Scientists Probe Indian Ocean for Clues to Worldwide Weather Patterns

An international team of researchers will begin gathering in the Indian Ocean next month to study how tropical weather brews there and then moves eastward along the equator with reverberating effects around the entire globe. They will use a vast array of tools ranging from aircraft and ships to moorings, radars, and numerical models.

The six-month field campaign, known as DYNAMO (Dynamics of the Madden-Julian Oscillation), will help improve long-range weather forecasts and seasonal outlooks, and enable scientists to further refine computer models of global climate.

The National Center for Atmospheric Research (NCAR) is providing major observing tools to the science team and helping to oversee operations and data management for the project. DYNAMO is organized internationally as the Cooperative Indian Ocean Experiment on Intraseasonal Variability in the Year 2011 (CINDY2011), which is led by the Japan Agency for Marine-Earth Science and Technology.

The overriding goal of the DYNAMO field campaign is to better understand a disturbance of the tropics known as the Madden-Julian Oscillation, or MJO. This disturbance, which originates in the equatorial Indian Ocean roughly every 30 to 90 days, is part of the Asian and Australian monsoons. It can enhance hurricane activity in the northeast Pacific and Gulf of Mexico, trigger torrential rainfall along the west coast of North America, and affect the onset of El Niño, along with other impacts on weather and climate patterns around the globe.

Scientists believe that the MJO is the world’s greatest source of atmospheric variability in the one- to three-month time frame.

“The Madden-Julian Oscillation has a huge impact all over the globe,” says DYNAMO chief scientist Chidong Zhang of the University of Miami. “It connects weather and climate, and it is important to forecasting both of them.”

“The MJO drives weather in both hemispheres even though it sits along the equator,” says NCAR’s Jim Moore, director of the DYNAMO project office. “Its origins have never been measured in such a systematic fashion before.”

DYNAMO, the Littoral Air-Sea Processes (LASP), and the ARM MJO Investigation Experiment (AMIE) are the three U.S. projects contributing to CINDY 2011. DYNAMO, LASP, and AMIE are jointly supported by several United States agencies including the National Science Foundation (NSF), Department of Energy (DOE), Office of Naval Research (ONR), National Oceanic and Atmospheric Administration (NOAA), and NASA.

Staff, facilities, and observations for the international collaborative effort are being provided by 16 countries: Australia, China, France, India, Indonesia, Japan, Kenya, Korea, the Maldives, Papua New Guinea, Seychelles, Singapore, Sri Lanka, Taiwan, the United Kingdom, and the United States. U.S. scientists, students, engineers, and staff from 16 universities and 11 national laboratories and centers are participating in the field campaign.

The project “super site” on Addu Atoll in the Maldives will host the major radar array. Other observation sites will be based on Manus Island in Papua New Guinea and on Diego Garcia atoll, as well as aboard research ships and aircraft in the Indian Ocean. The AMIE project provides continuous observations on Addu Atoll and Manus for the six-month period.

“The entire international program encompasses a vast expanse of the Indian Ocean on both sides of the equator and into the equatorial western Pacific, providing scientists a chance to measure the pulse of the whole life cycle of the MJO,” says AMIE principal investigator Chuck Long of the Pacific Northwest National Laboratory.

The MJO plays a key role in driving tropical weather and climate variations during all seasons of the year. It also interacts with other atmospheric patterns, such as the El Niño/Southern Oscillation and the North Atlantic Oscillation that can shape weather and climate patterns across much of the globe.

Scientists need to better understand the MJO, both to improve long-range weather forecasts and seasonal outlooks worldwide and perhaps make the leap to longer-term forecasts of climate that may extend years into the future.

In winter, for example, the onset of an MJO can set off atmospheric waves that travel across the globe and, about 10 days later, influence the location and severity of major storms on the west coast of North America, some of which cause significant flooding.

“If you can find out how an MJO event starts, you may get a couple of weeks warning about wintertime storms in the United States, “ says NCAR scientist Mitchell Moncrieff, a member of the DYNAMO Science Steering Committee.

At present, the computer models that scientists use to study global weather and climate fail to capture the MJO very well. The information from the field campaign could lead to significant improvements to the models.

As global climate changes, it is becoming more important to understand how the atmosphere and oceans interact to regulate Earth’s temperature and respond to long-term variation. Field projects such as DYNAMO and AMIE, with an emphasis on basic research, add to scientists’ growing body of knowledge about the many interconnected components of Earth’s complex climate system.

“The long-term applications and implications of the data that come from this international field campaign could be profound in terms of our understanding of weather, climate and climate change,” NCAR’s Moore says.

“It’s our first chance to do a large, in-depth field campaign in the Indian Ocean," says Eric DeWeaver, program director in NSF’s Division of Atmospheric and Geospace Sciences "This is a rare occasion when many countries pool their scientific resources to look at a phenomenon that's of tremendous interest to everyone. The precipitation pattern over the Indian Ocean can influence weather and climate as far away as the USA, including the number of hurricanes that form in the Gulf of Mexico."

The DYNAMO field campaign brings a considerable array of instruments to bear on the MJO, including two research aircraft provided by NOAA and the French Airborne Environment Research Service; four ships from the United States, India, Indonesia and Japan; a half-dozen meteorological radars; balloon sounding units; moored buoys; and a suite of other instruments.

Especially critical during the field campaign are radars, which provide information about the microphysics inside clouds and rainstorms that lead to the development of the MJO. At the project super site on Addu Atoll, a meteorological radar array with seven different frequencies will be used to scan the MJO as it moves through the region. The array includes NCAR’s S-PolKa, a dual-wavelength Doppler radar that can distinguish the sizes and shapes of precipitation particles and even observe the water vapor from which the clouds form, thereby shedding light on the development of clouds and rainfall. It also includes a C-band radar from Texas A&M University that can estimate rainfall and latent heating. In addition, the site includes a suite of radars in a mobile facility of AMIE that detect different types of clouds.

“DYNAMO and AMIE mark the first time in the modern era that we’ll be able to use remote sensing techniques, particularly radar, to measure atmospheric phenomena from individual cloud droplets to large raindrops,” Moore says. “We have instrument capabilities for this project that we didn’t even have 10 or 15 years ago.”

In addition to measuring the sky, the researchers will turn their attention to the sea. The physical properties of the ocean, such as temperature and salinity, are as important to the MJO as are the properties of the atmosphere. A collection of ocean sensors, deployed from ships and moorings in the open seas, will collect data on ocean-atmosphere interactions. The atmospheric and ocean data will be fed into computer models to study the initiation and propagation of the MJO.

About 50 scientists and technicians from NCAR are involved in DYNAMO. In addition to deploying the S-PolKa radar, NCAR is supporting the project by providing sounding systems that measure standard weather variables, hosting the project’s logistics and planning office, and handling data management, which includes creating a real-time, online field catalog and long-term data archive.

The U.S. researchers are collaborating heavily with their Maldivian hosts. The Maldives Meteorological Service is providing local weather knowledge, meeting and operations space and facilities. The researchers in turn will offer training on radar and other instrumentation to local meteorologists.

A DYNAMO and AMIE media day and opening ceremony will take place on Addu Atoll at the beginning of the field campaign. Other outreach activities with local schools and organizations will be incorporated into the project during the entire deployment period.

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 publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.