Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study Predicts Lag in Summer Rains Over Parts of U.S. and Mexico

12.03.2013
Delay Could Affect Agriculture, Livestock, Desert Ecosystems
A delay in the summer monsoon rains that fall over the southwestern United States and northwestern Mexico is expected in the coming decades according to a new study in the Journal of Geophysical Research. The North American monsoon delivers as much as 70 percent of the region's annual rainfall, watering crops and rangelands for an estimated 20 million people.

"We hope this information can be used with other studies to build realistic expectations for water resource availability in the future," said study lead author, Benjamin Cook, a climate scientist with joint appointments at Columbia University's Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies.

Much of the arid U.S. Southwest is expected to get even drier as winter precipitation declines under climate change, but the present modeling study predicts that summer rain levels will stay constant over southern Arizona and New Mexico, and northwestern Mexico. What will shift is the arrival of the heaviest rains, from July and August or so, to September and October, the study says. "There still will be a healthy monsoon which is good news for agriculture in the southern U.S. and northwestern Mexico-the timing is the problem here," said study co-author Richard Seager, a climate scientist at Lamont-Doherty.

A delayed monsoon could potentially lower crop yields as rains come later in the growing season, when the days are getting shorter. By prolonging hot and dry conditions during spring, a late monsoon could also trigger more wildfires and force cities to stretch diminished water supplies. The study makes use of the latest climate change models (those used by the Intergovernmental Panel on Climate Change in its Fifth Assessment Report due out next fall), to estimate monthly changes in precipitation by the end of the century, 2080-2099. The researchers hypothesize that future warming will make it more difficult to form clouds and rainfall early in the monsoon when soils are dry, followed reduced winter rain and snowfall, thus delaying the onset of the monsoon rains until enough moisture can be moved in from the oceans.

There is some evidence that the monsoon may already be arriving later. A 2007 study in the Journal of Climate led by researcher Katrina Grantz, then at the University of Colorado found a decline in July rainfall since the late 1940s, and a corresponding increase in August to September rainfall. Other scientists are cautious about drawing conclusions from a relatively short instrumental record, given the monsoon's natural year-to-year variability. The second-latest monsoon onset was recorded in 2005, but for three years after, the monsoon came earlier than average or on schedule, said Chris Castro, a monsoon researcher at the University of Arizona who was not involved in the study.
The Sonoran Desert and Sky Islands ecoregion lies at the northern edge of the North American monsoon, where vegetation ranges from saguaro-studded subtropical desert in the lowlands to high-altitude boreal forests. It is unclear how plants finely attuned to the monsoon’s arrival will cope with the longer wait. “Will their growth slowdown or will some species grow dormant?” said Jeremy Weiss, a geosciences researcher at the University of Arizona who was not involved in the study.

A delay is bound to have economic impact, whether in northwestern Mexico or Arizona where agriculture and rangelands respectively are mostly rain-fed. The late monsoon in 2005 hindered summer grass development to the point that U.S. ranchers had to buy supplemental feed for their cattle, Andrea Ray, a researcher at the National Oceanic and Atmospheric Administration, noted in a 2007 study in the Journal of Climate.

Though total monsoon rainfall is projected to stay the same, warmer summer temperatures under climate change will cause more evaporation, leaving less water for crops, reservoirs and ecosystems. "It is important to look at the big picture before getting too sanguine about monsoon rainfall staying steady," said Jonathan Overpeck, a climate scientist at the University of Arizona who was not involved in the study. "Farmers who rely on summer rain will have a trickier time as the rainfall timing and amounts changes-they like predictability. Ultimately, the jury is still out, but this is a fine study that gives us more information to plan with."

More:

Richard Seager explains the study: Global Decadal Hydroclimate Predictability, Variability and Change: A Data-Enriched Modeling Study (GloDecH)

National Science Foundation video: North American Monsoon System.

Kim Martineau | EurekAlert!
Further information:
http://www.ldeo.columbia.edu

More articles from Earth Sciences:

nachricht Global study of world's beaches shows threat to protected areas
19.07.2018 | NASA/Goddard Space Flight Center

nachricht NSF-supported researchers to present new results on hurricanes and other extreme events
19.07.2018 | National Science Foundation

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>