combat weeds

Veterans with epilepsy after traumatic brain injury may have higher mortality rates

Who is more likely to lose vision due to high brain pressure?

Scripps Research professor awarded $3.2 million to advance type 1 diabetes research

Anna Wuttig wins Bayer Foundation Early Excellence in Science Award

Electric vehicles outperform gasoline cars in lifetime environmental impact

Kilimanjaro has lost 75 percent of its natural plant species over the last century

Spider web “decorations” may help pinpoint location of captured prey

Ancient tombs reveal the story of Chinese history

[Press-News.org] Scientists eye longer-term forecasts of US heat waves